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ENERGY EFFICIENCY AS A RESOURCE Energy efficiency (EE) is as real a resource as the purchased energy or raw materials. But being hidden within the facility, it has to be uncovered by energy professionals whose job is akin to that of detectives. Their insights, skills and equipment relating to energy management constitute their core competence. Keeping abreast with the latest technologies in the field of functional domain (business operation or process) enriches their competence in that particular domain.

Sunday, 2 November 2014

Energy Sources

 Energy Sources

    • Biofuels
    • Coal
    • Electricity
    • Geothermal
    • Hydrogen
    • Hydropower
    • Petroleum – Oil and Natural Gas
    • Solar Energy
    • Uranium – Nuclear Energy
    • Wind Energy

Energy is essential. It is embodied in everything we use. To compare sources of energy effectively, we need to understand what it is and how it works.

What is Energy?

It comes from many sources and in many forms. The forms of energy are classified in two general categories: potential and kinetic.
Potential energy is energy stored in an object. Chemical, mechanical, nuclear, gravitational, and electrical are all stored energy. Kinetic energy does the work. Light, heat, motion, and sound are examples of kinetic energy.
Here’s a simple example. Stretching a rubber band gives it the potential to fly. The tension created from the stretching is potential mechanical energy. When the rubber band is released, it flies through the air using motion (kinetic energy). The process of changing energy from one form into another is called energy transformation. The rubber band is transformed from potential energy into kinetic energy.
Systems convert energy at various rates of efficiency. Water turbines, for example, are very efficient, while combustion engines are not. Engineers and physicists constantly work to develop systems with high energy-conversion efficiency.

Which Energy Source is Best?

It depends. Many alternative sources of energy are still being researched and tested. Technologies are continually being developed and enhanced to improve energy sources. Not all energies are ready for mass consumption, so you have to ask the right questions to find out which energy source does the job.
  • Is it a renewable or nonrenewable source?
  • What are the capital and setup costs?
  • What are the ongoing operating costs?
  • What size of energy storage is required?
  • How efficient is it to produce one unit of energy?
  • Can it be produced on a large scale?
  • What is the cost to the consumer?
  • What impact will it have on the environment?
Energy is lost to the environment during any energy transformation, usually as heat. Notice the heat from your computer or car after it has been in use for a while. Nothing is completely energy efficient.

What are the Sources of Energy?

Primary energy sources (meaning energy is created directly from the actual resource) can be classified in two groups: nonrenewable or renewable. Secondary sources are derived from primary sources.
Non-Renewable Energy Sources – Energy from the ground that has limited supplies, either in the form of gas, liquid or solid, are called nonrenewable resources. They cannot be replenished, or made again, in a short period of time. Examples include: oil (petroleum), natural gas, coal and uranium (nuclear). Oil, natural gas and coal are called “fossil fuels” because they have been formed from the organic remains of prehistoric plants and animals.
Renewable Energy Sources – Energy that comes from a source that’s constantly renewed, such as the sun and wind, can be replenished naturally in a short period of time. Because of this we do not have to worry about them running out. Examples include: solar, wind, biomass and hydropower. Currently, about 20% of the world’s electricity comes from renewable resources. There is a global debate as to whether geothermal energy is renewable or nonrenewable.
Secondary Energy Sources –  Energy that is converted from primary sources are secondary sources of energy. Secondary sources of energy are used to store, move, and deliver energy in an easily usable form. Examples include electricity and hydrogen.

Saturday, 18 October 2014

Certified New Homes

Certified New Homes
ENERGY STAR Certified HouseBuying a new home is one of the biggest purchases you'll ever make. By choosing one that has earned the government's trusted ENERGY STAR label, you can have the house of your dreams and enjoy peace of mind knowing it's been built to meet strict energy efficiency guidelines set by the U.S. Environmental Protection Agency (EPA). Find builders who are committed to the next generation of ENERGY STAR certified homes.
With ENERGY STAR, you know you're making the right decision—for your wallet, for your family, and for the environment—bringing these important benefits:

Lower Utility Bills

By using less energy for heating, cooling, and water heating, ENERGY STAR certified homes deliver approximately 20% savings on annual utility bills. Over the 7 to 8 years that a typical family lives in a home, you can save thousands of dollars in maintenance cost.

Enhanced Performance

In ENERGY STAR certified homes, comfort is ensured with consistent temperatures between and across rooms; indoor air quality is enhanced by reducing dust, pollen, bugs, and excessive humidity; and durability is improved with comprehensive water protection, windows that block damaging sunlight, and better grade equipment.

Environmental Protection

The energy used in our homes often comes from the burning of fossil fuels at power plants. So, by using less energy to operate, ENERGY STAR certified homes help to prevent air pollution—an added benefit for today's environmentally-conscious consumer looking for "green" choices.
Learn about Complete Thermal Enclosure System >

Weatherization

Weatherization (American English) or weatherproofing (British English) is the practice of protecting a building and its interior from the elements, particularly from sunlight, precipitation, and wind, and of modifying a building to reduce energy consumption and optimize energy efficiency. Weatherization is distinct from building insulation, although building insulation requires weatherization for proper functioning. Many types of insulation can be thought of as weatherization, because they block drafts or protect from cold winds. Whereas insulation primarily reduces conductive heat flow, weatherization primarily reduces convective heat flow. In the United States, buildings use one third of all energy consumed and two thirds of all electricity. Due to the high energy usage, they are a major source of the pollution that causes urban air quality problems and pollutants that contribute to climate change. Building energy usage accounts for 49 percent of sulfur dioxide emissions, 25 percent of nitrous oxide emissions, and 10 percent of particulate emissions.[1] Weatherization procedures Typical weatherization procedures include: Sealing bypasses (cracks, gaps, holes), especially around doors, windows, pipes and wiring that penetrate the ceiling and floor, and other areas with high potential for heat loss, using caulk, foam sealant, weather-stripping, window film, door sweeps, electrical receptacle gaskets, and so on to reduce infiltration.[2] Sealing recessed lighting fixtures ('can lights' or 'high-hats'), which leak large amounts of air into unconditioned attic space. Sealing air ducts, which can account for 20% of heat loss, using fiber-reinforced mastic (not duck/duct tape, which is not suitable for this purpose) Installing/replacing dampers in exhaust ducts, to prevent outside air from entering the house when the exhaust fan or clothes dryer is not in use. Protecting pipes from corrosion and freezing. Installing footing drains, foundation waterproofing membranes, interior perimeter drains, sump pump, gutters, downspout extensions, downward-sloping grading, French drains, swales, and other techniques to protect a building from both surface water and ground water. Providing proper ventilation to unconditioned spaces to protect a building from the effects of condensation. See Ventilation issues in houses Installing roofing, building wrap, siding, flashing, skylights or solar tubes and making sure they are in good condition on an existing building. Installing insulation in walls, floors, and ceilings, around ducts and pipes, around water heaters, and near the foundation and sill. Installing storm doors and storm windows. Replacing old drafty doors with tightly sealing, foam-core doors. Retrofitting older windows with a stop or parting bead across the sill where it meets the sash.[3] Replacing older windows with low-energy, double-glazed windows. The phrase "whole-house weatherization" extends the traditional definition of weatherization to include installation of modern, energy-saving heating and cooling equipment, or repair of old, inefficient equipment (furnaces, boilers, water heaters, programmable thermostats, air conditioners, and so on). The "Whole-House" approach also looks at how the house performs as a system.[4] Air Quality Weatherization generally does not cause indoor air problems by adding new pollutants to the air. (There are a few exceptions, such as caulking, that can sometimes emit pollutants.) However, measures such as installing storm windows, weather stripping, caulking, and blown-in wall insulation can reduce the amount of outdoor air infiltrating into a home. Consequently, after weatherization, concentrations of indoor air pollutants from sources inside the home can increase.[5] Weatherization can have a negative impact on indoor air quality, especially among occupants with respiratory illnesses.[5] This occurs because of a decrease in air exchange in the home, and resulting increase in moisture. This leads to higher concentrations of pollutants in the air. US Weatherization Assistance Program Weatherization has become increasingly high-profile as the cost of home heating has risen. The US Weatherization Assistance Program (WAP) was created in 1976 to help low-income families reduce energy consumption and costs. WAP reaches across all fifty states, the District of Columbia, and Native American tribes. The goal of WAP is to assist low-income families by reducing energy bills and decrease dependency on foreign oil by decreasing energy use. The US Department of Energy estimates that over 6.2 million homes have been weatherized, saving 30.5 MBtu of energy per household each year. It estimates weatherization returns $2.69 for each dollar spent on the program, realized in energy and non-energy benefits. Families whose homes are weatherized are expected to save $358 on their first year's utility bills.[6] Many state LIHEAP (Low Income Home Energy Assistance) programs work side by side with WAP to provide both immediate and long term solutions to energy poverty.

Home Energy Saver

Home Energy Saver is a set of on–line resources developed by the U.S. Department of Energy at the Lawrence Berkeley National Laboratory intended to help consumers and professional energy analysts, analyze, reduce, and manage home energy use.[1]

The Home Energy Saver energy assessment tool allows consumers to conduct a do-it-yourself home energy audit and provides specific recommendations to help lower household energy consumption and utility costs. By entering a zip code, users get estimates for typical and efficient homes in their area.[2] The estimates break down energy consumption by “end use". End uses reported by Home Energy Saver include: heating, cooling, water heating, major appliances, small appliances, and lighting.

The more details a user enters, (e.g., insulation levels, roofing, age of major equipment, how systems are used) the more customized the assessment results and energy efficiency recommendations become. The tailored reports allows consumers to drill into estimated cost of improvements, anticipated payback time, projected utility bill savings, and how much energy use and green house gas production will be reduced. Consumers can vary the energy efficiency assumptions and the upgrade costs, (e.g., replacing the default values with actual estimates from contractors) and recalculate the payback times and other details.

The Home Energy Saver website includes a section called LEARN which offers tips about energy savings, an explanation of the house-as-system energy efficiency approach, and other information to help people understand how energy is used in a home.

When launched in 1994, Home Energy Saver was the first and only online home energy calculator. Thereafter, 6 million people have used it to analyze their home energy use. Nearly 1 million people visit the site each year. In 2009, a second version of the tool, Home Energy Saver Professional, was launched. This advanced version provides a low cost, interactive energy simulation/assessments tool for contractors, building professionals, weatherization professionals, and building designers.

The Home Energy Simulation Model

The Home Energy Saver is built on DOE-2, a computer program for building heating and cooling energy analysis and design.[3] DOE-2 performs a thermal load simulation that accounts for heating and cooling equipment and thermal distribution efficiencies, infiltration, and thermostat management. User-entered zip codes are mapped to one of about 300 unique “weather tapes” that impose a year’s worth of local weather conditions on the home to determine heating and cooling needs.

Home Energy Saver extends DOE-2 in a number of ways to improve the simulation model. For example, when users enter their actual electricity tariffs, the predictive power of the model improves. Other methods are used to calculate the energy used by appliances, water heating, and lighting.

The public–domain HES calculation methods and underlying data are clearly documented on the website. Other web-based tool developers are welcome to use this information at no cost, providing that the source is properly credited.
Energy Saving Recommendations

The Home Energy Saver enables users to quantify the benefits of improving the energy efficiency and comfort of homes in the following ways:[4]

    No Cost Changes – No cost changes are modifications to the way energy is used, like lowering the hot water heater temperature, unplugging the second refrigerator that is running to cool just a few things, doing laundry with cool or cold water instead of hot, or programming the thermostat a bit lower. These changes don’t cost anything, but they can save a substantial amount of energy over time.
    Low Cost Changes – Low cost changes include actions like changing out incandescent light bulbs for compact fluorescent lamps (CFLs) or LED bulbs, wrapping a hot water heater in an insulating blanket, or weatherizing a home by caulking or adding weather stripping. Low cost changes are typically Do-It-Yourself tasks that can improve the energy efficiency of a home dramatically.
    Deep Home Energy Upgrades or Retrofits – Upgrades can include actions ranging from replacing old inefficient appliances with new Energy Star appliances, adding insulation, or replacing major systems like heating equipment or the roof.

The energy improvement recommendations are drawn from the National Residential Energy Efficiency Measures Database.
Awards & Recognition

Each year, the R&D 100 Awards recognize the year’s 100 most significant, innovative, newly introduced research and development advances. The awards are recognized in industry, government, and academia as proof that a product is one of the most innovative ideas of the year, nationally and internationally. Home Energy Saver and Hohm received an R&D 100 Award in 2010.[5]

Home Energy Saver received the U.S. Department of Energy's "Energy 100" award as one of the best 100 scientific and technological accomplishments over DOE's 23-year lifetime.[6] The discoveries were chosen based on their impact in saving consumers money and improving quality of life.

PC Magazine recognized Home Energy Saver in 2004 as one of the “Top 100 Undiscovered Websites.[7]

MSN-Money rates Home Energy Saver among the “Best Sites for Free Government Help” including it in the list of “The 100 most Useful Sites on the Internet.[8]

Energy Solutions

EnergySolutions, headquartered in Salt Lake City, Utah, is one of the world’s largest processors of low level waste (LLW), and is the largest nuclear waste company in the United States[citation needed]. It was founded by Steve Creamer in 2007 through the merger of four waste disposal companies : Envirocare, Scientech D&D, BNG America, and Duratek.

EnergySolutions has operations in over 40 states; and owns and operates a licensed landfill to dispose of radioactive waste approximately 60 miles west of Salt Lake City, UT in Tooele County, Utah. It also operates another disposal site in Barnwell County, South Carolina. The company possesses technology to convert waste into alternative material such as durable glass, and is contracted by the United States Department of Energy to assist in waste conversion efforts. The company holds the naming rights to EnergySolutions Arena.

On June 7, 2007, the company took over operational and management responsibilities of several Magnox atomic plants from British Nuclear Fuels plc in United Kingdom through the acquisition of the BNFL subsidiary - Reactor Sites Management Company (RMSC).[1][2]

Creation of EnergySolutions

Envirocare of Utah purchased the Connecticut-based Scientech D&D division in October 2005.[3] On February 2, 2006, Envirocare announced the $90 million purchase of BNG America a subsidiary of British Nuclear Fuels (BNFL) based in Virginia.[4] The merged company would change its name to EnergySolutions, with corporate headquarters based in Salt Lake City, Utah. On February 7, 2006, EnergySolutions announced it would buy Maryland-based Duratek, a publicly traded company, for $396 million in an all-cash deal.[5] The leveraged buyout was financed by banks led by Citigroup, effectively taking the company private.

After the acquisitions, EnergySolutions has 2,500 employees in 40 states with an annual revenue of $280 million.[6] Additionally, EnergySolutions owns two of the nation's three commercial low-level nuclear-waste repositories, although its primary competitor, Waste Control Specialists, hopes to build a fourth repository in Texas.
Envirocare

Envirocare (also called Envirocare of Utah, Inc.) was a company that disposed of Class A low level radioactive waste (LLRW) in an engineered landfill. It began operations in 1990 and was located in Clive, Utah.[7]

Envirocare was founded by Iranian immigrant Khosrow Semnani in 1988. Semnani served as president of the company until May 1997, when Envirocare's largest customer—the Department of Energy—requested that he step down in the wake of a bribery scandal.[8]

In mid-December 2004, Semnani sold Envirocare for an undisclosed sum. Steve Creamer became the company's new CEO. The deal was financed by private equity firms, led by Lindsay Goldberg & Bessemer of New York, Creamer Investments, and Peterson Partners both of Salt Lake City. Envirocare management promised to drop plans to bury hotter class B and C nuclear waste in Utah in deference to developing political opposition to the company, which was poised to ban the waste anyway.[9] Envirocare's management and ownership was retained as it made the acquisitions to become EnergySolutions.
Duratek

Based in Columbia, Maryland, Duratek was founded in 1983. In 1990, the company merged with General Technical Services (GTS); the resulting company was known as GTS Duratek.[10] That year, the company formed a joint venture with another firm — Chem-Nuclear Systems, Inc. — to build a commercial vitrification system.

In 1997, GTS Duratek acquired the Scientific Ecology Group (SEG). In 2000, the company purchased the nuclear services business arm of Waste Management Inc.[11] One year later, the company announced that it was dropping GTS from its name, and was once again known as Duratek.

Duratek was purchased by EnergySolutions at 25.7% premium over the February 7, 2006 stock price when the merger was announced.[5]
Energy Solutions

Since its inception, Energy Solutions has brought primarily domestic, Class A nuclear waste to Utah's west desert.

On June 7, 2007, the company announced the acquisition of the UK based BNFL subsidiary - Reactor Sites Management Company (RSMC).[1][2] The sale also included Magnox Electric Limited (MEL), a wholly owned subsidiary of RSMC, which holds the contracts and licences to operate ten nuclear reactor sites in the UK on behalf of the Nuclear Decommissioning Authority (NDA). Through the acquisition, the company took over operational and management responsibilities of several Magnox atomic plants from British Nuclear Fuels plc.

In 2009 it attempted to bring 20,000 tons of waste from Italy's shuttered nuclear power program through the ports of either Charleston, S.C., or New Orleans.[12] After processing in Tennessee, about 1,600 tons would be disposed of in Utah. The importation attempt was eventually abandoned.[13]

EnergySolutions has also sought at various times for the State of Utah’s permission to blend, or dilute, currently accepted Class A low-level radioactive waste with more radioactive Class B and Class C wastes until it just meets the Class A waste levels its license allows per container at its Clive disposal site.[14] Some estimate that this could increase Energy Solutions' Utah site current amount of 7,450 curies of radiation per annum (2010), to an additional 19,184 to 28,470 curies each year.[14] The Division of Radiation Control of Utah is currently considering this measure to allow Class B and Class C waste into Utah.[15] If allowed, this would make Utah, along with Texas, the only state in the nation to allow the importation of Class B and C radioactive wastes.[15]

Sunday, 12 October 2014

Energy, manufacturing to lead US President Barack Obama, PM Narendra Modi talks

US  President Barack Obama and new Indian Prime Minister Narendra Modi on Tuesday plan to discuss issues ranging from manufacturing to sanitation as the two leaders aim to deepen ties.
Obama and Modi were scheduled to meet at the White House at 10:55 a.m. (1455 GMT) during Modi's first visit to the United States since taking office in May, part of a larger effort aimed at expanding security partnerships and spurring foreign investment.
"When we meet today in Washington, we will discuss ways in which we can boost manufacturing and expand affordable renewable energy, while sustainably securing the future of our common environment," Obama and Modi said in a joint opinion piece published in The Washington Post on Tuesday.
"We will discuss ways in which our businesses, scientists and governments can partner as India works to improve the quality, reliability and availability of basic services, especially for the poorest of citizens. In this, the United States stands ready to assist," the two men wrote.
"An immediate area of concrete support is the 'Clean India' campaign, where we will leverage private and civil society innovation, expertise and technology to improve sanitation and hygiene throughout India."
The meeting comes on the heels of a joint "vision statement" issued after their first get-together at a White House dinner on Monday that laid out their plan to expand and deepen their countries' strategic partnership.
While efforts have been underway to build stronger ties between the United States and India, one of the world's most populous countries and a potential counterbalance to China in Asia, the partnership has yet to live up to expectations.
Modi has received a warm welcome in the United States, speaking at the UN General Assembly in New York and meeting with various US corporate chief executives. On Tuesday, he was scheduled to meet with other US leaders, including Secretary of State John Kerry and US House of Representatives Speaker John Boehner.
He also plans to visit a number of memorials in Washington devoted to former Indian independence leader Mahatma Gandhi, President Abraham Lincoln and civil rights leader Martin Luther King, Jr.
"We remain committed to the larger effort to integrate South Asia and connect it with markets and people in Central and Southeast Asia," Obama and Modi wrote in their op-ed.
They also reiterated a commitment to share intelligence and cooperate on security issues. They will also work on health issues that will help in tackling a range of crises from Ebola to malaria, they added.
(Reporting by David Brunnstrom and Susan Heavey; Editing by Jeffrey Benkoe)

Renewable is the way forward for India’s energy security: Narendra Modi

Renewable is the way forward for India’s energy security: Narendra ModiNeemuch, Madhya Pradesh: Spelling out his energy security plans for India’s development, Bharatiya Janata Party’s (BJP’s) prime ministerial candidate Narendra Modi blamed the central government for mismanagement of the country’s natural resources. “With the country having so much natural resources, India hasn’t progressed much in the 21st century,” Modi said on Wednesday at the inauguration of a solar power project in Neemuch. Articulating his strategy for the energy sector, Modi said India should harness coal, gas, hydropower, solar energy, bio-mass and nuclear and wind power to bring about an “energy revolution” in the country. India’s national action plan on climate change recommends that the country generate 10% of its power production from solar, wind, hydropower and other renewable sources by 2015, and 15% by 2020. India has an installed power generation capacity of 2,27,356.73 megawatt (MW), of which 12.4%, or 28,184.35MW, is renewable energy. Drawing comparisons between different regions of the country and the energy shortage, Modi said while there was darkness on one side, 20,000MW of capacity was lying idle on the other. “While there is a demand, there is no electricity,” the BJP’s prime ministerial aspirant said. Modi blamed the non-availability of sufficient coal and gas in the country as a reason behind power capacity lying idle. Gas-fuelled power projects with an aggregate capacity of 8,000MW that are close to commissioning and another 1,500MW that have been already commissioned have been stranded in the absence of gas. In addition, another 18,000MW capacity is operating at a plant load factor (PLF) of 20%. PLF is a measure of average capacity utilization. The power projects require 102.61 million standard cubic metres per day (mscmd) of gas. “If we want to industrialize, electricity is the first necessity,” said Modi. Modi also presented a picture of energy resources across the country. “With eastern part of the country rich in water resources, it is a heaven for hydro power generation; also our coasts are fit for wind energy. Similarly our plains such as Gujarat and Rajasthan are fit for solar energy generation. If the planners had thought of these factors and formed a policy India wouldn’t be so dependent on energy imports,” Modi said. India’s energy demand is expected to more than double by 2035, from less than 700 million tonnes of oil equivalent (mtoe) today, to around 1,500 mtoe, according to the oil ministry’s estimate India, which is highly dependent on imports to meet its energy demand, has an energy import bill of $150 billion. This is expected to reach $300 billion by 2030, requiring a $3.6 trillion payout by 2030. Modi, who has been blamed for avoiding specifics of his development agenda, said India’s current account deficit (CAD) has increased because of coal imports. India plans to restrict its CAD to $50 billion in the year ending 31 March, finance minister P. Chidambaram had earlier said. For the last fiscal, CAD was at $88 billion with total imports worth $491 billion and oil imports ballooning to $164 billion. “The CAD became a problem because coal imports increased. We have coal, we have the resources, but the central government doesn’t have the proper policies to harness it. If India needs to become sufficient we will have to become energy independent. Electricity is an important factor,” Modi added. India is the world’s fourth-largest energy consuming nation and imports 80% of its crude oil and 18% of its natural gas requirements. The country trails the US, China and Russia, accounting for 4.4% of global energy consumption. Modi also talked about environment versus development debate, and said, “If we don’t protect environment then development will be in danger. Environment friendly development desires non-renewable form of energy generation,” he added. The writer is in Neemuch as a guest of Welspun Energy Ltd. Gyan Verma in New Delhi contributed to this story.
 Read more at: http://www.livemint.com/Politics/7EkcrE6zgNmZJSlta0exlK/Renewable-is-the-way-forward-for-Indias-energy-security-Na.html?utm_source=copy

Shri Narendra Modi on "Unleashing India's Energy and Drive"

Unleashing India's Energy and Drive
With 800 million people under age 35, we are a nation ready for rapid, responsible economic development.
By
Shri Narendra Modi
Prime Minister of India
Sept. 25, 2014 7:25 p.m. ET
There is a high tide of hope for c­hange in India. This May, across India's immense diversity, 1.25 billion people spoke unequivocally for political stability, good governance and rapid development. India has a government with a majority in the Lok Sabha, our lower house of parliament, for the first time in 30 years. A young nation with 800 million people under age 35, India is brimming with optimism and confidence. The young people's energy, enthusiasm and enterprise are India's greatest strength. Unleashing those attributes is my government's biggest mission.
We will pursue this mission by eliminating unnecessary laws and regulations, making bureaucratic processes easier and shorter, and ensuring that our government is more transparent, responsive and accountable. It has been said that doing the thing right is as important as doing the right thing.
Indian Space Research Organization (ISRO) scientists and engineers cheer after India's Mars orbiter successfully entered the red planet's orbit. Reuters
We will create world-class infrastructure that India badly needs to accelerate growth and meet people's basic needs. We will make our cities and towns habitable, sustainable and smart; and we will make our villages the new engines of economic transformation. "Make in India" is our commitment—and an invitation to all—to turn India into a new global manufacturing hub. We will do what it takes to make it a reality.
We ran our election campaign on the promise of inclusive development. To me, that means many things: skills education, and opportunity; safety, dignity and rights for those in every section of our society, especially women; a bank account for every Indian; affordable health care within everyone's reach; sanitation for all by 2019; a roof over every head by 2022; electricity for every household; and connectivity to every village. In addressing these daunting challenges, I draw confidence from countless extraordinary stories of ordinary Indians that I have seen through decades of travel across India.
I also strongly believe in the possibilities of technology and innovation to transform governance, empower people, provide affordable solutions for societal challenges and reach people in ways that were unimaginable not so long ago. The number of cell phones in India has gone up from about 40 million to more than 900 million in a decade; our country is already the second-largest market for smart phones, with sales growing ever faster. When I think of the growth in computing power and storage capacity and its miniaturization that the world has witnessed over the past two decades, I am confident that this can be replicated in renewable energy. With solar and wind power, thousands of Indian villages will be able to get access quickly to reliable, affordable and clean energy, without waiting for large, faraway conventional power plants to be built.
For this reason, India's journey to prosperity can be a more sustainable and environmentally sensitive one than the path followed by countries that came of age in earlier eras. This is a journey of our choice, rooted in our tradition that worships nature's bounties.
India will pursue its dreams in partnership with our international friends. History tells us that India's natural instinct is to be open to the world. India will be open and friendly—for business, ideas, research, innovations and travel. In the coming months, you will feel the difference even before you begin your travel to India.
The United States is our natural global partner. India and the U.S. embody the enduring and universal relevance of their shared values. The thriving Indian-American community in the U.S. is a metaphor for the potential of our partnership, and for the possibilities of an environment that nurtures enterprise and rewards hard work. Our strengths in information technology are especially important for leadership in the digital age. The partnership between our businesses takes place in the comfort and certainty of similar political systems and shared commitment to rule of law. In education, innovation, and science and technology, the U.S continues to inspire India.
India and the U.S. have a fundamental stake in each other's success—for the sake of our values and our many shared interests. That is also the imperative of our partnership. And it will be of great value in advancing peace, security and stability in the Asia and Pacific regions; in the unfinished and urgent task of combating terrorism and extremism; and in securing our seas, cyber space and outer space, all of which now have a profound influence on our daily lives.
The complementary strengths of India and the U.S. can be used for inclusive and broad-based global development to transform lives across the world. Because our countries' values and interests are aligned, though our circumstances are different, we are in a unique position to become a bridge to a more integrated and cooperative world. With sensitivity to each other's point of view and the confidence of our friendship, we can contribute to more concerted international efforts to meet the pressing global challenges of our times.
This is a moment of flux in the global order. I am confident in the destiny of our two nations, because democracy is the greatest source of renewal and, with the right conditions, offers the best opportunity for the human spirit to flourish.
Mr. Modi is prime minister of India.

Modi calls for an 'energy revolution'

In the heart of Ahirwal-dominated Haryana’s Mahendergarh district on Wednesday, BJP’s fire brand ambassador and Prime Minister Narendra Modi slammed Chief Minister Bhupinder Singh Hooda for using state machineries, especially the police force, to create hurdles between him and the people of the state. 
“I was pained when I heard that old-age people walked to the venue to listen to me without bothering about distance. The state police gave parking space far away from the rally venue to create obstacles. 
"I want to ask the state government and local police why did they not make arrangements for parking close by. They will not become successful in creating gap between me and the people of Haryana,” Modi said, while addressing a gathering of more than one lakh people. 
During his rally in Rohtak, Modi underlined the need for four-colour revolution - involving energy (saffron), crops (green), milk (white) and fishing sector (blue) - to help India move ahead.

Read more: http://www.dailymail.co.uk/indiahome/indianews/article-2785684/Modi-calls-energy-revolution-Haryana-help-India-ahead.html#ixzz3Fuch10a5

Tuesday, 30 September 2014

Energy development

Energy development[1][2][3] is a field of endeavor focused on making available sufficient primary energy sources[4] and secondary energy forms to meet the needs of society.[5][6][7][8][9] These endeavors encompass those which provide for the production of conventional, alternative and renewable sources of energy, and for the recovery and reuse of energy that would otherwise be wasted. Energy conservation[note 2] and efficiency measures[note 3] reduce the impact of energy development, and can have benefits to society with changes in economic cost and with changes in the environmental effects.

Contemporary industrial societies use primary and secondary energy sources for transportation and the production of many manufactured goods. Also, large industrial populations have various generation and delivery services for energy distribution and end-user utilization.[note 4] This energy is used by people who can afford the cost to live under various climatic conditions through the use of heating, ventilation, and/or air conditioning. Level of use of external energy sources differs across societies, along with the convenience, levels of traffic congestion, pollution sources[10] and availability of domestic energy sources.

Thousands of people in society are employed in the energy industry, of which subjectively influence and impact behaviors. The conventional industry comprises the petroleum industry[note 5] the gas industry,[note 6] the electrical power industry[note 7] the coal industry, and the nuclear power industry. New energy industries include the renewable energy industry, comprising alternative and sustainable manufacture, distribution, and sale of alternative fuels. While there is the development of new hydrocarbon sources,[11] including deepwater/horizontal drilling and fracking, are contentiously underway, commitments to mitigate climate change are driving efforts to develop sources of alternative and renewable energy.

Colloquially, and in non-scientific literature, the terms power,[note 8] fuels, and energy can be used as synonyms, but in the field of energy technology they possess different distinct meanings that are associated with them. An energy source is usually in the form of a closed system, the element that provides the energy by conversion from another energy form; However, the energy can be quantitative, the balance sheet is capable of containing open system energy transfers.[note 9] Illustrative of this can be the emanations from the sun, which with its nuclear fusion is the most important energy source for the Earth[note 10] and which provides its energy in the form of radiation.

The natural elements[note 11] of the material world exist in forms that can be converted into usable energy and are resources from which society can obtain energy to produce heat, light, and motion (among the many uses). According to their nature, the power plants can be classified into:

Primary : They are found in nature: wind, water, solar,[note 12] wood, coal, oil, nuclear.
Secondary : Are those obtained from primary energy sources: electricity, gas.
Classified according to the energy reserves of the energy source used and the regeneration capacity with:

renewable: When the energy source used is freely regenerated in a short period and there are practically limitless reserves; An example is the solar energy that is the source of energy from the sun, or the wind[note 13] used as an energy resource. Renewable energies are:
original solar
natural wind (atmospheric flows)
natural geothermal
oceanic tidal
natural waterfall (hydraulic flows)
natural plant: paper, wood
natural animal: wax, grease,[note 14] pack animals and sources of mechanical energy[note 15]
nonrenewable: They are coming from energy limited sources on Earth in quantity and, therefore, are exhaustible. The non-renewable energy sources include, non-exclusively:
fossil source: petroleum, natural gas, coal
original mineral/chemical: uranium, shale gas[note 16]
So, for example, shale gas is secondary non-renewable. Wind is a primary renewable.

The principle stated by Antoine Lavoisier on the conservation of matter applies to energy development:[note 17] "nothing is created." Thus any energy "production" is actually a recovery transformation of the forms of energy whose origin is that of the universe.

For example, a bicycle dynamo turns in part from the kinetic energy (speed energy) of the movement of the cyclist and converting it into electrical energy will transfer in particular to its lights producing light, that is to say light energy, via the heating of the filament of the bulb and therefore heat (thermal energy). But the kinetic energy of the rider is itself biochemical energy (the ATP muscle cells) derived from the chemical energy of sugars synthesized by plants who use light energy from the sun, which runs from the nuclear energy produced by fusion of atoms of hydrogen, the material itself constitute a form of energy, called "mass energy".

Fossil fuels[edit]

The Moss Landing Power Plant burns natural gas to produce electricity in California.

Natural gas drilling rig in Texas.
Main articles: Fossil fuel and Peak oil
Fossil fuel (primary non-renewable fossil) sources burn coal or hydrocarbon fuels, which are the remains of the decomposition of plants and animals. There are three main types of fossil fuels: coal, petroleum, and natural gas. Another fossil fuel, liquefied petroleum gas (LPG), is principally derived from the production of natural gas. Heat from burning fossil fuel is used either directly for space heating and process heating, or converted to mechanical energy for vehicles, industrial processes, or electrical power generation.

Fossil energy is from recovered fossils (like brown coal, hard coal, peat, natural gas and crude oil) and are originated in degradated products of dead plants and animals. These fossil fuels are based on the carbon cycle and thus allow stored (historic solar) energy to be recycled today. In 2005, 81% were of the world's energy needs met from fossil sources.[12] Biomass is also derived from wood and other organic wastes and modern remains. The technical development of fossil fuels in the 18th and 19th Century set the stage for the Industrial Revolution.

Fossil fuels make up the bulk of the world's current primary energy sources. The technology and infrastructure already exist for the use of fossil fuels. Petroleum energy density in terms of volume (cubic space) and mass (weight) ranks currently above that of alternative energy sources (or energy storage devices, like a battery). Fossil fuels are currently economical, and suitable for decentralized energy use.

Dependence on fossil fuels from regions or countries creates energy security risks for dependent countries.[13][14][15][16][17] Oil dependence in particular has led to war,[18] funding of radicals,[19] monopolization,[20] and socio-political instability.[21] Fossil fuels are non-renewable, un-sustainable resources, which will eventually decline in production[22] and become exhausted, with consequences to societies that remain dependent on them. Fossil fuels are actually slowly forming continuously, but are being consumed quicker than are formed.[note 18] Extracting fuels becomes increasingly extreme as society consumes the most accessible fuel deposits. Extraction in fuel mines get intensive and oil rigs drill deeper (going further out to sea).[23] Extraction of fossil fuels results in environmental degradation, such as the strip mining and mountaintop removal of coal.

Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. The fuel economy is the energy efficiency of a particular vehicle, is given as a ratio of distance travelled per unit of fuel consumed. Weight-specific efficiency (efficiency per unit weight) may be stated for freight, and passenger-specific efficiency (vehicle efficiency per passenger). The inefficient atmospheric combustion (burning) of fossil fuels in vehicles, buildings, and power plants contributes to urban heat islands.[24]

Conventional production of oil has peaked, conservatively, between 2007 to 2010.[note 19] In 2010, it was estimated that an investment in non-renewable resources of $8 trillion would be required to maintain current levels of production for 25 years.[25] In 2010, governments subsidized fossil fuels by an estimated $500 billion a year.[26] Fossil fuels are also a source of greenhouse gas emissions, leading to concerns about global warming if consumption is not reduced.

The combustion of fossil fuels leads to the release of pollution into the atmosphere. The fossil fuels are mainly based on organic carbon compounds. They are according to the IPCC the causes of the global warming.[27] During the combustion with oxygen in the form of heat energy, carbon dioxide released. Depending on the composition and purity of the fossil fuel also results in other chemical compounds such as nitrogen oxides and soot and fine dust alternativey. Greenhouse gas emissions result from fossil fuel-based electricity generation. Typical megawatt coal plant produces billions of kilowatt hours per year.[28][note 20] From this generation, the carbon dioxide, sulfur dioxide, small airborne particles, nitrogen oxides (NOx) (ozone (smog)), carbon monoxide (CO), hydrocarbons, volatile organic compounds (VOC), mercury, arsenic, lead, cadmium, other heavy metals, and uranium traces are produced.[29][30]

Nuclear power, or nuclear energy, is the use of exothermic nuclear processes,[31] to generate useful heat and electricity. The term includes nuclear fission, nuclear decay and nuclear fusion. Presently the nuclear fission of elements in the actinide series of the periodic table produce the vast majority of nuclear energy in the direct service of humankind, with nuclear decay processes, primarily in the form of geothermal energy, and radioisotope thermoelectric generators, in niche uses making up the rest. Nuclear (fission) power stations, excluding the contribution from naval nuclear fission reactors, provided about 5.7% of the world's energy and 13% of the world's electricity in 2012.[32] In 2013, the IAEA report that there are 437 operational nuclear power reactors,[33] in 31 countries,[34] although not every reactor is producing electricity.[35] In addition, there are approximately 140 naval vessels using nuclear propulsion in operation, powered by some 180 reactors.[36][37][38] As of 2013, attaining a net energy gain from sustained nuclear fusion reactions, excluding natural fusion power sources such as the Sun, remains an ongoing area of international physics and engineering research. More than 60 years after the first attempts, commercial fusion power production remains unlikely before 2050.[39]

There is an ongoing debate about nuclear power.[40][41][42] Proponents, such as the World Nuclear Association, the IAEA and Environmentalists for Nuclear Energy contend that nuclear power is a safe, sustainable energy source that reduces carbon emissions.[43] Opponents, such as Greenpeace International and NIRS, contend that nuclear power poses many threats to people and the environment.[44][45][46]

Nuclear power plant accidents include the Chernobyl disaster (1986), Fukushima Daiichi nuclear disaster (2011), and the Three Mile Island accident (1979).[47] There have also been some nuclear submarine accidents.[47][48][49] In terms of lives lost per unit of energy generated, analysis has determined that nuclear power has caused less fatalities per unit of energy generated than the other major sources of energy generation. Energy production from coal, petroleum, natural gas and hydropower has caused a greater number of fatalities per unit of energy generated due to air pollution and energy accident effects.[50][51][52][53][54] However, the economic costs of nuclear power accidents is high, and meltdowns can take decades to clean up. The human costs of evacuations of affected populations and lost livelihoods is also significant.[55][56]

Along with other sustainable energy sources, nuclear power is a low carbon power generation method of producing electricity, with an analysis of the literature on its total life cycle emission intensity finding that it is similar to other renewable sources in a comparison of greenhouse gas(GHG) emissions per unit of energy generated.[57] With this translating into, from the beginning of nuclear power station commercialization in the 1970s, having prevented the emission of approximately 64 gigatonnes of carbon dioxide equivalent(GtCO2-eq) greenhouse gases, gases that would have otherwise resulted from the burning of fossil fuels in thermal power stations.[58]

As of 2012, according to the IAEA, worldwide there were 68 civil nuclear power reactors under construction in 15 countries,[33] approximately 28 of which in the Peoples Republic of China (PRC), with the most recent nuclear power reactor, as of May 2013, to be connected to the electrical grid, occurring on February 17, 2013 in Hongyanhe Nuclear Power Plant in the PRC.[59] In the USA, two new Generation III reactors are under construction at Vogtle. U.S. nuclear industry officials expect five new reactors to enter service by 2020, all at existing plants.[60] In 2013, four aging, uncompetitive, reactors were permanently closed.[61][62]

Japan's 2011 Fukushima Daiichi nuclear accident, which occurred in a reactor design from the 1960s, prompted a rethink of nuclear safety and nuclear energy policy in many countries.[63] Germany decided to close all its reactors by 2022, and Italy has banned nuclear power.[63] Following Fukushima, in 2011 the International Energy Agency halved its estimate of additional nuclear generating capacity to be built by 2035.[64][65]

Fission economics[edit]
Main article: Economics of new nuclear power plants
The economics of new nuclear power plants is a controversial subject, since there are diverging views on this topic, and multi-billion dollar investments ride on the choice of an energy source. Nuclear power plants typically have high capital costs for building the plant, but low direct fuel costs.

In recent years there has been a slowdown of electricity demand growth and financing has become more difficult, which has an impact on large projects such as nuclear reactors, with very large upfront costs and long project cycles which carry a large variety of risks.[66] In Eastern Europe, a number of long-established projects are struggling to find finance, notably Belene in Bulgaria and the additional reactors at Cernavoda in Romania, and some potential backers have pulled out.[66] Where cheap gas is available and its future supply relatively secure, this also poses a major problem for nuclear projects.[66]

Analysis of the economics of nuclear power must take into account who bears the risks of future uncertainties. To date all operating nuclear power plants were developed by state-owned or regulated utility monopolies[67][68] where many of the risks associated with construction costs, operating performance, fuel price, and other factors were borne by consumers rather than suppliers. Many countries have now liberalized the electricity market where these risks, and the risk of cheaper competitors emerging before capital costs are recovered, are borne by plant suppliers and operators rather than consumers, which leads to a significantly different evaluation of the economics of new nuclear power plants.[69]

Two of the four EPRs under construction (in Finland and France) are significantly behind schedule and substantially over cost.[70] Following the 2011 Fukushima Daiichi nuclear disaster, costs are likely to go up for currently operating and new nuclear power plants, due to increased requirements for on-site spent fuel management and elevated design basis threats.[71]

Sunday, 28 September 2014

Hydroelectricity

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010,[1] and is expected to increase about 3.1% each year for the next 25 years.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. There are now four hydroelectricity plants larger than 10 GW: the Three Gorges Dam and Xiluodu Dam in China, Itaipu Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela.[1]

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.[1] It is also a flexible source of electricity since the amount produced by the plant can be changed up or down very quickly to adapt to changing energy demands. However, damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.[1] Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO
2) than fossil fuel powered energy plants.[2]

Hydropower has been used since ancient times to grind flour and perform other tasks. In the mid-1770s, French engineer Bernard Forest de Bélidor published Architecture Hydraulique which described vertical- and horizontal-axis hydraulic machines. By the late 19th century, the electrical generator was developed and could now be coupled with hydraulics.[5] The growing demand for the Industrial Revolution would drive development as well.[6] In 1878 the world's first hydroelectric power scheme was developed at Cragside in Northumberland, England by William George Armstrong. It was used to power a single arc lamp in his art gallery.[7] The old Schoelkopf Power Station No. 1 near Niagara Falls in the U.S. side began to produce electricity in 1881. The first Edison hydroelectric power plant, the Vulcan Street Plant, began operating September 30, 1882, in Appleton, Wisconsin, with an output of about 12.5 kilowatts.[8] By 1886 there were 45 hydroelectric power plants in the U.S. and Canada. By 1889 there were 200 in the U.S. alone.[5]

At the beginning of the 20th century, many small hydroelectric power plants were being constructed by commercial companies in mountains near metropolitan areas. Grenoble, France held the International Exhibition of Hydropower and Tourism with over one million visitors. By 1920 as 40% of the power produced in the United States was hydroelectric, the Federal Power Act was enacted into law. The Act created the Federal Power Commission to regulate hydroelectric power plants on federal land and water. As the power plants became larger, their associated dams developed additional purposes to include flood control, irrigation and navigation. Federal funding became necessary for large-scale development and federally owned corporations, such as the Tennessee Valley Authority (1933) and the Bonneville Power Administration (1937) were created.[6] Additionally, the Bureau of Reclamation which had began a series of western U.S. irrigation projects in the early 20th century was now constructing large hydroelectric projects such as the 1928 Hoover Dam.[9] The U.S. Army Corps of Engineers was also involved in hydroelectric development, completing the Bonneville Dam in 1937 and being recognized by the Flood Control Act of 1936 as the premier federal flood control agency.[10]

Hydroelectric power plants continued to become larger throughout the 20th century. Hydropower was referred to as white coal for its power and plenty.[11] Hoover Dam's initial 1,345 MW power plant was the world's largest hydroelectric power plant in 1936; it was eclipsed by the 6809 MW Grand Coulee Dam in 1942.[12] The Itaipu Dam opened in 1984 in South America as the largest, producing 14,000 MW but was surpassed in 2008 by the Three Gorges Dam in China at 22,500 MW. Hydroelectricity would eventually supply some countries, including Norway, Democratic Republic of the Congo, Paraguay and Brazil, with over 85% of their electricity. The United States currently has over 2,000 hydroelectric power plants that supply 6.4% of its total electrical production output, which is 49% of its renewable electricity.[6]
Generating methods
Turbine row at Los Nihuiles Power Station in Mendoza, Argentina
Cross section of a conventional hydroelectric dam.
A typical turbine and generator
Conventional (dams)
See also: List of conventional hydroelectric power stations

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. A large pipe (the "penstock") delivers water to the turbine.[13]
Pumped-storage
Main article: Pumped-storage hydroelectricity
See also: List of pumped-storage hydroelectric power stations

This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.[14]

Photosensitivity

Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity.[1][2] The photosensitive ganglion cells in the mammalian eye are a separate class of light-detecting cells from the photoreceptor cells that function in vision.
Sensitivity of the skin to a light source can take various forms. People with particular skin types are more sensitive to sunburn. Particular medications make the skin more sensitive to sunlight; these include most of the tetracycline antibiotics, heart drugs amiodarone, and sulfonamides. Particular conditions lead to increased light sensitivity. Patients with systemic lupus erythematosus experience skin symptoms after sunlight exposure; some types of porphyria are aggravated by sunlight. A rare hereditary condition xeroderma pigmentosum (a defect in DNA repair) is thought to increase the risk of UV-light-exposure-related cancer by increasing photosensitivity.
Veterinary medicine
Main article: Photosensitivity in animals

Photosensitivity occurs in multiple species including sheep, bovine, and horses.

Photosensitizations are classified as primary if an ingested plant contains a photosensitive substance, like hypericin in St John's wort poisoning in sheep, or buckwheat plants (green or dried) in horses.[3]

In hepatogenous photosensitization, the photosensitzing substance is phylloerythrin, a normal end-product of chlorophyll metabolism. [4] It accumulates in the body because of liver damage, reacts with UV light on the skin, and leads to free radical formation. These free radicals damage the skin, leading to ulceration, necrosis, and sloughing. Non-pigmented skin is most commonly affected.
Electronics

Certain electronic devices, such as photodiodes and charge-coupled devices, are designed to be sensitive to light. They are constructed to take advantage of the photoelectric effect, the emission of electrons from matter upon the absorption of electromagnetic radiation. When light (one form of electromagnetic radiation) impinges on the active surface of such a device, electrical current flowing through or electrical charge stored in the device will increase or decrease in proportion to the intensity and wavelength of the light, although there is an upper limit to the amount of electrons released vs the increased intensity of the light, this comes out of quantum mechanics. This trait allows the device to perform regulating and sensing functions of many kinds. For example, a photoresistor circuit may sense ambient light to turn on a street lamp at dusk. Digital cameras use an array of photodiodes whose extreme sensitivity to light allows them to convert incoming photons into varying electrical charges with great accuracy. The varying charges are then encoded in a binary file which can be stored and later viewed on a computer screen or other medium.
Interpretation in chemistry

Chemicals that are photosensitive may undergo chemical reactions when exposed to light. These chemicals, such as hydrogen peroxide and many prescription drugs, are stored in tinted or opaque containers until they are needed to prevent photodegradation. Devices that are photosensitive include the human retina and photographic film; their photosensitive materials undergo a chemical reaction when struck by light.

Typical substances that are photosensitive are alkali salts and silver halides.

Artificial photosynthesis

Artificial photosynthesis is a chemical process that replicates the natural process of photosynthesis, a process that converts sunlight, water, and carbon dioxide into carbohydrates and oxygen. The term is commonly used to refer to any scheme for capturing and storing the energy from sunlight in the chemical bonds of a fuel (a solar fuel). Photocatalytic water splitting converts water into Hydrogen Ions and oxygen, and is a main research area in artificial photosynthesis. Light-driven carbon dioxide reduction is another studied process, replicating natural carbon fixation.

Research developed in this field encompasses design and assembly of devices (and their components) for the direct production of solar fuels, photoelectrochemistry and its application in fuel cells, and engineering of enzymes and photoautotrophic microorganisms for microbial biofuel and biohydrogen production from sunlight. Many, if not most, of the artificial approaches are bio-inspired, i.e., they rely on biomimetics.

Overview

The photosynthetic reaction can be divided into two half-reactions (oxidation and reduction), both of which are essential to producing fuel. In plant photosynthesis, water molecules are photo-oxidized to release oxygen and protons. The second stage of plant photosynthesis (also known as the Calvin-Benson cycle) is a light-independent reaction that converts carbon dioxide into glucose. Researchers of artificial photosynthesis are developing photocatalysts to perform both of these reactions separately. Furthermore, the protons resulting from water splitting can be used for hydrogen production. These catalysts must be able to react quickly and absorb a large percentage of solar photons.[1]

Whereas photovoltaics can provide direct electrical current from sunlight, the inefficiency of fuel production from photovoltaic electricity (indirect process) and the fact sunshine is not constant throughout time sets a limit to its use.[2][3] A way of using natural photosynthesis is via the production of biofuel through biomass, also an indirect process that suffers from low energy conversion efficiency (due to photosynthesis' own low efficiency in converting sunlight to biomass), and clashes with the increasing need of land mass for human food production.[4] Artificial photosynthesis aims then to produce a fuel from sunlight that can be stored and used when sunlight is not available, by using direct processes, that is, to produce a solar fuel. With the development of catalysts able to reproduce the key steps of photosynthesis, water and sunlight would ultimately be the only needed sources for clean energy production. The only by-product would be oxygen, and production of a solar fuel has the potential to be cheaper than gasoline.[5]

One process for the creation of a clean and affordable energy supply is the development of photocatalytic water splitting under solar light. This method of sustainable hydrogen production is a key objective in the development of alternative energy systems of the future.[6] It is also predicted to be one of the more, if not the most, efficient ways of obtaining hydrogen from water.[7] The conversion of solar energy into hydrogen via a water-splitting process assisted by photosemiconductor catalysts is one of the most promising technologies in development.[citation needed] This process has the potential for large quantities of hydrogen to be generated in an ecologically sound method.[citation needed] The conversion of solar energy into a clean fuel (H2) under ambient conditions is one of the greatest challenges facing scientists in the twenty-first century.[8]

Two approaches are generally recognized in the construction of solar fuel cells for hydrogen production:[9]

    A homogeneous system is one where catalysts are not compartmentalized, that is, components are present in the same compartment. This means that hydrogen and oxygen are produced in the same location. This can be a drawback, since they compose an explosive mixture, demanding further gas purification. Also, all components must be active in approximately the same conditions (e.g., pH).
    A heterogeneous system has two separate electrodes, an anode and a cathode, making possible the separation of oxygen and hydrogen production. Furthermore, different components do not necessarily need to work in the same conditions. However, the increased complexity of these systems makes them harder to develop and more expensive.

Another area of research within artificial photosynthesis is the selection and manipulation of photosynthetic microorganisms, namely green microalgae and cyanobacteria, for the production of solar fuels. Many strains are able to produce hydrogen naturally, and scientists are working to improve them.[10] Algae biofuels such as butanol and methanol are produced both at laboratory and commercial scales. This approach has benefited with the development of synthetic biology,[10] which is also being explored by the J. Craig Venter Institute to produce a synthetic organism capable of biofuel production.[11][12]
History

In the late 60s, Akira Fujishima discovered the photocatalytic properties of titanium dioxide, the so-called Honda-Fujishima effect, which could be used for hydrolysis.[13]

The Swedish Consortium for Artificial Photosynthesis, the first of its kind, was established in 1994 as a collaboration between groups of three different universities, Lund, Uppsala and Stockholm, being presently active around Lund and the Ångström Laboratories in Uppsala.[14] The consortium was built with a multidisciplinary approach to focus on learning from natural photosynthesis and applying this knowledge in biomimetic systems.[15] Research in artificial photosynthesis is undergoing a boom at the beginning of the 21st century.[2] In 2000, Commonwealth Scientific and Industrial Research Organisation (CSIRO) researchers publicize their intent to focus on carbon dioxide capture and conversion to hydrocarbons.[16][17] In 2003, the Brookhaven National Laboratory announced the discovery of an important intermediate step in the reduction of CO2 to CO (the simplest possible carbon dioxide reduction reaction), which could lead to better catalyst designing.[18][19]

One of the drawbacks of artificial systems for water-splitting catalysts is their general reliance on scarce, expensive elements, such as ruthenium or rhenium.[2] With the funding of the United States Air Force Office of Scientific Research,[20] in 2008, MIT chemist and head of the Solar Revolution Project Daniel G. Nocera and postdoctoral fellow Matthew Kanan attempted to circumvent this issue by using a catalyst containing the cheaper and more abundant elements cobalt and phosphate.[21][22] The catalyst was able to split water into oxygen and protons using sunlight, and could potentially be coupled to a hydrogen-producing catalyst such as platinum. Furthermore, while the catalyst broke down during catalysis, it could self-repair.[23] This experimental catalyst design was considered a major breakthrough in the field by many researchers.[24][25]

Whereas CO is the prime reduction product of CO2, more complex carbon compounds are usually desired. In 2008, Princeton chemistry professor Andrew B. Bocarsly reported the direct conversion of carbon dioxide and water to methanol using solar energy in a highly efficient photochemical cell.[26]

While Nocera and coworkers had accomplished water splitting to oxygen and protons, a light-driven process to produce hydrogen from protons still needed to be developed. In 2009, the Leibniz Institute for Catalysis reported inexpensive iron carbonyl complexes able to do just this.[27][28] In the same year, researchers at the University of East Anglia also used iron carbonyl compounds to achieve photoelectrochemical hydrogen production with 60% efficiency, this time using a gold electrode covered with layers of indium phosphide to which the iron complexes were linked.[29] Both these processes used a molecular approach, where discrete nanoparticles are responsible for catalysis.

Visible light water splitting with a one piece multijunction cell was first demonstrated and patented by William Ayers at Energy Conversion Devices in 1983.[30] This group demonstrated water photolysis into hydrogen and oxygen, now referred to as an "artificial leaf" or "wireless solar water splitting" with a low cost, thin film amorphous silicon multijunction cell directly immersed in water. Hydrogen evolved on the front amorphous silicon surface decorated with various catalysts while oxygen evolved off the back metal substrate which also eliminated the problem of mixed hydrogen/oxygen gas evolution. A Nafion membrane above the immersed cell provided a path for proton transport. The higher photovoltage available from the multijuction thin film cell with visible light was a major advance over previous photolysis attempts with UV sensitive single junction cells. The group's patent also lists several other semiconductor multijunction compositions in addition to amorphous silicon.

In 2009, F. del Valle and K. Domen showed the impact of the thermal treatment in a closed atmosphere using Cd1-xZnxS photocatalysts. Cd1-xZnxS solid solution reports high activity in hydrogen production from water splitting under sunlight irradiation.[31] A mixed heterogeneous/molecular approach by researchers at the University of California, Santa Cruz, in 2010, using both nitrogen-doped and cadmium selenide quantum dots-sensitized titanium dioxide nanoparticles and nanowires, also yielded photoproduced hydrogen.[32]

Artificial photosynthesis remained an academic field for many years. However, in the beginning of 2009, Mitsubishi Chemical Holdings was reported to be developing its own artificial photosynthesis research by using sunlight, water and carbon dioxide to "create the carbon building blocks from which resins, plastics and fibers can be synthesized."[33] This was confirmed with the establishment of the KAITEKI Institute later that year, with carbon dioxide reduction through artificial photosynthesis as one of the main goals.[34][35]

In 2010, the DOE established, as one of its Energy Innovation Hubs, the Joint Center for Artificial Photosynthesis.[36] The mission of JCAP is to find a cost-effective method to produce fuels using only sunlight, water, and carbon-dioxide as inputs.  JCAP is led by a team from Caltech, led by Professor Nathan Lewis and brings together more than 120 scientists and engineers from Caltech and its lead partner, Lawrence Berkeley National Laboratory. JCAP also draws on the expertise and capabilities of key partners from Stanford University, the University of California at Berkeley, UCSB, UCI, and UCSD, and the Stanford Linear Accelerator.  In addition, JCAP serves as a central hub for other solar fuels research teams across the United States, including 20 DOE Energy Frontier Research Center.  The program has a budget of $122M over five years, subject to Congressional appropriation[37]

Also in 2010, a team led by professor David Wendell at the University of Cincinnati successfully demonstrated photosynthesis in an artificial construct consisting of enzymes suspended in frog foam.[38]

In 2011, Daniel Nocera and his research team announced the creation of the first practical artificial leaf. In a speech at the 241st National Meeting of the American Chemical Society, Nocera described an advanced solar cell the size of a poker card capable of splitting water into oxygen and hydrogen, approximately ten times more efficient than natural photosynthesis.[39] The cell is mostly made of inexpensive materials that are widely available, works under simple conditions, and shows increased stability over previous catalysts: in laboratory studies, the authors demonstrated that an artificial leaf prototype could operate continuously for at least forty-five hours without a drop in activity.[40] In May 2012, Sun Catalytix, the startup based on Nocera's research, stated that it will not be scaling up the prototype as the device offers few savings over other ways to make hydrogen from sunlight.[41]

Solar architecture

Solar architecture is the integration of solar panel technology with modern building techniques. The use of flexible thin film photovoltaic modules provides fluid integration with steel roofing profiles that enhances the building's design. Orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air also constitute as solar architecture.
Initial development of solar architecture has been limited by the rigidity and weight of standard solar power panels. The continued development of photovoltaic (PV) thin film solar has provided a lightweight yet robust vehicle to harness solar energy to reduce a building's impact on the environment.

Solar thermal energy

Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, and in the residential and commercial sectors. The first installation of solar thermal energy equipment occurred in the Sahara Desert approximately in 1910 and was a steam engine without a kettle and fire but with a mirror system for sun light collection to heat water for the needed steam pressure. Because of the influence of World War I, liquid fuel was better developed and the Sahara project was abandoned, only to be reused several decades later.

Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for fulfilling heat requirements up to 300 deg C / 20 bar pressure in industries, and for electric power production. However, there is a term that used for both the applications. Concentrated Solar Thermal (CST) for fulfilling heat requirements in industries and Concentrated Solar Power (CSP) when the heat collected is used for power generation. CST and CSP are not replaceable in terms of application. The 377 MW Ivanpah Solar Power Facility is the largest solar power plant in the world, located in the Mojave Desert of California. Other large solar thermal plants include the SEGS installation (354 MW), also in the Mojave, as well as the Solnova Solar Power Station (150 MW), the Andasol solar power station (150 MW), and Extresol Solar Power Station (100 MW), all in Spain.

Systems for utilizing low-temperature solar thermal energy include means for heat collection; usually heat storage, either short-term or interseasonal; and distribution within a structure or a district heating network. In some cases more than one of these functions is inherent to a single feature of the system (e.g. some kinds of solar collectors also store heat). Some systems are passive, others are active (requiring other external energy to function).[1]

Heating is the most obvious application, but solar cooling can be achieved for a building or district cooling network by using a heat-driven absorption or adsorption chiller (heat pump). There is a productive coincidence that the greater the driving heat from insulation, the greater the cooling output. In 1878, Auguste Mouchout pioneered solar cooling by making ice using a solar steam engine attached to a refrigeration device.[2]

In the United States, heating, ventilation, and air conditioning (HVAC) systems account for over 25% (4.75 EJ) of the energy used in commercial buildings and nearly half (10.1 EJ) of the energy used in residential buildings.[3][4] Solar heating, cooling, and ventilation technologies can be used to offset a portion of this energy.

In Europe, since the mid-1990s about 125 large solar-thermal district heating plants have been constructed, each with over 500 m2 (5400 ft2) of solar collectors. The largest are about 10,000 m2, with capacities of 7 MW-thermal and solar heat costs around 4 Eurocents/kWh without subsidies.[5] 40 of them have nominal capacities of 1 MW-thermal or more. The Solar District Heating program (SDH) has participation from 14 European Nations and the European Commission, and is working toward technical and market development, and holds annual conferences.[6]
Low-temperature collectors
Main article: Solar thermal collector

Glazed Solar Collectors are designed primarily for space heating and they recirculate building air through a solar air panel where the air is heated and then directed back into the building. These solar space heating systems require at least two penetrations into the building and only perform when the air in the solar collector is warmer than the building room temperature. Most glazed collectors are used in the residential sector.
Unglazed, "transpired" air collector

Unglazed Solar Collectors are primarily used to pre-heat make-up ventilation air in commercial, industrial and institutional buildings with a high ventilation load. They turn building walls or sections of walls into low cost, high performance, unglazed solar collectors. Also called, "transpired solar panels", they employ a painted perforated metal solar heat absorber that also serves as the exterior wall surface of the building. Heat conducts from the absorber surface to the thermal boundary layer of air 1 mm thick on the outside of the absorber and to air that passes behind the absorber. The boundary layer of air is drawn into a nearby perforation before the heat can escape by convection to the outside air. The heated air is then drawn from behind the absorber plate into the building's ventilation system.

A Trombe wall is a passive solar heating and ventilation system consisting of an air channel sandwiched between a window and a sun-facing thermal mass. During the ventilation cycle, sunlight stores heat in the thermal mass and warms the air channel causing circulation through vents at the top and bottom of the wall. During the heating cycle the Trombe wall radiates stored heat.[7]

Solar roof ponds are unique solar heating and cooling systems developed by Harold Hay in the 1960s. A basic system consists of a roof-mounted water bladder with a movable insulating cover. This system can control heat exchange between interior and exterior environments by covering and uncovering the bladder between night and day. When heating is a concern the bladder is uncovered during the day allowing sunlight to warm the water bladder and store heat for evening use. When cooling is a concern the covered bladder draws heat from the building's interior during the day and is uncovered at night to radiate heat to the cooler atmosphere. The Skytherm house in Atascadero, California uses a prototype roof pond for heating and cooling.[8]

Solar space heating with solar air heat collectors is more popular in the USA and Canada than heating with solar liquid collectors since most buildings already have a ventilation system for heating and cooling. The two main types of solar air panels are glazed and unglazed.

Of the 21,000,000 square feet (2,000,000 m2) of solar thermal collectors produced in the United States in 2007, 16,000,000 square feet (1,500,000 m2) were of the low-temperature variety.[9] Low-temperature collectors are generally installed to heat swimming pools, although they can also be used for space heating. Collectors can use air or water as the medium to transfer the heat to their destination.
Heat storage in low-temperature solar thermal systems
Main article: Seasonal thermal energy storage

Interseasonal storage. Solar heat (or heat from other sources) can be effectively stored between opposing seasons aquifers, underground geological strata, large specially constructed pits, and large tanks that are insulated and covered with earth.

Short-term storage. Thermal mass materials store solar energy during the day and release this energy during cooler periods. Common thermal mass materials include stone, concrete, and water. The proportion and placement of thermal mass should consider several factors such as climate, daylighting, and shading conditions. When properly incorporated, thermal mass can passively maintain comfortable temperatures while reducing energy consumption.

Photovoltaics

Photovoltaics (PV) is a method of generating electrical power by converting sunlight into direct current electricity using semiconducting materials that exhibit the photovoltaic effect. A photovoltaic system employs solar panels composed of a number of solar cells to supply usable solar power. Power generation from solar PV has long been seen as a clean sustainable[1] energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialized applications, and grid-connected PV systems have been in use for over twenty years.[2]

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured,[2][3] and the levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions.[4] Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.[5] With current technology, photovoltaics recoup the energy needed to manufacture them in 1.5 (in Southern Europe) to 2.5 years (in Northern Europe).[6]

Solar PV is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integrated photovoltaics or simply rooftop).

In 2013, the fast-growing capacity of worldwide installed solar PV increased by 38 percent to 139 gigawatts (GW). This is sufficient to generate at least 160 terawatt hours (TWh) or about 0.85 percent of the electricity demand on the planet. China, followed by Japan and the United States, is now the fastest growing market, while Germany remains the world's largest producer, contributing almost 6 percent to its national electricity demands.[7][8][9]
The term "photovoltaic" comes from the Greek φῶς (phōs) meaning "light", and from "volt", the unit of electro-motive force, the volt, which in turn comes from the last name of the Italian physicist Alessandro Volta, inventor of the battery (electrochemical cell). The term "photo-voltaic" has been in use in English since 1849.[10]
Solar cells
Solar cells produce electricity directly from sunlight
Global solar potential
Main article: Solar cell

Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons. The photovoltaic effect refers to photons of light exciting electrons into a higher state of energy, allowing them to act as charge carriers for an electric current. The photovoltaic effect was first observed by Alexandre-Edmond Becquerel in 1839.[11][12] The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode.

Solar cells produce direct current electricity from sun light which can be used to power equipment or to recharge a battery. The first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boats, recreational vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic protection of pipelines.

Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide.[13] Copper solar cables connect modules (module cable), arrays (array cable), and sub-fields. Because of the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.[14][15][16]

Solar photovoltaics power generation has long been seen as a clean energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The technology is “inherently elegant” in that the direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialised applications, and grid-connected systems have been in use for over twenty years.

Cells require protection from the environment and are usually packaged tightly behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in multiples as arrays.

Photovoltaic power capacity is measured as maximum power output under standardized test conditions (STC) in "Wp" (Watts peak).[17] The actual power output at a particular point in time may be less than or greater than this standardized, or "rated," value, depending on geographical location, time of day, weather conditions, and other factors.[18] Solar photovoltaic array capacity factors are typically under 25%, which is lower than many other industrial sources of electricity.[19]

Solar thermal collector

A solar thermal collector collects heat by absorbing sunlight. A collector is a device for capturing solar radiation. Solar radiation is energy in the form of electromagnetic radiation from the infrared (long) to the ultraviolet (short) wavelengths. The quantity of solar energy striking the Earth's surface averages about 1,000 watts per square meter under clear skies, depending upon weather conditions, location and orientation.

The term "solar collector" commonly refers to solar hot water panels, but may refer to installations such as solar parabolic troughs and solar towers; or basic installations such as solar air heaters. Solar power plants usually use the more complex collectors to generate electricity by heating a fluid to drive a turbine connected to an electrical generator.[1] Simple collectors are typically used in residential and commercial buildings for space heating.
Heat collectors

Solar collectors are either non-concentrating or concentrating. In the non-concentrating type, the collector area (i.e., the area that intercepts the solar radiation) is the same as the absorber area (i.e., the area absorbing the radiation). In these types the whole solar panel absorbs light. Concentrating collectors have a bigger interceptor than absorber.[2]

Flat-plate and evacuated-tube solar collectors are used to collect heat for space heating, domestic hot water or cooling with an absorption chiller.
Flat plate collectors
Flat plate thermal system for water heating deployed on a flat roof.

Flat-plate collectors, developed by Hottel and Whillier in the 1950s, are the most common type. They consist of (1) a dark flat-plate absorber, (2) a transparent cover that reduces heat losses, (3) a heat-transport fluid (air, antifreeze or water) to remove heat from the absorber, and (4) a heat insulating backing. The absorber consists of a thin absorber sheet (of thermally stable polymers, aluminum, steel or copper, to which a matte black or selective coating is applied) often backed by a grid or coil of fluid tubing placed in an insulated casing with a glass or polycarbonate cover. In water heat panels, fluid is usually circulated through tubing to transfer heat from the absorber to an insulated water tank. This may be achieved directly or through a heat exchanger.

Most air heat fabricators and some water heat manufacturers have a completely flooded absorber consisting of two sheets of metal which the fluid passes between. Because the heat exchange area is greater they may be marginally more efficient than traditional absorbers.[3] Sunlight passes through the glazing and strikes the absorber plate, which heats up, changing solar energy into heat energy. The heat is transferred to liquid passing through pipes attached to the absorber plate. Absorber plates are commonly painted with "selective coatings," which absorb and retain heat better than ordinary black paint. Absorber plates are usually made of metal—typically copper or aluminum—because the metal is a good heat conductor. Copper is more expensive, but is a better conductor and less prone to corrosion than aluminum. (See: Copper in solar water heaters). In locations with average available solar energy, flat plate collectors are sized approximately one-half to one square foot per gallon of one day's hot water use. Absorber piping configurations include:

    harp – traditional design with bottom pipe risers and top collection pipe, used in low pressure thermosyphon and pumped systems;
    serpentine – one continuous S that maximizes temperature but not total energy yield in variable flow systems, used in compact solar domestic hot water only systems (no space heating role);
    flooded absorber consisting of two sheets of metal stamped to produce a circulation zone;
    boundary layer absorber collectors consisting of several layers of transparent and opaque sheets that enable absorption in a boundary layer. Because the energy is absorbed in the boundary layer, heat conversion may be more efficient than for collectors where absorbed heat is conducted through a material before the heat is accumulated in a circulating liquid.[citation needed]

Polymer flat plate collectors are an alternative to metal collectors and are now being produced in Europe. These may be wholly polymer, or they may include metal plates in front of freeze-tolerant water channels made of silicone rubber. Polymers are flexible and therefore freeze-tolerant and can employ plain water instead of antifreeze, so that they may be plumbed directly into existing water tanks instead of needing heat exchangers that lower efficiency. By dispensing with a heat exchanger, temperatures need not be quite so high for the circulation system to be switched on, so such direct circulation panels, whether polymer or otherwise, can be more efficient, particularly at low light levels. Some early selectively coated polymer collectors suffered from overheating when insulated, as stagnation temperatures can exceed the polymer's melting point.[4][5] For example, the melting point of polypropylene is 160 °C (320 °F), while the stagnation temperature of insulated thermal collectors can exceed 180 °C (356 °F) if control strategies are not used. For this reason polypropylene is not often used in glazed selectively coated solar collectors. Increasingly polymers such as high temperate silicones (which melt at over 250 °C (482 °F)) are being used. Some non polypropylene polymer based glazed solar collectors are matte black coated rather than selectively coated to reduce the stagnation temperature to 150 °C (302 °F) or less.

In areas where freezing is a possibility, freeze-tolerance (the capability to freeze repeatedly without cracking) can be achieved by the use of flexible polymers. Silicone rubber pipes have been used for this purpose in UK since 1999. Conventional metal collectors are vulnerable to damage from freezing, so if they are water filled they must be carefully plumbed so they completely drain using gravity before freezing is expected, so that they do not crack. Many metal collectors are installed as part of a sealed heat exchanger system. Rather than having potable water flow directly through the collectors, a mixture of water and antifreeze such as propylene glycol is used. A heat exchange fluid protects against freeze damage down to a locally determined risk temperature that depends on the proportion of propylene glycol in the mixture. The use of glycol lowers the water's heat carrying capacity marginally, while the addition of an extra heat exchanger may lower system performance at low light levels.

A pool or unglazed collector is a simple form of flat-plate collector without a transparent cover. Typically polypropylene or EPDM rubber or silicone rubber is used as an absorber. Used for pool heating it can work quite well when the desired output temperature is near the ambient temperature (that is, when it is warm outside). As the ambient temperature gets cooler, these collectors become less effective. Most flat plate collectors have a life expectancy of over 25 years.

Solar energy

Solar energy is radiant light and heat from the sun harnessed using a range of ever-evolving technologies such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture and artificial photosynthesis.[1][2]

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared".[1]

The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere.[3] Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet.[4]

Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their temperature. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface, completing the water cycle. The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones.[5] Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C.[6] By photosynthesis green plants convert solar energy into chemical energy, which produces food, wood and the biomass from which fossil fuels are derived.[7]
Yearly Solar fluxes & Human Energy Consumption
Solar     3,850,000 EJ      [8]
Wind     2,250 EJ      [9]
Biomass potential     ~200 EJ      [10]
Primary energy use (2010)     539 EJ      [11]
Electricity (2010)     ~67 EJ      [12]
1 Exajoule (EJ) is 1018 Joules or 278 billion kilowatt-hours (kW·h).

The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year.[8] In 2002, this was more energy in one hour than the world used in one year.[13][14] Photosynthesis captures approximately 3,000 EJ per year in biomass.[15] The technical potential available from biomass is from 100–300 EJ/year.[10] The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined,[16]

Solar energy can be harnessed at different levels around the world, mostly depending on distance from the equator.[17]
Early commercial adaption
A 1917 patent drawing for Shuman's parabolic trough solar energy system

In 1897, Frank Shuman, a U.S. inventor, engineer and solar energy pioneer built a small demonstration solar engine that worked by reflecting solar energy onto square boxes filled with ether, which has a lower boiling point than water, and were fitted internally with black pipes which in turn powered a steam engine. In 1908 Shuman formed the Sun Power Company with the intent of building larger solar power plants. He, along with his technical advisor A.S.E. Ackermann and British physicist Sir Charles Vernon Boys,[18] developed an improved system using mirrors to reflect solar energy upon collector boxes, increasing heating capacity to the extent that water could now be used instead of ether. Shuman then constructed a full-scale steam engine powered by low-pressure water, enabling him to patent the entire solar engine system by 1912.

Shuman built the world’s first solar thermal power station in Maadi, Egypt between 1912 and 1913. Shuman’s plant used parabolic troughs to power a 45-52 kilowatt (60-70 H.P.) engine that pumped more than 22,000 litres of water per minute from the Nile River to adjacent cotton fields. Although the outbreak of World War I and the discovery of cheap oil in the 1930s discouraged the advancement of solar energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy.[19] In 1916 Shuman was quoted in the media advocating solar energy's utilization, saying:

    We have proved the commercial profit of sun power in the tropics and have more particularly proved that after our stores of oil and coal are exhausted the human race can receive unlimited power from the rays of the sun.
    —Frank Shuman, New York Times, July 2, 1916[20]
Applications of solar technology
Average insolation showing land area (small black dots) required to replace the world primary energy supply with solar electricity (18 TW is 568 Exajoule, EJ, per year). Insolation for most people is from 150 to 300 W/m2 or 3.5 to 7.0 kWh/m2/day.

Solar energy refers primarily to the use of solar radiation for practical ends. However, all renewable energies, other than geothermal and tidal, derive their energy from the sun.

Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies.[21]