The Power of the SunAn Introduction to the History, Use and Potential of Solar EnergyNovember 6th, 2006Courtesy of Insurgent 49 
The sun makes life possible on Earth, and is ultimately the source of almost all energy used on Earth. In fact, the Earth receives more energy from the sun in an hour than all of humankind uses in a year. In Alaska, the direct use of solar energy is impractical during the darkest months of the year. However, the Arctic Circle receives 230 more hours of possible sunlight than the equator, due to the extended daylight of summer. However, the summer sunlight received at the Arctic Circle is much less intense than that received at the equator, and is subject to more cloudy days. Four to five billion years from now, when the sun runs out of its hydrogen fuel to power its nuclear fusion reactions, the sun will start dying and devour the Earth as it becomes a red giant star. Until then, solar energy will be abundant, although diffuse and intermittent in its pure form. Fossil fuels are actually stored solar energy than has been concentrated by geologic processes, and the renewable energy sources of wind, hydropower, wave, tidal and biomass are indirectly driven by the sun. Like all renewable energy sources, direct solar energy's chief advantages are that there are no fuel costs, and no polluting fossil fuels are burned. Direct use of solar energy falls under two categories: photovoltaic and solar thermal. Solar Thermal EnergySolar thermal energy is direct use of solar heat by use of reflectors or heat-absorbing material, and is the most widely used form of direct solar energy in the world. The oldest application of solar thermal energy is called "passive." In passive solar heating, the building itself serves as a collector of solar thermal energy. Greenhouses made of glass or other transparent materials are perhaps the most well know application of passive solar. Early passive solar building designs include the Anasazi cliff dwellings in the southwest's Four Corners region, and south-facing porticos in the buildings of Ancient Greece. The first glass windows were used in ancient Rome, beginning the era of "daylighting" with skylights. Solar concentrating mirror dishesEven in Alaska, the passive solar design of buildings can result in substantial energy savings. Such buildings are designed with south facing windows and other surfaces to absorb as much sunlight as possible. The "Northwestern" home style, popular in the Pacific Northwest between 1935 and 1960, was noted for its use of large glass windows that extended to the floor. A passive solar thermal energy application involving seawater is that of solar desalination, which uses a passive solar still to evaporate salt water. Solar desalination stills have been an important source of water for remote desert seacoasts for decades. The other type of solar thermal energy is known as "active" solar heating, which uses electrical or mechanical equipment such as pumps or fans to capture and control the solar heat. The most common type of active solar heat collector is the flat-plate solar collector, which absorbs solar heat directly. Other types of active solar thermal systems use mirrors or lenses to concentrate the sun's heat. Such "active" solar heating systems can be very cost-effective in sunny climates, and solar cooking stoves are very practical in developing countries. Solar water heating, such as for heating swimming pools, are already common domestic uses in sunny areas of the U.S. Solar ovens use concentrated sunshine as a "fuel" for cooking using mirrors or Fresnel lenses. If concentrated enough, solar thermal energy can heat steam hot enough to drive turbines. Solar Energy Resources in the USA small number of solar thermal power stations produce electricity in California, Arizona and Nevada. Several more solar-thermal power plants are being planned in these three states. In the sunniest parts of the world, the electricity produced by solar thermal power plants costs between 5 and 13 cents per kWh, considerably less than that from PV systems (described below). Ocean Thermal Energy Conversion (OTEC) is an experimental form of solar thermal energy that harnesses the warm surface of sun-baked ocean waters. OTEC power plants are still only experimental, and very inefficient. It also could be practical only in the tropics, and certainly not in cold Alaskan waters. The only operating OTEC power plant in the USA is an experimental Dept. of Energy facility on Hawaii's big island. Photovoltaic Solar EnergyPhotovoltaic (PV) cells produce a small amount of electric current when light shines on them. Invented by Bell Labs in 1954, PV cells are combined into modules and panels to produce useful amounts of electric power. Photovoltaics have long had many niche applications, such as PV-powered satellites, watches, and calculators. Since the launch of Vanguard 1 in 1958, PV technology is the energy source of choice for such extraterrestrial applications, satellites and space probes. PV panels can easily be installed on roofs and other structures integrated with a building's architecture. The highest energy conversion efficiency yet achieved by a PV cell in the laboratory is 35%, that is, 35% of the total light energy contained in the photons hitting the solar cell is converted into electricity. Commercially available solar panels today convert between 5 and 19% of the sun's energy into electricity. Flat plate solar collectorAll of the PV cells installed in the world today have an electric generating capacity of about 5,000 megawatts (MW), which represents a mere 0.15% of the world's total existing power generation capacity. However, this amount grew by over 1700 MW last year alone and is expected to grow exponentially in the years ahead. Japan is the world's biggest manufacturer of PV cells (833 MW of PV capacity produced in 2005), followed by Germany (353 MW) and the US (153 MW). Japan and Germany are undeniably the world leaders in PV technology. The Japanese electronics Sharp is the world's largest manufacturer of PV cells. The Japanese electronic firms Kyocera, Sanyo Electric, and Mitsubishi also rank on the top ten list of the world's largest PV manufacturers, along with the PV manufacturing divisions of the oil giants BP and Shell-Siemens. The Chinese PV manufacturer Shangde (also called "Suntech") started production in 2002, and is already the biggest PV maker in China. Shangde sells its PV solar modules for $3.38/watt, which is lower than the global PV average of $4.30/watt estimated by the solar industry consultants Photon Consulting. The current price of PV-generated electricity is around 20 to 25 cents per kWh, or about double what most Alaskans pay for the grid's power. Over the past several years, the prices of PV modules have been falling 5 to 8% annually. Home-sized PV systems are used in rural Alaska, for which battery storage systems and power control electronics are needed. Detailed descriptions of home-scale PV systems are often featured in Home Power magazine: (www.homepower.com). There are many different types of PV cells in use and under development. The most common types of PV in use today are the crystalline, polycrystalline, and amorphous forms of silicon. Crystalline PV cells are made from single-crystal wafer of silicon cut from cylindrical ingots and tend to be more expensive, and more efficient, than polycrystalline solar cells, which are made from cast square ingots, which are large blocks of molten silicon carefully cooled and solidified. Amorphous cells made from the non-crystalline form of silicon, the most common type of solar cell used for pocket calculators. Amorphous PV cells are only half as efficient as crystalline cells, but cost at most one quarter of crystalline cells. Recent PV technological developments that have become commercial in the past few years include thin film solar cells, which can be made from a variety of semiconductors, and "organic", or polymer, PV cells are made from polymers similar to plastics. Polymer solar cells have the potential to become as cheap as most plastics, though are currently relatively inefficient and have a much shorter useful life compared to silicon solar cells. More experimental types of solar cells still in the research stage include nano-crystal cells and photoelectrochemical cells, which use light-absorbing dyes. Challenges and EconomicsThe most obvious challenge facing solar energy is that the sun shines only during the day. Summer is the time of least energy demand for Alaskans, although this is also the time of year with abundant daylight. On average, the sunniest parts of Alaska receive less than half of the amount of the total solar energy throughout the year than the sunniest places in the southwestern US. Also, large-scale storage methods for solar energy are unavailable today. Electric storage batteries have only proven practical for storing small amounts of electricity, at least in terms of the electric power grid's size. In Fairbanks, the Golden Valley Electric Association operates one of the largest battery storage systems in the world. However, in the event of a generation or transmission related outage, it can provide 27 megawatts of power for only 15 minutes. For smaller systems, cold winter temperatures shorten battery life, which have to be replaced every few years. Solar "ponds" can use large amounts of water to store solar thermal energy, though have so far only proven practical to store heat for no more than a couple of days. The seasonal storage of solar energy is not yet practical, though could become feasible in the future with large-scale hydrogen storage. PV modules typically produce the most power during the part of day with the highest electricity demand, and PV-produced electricity remains very expensive compared to other sources of electricity. The American Solar Energy Society (www.ases.org) estimates the cost of solar PV power at 18 to 25 cents per kWh in the contiguous US. For most home applications, PV systems also require expensive battery and AC inverters. Solar thermal energy could be cost effective for certain Alaska heating applications, particularly in passive-solar designed homes. For home installations, there are a limited amount of qualified commercial installers of solar energy equipment. The solar energy industry of the 1970s and 80s was plagued by incompetent installers, leading to an unfair perception that home solar technology is inherently unreliable. Another common myth, dating from the 1970s, is that PV cells never produce more energy than it takes to manufacture them. While the expected working lifetime of a PV module is around 40 years, the energy payback time of such a module is anywhere from 1 to 30 years, and usually under five, depending on the type and the amount of sun where it is used. This means that PV panels can be net energy producers , and can "reproduce" themselves up to more than 30 times over their lifetime. International Examples of Solar EnergyJapan is the nation that manufacturers the most PV cells, and also consumes half of the total worldwide PV production. In addition, solar hot water heaters are used by more than 10 million Japanese households. Japan imports almost all of its oil, gas, and coal, as well as the uranium needed for the country's large nuclear power capacity. For these reasons, the Japanese government has aggressively supported the solar energy industry since the 1960s. Next to Japan, Germany has the most successful solar energy program in the world, despite the fact that it is not a particularly sunny country. Most of the world's largest PV power plants are in Germany, and the nation alone has more than three-quarters of the European Union's 1000 MW of installed PV capacity. The European Commission is setting a target of 4500 MW of total PV capacity installed within the EU by 2010. Sunny Spain has a thriving PV manufacturing industry and solar energy research programs, and PV is widely used in rural parts of the country. The city government of Barcelona now requires all new buildings heat at least 60% of their hot water, on an annual basis, from solar thermal systems. By 2010, Portugal plans to get 30% of its electric power from renewables, including existing hydroelectric plants. A $78 million, 11 MW solar PV power plant is under construction in southeastern Portugal, consisting of 52,000 PV modules spread over 150 acres. Plans for even larger solar power plants in Portugal have been proposed. Solar thermal plant in Odeillo, FranceElsewhere in the Mediterranean region, the island of Cyprus has cut its oil imports by 10% just by using solar water heaters atop most buildings, and Greece is building a 50 MW PV power plant on the island of Crete. The use of solar energy in Israel began in the 1950s, and today solar water heaters are mandatory for all residences. In 2005, the Israeli government announced an international contract for building a 100 MW solar trough plant in the Negev Desert to supply the electricity needs of more than 200,000 Israelis living in southern Israel. Next door in Egypt, small PV systems are used in rural areas for powering lights and water pumps, and several small-scale solar-thermal desalination plants have also been built. A combined natural gas/solar power plant being built near Giza, Egypt will feature 30 MW of solar-thermal power generation capacity. Solar energy is also growing across southern and eastern Asia. Behind Japan, Germany, and the USA, the nation with the fourth-largest installed PV capacity is India, which boasts much government support and subsidies for solar energy. China is already the world leader in the number of solar thermal installations, with 30 million Chinese households using solar water heaters, and is expected to soon overtake the US in PV production. In Australia, PV electricity has already proven competitive in remote small communities where diesel fuel is very expensive, and in urban niche applications such as lighting signs and bus shelters. Sales of solar energy are also booming in Africa, where a basic PV panel and wiring, ranging in power output from 12 to 30 watts, can be purchased for as a little as $100. While charging a car battery, such as system can store about enough energy to power a fluorescent lamp or TV set for several hours. In Kenya, more homes are adopting small solar-power systems than are connecting to the national grid. The country has the highest per-capita number of installed PV systems (though not in total PV capacity), and more than 30,000 such systems are sold in Kenya annually. Significant solar potential also exists in Latin America and the Caribbean, though it is slower to be developed there than in the other equatorial and sub-tropical regions of the world. Overall, the world's equatorial band has the richest solar resources, and contains many poor countries that have the most to gain from solar technology as it becomes more economical. Solar Energy in the USThe world's first commercial solar hot water heater was the Climax Solar-Water Heater, introduced in 1891 by Clarence Kemp of Baltimore, Maryland. Soon, newer and improved solar water heaters started catching on in southern California and Florida. For example, one third of the homes in Pasadena, near Los Angeles, had solar hot water heaters during the early 1900s. By 1941, more than half of Florida's population used hot water heated by the sun. Solar water heaters remained popular in the US Sun Belt into the 1940s, though rapidly declined after World War II. In 1951, President Harry Truman established a materials policy commission with William S. Paley, then the CEO of CBS Broadcasting, as chairman. The 1952 Paley Commission report recommended large-scale solar energy programs for USA, including the installation of 15 million solar water heaters by 1975. Unfortunately, its recommendations were not heeded, as the Atomic Energy Commission started attracting huge amounts of federal funding with its promises of cheap nuclear energy. Today, the leading US State for solar energy is undoubtedly California. The Golden State has embarked on an ambitious "Million Solar Roof" program, intended to create 3000 MW of roof-installed solar power within the state by the year 2018. In August 2006, Governor Schwarzenegger signed into law a requirement that homebuilders offer their customers the option of PV-integrated roof tiles. The Solar Energy Generating Systems (SEGS) facility near Barstow, California in the Mojave Desert, owned and operated by FPL Energy, consists of nine separate "parabolic trough" solar thermal power plants. It is the world's largest solar power generation plant with a total of 354 MW of generation capacity, and its 400,000 mirrors are spread over an area of one thousand acres. Phoenix-based Sterling Energy Systems is planning several large solar thermal power plants in the Mojave Desert in southern California. In January 2006, the California Public Utilities Commission approved the California Solar Incentive Program, which will provide $2.8 billion in incentives toward solar development over the next 11 years. Outside of California, the 64 MW Nevada Solar One solar thermal power plant in Boulder City, Nevada, being developed by the Spanish conglomerate Acciona, is scheduled to come on-line in 2007. The utility Xcel Energy is developing an 8 MW solar power plant in south central Colorado, to be online by the end of 2007. Two different solar technologies will be used at the site: 1.2 MW of this plant's capacity will be PV, and 6.8 MW will be flat-plate solar thermal collectors. The National Renewable Energy Laboratory (www.nrel.gov) in Golden, Colorado is the hub of the US government's solar energy research. However, the present amount of government support for solar energy in the US is well below that of the European Union and Japan. Ironically, the US was also the country that invented both the PV solar cell and the modern solar water heater.  Solar Energy in AlaskaSolar energy is more widely used in Alaska than most people expect. Long life and low maintenance are benefits of solar energy systems for remote Alaska applications. Summer-only remote buildings such as fishing cabins offer good possibilities for solar energy use. PV is by far the most common form of solar energy used in Alaska, with several hundred kW of generation capacity installed statewide. Most solar PV systems installed in Alaska are niche applications at remote sites such as navigational aids and communications facilities. For example, the Alaska Railroad uses PV panels to power its remote railroad crossing signals and communications equipment. Solar Unit In St. Elias RangeSolar energy technology has even made inroads into rural Alaska villages. In 2001, a $160,000 PV and battery system was installed in Lime Village in Southwest Alaska, funded by BP, has reduced village diesel costs. Arctic Village in the Brooks Range also uses PV power in the summer. Examples of solar thermal and PV technology in Alaska can be found in the book A Solar Design Manual for Alaska, by Rich Siefert of the University of Alaska Fairbanks Cooperative-Extension Service This publication can be downloaded for free from the webpage www.alaskasun.org. The sun may not shine very often or very strongly in Alaska, but it still will provide useful energy for those clever and patient enough to harness it.
Solar Energy links: Brian Yanity is a graduate student at UAA, activist and freelance writer. He resides in an undisclosed location in Southcentral Alaska, and can be reached at byanity@insurgent49.com. |
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