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Solar Facts and Information |
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Introduction to Solar EnergySolar energy is simply energy drawn from the sun. Whether we are enjoying the heat of the sun on a warm day, heating our water, or turning the sun's light into electricity, we are using solar energy. In fact, most forms of life use solar energy either directly or indirectly. We have always had a deep respect for our nearest star and have even deified it in many religions. It is because of the sun that life (as we know it) can even exist on earth. We have always used the sun for our most fundamental needs, and have recently learned how to use it even more by generating electricity from its light and heating our water with its warmth. This section of our website provides a little information about how we can do this. Sunlight is converted directly to electricity using solar cells. Solar cells are small, square-shaped panel semiconductors made from silicon and other conductive materials, manufactured in thin wafers or film on a substrate. When sunlight strikes a solar cell, chemical reactions release electrons, generating electric current. Solar cells are also called photovoltaic cells - or PV cells for short - and can be found on many small appliances, like calculators, toys and even hats. Solar Photovoltaic (PV) Electricity GenerationIndividual
PV cells are arranged together into a PV module and the modules are grouped
together in an array. Some arrays are set on special tracking devices
to follow the sunlight all day long. The electrical energy from solar
cells can then be used directly. It can be used in a home for lights and
appliances. It can be used in a business. Solar energy can be stored in
batteries to light a roadside billboard at night. Or the energy can be
stored in a battery for an emergency roadside cellular telephone when
no telephone wires are around. There
are primarily two types of PV systems. Off-grid systems are used in remote
locations where the cost of a PV system is cheaper than thc cost of running
electrical power from the local utility. Grid-connected PV systems that
can feed their excess electricity production back to the grid during the
day, to be applied as a credit against electricity that you use at night.
This effectively spins the electricity meter backwards in what is known
as "net metering." Photovoltaics or solar cells can be purchased in two formats: as a stand-alone system that is attached to your roof or as integrated roofing materials with dual functions that act as a regular roofing shingle and as a solar cell making electricity. Also, because solar reduces the amount of electricity drawn from the grid, solar can offset energy use for Title 24 compliance. Because of state incentives, federal tax credits, and various local programs many people are now considering grid-connected PV systems. These incentives offered to homeowners and small businesses are helping to develop a more robust PV industry in the United States. In addition, growing demand for PV cells, along with competition, is helping drive down the per watt price of PV cells while at the same time creating new jobs in America. Types of PV Panels Monocrystalline Silicon Panels 15-18% efficiency Monocrystalline panels use crystalline silicon produced in large sheets which can be cut to the size of a panel and integrated into the panel as a single large cell. Conducting metal strips are laid over the entire cell to capture electrons in an electrical current. These panels are more expensive to produce than other crystalline panels but have higher efficiency levels and, as a result, are sometimes more cost-effective in the long run. Polycrystalline Silicon Panels 12-14% efficiency Polycrystalline, or multicrystalline, photovoltaics use a series of cells instead of one large cell. These panels are one of the most inexpensive forms of photovoltaics available today though the costs of sawing and producing wafers can be high. Even though they have lower conversion efficiencies than monocrystalline panels, the cost per watt ends up lower because of efficient manufacturing processes. Two Primary Manufacturing Methods are: Cast Polysilicon - In this process, molten silicon is first cast in a large block which, when cooled, is in the form of crystalline silicon and can be sawn across its width to create thin wafers to be used in photovoltaic cells. These cells are then assembled in a panel. Conducting metal strips are then laid over the cells, connecting them to each other and forming a continuous electrical current throughout the panel. String Ribbon Silicon - String ribbon photovoltaics use a variation on the polycrystalline production process, using the same molten silicon but slowly drawing a thin strip of crystalline silicon out of the molten form. These strips of photovoltaic material are then assembled in a panel with the same metal conductor strips attaching each strip to the circuit. This technology saves on costs over standard polycrystalline panels as it eliminates the sawing process for producing wafers. Some string ribbon technologies also have higher efficiency levels than other polycrystalline technologies. Amorphous Silicon or Thin Film Panels 5-6% efficiency Thin-film panels are produced very differently from crystalline panels. Instead of molding, drawing or slicing crystalline silicon, the silicon material in these panels has no crystalline structure and can be applied as a film directly on different materials. Variations on this technology use other semiconductor materials like copper indium diselenide (CIS) and cadmium telluride (CdTe). These materials are then connected to the same metal conductor strips used in other technologies, but do not necessarily use the other components typical in photovoltaic panels as they do not require the same level of protection needed for more fragile crystalline cells. The primary advantages of thin-film panels lie in their low manufacturing costs and versatility. Because amorphous silicon and similar semiconductors do not depend on the long, expensive process of creating silicon crystals, they can be produced much more quickly and efficiently. As they do not need the additional components used in crystalline cells, costs can be reduced further. Because they can be applied in thin layers to different materials, it is also possible to make flexible solar cells. However, thin-film panels have several significant drawbacks. What they gain in cost savings, they lose in efficiency, resulting in the lowest efficiency of any current photovoltaic technology. Thin-film technologies also depend on silicon with high levels of impurities. This can cause a drop in efficiency within a shorter period of time. Thin-film panels have the potential to grow in use, and already figure in some of the most exciting enhanced photovoltaic systems, including high-efficiency multijunction devices and building integrated photovoltaics.
An estimated one million residential and 200,000 commercial solar water-heating systems have been installed in the United States. Although there are several different types of solar water-heating systems, the basic technology is very simple. Sunlight strikes and heats an "absorber" surface within a "solar collector" and heats the fluid within it. Either a heat-transfer fluid or the actual water to be used flows through tubes attached to the absorber and picks up the heat from it. (Systems with a separate heat-transfer-fluid loop include a heat exchanger that then heats the potable water) The heated water is stored in a separate preheat tank or a conventional water heater tank until needed. If additional heat is needed, it is provided by electricity or fossil-fuel energy by the conventional water-heating system. By reducing the amount of heat that must be provided by conventional water-heating, solar water-heating systems directly substitute renewable energy for conventional energy, reducing the use of electricity or fossil fuels by as much as 80%. Today's solar water-heating systems are well proven and reliable when correctly matched to climate and load. A quality assurance and performance-rating program for solar water-heating systems, instituted by a voluntary association of the solar industry and various consumer groups, makes it easier to select reliable equipment with confidence. Building owners should investigate installing solar hot water-heating systems to reduce energy use. Before sizing a solar system, hot water-use reduction strategies should be put into practice. Types
of Solar Hot Water Systems Thermosiphon Systems. These systems heat water or an antifreeze fluid, such as glycol. The fluid rises by natural convection from collectors to the storage tank, which is placed at a higher level. No pumps are required. In thermosiphon systems fluid movement, and therefore heat transfer, increases with temperature, so these systems are most efficient in areas with high levels of solar radiation. Direct-Circulation Systems. These systems pump water from storage to collectors during sunny hours. Freeze protection is obtained by recirculating hot water from the storage tank, or by flushing the collectors (drain-down). Since the recirculation system increases energy use while emptying reduces the hours of operation, direct-circulation systems are used only in areas where freezing temperatures are infrequent. Drain-Down Systems. These systems are generally indirect water-heating systems. Treated or untreated water is circulated through a closed loop, and heat is transferred to potable water through a heat exchanger. When no solar heat is available, the collector fluid is drained by gravity to avoid freezing and convection loops in which cool collector water reduces the temperature of the stored water. Indirect Water-Heating Systems. In these systems, freeze-protected fluid is circulated through a closed loop and its heat is transferred to potable water through a heat exchanger with 80% to 90% efficiency. The most commonly used fluids for freeze protection are water-ethylene glycol solutions and water-propylene glycol solutions. Types
of Collectors Flat-plate collector, the most common type, is an insulated, weatherproofed box containing a dark absorber plate under one or more transparent or translucent covers. Evacuated-tube collectors are made up of rows of parallel, transparent glass tubes. Each tube consists of a glass outer tube and an inner tube, or absorber, covered with a selective coating that absorbs solar energy well but inhibits radiative heat loss. The air is withdrawn (evacuated) from the space between the tubes to form a vacuum, which eliminates conductive and convective heat loss. The vacuum also helps them achieve extremely high temperatures (170°-350° F); so they are appropriate for commercial and industrial uses as well as residential. Concentrating collectors are usually parabolic troughs that use mirrored surfaces to concentrate the sun's energy on an absorber tube (called a receiver) containing a heat-transfer fluid. They provide hot water and steam, usually for industrial and commercial applications. Polypropylene Plastic collectors are used for non-potable water applications such as pools, hot tubs and radiant flooring. These panels are very cost effective, with payback in as little as 2 years
We can trace all energy used on our planet back to the source...the nearest star, our sun. The history of solar energy is as old as humankind. In the last two centuries, we started using Sun's energy directly to make electricity. In 1839, Alexandre Edmond Becquerel discovered that certain materials produced small amounts of electric current when exposed to light. William Grylls Adams, who, with his student, Richard Evans Day, discovered in 1876 that a solid material - selenium - produced electricity when exposed to light. Selenium photovoltaic cells were converting light to electricity at 1 to 2 percent efficiency. Photovoltaic, or PV for short, is the word that describes converting sunlight into electricity: photo, meaning pertaining to light, and voltaic meaning producing voltage. It took, more than 100 years, however, for the concept of electricity from sunlight to become more than just an experiment. Birth
of the PV Cell By the mid-1960s, efficiency levels were nearing 10 percent. As an outgrowth of the space exploration in the 1960s-70s, PV development increased dramatically. Meanwhile, world wide hostilities and the threat of war turned the world more and more away from oil and toward renewable energy. 1970s
& 1980s The Energy Tax Act (ETA) of 1978 (Public Law 9-618) was passed by Congress in response to the energy crises of the 1970's - the Arab Oil Embargo and the taking of U.S. hostages in Iran. The act encouraged homeowners to invest in energy conservation and solar and wind technologies through tax credits. A federal energy tax credit of up to $2,000 was given for devices installed on people's homes on or after April 20, 1977 and before January 1, 1986. Solar space and water heating carried a 40% tax credit, while weatherization, insulation, and similar conservation activities carried a 15% tax credit. However, the incentives were phased-out in the mid-80's as a result of Reagan administration policies. The federal tax credits, however, spurred the creation of new utility-scale solar and wind electricity systems. Wind turbines sprouted on California's windiest hillsides, and companies began investing in solar technologies. In 1979, ARCO Solar began construction of the world's largest PV manufacturing facility in Camarillo, California. ARCO Solar was the first company to produce more than 1 megawatt (MW) of PV modules in one year. Four years later, ARCO Solar dedicated a 6 megawatt PV facility in Central California in the Carrissa Plain. The 120-acre unmanned facility supplied the Pacific Gas and Electric Company utility grid with enough power for about 2,500 homes. ARCO Solar also built a 1 MW PV power plant with modules on over 108 double-axis trackers in Hesperia, California. Solar One began the first test of a large-scale thermal solar tower, power plant. Solar One was designed by the Department of Energy (DOE), Southern California Edison, Los Angeles Department of Water and Power, and the California Energy Commission. It was located in Daggett, California, which is about 10 miles east of Barstow. Solar One's method of collecting power was based on concentrating the sun's energy to produce heat and run a generator. A total of 1818 mirrors, or heliostats, would track the sun across the sky and reflect the sun's light to the top of a large tower. A black-colored receiver, on top of the tower, transferred the heat to an oil heat-transfer fluid. The heated oil was then used to boil water, which turned turbines and generators. Solar One produced 10 MW of electricity. It was completed in 1981 and produced power from 1982 to 1986. In 1984, the Sacramento Municipal Utility District dedicated a 1.0 MW photovoltaic power plant to operate near the Rancho Seco Nuclear Power Plant south of Sacramento. That was later expanded to two megawatts. In 1986, the world's largest solar thermal electricity facility began to be built in California's Mojave Desert. The LUZ Solar Energy Generating Stations (or LUZ-SEGS) contains rows of mirrors that concentrate the sun's energy onto a system of pipes circulating a heat-transfer fluid. The heated transfer fluid is used to produce steam, which powers a conventional turbine to generate electricity. All told, more than 300 megawatts of solar thermal electricity were built before the company had financial difficulties and was sold. They are still producing power today, 20 years later! 1990s
to 2006 1996, the U.S. Department of Energy and an industry consortium begin operating Solar Two - an upgrade of the Solar One concentrating solar power tower. Until the project's end in 1999, Solar Two demonstrated how solar energy can be stored efficiently and economically so power is produced even when the sun isn't shining; it also spurred commercial interest in power towers. Another and more important event also occurred in 1996. Assembly Bill 1890 (Statues of 1996, Chapter 854, Brulte) was passed by the Legislature and signed by Governor Pete Wilson. This bill deregulated the state's investor-owned electric utilities and created incentives for grid-tied PV systems under the California Energy Commission's Renewable Energy Program. The following year, Senate Bill 90 (Statues of 1997, Chapter 905, Sher) implemented the provisions of AB 1890 and directed the activities of the Energy Commission relating to renewable energy. The primary goal of this program is to develop a self-sustaining market for "emerging" renewable energy technologies in distributed generation applications. The Emerging Renewables Program (formerly called the "Emerging Renewables Buydown Program") was created to stimulate market demand for renewable energy systems that meet certain eligibility requirements by offering rebates to reduce (buy-down) the initial cost of the system to the customer. For systems larger than 30 kilowatts, the California Public Utilities Commission directed the investor-owned utility companies - Pacific Gas and Electric, San Diego Gas & Electric, Southern California Edison, and Bear Valley Electric - to work with businesses, governments and schools to install PV "self-generation" systems. In the ten years since 1996, more than 150 megawatts of electricity was installed through both the Energy Commission and the CPUC's programs. Nationally, the "Million Solar Roofs" program begun by President Bill Clinton in 1997, had supported the installation of 70,000 PV systems by the end of 1999. In 2000, Senate Bill 1345 (Statutes of 2000, Chapter 537, Peace) directed the Energy Commission to develop and administer a grant program to support the purchase and installation of solar energy and selected small distributed generation systems. Solar energy systems include solar energy conversion to produce hot water, swimming pool heating, and battery backup for photovoltaic (PV) applications. Funding for the program had to be renewed annually by the Legislature. The state's budget crisis essentially ended the program. In September 2000, the legislature adopted the Reliable Electricity Service Investments Act (RESIA) as the result of legislation: Assembly Bill 995 (AB 995, Statutes of 2000, Chapter 1051, Wright) and Senate Bill 1194 (SB 1194, Statues of 2000, Chapter 1050, Sher). These two pieces of legislation mandated the three investor-owned utilities to collect $135 million annually for 10 years beginning in 2002 to support the Energy Commission's Renewable Energy Program. In 2001, during the height of the electricity crisis, Senate Bill 17xx - created a solar tax credit retroactive to January 2001. The tax credit, for tax years 2001-2003, was equal to the lesser of 15 percent of the net purchase cost of a photovoltaic or wind-driven system with a generating capacity of not more than 200 kilowatts. The Bill allowed credit for one system per each separate legal parcel of property or per each address of the taxpayer in California and required recapture of the credit if the system is sold or removed from California within one year. The credit was reduced to half that amount for tax years 2004-2005 and ended on January 1, 2006. Qualifying systems needed to be certified by the Energy Commission, installed with a five-year warranty, and would be required to be in service in California for at least one year. This bill complemented other programs that provided incentives for installing renewable systems. Assembly Bill 29x in 2001 provided more funding to both investor-owned and municipal utility customers in the Energy Commission's Emerging Renewables Buy-Down Program. The additional funding came from state tax dollars (as opposed to ratepayer or "public goods charge" funding used by the deregulation bills). AB 29x also established a Renewable Energy Loan Guarantee Program, set up by the Technology, Trade and Commerce State Agency for larger renewable energy projects. Senate
Bill 103 (SB 1038, Statutes of 2002, Chapter 515, Sher), signed in September
2002, incorporated the "RESIA Investment Plan" with changes.
The bill directed the Energy Commission on how to implement the Renewable
Energy Program from 2002 through 2006. By 2006, the estimated yearly solar cell production reached 1,868 megawatts, and California made international news with the California Solar Initiative. Solar makes up only a small fraction of current electricity production and is expected to continue growing at an accelerated rate as technologies improve and its use becomes more widely accepted.
Net Metering WorksWhat
is Net Metering? Am
I Eligible? How
does Net Metering work? A Net Metering agreement allows you to use the electricity you generate first, reducing what you would normally buy from your utility or ESP. If you generate more electricity than you use, the excess goes through your electric meter and into the grid, spinning your meter backward. Your meter shows the net amount, measured as the difference between the electricity you generate and the electricity you purchase from your utility or ESP. What
are the benefits of Net Metering? Another benefit of Net Metering is the "baseline" rate you are charged for the net electricity you consume. The baseline is a given amount of electricity for your home or business; you are charged a lower rate for each kilowatt-hour of electricity you consume below the baseline, and a higher rate above it. If your system is sized to offset most of your electricity needs, you are charged a lower rate for the minimal electricity you purchase from your utility if your annual net consumption falls at or below baseline. Net Metering offers additional benefits, depending on the size of your generating system. If you purchase a smaller, less expensive system, you can still offset most or all of your electricity needs because of the higher value of your excess electricity. If you purchase a larger system, you can "bank" or store your excess electricity on the grid and offset all of the electricity you would otherwise purchase from your utility or ESP. How
will I be billed under Net Metering? On the anniversary of your agreement, you will be billed for the net electricity you consumed for the previous twelve months. You may request the option of monthly billing. Depending on the type of agreement you have, your meter might show a credit during some or all billing periods, even though the actual kilowatt-hours you generate and consume are equal. Your utility is not required to pay you or credit your account for your excess generation each year, but it might do so. Contact your utility or ESP to discuss the option of negotiating rates for purchasing excess generation. If your current utility or ESP does not purchase excess electricity, you may contract with another company that will agree to purchase it. What
size should my generating system be? Can
I use my current electric meter? How
do I sign up? When
connecting the system to your grid, your LDC cannot:
Q - If my generating system produces more electricity than I need, is my utility or ESP required to buy it from me? A Utilities or ESPs may, but are not required to, purchase any excess electricity you produce at the end of each year of your net metering agreement. State law says that they do not have to buy your net generation. However, some ESPs, especially those specializing in selling "green" electricity, may be willing to buy your excess solar or wind electricity to re-sell to their other customers. Q Will I have to pay for special meters, inspections or fees to get my system hooked up to the grid? A You are only responsible for having a simple, bi-directional meter, the type you probably already have, unless you decide to purchase a time-of-use meter. If your generating system meets national safety and performance standards, you cannot be charged for additional tests, certifications or fees. Q Will the electricity I might still need to buy from a utility or ESP cost me more than before I became a Net Metered customer? A No, your utility or ESP cannot charge you more for electricity because you are a Net-Metered customer, and no charges can be imposed on the electricity you generate.
1. If my generating system produces more electricity than I need, my electric service provider (ESP) must buy it from me. Wrong: ESPs may, but are not required to, purchase any excess electricity you produce at the end of each year of your net metering agreement. State law specifically states that your ESP does not have to buy your net generation. However, some ESPs, especially those specializing in selling "green" electricity, may be willing to buy your excess solar or wind electricity for resale to their other customers. 2. My electric service provider will pay me full retail rates for my excess electricity. Wrong: If they are willing to buy this "net" annual generation, they do not have to pay you full retail prices for it. While the actual rate paid would be up to the ESP, it would likely be less than retail and closer to "wholesale" rates, which are much lower. 3. I will have to spend hundreds of dollars on special meters, inspections or fees to get my system hooked up to the electric grid. Wrong: You are only responsible for having a simple, bi-directional meter, the type you probably already have. If your generating system meets national safety and performance standards, you cannot be charged for additional tests, certification or fees. 4. The kilowatt-hours of electricity I might still need to buy from an ESP will cost me more than before I became a net metered customer. Wrong: Your ESP cannot charge you anything extra for being a net metered customer and no charges can be imposed on the electricity you generate.
Most
electricity customers are not aware that, as a result of deregulation
of utilities here in California, their old electric utility no longer
exists. It has now been replaced by two companies to bring them electricity,
an "electric service provider" or "ESP" and a "local
distribution company" or "LDC." This change is similar
to the deregulation of telephone services twenty years ago. That deregulation
meant that the company that sells you long distance telephone service
may now be a different company from the company that maintains and owns
the telephone wires into your home. This is now the same case for electricity,
where the company that supplies the electricity that you purchase, your
"ESP," may be a different company than the one that owns and
maintains the power lines to your house, which is your "LDC."
Your old utility company is most likely still your LDC and may also be
your ESP, unless you have chosen to buy your electricity from one of the
many new electric service providers that have been formed to market electricity.
With net metering, the metering arrangement is with your ESP, while the
details of how your generating system must be safely connected to the
electrical grid is handled by your LDC. |
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