Almost all energy we use comes originally from the sun. Fossil fuels are plant and animal matter that decayed tens of millions of years ago and have been compressed and heated, turning into coal, oil, and gases. Of course, plants get energy from the sun and convert it through photosynthesis. Animals in turn eat plants, converting the stored energy into energy to keep themselves alive.
Wind is created because of differential heating of land and water areas by the sun, creating movement of air from one area to another. Geothermal energy is residual heat of the earth, which was created billions of years ago in the formation of the solar system. So, we can trace all energy back to the source…the nearest star, our sun.
But the Sun’s energy can also be used directly…
In 1839, Edmond Becquerel discovered that certain materials produced small amounts of electric current when exposed to light. Not long after that, selenium photovoltaic cells were converting light to electricity at 1 to 2 percent efficiency. In 1954, D.M. Chapin, C.S. Fuller and G.L. Pearson, of Bell Laboratory, patented a way of making electricity directly from sunlight using silicon-based solar cells. The next year, the Hoffman Electronics-Semiconductor Division announced the first commercial photo voltaic product that was 2.0-percent efficient, priced at $25 per cell, at 14 milliwatts each, or $1,785 per watt (in 1955 dollars). By the mid-1960s, efficiency levels were nearing 10 percent.
We call modern-day devices that convert sunlight into energy photovoltaic cells, or “PVs” for short. More commonly, they’re known as solar cells. We can find them on calculators, hats, sidewalk lighting systems, and alongside freeways to power phones for stranded motorists.
As an outgrowth of the space exploration and following the energy crises of the 1970s, PV development increased. 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 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.
When large collections of PV panels or modules are put together, they can be tied into the electricity grid system. These can supply additional power to areas that need electricity, but costs for new transmission lines and substations are prohibitive. These type of systems are basically Utility-Scale Applications of Photovoltaics.
PV systems can also be used in homes, whether they are connected to the electricity grid or are in rural or remote locations.
Solar photovoltaic cells are small, square-shaped panel semiconductors manufactured in thin film layers from silicon and other conductive materials. When sunlight strikes the PV cell, chemical reactions release electrons, generating electric current. The small current from individual PV cells, which are installed in modules, power individual homes and businesses, or can be plugged into the bulk electricity grid.
Solar PV has come a long way since its early origins in the space program powering satellites and other extraterrestrial vehicles more than four decades ago. The technology has come down to earth and now is the first power supply choice for much of the developing world. They are also appearing on rooftops and years around our state to provide power during daylight hours.
There are two primary PV markets. Off-grid systems are used where the cost of a PV system is cheaper than stringing electrical power lines long distances from the local utility. Grid-connected PV systems usually cannot compete directly with the cost of utility-produced power. However, with the changing deregulated marketplace, many people are considering grid-connected PV systems. If the PV system provides more power than the home or business uses, additional electricity is fed back into the grid for other people to use. This effectively spins an electricity meter backward in what is known as “net metering.”
Incentives are being offered to homeowners and small businesses by some states to help develop a more robust PV industry. For more about the current incentives and rebates, please visit the Go Solar California! website.
From 1998 to 2006, solar/PV incentives for systems under 30 kilowatts were handled by the California Energy Commission’s Emerging Renewables (Buy-down) Program. Larger systems were funded by the California Public Utilities Commission (CPUC) and the Self-Generation Program with the electric utilities.
From 1998 to October 31, 2006, nearly 175 megawatts of solar electric capacity was installed in California under the two programs.
Beginning January 1, 2007, all solar/PV rebates on existing homes and businesses will all be handled by the electric utilities under the California Solar Initiative at the direction of the CPUC. The Energy Commission will focus on solar on new home construction, along with rebates for small wind and fuel cell electricity systems.
There are many solar PV products on the market.
One of the more intriguing recent advances was just announced by Toshiba for the Graetzel cell, a new type of solar panel that consists primarily of titanium dioxide nano-crystals coated with a dye. The new cells could be manufactured by silk-screen printing technologies. At present, at least seven companies in Japan, Europe, and Australia are developing improved Graetzel cells that may end up gracing cell phones, laptops, and even windows in energy-efficient homes.
BP Solar panels quietly and beautifully transform atria, glass roofs, and roof lights into electricity generators. The most impressive products, nevertheless, are PowerWalls, which arrange solar cells in patterns framed by curtain walls erected with traditional glazing techniques.
Powerlight Corporation of Berkeley, California, has developed a unique mounting platform that integrates a variety of PV products into rooftops. A foam insulation reduces heating and air-conditioning costs. The light-weight solar PV modules also extend the life of the roof by protecting it from the damaging effects of weather.
The building-integrated products manufactured by Atlantis Energy of Grass Valley, California, offers custom glass PV laminates, which turn windows into micro-power plants.
The cost of a PV system depends on the system’s size, equipment options, and labor costs. Prices vary depending on other factors as well, such as the PV provider, whether or not your home is new, if the PV is integrated into the roofing materials or mounted on top of the existing roof, and the PV manufacturer. Small systems funded through California’s Buy-Down Program have been averaging $7.00 / watt, after rebates.
The property should have clear, unobstructed access to the sun for most of the day and free from shade. The best orientation for a PV system is on a south-facing roof. If your location looks promising, a PV provider can trace the sun’s path for you and determine whether your home or business would benefit from a PV system. Typically, composition shingle roofs are the easiest to work with.