Solar Energy for County Facilities Many regional utilities offer credit on ener- A dish engine system is essentially an elec- ●●Introduction gy bills for providing the utility with excess tric generator that runs on sunlight. A dish Solar power involves the use of the sun’s electricity from the customer’s solar or other made of glass mirrors collects direct rays of energy to provide electricity, heat, or light. alternative energy electricity system. This light from the sun and concentrates these rays This energy can be harnessed for use in both “net energy metering” can lead to significant in a receiver. The receiver converts it to heat large- and small-scale projects, from a home bill reductions for customers with this tech- and then transfers it to the engine, which uses to a commercial building. According to the nology. it to produce electricity. This is essentially an NACo County Green Programs Survey, electric generator that runs on sunlight. Environmentally, the use of solar energy which was sent to counties nationwide in benefits both land and air quality. Solar pow- June 2008, 14% of the 147 respondents gen- Some concentrating solar systems are com- er does not create greenhouse gas emissions, erate renewable energy. Of this renewable bined with thermal storage capacities to op- nor does it release other toxins into the air. energy, 40% is solar power. erate during nighttime. Others are combined It also replaces the use of fossil fuels with a with natural gas powered generators, so that Sunlight is made of photons, which contain renewable resource. power can be produced on demand if needed. energy. Several technologies have emerged In both cases, the reason is to ensure power to harness this energy including concentrat- ●●Concentrating Solar can be produced on demand even if the sun ing solar power, photovoltaics, solar heating is not shining. and solar lighting, all of which will be ex- Power Systems plained in this fact sheet. By using mirrors or lenses to concentrate Concentrating solar power systems may the rays of the sun, solar thermal systems can also use special photovoltaic cells (see the ●●Costs and Benefits produce temperatures as high as 750 degrees section on Photovoltaic Systems below) de- Fahrenheit. DOE reports that this intense signed for the intense light from the concen- The sun shines daily, serving as a con- heat can produce anywhere from 10 kilo- trator. However, these types of collectors are stant free fuel. The U.S. Department of En- watts to 100 megawatts of electricity. Solar mostly under development and not commer- ergy (DOE) reports that even on extremely concentrators come in three main designs: cially available. overcast days, solar energy systems can still parabolic troughs, power towers, and dish Boulder County, Colorado is working to produce 25% of maximum output, and this engine systems. Arrays of lenses are also oc- identify potential sites for concentrating so- number increases to as much as 80% on days casionally used. lar power plants, as well as finding partners that are only partially cloudy. Due to this to support and demonstrate these projects. abundantly available fuel, solar power can be The parabolic trough uses a curved collec- The county has created a map with possible a cost-effective choice. Note: Regional dif- tor to reflect light onto a pipe running along areas for these plants. The county is also ferences (particularly weather patterns) may the inside of the curved surface. This raises encouraging a company with plants in the make another source of energy more cost ef- the temperature of a heat transfer fluid in the county, Frito Lay, to build 50 acres of solar fective. pipe, which then is used to run a steam gen- erator. Often, these troughs will be combined concentrators to provide renewable fuel. This to create a collector field, which is generally plan would reduce the plant’s electricity con- aligned on a north-south axis, in order to op- sumption by 90% and the use of natural gas timize the sun as it travels across the sky. by 80%. For more information, see the Boul- der County sustainability website, located at According to the Union of Concerned Sci- www.bouldercounty.org/sustain/. entists, a nonprofit organization working for a healthy world, there are currently nine so- lar electric generating stations in California’s Mojave Desert, built from 1985 to 1991. Power towers concentrate sunlight from a very large area on a receiver at the top of a tower. The sunlight is reflected by heliostats, large sun-tracking mirrors that all point the sunlight at the tower. Inside the tower the receiver contains a heat-transfer fluid which then generates steam power to drive turbines, producing electricity. The solar water heating system was in- County Case Study: stalled in the county’s youth center, home Washtenaw County, Michigan to 30 people. Hot water at the facility is Population: 341,847 used for 30 showers daily, laundry, and in County Seat: Ann Arbor the kitchen. The system consists of a flat- plate solar collector and a storage tank. It Washtenaw County, Michigan has a allows the facility to save $500 and 400 photovoltaic and solar hot water heating cubic feet of natural gas each year, as well system in two county facilities. The 10 as to reduce carbon dioxide emissions by kilowatt photovoltaic system, installed at 5,000 annually. the Washtenaw County Western Service Center, generates enough power for 3% The county also educates the community to 5% of the facility’s energy needs, sav- about solar power. The Washtenaw County ing the county $1,000 to $1,500 annually Western Service Center features a display and reducing carbon dioxide emissions by with information about the county’s solar 16,000 to 24,000 pounds. It was funded by power use, as well as a computer with real a grant from the Energy Office of the State time data about energy production and the ●●Photovoltaic Systems of Michigan. money that using solar power is saving the Photovoltaic systems convert solar energy county. into electricity. The use of these systems in the U.S. is rapidly increasing. Solar Industry Magazine reports that the number of new sys- in remote locations where no utility power is In May 2004, Butte County, California tems in the U.S. approached 13,000 in 2007, available. commissioned Sun Power & Geothermal up 24% from the previous year, bringing the Energy in collaboration with Sharp Electron- A more common solution is to connect cumulative number to over 48,000 locations. ics Corporation, Pacific Gas & Electric, and the photovoltaic system to the utility power Methods of collecting and storing solar en- the California Energy Commission, to install grid with equipment that outputs utility- ergy vary depending on the intended uses. a solar energy system that would double the compatible power, while protecting both the solar energy already produced in the county. Most commercial photovoltaic “cells” (also utility and photovoltaic systems in case of Installation was completed in September called solar cells), are made of silicon, which problems on either side. When the sun does 2004, with a total project cost of just over is a semiconductor, allowing it to absorb not produce sufficient energy for the facil- $8.4 million. some sunlight and convert it into electricity. ity, electricity can come from a local power The silicon in a solar cell is very specially company. In addition, with the company’s The system is comprised of four separate formulated and manufactured so that it will approval, the facility may also be able to sell solar arrays, providing all power for three allow energy to move through it, producing excess power generated by the solar cells to electricity. the power company. Sunlight is made of photons, which contain The typical amount of time that it takes for energy. When these photons hit the photovol- a photovoltaic system to generate the same taic cell, some are absorbed, and the energy amount of energy that it took to create the from the photon is transferred to an electron system is about 2 to 5 years. A well-designed, in an atom in the cell. The electron uses this well-cared-for system can last for 20 or more energy to move around freely, becoming part years, creating a net energy gain. of the electric current. A metal backing and a grid of wires on the front collects the elec- According to the Florida Solar Energy tricity and connects it to the power system. Center, the state’s energy research institute, The photovoltaic cell is also covered with an non-tracking solar arrays (that do not follow anti-reflective coating to prevent loss of pho- the sun’s path) located in the Northern Hemi- tons. Finally, a glass cover plate covers the sphere should face south in order to best col- cell to protect it from the elements. lect sunlight. Additionally, they should be inclined at an angle equal to 90% of their lo- Of course, the sun does not constantly shine cation’s latitude, so as to receive as much en- in one place. One solution for this is to install ergy as possible year-round. They should be deep-cycle batteries to store energy for night- placed away from shade. If even one of the time. These batteries are charged during the cells in the panel is shaded, the production day, and are able to discharge a current for a of power can be reduced by more than 50%. long period of time over the night or cloudy Furthermore, the panels should be designed periods when more electricity is needed.