BUYING GUIDE TO
Solar power is usually divided into two categories. Solar thermal and Photovoltaics (solar electricity). Solar thermal uses the heat from the sun to make heat. Photovoltaics uses the light energy (photons) to make electricity. Solar thermal is used to heat space and water directly. Heat from the sun is collected during the day and stored by thermal mass, i.e. large heavy cement or stone walls, tile floors, water etc. and radiated out into the room at night. The principles of passive solar design can be built into a house in order to reduce the use of commercial heating and cooling.
Passive solar is relatively low tech and uses no extra devices such asmotors and pumps. Domestic hot water systems can be active or passive. A passive hot water system uses convection to circulate the water. An active system will use circulating pumps. Books on passive solar homes are available. Companies that sell hot water systems for household and poolwater are available in every community. Also available are companies that specialize in solar space heating. All these various systems can be very expensive and sophisticated. The consumer needs to know if adding solar space or water heating is cost effective in their situation.
Photovoltaics is a very different technology. Where it is possible for a handy type person to build their own solar collector for hot water a solar electric panel is a product of modern high tech. There are two types of solar panels commercially available at this time. Amorphous silicon and crystalline silicon. Amorphous or thin film panels are about 6% efficient and crystalline silicon is about 14%. Solar panels are wired together to make an array.
There are two main types of solar electric systems. Stand alone and grid connected. A stand alone system is completely independent of the utility grid. These are usually remote home, cabins, house boats, RVs and telecommunications installations. Stand alone systems can either be AC orDC. AC systems are the most common for homes. DC is fine for telecommunications but where one wants to use common appliances of modern life, blenders, washing machines, microwave ovens etc. AC is most cost effective. The main components of a stand alone PV situation is the PV array, battery storage, controls and meters, and the inverter for an AC system plus a back up source of power such as a generator. An inverter is the device that convert DC power to AC.
Grid connected systems are always AC, may or may not use batteries, and need to use a sine wave inverter. However grid connected systems do not need generator back up because the utility grid itself serves. There are two main types of inverter, modified square wave and sine wave. Since commercial power is way less expensive that solar it can take easily 20 years to "payback" the cost of a household grid connected system. There are cost incentives in the works to help pay down the very high cost of grid connected solar systems.
There are many off grid independent solar electric homes in this country. I live in one myself. (And the number of grid connected installations are increasing) There are companies that design and install systems and there are catalogs of components available for folks who want to install there own.
Solar electricity is still very expensive but the technology for stand alone and grid connected photovoltaics is very mature and reliable.
HOW TO SHOP
Educate yourself. Send for catalogs from the many renewable energy companies in the country and read them. You will learn that the equipment is fairly standard and the costs are similar. You can familiarize yourself with the types and sizes of components available. Solar electric components are well made. Solar panels are manufactured by major world corporations who are usually already in the energy business such as British Petroleum. Solar panels have a lifetime of 20 or more years and new ones have good manufacturers guarantees. Most catalogs also contain books on solar electrical and some solar thermal. There are workshops available as well. After you feel fairly confident that you understand this technology, find a local provider who is experienced. If you are going to have a system installed for you, get references and make sure your installer is a licensed electrical contractor experienced in solar electric. Even if you are competent to do you own installation you should have an experienced person local enough to advise you or help you out of a tight spot. If you have questions, feel free to contact me.
Article written by: Cynthia Loweburg, Offline Independent Energy Systems
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