1 What are renewable energy systems? What do they do?
Different types of renewable energy systems perform different functions. For example:
• Photovoltaics (PV) convert sunlight directly into electricity using PV cells made of semiconductor material.
• Concentrating Solar Power (CSP) systems concentrate the sun’s energy using reflective devices, such as troughs or mirror panels, to produce heat that is used for industrial processes or to generate electricity.
• Solar water heating systems heat water, either directly or by heating a “working fluid” that then heats the water. Solar water heaters are commonly used to heat domestic water in homes; heat water for swimming pools, spas and hot tubs (a particularly cost-effective application); or to heat water for industrial processes.
• Transpired solar collectors use solar energy to preheat ventilation air.
• Passive solar energy designs use the building itself as both the solar collector and storage medium, usually by increasing the window area on the south side of the building and the amount of thermal mass inside the building to absorb the solar heat that enters through the windows.
• Daylighting systems provide light during the day, significantly reducing the cost of, and heat gain from, electric lighting.
• Wind turbines use the wind’s energy to generate electricity.
• Bioenergy—the energy from biomass (organic matter)—can be used directly for heat or to power a generator to produce electricity. Biomass can also be chemically converted into a fuel oil or liquid fuels.
• Geothermal energy can be used to generate electricity, heat water and heat and cool buildings.
• Hydropower captures the energy in flowing water and uses it to generate electricity.
• Ocean energycan be used as either thermal energy or the mechanical energy of tides and waves.
2 What are the benefits of renewable energy systems?
Renewable energy sources are clean and inexhaustible. The money spent on renewable energy installations tends to remain in the community, creating jobs and fueling local economies. The use of renewable energy equipment also reduces our dependence on foreign and/or centralized sources of energy, and is an important strategy in the process of creating a truly secure and sustainable energy future.
3 Can I use solar for my home or business? How do I know if I have enough sun?
Most places have enough solar energy to meet some or all of their needs with solar energy systems. You can get more specific information by contacting a local solar system designer, installer, solar architect or builder to discuss your power requirements, particulars of your property, what type of systems would suit your needs, sunlight availability, etc. In general, solar energy systems produce energy even under cloudy skies (although less than under full sunlight).
4 I’m interested in having a solar energy system installed on my home or business. Where do I start?
Increasing the energy-efficiency of your building, lights and appliances is always the most cost-effective first step in this process. Look for experienced local solar energy system designers and installers, and check their references as you would any other contractor. If you’re lucky, you can find solar companies listed in your local phone book.
5 Can I use solar electricity to heat water or to heat my house or office?
It is impractical to use solar-generated electricity to heat water—a solar water heating system is a far more cost-effective choice. Similarly, space heating is best accomplished with solar thermal strategies or equipment designed for the
task—passive solar designs or transpired
collectors, for example.
6 How much can I expect to pay for a renewable energy system? How much will it save me on my utility bill?
Your savings will be specific to your circumstances. If you’re lucky enough to live in a state with generous incentives and good solar resources, the economics of installing solar systems may be quite attractive. Solar water heating can be cost-effective nearly anywhere in the U.S. compared with heating water with electricity. If you’re building new, a carefully thought out, energy-efficient and passive solar design costs little extra to build and pays large dividends in energy cost savings over the life of the building. There are also many inexpensive strategies that can save energy and money in renovated buildings. Like any other major purchase, you have to weigh all the costs and benefits. Renewable energy systems offer many benefits unrelated to cost (clean, quiet operation, low environmental impact, energy independence, etc.) and many people choose them even if they are more expensive.
7 What is the energy payback time for PV?
Typically, the energy payback time (the time it takes the system to generate the same amount of energy that it took to manufacture the system) for PV systems is two to five years. Given that a well-designed and maintained PV system will operate for more than 20 years, and a system with no moving parts will operate for close to 30 years, PV systems produce far more energy over their lives than is used in their manufacture.