Green Product Category: Renewable Energy

Renewable energy sources offer environmentally attractive alternatives to fossil fuels and nuclear power. Although no energy system can claim to be 100 percent pollution free, renewables are orders of magnitude better than our conventional energy systems.

The U.S. Department of Energy estimates that the annual influx of accessible renewable resources in the U.S. is more than 200 times the total amount of energy used. Technologies for converting these energy sources into electricity or usable heat are improving in efficiency and dropping in price.

A few strategies, systems, and concerns:

• The simplest way to utilize renewable energy in buildings is with climate-responsive design—passive solar heating in winter, summertime cooling with natural ventilation, and daylighting.
• The field of building-integrated photovoltaics (BIPV) is expanding dramatically, with enormous arrays of PV panels on large, institutional buildings and smaller arrays integrated into individual homes. These typically come in the form of panels that can be wall- or roof-mounted, though PV panels that serve a dual role as glazing and power production are now also available. Solar-domestic hot water systems have quick paybacks in climates where sophisticated freeze-control systems aren’t needed. In colder climates the paybacks are longer, but such systems can still be a very worthwhile investment.
• While large-scale hydroelectric facilities are associated with some significant environmental problems (most notably the displacement of humans and other species, and the interruption of fish migration), carefully sited small-scale hydropower may be a good option.
• The Union of Concerned Scientists estimates that wind power could supply one-fifth of U.S. electricity demand. Small, home-based wind machines range in output from 250 watts to 10 kilowatts (compared to utility-size wind turbines that can produce more than 750 kilowatts of power).
• One issue affecting many renewable energy sources is that their power production varies with the time of day and season. In some cases, the peak production actually matches peak demand—for example, photovoltaic systems generate the most electricity on hot days, when cooling loads are highest. In other cases, different forms of energy storage are needed to match the energy demand with energy production.

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