Renewable Energy

In affordable housing, the most practical renewable energy strategy is to capture solar energy for electricity generation or water heating.

Active solar design strategies should be taken up only after passive solar and comprehensive energy efficiency and load reduction approaches have been incorporated, since active systems are typically more costly. Solar water heaters are the most common type of active solar system in affordable housing. Typically, they are mounted on south-facing rooftops and are connected to a gas-fired boiler, with solar used for preheating water.

Photovoltaic (PV) or solar cells convert sunlight directly into electricity. In rental developments, photovoltaic systems are most commonly sized to offset the electricity attributed to the "house meter"—for office and community room; corridor safety lighting; exterior building, parking lot, and landscape lighting; and garage exhaust fans. For a fifty-unit rental development, a PV system designed to provide all the annual electric needs of the common area would likely have a size of 25 to 70 kilowatts (kW), or eight to twenty-five times what is typical for a single-family house. Less common are projects that include PV systems that offset the electricity use of the individual dwelling units. One example of a project that powers both common areas and the dwelling units is the Solara in Poway, California, which also meets the California Energy Commission's zero-energy criteria. Other projects are preparing for future PV or hot-water systems by installing conduit and plumbing during construction to enable easy installation at a later date. PV installations in home ownership projects are usually 1.5 to 5 kW, which can offset 40 to 90 percent of electricity use, depending on home size and the occupant's energy use. While the cost of PV systems often appears to be prohibitive, state rebate programs, federal tax credits, innovative financing (such as including the cost of the PV system in the mortgage for the house or leasing the system), and anticipated increases in energy costs can make these systems a cost-effective investment for owners with a ten-year or longer time horizon.

FIGURE 3.11. Installation of photovoltaic panels on the Nuevo Amenecer Apartments in Pajaro, CA.

Photo courtesy of Pamela Cepe

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