Tuesday Nov 18 2008
Solar power has this family off the grid
By: Janis Dice Gold Country News Service
Editor’s note: This is the second of a two-part series on solar home design. Dick and Becky Myers wanted to do more than just add a few passive solar components to their new home: With the help of expert environmental architect David Wright, they went completely off the grid. “I had a second-grade teacher talk to us about protecting the environment and, even then, it made sense to me,” Becky said recently. “Being energy independent is a challenge Dick and I both wanted to meet.” “I like the feeling of independence,” Dick said. “It’s something we can pass on to our kids.” The Myers searched for land in the foothills with an unobstructed southern orientation to optimize exposure to winter rays. A proper bearing is one of the most basic aspects of any solar project, Wright said. There are two solar strategies – passive and active. A passive approach relies on the predictable flow of heat and air to reach and maintain comfortable temperatures, with little or no mechanical assistance. It optimizes the sun’s energy while using standard construction techniques and taking advantage of natural breezes, shade trees and windbreaks. Active solar systems use fans and pumps to collect, store and distribute heat. Then there are photovoltaic panels that collect solar energy and convert it to electricity. The Myers use it all. Working with the sun to heat and cool their 1,850-square-foot lodge-style abode, the Myers melded their design ideas with Wright’s suggestions of passive and active elements. The passive heating techniques include the home’s concrete slab floors. During the day, they absorb warmth from sunlight pouring through plentiful panes of glass, then slowly release that heat as the house cools at night. The slab, as well as a stone hearth, also retain heat generated from the woodstove. The careful positioning of windows, doors, transoms and operable skylights also are pieces of the passive-solar pie. They provide abundant daylight and are opened to achieve cross-ventilation when cooling is needed. “When the outdoor temperature drops below the inside temperature, you just open the house and let it breathe,” the architect explained. “By morning, it’s nice and cool in there.” On warm days, the glass portals are closed in the early morning, then shuttered or draped to keep heat rays out. In winter, the same shields are used to keep warmed air in. Even the home’s corrugated metal roof is a passive solar aspect. It not only deflects much of the sun’s waves, it also reduces the heat transmitted to the roof: Due to its undulating configuration, little of the material touches the roof, minimizing its heat conductivity. And air blows through the furrows, letting heat escape naturally as it draws cooler breezes across the roof. A deep overhang above the porch shades the outdoor living space in summer. In winter, a portion of the awning is removed to open the concrete patio – and the home’s south-facing portals – to the sun’s warmth. Because they have no back-up electricity supplied by a power company, the Myers opted for some active ingredients, including roof-mounted photovoltaic – or PV – panels. Affixed to the crown of the carport, the rectangular modules directly covert sunlight to electricity. A number of PV cells laid side-by-side form a module; several modules form an array. PV modules generally range from about 5 watts to 300 watts in power output, and produce a direct current. When sunlight strikes a PV cell, an electron is dislodged. The loose electrons are gathered by wires attached to the cell, forming an electrical current. The more cells, the greater the current and voltage produced. According to the California Solar Center, there are more than 25,000 homes in California today that are off-grid and powered primarily by PV arrays. The Myers’ array, installed by Dick, cost about $20,000. The payback on any type of passive or active solar feature varies depending on regional utility rates; local, state or federal incentives; and the users’ level of energy consumption. Where PV users have access to electric grids, they even can recoup costs by selling excess electricity back to the power company. The power generated by the units is stored in batteries that run the home’s lights, small appliances and electronics. During a stretch of cloudy days – or when they have battery storage problems – the Myers use a back-up generator to supplement the PV system. Propane connects directly to the range top, clothes dryer, back-up domestic water heater, radiant floor water heater, back-up generator and the barbecue, Dick said. When in use, the generator can power everything, including charging the PV batteries. The Myers’ propane bills averaged $26 per month last year. “We try to run things during the time of day when solar-generated power is highest,” Becky said. “On a cloudy day, you might just wait to do laundry until the sun comes out again.” That’s a small price to pay for living off the grid. Signed into law on Oct. 3, 2008, the U.S. House and Senate passed legislation that will increase the use of solar energy across America. Renewable energy provisions in H.R.1424 include an eight-year extension of the 30 percent solar tax credit and removal of the monetary cap for residential solar electric installations. For more information, visit the American Solar Energy Society Web site at ASES.org. Other resources: californiasolarcenter.org; .pge.com/cs. To check for solar energy rebates or incentives in your area, contact your local power supplier or check online community bulletins.