Photovoltaic Systems Rio Rancho NM
Internship - Off Grid Solar Energy System
Internship - Off Grid Solar Energy System
The man from the power company had to agree: The site Fred Todd and his wife, Ann Pistell, had chosen for their new home in Maine was a splendid one. But to bring in power from the road would take 12 poles - at $1,000 each. As for laying the cables underground -- which the easement for the lot required - well, the cost for that was anyone's guess. Even $50,000 might not cover it. The figures spoke for themselves. For Pistell and Todd it was no longer a question of whether they should go off the grid; the question now was how they could do it and still enjoy the conveniences and comforts of modern living.
That was almost three years ago. Today their home's 22 photovoltaic (PV) panels, generating 1,650 watts of peak power, provide the family of four - including two teenage daughters equipped with blow dryers - with power to spare for 10 months of the year. (In December and January, when cloudy skies and clinging snow are commonplace, they turn to a gasoline-powered generator to make up the shortfall.) As Pistell and Todd see it, their new life hasn't required them to make any sacrifices, but it has required them to be more disciplined in the way they use energy. The PV panels on the roof of their home convert sunlight into electricity - power that is produced using no moving parts, consuming no conventional fuels, and creating no pollution.
The use of PV-generated power is growing. Shipments of PV modules and cells by American manufacturers reached a record level of 77,000 peak kilowatts in 1999, up 52 percent from 1998 - the fourteenth consecutive annual increase in shipments. The boom is being driven largely by need, much of it in developing countries where hundreds of thousands of villages have no connection to power lines and no easy access to expensive diesel generators. In these areas, PV power often is introduced first to pump water and later to power community centers and clinics. But choice, not just necessity, is also fueling demand.
In the United States and much of the Western world, PV users range from billionaires with vacation homes on remote islands to back-to-the-landers and others who live far enough from power lines to make tying into the grid impractical. Some users have an independent streak and want nothing to do with power companies. Still others need backup power for use in the event of a blackout; they often install small systems with just enough generating capacity to provide essential power during time off the grid. PV panels consist of individual solar cells that generate direct current (DC). This power can drive DC-operated appliances, such as those found on boats and in travel trailers, or it can be passed through an inverter that changes it into the alternating current (AC) that powers conventional appliances. Most solar homes use both types of appliances. Available DC appliances include refrigerators, lights, fans, timers, water pumps, televisions and radios.
Ann and Fred's refrigerator runs on DC current. The rest of their appliances run on AC, even though some power is lost when the current passes through an inverter. PV systems can eliminate the need to connect to the grid, but freedom comes at a price. Stand-alone systems require banks of batteries to store power for use at night or during low-light periods. That means they cost more and require more maintenance. In addition, the batteries eventually wear out and need to be replaced. But most American PV users don't leave the grid entirely, choosing instead to draw conventional power when it's needed. When the panels generate more power than the home needs, the excess is fed to the utilities, which either buy it at wholesale rates or reverse the home's meter, depending on the laws of the state.
Peter Talmage, a Maine-based engineer and PV specialist, has a system that will power his home even through the dead of winter. On long summer days, it frequently generates several times more power than his family uses. By selling the excess to the power company, Talmage not only enjoys an economic benefit but the satisfaction that he is making an environmental contribution as well . "The more pollution-free kilowatt hours I feed into the system, the less pollution-encumbered kilowatt hours (the power companies) need to generate," he says. Another plus for PV, says Talmage, is that nearly every system produces more power than its owner needs during the summer, the time of year when air conditioning and refrigeration "force utilities to run every dirty generator they have to keep up with demand." Talmage sees each rooftop in the United States as a potential generating site feeding power into the national grid - an ideal situation in which homeowners would become the country's primary producers of pollution-free electricity. The result would be less pollution, lower costs, stable prices and increased reliability. But that ideal situation also carries a cost, at least for now.
Depending on its complexity, a PV system costs from $5 to $20 per watt of generating power. An average system producing 100KWH of power a month in a northern state like Maine costs about $8,000 installed. Over its effective life of 30 years, such a system generates electricity at 24 cents per KWH. That's twice the current cost of electricity in many states. But, Talmage asks, how much will electricity cost in 30 years, or even three? While a PV system will continue to generate power at 24 cents per KWH, the cost of utility-generated power could rise far higher. At the height of California's rolling blackouts earlier this year, the state was paying as much as 20 cents per wholesale KWH, and only state laws prevented consumers from being hit with charges well above that. New power plants now under construction should produce enough electricity to meet California's needs within three years. But demand for electricity is sure to continue upward. And some studies suggest that lagging construction of new transmission lines could soon create bottlenecks in the supply of power to other regions of the country - further raising pressure on prices. California's searing experience with power shortages has created a surge of interest in photovoltaics there. "Demand has taken off," says Talmage. How do you know if a PV system is right for your home? The first and most basic question you need to answer is whether your site has enough potential exposure to sunlight. During winter the panels need to be in sunlight from about 9 a.m. to 3 p.m. - difficult given the sun's low angle. Removing or trimming trees may be necessary.
PV systems that are tied to the grid need little maintenance beyond keeping panels free of snow and checking connections every few months. Stand-alone systems, on the other hand, require a committed homeowner. Batteries must be checked and serviced, and are likely to need replacement within the lifespan of your system. "If you're not prepared to do the maintenance," says Fred Todd, "you might as well forget about it." Todd notes, however, that the future holds promise of simpler times. Courses on understanding PV, are increasingly being offered to electricians by vocational schools so that "getting your system serviced could soon be as simple as calling up the local electrician." Before you make any decisions about photovoltaic systems, you need to thoroughly examine your household power use and ask whether you could do more to conserve. Why spend $20,000 on a system when adopting better conservation measure would allow you to get by with a system that costs half as much? In fact, conservation is important for those with PV systems. In the Todd/Pistell home, for instance, the water heater is powered by propane, as is the cook stove. All electrical appliances have the highest efficiency rating available. The super-insulated refrigerator uses one quarter the energy of a conventional refrigerator, and the washing machine and dishwasher come close to duplicating that feat while using much less water. Turning off lights and other electrical devices when not needed is mandatory. "When we moved here, our daughters said they could not give up their blow dryers," says Ann Pistell. "So we said, OK, but only if you toe the line with every other form of efficiency. Thy have, and they've done well." Fred Todd plugs interconnected items like the computer, printer and scanner into a single power strip. That way, he says, "it's a simple thing to turn them all off with one flip of the switch." Using a PV system gives homeowners new awareness of how power-hungry devices can be. "Never underestimate the amount of power used by appliances during sleep mode," notes Todd. For instance, a plug-in flashlight draws 5 watts an hour; over a year it adds 44 KWH to a home's annual consumption. A computer in sleep mode can draw 20 to 30 watts an hour.
All told, the sleep mode of appliances in the average US home contributes 14 percent to the monthly bill. An unexpected sight in the basement of the Todd/Pistell home is the water tank. Like rural families everywhere, they depend on their well for water, but the storage tank is twice the normal size used by a family. That's because the biggest amount of power consumed by the pump is at the moment it turns on. Once the water is flowing, power consumption drops considerably. "By having the larger tank, the pump cycles on and off only half as frequently," Todd says. As the seasons change, so do energy consumption patterns. Todd notes, for instance, that the family's power-hungry microwave sits unused all winter, when home-generated electricity is at a premium. Come summer, "When the solar panels are turning out more power than we use and the batteries can store, the microwave is about the only thing we cook with,' he says. Talmage follows the same approach. Even though he's tied to the grid and can "sell" every extra watt produced, he uses an electric power mower on his lawns. "Lawns only grow when I have power to burn," he grins, "and I don't pollute the air around my house." Like Todd, Talmage uses energy efficient fluorescent lighting throughout the house. Fluorescents use one quarter the energy of incandescent bulbs. If just one incandescent bulb were replaced with a fluorescent in every home in California, it would eliminate the need to build one medium-sized power plant. How effective is all this attention to conservation? The average American home consumes about 600 kWH of electricity each month. Investing $5,000 in high efficiency appliances and lighting can cut that consumption in half.
Todd and Pistell, in fact, consume an average of just 160 kWH a month. The payback from such measures is so great, says Talmage, that more than one potential client for a PV system has dropped the idea "when he found out how much he could trim his electrical bill simply by investing in conservation." For their part, Pistell and Todd are debating how to boost their system so that it will carry them through the dark days of winter without resorting to the generator. Two more solar panels would do it, but also supply far more power than they would ever use in summer. An alternative might be to add a small wind generator, since the wind blows with more vigor and consistency in Maine when solar light is at its lowest. But it's clear that PV has the greatest appeal. Says Pistell: "The sun shines on the roof and the refrigerator purrs in the kitchen."