Saturday, April 18, 2009

Solar Electricity


Put a power plant on your roof

Solar electric systems convert the sun's inexhaustible energy into electricity that can power our buildings. These systems, which are also called photovoltaic (PV) systems, have been around for decades--remember those nifty solar-powered pocket calculators? But their acceptance as home-energy systems has been slow because of their high upfront cost.

Attitudes are changing, however. With concern mounting about carbon dioxide emissions, rising energy costs, and dependence on imported fossil fuels grows, having a power plant on the roof sounds awfully attractive. In fact, after tuning up your house to make it as energy efficient as possible, PV is one of the most powerful steps you can take to green your home.
Watch SCGH's Jennifer Schwab interview Scott Perry and tour his home with installed solar panels.

Top Tips

At home

  • Look for free ways to use the sun's energy. A PV system is a big-ticket purchase, so before taking the plunge look for free ways to capture the sun's energy, like passive solar design, daylighting, or a good old-fashioned clothesline.

  • Invest in conservation. For starters, that means installing more insulation, swapping out energy-guzzling appliances for super-efficient models, sealing air leaks, and replacing incandescent bulbs with fluorescents. It also means changing habits: turning off lights and gadgets when you're not using them, lowering the heat, skipping the air conditioning except on the hottest days, or piling on an extra comforter instead of switching on an electric blanket. If you do all that first, you won't have to invest as much in PV to bring your electricity bill under control.

  • Reach for the sky. Even if a PV system only offsets a portion of your electricity use, you're doing something good for the Earth and bringing your energy costs under control. But if you're ready to set really high goals, shoot for a zero-energy home. That means generating as much energy as you use over the course of a year. To do that, you'll first need to get your energy use as low as possible (hang out on this site and you'll become an expert in how to do that), and then produce the rest with renewable energy systems.

  • Check out your site. PV modules need south-facing exposure that's not shaded by trees, buildings, or other structures. They can be installed on sloped or flat roofs, as long as there's unshaded south-facing exposure. But it doesn't have to be on the roof. PV modules can be mounted on the ground, on walls, on window overhangs, and even on trellises where they can do double duty by shading your patio table. On the ground, you can even use tracking devices that tilt the panels in response to the position of the sun. These trackers can increase output by as much as 25%, but they also increase the system's cost, and--by adding moving parts with electronic controls--they may decrease the system's reliability. If you need more power, it may be more cost effective to add a few more panels instead of trackers.

  • Buy green. PV has a lot going for it, but it's not the solution for everyone. If your property gets too much shade, or if a PV system is out of your price range, you can buy green power instead of generating it. Check out the U.S. Department of Energy's Green Power Network website to find out about green power options in your state.

  • Think ahead. If you're building a new house or doing a major remodel, think solar. That means orienting the house or the addition so there's plenty of unshaded, south-facing roof space for PV. If you can't squeeze a PV system into your construction budget, at least plan for where it can be installed in the future and run conduit (without the actual wiring) from that area to the utility meter. This will make it less expensive and less disruptive to install PV later.

When shopping, look for

  • A system that's the right size. Typical residential sizes are between 2 and 4 kilowatts. (One kW equals 1,000 watts--the amount of power needed to keep ten 100-watt light bulbs burning.) How large a system you need depends on how much electricity your household uses, what portion of that demand you want to offset with the PV system, and how much unshaded south-facing space you have available. Solar companies can usually estimate system size over the phone, after asking about your current electricity use and looking at your property on a satellite map to check out shading issues. If your property looks feasible for solar, they'll come to your house and do a detailed analysis.

  • Payback. A reputable PV system designer or installer can calculate how long it would take for your energy savings to pay for the upfront costs of the system; they'll run the numbers for free as part of their sales proposal if they've determined that PV is feasible for your site. Typically you'll pay $15,000 to $30,000 for a system, and in 15 to 30 years or so you'll reach the break-even point. If energy costs keep rising or you qualify for any rebates, you'll get your payback quicker.

  • Financing. You might finance a PV system with a home equity loan. Or if you're building a new house, you can fold the cost into your construction loan. Recently a few companies have been offering leasing arrangements. In those deals, the solar company installs a PV system on your home and retains ownership of it. You make monthly lease payments that should be lower (or at least no higher) than what you're currently paying for electricity. When the lease ends, you may have the option to buy the system or have it removed. Since this is a relatively untested arrangement, make sure you understand all the fine print before making a commitment.

  • Rebates. Depending on where you live, rebates and other incentives can help bring costs down. Check the DSIRE database for incentive details by state. Even some cities are starting to offer innovative programs to help their citizens defray the high upfront cost of PV. Berkeley, California, plans to offer a program that would let homeowners pay for solar systems through a long-term assessment on their individual property tax bill.

Other Considerations

  • The average cost of a PV installation in the United States in 2007 was $7.62 per watt, after available state and federal incentives. That comes to roughly $15,000 to $30,000 for a typical 2 to 4 kW system. Maintenance is no big deal. PV modules have no moving parts and just need an occasional hosing off when you haven't had rain or snow for a while.

  • First-generation PV systems, which still account for the vast majority of the market, are modular panels that look like big glass windows. But other types of PV systems are now available, including solar shingles. They look a lot like ordinary roof shingles and become a part of the roof. They cost more than regular PV panels but if you're planning to reroof, solar shingles can offset the cost of some of the new roofing.

  • Expect PV modules to last 20 to 30 years. You'll also need an inverter, which converts a PV system's direct current to the alternating current you use in your house. It's likely to have a 10-year warranty. If your system has batteries to store the energy you've collected from the sun (most don't because of the expense), expect them to last seven to ten years.

  • In remote regions, an "off-the-grid" or independent PV system may be more cost effective than running wires to connect with the utility grid. With these off-the-grid systems, the home is powered entirely by PVs, with a bank of batteries storing excess electricity for use when the sun isn't shining.

  • In states with "net metering" laws, most residential PV installations are connected to the local utility's electricity grid or "on-the-grid." (More than 30 states have net metering laws; check the DSIRE database to find out about your state.) This allows you to feed any excess electricity your system may generate into the grid. And when the sun isn't shining, your home draws the electricity it needs back out of the grid. Your electricity meter tracks the outputs and inputs. Over a 12-month period, you pay only for the electricity you used above what your system produced. Unfortunately, these net metering laws also stipulate that the utility company need not pay you for surplus electricity you may have generated over the same period. For this reason, most people size their PV system so that it won't produce more than their expected annual electricity use.

  • Off-the-grid installations need batteries to provide power at night and during cloudy periods. Most grid-tied systems don't include them because they drive up the system's price. But if there's a local power outage, utility companies require an automatic shutdown of your power and everyone else's--for the safety of utility line workers out repairing power lines. If you want the security of having back-up power during grid outages, you'll need to add batteries to your system.

Benefits... your wallet
It will take a while, but eventually the energy savings from a PV system save you money. In addition, the system will give you a hedge against future energy price increases. And it may increase the value of your home. According to the U.S. Department of Energy, a PV system may add $10 to $20 to your home's worth for every dollar in energy costs saved in one year. For example, a system that reduces energy costs by $500 per year might add $5,000 to $10,000 to the home's value. An added bonus: PV systems can help extend your roof's life by protecting it from ultraviolet rays and weather. the Earth
While it's true that energy and other resources like heavy metals are used to manufacture a PV system, after about three years the clean energy it produces and the emissions it reduces more than make up for that initial expenditure. Compared with conventional power plants, PV systems reduce greenhouse gas and heavy metal emissions by at least 89%. If you're worried that the push for solar power will wind up blanketing the Earth with solar hardware, relax. In the United States, cities and buildings cover about 140 million acres of land. We could meet all our current electricity needs simply by putting PV systems on 7% of that area, according to the U.S. Department of Energy.

Common Mistakes

  • Wasting the electricity you produce with inefficient appliances and a leaky house. It's a lot cheaper to save a watt of electricity than to produce one. It makes no economic sense to pay the high cost of PV if you haven't yet invested in conservation.

  • Thinking it's all or nothing. There's no reason that your PV system has to meet 100% of your electricity needs. Even if you're only offsetting a quarter of your consumption, you're doing something good for the Earth and helping bring your energy costs in check. If you can't afford a system big enough to supply all your energy, consider installing a smaller system now and expanding it later.

Getting Started

A PV system is usually professionally installed, but if you're experienced with wiring and construction, you can buy the components and install it yourself. Beware that DIY installations may void the equipment manufacturers' warranties. If hiring an installer, be sure to ask the following:

  • Does the solar professional have experience designing and installing the type of system you want?
    If you are in the market for a solar pool heater, for example, don't hire a contractor who has only installed photovoltaic systems.

  • How many years has the contractor has been in the solar business and how many installations have they done? Solar is booming in many parts of the country; be cautious about hiring a newbie contractor.

  • Is the contractor licensed? Some states require solar contractors to have special licenses; check with the contractors' license board in your state about requirements.

  • What specific services will the solar contractor provide? Most offer a "turnkey" service: they'll analyze your site and energy needs, design an appropriate system, procure the equipment and materials, handle the utility company and rebate paperwork, obtain any necessary permits, and install the system.

  • Are the bids you received based on comparable information? When evaluating bids, make sure they are for the same type and size system. The bids should include all costs associated with buying and installing the system, including hardware, installation, permits, and grid connection (for PV systems). For PV systems, the bids should state the expected energy output in kilowatt-hours. Bids for solar hot water systems should include an estimate of how much energy will be saved in kilowatt-hours or "therms" (which each contain 100,000 Btu).

  • For general advice on what questions to ask contractors and other tradespeople, see our "What to Ask Your Contractor" article.

No comments:

Post a Comment