Learn how you can save on electricity costs by installing a solar photovoltaic system in your home.
Chris Banks and Paula Minucci were faced with a decision. Just bringing electric service to their beautiful mesa homesite near Carbondale, Colorado, was going to cost thousands even though the site was less than a mile from the nearest utility line. They wanted to have all the modern-day comforts, but couldn't convince themselves that forking over $8,000 to connect to the utility — and then to be burdened with a lifetime of electric bills — was a wise investment. Instead, they decided to put their money where they could reap a return: in a photovoltaic (PV) system.
Even before he was faced with the sticker shock of connecting to the utility grid, Chris was interested in using solar energy. "[Resources] are going away faster than [they are] being replaced," Chris says, "so any way to conserve helps out in the big picture."
Sizing the Solar Photovoltaic System
Chris and Paula visited Sunsense, Inc., a local PV dealer and installation company in the Roaring Fork Valley of Colorado, to discuss their energy requirements. Sunsense owner Scott Ely showed them different equipment options, and explained what they could expect from a PV system. Ely and his associates also visited the Banks-Minucci building site to determine the best placement of the system and help them calculate their electric loads.
Chris and Paula have many of the typical electric needs of a U.S. family: lights, toaster, blender, hair dryer, juicer, stereo, television, refrigerator and washing machine. Along with lighting needs, refrigerators, washing machines, electric heaters, air conditioners and electric ovens usually are the biggest electrical loads in a house. Thanks to their lower consumption of energy, high efficiency refrigerators and horizontal-axis washers are easy to run on solar electricity. (Appliances that use electricity to generate heat such as electric stoves and heaters are relatively inefficient and not well-suited to solar electric.) Chris and Paula bought a Sunfrost refrigerator and a Staber washing machine, which both retain their warranties even connected to a PV system. Highly insulated Sunfrost refrigerators use about one-quarter of the energy of conventional refrigerator. Their Staber washer, besides saving about two-thirds of the water typically used, also cuts energy usage in half, compared to vertical-axis washers. Chris and Paula also chose energy-efficient compact fluorescent lightbulbs, which require one-quarter of the energy used by incandescent lightbulbs. just this simple switch — investing in 10 15-watt compact fluorescent fights, instead of 10 60-watt incandescent lights — can make the difference in buying three to four fewer 100-watt PV panels — a savings of thousands of dollars.
Using the calculations the couple provided to him, Ely designed an eight-panel "starter" system that could be expanded to 12 panels as the budget allowed. A backup propane-powered generator, says Ely, was the ace in the hole that enabled the initial implementation of a smaller, more inexpensive system. (You can calculate your own household's energy loads by using the Electric Load Estimation chart and the Wattage Chart, which are in the Image Gallery.)
Siting the Solar Photovoltaic System
Ely advised Chris and Paula as to how far the panels could practically he mounted from the house, and together the three of them figured out the best location. Paula was adamant about keeping the house's appearance streamlined, which meant leaving the panels off the roof. They also wanted to preserve the home's attractive entryway and didn't want panels visible from the house or the driveway. Eventually, they found a perfect sunny spot behind the house to place the array.
Pole-mounted PV systems have the advantage of being able to be connected to a tracking mechanism that follows the sun from east to west (and, in the case of dual-axis trackers, from horizon to sky). Tracking systems can increase the amount of power a multicrystalline PV system annually produces by up to 25 percent. Although trackers are well-suited for applications such as a batteryless water pumping system, which can use solar energy the second the sun comes up, for many applications it's more economical to add another panel or two than to invest in a tracker. The Banks-Minucci system is the best of both worlds: a polemounted system that can be manually adjusted throughout the day and year. To capture the most from the sun, Chris adjusts the tilt of his panels to different sun angles throughout the year. To follow the sun's arc through the sky, Chris daily repositions the panels. He doesn't think of it as work or an inconvenience, but takes a special enjoyment in what he considers "farming" the sun.
Solar Photovoltaic System Components
PV panels are only one part of a solar-electric system. For the Banks-Minucci off grid application, eight deep-cycle batteries store electricity for nighttime and cloudy-day use. A controller keeps the batteries from being overcharged, and an inverter converts DC electricity produced by the solar panels into AC electricity typically used by home appliances. A 4,000-watt inverter, oversized for their initial system, provides expansion possibilities if Chris and Paula want to add more energy production.
Living With the Solar Photovoltaic System
Unlike grid-connected systems, standalone photovoltaic systems require more owner involvement, and maintenance is essential to keep a system functioning properly. But in the past seven years since the system was installed, Chris and Paula have called Sunsense only a few times with questions or problems.
Both feel that living with solar hasn't dramatically changed their lifestyle. "Conserving energy is not a sacrifice, but more of an awareness," says Chris. Although he and Paula considered themselves "environmentally conscious," they both admit they now are much more aware of the instant payoff of their energy conservation — and the almost instantaneous repercussions of being neglectful: If you leave the lights on, the PV system runs low, the generator goes on and the propane bill goes up.
Chris and Paula do use their backup generator in the winter more than they would prefer. Two years ago, when they realized they needed more power and had a few extra dollars to invest in their system, they decided to add four 100-watt panels, bringing their entire system's energy production capabilities to 1 kllowatt. Instead of hiring out the job, Chris made a couple of calls to Solar Energy International, a renewable energy education center. With SEI's advice and Ely's previous work, he integrated the four new panels himself.
PV System Components
• 8 75-watt Siemens photovoltaic (PV) modules
• 4 100-watt Siemens PV modules*
• Ananda Powercenter 3
• Trace 4024 Inverter
• 8 Trojan L- 16 Batteries
PV System Costs
8 75-watt Siemens modules: $2,400
APT Powercenter: $1,700
Trace 4024 Inverter: $3,200
8 Trojan L-16 Batteries: $1,500
Misecellaneous materials: $650
The Power Of PV
A single PV cell is made of highly purified silicon that is doped to create a voltage difference on each side of the cell. Sunlight striking a PV cell knocks electrons loose, which frees them to flow in a current. Metal contact points on the top and bottom of the cell draw the current off for whatever external use is intended. On a bright, sunny day, the sun shines about 1,000 watts of energy per square meter of the Earth's surface; if we can just collect part of that energy economically, we can easily power our homes and offices with sunlight instead of oil. (For more on how solar cells work, click here.)