FREQUENTLY ASKED QUESTIONS
ARE THERE STATE INCENTIVES TO HELP WITH COST OF THE SYSTEM?
Go to www.dsireusa.org to find out what grants or incentives are available in your state.
WHAT WILL IT COST FOR ME TO GO SOLAR?
Many factors can come into play, such as your energy usage, roof orientation, and shading. Several states and cities also have rebates that can dramatically affect the install price.
WHAT ARE PHOTOVOLTAIC CELLS?
Photovoltaic cells were developed at Bell Laboratories in the early 1950s as a spinoff of transistor technology. Very thin layers of pure silicon are impregnated with tiny amounts of other elements. When exposed to sunlight, small amounts of electricity are produced. They were mainly a laboratory curiosity until the advent of spaceflight in the 1950s, when they were found to be an efficient and long-lived, although staggeringly expensive, power source for satellites. Also, the utility companies couldn’t figure out how to get their wires out into space, so PV was really the only option! Since the early ’60s, PV cells have slowly but steadily come down from prices of over $40,000 per watt to current retail prices of around $5 per watt, or in some cases as low as $3 per watt for distributors or in very large quantities.as low as $3 per watt.
HOW LONG DO PV MODULES LAST?
PV modules last a long, long time. How long? We honestly don’t yet know, as the oldest terrestrial modules are barely 45 years old and still going strong. In decades-long tests, the fully developed technology of monocrystalline and polycrystalline modules has shown to degrade at fairly steady rates of 0.25%-0.5% per year. First-generation amorphous modules degraded faster, but there are so many new wrinkles and improvements in amorphous production that we can’t draw any blanket generalizations for this module type. The best amorphous products now seem to closely match the degradation of single-crystal products, but there is little long-term data. Most full-size modules carry 25-year warranties, reflecting their manufacturers’ faith in the durability of these products. PV technology is closely related to transistor technology. Based on our experience with transistors that just fade away after 20 years of constant use, most manufacturers have been confidently predicting 20-year or longer life spans for PV systems. However, keep in mind that PV modules are seeing only six to twelve hours of active use per day, so we may find that life spans of 60-80 years are normal. Cells that were put into the truly nasty environment of space in the late 1960s are still functioning well. The bottom line? We’re going to measure the life expectancy of PV modules in decades – how many, we don’t yet know.
WHAT IS THE DIFFERENCE BETWEEN SOLAR THERMAL AND SOLAR PHOTOVOLTAIC?
Solar Thermal systems collects and converts Ultraviolet radiation from the sun into heat. This heat is then used to warm a glycol-water mix that is then used to heat the domestic water supply, provide heating for your home or business, generate electricity, or provide air conditioning. Solar Photovoltaic systems collects and converts visible light into electricity.
I’VE ALWAYS HEARD THAT SOLAR IS MORE WASTEFUL THAN EFFICIENT SINCE IT COSTS SO MUCH TO PRODUCE THE MATERIALS. IS THAT TRUE?
In the early years of the PV industry, there was a nasty rumor circulating that said PV modules would never produce as much power over their lifetimes as it took to manufacture them. During the early years of development, when transistors were a novelty, and handmade PV modules costing thousands per watt were being used exclusively for spacecraft, this was true. The truth now is that PV modules pay back their manufacturing energy investment in about 1.5 years’ time (only a fraction of the typical warranty period), depending on module type, installation climate, and other conditions. Now, in all honesty, this information comes to us courtesy of the module manufacturers. The National Renewable Energy Laboratory has done some impartial studies on payback time. It concludes that modules installed under average U.S. conditions reach energy payback in three to four years, depending on construction type. The aluminum frame all by itself can account for six months to one year of that time. Quicker energy paybacks, down to one to two years, are expected in the future, as more “solar grade” silicon feedstock becomes available, and simpler standardized mounting frames are developed.
WHAT IS THE MAINTENANCE ON AN INSTALLED SOLAR POWER SYSTEM?
It’s almost laughable how easy the maintenance is for PV modules. Because they have no moving parts, they are virtually maintenance free. Basically, you keep them clean. If it rains irregularly or if the birds leave their calling cards then you can simply hose the modules down. Do not hose them off when they’re hot, since uneven thermal shock could theoretically break the glass. Wash them in the morning or evening. For PV maintenance, that’s it.
WHAT IS AN INVERTER?
An inverter is an electronic device that converts (transforms) the low-voltage DC power we can store in batteries to conventional AC power as needed by lights and appliances. This makes it possible to utilize the lower-cost (and often higher quality) mass-produced appliances made for the conventional grid-supplied market. Inverters are available in a wide range of wattage capabilities. We commonly deal with inverters that have a capacity of anywhere between 150 and 500 Kilo-watts.
WHAT IS A PV MODULE?
This is what you might call a “solar panel” that makes electricity when exposed to direct sunlight. PV is shorthand for photovoltaic. We call these panels PV modules to differentiate them from solar hot-water panels or collectors, which are a completely different technology and are often what folks think of when we say “solar panel.” PV modules do not make hot water.
I’M NOT SURE IF MY HOUSE GETS “FULL SUN”. WHAT DOES THAT MEAN EXACTLY?
Most people seldom see 100% full-Sun conditions. If you are not getting full, bright, shadow-free sunlight, then your PV output will be reduced. If you are not getting bright enough sunlight to cast fairly sharp edged shadows, then you do not have enough sunlight to harvest much useful electricity. Most of us actually receive 80%-85% of a “full Sun” (defined as 1,000 watts per square meter) on a clear sunny day. High altitudes and desert locations will do better on sunlight availability. On the high desert plateaus, 105%-110% of full Sun is normal. They don’t call it the “sunbelt” for nothing!
WHAT IS A ‘UTILITY INTERTIE’ SYSTEM? IT SEEMS REALLY COMPLICATED.
These are actually very easy. Whatever your renewable energy system doesn’t cover, your existing utility company will. So we don’t need to account for every watt-hour beforehand. Tell us either how much you want to spend, or how many kilowatt-hours of utility power you’d like to displace on an average day. For direct-intertie systems without batteries, you’ll invest about $2,500 for every kilowatt-hour per day your solar system delivers.