FREQUENTLY ASKED QUESTIONS

Will my roof leak? Your solar installer should be trained in proper roofing methods to prevent the solar mounting hardware from causing roof leaks. If you have a metal roof of the "standing seam" type the hardware can clamp to the seam itself with only piping or conduit penetrations required. If you have a flat roof, as with most commercial property, your solar company may want to sub-contract the roof attachments and penetrations to a roofing company. With PV there are ballasted mounting systems for flat roofs that require no mounting penetrations and will withstand winds up to 90 mph. This is not the case, however, with thermal collectors because the copper piping cannot withstand the small movements that a PV system can sustain with its flexible wiring.

Will snow be a problem? Any sloped roof facing South ± 30˚ will tend to melt once it is exposed to sunlight. Also sunlight actually penetrates snow with enough light striking the panels or collectors to cause them to start working just enough for their waste heat to melt the snow as well.

What about hail? Will it break the glass over the collectors? They are as resistant as skylights and it is uncommon for skylights to break in a hailstorm. The Sunda brand evacuated glass tubes are rated to withstand hail up to about 1.5" diameter at terminal velocity.

Do photovoltaic panels require any cleaning? In some areas heavy dust might accumulate as well as bird droppings. Usually it rains often enough that this is not an issue. In a prolonged drought you might want to take your garden hose to them with a spray nozzle, but this can be done from the ground.

What is a solar site analysis? Every potential location for a solar installation has a solar window. It would be unusual if some of that window were not partially shaded by trees, mountains, or other buildings some of the time. Your solar system designer will come to your home or business and discuss the possibilities with you and then use an analysis tool to determine the percentage of shading in the solar window. Some of the analysis tools are designed to interface with computer software that automatically calculates the shading factor. This information then makes it possible to determine how much energy can be produced at that particular location. Without this piece of information it is impossible to determine the payback time period discussed on previous pages.

So how big a deal is shading? With thermal collectors there is a general rule of thumb that if it is, for example, 10% shaded at any given time, then it is 90% efficient. However, with PV this is not the case. With small systems all the panels will be wired in series. With larger systems there may be 2 or more series strings wired in parallel. If one string has any shade at all its efficiency will be very poor. Other strings, fully in the sun, will have full efficiency. It's analogous to the old Christmas lights metaphor. If a string of lights is wired in series and one bulb burns out then none of them work, but if they are wired in parallel then one bulb does not affect the others. The thoroughness, or lack of it, on the part of your solar installer toward shade analysis can profoundly affect the final efficiency of your PV system. As for you, the consumer, plant only trees in front of the installation that do not grow tall and eventually shade it.

How can I keep up with rebates, credits, and other incentives? At www.dsireusa.org click on your state on the national map. This will take you to all federal, state, and local incentives. It is periodically updated, but it still may lag by a few months. Something not mentioned elsewhere on this site is that under Colorado HB 1279 Solar Energy Equipment Sales Tax Exemption you can get a 2.9% state sales tax exemption on PV panels. This does not apply to inverters, racking or wiring. This is a recent tax clarification as of Jan. 2008, and is retroactive to May 2007.

Should I wait for a technology breakthrough? Solar thermal is here now and nothing big or new is on the horizon. The same could be said for photovoltaics. It is probable that as PV becomes more mainstream that the price will come down some as a result of economies of scale, but this will be quite gradual and over a period of years. As for a technology breakthrough in PV the most likely candidate is to increase the light spectrum range utilized by PV modules. Currently the spectrum range is near the infrared end of white light and on into the infrared range. The photovoltaics used on space satellites, etc. have efficiencies of converting light into electricity in the 40's % compared to our applications around 16 to 18%, but this is because they utilize a wider frequency band and cost is no object. There is ongoing R&D to make this technology affordable, but there are no indications it will be anytime soon. You may also have heard of solar cells made of cadmium telluride as opposed to silicon. However, this is toxic metal mining and you have to ask is this really the way we want to go? Besides, silicon is still more efficient.

Aesthetics. Sometimes you see solar collectors or PV panels racked up where they are not set parallel to the roof slope. Is this really necessary? The ideal year round angle to the horizon is the geographical lattitude of your location. This is about 37˚ here in Durango and is the equivalent of a steep roof pitch. With PV the inefficiencies of not racking to lattitude are fairly inconsequential. With solar thermal collectors it is a more significant, but aesthetics matter as well. Perhaps an additional collector will make up the difference and they can all lay parallel with a lesser pitched roof, and, of course, a pole or ground mount can be set to the ideal angle. With radiant space heating the ideal angle is going to be lattitude plus 15˚ because the sun is lower in the winter sky. This is 52˚ for Durango, another reason to consider a ground mount for maximum radiant space heating efficiency.

Can my homeowner's association prevent me from installing solar on my property? Actually Colorado has a law dating back to the 70's prohibiting HOA's from doing this. Currently there is a bill before the state legislator which would allow HOA's to have a say as to the appearance or aesthetics of the installation, but not to the point where it would effect a major increase in the cost. The final disposition and wording of this remains to be seen.

If your question is not answered here, it is probably covered to some degree on the other pages. If not feel free to call and ask.