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Our house is a passive solar design that provides its own heat and power. We have 1200 watts (about 40 amps max) of photovoltaic (PV) panels that provide our electricity. The panels are split between two arrays, one array is on the roof of the house and is made up of 6 Solec S-100 solar panels, each of which produces 100 peak watts and is wired for 24 volts. The other array is mounted on the hill behind the house and consists of 8 BP Solar 75 watt panels. On a day of full sun we can get as much as 6.5 kilowatthours of energy. Contrary to what you might think we can get more power out of the system in the winter than during the summer.

Two factors enter into this odd state of affairs. First, the weather here in the Colorado high country tends to be clearer during winter days. We have lots of days in the winter when the sun shines brightly in a cloudless sky from sunrise to sunset. In the summer we often have clouds forming by noon and afternoon thunderstorms. The clouds cut significantly into our insolation (solar gain) time.

The second factor is temperature. Cold winter temperatures make our PV modules more efficient, in full sun the bank can generate over 45 amps.

Another factor that doesn't come readily to mind but has an impact on our power generation is our altitude. At our 9000' elevation the sun is much stronger than it is at sea level. Panels are rated for power output at sea level where the average energy falling on the surface of the Earth is 1000 watts per square meter. However we get more than that per square meter because the thinner and clearer air at this altitude allows more energy to reach the ground.

This is the inside of the greenhouse, fresh greenery all year round! The two stories of glass provide abundant sunshine and heat during the winter months when the sun is low and the 2 foot roof overhang shades the glass in the summer when the sun is high.

The net you see in the picture is really just a great big hammock. Produced by the Billy Pugh Company in Texas, it is actually a safety net, easily supporting four or five people (and a couple of cats). A great way to lounge in the sun on a winter day! One unexpected advantage of the net is that it makes a great place for drying laundry. When we built the house we plumbed the laundry area for a gas dryer but have never bothered buying one. The net is a very efficient way to dry and doesn't use any power!

We have been going through all sorts of "growing pains" (pun intended) with the greenhouse. We've had the obligatory infestation of insects, which seems to be slacking off and are learning the best areas in the greenhouse for growing (some areas get more shade than others). So far we've had some success with tomatoes (they grow best in the winter) and have found that our house plants are growing wild. We are learning that plant cuttings make great gifts.

We've planted our banana plants in the middle of the greenhouse in the best soil we could design. We've already gotten a crop of bananas out of it and are looking forward to more. The bananas you see in the left of the photo have been producing bananas regularly, fabulous bananas too. The location at the front of the greenhouse allows them to get abundant sunshine and they are far more productive than the original plants, which are still there but not producing much these days. Our first banana crop was a treat and has now been duplicated by the transplants at least 3 times. We've now moved out of the house since we've put it on the market and it spent this current winter empty and relying only on the passive solar heating. Yet, despite that the bananas are doing fine, which really shows how effective the passive solar design is as this past winter has seen temperatures in the -20f range.

Over years we've made adjustments to the greenhouse space. We actually started out with sod on the floor, thinking the green would be a nice surface and that we might have to put a stone walkway into it if the traffic areas couldn't stay green. That turned out to be a bad idea on a lot of levels. First, the greenhouse windows utilize a type of glass called "heat mirror" which reduces severely the amount of UV light and heat (to prevent overheating with all that glass) and this resulted in the sod not getting nearly the light it needed, regardless of how religiously we watered it.

Then, the bugs came out. The bug population in sod isn't a problem outdoors, but inside it was a disaster. The bugs had a field day in our controlled environment and thrived all winter long, to our dismay. It took us a couple of years to get them under control.

And of course, the cats just loved it, especially when the grass started to die and the digging got easier

Our second attempt was to put in sandstone pavers (once we had hauled off all the old sod). This was an improvement. The cats couldn't get to the dirt and it gave us a hardy floor material but it was a step down from both the living room and the kitchen and was an uneven surface at best.

Since we had wanted the first floor to be handicap accessible and the step down from the two main rooms made that obviously impossible I decided, a year ago, to install a redwood deck. The space is a mimic of the outdoors, after all, and a deck not only looks like it belongs it also manages to tie the whole first floor together on a single level.

We started out with a wind generator, a Southwest Windpower Air 303. However it turned out not to have the output we were led to believe, something that was compounded by the thin air here at 9000'. We have replaced it with 8 BP275F PV panels. The installation of the panels was a snap, made easier by the fact that I already had the appropriate size wire run out to the wind generator location. I just moved the wire over to the panels and connected them to the system. We now have an input of 40 amps @ 24 vdc. These are the panels I mentioned above. It is really amazing the difference these panels have made over the wind generator. I mounted the panels on a 4" schedule 40 pipe set in concrete. When the panels are set at their winter (near vertical) orientation and we have snow on the roof we will get some addition power generation from the light reflecting off the snow.

Our Roof PanelsI have also raised the front of the rooftop panels by 18" to allow for clearance in the winter. This will keep snow that sloughs off the panels from shading the lower sections of the panels and reducing their output and will dramatically improve our winter input and greatly reduce the time I have to spend on the roof cleaning snow (not a fun job). It also reduces shading from the clerestory walls to the east and west of the panels, further increasing our input.

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Wagonmaker Press
Thomas W. Elliot