William von Brethorst
©1997 William von Brethorst
Above: The Zars Homestead with its new PV and wind power system.
A bout 10 miles north of Hayden, L V Colorado is the Zars Homestead (TUwhich has been in existence for over 100 years. It has been without electricity or services from the beginning. The present owner, Reed Zars of Laramie, has been slowly rebuilding the main cabin after a fire caused by lightning destroyed the original structure. He had a limited budget and wanted systems and designs which could be upgraded as building use increased or as new services and amenities were added. For now, the cabin is used only on weekends and occasionally for three or fours days at a time during holidays.
The property has the distinct advantage of a year-round spring piped into the cabin crawl space (a delight, in that the crawl space was almost 6 feet high and the full length of the cabin). The spring was generally available even in the depths of winter, though sometimes the transfer pipe froze up. The spring provides about 10 gpm but only about 5 to 10 psi in pressure. This could not properly supply the toilet and sinks, nor safely supply the propane water heater.
After the usual preliminary "what-if?" scenarios, a plan was decided on to install the main components of a system for water, heat, and electricity that would allow future re-work as cabin usage changes. Because the cabin is usually not heated unless occupied, all major electrical equipment was located in the crawl space. Its depth, size, and location would assure a year-round temperature difference of only 30° to 40°. In the summer the space would be cool (45°F) and in the winter, the radiated ground heat would keep the space around 30°F.
When the cabin was not in use, the inverter would be off, but the array controller would still be active to keep the batteries charged. After much consideration, the components chosen were a Trace DR-1524 inverter, an APT "Smart-Charger" controller, an Air-303 wind generator, two Solavolt 85 Watt modules and four Photocomm 225 Amp-hour "golf cart", wet-cell, lead acid batteries. The system voltage chosen was 24 VDC, mainly for lower line loss but also because the DC devices were 24 VDC. The batteries were mounted in an insulated box with room for four additional cells. The battery box was constructed from 3/4 inch plywood with R-11 fiberglass insulation inside and poly-cell matting over the box floor to prevent cold-sinking.
The water pressure problem was solved by adding a small 24 VDC booster pump with a pre-charged pressure tank to prevent constant cycling of the pump. The Shur-Flo 3.1 gpm pump was installed and plumbed so it could be bypassed in case of failure (as diaphragm pumps wear out faster than centrifugal pumps). A valve system allows the spring to feed the house directly, if required. A BZ products low-voltage disconnect was added so that in the event of a leak, the pump would not run continuously and completely discharge the batteries. A manual on-off switch was also installed.
The system inverter and controls were pre-fabricated on a plywood board and wired and tested in the Planetary Systems shop in Jackson. We did this
System Component Costs
Above: The Zars Homestead's power wall with Trace 1524 inverter, insulated battery box, and pressure tank system.
Below: Electrician Skip Chisolm installs the 120 vac service panel.
System Component Costs
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