A Description of this Project.

Forty eight volts direct current from the solar panels is regulated by two charge controllers to keep the batteries properly charged. The batteries in this picture are wired series-parallel with equipotential points tied together. The bank is not yet wired this way, but I hope to upgrade it at some point in the near future. An E-meter shunt is in the battery bank ground wire to monitor the flow of current into and out of the batteries to guage their efficiency and state of charge. A 400 amp fuse will open the circuit from the batteries to the inverter in the event of a short circuit. A DC disconnect removes all DC power from the inverter for system maintenance.

The power from the Grid comes through the meter outside and leads into the Utility AC Load Center in the house. This is fed into the inverter and also into a "generator switch" which is used as a GRID/PV isolation switch so the system can be run off either Grid power or Inverter Power, but the inverter will never feed back into the Utility interface. The two can not be connected to the Inverter Load Center at the same time.

The "donor" house is around fifty years old with a car port that was added at some point. The project has taken several years so far, and is coming along slowly.

The first job was to upgrade all the electrical outlets to grounded 3-prong duplexes with GFI (ground fault interrupt) outlets in areas which might contact water (kitchen, basement, washing machine, outside). This was a safety issue, bringing the wiring up to current code requirements.

The next step was to replace the greatest power consuming items with the most efficient ones I could manage to get. The rationale for this is that it is often cheaper to purchase more efficient appliances than it is to purchase the extra solar PV panels to produce more power.

I started by replacing all the lights in the house with compact flourescent bulbs. I added low voltage lighting for background lighting outdoors and put the larger lights outdoors on pir (passive infrared) sensors so they only come on when a person or animal comes by. This process took a while because many of the fixtures had to be modified to accept conventional compact flourescent bulbs. In general, flourescent lights use about a third of the energy of incandescent lamps which produce the equivalent level of light.

I replaced the electric clothes drier with a gas fired one. This left a gas stove, gas drier, gas furnace, gas log, gas oven, and gas water heater, reducing the electrical loads to a minimum.

Shifting the largest electrical loads to gas will enable a moderate-sized PV system to power all the electrical loads, with the exception of air conditioning.

Further steps I am working on improve the comfort and efficiency of the heating and cooling systems.

First, I sealed all the windows and doors with caulk and weatherstripping. I installed outlet gaskets on all the switches and duplexes on outside walls. I sealed off windows which are not being used with sheets of Celotex Tuff-R(R) polyisocyanurate sheets which are R14.5 for a 1 7/8" thick sheet. I am adding ridge and soffit vents to the attic, putting in vapor barriers and working on bringing up the walls to R30 and the attic to R60 levels of superinsulation. This is a long, slow process because the house has all finished walls which are in very good condition. It is really discouraging to have to tear out a perfectly good wall just to add some insulation, so I have been working on the easier walls first, one at a time. Part of the basement has unfinished walls. The attic floor is easily accessible. The kitchen has panelling in the walls. The car port side of the house can be insulated from the outside making the brick thermal mass in the house. The area near the car port can be excavated for hot water storage and to run pipes to the solar hot water collectors and to insulate the basement wall from the outside there, as it is finished in the inside. The basement is walk- out on one side, so that side can be finished from the outside.

Rather than tear out the basement floor to insulate it from underneath, I can seal it with a vapor barrier and put insulation and carpeting on it. This will help reduce the humidity level in the house. The polyisocyanurate sheets are over $20 apiece, for a 4'x8' sheet, so I purchase three or four of them, install them little by little and then get another three or four and keep going.

The old water heater burst, so when I replaced it, I plumbed the new one with the fittings for a solar hot water batch preheater (not constructed, yet).

Needless to say, this is a long, slow, expensive process. It is much more expensive and time consuming to retrofit an existing house than it is to build it superinsulated and efficiently from the start. Of course I can live in it at the same time, so there are some advantages to retrofitting. Also, it might be hard to build a new house in the location I want it. Also, I can do the modifications little by little without financing them, while building a new house would require a substantial financial investment, as they say.

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