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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