Hi/Low
Tech-Low Watts:
Getting
the Most from an Off-Grid Solar System
The
goal with this off the grid home was to minimize
electrical consumption but not give up any
modern conveniences using creative solutions
either hi-tech or very low-tech. In October 2009
we installed more solar panels at a steeper
pitch (so snow falls off quicker).
Minimize
electric use for heat and hot water using
passive and active strategies: Passive
solar heating and masonry fireplace coupled with
superior insulation provide most of the heat
needed without any electric use. Radiant infloor
heat uses propane or solar hot water requiring
only pumps, however at approximately 600 Kwh to
run, these 2 pumps use more electricity than I
anticipated, but there is plenty of power if
heating used during day. Propane fireplace in
master bedroom for heat where only the fan only
uses electricity. Solar hot water system provides
almost all domestic hot water and pump uses "free
electricity." The well pump is relatively small
(1/2 HP) but is AC.
Timing
of electric use to maximize "free electricity":
The photovoltaic system is robust and generates
far more electricity than can be used and stored
in the battery bank on a sunny or partly sunny
day. This is the time to use the radiant infloor
heat (house retains heat well overnight and no
heat needed at night), use the
washer/dryer/dishwasher, use power tools, run the
vacuum, use HRV etc. The solar hot water system
pump is only needed when the sun is shining.
Minimize 24/7 electricity use to what is most
important: Refrigerator, radon fan,
router/modem/webcams/internet of things devices,
raspberry pi for monitoring outback data and use as server, radon monitors,
smoke/carbon monoxide/propane detectors, inverter.
The radiant infloor heat comes on automatically
when the solar hot water tank reaches a user
specified temperature. I also can run the electric
space heater to use up excess electricity during
float since with an off-grid home, unused
electricity is just thrown away.
Measure
electric usage: I use Kill-A-Watt
monitor to measure wattage of appliances,
electronic equipment etc. Also, the newer smartplugs such as Sonoff with Tasmota or Zigbee have built in electric monitoring.
Appliance
selection including energy star: Energy
star dishwasher, washing machine, refrigerator.
Refrigerator choices for an off the grid home
include DC electric and propane refrigerator but
the current generation of energy star
refrigerators are so energy efficient and so
inexpensive relative to the other options that the
price differential more than makes up for the
increased cost to a PV system. The hot water
heaters, dryer, and stove use propane as a fuel
source. The stove uses electricity for the
electronic ignition only. It does not have a glow
bar (large electricity user in essentially all
other ovens in US) and does not even have an
electric clock. I try to use the microwave only
during the day and it has a phantom amp power
strip to turn it off.
Energy
efficient lighting: This house uses energy efficient LED lighting. No CFL lights are still used. I have
motion detectors in the bathrooms, pantry, a
closet, and laundry room.
Radon
mitigation : Radon level was found to
be very high with this extremely tight home
(38.7). After sealing and caulking the floor and
about a year of expermentation with multiple types
of radon fans using various combinations of 3
pipes inserted under and around the slab, and HRV
timing, a good result was obtained using the
minimum of electricity. The current plan uses DC
radon fans which have excellent performance with
few watts. A 24V 38 watt DC fan pulls air from
under the house from the garage. It currently uses
AC power with a DC transformer. A 12V 27 watt DC
fan hooked up to a left over solar panel from our
construction RV (does not draw off the main house
batteries) and another 24V 38 watt fan are
attached to a drain pipe and pull air from the
drain pipe running behind the house and the
garage. There is also a pipe which allows for
passive ventilation from under the kitchen in the
back of the house. I have two continuous radon
monitors whose values can be seen on the internet, one of which sits on the kitchen desk and the other in the loft. The
radon level now runs about 2 or less if fans are working.
Eliminate
phantom amps: Many appliances,
electronic equipment and other items use quite a
bit of power when they are off. They should be
really off by pulling the plug or turning off
their power supply. The simplest solution is using
a power strip or an outlet switch which is turned
off after the item is no longer needed. Phantom
amp switches are hard wired for the 2 garage door
openers and the stove although the stove that I
purchased does not need this because it has no
electronic components.
Strategies
to make use of electricity more difficult:
Kitchen sink garbage disposal switch is under the
sink. Trash compactor is in laundry room rather
than kitchen so that it is compacted less often.
Computer/Electronics/Telephone:
Energy star laptops and monitors. Use laptop in
preference to desktop because it uses far less
energy. Modem to Viasat satellite internet,
wireless router and webcams use very little power.
I had an Acer netbook on continously to run the
Wattplot program for monitoring our Outback
inverter and charge controllers. This died in
October 2018 and the program was no longer
supported. I replaced it with a linux based
netbook and a python program that I wrote which
captures the outback data from the outback mate
via a serial connection and stores it in a MySQL
database. When the netbook died, I substituted a
Raspberry Pi 4 to capture the solar data. The TV
and sound system are good relative to alternatives
but still use power. The best solution is to have
reasonable viewing habits. Stereo and video wiring
is in walls so power for wireless equipment not
needed. I now use voice over internet protocol for
phone service which is wired to the phone jacks. I
have some ordinary phones which draw power from
the phone jack only.
Find
solutions to problems using less or no energy:
Climate is very harsh and septic tank froze.
Common solution in this area is to use heater at
about 1kwH. We put 4 inches of foam insulation and
then 4 feet of dirt above septic tank. Advance
planning with deeper septic tank would have been
much better.
|