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Now
is the time to become your own Power Producer. We can help with all of your power system needs.

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SYSTEM
SIZING INFORMATION
The size
of a solar electric system depends on the amount of power
that is required (watts), the amount of time it is used
(hours) and the amount of energy available from the sun in
a particular area (sun-hours per day). The user has
control of the first two of these variables, while the
third depends on the location.
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Conservation
Conservation plays
an important role in keeping down the cost of a photovoltaic
system. The use of energy efficient appliances and lighting,
as well as non-electric alternatives wherever possible, can make
solar electricity a cost competitive alternative to gasoline
generators and, in some cases, utility power.
Cooking, Heating,
& Cooling
Conventional
electric cooking, space heating and water heating equipment use a
prohibitive amount of electricity. Electric ranges use 1500
watts or more per burner, so bottled propane or natural gas is a
popular alternative to electricity for cooking., A microwave
oven has about the same power draw, but since food cooks more
quickly, the amount of kilowatt hours used may not be large.
Propane and wood are better alternatives for space heating.
Good passive solar design and proper insulation can reduce the
need for winter heating. Evaporative cooling is a more
reasonable load than air conditioning and in locations with low
humidity, the results are almost as good. One plus for
cooling -- the largest amount of solar energy is usually available
when the temperature is the highest.
Lighting
Lighting requires
the most study since so many options exist in type, size, voltage
and placement. The type of lighting that is best for one
system may not be right for another. The first decision is
whether your lights will be run on low voltage direct current (DC)
or conventional 110 volt alternating current (AC). In a
small home, an RV, or a boat, low voltage DC lighting is often the
best choice. DC wiring runs can be kept short, allowing the
use of fairly small gage wire. Since an inverter is not
required, the system cost is lower. When an inverter is part
of the system, a home will not be dark if the inverter fails and
the lights are powered directly by the battery. In addition
to conventional-size medium-base low voltage bulbs, the user can
choose from a large selection of DC fluorescent lights, which have
3 to 4 times the light output per watt of power compared with
incandescent types. Halogen bulbs are 30% more efficient and
actually seem almost twice as bright as similar wattage
incandescent because of the spectrum of light they produce.
High quality fluorescent lights are available for 12 and 24 volt
systems.
In a large
installation or one with many lights, the use of an inverter to
supply AC power for conventional lighting is cost effective.
AC compact fluorescent lights will save a tremendous amount of
energy. It is a good idea to have a DC-powered light in the
room where the inverter and batteries are in case there is a
problem. Ac light dimmers will only function properly on AC
power from inverters that have pure sine wave output.
Refrigeration
Gas powered
absorption refrigerators are a good choice in small systems if
bottled gas is available. Modern absorption refrigerators
consume 5-10 gallons of LP gas/month. If an electric
refrigerator will be used in a stand-alone system, it should be a
high efficiency type. Some high-efficiency conventional AC
refrigerators use as little as 1200 watt-hours of electricity/day
at a 70� average air temperature. A comparably sized Sun
Frost refrigerator/freezer uses half that amount of energy and a
Sundanzer refrigerator (without a freezer) uses less than 100
watt-hours per day. The higher cost of good quality DC
refrigerators is made up by savings in the number of solar modules
and batteries required.
Major Appliances
Standard AC electric
motors in washing machines, larger shop machinery and tools, swamp
coolers, pumps, etc. (usually 1/4 to 3/4 horsepower) require a
large inverter. Often, a 2000 watt or larger inverter will
be required. These electric motors are sometimes hard to
start on inverter power, they consume relatively large amounts of
electricity, and they are very wasteful compared to
high-efficiency motors, which use 50% to 75% less
electricity. A standard washing machine uses between 300 and
500 watt-hours per load, but new front-loading models use less
than 1/2 as much power. If the appliance is used more than a
few hours per week, it is often cheaper to pay more for a
high-efficiency appliance rather than make your electrical system
larger to support a low-efficiency load. Vacuum cleaners
usually consume 600-1000 watts, depending on how powerful they
are, about twice what a washer uses, but most vacuum cleaners will
operate on inverters larger than 1000 watts because they have
low-surge motors.
Small Appliances
Many small
appliances such as irons, toasters and hair dryers consume a very
large amount of power when they are used but by their nature
require very short or infrequent use periods, so if the system
inverter and batteries are large enough, they will be
usable. Electronic equipment, such as stereos, televisions,
VCR's and computers have a fairly small power draw. Many of
these are available low voltage DC as well as conventional AC
versions, and in general, DC models use less power than their AC
counterparts.
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