|
OFF GRID CASE STUDY: Off-Grid Photovoltaic System
Vic Cooper, Big Sur, California
"We were very much satisfied. I thought the job was
professionally done. The components he picked out
seemed to work well together."
"Overall I enjoyed working with Farrel, which hasn’t
been the case with other people. I did call a few
people to ask about solar installation and did Web
searches, but because we were remote, a lot of
people didn’t want to work with us."
See a larger photo
Description of Site:
The site is located in Big Sur, California about one
mile from the closest utility power pole. The
property is located on very steep terrain at 1800
feet above the Pacific Ocean with numerous scrub
oaks on site. Although the majority of the property
is steep, it does receive good southern exposure
with no obstructions.
Mr. Cooper purchased the property with an existing
solar electric power system in place, but the system
was underpowered and in poor condition. The existing
system was installed with a few low wattage modules
that were lying on the ground with exposed wires.
The system had used a low amperage charge controller
and a small bank of car batteries.
Customizing the System:
In our site analysis with Mr. Cooper, he noted that
he wanted a power system that could produce both 120
and 240 volts. This would be necessary to power a
well pump. Mr. Cooper also noted that he wanted to
be able to run a standard electric (22 cubic foot)
refrigerator and a variety of office and household
appliances. The last consideration was his desire to
eventually construct a shop that would be at some
distance from the main house and would require a
substantial amount of power to run high-demand shop
tools.
Using a 120/240 volt system allowed Mr. Cooper the
option to operate high power equipment at a longer
distance from the power source than he would have
had with just a 120 volt system.
See a larger photo
Considerations:
The most appropriate site for the solar array was
located on a steep embankment that had good
southerly exposure. Due to the high winds in the
local area, Apex Solar chose a high-strength ground
mount that allowed the array to conform to the
hillside. Also, at Mr. Cooper’s request Apex Solar
left extra racking space on the array for additional
modules to be placed there at a later time if so
desired.
Apex Solar chose an Outback Power System which used
a stacked pair of 3600 watt inverters. This allowed
for a 120/240 volt set up with an automatic
generator start ability. Another benefit of using an
auto-start generator is that there is little chance
of damaging the battery bank due to a deep
discharge. This type of system requires very little
maintenance on the part of the homeowner.
The power panel (the inverters, charge controllers,
and circuit breaker boxes) was mounted in a secure
area of the garage. The solar array was configured
for a higher voltage (100 volts) due to a distance
of 250 feet, from the array to the power panel.
Because of the higher voltage and lower amperage of
the array, a small diameter wire conductor was used
without significant loss of efficiency.
System Specifications:
-
2550 watt array using fifteen Sharp 170 watt modules
-
Sixteen 360 amp hour batteries (L16) operating at 48
volts
-
Outback 7200 watt stacked inverters operating at
120/240 volt
-
Mx 60 Charge controller
-
18 Kw diesel generator with auto start on demand
Recommendations:
During the site analysis and design Apex Solar made
the following recommendations for Mr. Cooper’s
system:
-
Radiant Floor Heating. The original home had been heated
with a wood-burning stove. Mr. Cooper wanted to
update this with a more modern heating system.
Apex Solar recommended a radiant floor system
because of the low energy demand of the radiant
floor water pumps and the ability to heat the
water with a solar thermal panel and a gas water
heater backup.
-
Fluorescent light bulbs. This
included fixtures not normally associated with
fluorescent lights such as recessed can lights,
chandelier lights, and outdoor lighting. With
new advances in the availability of receptacles,
bulb shapes, and colors, the fluorescent bulb
can match almost all current incandescent bulb
styles.
-
Other appliance recommendations.
Apex Solar recommended laptop computers over
desk top computers due to the significantly
lower power draw. Also, Apex recommended that
all office equipment be placed on power strips
to allow for shut down of “phantom loads” at the
end of the day.
Results of Installation: This system was installed in five days and has been
operating maintenance-free for over 8 months. |
