from energy efficiency
and solar strategies
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from energy efficiency and solar strategies |
When solar energy collecting devices are integrated into the south facing
wall and roof of a builing and are coupled with passive solar design
strategies, solar energy becomes an economic alternative to centralized
power generation. Quickest payback comes from conservation and energy
efficent design, followed by savings through the use of solar heated water
and solar driven hydronic heating, and, finally, integrated photovoltaics.
However, even if a building is designed and constructed with the least
environmental impact in mind, when it comes to air pollution the automobile
remains the real culprit. In a rural area, transportation uses twice the
energy used in housing but causes about 7 times the air pollution because
of its total reliance on petroleum. An electric car recharged by an
integrated PV array can have the most positive effect on air quality.
Taken in isolation each of these direct solar strategies would have
marginal success, but used in conjunction the environmental quality and
economic savings compound.
The following is an economic analysis based on real functioning examples.
The cost savings are based on a 30 year life span of most solar hardware
and compared to the local utility's estimated energy costs for an average
home.
Conservation and energy efficient design
Solar hot water
Solar driven hydronic heating
Integrated Photovoltaics
Crystalline, poly-crystalline, and amorphous are the commonly available
kinds of photovoltaics. Crystalline and poly-crystalline are about 14 to
18% efficient in their conversion of sunlight into energy compared with 4
to 10% efficiency for amorphous panels. However, the overall efficiency of
thin film amorphous silicone panels, when compared to stationary
crystalline panels, is increased by their ability to convert indirect or
diffused light. This makes the amorphous panels very useful in areas with
extended periods of overcast skies.
The total income generated by 30 years of living in an efficient solar
home is $75,000.
The industrialized world spends more money on transportation than on
housing. It costs the nation $95 billion a year to treat air quality
related health problems, according to the American Lung Association.
Transportation's total reliance on petroleum causes 80% of that air
pollution. When alternative fuels, such as wind, solar and hydro, are used
to recharge electric vehicles the need for petroleum use is eliminated.
Simple conservation measures mean financial savings. A switch from
incandescent to fluorescent light bulbs can save $5 to $15 a month (at 12.5
cents/kwh). Natural lighting can save another $20 a month. Using a
clothesline instead of an electric dryer for the sunny half of the year can
save $15 per month. Purchasing an energy efficient refrigerator can save up
to $18 a month. A front load clothes washer can save $6 per month over the
standard top loader. A well-insulated building with full southern exposure
and well-placed thermal mass to store direct gain, can save $70/mth of the
energy needed during the heating season. Natural ventilation instead of air
conditioning during the summer months can save $50 a month during the
cooling season.
The savings from conservation measures minus their initial purchase and
installation cost amount to $18,000 over a 30 year period.
An electric water heater can account for $50 per month on the utility bill.
Simple solar hot water heaters can be installed for as little as $1,000.
In most cases a convection or thermal siphon system - which requires no
pumps or energy - can be used to satisfy domestic hot water needs. Backup
during sunless periods is provided by the addition of coils in a wood stove
or an auxiliary gas heater. The savings from a solar hot water system
minus the initial installation and hardware cost is over $10,000 for a 30
year period.
The south-facing walls of an energy conscious home are the best place for
controlled solar gain because they receive more energy in the winter than
they do in the summer. Solar gain in the summer can be totally avoided
with the addition of overhangs. Flat plate collectors can take the place
of siding on the south wall, along with windows, which provide direct solar
gain. The collectors heat liquid which is circulated through radiant
heating pipes embedded in the floor. This type of solar driven hydronic
heating coupled with direct gain and good insulation can save another 30%
on the space heating. This compares to a monthly utility bill of $200 for
an electrically heated average sized home, and $100 for gas.
The collectors end up being less expensive to purchase and install than the
furnace that would normally drive the hydronic heating system. Assuming the
average heating season is five months, up to $1,000 can be saved per year
and $30,000 over the 30 year life expectancy of high quality flat plate
collectors and radiant floor.
Typically a roof's main function is to keep the rain out while maintaining
a comfortable indoor temperature. When a photovoltaic material is used as
the roofing material, the roof takes on a dual function by converting the
sun's rays into electricity. If the photovoltaics are 10% efficient about
400 sq ft. of roofing area will satisfy the electrical needs of an average
energy efficient home.
Another advantage is their environmentally friendly manufacture. The thin
film is applied without any waste, while significant material loss results
in the manufacture of crystalline panels. The energy consumed in the
manufacture of thin film amorphous panels is recuperated in as little as
two months of use, as opposed to up to 5 years to produce the energy used
to manufacture crystalline panels. Because the thin film amorphous material
adheres to materials that also make good roofing, like metal, glass and
ceramic, it becomes versatile as a building material.
Uni-Solartm, United Solar Systems Corp, with its corporate headquarters in
Troy, MI., is laminating thin film amorphous material to standing seam
metal roofing that could revolutionize home construction. The 20 foot long
standing seam metal roof panels produce 800 watts per 100 sq ft.
Steve Heckeroth
Homestead Enterprises: Solar Design and Renewable Energy Products
Box 151
Albion, CA 95410
phone/FAX 707-937-0338
EMail Us! solar@renewables.com
