The scientific community has reached broad consensus that global warming is happening and that humans have caused it. We must lower our CO2 levels to around 350 PPM. The impacts of climate change are so wide ranging that they could equally
be called a major economic, military, agricultural or social justice issue. We must all live on this small planet. We are all interconnected. We need to act responsibly.
Future
Solar is on track to deliver 50% of energy in the US, for all purposes including plug-in vehicles by 2042 according to Green America's Solar Catalyst program. Last year, both the US and the European Union added more power capacity from renewables than from conventional sources.
Your PV array should not be shaded. The shading of a small part
of a PV module greatly reduces output from the entire array. After
installation, the area must be maintained to prevent weeds, leaves or
tree branches from shading the array.
Controllers
Charge controllers are included in most PV systems to protect
the batteries from overcharge or excessive discharging. Excessive
discharge will cause premature battery failure. Over charge can
boil the electrolyte from the battery and cause failure.
Module Mounting
There are many choices for mounting modules. They can be incorporated
into the outer structure of the building to form the roof or walls.
They can be mounted at ground level on a pole or on top of a roof,
with a fixed, seasonally adjustable or tracking array.
Tilt Angle
For a fixed array the tilt angle of the array should equal the
latitude of the site. If the array can be adjusted it is recommended
that it be adjusted to: winter = your latitude +15°; spring
and fall = your latitude; summer = your latitude - 15°
Hybrid Systems
When any power source is integrated with a different type of
power source, the result is a Hybrid System. A hybrid system could
be PV - Diesel Generator; PV-Wind or whatever combination makes
sense at your site. A battery bank can be used to buffer the variability
of sunlight. During times when the load is larger than the output
of the PV array, the battery bank the auxiliary source make up
the difference.
Advantages of PV Energy
1) High Reliability - no moving parts, 25 yr warranties
2) Environmentally Friendly - no fuel, fumes, radiation, cooling
water
3) Modular - can be used to power watches or Multi-Meg Watt size
projects
4) Low Operation and Maintenance Costs
5) Grant or tax money from utility or Federal government
6) Save money on utility bills
7) Energy Independence
8) Hedge against inflation
9) For our Kids and the Planet
Powering Heating Loads
PV can power any resistance heating load, but not at a price
you are willing to pay. Use solar thermal, passive solar, propane
or natural gas.
Solar Water Heating
Very good for domestic hot water, pools, radiant floor or industrial
process needs. Solar thermal can even be used to power ammonia
based refrigeration cycles. We don’t do this type of work,
except control or power wiring for pumps, etc.
Building Integrated PV
Architectural quality should not be judged by purely formal
aesthetic criteria. The success of any building must also be judged
by its environmental impact and energy efficiency. Architects
and builders are using PV materials on the roof or south side
of large skyscrapers and smaller structures to offset some or
all of the electrical power needs of the building, (and or) to
feed back to the grid during periods of excess generation.
Track or Not
Tracking can increase energy production in the summer as much
as 50%. It is not very helpful in winter because the sun is so
low on the horizon. Tracking is generally used in water pumping
applications, which have a peak summertime need. For home systems
we recommend a fixed mount and more panels.
Wind
Location | Location | Location
At any remote site with a wind speed greater than 10 MPH average annual wind speed, small wind turbines produce power at less cost than gasoline or diesel generators. In many location,s solar and wind resources complement each other with sun in the summer and wind in the winter. We've found that these "hybrid" systems perform even better when coupled with a small back-up generator to reduce the amount of battery storage required. Wind machines can also be used to backfeed the grid. Doubling wind speed does not only double the power it increases by 8 times. Experience has shown that the entire turbine rotor should be at least 30' above any obstructions within 300'.
Most sites in the Northwest do not have a high enough average
annual wind speed to make it worthwhile to install a wind turbine.
However there are some excellent sites; please visit www.energyatlas.org
to get an idea of the potential for wind power generation in your
area. Generally speaking you must have an average annual wind
speed of greater than 10 mph to make an installation worthwhile.
Batteries
The batteries used in stand-alone PV systems should be deep
cycle heavy-duty types. Lead is a soft metal so often other elements
such as antimony or calcium are added to strengthen the plates.
Lead-antimony types will withstand deeper discharge cycles but
have higher watering needs. Lead-calcium types are used where
fewer deep discharges are anticipated. Their lifetime is shorter
than for lead-antimony types. Any battery should be considered
dangerous, particularly to children and animals. Access should
be limited. NiCad or Lithium Batteries are sometimes used in extreme environments.
Inverters
Grid-tied without batteries, Grid-tied & battery based or Battery based only, inverters are necessary if you want to run AC loads. Inverters
change DC to AC, (remember PV arrays produce DC electricity).
Batteries store DC electricity. There is tremendous variety among
types of inverters on the market. Some of the characteristics
that should be considered are: output waveform, power conversion
efficiency, rated power, duty rating, input voltage, voltage regulation,
audio and RF noise battery charging capability, capability for
parallel operation with utility grid.
Ghost Loads
Typically these are small wall cubes that are plugged into outlets
that convert AC to DC for electronic equipment. These contain
small transformers which can waste incredible amounts of power,
because they are left on 24/7/365 days a year.
Solar Modules-Power Characteristics
Four factors determine any PV modules output
1) solar irradiance - see “insolation”
2) efficiency of PV cells 8 - 20%
3) load resistance
4) cell temperature
Sizing a System
Insolation
The availability and amount of sunshine (insolation) must be
estimated because it is unlikely that long-term data is available
for your site. The term peak sun hours” is defined as the
equivalent number of hours per day with solar irradiance equaling
1000 watts/sq. meter. Kilowatt-hrs per square meter equals peak
sun hours. In other words, 4 peak sun hours means that the energy
received during total daylight hours = the energy that would have
been received had the sun shone for 4 hours with an irradiance
of 1000 watts/sq. meter.
On a bright sunny day in Seattle the irradiance striking the earth
will be about 1000 watts/sq. meter. In the SW United States the
levels regularly are above 1000 watts/sq. meter. In some mountain
areas readings over 1200 watts/sq. meter are routine. Maximum
instantaneous valves of 1500 watts/sq. meter have been recorded
when puffy white clouds focus the sunlight. These high levels
seldom last for more than a few seconds.
Power Consumption
The load or loads you will be powering and the length of their
use is extremely important information. Without this information
we can only guess and that can cost you a lot of money.
Reducing electrical consumption through energy conservation, efficiency and thoughtful building practices improves the useful work that each kilowatt-hour can provide. It is pointless to waste expensive PV or small wind generated power on inefficient appliances. As a general rule of thumb: "For every $1,000 you spend on energy efficient appliances, you will save $3-4,000 in expenses you would have needed to spend to generate and distribute power to those older, energy inefficient appliances." Renewable Energy Systems are long-term investments and should be viewed as such.
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