day more energy falls to the Earth from the sun's rays than the total
amount of energy the planet's 5.9 billion inhabitants would consume in
Only in the last few
decades-when growing energy demands, increasing environmental problems
and declining fossil fuel resources made us look to alternative energy
options-have we focused our attention on truly exploiting this
tremendous resource. The electric rates in 2000 are a prime example of
what happens when we have energy shortages.
The graphs below show that
the US is an electric energy pig. Only ten percent of the electricity
in this country comes from renewable, non polluting sources.
The requirement for energy
in space for powering satellite systems provided a big impetus to
advance the technology. The new international space station, for
example, has over $600 million in new solar arrays.
The state of California
adopted a buy down program for small alternative energy plants smaller
Currently the program will reimburse the homeowner or business for up
to $2.50 per watt (for 2007) delivered to the grid ( retroactive to
installations from 2/8/07), or
50% whichever is less for wind or photo voltaic, PV, power plants. The
rebate was $3.00 per watt up to 5/15/01 then went up, and is now back
down as of 1/1/04. At $3.00 per watt the CEC is basically giving the
panels away for free. The rebate is due to
expire 12/31/07! The CEC ,
California Energy Commission, calculates the rebate on the true power
generated by the panels times the efficiency of the inverter. On good
quality panels this number is close to the actual power rating of the
panel. On poor units, the number can be a third less. You get what you
For my system I used BP585
panels. These are not cheap but offer the highest power per area of all
the panels. BP Solar gives an ideal power output of 85W per panel. The
state's real world output is 78.1W. This ratio is actually excellent.
Most panels are much worse. To calculate the CEC rebate, take
78.1W/panel * number of panels * inverter efficiency * $2.50/W. My
inverters are very good and have efficiency of 95 percent. Good
inverters are a lot cheaper than extra solar panels. Don't skimp here.
For my original system:
78.1W/panels * 64 panels * 0.95 * $3 per watt = $14,244 of CEC rebate.
If I had installed the system after 2/8/01 the rebate would have been
$21368. The old system had a maximum output power into the grid is
4.75KW. Again, the CEC calculates rebates on the power that can be
input to the grid. Buy quality components.
The new rebate is $2.50 for
2007, but the new solar cells have higher efficiency than when I bought
my panels. The new Kyocera 200 watt panels are 14.2% efficient. My
older BP panels are about 12%. That means that if I built my system
today, I would generate another 1.2KW for the same area. That is more
than 18% more power. Another way to look at it is that you would only
need 7.5m2 of area to generate a KW of electricity, instead
The rebate is a great idea
and necessary. Although PV arrays have dropped in price by 7:1 over the
last 20 years, they are still expensive. Good panels are around
$5.00/watt. Higher end units such as the BP585 sell for $5.40/watt or
more. Houses take many kilowatts to operate, so the panels alone can
easily cost $15,000 to $20,000. Add the cost of installation,
inverters, sales tax, etc, and the system cost is huge. Without the buy
down few people would bother with these systems. The rebate is a great
use for part of the budget surplus.
In January 2002, the state
of California passes a tax credit bill for solar systems installed in
2001-2005. This is a 15% credit of the system costs after rebates on
your tax bill. It is not a deduction but a credit on your tax bill. So,
this equates to California buying another 7.5% of your system for you
after the rebates. TurboTax has the forms built into the state return.
Other Rebates from
Check your local power and
water companies for rebates on large appliances. SDG&E, the local
power utility, has other rebates available for businesses and
consumers. For example, they offer a $75 rebate for energy efficient
washing machines. The key phrase here is energy efficient. It turns out
that the water department also has a voucher program for efficient
washing machines, too. Front loading washing machines are very
efficient for power and water but cost over $1000.
The water authority will
send you a $125 voucher at the time of purchase for SD city residents,
but you must have the voucher in hand before you buy the machine. You
give the paperwork to the merchant at time of purchase, and they deduct
the cost. It is a $125 coupon from the water department. To get the San
Diego city $125 water voucher call 1-800-986-4538. That is a total
rebate of $200 for an energy efficient washing machine. The water
department is very strapped for resources, so they don't advertise
programs much. This program isn't on their web site, yet. The program
has only been in effect for a few months. Still these programs do exist
if you dig a bit.
SDG&E just restarted
rebates on refrigerators up to $125 and other large appliances.
SDG&E also offers a built in buy down ( no rebate; the cost is
lowered by SDG&E already before you buy.) on certain florescent
lights, and florescent torchiere lamps at the local Home Depot. They
sell GE and Lights of America brands. The LOA lights are very
poor in quality both electrically and mechanically. In fact you can
dent the metal base with your thumb nail. Buy the GE branded lights.
For a current list of SDG&E rebates click
If everyone is San Diego
replaced their refrigerator, clothes washer, and dishwasher with a new,
Energy Star qualified model energy costs in the county would drop $100
million dollars. The drop in emissions from power plants is the same as
taking 40,000 cars a year of our roads. If everyone with a swimming
pool replaced their old pump motors with a new, efficient model, the
energy savings would be enough to operate 90,000 homes for a month.
Energy inefficient appliances cost you a lot more than just monthly
pain in your wallet. They affect your quality of life. Every one of
these new appliances will pay for themselves in energy saving and then
According to U.S. department
of energy and Maytag, the town of Bern, Kansas ran an interesting test.
Five years the town suffered from a massive drought. Maytag replaced
every washing machine with a Neptune front load washer. The townspeople
saved 38% on water and 56% on energy. That is a huge savings for the
environment and your wallet.
Even the Feds are in on the
energy rebates. The US DOE has a buy down for compact florescent
lights. They lower the cost of the compact florescent lights for you.
You just pay the lower cost. These lights will pay for themselves in
6-12 months. After that it is pure free money! Try is URL for more info
on the DOE program:
Why I finally installed
a Solar System
I wanted to install a PV
plant a while ago but balked at the cost. I knew that electric energy
production is the largest source of air pollution in the nation. I
liked the idea of helping out and weighed it again the initial
investment. When the electricity prices went crazy last summer in San
Diego, however, I pushed the button and had the system installed. A
$460 electric bill is a great motivator. The $3 per watt rebate
from the state really helped.
As electric rates continued
to rise I noticed my roof had some open area. So, I had the original 40
panel system upgraded to 64 panels. The roof is full, but then I eyed
the patio roof! The PV arrays had a rating of 4.8KW in full sunlight.
My goal was to have a near zero electric bill. So I added another 24
panels in March 2001. Now I should be at 6.5KW in the summer. The next
two charts are my power bills and usage over the last few months. The
April 2001 bill finally went negative!
A wet and cloudy February, 2001 made a bump in my data.
I hate rain. The air conditioner made the big jump in the June 2000
usage, even though the AC is very energy efficient. It still gets hot
in the summer. The AC comes on every day this summer, but the solar
arrays keep the net usage down. As of September 2001's bill I'm still
net negative from March through September. Even during the warmest
months of the year I'm still a net producer!
In December I receive my annual power summary. The total
bill was $249 for the entire 2001 year. I used to spend more than that
in a single month. For a good part of the year I only had two or three
arrays. With a full year with all 88 panels, I hope to get the total
power bill closer to zero. The minimum bill is $62 per year or 17 cents
per day. SDG&E has a minimum power fee per day. Alternative energy
groups are trying to get these fees eliminated.
2002 is the first year with all 88 panels running. The
yellow curve, 2003 data, runs around the cyan, 2002, data. As of
7/9/03 my power bill is under $24 for the entire year of 2003.
That is with the four ton AC running, too!
Net Metering, TOU Meters,
and Permission from the Power Company
A key step is a
net metering agreement with the local
utility. The agreement allows you to push power back to the grid when
you have a surplus. The term net means that the
utility bills you once a year for the total usage -- a total of all the
negative and positive usage months. SDG&E,
the local utility here in San Diego, will not allow you to connect to
the grid without a net metering agreement in hand. Why? When your usage is negative power goes into the grid. So
they don't want one of their crew to get killed working a circuit
they thought was deenergized while your solar plant actually kept the
circuit hot. Without the agreement you can't get
your rebate from the state. Don't worry. The folks in
SDG&E's alternative energy group are great. They are extremely
reasonable. Remember, it is important for folks with PV to spin their
utility meters backwards. They get full value
for their home-grown energy while displacing
polluting electricity. All US utilities are required to allow qualified
generating facilities to connect to the grid.
California utilities are required to net meter
qualified residential PV systems under 10 kW.
If you can get a Time Of
Use, TOU, meter. The utility charges more for power during peak hours
of the day than they do in the mornings, evenings, and weekends. This
is especially true in the summer months. I pay 17.5 cents in the day
and 14.2 in the evening. The power company does this because it costs
them more to provide power in these peak periods when the demand is
higher from business loads. With a standard meter, your charges are
averaged over all load periods.
The cool part is that your solar system puts out maximum power during
these peak hours. The result is that you put power into the grid at a
high rate and use it later at a lower rate. You save money. If you have
people at home during the day and run the AC, don't get the TOU. You
won't save any money and may end up paying more.
My system is pretty big.
Tim the "Tool man" Taylor would even be proud. Ar Ar Ar. I now have 88
panels, a full roof and patio cover, two 4KW inverters, four charge
controllers, and 2000lbs of Trojan L16, 6V 350AH batteries. Some of the
system pictures are on the left. It has a full bright sunlight rating
of 6.5KW. I do loose 10% in the winter because of the load of the
battery bank. I'm anxious to see what the new power bill after a few
weeks of full sunlight.
The PV array has maximum
power over 60VDC at lower temperatures, but the battery clamps
the voltage at 54-55VDC. Each panel has a voltage temperature
coefficient of -0.086V/C reference to 20C. I wired the panels in series
sets of four, so the total system voltage coefficient is
-0.344V/C. Systems without batteries are 10% more efficient but
can't run when the power fails. It's a trade off. Efficiency will
improve in the summer as the panels heat up and the loaded voltage
drops on each panel. On a hot day the panels will rise at least 17C
above the 20C test temperature. This temperature rise drops the total
panel voltage by almost 6V.
In March of 2003 I changed
two of my four charge controllers to a switching power supply type.
These convert the 60+ volts of the arrays to the 54 volts or so that
the batteries want but at a higher current than you would get with the
older charge controllers. These two arrays have 20 panels each. With
the new controllers they produce almost the same current as the two
other arrays with the old controllers and 24 panels each. I get about
10% more power from these two arrays. The new controllers cost more
than the simple, older type. However, they cost much less than the four
or five solar panels of extra power I wasted before. Because of the
temperature effects noted above, the efficiency boost will be even
larger in the winter.
Shown below is a block
diagram of the home system. The inverters now talk to a PC to provide
real time data of output current and total AC power.
Make sure parts are up to the task
In January of 2004 one of my inverters started to act a
bit odd. The inverter wouldn't push current back to the utility and had
a fixed load. After some measurements I found that the connection to
the inverter's input wasn't there. It is hard to push power back into
the AC line when there is no connection.
I poked around and found that I couldn't remove the AC
disconnect switch to the house's power panel. It was stuck. I pried it
apart with a screw driver. Look what I found.
The connectors got hot and melted the supporting
plastic. When that happened the connection to one of the inverters
opened up. You can click on each of the two photos to see the up close
and personal damage. Both sides had considerable damage. Only one side
failed completely, although the other would have shortly with all of
the current flowing on one side. The contact metal is dead soft now and
Although this disconnect has a 60A rating and the loads
are never more than 35A, the contacts had poor corrosion protection.
The heat generated can be huge when the current is 30+ amperes. The
contacts must be secure and completely clean. The new switch uses
heavy, silver plated contacts and plastic that will not melt when it
Do I need batteries?
Batteries are big, heavy, and add a few dollars to the
system cost. Are they really necessary? If you only want the
maximum power from your solar system at the lowest cost, batteries are
Using a special version of the inverter that runs
without batteries results in a simpler and more efficient system. The
batteries, charge controllers, battery disconnect circuit breakers, and
secondary circuit panel are all eliminated. The special inverter also
has special software, power tracking software, that optimizes the
system for maximum power from the panels. With a battery system the
voltage of the panels must be larger than the voltage of the
batteries. Otherwise you can't charge the batteries. In English your
system must use sets of four solar panels in series to guarantee that
the batteries are always under charge under all conditions and
temperature. Without the battery restriction your system can use three
panels per leg. System installation and wiring costs are reduced. The
inverter can use more of the useful power from the solar panels. You
also don't have to deal with a big battery box in the garage. As stated
earlier, you do loose ten percent of your power in the winter time with
batteries in the system.
The downside of no batteries is no power when the
utility grid fails. Your lights will go out if your power company fails
-- day or night!! The inverter needs the power company to synchronize
it's output energy. If you have a power failure, even in the day when
your solar plant is cranking out energy, the inverter looses synch and
shuts off. A battery backed up system doesn't have this problem. If the
power fails the battery acts as a buffer for the inverter. Your lights
stay on day or night.
Below is a map of solar radiation strength for the US
for objects directly facing the sun. California is a great state to be
in for solar power, but it isn't as good a Arizona. Don't bother with a
solar system in Alaska or Seattle!
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