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A group of 5 panels

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My battery bank

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The Electronic Center

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Panels on the roof

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and on the patio roof

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Each 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 27 years.

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.

California's Rebate Program

The state of California adopted a buy down program for small alternative energy plants smaller than 10KW.  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 pay for.

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 of 10m2.

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 Utilities

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 here .

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 some. 

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!

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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!

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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

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 completely charred.

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 gets warm.

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 not needed.

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!

Graph Showing Breakdown of Resources


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