Archive for » March, 2009 «

Saturday, March 28th, 2009 | Author:

California Power Companies are obviously feeling the heat. Grid-tie systems are an extremely attractive option for those looking to go solar. When you take batteries out of a PV system you eliminate a costly component that requires maintenance. In turn, this eliminates the need for charge controllers, a large amount of wiring, disconnects, fuses, etc. This makes the cost associated with going solar plumet to a much more manageable level making solar financially available for most people. When we “do the math” on grid tied systems, we usually find very near term investment returns with the Net Metering laws on the books. For those of you that don’t know, grid tie systems offset our power consumption by spinning our meters backward whenever there is surplus power from our panels. In Net-metering states, California for example, the kW’s we send back into the grid are worth the same as the kW’s coming in. The power companies are trying to tax our use of the grid to bring the price they pay us for our power down to their “avoided cost,” the price they pay for power, instead of what they resell it to us for. This would negate the whole purpose of Net Metering and is only a ploy from electric companies to maintain their pollutive monopoly. The verdict is in, CPUC Rules Against Solar Tax! This is obviously a huge win for renewables. Visit SEIA

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Sunday, March 22nd, 2009 | Author:

If you own an old Trace Sun Tie, it’s time to turn that puppy in. Chances are, if you have one, you have had a miserable experience with it. One of our customers is on his third STXR which now seems to working fine. Trace’s Sun Tie inverters were recently de-UL listed for problems with islanding, whereby when the grid went down, they still continued to push power to the grid. This is dangerous for the line workers. This has since been fixed and they’re back on the U.L. Trace must live by the third-times-a-charm rule because the new one, as far as I can tell, works pretty well. The new units have MPPT which has successfully lengthened daily up time and power production.

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Monday, March 16th, 2009 | Author:

Max Power Point Tracking is a new technology that has the eye of all the major players. SMA Sunny boy inverters have it, OutBack has it in the MX60 charge controller, RV Power has it and obviously, so does Trace. MPPT is a digital slight-of-hand that trades off voltage or amperage in order to get within the operable range of the inverter. Based on IV curves we know that shading does not have a great affect on the voltage output of a PV panel, but it greatly affects the amperage output. We also know that cell temperature barely affects amperage but can greatly affect voltage. Based on this observation, with software and electronics, we can adjust the output of our panels to meet the minimum or maximum operating levels of our components. The blue area in the graph above represents the acceptable operating range of a given Sunny Boy inverter. In the case shown, the minimum operating voltage of the inverter is not being met (denoted by the “O”), so MPPT technology sacrifices amperage to pull the voltage up into range (denoted by the “X”) so that we can now get power production where we other wise wouldn’t.

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