Monday, November 20, 2006

PV System Upgraded

My PV system was very useful during the most recent grid power failure, but at the same time I wished that it could have done more. As a result of that experience I decided that the next upgrade would be a better inverter. My present inverter, a 600-Watt modified sinewave type, does a great job running lights, fans, and charging the cell-phone batteries, but has its limitations. Here is a list:

It is not powerful enough to operate my microwave oven and other large appliances.

It doesn’t provide enough starting current to run a small refrigerator.

It causes buzzing in the sound when I run a radio on it.

It causes streaks in the picture of a TV powered with it.

A timer motor runs fast, making it useless as a timer.

I’m afraid to connect expensive devices to it, fearing that it may damage them.

To overcome these limitations, I’ve just ordered an Exeltech 1100-Watt sine wave inverter. I chose the Exeltech because it seems to be more rugged and dependable than others I’ve considered. And, because it’s made in the USA, I suspect that it will be quicker and easier to get it repaired if I do experience a problem. With the Exeltech, I’ll be able to run almost any appliance I can think of.

In choosing an inverter I first had to assess my needs, and then find one that meets those needs while staying within my budget. In the event of an extended grid power outage a typical load on the system will be:

Three compact fluorescent lights 45-Watts
Small chest freezer 90-Watts (When the compressor runs)
Small refrigerator 115-Watts (When the compressor runs)
One fan (medium setting) 30-Watts
A radio 5-Watts
Total 285-Watts

I’ll also be able to use other appliances, such as a microwave oven or a vacuum cleaner, at the same time. Since the microwave is rated at 750-Watts, the total power supplied by the inverter will be 750 plus 285, or 1035-Watts. The Exeltech inverter can handle up to 2200-watts for a few seconds, so a high motor starting current surge from the freezer or refrigerator should not present a problem.

With the exception of a few high-power devices, I’ll be able to run multiple appliances at the same time. For example; if I want to use the microwave, I’ll have to avoid using a vacuum cleaner. Of course I’d have preferred a bigger inverter, but when considering the cost, I decided to put up with a little inconvenience.

Daily needs can be calculated by multiplying Watts times Hours. My short-term goal is a system capable of supplying 1450 Watt-hours. My fully-charged battery bank can provide that amount of power for a day, but my solar panel array is not big enough to keep the batteries charged in the event of a power outage lasting more than a day. I plan to add solar panels next year to overcome that limitation. Eventually, I’ll add even more panels so that my system can be used for heating or cooling.


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