Friday, 1 March 2013

Fans for power conditioners

You really have to read the small print. 

The rating of the Power conditioners is 4 kW, but this is at a temperature of 30 degrees. It drops to 3.2 kW when the temperature goes up to 40 degrees. 

This is a big deal if we have two power conditioners, which we do, and the panels are producing over 8 kW, which they will on many sunny days. 

I don't have much solid data at hand on the hourly generation. I started off copying it from the display panel, but gave up after about three weeks and have just been recording the daily figures since then. The 22 days of recorded data, of which 16 were sunny, and what I see when I walk past the display panel, show that it's rare for the power conditioners to be producing more than 7kW. Of the hours we'd expect maximum output, we got 7.2 kWh per hour once, but the normal maximum is about 6.9 kW.  

Since the temperature of the power conditioners mostly depends on the heat they put out, and the heat they put out is a percentage of the electrical power going through them, they are unlikely to deliver 4kW. 

If they could be cooled, we may get an extra half kilowatt out of each power conditioner when it is generating a lot. That could be for four or five hours on a good day. Maybe an average of two hours a day. 2 kWh, 100 yen in the bank every day. 

Cooling them is easy. You can put a fan in front of them. The room with the power conditioners gets hot, and the thermometer in there shows that it's over 30 between about 10:30 and 16:30, but circulating the air is going to cool the machines down. 

I put a fan in there the other day and watched the numbers on the power conditioners go up from 3.2 to 3.99 while they were blown on. 

The fan is going to use electricity, of course, but probably only around 20 Watts. Fixing it to a timer to run between 11:00 and 16:00 each day would cost us 100 Wh, but this is only 5% of the extra 2 kWh we could make, so we'd be winning. 

Of course we have to offset these financial savings with the capital investment. We may need to get another fan since the time we want to cool down the power conditioners coincides with it being hot downstairs when we want to circulate air in the house. 

It would be really good to have a fan connected to the DC output of the panels, that would start working when it got to around 4kW. This is part of a broader desire to take power straight off the panels without sending it through the power conditioner, for example in running a heat pump for hot water. I don't think it would be very difficult technically, but I'm really not sure whether I'll be able to find anyone interested in doing it.