Wednesday, March 24, 2010

4 KW Solar Electric

We have begun an exciting new project, a 4kw Solar Electric system. It is being installed by the capable team from Clean and Green Alternatives.  It is our hope that this system will have the same effect on our electric bill as our Reynolds Solar Hot Water system has had on our propane bill.  Our system presented some challenges to Clean and Green. Our roofs were not suitable and I did not want to use valuable orchard and garden space for solar panels. Neither did I want the panels blocking any of our rural scenery.  Therefore I had them squeeze the system behind our garage and put it on tall poles to avoid any shadows.  This changed the engineering requirements dramatically, requiring much stronger poles and a whopping 4 yards of concrete, poured into 3 foot diameter foundations.
This required a large concrete truck.  Too large to get behind the garage. Therefore, a mud buggy was required, too.
It took about 9 trips to transfer all the concrete to the worksite. A little over a yard went into each of the 3 foundations supporting the nearly 1,000 pound support structure.

 The support, ready for panel installation:

The panels, waiting for installation:
Sixteen 280 Watt Grape Solar panels.

The panels went up in less than a day. It is an attractive and nicely engineered system.  There is 330 square feet of panel area.  The combined weight of the panels is 890 pounds and the racking is around 300. The poles add a few hundred pounds more, and they are set in 16,000 pounds of concrete.  It becomes easy to see why these systems remain expensive.
  The inverter, a PV Powered 4800 Watt, is a solidly made unit which can produce power even when the panel output is very low.  I've observed it making as few as 50 watts before shutting down as dusk.

True, 50 watts is insignificant. But the system's low light efficiency pays off on a cloudy and foggy day like today. The system produced on average 400 watts under a solid overcast, and 4kwh for the day.  That alone would be enough to reduce our electric bill by 10%.  But of course a solid month of rain would be rare, and in normal weather the system should produce 500kwh/mo.
The early results are encouraging.  The system has been running 3 weeks through a variety of weather conditions. It has averaged 19kwh/day, which equates to 570kwh/month.  That should result in us having  electric bills near zero for 2 - 3 months each year and substantially reduced ones for the remainder.
PV Powered has a great website which monitors the inverter and records the output. You can then download a variety of performance data, like the chart on right.  It also monitors for any problems that might develop.
As we accumulate more data, I will update the results here.  Update.  I increased the size of the system, click  here to see it.

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