Tuesday, 7 June 2011

Roof going solar

Forty-two of the 48 solar panels went on the roof today, making up most of the 9.12 kiloWatt array. Three companies were on site this morning, although the architect didn't make it until later as he'd been out of town, and nobody from the builders came all day, as far as I can tell.  The three companies were the manufacturer of the solar panels, Caname; Rooftech, a company from Yamanashi who install solar panels; and Yamazaki, the roof-workers, who work for Rooftech. The electrician also came in at some point to discuss the connections, although the last I saw this won't happen until October when the house is ready.  I'm sure, at the very least, they could connect the power conditioner up so that everyone working on the house can use the free electricity rather than having to pay for it.

The eight people working on the roof seemed to spend a few man hours at first working out what to do as the top of the roof was 13 mm wider than on the plan, and it was about 5 mm longer from the top North ridge to the bottom South edge. They seemed to work out what to do eventually, and they started sending materials up to the roof just as I had to set off from work. I got back in the evening to see them install twelve panels and send the remaining six up to the roof ready to install tomorrow. 
I saw the carpenters working on the tricky west side of the roof a couple of days ago, as they laboriously trimmed all the rafters sticking out the side of the roof, only to find that the eaves weren't straight when they put them on. They hammered away to take the eaves off, then knocked off for their lunch. If I'd known how much trouble the west wall was going to be, we may have gone for a square house, but every time I look at it, I'm convinced it was the right decision.

Those numbers, 42 and 48 have another significance.  We reckon on around 100 kWh/Kw month. In other words, we have 9.12 kW of panel, so we can expect 912 kWh of power each month. KiloWatts represent the power, and one kiloWatt for one hour amounts to one kWh of energy. Electricity companies sell their electricity by the kWh. Manufacturers of devices that produce or consume electricity rate their products in Watts or kiloWatts.

Now, in their attempts to encourage solar power, the government has been obliging power generators to pay people with solar panels over the normal electricity rates for their electricity. There's a ten year contract and the price last year was 48 yen per kWh. Electricity companies usually charge around 24 yen per kWh. If we could sell all our solar electricity, and only use cheap offpeak night time electricity, at 9 yen per hour, then we'd get an income of over 40,000 yen per month. 

The prices drop to 42 yen this year, which represents a loss of over 5,000 yen per month. With all the delays, it was looking like we'd missed the boat for 48 yen, but I just heard that, because of the recent earthquake and disruption to the building trade, they have extended the 48 yen contracts. I don't think our delays had anything whatsoever to do with the disaster. There does seem to be an invigorated interest in solar power as a result of Japan's recent nuclear problems, and it seems likely that the government will continue or even increase their subsidies and benefits. To be honest, until now they seem to have been more interested in increasing sales for their friends in the big electric manufacturers, who happen to hold large chunks of the world share in solar, and the "eco" has been more -nomic than -logical.