Sunday, April 18, 2010

PV roof like Usain Bolt! 1000kWhr

17 April : The Photovoltaic roof took a long time to crawl to 500 kWhr because it was Winter, but now we are in April, it has charged to 1000 kWhr, and crashed through that target like an olympic sprinter, with a monster sun-day of almost 21 kWhrs in one day!

Meter stuck?
  This was also a test of our house meter, and I am very annoyed about something that I hoped would work for us... but it seems I am going to have to make some phone calls next week.
   I had fondly imagined that somehow our house electric meter would work in reverse on good days, so that we get credited for power we generate through the saving on reversing the meter. The OfGem meter correctly shows what is being generated, and we hope and presume that it goes out to the grid - but through what cable I don't know. The actual house meter just locks when stuff is going out, so for example, while 20kwhr was generated by our roof, the house meter just stuck at 26632 at 3pm. It didn't move back, but while the sun shone, did not move forward either until after sunset.
  I spoke to my friend Karina Wells later in the day and she says that when her roof is doing well, her net consumption for the day is down to 1 kWhr. That is impossible for us, because even if the house uses none in the day there is still the baseload of the house, and evening heating/ lighting/ power - so it can't be less than 7-8 kWhr in a day. We used 7 kWhrs in evening cooking, lighting, power, so the day ended at 26639.

18 April : Another sunny day and another chance to test the meter. The reading was 26639 last night at about 2am (yes, I am nerdy enough for the test to have checked it at that time). The reading at 2pm today, 12 hours later, having generated 17 kWhrs from our roof is still 26639. It seem that at this time of year, the only time the meter moves forward is at evening/night time.

19 April: PS, I have had a reply from our installer, and the new generation of meters are designed only to show the IMPORT from the grid, so will remain static when we are generating. The balance between what we use ourselves and export is based on a rule of thumb of 50%-50% over a year (at the moment, we are exporting more than we use, of course). I will probably publish this answer in full in a later posting.

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