News and Views

From my kids accomplishments, to my heretical perspective of the world

News and Views header image 2

We have power!

December 21st, 2011 · 12 Comments

Our solar energy system finally became active today. SRP (the local power company) was here at 9:00 am, and did the final connection.

Since then (it’s now 3:00pm) we have generated about 24 kWh. Of that, about 14 were sold back to SRP, and we have used about 10.

They installed a new meter that was set at zero this morning. It now reads 99986, showing that net energy has flowed out. I expect that after heating the house tonight with no sun shining I will wake up and find the savings erased. I noticed that when I turned on the heat pump, the direction arrow reversed, showing that we don’t generate quite enough to run everything else in the house and the heat pump too.

Peak energy during the day was 5100 watts; not bad for a winter day with the sun lower in the sky. Theoretical maximum is 8000 watts, but I will never see that due to inherent losses in the system.

I’ll publish some data after it has run for a couple of days.

Tags: Computers, Tech & Science · Family Updates

12 responses so far ↓

  • 1 Daryl // Dec 21, 2011 at 3:57 pm

    Just realized that tomorrow is the winter solstice, the shortest day of the year. That will also be my first full day of usage. It should only go up from here, as the days get longer.

  • 2 Richard // Dec 21, 2011 at 5:29 pm

    Cool! Looking forward to hearing the results as the months go by.

  • 3 Donna // Dec 21, 2011 at 5:51 pm

    Cool! I mean, warm! At least until April or May. Then cool!

  • 4 Daryl // Dec 22, 2011 at 10:42 am

    Darn it, partly cloudy today, not making as much power.

  • 5 Don // Dec 22, 2011 at 11:39 am

    Lukewarm! I’m looking forward to seeing how this works over the next few months.

  • 6 Daryl // Dec 23, 2011 at 8:24 pm

    As of tonight, the 3rd day, I have generated more than I have bought from SRP (78 vs. 69 kWh). That means that I am supplying more than half my own power. And yesterday was partly cloudy; I only produced about half what I did today.

    The contractor said that in the spring and fall, when I am not using any heat or air conditioning we may occasionally develop a surplus. But we shouldn’t expect it this time of the year.

  • 7 Richard // Dec 24, 2011 at 6:01 am

    Have you changed your usage habits any, even subconsciously?

  • 8 Daryl // Dec 24, 2011 at 11:09 am

    I probably have changed my usage a little, though not intentionally. I think about it each time I raise the thermostat, mainly, but I’m trying not to change.

    I do know that based on previous years I’m using about the same daily energy, so the change isn’t extreme.

    Watching the meters, the heat pump seems to be the only thing that requires energy from SRP, during the day when we are getting sunlight. When the heat pump is not on and the sun is shining, we are always sending energy out.

    Last night was below freezing, and I can see that we consumed quite a bit. I’m not sure if it will make up the difference by nightfall; we may still be less than half by the end of the day.

  • 9 Daryl // Dec 24, 2011 at 8:21 pm

    End of the 4th day, and still ahead. PV has generated 110 kWh, while SRP has contributed just 96.

    I’m always ahead in the evening, and behind in the morning.

  • 10 Richard // Dec 25, 2011 at 5:59 am

    My system works the same way. Now, if we could just get some decent lunar panels……

  • 11 Daryl // Dec 25, 2011 at 12:58 pm

    Here’s a graph of power generation during the day. Note how it’s a steeper rise in the early morning than the fall in the afternoon. That’s because it faces south east, and catches the sun as soon as it rises. In the afternoon it is still generating power even when there is no direct sun, just from the scattered atmospheric light.

  • 12 Richard // Dec 25, 2011 at 8:37 pm

    Believe it or not we have seen a few (couple) watts generated by street lights. It’s amazing how few photons it takes to knock off an electron or two.