Tuesday, 5 June 2012

Not my fault

I wrote to the solar panellists about the excessive limitation of our electricity and got back a letter basically blaming the electricity company. They said that the situation in the local grid can effect the electricity going out of the house. 

The way the wiring is set up, the electricity is going in or out of one line, and will only flow from a higher voltage to a lower voltage, if my understanding of electricity is correct. I may be confusing it with heat only being able to flow from a hotter body to a colder body, but I think the principle is the same even if the physics is different.  Thermal conduction and electrical conduction share some features and characteristics, but the so does bus conduction. Different things are happening at the micro, or nano level.

So it's possible that the voltage on the lines in the neighbourhood is higher than the voltage that we are trying to produce. Although mains electricity is rated at 100 Volts, it's actually 101 V plus or minus 6, so somewhere between 95 and 107 V.  The power conditioners are set to not exceed 107 V. The power conditioners should be set to produce electricity at as high a voltage as possible, and if not over 107 V, then not much under. If they were producing at 105 V, and the grid voltage was 106 or 107 V, then I think no voltage would be flowing out. 

They suggested that something like this is happening, and that I should contact the local electricity company asking them to investigate the local voltage, to find out if there are any unusual conditions.

I wrote back to them saying that I was reluctant to write to the local electricity company without further information. I explained my understanding of electricity that if the voltage of the local grid is higher than the voltage coming out of the house, then no current will flow and we'll supply zero power.  I have never seen this situation, although frequently seen it producing 5 or 6 kW, and the display indicating that the power conditioners are limiting the voltage. 

They also said that the power we are not sending only amounted to 1000 yen or so in March and in April, and whatever we do, we are unlikely to get the time it is limiting power down to zero.

I still feel to have been a little misled when they told me that two 4kW power conditioners would be fine for our 9.12 kW solar array. This was perhaps my fault for assuming that 4 kW was a rough rating, in the same way that 100 volts could be anywhere between 95 and 107 or our 9.12 kW array is actually 9.34 kW when you add up all the measured ratings of each panel.