Solar data and experience of last 45 days on Solar system

Energy meter for daily consumption was installed on 13th April and hourly generation and consumption was recorded from that date onwards. The main observations are:

1. Average daily generation was 6.3kwh. For a 1.5kw solar panel capacity this works out to 4 hours of bright sunshine per day. Average consumption was 4.7kwh/day

2. During this period, the zenith time (i.e. the time when the sun is exactly vertically above – this time is a function of your location and the month of the year) was 12.30pm. This meant that peak generation should be around this time (if the clouds don’t interfere). 

3. The maximum generation rate in this interval was 1.3kw and for a 1.5 kw installed capacity, I think it was a reasonably satisfying results. On two occasions the value was 1.2. Majority of days it was 1.0

4. Even a slight cloud cover perhaps affects the generation as reflected in fluctuation in generation rates in these time intervals.

5. Unfortunately quite a few days were cloudy and hence the average peak generation (between 12 noon to 1pm) was 1kw

6. Cumulative generation for the first half of the day i.e. till 12 noon to 1pm interval was 3.7kwh. With daily generation of 6.3kwh meant that in the second half the generation was 2.6 kwh only. Most days in the evenings especially after 3pm the sky would get a good cloud cover (even though the rain Gods did not shower blessings on us) 

7. We were out of station from 29th onwards for about 5 days and during this period only our fridge was on. Average generation per day during this period was 5.4kwh/day and our consumption was 2.2kwh/day. So the average consumption for a 300 L capacity fridge is around 2kwh/day – which matches with their specifications of approximately 100watts.

8. After our return, the generation has been very low since most of the time the sky is overcast. In the last 10 days that we returned, the generation has fallen to 4.5kwh/day but the consumption was 4.8kwh/day

9. Cumulative units generated since 13th April has been 173kwh and our consumption is 142 units, difference between generation and consumption comes to 31kwh.

10. During this period, 40 units was drawn from the grid out of which in the last 10 days 25 kwh was drawn. So if we add 31 units to 40 units drawn from the grid, the gap increases to 71 units. This comes to more than 3 units per day. This is the energy consumed by the inverter. At the generation level of 6 units a day if the inverter takes 3 units (which comes to 50% of the generation), one has to really get from the manufacturer what is the power requirement for the solar inverters and incorporate into the design. 

11. Our average consumption prior to installation of Solar system was 7 to 8 kwh/day which has dropped to 4.75 units a day. I was wondering how we were able to bring down the consumption by almost 30 to 35%. After looking at the energy consumed by the inverters, I conclude that our earlier UPS must have been consuming 2 to 3 units a day!!!. Now the consumption is metered from the output of the inverter and therefore does not include the inverter load whereas earlier the Board meter was measuring the power supplied to the house hold which included the UPS.

12. I have not worked out the cost of generation yet. I want to assess the monthly generation over longer period to project what will be the yearly generation to estimate the cost of generation.

13. Because of unsteady atmospheric condition i.e. clear sky, partly cloudy, overcast sky etc, it is difficult to correlate generation with previous day’s consumption.

This much for now. Hope you will find these observations interesting.