But such data is scarce so it's always a high point for me to come to the end of my 'accounting year' and be able to present my figures.
The 'accounting year' I use runs from October 1st to September 30th so today is the day I have been able to wrap up the figures for the past 12 months. Presented graphically as a cumulative plot of kWh's generated the results look like this:
...and the same data presented as a daily plot showing generation on each day of the year, the results look like this:
Both plots show data for this year (purple) and for the previous three years.
Though the figures for hydro generation are interesting enough in themselves, many very small hydro installations will be coupled on the same premises with a small solar installation, and it's nice to be able to see how the one compliments the other. Here then are the corresponding graphs for my 3.3 kWp PV which has been operational for only two years:
It doesn't need a magnifying glass to spot some of the comparisons to be made between the hydro and solar yields:
- solar is hugely variable on a day-to-day basis but the cumulative plot in one year follows almost identically that of the previous year; hydro by contrast has almost no day-to-day variation (a step change occurs only when a nozzle change is made) but the cumulative plot lines are widely divergent from one year to the next.
- the yield from hydro does well from November to May, whilst solar does well from March to September; late October is the time when total 'domestic generation'(i.e. the daily sum of the two) is at its lowest.
- on the evidence so far available, the total per year for my domestic generation will lie between 5800 and 7200 kWh.
This last bit of information, i.e. generation being between 5800 and 7200 kWh/year, has been a key driver in my exploring 'battery-on-the-wall-storage' at home. Our domestic consumption of electricity is about 6000 kWh/year but because cooking (our heftiest use) always takes more power than is being generated, we end up having an annual take from the grid of about 1700 kWh. I have been exploring whether it might be feasible to reduce this by storing domestic generation into a battery when there is a surplus, - a few hundred watts at any given moment but over several hours, - so that it can be used for cooking when the need is for 3-4 kW but for a short time only.
And a 'battery-on-the-wall' offers two other possibilities: the possibility of purchasing and storing grid energy when the tariff is cheap then using it at a time when the grid tariff is high, and the possibility of having an 'uninterruptible power supply' for the whole property for times when grid outages occur.
So data collection has its uses. It can inform how best to move with the times as new developments like 'home battery storage' come on the market. The man is coming to see me about battery storage next month. I'll report back.
