In my recent post featuring a residence in Tucson, Arizona (latitude 32 north) I found that no reasonable number of Tesla Powerwalls would allow the homeowner to go off-grid using a combination of solar and battery storage. In this post I review a residence in UK (latitude 52 north) and find, unsurprisingly, that its prospects for going off-grid with solar and Powerwalls are likewise non-existent. Further reviews show that the overgeneration approach does not work well in the UK either. The only presently-available option for a UK homeowner with a solar array who wants to go off grid is to combine solar with a backup generator.
The solar array I chose as my UK example is on the roof of 10 Mossbank Way, Shrewsbury (data from Sunny Portal). With a capacity of 4kWp (16 Sanyo HIT-H250E01 panels), total 2016 generation of 3,809 kWh and a capacity factor of 10.8% it’s about as average as you can get for a rooftop UK system:
10 Mossbank Way, Shrewsbury
Daily average solar generation from Mossbank during 2016, the last full year for which data are available, is shown in Figure 1. Average power output was highest in May (0.71kW) and lowest in January and December (0.13kW) – a seasonal range of more than a factor of five:
Figure 1: Mossbank average daily solar generation, 2016 (a plot of hourly solar generation for the entire year is hard to interpret). The red lozenges are monthly means
Hourly solar generation data for May and January are shown in Figure 2 for illustration purposes. The large differences in total generation and the abundance of January days with minimal solar generation are apparent:
Figure 2: Mossbank hourly solar generation, January and May 2016
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