Terence Eden
@Edent@mastodon.social  ·  activity timestamp last week

What would it take for our home to be Solar Self-Sufficient?

Work in progress, but I think I have the answer.

🏠 I live in an ordinary house in suburban London.
☀️ Our solar panels generate 3,800kWh per year.
🔌 We use the same amount of electricity per year.

After crunching the numbers:

🔋 Capturing all our solar excess needs a 1 MegaWatt-hour battery.

#Solar#SolarPunk
Julian Schwarzenbach
@jschwa1@mastodonapp.uk replied  ·  activity timestamp last week
@Edent WE have a large heat pump and a large solar array plus battery.

Our graph of solar export is probably similar to yours.

But our consumption graph is the other way - high in winter (when there is little sun) and low in summer when there is plenty.

The battery helps in winter and in effect offsets some of our daytime consumption to night time cheap rate.

Going entirely off-grid, for us, would require an extremely large battery!
Anonomouse13
@Anonomouse1981@mstdn.social replied  ·  activity timestamp last week
@Edent

If your electric network was like USA, California, you could sell back the unused electric to the grid at wholesale rate in the summer, then buy your electric it from them at market rate in the winter. "Grid tie interconnect" or some other tech sounding phrase.
TOO , Caliornia method doesn't pay you. You'd get a "credit" you can spend down during future use, not a check in the mail.
Andy Fletcher
@X31Andy@mastodon.green replied  ·  activity timestamp last week
@Edent 1MWh isn't a stupid capacity for a battery. China grid scale storage bids are currently coming in at US $55K/MWh for GWh scale systems. So give it a few years for smaller scale systems to be come economic. I can and have built offgrid LFP battery storage systems for £80/kwh

Problem in south UK is summer/winter solar yields are about 6:1 so you have to oversize your arrays for winter use but you can put the panels vertically on a south facing wall which works well in winter.
mirth@mastodon.sdf.org
@mirth@mastodon.sdf.org replied  ·  activity timestamp last week
@Edent To provide the assurance of available electricity without needing to provision the battery bank with capacity to handle the 99.99% case alone. Rough numbers, 1 MWh battery is perhaps 100,000kg of CO2 lifecycle emissions, while a fossil fuel generator in use emits something like 1kg per kWh. Each 10kWh of battery is similar CO2 to getting 1MWh from a generator. This suggests that the first X kWh pay off due to high utilization, but at some point a generator is lower marginal emissions.
Waslich
@Waslich@mastodon.social replied  ·  activity timestamp last week
@Edent because my home needs less than 10 kWh on the coldest days (northern Italy) but with heat, dhw and cooking included (no gas contract anymore), thus it seems to me that using that amount of energy every day of the year without heating (dhw and cooking on electricity or gas?) is a lot. And it's not that we're doing anything special with our appliances. It's not average to have the amount of solar panels you have, it's not necessary to retain average consumption either
Phil Dennis-Jordan 😷
@pmdj@mstdn.social replied  ·  activity timestamp last week
@Edent I assume you could shrink the battery size requirement quite a bit by adding more panels, especially in winter-optimised locations? (Assuming the physical and legal realities of the building allow it.) So, strategically using E/S/W-facing exterior walls or balcony railings that receive a decent amount of winter sunlight to mount panels. Also, things like solar fence panels.