Solar / Battery Storage considerations

Should be straightforward then. Our roof is corrugated iron - they basically used the exisiting screw holes to fix the supporting frame and then fix the panels to the frame. This should be similar. Provided the pitch of the roof and the orientation is okay and you can connect into you house supply, it could be a good option.

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I’m surprised no one has mentioned flywheel batteries yet. They’ve finally hit the domestic market after being the holy grail for years. A French company makes 50Kw home flywheels. If you’ve got the space for one (3 tonnes but very compact and must be installed underground), no chemical battery, long 30 year life, low maintenance.

I can’t wait for them to get safety approval where I live. Exciting times.

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What a brilliant idea. I had a similar idea about a year ago based on a heavy weight that goes up and down a lift type shaft outside your house, but the maths means that you needed a massive weight, and there the idea stopped

But gravity batteries do work on a larger scale. I think there are villages in Germany that use massive ones to provide shared energy storage for the entire village. Though of course they take up a field from what I saw and are pretty darn high. Still, very eco friendly. Everyone’s solar panels work to lift the weights during the daytime and they fall at night.

I just feel like chemical electrolytic batteries are not the way forward out of the storage problem long term.

The future is less tiny magic bars of Star Trek unobtanium the size of a shoe with 10Gw storage and more steampunk I expect. And that’s fine. Embrace the really old and the really new together.

I recall seeing something similar with some heavy freight trains going up and down a hill, so I did steel the idea and try and shrink it for a house.

Like the idea of tiny magic power bars, although in Star Trek world, perhaps they might be little hand held nuclear reactors :thinking:

There’s also the “heat battery”. (Some sort of chemical phase change thing) that are positioned as compact alternatives to hot water tanks.

Put “spare” electricity (solar Pv) in to “charge” them, then to extract the heat you put cold water in and get hot water out.

A bit like those hand warmer gel packs, I think.

I recently had an 8kW solar system fitted, along with 13.5kW batteries. It took a while for the supplier to get all the parts - my house has 3 phase, so I had to wait a while for the correct 3 phase inverter - but it gave us better battery options.

The solar was an easy cost vs benefit decision, but I did weigh up the batteries for a while before committing. Deciding factors for me on the batteries were: i) I am on economy 7, so can programme the batteries to top up overnight at a lower price, then use during the day (my solar will never completely cover my house usage); ii) offset against powercuts - my house is electricity only, no gas or oil.

It’s early days, but I have seen my overall usage from the grid for the month of June plummet compared to last June (and last June I did not have an electric car). I am aware though that June was very sunny with long days in UK. Generation in December will be minimal!

Mostly though, I am impressed (a little obsessed?) with the app that provides real time usage data: how much the house is using and a nice graphic showing where that’s coming from - solar/battery/grid.


Bobby, the decision should not be a narrow financial one. We need collectively to reduce fossil fuel consumption and solar is a ‘no brainer ‘ in that respect.
You rightly point to the huge satisfaction from seeing from the app just how much the sun is delivering your energy needs. It is quite addictive!

A question for people with solar already.

How much output do you see on a cloudy day, say as a percentage of the total array?

I’m interested to learn if a low base load could be covered, even when there is limited sunlight.

Haha, i was thinking something similar regarding winter output.
My PV/ battery install is due for mid sept, so im wonding what ill see for the first 6 months.

We’ve had our system for about 3 weeks, and it’s mid winter. The best so far has been just shy of 30kWh on a day that was clear all day. Today it has rained all day and we got about 3kWH. A cloudy day is about 15kWH.

We have an 8.8kW array and the maximum output we have had so far is 5.5kW.

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Hopefully these charts give an idea for my UK 5KWh panel from Last Dec and Jan. When you get those clear sky cold days, I can generate 3KW quite easily. Cloudy days often generate enough to cover my homes lowest default usage of 250-300Watts

Thanks, that’s very useful information.

Our baseload is fairly similar although we now have an air to air heat pump that runs in winter for our conservatory that ticks over around 250 watts once the room has warmed up which adds to the winter load.

So, during daylight hours you will still generate 200 to 300w. That too would cover my base load ( and a bit more) for when noone is in. Although a long way to charging up my 9.5 Kwhr battery! Hence why im planning on filling that up on the economy 7 at night.

Yes, that is mostly the case, except when you get those dark cloudy days, in which case I don’t get an awful lot.

Today is quite a cloudy day as you can see below

Below was Christmas Eve last year, which probably included a clear sky for the bit in the middle.

Of course my panels are now 3.5 years old, and no doubt newer ones would be even better

Thats good info, thanks.

Well we finally got rid of our traditional electric hot water system and replaced it with a heat pump and water storage tank.
As we suspected, the old electric hot water system was using huge amounts of electricity, and the heat pump uses a fraction in comparison
Because I can see live electricity usage on my app- even though the heat pump only went in yesterday morning, we saved yesterday 12kw , and today saving will be 14kw ( heat pump been in for a full day as opposed to part day)
So pleased we had the heat pump fitted


Gosh, that’s a really good result. I remember you saying that your hot water costs looked odd.

I’ve been tracking our app to see how much our hot water is using. I had it set for 4am to 7am on our cheap night rate and 10am - 5pm for the solar. At 4am it uses about 2 kW to top up the hot water, which seems really good. I’ve just changed it to come on at 6am, as we are now getting some days where 6 - 7 am is the best time for our free hour of power, as the heat pumps are on too. We are getting afternoons with enough solar now to make the spa much cheaper - which is the other time we use that free hour if it’s cloudy.

We hit 30 kWh generation the other day - and it’s only early August.

Part of our challenge was that the hot water didn’t have a timer on it, so it would always reheat the water in the storage tank when it was depleted.

Your solar seems to be performing very well indeed, ours is producing pretty much what the installer said it would, so thats reassuring, we are hitting 15KWh at present ( partly shaded roof but sunshine has returned to Sydney to help) 34KWH is our forecast peak production for January.

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