As the heatwave dissipates (for now) the need for enhanced air conditioning & the worries about its energy are becoming a concern.... but, hold on:

As we move to renewables & energy storage to deal with fluctuations in need & supply, we're looking to build capacity to get us through winter usage; but currently summer usage is much lighter, meaning we'll have lots of spare capacity in the summer to run AC units.

Maybe too neat, but not implausible?

#energy #GreenTransition #politics
h/t FT

@ChrisMayLA6 something something jevens paradox?

@ChrisMayLA6

Actually AC units can fully run on solar energy. A single balcony mounted solar panel of nominal 500W power can pump out circa 1500BTU/hr.

(For not STEM readers – cooling a room from solar is a net zero action – energy used to pump the heat out of your room is energy that would otherwise heated the surface where the shadow of solar panel now is).

@ohir @ChrisMayLA6 One of the challenges might be the infrastucture.

In the UK there is a 3.5kW limit on the feed, which usually means the inverter is capped, which in turn means you can't produce more, even if you use it yourself, or have local storage options.

I have 5.8kW in panels, but the inverter caps it, so in the summer I lose about 60% of its capacity in heat produced by the inverter (and the attic is hot enough as it is).

@wanwizard @ohir @ChrisMayLA6 The UK allows 3.6kW grid tie with no complicated paperwork, most people currently get 5kW+ if they apply. If your system can limit properly (so called G100) you can have a big system with a small export, plus all that you store in batteries so 10kW is perfectly doable.

32kWh batteries now start around £3200 quid so its not expensive to store lots of it too - about 2 grand (including vat for retail) for 16kWh - has gone up a bit since Trump made an ass of himself

@wanwizard
> In the UK there is a 3.5kW limit on the feed,

This is a G99 limit that does apply to the grid–connected installations (a 3.68kW/phase). Small AC units can run off balcony solar energy "off-line".

@ChrisMayLA6

@ohir @wanwizard @ChrisMayLA6 Yep - I have about 4kW of solar panels in the garden that are plugged into batteries that run the aircon and in winter a fair chunk of the heating on many days (often the coldest UK days are clear skies).

As it's plugged together and not grid tied it doesn't even need an electrician or other such nonsense.

@ChrisMayLA6 There is one funny involved in this - your general assumption is sort of right. However most of the grid equipment has performance ratings that are temperature sensitive so the grid actually gets downrated all over the place on hot days (or if your equipment wasn't built for the heat goes bang.. as has happened across Europe).

@ChrisMayLA6 If you can ensure that the AC units that are getting installed are fully functional, bidirectional heat pumps, you're likely helping with decarbonization significantly. Even with fossil fuel-produced electricity, heat pumps provide building heat at much lower carbon intensity than gas heat, and of course they're much easier to power with renewables than gas furnaces.

A huge part of Europe's remaining carbon problem is its reliance on gas heat. Get ye some heat pumps! (And take the AC along with it!)

@MichaelTBacon @ChrisMayLA6 Most fixed systems installed in the UK are bidirectional. A lot of Brits though know nothing about aircon and buy dreadful single hose chinesium budget products then wonder why they don't cool well, cost a fortune to run and die after 2 years (often not helped by the fact they don't clean the filters).

Bigger problem is the UK has a bizarre obsession with using mostly heat only and expensive air/water systems because they sort of work like old gas boilers but badly

@etchedpixels @wanwizard @ohir @ChrisMayLA6 I assume the batteries as Li-ion these days? (Or Li-FePO?) How do you feel about longevity and fire risk?

@pavel
> I assume the batteries Li-ion
Li-Ion I deem too dangerous to keep around house. LiFePO₄ are the primary batteries for storage now. With the LTO (titanium) buffers can be good for some 15-20 yrs. 8-10 without such a buffer. Note that this still is theory assuming the maker claims. In practice I recently saw an influx of used LTO batteries having less than 70% of their nominal capacity. AFAIK all come from the refurbishing Chinese public transport fleet. The Natrium batteries are fresh so I can not share too much.

Personally I for years was trying to get through with a message that lead acid batteries are the way forward. But 'industry' will fight tooth and nail against them.

@ChrisMayLA6 @wanwizard @etchedpixels

@etchedpixels @ohir @ChrisMayLA6 That would suggest I was incorrectly advised and sold the wrong system?

@wanwizard @ohir @ChrisMayLA6 wouldn't surprise me as the old G99 form was difficult to do so installers avoided the extra hassle. They may also have known your location wasn't likely to get a good export limit based on other applications.
The G99 application was simplified over time but it used to be a real problem.

@pavel @ChrisMayLA6 @wanwizard @ohir LFP, decent ones have 6000 to 8000 guaranteed full cycles to 80% of original capacity.

The fire risk is tiny from actual data (lower than say a tumble dryer). The actual real world risk is what happens when an existing fire from another source burns one. The current rules here put most big batteries outside or in garages (UK garages attached to homes have fire protection because petrol cars are a vastly bigger hazard).

@ohir @pavel @ChrisMayLA6 @wanwizard having dealt with lead acid I would rather not have heavy poor utilisation hydrogen emitting batteries anywhere. Lead acid is dying for good reason.

@etchedpixels
> LFP, decent ones...
Yes. LFP are safe. The Li-Ion are not.

@pavel @wanwizard

@etchedpixels
> having dealt with lead acid ... would rather not have

I am talking grid-scaled Pb-PbSO₄ batteries, without Ca⁺ and other planned obsolescence additives.

Those batteries are more expensive than LiFePO₄ technology but are perpetual: the full regeneration cycle (to be performed once per 8-15yrs) wastes less than 0,05% of weight, mostly due to impurity of the electrolyte solution. Unlike LiFePO₄, the production process of the lead-acid batteries is simple and clean. Lead once put in the battery case remains there for millenia to come.

Cost of storage is estimated to be ~€2.2m per 1MWh. For local storage facility we e.g. can use existing 30x50m parking lot stuffed 1.5m under surface with 1m high plates. This gives 12MWh max battery. 10MWh safe cycle capacity; for €25m.

Talking whole countries: 3TWh storage can be built under the highway's verges. With mean width of 4m and the same industrial plates as above we need some 100km to get at 3TWh capacity. Built using 20 years worth of copper ore waste tailing, and sulfur from the natural gas purification.

Electrolyte H₂SO₄ comes from flue-gas desulfurization (EU still has coal power plants). Such 3TWh battery cost is estimated at €20bn, €2bn/year with 10y target completion.

*3TWh estimations were made for the Germany's 24h needs.

@pavel @wanwizard

@wanwizard
> Wrong system
I dont't think so. Likely, installers knew the grid operator will be cutting you off frequently with bigger installation. You saved money, they were spared the G99 hassle and approval delays.

@etchedpixels @ChrisMayLA6

@ohir @wanwizard @ChrisMayLA6 that's not even how the UK works. If you get a G99 it's because the local grid can take it (and with quite a margin). There is no cutting people off - you are spouting chatgpt grade nonsense

@etchedpixels @ohir @ChrisMayLA6

I'm not even looking at exporting more than 3.6kW to the grid.

The point I was making was that if I can generate the full 5.8kW, I can export 3.6kW of that to the grid, and use the remaining 2.2kW, either directly or for battery charging.

I can't do that now because the inverter is capped, not the export.

@wanwizard @ohir @ChrisMayLA6 You will need a G100 compliant system to do that. That would have been a somewhat more expensive install and if the system was installed some years ago then may well not have been a sensible option at the time. It would need a lot more context.
There was and to some small extent is a problem with installers avoiding G99 so they can bang out installs with less paperwork. Installers work in their own interest a lot - pushing high cost fancy brand name kit etc

@ohir @pavel @wanwizard Only non LFP you see in big stuff here is NMC. Some DIY folk reuse NMC car batteries in homes which I find terrifying. Location is also regulated by PAS63100 so no batteries in stupid places like by the front door any more

@etchedpixels
> If you get a G99 it's because the local grid can take it

I read about UK's G99 and understood it is needed to get _bigger_ than allowed 3.65kW per phase installation.

I’m sorry for misunderstanding, I should have made it clear throughout that connection requirements vary from country to country.

> There is no cutting people off

In my country (Poland) the grid balances by cutting simple installations off. If you have 'hybrid' installation that can independently supply home you can use your production. But if you have cheap 'online-only' inverters those are instructed by the grid operator to stop producing.

@wanwizard
@ChrisMayLA6

@ohir @wanwizard @ChrisMayLA6 The UK grid will generally take 3.68kW without issue. Above that is pre-approval based on whether the grid will take it and other stuff reliably. G100 then allows inverter with export limiting in most cases. We have a few spots where G100 will be refused with ancient rural wires on poles
The overvoltage shutdown is seen as an emergency thing only, and if a piece of grid hits that the grid operators are required to fix it.

@etchedpixels @ohir @ChrisMayLA6 I'm in Scotland, and afaik you need G98 for a maximum of 3.6kW export, and G99 for exports above 16A per phase.

As I'm not interested in higher exports, G99 is not relevant for me, I'm perfectly fine with the 3,6kW export limit.

What I'm not fine with is that my inverter is converting 2.2kW of excess production into heat, when I could have used that myself, either directly or for battery charging.

@wanwizard @ohir @ChrisMayLA6 it's not turning it into heat to be clear it's just not using it so your panels are a bit warmer as they are turning less of the sunlight into electricity.

Battery is definitely another option - excess into the battery for night use or steady lower export.

Gentlemen, let's set our detailed chat to quiet, please. And take our host, ChrisMayLA6 off it.

@wanwizard
> with is that my inverter is converting 2.2kW of excess production into heat

If that is the case, a fake MPPT cheapo inverter was used by whomever you bought installation from. A fraud IMO.

@etchedpixels
> The UK grid will generally take 3.68kW without issue.

Here even 1kW started to be a problem, as in many regions 90% small village houses have 4-10kW peak power installed on their roofs.

@pavel

@ohir @etchedpixels @pavel Just learned about MPPT, so forget that comment.

Most UK installs are capped to 16A single phase, because the costs and paperwork to go over that are prohibitive for most households.

I have excess capacity on the roof because only in the few summer months I can get close to 100% production (due to me being far north), this allows me to produce 3.6kW for longer. But it wastes capacity in those months, capacity that with the current systems can't be used.

@wanwizard @ohir @pavel Most UK installs are over 5kW. The G99 form was changed several years back to make it easy to do larger home installs. Historically it was a mess because G98 was easy but G99 was the same form for a 5kW inverter or a solar farm. That was thankfully resolved so these days most installs are bigger

If you have a 3.68kW or less inverter you would probably have to replace it to fix the limit unless it can also take batteries directly itself (DC coupled)

@etchedpixels @ohir @pavel Mine dates from 2022, and I was told I had to shell out for a full grid capacity survey if I wanted to go above 3.6kW. So I've been had?

@wanwizard @ohir @pavel A G99 application is usually free. If it's refused then the next step becomes things like a study to determine the costs of the needed grid upgrade. That bit is never done by homeowners because it's on a bizarre basis that whoever causes the upgrade pays for it all not just their share of the benefit. So the grid upgrade paths are done by new housing estates and the like not random homeowners.

@wanwizard @ohir @pavel What I don't know is if your installer actually did a G99 application, or pre-approval check or just talked to the DNO and got told "wil be refused". In that case the next step if anyone wanted to continue would indeed by to work out what it would cost to improve all the local grid

@etchedpixels @ohir @pavel Yes, they did. You need the full paperwork before you can apply for the Scottish grant. I have a copy of the DNO approval.