Originaltwist

The cost to heat it up is different. 100% electricity vs. 3 times better with tank and a heat pump.

I used to fill my evac tube panels with a garden sprayer - the backpack one with a pump handle - so @Chriswills I hope your pump is just as good. You'll be connecting it to the fill station and as soon as fluid starts heading up to the panels then air will be coming down and the air bleeder on the pump station will need manual bleeding a few times. I'm fairly confident this will work for you because the tube types just have a manifold across the top and can't hold much air.

According to the EDDI manual '3.68kW / 16A max. heater load'

The MVHR exhaust air could be just one input to the heat pump plenum greenhouse shed thing. The others being: Sun (stored in the black drums), ground air pipes (circa +5c lift I believe). Obvs the more extra energy you can get in the fewer defrost cycles and the better COP.

I like the way your project is shaping up but talk of radiator upgrades made me wonder about a DIY fan-coil unit I came up with a while ago. It's cheap and neat and better for low temperature flow - just needs an open mind to give it consideration. There's a description and pictures on https://originaltwist.com/2018/11/14/diy-fan-coil-heater/ so I won't bang on about it here.

I think a lot of things have changed to make off-peak storage in water viable: High temperature heat pumps enable a wider Dt and so more heat stored in smaller tanks. Off-peak electricity becoming even cheaper thanks to the electric car era. Unstopable wind and nuclear power has to be dumped Better insulated homes need far less energy. PV more common, enabling DHW top up with an energy diverter Combine all the above and a 1,000 litre tank works - a few years ago you'd be looking at a swimming pool.

Interesting thought about spare capacity. Here's your idea modelled but with a smaller Dt as it's hard to get the tank below 25C - but yes, 400 litres hits the spot.

@sharpener - I have just gone through your economics analysis (better late than never) and the payback calculation is the only way to approach this of course. As you intimated before, the MCS wallahs might insist on an oversized HP so the extra cost would mainly lie with the thermal store. Having had one myself and encouraged many others to do so, I know that in general they are intrinsically fine bits of kit so water based thermal storage is a good way to go; certainly good enough for anyone going down the heat pump route to give it serious consideration. Off-peak energy is mainly renewable too, so this system is kind to the grid and the planet and your wallet.

For me it's about the triangle thing in your workspace - fridge, cooker, sink. Heres one I did earlier, and it worked really well

Off-peak energy storage for cheaper heating Off-peak energy plus heat pump equals unbelievably cheap heat. But how to store it? High temperature heat pumps might make all the difference (wider Dt) so here’s a shot of my model which shows that a 1,000 litre buffer tank along with, say 300l, DHW and a bit of slab heating might work. 60kW.hrs a day for £300 a year – worth a look! Conclusions are a bit disturbing and contra intuitive as inefficiencies are overcome by economy. Buffer tanks should be huge Blending down is necessary Zoning is easy and a good thing HP running all day is not a good idea A much bigger heat pump is needed A mini-split addition is even more desirable I’ve sketched out how such a system might look on Off-peak energy storage for cheaper heating https://wordpress.com/post/originaltwist.com/7618 So, team, is this worth a look or a step too far? N.B. I'm aware this contradicts all the wise words seen so far on this topic and I apologise for that but I genuinly can't see what will no doubt emerge as the big flaw.

The thing with diverter valves is that flow stops dead during the changeover - can't imagine heat pumps like that. Coster used to do one with constant flow but any other suggestions?

The panel layout will be interesting and there will almost certainly be shading issues. So, microinverters on all the panels (Enphase obvs). That's going to be a bit more expensive to start with but more reliable and cheaper in the long run. Probably Victron to charge the battery and maybe Fogstar for the battery. Eddi for the immersion and I believe that can cascade onto the Zappi. Some thoughts to juggle with anyway.

All this talk of nuclear fusion makes me laugh. Our area has been connected to a local nuclear fusion plant for ages and myself along with a few neighbours are already connected. The benefits certainly compare well with other forms of energy. Unlike conventional sources there are no wires or pipes because the transmission is wireless. It’s hard to imagine how that works, but the energy is sort of beamed across the airwaves. It is necessary to have line of site from the reactor to the receiver so this may not be available for everyone. There was no cost to actually connect to the source reactor although the receiver was fairly expensive at around £5,000. Possibly the major benefit though is that there is no charge for the energy supplied as it is beamed, free of charge, directly to the receiver. In these times of hugely expensive energy, it seems impossible that this fusion power can be free but it’s true, there is no charge for the power and no sneaky daily charges either. Furthermore, the price is fixed at zero and it is guaranteed that there will be no price increases ever. On the downside the transmission has been fairly erratic and a bit limited over the winter. This deficiency can be largely remedied by having a battery to tide us over the downtimes. So far, reliability of the fusion reactor itself has been good and I’m told it is unlikely to fail for well past our own lifetimes. It is comforting to know that it has never been known to fail; unlike some other supplies. So, you may well ask, if it’s free energy with free and quick connection why isn’t everybody doing it? Well, it beats me but I have noticed that a few savvy people round here have got the message and have fitted receivers to their rooftops. You might not have heard about all this because the big energy suppliers want it to be kept secret. So, keep it to yourself. Mum’s the word.

Yes but you can prove anything with facts. Seriously though, I love those charts, where do they come from?

There's a bar for night rate electricity on the chart so that's your cost with a bit added on for the inefficiencies of the battery.

Mmmm Yes oil is looking quite good at the mo. I've just updated the comparison chart for the next cap etc.

Ask him if there's a £7,500 grant to fit the oil burner. Oil burners definitely best to have serviced - I don't bother with my heat pump just as I don't have my fridge serviced. Running costs may be similar EXCEPT when running off-peak, running off batteries, running with PV and the sun shining.

Sorry - pressing all the wrong buttons. Anyway that was a long double ender with a tiled surround. The taps were set for easy access and fed the spout placed so the water flow would be by ones knees so no scalding feet etc.. Can't say I liked it though - very difficult to get out.

I did a write up on a modern floating design along with some details on the geometry - might be useful. https://wordpress.com/post/originaltwist.com/1927

When you consider that most of the planet is covered by water -which naturally evaporates- then any rise in temperature will have to make more rain. Where will it all fall? Well. England obvs.

I encountered the same issue with a heat bank but the issue was not electrical. The problem was due to a pressure drop when taps etc were turned on and the flow switch didn't get enough of a kick to activate it. The owner was not willing to remove the flow restricting pressure reducer on the mains or to change to a more sensitive flow switch so the situation was left unsolved. The local plumber, of course, knew better so I left them to it. A lot of people don't see they have a pressure problem when the pressure guage looks good and they don't notice the drop when there is flow. I suspect from the dialogue so far that the problem really is electrical but I thought I'd add this just in case.

Aha But if the V2L is fed to a domestic battery via the generator connection on a Quattro-II then there is no additoonal hazard and no phase conflict. I get that it's a bit weedy, but not by much and an amperage limiting relay could bring on the mains if required... trying to get towards a solution here.

Try again Thanks for that. I'll be having a look round the Kia/Hyundai marque with V2L. Some questions for the team arise; Could I have a separate battery driven house circuit that doesn't back feed the grid and doesn't need any permissions. So the mains could charge the battery if needed but nothing in reverse. There's already a back feed preventing trip (Enphase for example) so would that do instead. Should it have a static battery as well as the occasional V2L hook up. I.e solar storage works while you go shopping. I suspect the multiple in/out connections of the Victron Quattro-II might make this work but I need a deeper study. With so much storage to hand I can see a house running entirely on off-peak power. Divide by 3 with heat pumps and it all gets rather interesting.