30kW PV, All electric heating, is this mad?

[LnP]

On 22/06/2023 at 13:45, HughF said:

Multi head mini-split, job done.... Cheap as chips, easily controllable, easy to fit.

@HughF sorry I'm a bit late to this discussion .... This is interesting. A couple of questions:

Are you recommending multi head mini split heat pumps just to provide air-conditioning or also for space heating?

For cooling, how would this compare with running an ASHP in cooling mode through fan coil units as well as through the UFH? Say UFH on the ground floor and fan coils in a few specific rooms. I believe Daikin ASHPs can deliver water at 7 deg.

[JohnMo]

If you are doing UFH (cooling) your flow temp doesn't want to much below 11-12 degs, but the fan coils would ideally be cooler.

 

If you go that direction with ashp you would need a second flow temp, some do this out the box most don't.

 

CoP A2A should be slightly better depending on which unit you choose, as there are big differences in performance.

 

A2A can do both heat and cool equally as well. Both can give great CoP.

[PeterW]

@DevonBarn are you considering any sort of secondary heat such as stoves ..? If so, and also for the heating, I would start by putting UFH in as it can be used as a big heat store in the winter. I would also consider a very big heat “accumulator” setup with 1500-2000 litres of storage as you can run a boiler stove hard into it and then make the most of the hot water when you need it as either a buffer or a preheater for your hot water supply (which needs to be min 500 litre UVC) and then maximise your solar to divert into the tank too. It’s one of the only instances I would also look at Solar Thermal, as you can dump it into the buffer too. Like a lot of others say - start with a 3P connection though as it opens up opportunities ..!

[Mike]

2 hours ago, PeterW said:

I would also consider a very big heat “accumulator” setup with 1500-2000 litres of storage as you can run a boiler stove hard into it and then make the most of the hot water when you need it

With a budget of around 32K to play with, you could look at adding another 0 to that volume a going for an inter-seasonal store - that is, one you heat during the summer and draw on during the winter. They've been doing it on a small scale in Switzerland and Germany for a couple of decades - see the https://www.sonnenhaus-institut.de/ (in German).

 

For example a 24,000 litre tank being installed here https://aktivsonnenhaus.de/veranstaltung/13-09-2016-spektakulaere-speichersetzung-in-90559-burgthann/

 

And someone here considering the idea of using a 20,000 litre milk tank as a thermal store https://www.earth.org.uk/milk-tanker-thermal-store.html

 

 

 

[SteamyTea]

59 minutes ago, Mike said:

They've been doing it on a small scale in Switzerland and Germany for a couple of decades

What latitude is that place, and how different is the weather?

[Mike]

2 hours ago, SteamyTea said:

What latitude is that place

There are multiple installation, but Switzerland isn't that big - double the size of Wales / half the size of Scotland

 

 

2 hours ago, SteamyTea said:

how different is the weather?

 

Warmer in summer, colder in winter:

 

Climate comparison: Switzerland / United Kingdom (worlddata.info)

 

 

More regional variation in Germany though.

[SteamyTea]

34 minutes ago, Mike said:

Warmer in summer, colder in winter:

And a lot sunnier I suspect.

There has been a lot of research done in Denver. That is further south than Madrid.

At the moment it is 15⁰C where I am, and looks like this.

That is St. Michael's Mount in the fog.

 

[HughF]

20 hours ago, LnP said:

@HughF sorry I'm a bit late to this discussion .... This is interesting. A couple of questions:

Are you recommending multi head mini split heat pumps just to provide air-conditioning or also for space heating?

For cooling, how would this compare with running an ASHP in cooling mode through fan coil units as well as through the UFH? Say UFH on the ground floor and fan coils in a few specific rooms. I believe Daikin ASHPs can deliver water at 7 deg.

I was suggesting it for both heating and cooling. They really are a wonderful technology.

 

They should beat a2w on a COP perspective, and it is easier to manage the condensate on them as the line sets are pre-insulated.