Alternatives To An ASHP

[pdf27]

1 hour ago, Iceverge said:

Solar thermal is parallel universe stuff at this stage. I really like the idea of it but I'm not sure I'd bother installing it if I got the equipment for free.  If you want solar hot water install PV and an immersion. Solar thermal has high heat losses from the panel to the tank, requires servicing, is less reliable and arguably more expensive at this stage. On top of that for most of the year it won't get the water hot enough or will get it too hot. 

Most of the maintenance issues seem to be related to the MCS requirement to use Glycol antifreeze. Glycol really doesn't like being hot, and so degrades to sludge over a number of years. If you use plain water instead, and rely on the controller to do freeze protection using low-grade heat from the hot water cylinder then they seem to be pretty robust.

 

Having said that it doesn't make sense if you can use a heat pump and PV - you'll get more heat per unit cost or roof area from PV than from solar thermal. The only way I can make it work is if you're chasing a particular standard which doesn't count solar thermal heat against the energy in the standard  (I think Passivhaus still does this), and even then it's only worthwhile if the alternative ways of hitting the same standard are more expensive.

[joe90]

6 hours ago, Iceverge said:

There's a simple answer to your issues here. Install UFH and a cylinder capable of using an ASHP.  Plan to run it on cheap electricity via Willis heaters and immersions initially with an option for ASHP later. 

 

Dedicate all your energy thinking about heating into making the house as low energy as possible. 

This is what @TerryE did and it works well for him!

[Matt60]

On 06/03/2021 at 10:16, Iceverge said:

There's a simple answer to your issues here. Install UFH and a cylinder capable of using an ASHP.  Plan to run it on cheap electricity via Willis heaters and immersions initially with an option for ASHP later. 

 

Dedicate all your energy thinking about heating into making the house as low energy as possible. 

 

Thanks, I think this is probably the way to go and with a very low initial outlay. If at a later date an ASHP was fitted, would you aim to use it just for the cylinder or to replace the Willis heaters too?  I guess some PV and a battery would be good with this too if the cost is justifiable? 

[joe90]

13 minutes ago, Matt60 said:

If at a later date an ASHP was fitted, would you aim to use it just for the cylinder or to replace the Willis heaters too? 

As you could get up to COP4 fir an ASHP you might as well use it fir both (like I do).

[Matt60]

10 minutes ago, joe90 said:

As you could get up to COP4 fir an ASHP you might as well use it fir both (like I do).

 

Thanks, would I be able to to do this and have the upstairs heating circuit running at a higher temperature than the UFH on the ground floor?  I don't want UFH upstairs (two professional house builders I know have said it's more trouble than it's worth) and I'd rather avoid having over-sized radiators too. It's possible that even if they ran at the temp of the UFH it would be enough with the thermal efficiencies of the build, but I'd like to know if I can run the tank, UFH and rads all from a ASHP with all three requiring different temps. 

[joe90]

As you know running an ASHP at higher temps reduces its COP. I have no heating upstairs apart from bathroom towel rads. If you wanted higher temps fir the rads then all heating would be at that temp and just blended down fir the UFH. !,!

[Iceverge]

Do some quick sums on batteries and solar PV if you can. 

 

It soon becomes apparent that it's cheaper not to use electricity through efficiency than to generate more and store it. 

 

A tank of hot water makes a cheap battery also.