Using solar power to heat an Annexe

[John1958]

Hello, we live in a barn conversion that has (wet)underfloor heating. In almost all areas it works well but it has always been a lot cooler in our guest annexe than the rest of the barn. We currently have an engineer looking into this issue but I am in “looking ahead” mode.
If we are unable to increase the temperature in the UFH I want to look into the feasibility of using solar panels to heat this room. Just that one room. We live in Norfolk and the climate is much better than anywhere we have lived before….plenty of free sun.
If anyone can point me in the right direction, so I can do further research, I would be most thankful.

John

 

[ericmark]

North Wales and solar water heating failed, Turkey it worked well. So likely a better idea to use electric panels, the main thing is wires don't loose heat, but pipes do, also water collects radiant heat, but electric works with light as well.

To gain maximum output from electric solar panels the voltage varies through the day, however I am not sure if all the complex control gear is required, an immersion heater does not care if AC or DC, so maybe you can directly connect a panel to an immersion heater?

The Centre for Alternative Technology were testing solar panels back in the 80's, I remember visiting back then and seeing the panels tested and how long they ran before failing, the simple mat black radiator behind a double glazed window, did nearly as well as the professional built units.

 

[JP_]

Surely solar panels will only work when the sun is shining, and if the sun is shining, then well placed quality windows will bring in more heat.
Might it be more economical to install a electric heaters for the annex, that can be used just when you have guests? Or is it used more than occasionally?

 

[motorbiking]

Its not clear from the OP, if you are considering pre-heating the water via solar, or PV connected to some sort of air con.

I'd start by trying to diagnose the UFH issue, maybe close the zones in other rooms or boost the pump speed. To heat via solar PV, you will need at least a 3kw system, Tesla power wall or similar and then hot/cold aircon. Budget maybe 8-12k. or you could put an electric fan heater in the amex? Budget £40 (cost over 20 years) about £1,500

 

[AngleEyes]

There's quite a few options: HRVS (Heat Recovery Ventilation System) heat recovery from ventilation from bathroom & kitchen, (ASHP) Air heating pump for that area, (GSHP) ground source heat pump, auxiliary heat source for that area, plus those systems mentioned by others.
You need an on-site inspection really to propose the best solution.

 

[lostinthelight]

To give you an idea of solar panel output, I have 3.3kwh system which produce a maximum of 2kw in total on a sunny day at this time of year and some days it's less than 1/2 a kw so not a lot of use for heating as I see it.

 

[John1958]

This solution would only be to heat the room and raise the ambient temperature. No need to heat hot water. There is already a separate electric heating system to heat the hot water in the adjoining shower room. There is also separate electric underfloor heating in the shower room as well as a separate electric towel rail. Both are REALLY expensive to use. That is why I am investigating a solar solution to heat the annexe/bedroom.

 

[John1958]

Surely solar panels will only work when the sun is shining, and if the sun is shining, then well placed quality windows will bring in more heat.
Might it be more economical to install a electric heaters for the annex, that can be used just when you have guests? Or is it used more than occasionally?

I am interested in finding out to what extent one can store heat from the sunny days to use in the days when it is crap?!

 

[JP_]

I always assumed that the reason people generally heated water with solar was because it is much easier, and cheaper, to store hot water in an insulated tank, than it is to store electricity in a battery.

Air source heat pumps are all the rage at the moment - could one be installed just for the annex?
Or maybe could it have its own mini boiler with rads, or is that just too expensive?

 

[John1958]

To give you an idea of solar panel output, I have 3.3kwh system which produce a maximum of 2kw in total on a sunny day at this time of year and some days it's less than 1/2 a kw so not a lot of use for heating as I see it.

What do you use your system for?

 

[motorbiking]

most people with PV systems use the electricity to run their home, with excess going to the grid or in to an EV. Over time the subsidies have reduced for Feed in Tariff, so typically you need to consider a battery to store your excess. You can also get intelligent water heaters that will heat a water tank via emersion heater. If you have a big PV system, you can run air sourced heat pump (which is basically what an aircon unit is).

The other option is a pre-heater for hot water, which basically takes the source temp up from whatever it comes out of the mains up, to say 5-10 degrees winter and 60+ summer to reduce the energy heating water.

 

[jeds]

There is no realistic way to directly heat a space with PV panels. In theory you could run an electric heater but that would only work minimally and only when the sun is bright - i.e. when you least need heating. Solar generated electricity would supplement your general electricity supply, which in turn might power electric heaters, but that isn't direct heating.

You don't give details of the spaces or how they are arranged but, for a self contained open plan area, and if you have an outside wall available that is out of the way, you might look at a wall mounted split system. (look up small wall mounted split heat pump) These are not too expensive and provide on-demand warm air heating to a space - and can be reversed to provide cooling as well. They are also extremely efficient.

 

[John1958]

There is no realistic way to directly heat a space with PV panels. In theory you could run an electric heater but that would only work minimally and only when the sun is bright - i.e. when you least need heating. Solar generated electricity would supplement your general electricity supply, which in turn might power electric heaters, but that isn't direct heating.

You don't give details of the spaces or how they are arranged but, for a self contained open plan area, and if you have an outside wall available that is out of the way, you might look at a wall mounted split system. (look up small wall mounted split heat pump) These are not too expensive and provide on-demand warm air heating to a space - and can be reversed to provide cooling as well. They are also extremely efficient.

Many thanks.

 

[lostinthelight]

What do you use your system for?

It goes some way to reduce the amount I have to pay for power from the grid as well provide nearly all our hot water by a previously mentioned, intelligent switch , from March until October . Without an expensive battery this is about the only way to store unused capacity.
My system generates 3000kw a year for which I receive around £200 in Fit payments which has now been replaced by another scheme.