Retrofitting heating system with solar?

galah

Hi everyone,

quick question about heating systems:

we're in the process of buying a house, and there's no "real" heating installed. Zero. (well, two storage heaters, a fireplace, and a stanley range). But no radiators or pipes.

So we have to install some sort of heating from scratch (just starting out on this quest, so excuse me if my questions sound a bit stupid).

I am strongly in favour of solar panels/renewable energies and do not want oil-fired heating - but now I've heard that most solar systems only heat your water, but not your radiators. Which makes me wonder- the radiators would be run on hot water, correct? So what would stop us from using solar energy to heat the water for the radiators (considering that the alternative is pretty much no heating)?

Are there any technical issues? Cost issues? I don't quite understand the problem, and research has not clarified this sufficiently for me...;-(

Any pointers welcome!

Cheers,

galah

ThePiedPiper

There are a couple of problems. First would be that for the time of year that you'd want lots of heating, i.e. winter, this is when you'd have the least amount of sunshine to heat the water.

The volume of hot water needed would be substantial to heat the house and would require a crazy amount of solar panels to do so. A man in my townland tried this a few years ago, his entire roof is covered in solar panels and it still wasn't enough. He had to retro fit a boiler.

Also, the temperature that solar panels heat water to is not high enough to adequately heat radiators. I don't know exact figures but I think solar panels might heat water to 45 Celcius whereas rads operate best at 65. I'm open to correction here.

galah

cheers for that.

still don't get it though - are the boiler for the shower etc and the heating not the same? (where I come from, we have 'remote' heating - as in, the hot water is pumped from the actual powerplant through pipes across town to the individual houses, so I'm slightly baffled by the Irish way of doing things...)

anthony4335

The oil will heat up both. A coil pipe goes through the tank in which hot water from the heating system runs through ,heating the water in the tank. You will still need to install a house heating system, as the solar panals will not be enough to heat the house, on its own anyways.

RVR

galah wrote: »

are the boiler for the shower etc and the heating not the same?

As anthony4335 says, the domestic water is usually heated by running the central heating water through a coil in a tank. Example schematic:



Solar is normally only used to heat the hot water (e.g. it would be put through the second coil of the tank above). This is because when there's energy available for solar, it's when there is little or no heating demand.

There are combination tanks / systems out there that can use either the boiler or solar to heat the rads, but as runforestrun says, you'd need a gigantic amount of solar to get enough energy to do it on its own!!!

galah

Thanks all, I am starting to understand the issue (and am not happy ;-()

will have to look into other forms of heat generation then, so.

Appreciate all your input!

quentingargan

Agree with most of the posts here. Solar space heating evolved in countries like Austria where they get more winter sunshine. Below is a chart showing average energy from sunlight per sq m per day each month. You will see that in Dec and Jan, Austria has more than double ours.



I would only recommend adding solar panels for space heating if there is already a large buffer tank present for some other system such as a log gassifying stove. Then it will provide some small benefits.

ThePiedPiper

galah wrote: »

Thanks all, I am starting to understand the issue (and am not happy ;-()

will have to look into other forms of heat generation then, so.

Appreciate all your input!

Galah,
You could consider retrofitting insulation in the attic, pumping the walls, making the house as airtight as possible in order to minimise heat loss.

You seem to be intent on minimising reliance on fossil fuels which is a great goal. A multi-fuel boiler will give you the option of getting your heating and hot water needs from using whatever fuel you wish to put in it: timber, wood pellets, etc.

soldsold

Hi Quentin,

What about the logic of using solar panels in winter to heat air up to a reasonable temperature and use this warm air to preheat air coming into a HRV system?

I think you are 100% correct in saying that using solar in winter to heat space-heating water is not a good idea, but judging by the amount of heat trapped in a small glass porch during the many clear winters days, it seems logical that solar could provide useful space heating through warm air assuming the house was super-insulated and airtight?

Thanks,

S.

gizmo555

soldsold wrote: »

What about the logic of using solar panels in winter to heat air up to a reasonable temperature and use this warm air to preheat air coming into a HRV system?

I retrofitted a HRV system to my house this year and this was one of the options I considered.

One of the HRV suppliers I spoke was very gung-ho for this. Another told me that they had tried it in two installations and found the contribution to space heating at the times of year it was actually needed was negligible. They therefore decided they wouldn't offer this option any more.

It stands to reason - after all, it is very well established that solar hot water systems produce very little energy in the Irish winter months, the occasional bright sunny day excepted.

Charlie 08

could the poster's question work with UFH-works at a lower temperature than rads. Could panels ( the typical set up) be used to heat the water a little and then use oil/gas to bring it up to required temperature?

gizmo555

Charlie 08 wrote: »

could the poster's question work with UFH-works at a lower temperature than rads. Could panels ( the typical set up) be used to heat the water a little and then use oil/gas to bring it up to required temperature?

I'd defer to the experience and knowledge of people like Quentin, but if as is generally agreed, solar hot water systems provide negligble contribution to hot water needs during the winter months, their potential contribution to space heating would of necessity also be negligible.

quentingargan

gizmo555 wrote: »

if as is generally agreed, solar hot water systems provide negligble contribution to hot water needs during the winter months, their potential contribution to space heating would of necessity also be negligible.

True, but as Charlie suggests there is an argument that panels lose efficiency as the temperature of the fluid rises. Therefore if you use solar for UFH, then at 40 degrees the panels are more efficient, and in HRV, the working temperature is even lower. But if you add it all up, even at 80% efficiency (which you won't get close to) there is only a small contribution to the heating needs - about €70 per year if you are replacing oil at 7c per KwHr.

gizmo555

quentingargan wrote: »

if you add it all up, even at 80% efficiency (which you won't get close to) there is only a small contribution to the heating needs - about €70 per year if you are replacing oil at 7c per KwHr.

Scarcely worth the added cost and complication of linking the solar and space heating systems so, unless it was as you suggested earlier, a wood burning system with a big buffer tank. Certainly, the people who installed my HRV were adamant that combining HRV and solar was a complete non-starter and wouldn't sell it, despite the fact that some of their competitors do.