Posted By: Ed DaviesBut then you need an inverter as well. And you're probably limited to 16 amps at mains voltage. And definitely need an electrician.

Sorry Ed, I didn't realize this was an off-grid thread!? The OP has an electric cooker. So of course he'd have an inverter with the PV. And what's the problem with electricians? The OP has already as much as stated he'll need a plumber so why wouldn't he need an electrician! And what's with a 16 A limit, where does that come from?

an02ew
Do you have a heat meter on your system, then we can compare it to local weather conditions.
How does the system cope in the summer, any over heating/reliability issues yet?
What service regime do you do?

So about 9 kWh/day delivered, what area does the complete system take?

At current E7 prices it would cost about 63p/day, so £735 for the last 1170 days.

A quick look at PVGIS and assuming that you can fit 2 kWp system in the same area would yield 1890 kWh a year (in the middle of Devon).
So over that same 1170 day period you could have generated 6060 kWh, so 40% less.

So on basic numbers it looks like your ST system is performing better.

What did it produce yesterday?

Posted By: djhSorry Ed, I didn't realize this was an off-grid thread!?

Yeah, but I was answering an02ew's “Solar thermal, its cheaper, can be self installed by competent person” so a direct comparison wouldn't necessarily be (all) grid connected. With the 16 A limit you might want at least some PV which isn't if you're serious about replacing solar thermal.

Posted By: an02ewMy solar controller has some data that says

1170 operating days
10647 kWh of heat

Right, but how much in December and January? Or even November and February?

[Cross-posted with Steamy and An02ew's last two.]

Posted By: SteamyTeaA quick look at PVGIS and assuming that you can fit 2 kWp system in the same area would yield 1890 kWh a year (in the middle of Devon).
So over that same 1170 day period you could have generated 6060 kWh, so 40% less.

1) You often need to compare on cost, not area. Of course, sometimes it is area that matters.

2) There's no doubt that solar thermal can produce oodles of heat in the right circumstances and will almost certainly beat PV on cost as well as area for total annual production.

However, weak sunshine and high output temperatures for DHW are not the right circumstances. In that case ST will basically produce nothing whereas PV will at least give you a trickle of heat. If you have enough of it that could be a very useful trickle.

We're moving (very slowly) towards an energy system where prices, particularly of electricity, are very much more variable (more renewable energy plus smart metering (not a coincidence)) so electricity is very likely to cost a lot more just at the time when solar thermal isn't doing anything useful for your DHW.

I have 8 panels of 20 47 mm tubes to go on my house. I'm planning to do a lot of experimentation but the expectation is that in the winter they'll contribute mostly to space heating and not much to DHW; maybe as a preheat which gets topped off by resistance heating from the PV.

I'm in Somerset. Near taunton

My comment" PV is dead long live solar thermal" was aimed at every decreasing funding available for pv(FITs) I'm assuming that without the government hand out sence will provail and people will choose, based on what is actually required not on a payment return?

I agree that subsidies skew a market, but there are places where subsidies are not available, or hard to claim, that are choosing PV over ST, Sub Saharan Africa and rural India.
These places, which have a need for thermal energy, have opted to get that via electricity.

In an ideal world every building would have a combination of ST, PV, Wind and Hydro that feeds into heat pumps, thermal storage and chemical storage.
Now that would be an interesting project to see if such a plot could be found and how much it would cost to just buy and self install the kit without bothering with all the legalities.

Bit tangential and left field (as usual...) but can excess heat in summer from solar thermal be used to generate electricity, perhaps via a Stirling engine?

Posted By: an02ewThat depends to the amount of sun? Listening to bbc yesterday it's been the warmest winter on record? February has been a great month for solar

In this area at least 'cold' winter weather is usually better for solar gain! 'Warm" winter weather usually means cloud.

For much of this week the mean 24hr temp has been between 2 & 3C but we seen more sun than for for a good while. In the last 7 days the PV has generated more than the whole of December 2015 (mean 6.8C) & January 2016 (mean 4.8C) combined (days are longer of course, but the difference in solar is far greater).

I can usually get two baths out of my 200 lt 'thermal store' (usually called a DHW cylinder) and I only run it at 50°C.
Not unusual for me to have a bath in morning (an hour or so after last charge up) and one 14 hours later.
So there is not really an issue with the store 'holding the temperature' as that is just about usage and insulation.
More about the best way to get the energy into the store.

We are totally wood fired for cooking heating and DHW using an Esse for cooking and DHW and a Dunsley Yorkshire for the central heating. It works reasonably well but if I was redoing the system then I would run the whole system off a Lohberger stove which also has the wood pellet option so that it can auto ignite at a preset time in the morning. Would not even consider the Rayburn when compared to a Lohberger but the difference is reflected in the price.

Posted By: TriassicFabric first?

EWI on exterior walls to help keep the place warm and the heat in?

Discuss...

Indeed. Being able to collect almost free wood is all very good (and laudable) now, when you're young fit and willing. But what about when you're older with failing joints? Or just don't feel like it? Insulate now and it'll pay you back in many ways later....

Seems I was wrong at least it has flushed out someone with first hand experience .

which was what was needed.

How much does a modern Rayburn weigh? the old ones weighed several hundredweight.

However I would still insulate as a priority it will make best use of all that hard won wood you have gathered .

Thanks for all of the comments as usual. Please don't feel the need to apologise for going off on tangents - I have found this very useful when looking through other threads.
I've not got to grips with the quote thing yet but in response to a few posts - I don't intend keeping a fire in all night and I just use the hand tools to make the timber small enough to haul back to my van or trailer, I process the firewood with a chainsaw after that. When I'm no longer enthusiastic or able to cut wood I hope to hire a young, enthusiastic, able person to chop it for me - I feel it is something I'd like to invest my pension in. Also I should mention that I'm not opposed to buying in a load of logs now and again, many of my neighbours do, I just like having the option to do it myself. This also puts me off pellet boilers- always in thrall to the supplier.
As for solar, we have a PV array thanks to the previous owner taking advantage of the very high initial FIT which we now benefit from. I hoped to tie this into the system by having three immersion heaters at different levels in the thermal store.
I've taken on board the advice that it is asking too much of the rayburn to do everything and currently favour the idea of having the living room stove feed the TS from a backboiler and have a split system for DHW and CH. I'll try to draw myself some schematics to get my head around a couple of different options (mainly to ensure that both summer and winter needs can be met and that the solar element can be utilised effectively).
Reports of the timescale for cooking on the rayburn are in line with my expectations.
Thanks everyone for the helpful advice.