Thermal Store

greevescat

Having just pulled our small old farm house back to basics, i would like any information possible as to installing a thermal store. we will have 3 bedrooms a bathroom 1 kitchen/utility and 1/2 small lounge areas. I would ideally like a range cooker to run off electricity .and radiators for heating in winter. We are planning on putting a back boiler wood burning stove in, 21 KW ? solar panels to run the range and hot water in the summer, ive been told 4KW and evacuated tubes ,will i also need an immersion heater for back up. I think that the thermal store would need to be designed for the input. I have been reading up about thermal stores and it seems to be a bit of a minefield as to what make, size, installation etc. Any help at all would be greatly appreciated

Reed_Richards

Are you sure you need the evacuated tube thermal solar panels?  The modern way is to use just solar PVs and use these to power your immersion heater with your spare summer electricity.  That would also simplify your thermal store requirement as it would only need a heating coil for water from your back burner and an immersion heater (and a coil or similar to heat your hot water).

Electricity has become very expensive of late.  I would check that you can afford to run your electric range in winter when you will have little solar power.  

Coastalwatch

Hi GC and welcome, don't know if I should read anything into your handle but I have an MDS and Hawkstone if of interest!

Equally of interest is the project you've laid out and seeking further thoughts upon. Having already gone through a similar process in recent times I quite agree with RR's post above.

It's great that you have space for 21kWp of panels and possibly a 3 phase supply also to go along with it. If not 10kWp would be the max and with DNO approval that is.

We installed a 210 litre thermal store(circa £1100) simply heated via two 3kW elements, a main and a boost powered by excess PV during summer, spring and autumn. During winter we simply use Octopus's cheap overnight rate. It's an off the shelf item so no need for additional design complexity or expense.

For space heating we rely totally on two very efficient Air2Air heat pumps(Air conditioning units) circa 3k to purchase and install, while you might need three so another £1.5k. Along with a COP of 4:1 (4 units of heat supplied for each unit of energy consumed) they will cool in summer for zero cost from the surplus energy generated by PV.

I appreciate the above is a little radical compared to your original thinking but once you've costed any alternatives you might find the approach favourable plus of course with no harmful emissions from a wood burning stove.

We also swapped out our gas hob with an induction replacement and love it. So responsive heat wise and vastly easier to keep clean.

Hope the above is helpful or at least gives food for thought. Good luck with your research in the coming weeks/months if you've any questions arising I'll my best to provide answers based purely on our experience and knowledge gained from guys on this forum. I'm sure others will post their thoughts also to give you even more to think about.

greevescat

Thank you for your comments, i am sorry for any misunderstanding.
the woodburning stove with back boiler is 21KW which i thought for the winter months to heat the property  and water in the thermal store
solar panels 4kw to store electricity and to run the Everhot range which uses 90kw per week dont know if its possible to store via battery or use it to run an immersion heater in the thermal store during the summer months.
the evacuated tubes would also warm the water in the thermal store during the summer months when the wood burner isnt lit.
these are only my thoughts 

Reed_Richards

greevescat said:

Thank you for your comments, i am sorry for any misunderstanding.
the woodburning stove with back boiler is 21KW which i thought for the winter months to heat the property  and water in the thermal store

What will you use the Thermal Store for?  Are you running radiators or Underfloor Heating from it (in parts of the house that your stove will not reach).  Or is it only there to provide hot water for the taps?

greevescat said:

solar panels 4kw to store electricity and to run the Everhot range which uses 90kw per week dont know if its possible to store via battery or use it to run an immersion heater in the thermal store during the summer months.

90 kWh per week will cost you about £30 per week at current electricity prices (£1560 per year).  But the average power is 535 W so you will still have solar power to spare when the sun shines in summer so a battery or running the immersion heater or both are all viable options.

greevescat said:

the evacuated tubes would also warm the water in the thermal store during the summer months when the wood burner isnt lit.

Yes, but the evacuated tubes are taking space that could be occupied by more solar PV panels that could also warm/heat the water in your thermal store via the immersion heater.  Current considered opinion is that that is the better option.
 

Pile_o_stone

I wouldn't touch solar thermal panels with a barge pole. They are more expensive than solar PV and they aren't 'fit and forget'. You have to worry about them freezing, boiling, leaking. Much better to have more PV connected to an immersion heater.

I'd also forget the electric range cooker. The only time your PV would be able to generate enough energy to offset the cost will be on days when it's so hot you'd rather be turning the stove off. Remember that your stove will be competing for power with your fridge, freezer, washing machine, TV, dishwasher, immersion heater, etc. etc. Range cookers are great for heating the immediate area around the stove, but for heating a house they are a poor substitute for an efficient condensing boiler or heat pump.

A wood burning stove is good if you have access to a lot of free wood and enjoy cutting, stacking, carrying, restacking and you have the storage space to hold all that wood for a year or more while it dries out and enough wood for the current heating season. If you are relying on it for your main heating and hot water then it'll become a real chore to light every day.

Sorry to be so negative but you'll either thank me or wish you had listened to me, depending on what you decide to do. Good luck anyway!

Coastalwatch

I guess with a renovated farmhouse, tradionally heated via a range and open fire then the temptation is to continue the romance. However, as PoS suggests it does come with it a certain amount of baggage and along with the aforementioned is that of emissions. While with a WBS most of these disappear up the chimney, each time the door is opened to reload the fumes then plume out into the room for everyone to ingest.

Just for comparison, a recent study discovered that whereas only 8% of properties utilise this type of fuel for heating the emissions generated are greater than all of those created by the land based transport industry.

Now that's a scary thought and implication for us all to bare in mind.