Solar PV & Thermal Store idea - feedback appreciated

[pharma]

I am hoping for some advice. I have both Solar PV (1.8kw) and Solar Thermal. The PV is great, the Thermal has been disappointing. I have room on a west facing roof for a 2.4 kw Solar PV system that I am thinking of going ahead with (rather urgently following the new deadline!) at the same time as installing an EMMA (Energy and Micro-Generator Manager) & Thermal Store. My hot water tank and boiler is currently in the loft. The water then runs across the loft and down into my spare bedroom before going around the rest of the house - it is a good 20-odd meters before the first tap - hence why I am probably disillusioned with the Solar Thermal (ST).

My latest plan is to create an airing cupboard in the spare bedroom to house a thermal store and the boiler that I will have moved from the loft. I will let the solar thermal continue to heat the hot water in the loft and then the pipes from the hot water tank will run through the thermal store. I will let the DHW pipe and central heating pipe come out of the top of the TS (I don’t have to preserve a hot area for DHW as it 'should' be fairly warm from the hot water tank). By doing this I can throw everything at the central heating. My plan is to feed the EMMA from the Solar PV straight to the thermal store and hope to let the TS get to, say, 95C where possible. If the TS gets to, say, 60C then top it up with the boiler.

The benefits of the above as I see it are:
1)   Constant Solar hot water from late spring to early autumn - even a couple of bad days for the Solar Thermal will be offset by a good reserve in the thermal store.
2)   Bring the final heating source for the DHW (the TS) closer to each tap will improve efficiency –both in heat and reduce the amount of water I ultimately use waiting for the heat to come through.
3)   By allowing the Central Heating pipes to come out of the top of the thermal store will mean more of my CH will run from solar than gas – might even take care of all late spring and early autumn requirements??
4)   Any heat loss from the TS will go into my spare bedroom and may even mean running one radiator less in the house

That’s the plan – does it sound realistic? If so, how large do people think my TS will have to be (4 bed and 4 people house)? Can anyone suggest any improvements?

Even if it passes all of the practical tests above, it still has to go through the pure random process of obtaining agreement from my wife – so still plenty of hurdles and such little time!

Appreciate all comments.

[knighty]

can you draw up a diagram ?  (doesn't matter if it's not great)

to give us a better understanding of what you plan to build :-)


EDIT: p.s. how much does the EMMA cost ? the last ones posted on here were pretty expensive.... meaning they had a 10+year payback perios over just using the gas central heating

p.p.s. I'm assuming you have radiators and not under floor heating ?

[regen]

1. existing 1.8solar plus proposed 2.4 solar = 4.2 which takes fit into lower rate and is more than 16amps so requires DNO approval.
2. Was the existing solarpv and solar hotwater a package for fit socheck if pv add on is possible.
3. Moving a gas boiler will be expensive- maybe better to just insulate pipework to higher std.
4 Emma is not cheap
5.  Thermal store required will be 250 litres plus.
6. I would look very hard at costings and payback.
7. Are you proposing to utilise the spare pv capacity for heating if so the contribution may not be great enough to justify cost.

Regen