Hybrid PV-Thermal panels

mrawkward

With PV not covered by SEAI grants, are these hybrid PV-T panels a viable solution and avail of the grants?

In addition, the cooling effect of the thermal part also appears to increase the efficiency of the PV element on hot sunny days.

Located in South Dublin, bungalow (140sqm) with due south facing c30deg pitch concrete tile roof, Mitsubishi Ecodan 8.5KW Air Source Heat Pump system with an Ecodan_EHPT20X-VM2HB_Monobloc_Cylinder and low temperature radiators.

Anyone got any ideas/experience of interlinking the thermal output to the existing heating system.

quentingargan

An effective PV system of, say, 2kw is 12 sq m of panels. Most domestic hot water systems only require about 4 to 6 sq m. . It is probably more cost effective, if putting in PV, to add more panels to provide electricity for hot water via a diverter than to have two separate systems, one of which is spilling its surplus power to the grid.

mrawkward

It is indeed a fascinating topic to which I have never given any detailed consideration other than insulating my house and putting in a heat pump system. I thought the PV-T panels would be interesting to link the thermal output to a 500 litre dual coil solar water store (17.5 KWh storage equivalent at 30C over ambient) to run the heating over night. The cost is but a fraction of the same size battery store but clearly only applicable if you can use the thermal store...with a heat pump system being ideal. The PV would then be used 100% to run the pump and heat house and the solar store. Using night rate electricity would keep top up energy costs to a minimum along with running dishwasher and washing machine at night.
Or perhaps I have it all wrong?

quentingargan

Batteries are falling fast. And when smart meters come in (which they will) the most expensive electricity will be between 4.00pm and 7.00pm, which will all be met by any half-decent battery pack.

I think this is a more likely direction than storing heat as hot water. For a start, solar in't great at space heating - it works best when you need it least. But water systems require maintenance and have stagnation issues during summer holidays etc.

mrawkward

I am not proposing to use the solar store to heat space directly but rather to store the energy as heat to feed the heat pump system when PV is low/non existent. https://www.engineeringtoolbox.com/energy-storage-water-d_1463.html

You do seem to be ignoring the whole heat pump/thermal storage opportunity but as you do sell battery storage perhaps that explains it.

quentingargan

mrawkward wrote: »

You do seem to be ignoring the whole heat pump/thermal storage opportunity but as you do sell battery storage perhaps that explains it.

To date, I haven't sold battery systems because the cycle cost of batteries has been too high, though I do think Li-Ion is coming down in price to a point where they will be viable. In the absence of a FIT or for anyone wanting to stick up two fingers to the utility companies, it has a certain attraction. :rolleyes:

But even when I was working in the solar thermal industry, I always argued against people putting in large thermal systems to use for space heating. I still think that the heating gain in a well insulated house mostly comes at the wrong time. That is different in other countries where you get a lot of sunny cold days.

But you are right - I wasn't factoring in the heat gains of solar storage for pre-heating to a heat pump. That is an interesting aspect to explore.