PV only, or Solar Thermal too?

Oscarmax

valiant24 said:

Hi

We're building a new house in Somerset. It'll be very well-insulated and energy-efficient ; almost a "passive house" but not quite ...

It'll have an air pump.   There are two options for heating: StoreEdge 5.3kW Solar PVs only; or 3.9 PV and Solar Thermal.  There will be a 10kWh StoreEdge battery.  The PV-only option is about £9k, and the PV-plus-Thermal £15k.   Can't really see the point of Solar Thermal myself on these numbers.

I wondered if anyone else has any experience, good or bad, and/or advice?

Thanks
V

PS One specification from the architect is MVHR (Mechanical Ventilation with Heat Recovery). Which is the best forum to ask about this on please? 

We can talk from some experience in 2008 we built a very large environment friendly 4 bedroom house, in those days solar panel were both horrifically expensive and less efficient, plus being in an conservation area we not allowed under permitted development.

However as part on planning application for some mad reason we had to fit solar thermal panels, it being both expensive and very inefficient, 95% of the time we heated the DHW apart from the height of summer. Personally I would give it a miss and go with the Solar panels.

ispookie666

For £500 you can add a hot water diverter and pretty much replace the Solar water heater. Use the saved money to buy batteries or more PV.  

zeupater

Hi

We have PV & a reasonably large thermal system (most years provides all DHW from ~mid March to ~early November) and think they're both great, but these days with the price/kWp for PV being pretty reasonable I'd only recommend to go for thermal if you're looking at heating DHW with solar but are restricted on roof space as it's far more efficient (kW.t/sqm), especially if vacuum insulated ... if you're not restricted on roof space just fit a proportional diversion switch & increase the installed PV capacity as the energy collected/generated provides you with far more flexibility in what you can actually do with it  ...

Anyway ... in addition to comments on the price for the PV being a little high, I'd guess that the thermal could also be open to research & some flexing of negotiation skills.

HTH - Z

mnbvcxz

solar PV captures about 20 something percent of the sun's energy. 

Solar thermal captures about 80 something percent of the sun's energy 

So a square meter of thermal is dramatically more productive than pv.

But put the solar PV electricity though your heat pump at an optimistic cop ratio of 4 and you end up with almost the same amount of hot water in the end....  Plus you can run the PV all day exporting it for money or using it. The thermal in summer will heat your tank by noon and then just cycle churn the fluids around your house around trying to stop overheating.  The cost of plumbing is high too.

So if you have limited space or are capable of doing the plumbing yourself then thermal is amazing. But otherwise PV is better, especially when combined with a heat pump.