If you were retrofitting solar for dhw in 2016 would you fit tubes or a thermodynamic

batman1

If one was considering retrofitting solar for hot water, is there much comparison on the tubes vs thermodynamic panels ? Reading online there appears to be pros and cons to both but the thermodynamic system seems to be gaining followers as it becomes more popular.

BryanF

Tubes

Calahonda52

batman1 wrote: »

If one was considering retrofitting solar for hot water, is there much comparison on the tubes vs thermodynamic panels ? Reading online there appears to be pros and cons to both but the thermodynamic system seems to be gaining followers as it becomes more popular.

On the internet, where anything goes, where nothing is real and punter manipulation by snake oil sellers is king.

A question: make the, longterm, economic business case for the project.

Not for us here, just so you articulate your thinking

batman1

Very helpful

quentingargan

I would perhaps hold off until the announced subsidy regime for photovoltaic is introduced and see what the nature of that is. If it is an "export" tariff where you get paid for surplus power exported, then the electricity from it would subsidise a thermodynamic system's consumption while you still get paid for your surplus power. If it is a "production" tariff, then you can install it and use the surplus electricity to heat your hot water using an Immersun or similar device. PVs have come down in price so much that they are now a cost-effective way to heat water with none of the antifreeze and other maintenance issues associated with tubes.

batman1

quentingargan wrote: »

I would perhaps hold off until the announced subsidy regime for photovoltaic is introduced and see what the nature of that is. If it is an "export" tariff where you get paid for surplus power exported, then the electricity from it would subsidise a thermodynamic system's consumption while you still get paid for your surplus power. If it is a "production" tariff, then you can install it and use the surplus electricity to heat your hot water using an Immersun or similar device. PVs have come down in price so much that they are now a cost-effective way to heat water with none of the antifreeze and other maintenance issues associated with tubes.

Thanks. Could you indicate whether it would be feasible cost wise to go for solar pv? My southerly roof space is not huge. Also, could you recommend vs company by pm who I could get some advice /planning from ?

quentingargan

batman1 wrote: »

Thanks. Could you indicate whether it would be feasible cost wise to go for solar pv? My southerly roof space is not huge. Also, could you recommend vs company by pm who I could get some advice /planning from ?

Solar PV for retrofit sites is in a bit of a quandary at the moment. There is an incentive scheme promised but nobody knows what this will be, or if it will be retrospective. Will PM you.

ferryman35

Thermodynamic Panels are basically heatpump technology is a different package and the jury is very much still out on them.

Any solar is a longterm bet - so its important to put in a good system so that you get your payback.

Tubes / panels seem to get a bad press, but then the standard spec seems to be to put 6m2 worth of cheap tubes onto a 300l cylinder. Whereas the better renewables suppliers will specify 100l of water per m2 of solar collectors. Also, hooking the solar thermal only up too the dhw means when that cylinder is fully heated you have no more capacity left to absorb energy....i.e the sun could be belting away and you're missing it! The way around this is to use a bigger buffer cylinder and integrate the harvested solar energy with your heating system as well as your dhw. A very clever idea I came across recently was where an individual was using solar panels to 'recharge' the ground via his ground loop collector - i.e. using the planet as a storage heater!

PV is simple and could become very effective if the right FIT scheme is developed,but I would have concerns that the system would be very well designed. Its important that a hw cylinder is heated to 65'C at least weekly to sterilise the water, whereas 42'C is plenty hot for most of our needs. If a system was operated such that a PV array could get the water to usable temperatures but no other additional sources were used to bring the cylinder up to 65'C it could be a breeding ground for Legionella. In theory the same is also true with other solar setups but they tend to boil so its less likely!

batman1

Many thanks for the replies. Our current setup is a small copper tank Fed by both oil boiler and stove. However in the summer we can't just heat the tank unless the radiators are heated also. Therefore we use the immersion daily or twice daily to heat water for showers and as the tank is so small we only get enough for one or two at most and certainly not enough for a bath.
As I'm currently planning a refurb I was hoping to get a solar system fitted which I would hope would be beneficial both in the summer for hot water and also in winter to assist in the heating system working faster through the stove etc by having the minimal solar gain warming the cylinder some bit.