If you have an existing gas combi boiler then its difficult to justify anything other than the simplest/cheapest solar thermal set-up. Even that would require finding space for a cylinder & putting up with standing heat losses in winter which you wouldn't get with a combi boiler. In terms of economics alone, its not a clear cut decision.

For a new build or retrofit off the gas network, I'd agree that you need some combination of solar thermal (for bright days) & heat pump (for dull days). However, I wouldn't trust the unsubstantiated claims of the only thermodynamic panel provider I've seen & I have concerns about the panels frosting in our more humid climate.

I would go for separate solar thermal drainback & air source heat pump systems feeding a common hot water cylinder or thermal store. Rotex offer some interesting systems based on a drainback solar thermal store & Daikin split system air source heat pumps.

David

We have been in our house for almost a year now, tried to build to passishaus standards and despite plumber, electrician and MVHR installation problems (see previous discussions if clarification needed), the thermodynamic panel is one piece of kit that i cannot fault. There is a backup immersion fitted and has never been switched on and we have had 60 degree hot water every day without fail. I have seen the panel completely white with frost and still no bother with hot water. I am in no shape or form connected to any company that sells or installs the panels, but I have no problem recommending the technology.

I've been trying to gather info on Thermodynamic Panels on my project blog.
- http://www.silverspray.co.uk/tag/thermodynamic-panels/

I've got a coastal cliff top site, so a normal air source heat excanger is going to have "fun" surviving the salty sea air. The site means ground source would be VERY expensive. So when I saw Thermodynamic Panels it seemed to be the perfect solution (for my project).

I understand they've been in use for many years in Ireland, and even longer in Spain and Portugal.

They are what I'm planning.

Anyway, have a look at the notes on my blog.

and great to hear the real user comment from "brogie2805" above.

Sounds like a great system but at £5500 a bit on the expensive side? If the price were to halve I might consider it!

I also found this information on payback times which some of you may find interesting - http://www.cernunnos-homes.co.uk/latest-news/thermodynamic-hot-water-versus-fossil-fuels/

I have had one of the heating systems installed on a new build house we developed and then retained as a buy to let. Occupied for a year nearly and the tenants seem very happy (and they like to house hot!). We have supplied a few of the hot water systems and again the customers are all very happy! However installation costs are a touch high and to be perfectly honest stop the product being a sensible solution in many places with mains gas.

They especially good if one has solar PV for the electricity they consume (PV produces enough even when its cloudy as they typically consume about 700 watts.

That said many other companies are marketing these as being eligible for the RHI - they are not I am afraid at present - in fact MCS suspended the registration of them from the Solar Thermal category a couple of days ago - effective 18th November. Suspended as it is not really solar thermal - they may create a category or move the product to the heat pump technology but one must assume no subsidies at present!

For my own house though I have opted for the ESP Ecocent (http://www.cernunnos-homes.co.uk/products/air-source-heat-pumps/) - similar unit cost but lower installation (no panels) and when integrated with ventilation (from bathrooms or MVHR) they are fantastic. Much better looking unit, with better controls, quieter (the Energie system is a bit noisy) .... It is classified as an exhaust air source heat pump so unfortunately not at present in the RHI ...

One point last point - either product has a slower recovery time than a gas/oil fed modern system so make sure you opt for a larger tank than the one you are replacing (typically 200 litre for smaller 4 occupants or less and 300 litre for larger homes/4 or more occupants).

Interesting. A cross between solar thermal and an air-source heat pump. http://www.cernunnos-homes.co.uk/products/energie-solar-thermal/ says that it can have Cop up to 8, but typically 3.5. It also says that typical solar thermal system have a COP between 2 and 1, which sounds wrong to me, or I don't understand how they are calculating it. Mine produces between 200 and 2000W with a 12W pump and 4W permanently-on controller. That's < ~6% parasitic load which makes for a COP of around 17. A COP of 2 implies 50% parasitic load which would be shocking.

Clearly this setup has major advantages for producing hot water even when it's not sunny, or even daylight. Quite how this works out over the year I don't know, but I reckon simple solar thermal with gas/electric fill-in is hard to beat. So yes these look quite good in comparison to fossil fuels, but that's not hard - I'd like to see a comparison with conventional ST.

Their website also says embarrassing things like: "It takes 4.18 kW to raise the temperature of 1 litre of water by 1 degree Celsius".

Posted By: SteamyTeaThe trouble with heat pumps is that they do not count the 'invisible' energy source, this could be the air, water, ground or solar. Add them in and you will always be below unity.

Why do you care? Its usually free & zero carbon.

David

Posted By: SteamyTeaThe Joule does not distinguish how it exists, but we do. Saying that it is free or zero carbon is not always the case.

The COP you should be found by dividing the valuable outputs by the valuable inputs. Otherwise-useless inputs and outputs shouldn't be counted. The fact that sometimes people are a bit misleading by ignoring this doesn't invalidate the concept, though.

Note also that a heat pump can be useful even when all of the inputs are “valuable” and the COP or efficiency or whatever you want to call it is less than one. E.g., it can turn the heat in a lot of tepid water into heat in a smaller amount of domestic hot water.

Posted By: davidfreeboroughInstead we need to educate people that there's more to an efficient heat pump installation than the COP.

Yes. I was at a meeting once and someone had said that he was going to connect the output of his heat pump into the input and get all his energy for nothing

That's a classic

Posted By: davidfreeboroughnstead we need to educate people that there's more to an efficient heat pump installation than the COP.

Please educate me further! What more is there? Price, serviceable life come to mind but I don't think that's what you're getting at.
thanks
RobinB

Posted By: SteamyTeaalways makes me wonder why people want to use them at night)

E7

Would have to work out the costs, both in cash and pollution to find out if it is worth running an ASHP, of different sorts at night. Oddly enough I am just running through the last 3 years weather data, but not sliced it into hours yet, takes long enough to just get it sorted into days. I think that it is this sort of thing that David was getting at when he talks of education.

All comes down to how large your HP and thermal store is as to whether it is better to run it at night or no.
Though I do urge everyone with this sort of technology to monitor it to find the sweetspot for them.

E10 may be the answer, just to throw something else into the mix, but when we get smart meters then we will all be on E48, or is that a cream to keep your fingers soft.

Here is a chart for the min temps and mean daytime solar intensity (sounds odd but they are daily averages) for near me.
Ignore any value that is actually sitting on the x-axis as they are null values (and I just can't get Excel to ignore them and leave a gap).
Trick is to now try and match the PV potential to the heat load.