thermodymic panel for water heating

Cardew

lynneinjapan wrote: »

However, the guy who quoted seems to have won my husband over with his talk of efficiency,

Get the salesman to put in writing some performance figures avoiding the use of terms like 'up to' etc etc.


If you lend me some money I will guarantee that you will receive interest rates of 'up to' 27.78%;)

Have a chat with the Energy Saving Trust about thermodynamic panels.

zeupater

lynneinjapan wrote: »

Reviving an old thread because we're looking at the possibility of installing solar thermal but the only company we've had a quote from so far were offering solar thermodynamic instead. We'd been reading up about the options and had decided against thermodynamic as (a) the products currently available are apparently better suited to the warmer climates of southern Europe and (b) it doesn't qualify for the Renewable Heat Incentive (I think because it uses refrigeration rather than water or glycol like solar thermal).

However, the guy who quoted seems to have won my husband over with his talk of efficiency, and also seems to have told him that it HAS now been MCS-approved and will soon be added to the RHI scheme, at similar rates to solar thermal if I remember correctly. Does anyone know whether this is true?

Hi

Looking at your post, the first major question which springs to mind is - what are you looking to achieve, is it purely domestic hot water or something else ?

Out of interest, what is the claimed performance of the system which has been quoted, where would it be mounted ? (roof, wall etc) and importantly, how much will it cost ? ... if you wouldn't mind sharing this information, someone will be able to comment on the suitability and possible alternative solutions which may not have been considered.

HTH
Z

lynneinjapan

We also considered solar PV (which we have on our own home - but we got that installed while the FIT payments were still high) but this house is going to be an HMO - i.e. several tenants each rent their own room and share a kitchen/lounge. There will be six rooms, each with its own shower room, and the tenants will be professionals so the majority of electricity usage will be in the evening, when solar panels wouldn't be generating. So for that reason we decided it'd be better to focus on hot water, as that can be stored for a few hours. I've been advised that we should allow 50 litres pppd so that would equate to a 300-litre tank. Bills will be included in the rent so the tenants will probably not worry too much about energy conservation - hence we want to make the house as energy-efficient as possible!

The other approach we were looking at was a solar thermal system with backup heating from a system boiler (house has gch, currently with a combi boiler, but major reconfiguration is required anyway). Considered thermodynamic but, as I said before, lack of RHI was a big turn-off and from what I've read it seems that the products available up to now haven't been optimised for the UK climate.

The house's roof is just about perfect for some kind of solar panel: it's a 9m wide, unshaded pitched roof (not sure of pitch but it's steepish so I'd guess around 30 degrees+) and facing about 10 degrees west of south. However, we're going to put a flat-roofed single-storey extension on the back and it was suggested that we put the thermodynamic panel there instead. Not sure of technical details but I think the claim was that the system would provide 90% of our hot water needs (year-round) and it would feed a tank of up to 300 litres (included in price). The price quoted was £8100 but there's some feedback scheme through which we could get it for £6450. From what I've read, though, it sounds like £4000ish should be achievable.

zeupater

lynneinjapan wrote: »

.... Not sure of technical details but I think the claim was that the system would provide 90% of our hot water needs (year-round) and it would feed a tank of up to 300 litres (included in price). The price quoted was £8100 but there's some feedback scheme through which we could get it for £6450. From what I've read, though, it sounds like £4000ish should be achievable.

Hi

Interesting ..... 6 rooms, all with showers ! - just make sure that they're not power showers - 300 litres isn't all that much so I'd reckon that there'll be a need for a regular shot of heat from the GCH whatever you've got on the roof, else it's cold shower for some ...

To be able to provide 90% of the DHW requirements for 6 adults the thermodynamic panel must be pretty large, or (and this is where caution is required) the system has booster elements - in which case the 90% provision could be costing some serious money.

Whatever system you go for it looks like you'd be looking to provide around 20kWh.t/day, summer, winter & between ... that's a serious ask for either pv or solar thermal, especially considering the variability of the weather! ...

Regarding the thermodynamic system, is there any further information on the quotation which you could share (no of panels, COP etc) .... I'm pretty sceptical on the some of the performance claims which I've seen to-date, however, there's always the possibility that a system 'could' be built to provide ~20kWh.t/day ...

HTH
Z

lynneinjapan

It was only going to be one panel; I got the impression that it was their standard offering. They claim "a COP rating of between 3 and 6".

zeupater

lynneinjapan wrote: »

It was only going to be one panel; I got the impression that it was their standard offering. They claim "a COP rating of between 3 and 6".

Hi

Did they tell you how much power the unit draws and the physical size of the panel ? (possibly available on a specification table in a brochure) ....

Z

zeupater

lynneinjapan wrote: »

It was only going to be one panel; I got the impression that it was their standard offering. They claim "a COP rating of between 3 and 6".

Hi All

Okay, it looks like someone is actually conducting an independent test on thermodynamic panels. The test is claimed to be the first one made on an independent basis, it also seems that MCS are interested in the test regime & results in order to formulate future standards.

Test .... http://www.narecde.co.uk/solar-thermodynamic-panels-independent-test-challenge-part-ii/#.U2U7nGdOW00

Test result data .... http://www.narecde.co.uk/solar-thermodynamic-panels-independent-test-challenge-part-ii/#.U2U7nGdOW00

You will note that for the first three month of this year the single panel system is struggling to achieve a COP much above 1.5 when drawing a mere 120l/day (5.8kWh daily heat replacement), even when operating with a relatively low tank-top temperature looking to average somewhere in the low 50's C with a 55C set point ....

Read into it what you will, but looking at the latest data (March '14), whilst the thermodynamic system on test was averaging around 4.5kWh of electricity/day heating DHW to the low 50s, our solar thermal was maintaining tank top temperatures averaging at least 10C higher with a ~20W pump, which was powered by our own pv system .... we used no gas at all to supplement the DHW this March.

To me, the test results are displayed in a confusing manner. The COP which they are claiming is a whole system COP, including cylinder heat-loss. To be able to compare with other heat sources the 'COP inc tank loss' is more representative and can be readily compared to something like an electric immersion at an effective COP of 1.0 or any form of ASHP DHW provision ... etc.

Anyway, the performance figures on the referenced links pretty much stack-up with my previous rough assessment of the technology from 2012, #35 on this thread ( http://forums.moneysavingexpert.com/showpost.php?p=56255949&postcount=35 ), so it's not really unexpected.

Regarding thermodynamic systems and RHI. It certainly looks like this technology is currently suspended from registration by MCS ( http://www.microgenerationcertification.org/images/2012%2011%2005%20-%20Letter%20to%20all%20installation%20companies%20re%20Thermodynamic%20Panels%20FINAL.pdf ) and with their 'Steering Group' having recently recorded an interest in this test, I would anticipate that they have done little to research the technology themselves, so the likelihood of there being any systems ready for inclusion to be extremely low.

My conclusion is that a decision to implement a single panel system to provide DHW for 6 rooms with showers will not only lead to extreme disappointment regarding heating provision requiring a regular GCH boost, but will have a far higher energy purchase cost than simply using gas and will unnecessarily add £thousands to the cost of your building work ... all with little chance of RHI assistance ...

HTH
Z

lynneinjapan

Thanks zeupater - it's going to take me a while to digest all that but your comments at the end confirm what I suspected: that it's very unlikely to be the bargain/miracle that it's being presented as.

So what do you think would be the most cost-effective option, given the situation of 6 working adults / 6 showers in the house, tenants probably having little regard for energy saving, and most of the electricity usage probably being in the evening?

(Already got pretty good insulation but may add to what's in the loft, and will use low-energy lighting throughout with PIR sensors in communal areas, and probably Nest or Hive or similar for central heating controls.)

zeupater

lynneinjapan wrote: »

Thanks zeupater - it's going to take me a while to digest all that but your comments at the end confirm what I suspected: that it's very unlikely to be the bargain/miracle that it's being presented as.

So what do you think would be the most cost-effective option, given the situation of 6 working adults / 6 showers in the house, tenants probably having little regard for energy saving, and most of the electricity usage probably being in the evening?

(Already got pretty good insulation but may add to what's in the loft, and will use low-energy lighting throughout with PIR sensors in communal areas, and probably Nest or Hive or similar for central heating controls.)

Hi

If you're paying the energy cost the solution is pretty clear ... concentrate on the highest value energy source.

Whatever you do go for, with 6 rooms with showers it's unlikely that any reasonable renewables option would provide a significant proportion of the DHW heat for a significant proportion of the year, especially from a 9m wide roof .... even more so if even one occupant isn't energy savvy and takes a couple of showers/day ...

Looking at DHW energy collector density, solar thermal would almost certainly provide more kW/sqm than solar pv, but I doubt that something like a 300l buffer would see you through even the shortest dull period, possibly not even enough to last 24Hrs without a top-up ....

Simply taking the roof as being ~9m wide, it's possible that you'd get 2 rows of 8 panels, so maybe 4kWp is the limit, maybe 5kWp at a push with higher efficiency panels ... so, in my view this would be the best option .... you're paying for running the shared kitchen equipment (which for 6 rooms would need a pretty large fridge & freezer), main & room TVs and most likely some multiple of the ancillary equipment (clocks, laptops, chargers, radios etc) which most homes would have .... it's not likely to be a 'low energy' household whatever you try to do, so offset the highest cost energy, electricity, and divert whatever spare power which is available (mainly summer) into the 300l DHW cylinder's immersion using a proportional controller to supplement standard GCH DHW.

If the requirement wasn't for 6 rooms (6+adults), or the roof space was larger, or the occupants were paying for their energy and therefore 'energy aware', then the answer would certainly be different, but I'm pretty sure that pv is the best and most cost effective solution in this instance.

Regarding a Hive/Nest ... I've no idea how anyone would expect to use one of these to control the heating for 6 individuals, all probably on different schedules (unless you intend to keep an eye on the settings, or control/ration the heat ) ... I'd reckon you'd probably be better off with a simpler 7 day cycle programmable thermostat with a manual override coupled to zoned control via TRVs .... there's probably also a pretty neat solution to control the gas DHW provision using a couple of cylinder thermostats in order to better control the heating cycle whilst maintaining a minimum buffer, but you'll need to talk to your installer ...

... as for insulation ... whatever you've got - look to put more in, after all, if there's no financial incentive to be cooler, who'd turn the thermostat down!

Incidentally, with all of those showers, have you looked into heat recovery ventilation as opposed to extraction ? (whole house or bathroom) .... it's an option worthy of a few hours investigation ....

HTH
Z

lynneinjapan

Lots of food for thought there, thanks. So it sounds like I should be looking at solar PV rather than solar thermal, and using any surplus electricity generated to heat water, though with the bulk of the water heating still done by GCH. Makes sense. We'd need to have a tank with system boiler for that, wouldn't we?

I don't have any personal experience of Hive/Nest, but they come highly recommended by other HMO landlords. The idea is basically just to prevent the tenants from whacking the thermostat up to 25 degrees and leaving it on for 24 hours a day. We can put a cap on bills, i.e. tell the tenants that if gas & electricity bills come to more than a set amount per month (say, £200 for the house) then we'll bill them for the excess, so that should encourage them to be a little less wasteful than they might otherwise - especially if we actually do it once or twice!

No, I haven't looked into heat recovery ventilation. Must do that.