thermodymic panel for water heating

suffolkpumpkin wrote: »

It does look like a right thing for sure. But the chap said that you have to expose them to influx of air, strange to read that you can put them underground.

OK: what I've learned in a very simple language
1) the price quoted is too much (£8.9K, 1 panel just to heat water, new water tank, labour and everything else)
2) you have to accept that below -10C they don't work (or almost don't work) and you have to put the booster on.
3) it's not really advisable to paint them in other colours apart from black, so just as well you can leave them as they are.

So many thanks!!!!:T

Hi

I'd certainly get them to demonstrate a unit before you go any further, if that's what you intend to do ..... If the panels are 1.7mx0.8m each (less than the size of one of our pv panels) and you are being told that will provide ample heat for a 200l cylinder at a COP of 7, then that's something which would be ringing my alarm bells .... maybe a COP of 7 with a much larger evaporator (up to 7 panels in series ?) ... a low usage heated water requirement would probably still need around 6 to 8kWh.t of heat in a day ....

To me, I understand how the technology works and believe that if sized correctly the panels probably work well - but at £9000? ... :rotfl:... and compared to the alternatives? ... :rotfl::rotfl:... and a COP of 7? .. :rotfl::rotfl::rotfl: ... I'd certainly not be first in line with my chequebook ..

HTH
Z

Karen_Hird wrote: »

We got a quote for Thermodynamic Panels from Solar and Green based in Yorkshire and the guy who visited seemed very knowledgeable and our quote was for £6000 for hot water not £9000 as stated a in a previous email that's an awful lot more. I gained interest in these panels as they were at a show and i felt the hot water which was hot 55 degrees, they told me one panel heating the water in about 5 hours and the advantage of having 2 panels would heat the system quicker. Anyone had these installed? Any advice?

Hi

Do you have any further information regarding this ?. If the system is similar to that described by others, it seems pretty close to unbelieveable to me ...

Let's consider a 200l tank filled with mains cold water at 15C ... and let's raise this to 55C, a difference of 40C. Using a rough calculation that it would take approx 1.16kW 1Hr to raise 1 Tonne of water by 1C then raising 200l by 40C takes 9.3kWh(1.16x40x(200/1000)) of energy, so over the entire 5 hours the system must deliver an average 1.9kW (9.3/5) of power ....

The panels are 1.36m2 (1.7x0.8) and therefore in full equitorial bright sunlight at midday you could expect to receive a maximum of 1360W, in the UK probably no more than 75% of that, so approx 1kW (1.36x0.75), and then factor in reflection, angles etc that's a more realistic 500W over a 5 hour heating cycle as the sun moves around ... so even in bright sunlight a single panel system would need to absorb an extra 1400W from the air ....

Is this possible ? ... well, let's consider a radiator and reverse it's deltaT50 sizing .... a single panel radiator (unfinned) would be expected to be rated at around 1.8kW/sqm of panel (1mx0.8) therefore running the panel at -10C input/-5C output (-7.5C average) in ambient 10C conditions, an average differential of 17.5C, would suggest that the single panel could possibly (possibly !!) collect around 600W (1.8*(17.5/50)) ...

So, if it was a really bright day then a single panel system could possibly achieve 1.1kW of heating duty .... at night, possibly 600W .....

Now then, an earlier post mentioned a 390W compressor. Now depending on whether all of the 390W could be recovered as heat into the HW cylinder that now gives the following COP ...

Day, bright sunshine, midday, south facing .... COP 3.8((1.1+0.39)/0.39))
No effective radiated collection (night/dull) .... COP 2.5 (0.6+0.39)/0.39)

... note, neither of these are anywhere near a claimed COP of 7.0 ... the logic used above is rough and ready, but pretty sound and is based on concepts which most would understand (including simple folk like me ) ... I would consider the figures calculated to be generous and would not expect the panels to perform as well at night as the calculation would suggest (see previous posts) ....

At a COP of 2.5 gas would be a cheaper option and at a COP of 3.8 the system would just about start to recover investment ... throw in financing and nothing makes sense ....

I still maintain that solar pv or solar thermal would provide more benefit .... Add a second panel, or a third, or bury the panels and the dynamics change, but so does the cost ...

HTH
Z

1echidna wrote: »

I have to say Z I think your heat transfer for these plates under ideal conditions may be too conservative

This source quotes the total surface areas of these panels as 3.2 m2

Another source gives typical overall heat transfer coefficients for plates used as refrigerant evaporators as 12 to 14 W/m2K (table 8.23a)

Taking the most extremely good conditions I can think of, we have

Temperature of evaporation -26C
Ambient temperature 25C
Temperature difference 51C

Heat transfer = 51 x 14 x 3.2 = 2285W = 2.285kW

COP = (2.285 + .39)/.39 = 6.9

Therefore under ideal conditions, perhaps with a dollop of sunshine COP of 7 entirely possible.

Hi

I understand what you're saying, however, the effective surface area of the radiators I mentioned can also be doubled as they have two sides too, but at deltaT50 they still provide ~1.8kW.t/sqm of wall covered (~900W.t/sqm surface area) ...

Looking at your calculation In have some observations ... firstly, the average annual daily temperature in the UK is more like 10C than 25C, and although the temperature of evaporation could be -26C (depending on gas, it's probably more like -45C), this will not be the temperature of the entire plate, just the point where the compression pressure drops and evaporation occurs, after that the liquid is simply gathering heat until the next compression phase where it releases it again .... it's no use considering ideal conditions, what is needed is a 'real' world scenario, if not the 'ideal' could simply be used to mis-sell product, and no-one wants that ...

Take a number of these plates, fold them up , put them in a box and add a fan and you have an ASHP and we are all aware of the claims made by many manufacturers in that sector, however, I'm pretty sure that I've not seen many claims of a COP of 6,7 or 8 being possible when transferring to water at 55C ....

I remain a total sceptic on this product .... if the manufacturers want to have one tested by a sceptic, then I'm their man .... I've got pv and thermal, but these only cover about 20% of our roofspace and we have plenty of walls to cover too .... :cool: .... chances of a freebie to test, absolutely none ...

HTH
Z

May I ask some stupid questions?

Assuming (for arguments sake) that such a system runs at 390W, would that remain a constant energy consumption, regardless of the temperature differential outside (or in the tubes)?

In other words, would it make more sense to run such a panel(s) when the temp outside is high, and ideally when the panel(s) are in the sun, or would the 390W demand vary accordingly?

I'm wondering if such a system, whilst able to work year round and day or night, might still profit from intelligent interference, eg the MkI eyeball, or some sort of temperature activated switch?

It also occurs to me that such panels could be used to cool an office if placed internally, but I can't work out what to do with all that hot water, plus I'm probably just re-inventing some sort of A/C to water heating system that already exists and is far cheaper/efficient?

Mart.