EST Report on solar thermal

[Ted]

http://www.energysavingtrust.org.uk/Generate-your-own-energy/Solar-water-heating/Field-trial-of-solar-water-heating-systems

Results from studies of 88 systems (54 flat plate, 34 tubed) across the UK and Ireland.

[A.L.]

as usual from EST - low on detail 

[stannn]

I expect that Navitron will have something to say about the assertion that evacuated tubes are no better overall than flat panels. A lot of the report is common sense. The folks with both PV and solar water heating will now be able to add the daytime cost of running the mains circulation pump to their savings.
Stan

[TwoHorsePower]

It's only the annual yield they reported on. This doesn't mean a great deal. Pity they didn't chart out the distribution of that yield by month, as this would have shown that vac tubes have a wider 'useful season', and that plates (probably) deliver more hot water than can be used in good weather.

[billt]

From P9:

"Due to their higher levels of insulation, evacuated-tube collectors can produce a higher energy output from an identical absorber surface area than flat-plate collectors. However, this did not translate into higher annual energy yields in the study because the geometry of flat plate solar panels generally gives a larger absorber surface."

Seems a perfectly reasonable explanation.

[martin]

and totally overlooks the fact that flatties are far less efficient when the sun is anywhere but in an optimum position - vacuum tubes can accept the sun's output from a far wider range of sun positions and still deliver high outputs, whereas the flatties will be floundering.......... but then I wouldn't expect better from the bunch of otherwise unemployable at EST!

[skyewright]

They say they "contacted more than 150 households across the UK and the Republic of Ireland" and "worked with project partners and the wider solar water heating industry to identify suitable participants" but the distribution of test sites has some very large blank areas, e.g. almost the whole of Eastern England North of the Thames estuary. Nothing anywhere near Oakham...  

[Ted]

The entire south west of England is missing too - but you can only study people who say 'yes'.

[skyewright]

The entire south west of England is missing too - but you can only study people who say 'yes'.

Indeed. Getting 88 acceptances out of the more than 150 contacts is better than 50%, so probably not a bad rate of response? Might it not be strange though if the yes/no reaction showed a regional bias? There are several quite tight clusters of sites, which might possibly correlate to clusters of installs related to particular project partners maybe?

[KLD]

My reading of this report is that the most important variable in optimising the system output is customer education. A few percentage points higher "efficiency" (whatever that is, the reference point they used in this report is not stated anywhere) does little compared to adjusting ones DHW usage to the availability of solar heat, and the timing of the top-up by fossil fuel-powered backup heat sources.
The second largest factor is heat loss from the store, which again can be minimised by using the heat when it's there (that's essentially point 1 again), and by adding insulation.

Nothing much new here.

Klaus

[desperate]

I agree there Klaus, I was able to interrogate the controller on the system we installed in Kenilworth in June '09 and the next day ours that was installed in October '09, I made a note of the running hours as follows

These readings were taken on the weekend of 9/10/11
Kenilworth                                                              Cactusville

total  2651                                                             total  3070
year  950                                                               year   1416
month 32                                                                month 47
wk     27                                                                wk      31



These differences are I believe mainly due to the fact that the kenilworth system backs up a gasser that is set to heat the water once a day in the evening whether there is a real need to or not. Whereas at Cactusville I prowl around the place with my head in the cupboard quite a lot, and only allow the gasser to come on if there is a danger of a riot from within the shower     I guess the Kenilworth system is forced to reach a higher panel temp before switch on, of course there are lots of other variables, but do you think they could account for such a big difference in operating hours?

Educating punters, hmm an uphill battle.

TTFN

Desp

[KLD]

Educating punters, hmm an uphill battle.

The one battle that has to be fought and won, though. 

Klaus

[brackwell]

Not so sure its about education but more about life style choices that make the differences-
Size of household
duration/frequency of showers/bath
mornings or evenings or both
washing Mc hot fill?
Short duration running of taps
etc

It is probably because of all these variables that the report is so weak.

Whilst i have and am a total enthusiast of the technology i am not convinced it is a economicaly viable technology unless done on a DIY basis.    Further i remain convinced that it is not for jo public due to the fact that it is seasonal and unreliable.
 ( How many would have a car if it did not run in winter and not on days when it was raining etc)

It is not the problem of the customers but the failure of the industry to listen to the concerns of the customers and deal with them. A business that does not listen to its customers it not long for this world.

The customer wants to just use it and not have to take a degree course in thermodynamics first.   I have said before and met with little enthusiasm but the answer is the use of a inline heater between the solar storage tank and the usage point.  This can be a combi boiler or electric heater.  I favour the electric heater as it does not have the stop start losses of the combi and can also be easily retro fitted.

The inline heater JUST heats the water used to JUST the right temp (40C) with virtually no losses and is ensures that the system is always usable.

Ken

[martin]

Economic viability depends on what the householder would be using instead - if their only other choice is an immersion heater, then "payback" will be relatively swift - a lot slower if the property is on mains gas, BUT what is so often glossed over/misunderstood/ignored is the savings for environment - payback of embodied energy is swift, thereafter no fuels of any sort are being burnt (apart from a modicum of electricity for the pump and controller) during the months when you can rely on it for your domestic needs, and for probably at least a couple or more decades thereafter!

[StationHouse]

I priced up solar thermal earlier this year, best price was a shade under 4k for an MCS installation

Probably useful, or a nice to have, in certain circumstances but that is just a stupid price when our 14kw ecodan ashp complete with huge packaged kingspan tank was £6k

And for £10.5k I could have my roof covered in PV for huge returns...