Finally at 60C

[Ivan]

My solar thermal system provides only a small contribution towards our hot water requirements during November, Jan and Feb (achieving no more than 35C), but it starts to improve in February, exceeding 40C on good sunny days. March however, sees a great improvement, and by the 8th March, every day, temperatures exceeded 50C (As we've seen for the last 4 or 5 years, once again great sunny weather for much of March). Last week, we were tantalisingly close to 60C, reaching 57 or higher on several days. Two days even hit 59C, but we took advantage of the hot water and high output from the PV array to do dishwashing and clotheswashing whilst the sun shone, keeping it from hitting 60C. The hot water has been virtually entirely solar-heated for over a week, and on Sunday (21st March), we finally did it with an end-of-day bottom-of-cylinder temperature of 62.1C

[murraymint]

I am really considering installing DIY system this year and have a question about how you use your hot water produced by solar. Do you find you need to modify your personal behaviour in respects to using the hot water, do you shower at different times and as you have already intimated use the washing machine any differently?

[Billy]

I would be rather pleased with 35C as my stored water seems to average about 8C.  35C I could shower in that!  Positive luxury.   

No changes for use, use shower in morning as usual.  Only two of us mind.  In the summer I can connect the pressure washer and use it as a hot washer such is the abundance.

billy

 

[Alan]

No life style change required. Go large on the water tanks and
add as many lagging jackets as the house size will allow.

With lots of volume and insulation the water is ready for use.
November till end of February you will need an additional heat input.

Here with two Megaflows ( total volume 450 Ltr ) the tanks sit above
60 Deg C most of the time.

One tank is in the loft near the panels.
The other tank is down stairs in an outside toilet.

Link to old posts here.
http://www.navitron.org.uk/forum/index.php/topic,12538.msg138760.html#msg138760

South facing roof, go for it.

Regards

Alan

[greentangerine]

My store has been hitting high 70s (and even low 80s) most of this month.  It's providing more or less all our hot water now.

[profp]

My store has been hitting high 70s (and even low 80s) most of this month.  It's providing more or less all our hot water now.

60s here - and surplus PV for a good part of most days now, hooray! Shame I don't have more batteries to store it in...

[DonL]

I too have been seeing that big improvement this month and am getting sufficiently solar hot water most days.
A question: I noticed on one of the schematics for the solar controller that there is an option to have two solar coils in the tank with a diverter valve which directs the solar circuit to the upper coil until upper temperature is satisfied and then directs it to a lower coil.
This would seem to have a lot of merit in marginal conditions, producing a smaller amount of hotter water rather than heating the whole tank luke warm.
Anyone used this system? and with what results?
Don

[dhaslam]

Best temperatures for bottom of cylinder (solar only)  were 45C in December,   49C in January, 62C in February and 58C in March.  These are just   from isolated daily readings and are not necessarily the peaks.   

[tz0c0s]

Ivan, how big is yours ? 

Andy

[Ivan]

I've got a 260litre tank. Probably about right now there are 4 in the household, but it was too large for three people. Large tanks = extra heatloss = extra tubes needed for a given water demand. So no point in over-sizing.

Our water has been entirely solar-heated with the exception of one day where the water temperature reached on 44C, otherwise it's been 57-62C at the end of each day. I never cease to be amazed at how suddenly solar power switches on in March.

Yes, we do modify our behaviour due to solar hot water and solar PV. Firstly, we use thermostatic mixer showers, manual hot-fill in the washing machine and hot-feed on the dishwasher (the hot-fed white goods are responsible for a 20% reduction in our electricity consumption). Because we're using solar-heated water, we tend to wait until the water reaches 55C+ before running dishwasher or washing machine, or put it off until the next day, if it's not sunny. It's a compromise between maximum temperature of hot water and making sure we get the machines running whilst the sunshine is at its strongest (ie highest level of PV output). Currently we're exporting twice our daily cosumption when it's sunny. In mid-summer we export 4x our daily usage.

[tz0c0s]

Thanks for your reply Ivan. I was thinking also of your litres/tube ratio?

A hot fill washing machine encouraged to use hot water I understand, but with the dish washer.... Do you make any attempt at limiting the incoming water temperature other than possibly a whole house TMV? I assume you are simply filling a standard cold fill one with hot water?

Regards Andy

[profp]

Thanks for your reply Ivan. I was thinking also of your litres/tube ratio?

A hot fill washing machine encouraged to use hot water I understand, but with the dish washer.... Do you make any attempt at limiting the incoming water temperature other than possibly a whole house TMV? I assume you are simply filling a standard cold fill one with hot water?

Regards Andy

Can't speak for Ivan obviously, but what we have on our washing machine feed is a thermostatic valve intended for use in pubs etc. to limit hotwater temperature in basins. One side is fed from solar thermal, other side is fed from rainwater stores, with the output set for 30C (adjustable if you prefer a higher temp, that's just our personal choice).

[wookey]

Just to echo Ivan's observation that suddenly the solar gets a lot more useful in March. I think it's mostly to do with the shape of the insolation curve - this is the equinox so the point of maximum slope on the graph (i.e things are changing fastest). We hit 73C top of tank on the 7th and it was 86C yesterday, so we may be heat-dumping by this afternoon. (Bathroom soil pipe was being moved last week, so hot water usage somewhat reduced :-) ).

http://aleph1.co.uk/munin/wookware.org/control.wookware.org-heating.html

(BTW ignore the fact that purple is labelled 'tank-base' on that chart - it is in fact tank-top)

[Paul Bradford]

Hi All,
We're hoping to get to 60c soon this year. A bit different for us as we live in SW France. The system has been installed 8 months. We did hit 60+ last summer, but to be honest I wasn't taking as much notice as I should have, I was just enjoying the hot water! Today (time now is 1820hrs) the outside temperature in the shade is 24c. Temperature at the collector is 68c and water temperature in the middle of the 200ltr tank is 57c. I have a standard 20 tube collector. Roof pitch is around 34 degrees and we face directly south. We have oil fired central heating. We had noticed that our fuel requirements have dropped quite a bit.
We are just going ahead (hopefully if it gets passed for planning) with a 4kw PV grid tie system. I would love to have sourced one in the UK, but we have a concern that EDF might be awkward about commissioning it. I'm seeing the Bank Manager next week as there is a strong possibility that we will get a 12 year interest free loan to install it as well as almost €4000 tax credit.
I'll keep you updated.
Paul