Warm domestic water even on cloudy days.. (test)

[cyprusmax47]

Recently we had a lot of dull or rainy days with no or only a bit of sunshine with the result, that traditional cheap solar systems one can see on nearly every roof in Cyprus won't produce warm water (except you use the 3 kW electric element which is very costly)

As there is a quite new technology available in Cyprus now, imported from Germany, heating the domestic hot water with four photo-voltaic modules, I used this winterly weather conditions for testing both systems.

Beside the much nicer look of only 4 PV-modules on the roof instead of the ugly traditional installation my test results were very interesting.




We had several days with no sunshine and the result was, that from the thermosyphon system I received not even lukewarm water, just cold one. These systems need the heat of the sun in order that warm water starts to circulate between panel and hot water tank. Even in periods when sun appears for some minutes before the next clouds, the circulation will not start in cold days like now. Worse case if the panels are not mounted with ca 60 degree tilt.

Completely different story when photovoltaic modules producing electricity, heating a electric coil in the tank.
Four Good quality PV-modules (285 Wp) produced in my place on days without any sunshine app. 2 kWh per day, while on light overcast days I got 3.5 kWh/day. This would be similar if you switch on a electric 3KW coil (element) to heat water for ca 1 hour.

More information to reduce CO2 emissions in your household on the updated link from Green Air: "What's NEW" here on Paphos Life Directory:
https://www.paphoslife.com/directory/entry/greenair

Max

[Devil]

Max

Why spend the cost of 4 more PV panels, if you have PV on the roof, anyway? An ordinary immersion heater has ~99% efficiency in transferring energy from electricity to heating water, even with cheap heaters. Easy to add a relay that switches on solar water heating when the panels are producing and off when on mains supply.

[PolemIan]

For most people, this makes little economic sense. I track very closely how many hours we use our immersion heater for, last winter for example from 1/10/18 to 30/4/19 was a total of 48 hours and 45 mins. Roughly 150kw and approx 20 cents per kw so about €30 for the year, though in practice zero for us due to net metering. Payback in investing in an alternative would be be a long, long time.

[jeba]

Payback in investing in an alternative would be be a long, long time.

If it ever happened. My 4 kWp device produces more electricity than I´m using.

[cyprusmax47]

The topic was, that with photo-voltaic panels one can produce energy to warm domestic water in certain weather conditions like overcast, rain etc..while with thermosyphon it is hardly possible. It has nothing to do if some people have already PV installed or not. (good decision though)

The reason for the test was also for me personally to prove that situation, as in the past (1987) I had bad experience at my second house, where a installed cheap thermosyphon system, with low tilt, produced nothing even in sun & cloud conditions...In the end I replaced it with an quality product from Australia: Solahart

A big mistake in Cyprus is also that thermosyphon systems are wrong installed, facing North or West or are hidden behind a wall which gives all winter mostly shady conditions for the panels.

There are always people which want or have to replace their existing old system on the roof and have now the choice to buy a more advanced technology or high quality products from Wagner Solar Germany now in stock at GreenAir Paphos.
https://docs.google.com/viewerng/viewer ... cuterm.pdf

Max

[Devil]

I agree that many (most) solar panels here are badly installed. However, I question whether 'a more advanced technology or high quality product' can be amortised, compared with a correctly installed thermosyphon system from a reputable manufacturer.

[cyprusmax47]

I agree that many (most) solar panels here are badly installed. However, I question whether 'a more advanced technology or high quality product' can be amortised, compared with a correctly installed thermosyphon system from a reputable manufacturer.

It depends on the amount of daily hot water one needs, how many people are in the household, male or female (hairwash), children (they like to stay much longer under the shower) taking a bath or only shower, time of the day etc.etc.( and personal habits p.e., some people prefer to have a shower/bath only every other day...)
If one waits until the late afternoon on a sunny day until he uses hot water, a simple system perhaps will do the job, with the right position to the sun...

Max

[Kili01]

Perhapa a more affordable idea would be to install a Solahart, and a timer for the immersion heater? At present I have a timer on my ordinary heater which allows me to set it exactly in increments of 15mins up to 1hr. Usually if set to 15 mins, if heats plenty of water to do a nice hot shower.
Also with this timer there is no possibility of forgetting to turn it off!
Dee

[Jimgward]

The ideal situation would be a thermostatically controlled system, that ONLY used the immersion, when the sun didn't cope and heat the water sufficiently. Now, you couldn't have a simple system, since the water might be below the temperature at 5 am, but didn't need to be 'hot' - and you needed the morning to raise the temperature. That's quite a sophisticated piece of programming - needs AI with data from forecasts.