May 2009 Temperatures

[dhaslam]

Best temperatures  today, so far,  but the period of clear skies is about to end.     20 Kwh today.  Heat dump operated four times and each time raised the 850 litre buffer tank by one degree.  
On 2nd May at midday the heat transfer reading reached 10,384w when the panel was at 61C and the bottom of the cylinder at 24C.  Hard to believe a 10mm pipe can carry that much heat.  60 tubes 250 litre cylinder

[Ivan]

Yesterday was our worst cylinder temperature for quite a while - this morning, the top of the cylinder was only 51C, and I guess most of the water below it was only 35-40C, as we had very little sunshine over the last couple of days. However, we had a brief spell of sunshine this afternoon (an hour or so), which recovered the cylinder temperature to 57C at the base by the end of the day. I think we've only had the boiler on to heat water twice since the first week of March.

[Ivan]

We've been on 100% solar-heated water since the first week of March. Today we hit another record - 84C recorded bottom of cylinder. The SFA panel in my back garden was boiling 140litres of water all afternoon (you can hear it glugging away, as well as the plumes of steam coming out of it). I even had Radio Wyvern playing from an FM radio powered by the heat of 4 Navitron solar tubes.

[Dan]

its a East west installation in south yorkshire

East 20 tube panel 
172L tank
West 20 tube panel

I have been data logging on the TDC3 since Dec 08 and the KWH readings are something like this ( difficult to read off the graphic monthly output)
 
Dec              10 ish
Jan               60 ish
Feb              116 ish
March           330 ish
April             348 ish
May             326 ish to date

Total             1190Kwh since dec
pumps operating hours is 335 hrs

Best temperature to date was 75C bottom of the tank yesterday.

[dimengineer]

Sorted my system out in April, and heres a graph of the May results.

Just to explain, its a log of the solar flow temperature, which tracks the bottom of tank temeperature (while the pump is running). By the miracles of dubious thermal contact etc, what I measure is within a couple of degrees of the actual tank bottom temps (conditioned by observation).

I know the whole tank is at or above the peak temperature measured at the end of the day.

250 litre tank, 21 tube Kloben panel, W London. S facing panel.

Tim 

[rt29781]

The beginning of May was wet in SW France but then the sun came out.  Here is the PV output so far this year.  The solar thermal is roughly 3 times the PV output so 1200kWh For May.

[billi]

rt  is it mainly 3 times more of solar thermal compared to PV during the whole year ? or is this in summer only?

how does the PV  and the solar thermal behave on overcast days ?

thanks Billi

[dhaslam]

April and May were very patchy months with no decent periods of sun until the last few days.    Once the output goes over about 14KWh the heat dump transfers  the surplus to the buffer tank and the buffer tank (850 litres) has risen to 41C  so about 21KWh added in the past few days.  Output in April was 302 Kwh total and May 347 but 20 of that was on the extra last day.

[rt29781]

Hi Billi,  I have measured the relationship between PV and Thermal output of our system several times and the ratio has always been about 3:1.  On a cloudy day neither system performs well and therefore measurement is difficult to perform accurately.  I suspect the ratio would fall from 3:1 Thermal to PV to maybe 2:1 but this may be purely because of the difficulty of calculating the numbers.  Certainly it doesn't matter in the scheme of things because output on a cloudy day is a fifth or less of that on a sunny day so the average ratio stays about the same overall.  In summer I will measure the ratio again as I suspect the PV output will be a bit less because of the higher temperatures.

[sjaglin]

Here are the results for the PV in Sunny Bristol (2.1 kWp installed):



There is also a daily detail on my website...

May was good but not as good as I though, we still had to have the heater on a couple of evenings... PV worked well and the hot water was 70 top to bottom several times.

The hot water system concerns me a bit as when the 70 degrees is reached on a sunny day, the summer setting kicks in and stops the pump until the liquid in the tube reaches 160 degrees then the pump goes a bit to cool down. We are going on hols in 2 weeks for two weeks, will the system overheat? The other day the temp in the tubes went up to 135 andI could hear it boiling + the pressure shot-up to 3.2, is 160 as a max a bit too high (manufacturer settings= Resol).

Stef

[Dan]

its a East west installation in south yorkshire
East 20 tube panel 
172L tank
West 20 tube panel

I have been data logging on the TDC3 since Dec 08 and the KWH readings are something like this ( difficult to read off the graphic monthly output)
 
Dec              10 ish
Jan               60 ish
Feb              116 ish
March           330 ish
April             348 ish
May             471 ish

Total            1335 Kwh since dec
Total pumps operating hours is 375 hrs

I suspect that the flow rate I entered in the TDC3 is wrong hence the figures but the best part is since the end of march we have only used 28m3 of gas (318Kwh) 

[billi]

179 kwh   in May from the 1.6 kw PV  panel  in south west Ireland

solar hot water is cooking at over 100°  in our solar water heater in the garden 

Billi

[langstroth2]

20 days in May where the HW cylinder reached an average of at least 50C by 7pm entirely from solar heating (more often than not over 65C).

[johnn]

Hi, you mentioned 3.2+ pressure, anything over 3, your pressure release valve will lift reducing the build up. I am hoping to avoid this by putting a thermostatic bypass in that will go to a heat sync/radiator. This will lift on temperature only which is the route of the pressure rise. That brings me on to my question if ok - I am a heating engineer and had decided to go over to solar hot water. I thoroughly enjoyed planning the system and picking certain components that I knew were reliable or better made only to be stopped in my tracks by my good wife saying  'what about PV electricity?' (so solar hot water is on hold). I noticed you have had yours installed in Bristol, I live in Bath and I will get an electrician to carry out grid connection and import/export meter but I don't have any idea where to buy and what to buy. I would be grateful if you have any advice.

Thanks in anticipation.

The baked cake looked fantastic.  John

[Ivan]

Well, asking on the Navitron board, you won't be surprised to get an answer that you should buy from Navitron! It is good advise though - Navitron has excellent quality panels, excellent prices (discounts if you're purchasing full systems) and free technical advise.

Back on topic:

Today, I had to run off several gallons of hot water to keep cylinder below 95C (it actually reached 93C). This weekend, I'm going to permanently shade one bank of panels until the weather cools down. At the 80+C temperatures the cylinder has reached most days recently, we've got about 4days worth of hot water stored, so there's no desperate rush when the sun fails to appear. I'm also wondering about installing a 10000litre+ heatstore in my basement for a few weeks of early autumn space-heating.