SOLAR DIARY YEAR 1    30-08-08 to 31-12-08

A week by week account of how our solar hot water system is performing.

Battery Voltage ===== The current voltage of the battery that is kept charged by the P/V panel.

Panel temp ======== Temperature of the sensor that is fixed to the panel.

Tank temp ======== Temperature of the sensor that is fixed to the bottom of the tank.

Acc temp ========= Temperature of outlet pipe at the top of tank measured with accurate thermometer

Boiler set to come on from 6 to 7 AM and 6 to 7 PM for hot water

Important changes to the system are in red


With Autumn and winter approaching the heat gain from this setup will be expected to gradually get less, but I hope to keep this diary going just in the interest of research. It will be interesting to see how the system copes with freezing nights. And also how much hot water is made on sunny but cold days during the winter. If you are considering a solar system you may like to follow this diary. This will be a warts and all account. No exaggeration of results or non reporting of disasters.

Saturday 30th August 2008 at about 1.30 PM Finally got everything ready to go. Made a final check of all water and electrical connections. It was quite a hot day. I opened the two isolating water valves, connected the battery and waited for the controller board to set itself up. The display said: Battery voltage 12.80v: Panel temp 99C: Tank temp 23C. I was not expecting the panel temp to be so high. The pump was pumping for about 10 seconds every 15 seconds. The Pump was really noisy and I could hear it from downstairs as I made a cup of coffee. Starting to think I will have to put the pump in a sound proof box. I kept feeling the hot water return pipe, but it was not getting hot. I was wondering if there could be a blockage in the panel. I closed the hot return isolating valve and pulled off the pipe. There was no water in it at all, but I could hear hissing so I put the end of the pipe into a bucket and waited. To my great relief water started to flow from the pipe, and it was very hot. Steaming as it filled up the bucket. When the pump paused I quickly reconnected the pipe and opened the isolating valve. The pump is now very quiet. Must have been some sort of airlock in the panel. Pipe going into isolating valve is now reading 60C using a very accurate meter, but I think the pump may be pumping too much ( about 5 liters in 10 minutes ). I am not sure at the moment if my controller board is reading the panel temp accurately.

01-09-08 A warm day, but cloudy and windy with spells of hot sunshine. At about 12.00 a.m : Battery voltage 12.3v: Panel temp 67C: Tank temp 31C: Acc temp 50C. Pumping for 8 seconds every 15 seconds. I think it may be pumping too much and cooling the water in the tank after about 4.00 p.m.

02-09-08 A windy rainy day up to about 4 p.m then the sun came out for about an hour. At 4.30 p.m : Battery voltage 12.5v: Panel temp 51C: Tank temp 23C: Acc temp 30C.

03-09-08 Cloudy with spells of hot sunshine all day. At 1.30p.m Battery voltage 12.7v: Panel temp 90C: Tank temp 31C: Acc temp 65C. At 6p.m the boiler did not come on for the first time ever and the tank is full of hot water. I have reduced the pumping time to 4 seconds every 15 seconds and this is working better.

04-09-08----05-09-08 Both days overcast and raining. Have fitted a permanent thermometer under the insulation about 20 cm down from the top of the tank, for more accurate readings. I will try next week connecting the P/V panel direct to the pump. Just to see how this works out, but I still think that an electronic controller will be needed. Also plan to fit a water softener as soon as possible as I live in a hard water area.

06-09-08 Overcast and rain all day no free hot water today.

07-09-08 Overcast and rainy all day. Connected the P/V panel direct to the pump to see how a passive system works out, but no sun at the moment. Noticed that although the panel is at 45C the pump is not pumping because there is no direct sunshine.

09-09-08----10-09-08 Cloudy most of both days with some spells of sunshine. Panel temperature really shoots up when there is a spell of sunshine, pleased with this. With the P/V panel connected direct to the pump there are a few problems. When the sun comes out the pump pumps like mad and I think it would need a resistor across the pump connections to slow the pump down a bit. Probably would have to try quite a few values to get this correct. Also noticed that when the sun goes in, the pump stops whilst the panel is still hot. When there is very thin cloud the panel warms up to about 45C but there is not enough sun to start the pump. I think this type of system would work well where there is plenty of reliable sunshine and the pump is slowed down . There is some worry if the pump was to start pumping when the panel is frozen the pressure build up may push one of the pipes off.

11-09-08 It's no fun when there's no sun.

12-09-08 Tank temp probe is moved from the bottom of the tank where it always reads about 25C to a position about 20cm from the top of the tank under the insulation. Day starts off very cloudy and overcast, then about 1 pm the sun comes out and the panel temp shoots up to 84C at one point. The pump is pumping about 4 seconds every 15 seconds and the tank temp gradually rises from 35C to 45C over the next three hours. Then the clouds return. At 6 p.m. the boiler comes on for about 10 minutes and raises the tank temp to 47C then shuts off. Almost had a boiler free evening. The controller is now set so that the pump pumps only when the panel temp is 5C or more above the tank temp. P/V panel and pump now connected to the controller board.

13-09-08 Cloudy at first then at 11a.m the sun came out and there were long sunny spells all afternoon. Panel temp got up to 84C at one point and the tank temp was 45C about 5 p.m. Had to go out so do not know if the boiler came on, but it probably did for only about 10 minutes.

14-09-08 A nice sunny day all day. The panel was soon up to 92C and stayed hot all day. The water in the tank got to 51C and the boiler never came on at all. At about 10pm the panel went down to about 8C and the controller went into sleep mode as planned.

15-09-08 Not very sunny today. Panel max was 70C and tank max was about 42C at 3pm. Made some hot water.

16-09-08 Overcast. Panel max = 49C Tank max 45C.

17-09-08 Overcast. Panel max = 65C Tank max 45C. One thing I have noticed about these dull days is that although the tank temp does not get very high, there is much more hot water in the tank. It is getting hotter lower down.

18-09-08 Sunny day all day. Really pleased how things are working when the sun comes out. Panel max 90C. Tank max 50C. No need for boiler to come on.

19-09-08 Even hotter today. Panel max = 98C. Tank max 53C. Boiler never came on. Water is so hot in the tank that the boiler may not come on in the morning. £££££££.

20-09-08 Sunny day all day. Panel max = 92C. Tank max = 49C.

21-09-08 Sunny day all day. Panel max = 94C. Tank max = 50C.

22-09-08 Overcast day with some spells of sunshine. Panel max = 63C. Tank max 43C.

23-09-08 Overcast most of the day. Panel max = 47C. Tank max = 39C.

24-09-08 Overcast most of the day. Panel max = 41C. Tank max = 30C.

25-09-08 Overcast most of the day. Panel max = 71C. Tank max = 41C.

26-09-08 Nice sunny day. Panel max = 94C. Tank max = 53C. Pipe going into tank was too hot to touch. Boiler never came on and may not come on in the morning.

27-09-08 Nice sunny day. Used a lot of hot water today. Panel max = 94C. Tank max = 53C. boiler came on for 5 minutes at 6PM, but never came on the next morning.

28-09-08 Sunny day. Panel max = 92C. Tank max = 47C.

29-09-08 Sunny day. Panel max = 88C. Tank max = 50C. I have turned down the tank thermostat about 5C to 50C. This may stop the boiler coming on for about 5 minutes on some evenings.

30-09-08 No Sun.

01-10-08 Overcast most of the day. Panel max = 67C. Tank max = 39C.

02-10-08 Dull day.

03-10-08 Dull day. Still making some hot water on these dull days,but not much.

04-10-08 Dull day.

05-10-08 Rain all day.

06-10-08 Started off dull again then at 11.30 AM the sun came out for about two hours and made quite a lot of hot water. Panel max = 86C. Tank max = 49C.

07-10-08 Dull day.

08-10-08 Sunny day. Panel max = 94C. Tank max = 50C. No boiler on.

09-10-08 Sunny day. Panel max = 90C. Tank max = 49C. No boiler on.

10-10-08 Sunny day. Panel max = 85C. Tank max = 46C. Boiler on for about 10 minutes.

11-10-08 Sunny day all day. Made lots of hot water. Had a Eureka moment today.

see: Eureka moment Boiler came on for about 10 minutes, but we used a lot of hot water today.

12-10-08 Sunny day all day. Panel max = 88C. Tank max = 48C. used a lot of hot water today including pre filling the dishwasher. Don't know if the boiler came on.

13-10-08 Dull day.

14-10-08 Dull day.

15-10-08 Dull day.

16-10-08 Sunny day. Just about made a tank full of hot water and it was quite a chilly day.

17-10-08 Sunny day. Showers,Pre filled dishwasher, and no boilers on

18-10-08 Sunny day. Used plenty hot water. No boiler on.

19-10-08 Dull day.

20-10-08 Sunny day all day. Loads of free hot water. No boiler on.

21-10-08 Started off frosty. Then sun came out. Loads of free hot water, no boiler on. Really pleased with how quickly the panel gets up to 80C + on a cold day.

22-10-08 Average autumn day. A bit of sun. made some hot water.

23-10-08 Made some hot water, but not much.

24-10-08 Made some hot water.

25-10-08 Made some hot water. Sun getting low in the sky.

26-10-08 Dull rainy day.

27-10-08 Made some hot water.

28-10-08 Chilly day but panel still getting up to 75C. Made some hot water.

29-10-08 In my back garden there is some ice but its sunny, And the panel is up to 84C making hot water.

30-10-08 Cold morning, but sunny. Made some hot water.

31-10-08 Cold morning,but sunny. Made some hot water.

01-11-08 Rainy all day.

02-11-08 Sunny but not much heat. Made some hot water.

03-11-08 Dull day.

04-11-08 Dull day.

05-11-08 Dull day.

06-11-08 Dull day.

07-11-08 Sunny for about two hours. Panel max 70C.

08-11-08 Dull rainy day.

09-11-08 Dull rainy day.

10-11-08 Windy rainy day.

11-11-08 A bit cold ( 10C ) but, sunny. panel max 70C. Made some hot water.

12-11-08 A bit cold ( 9C ) but, sunny. panel max 68C. Made some hot water. Made some changes to the controller board. Battery was over charging a bit, so now fitted a voltage regulator LM 317. Going to try some other type ( L200 ) with lower quiescent current drain.

13-11-08 Dull day.

14-11-08 About 2 hours sun. Panel max 70C. Made some hot water.

15-11-08 Dull day with some sunshine. Made some hot water.

16-11-08 Dull day.

17-11-08 Dull day.

18-11-08 Dull day.

19-11-08 Cold start but,sunny day. Panel max 70C. Made some hot water. Going to use LM 317 to charge battery.

20-11-08 Dull day.

21-11-08 Dull day.

22-11-08 Cold start with some sun about midday. Made some hot water.

23-11-08 Snow to begin with, then some sun. Made some hot water.

24-11-08 Cold start with some sun about midday. Made some hot water.

25-11-08 Ice on the car windows and on the panel. Must have been frozen in the night but, the sun came out at bout 10AM and the panel got up to about 60C. Pumped for about two hours. Although to panel is not getting very hot the tank is getting full with quite warm water during the day. I am going to set the controller so that it shuts down when the panel is below about 20C. Just to make sure that the pump can't pump in to a frozen panel. Now decided to change to PIC 16F833 for the controller chip.

26-11-08 Dull day.

27-11-08 Dull day with some sun.

28-11-08 Dull day.

29-11-08 Dull day.

30-11-08 Dull day.

01-12-08 Really cold morning but, sun came out at 10AM and made some hot water. Panel max 58C.

02-12-08 Starts off really cold then sun came out at 10.30 AM. Panel max about 60C for an hour or so. Made some hot water then it clouded over for the rest of the day.

03-12-08 Really cold again to start with, then sun comes out for about two hours and makes some hot water. Panel max about 60C.

04-12-08 Repeat.

05-12-08 Repeat.

06-12-08 Repeat

07-12-08 Repeat

08-12-08 Repeat

09-12-08 Repeat

10-12-08 And the same thing again today. Starts off really cold with ice and frost. Then the sun comes out about 11.00AM for two hours and makes some hot water panel max about 65C.

11-12-08 Dull day.

12-12-08 Dull day.

13-12-08 Dull rainy day.

14-12-08 Dull day.

15-12-08 Dull day.

16-12-08 Dull day.

17-12-08 Started cold ( this has been the coldest December for about 30 years in UK ) then the sun came out for about four hours and filled up the tank with quite warm water. Warm water coming out of the bottom of the tank. Panel max 68C.

18-12-08 Dull day.

19-12-08 Started cold then sunny for a couple of hours made some hot water. Panel max 60C.

20-12-08 Dull day.

21-12-08 Special day. Today is the day that we get the least sunshine in the year. The sun is furthest away and lowest in the sky and its a dull day. This means that from now on things will only get better for solar people. 21-12-08 is the least sun and 21-06-08 should be the most sunny day. Mid winter and mid summer come about six weeks later due to ocean cooling and heating.

22-12-08 Dull day nothing doing.

23-12-08 Dull day.

24-12-08 Dull day.

25-12-08 Dull day.

26-12-08 Cold start with some sun around midday. Made some hot water.

27-12-08 Cold start with some sun around midday. Made some hot water.

28-12-08 Cold start with some sun around midday. Made some hot water.

29-12-08 Same again.

30-12-08 Same again. Panel max 60C around 12.30 AM.

31-12-08 Dull day.

YEAR 2   01-01-09 to 31-12-09


YEAR  3 01-01-10 to 31-12-10


YEAR 4 01-01-11 to 31-12-11


YEAR 5 01-01-12 to 31-12-12


YEAR 6 01-01-13 to 31-12-13


YEAR 7 01-01-14 to 31-12-14


YEAR 8  01-01-15 to 31-12-15


YEAR 9 01-01-16 to 31-12-16


YEAR 10 01-01-17 to 31-12-17


YEAR 11 01-01-18 to 31-12-18


YEAR 12 01-01-19 to 31-12-19


YEAR 13 01-01-20 to 31-12-20




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