Solar Hot Water Heating Performance Graphs 2007 - 2008
I have now completed monitoring and performance graphs for a full year of operation . Performance is not so good in winter, but improves greatly when the sun shines! My hot water cylinder element is set to switch at 55 degrees Celcius, so when the holding cylinder is heated above that temperature and hot water is drawn through the thermostat will not switch on and power charges will drop. I am recording the times when the heating element switches on and off to the nearest minute. Data collection is continuous except when the battery goes flat in the datalogger (three glitches but only a few days data lost).
Temperature is recorded off the monitoring panel which is +/- 2 degrees. The monitoring point is in the middle of the cylinder and I have noticed that when hot water is drawn off slowly it can take a while before the temperature equalises and the sensor temperature drops. Similarly, if large amounts of water are drawn off quickly the cold water circulates faster causing the sensor temperature to dip quickly, and then rise again slightly and stabilise. A temperature profile of the tank would be more accurate, but involve many more sensors.
| Statistics over period June 2007- March 2008 | |
| Max temperature of solar tank (collector will be 8 - 10 degrees hotter) | 84° Celcius (30 November) |
| Highest daily temperature gain of solar tank | 44° Celcius (21 December) |
| Longest continuous period water heater element is on | 76 minutes (14 July) |
| Longest continuous period water heater element is off | 62 hours (25-28 January '08) |
Main hot water cylinder on time in hours on a weekly basis
Daily high and low temperatures for the 270 litre holding cylinder attached to the solar collector
Main hot water cylinder power usage in hours (1500 Watt element) - there were 12 days during the year when the heater element did not operate
(The weekly peaks mainly seen during winter are due to washing machine usage)
Graph above shows the difference between cylinder high and low temperatures, ie daily heat gain delivered by the solar panel.
A gain of 20 Ceclius = 22.5 MJoules of energy.
The flat yellow line shows approx. cylinder element power usage without solar heating
I have continued to monitor performance using my datalogger, but I am just publishing the first full years data above. I expect performance in the subsequent years to be similar.
© In the Light, 13 May, 2011 , Disclaimer, Son of Suckerfish drop-downs from HTML dog