Meeting the hotwater demand through the use of solar collectors
This workbook shows the calculations involved in the determination of the most suitable solar collector system for installation to produce the optimum saving in CO2
when compared to the level of CO2 which would be emiited if natural gas was used
The demand from hot water at the Rottenrow site is estimated to be 21987 KWhr/annum
The associated release of CO2 from use of natural gas is 0.13 Kg/KWhr
Based on a efficient modern boiler unit using natural gas as the fuel which operates
at 90 % efficiency the real consumption in KWhr necessary to supply the heating
demand is found by dividing the heating demand by 0.9. This gives a real heating demand of 24430 KWhr/annum
Thus the associated release of CO2 from the use of natural gas to supply the fuel hot water demand is 3175.9 Kg CO2 / annum
type of solar number of solar natural gas saving area of collector total area of collector CO2 saving
collector collectors per annum m2 m2 per annum
deficit excess
2 13208.1 601.193 11222.12222 3.041 6.082 1458.875889
MSC-32 solar collector 4 11441.7 1987.45 12988.52222 3.041 12.164 1688.507889
with perfectly insulated 6 10833.1 3589.28 13597.12222 3.041 18.246 1767.625889
tank of volume 0.03m2 8 10607.4 5030.81 13822.82222 3.041 24.328 1796.966889
10 10528.2 6274.08 13902.02222 3.041 30.41 1807.262889
12 10550.5 7351.94 13879.72222 3.041 36.492 1804.363889
14 10614.4 8326.04 13815.82222 3.041 42.574 1796.056889
16 10731 9243.7 13699.22222 3.041 48.656 1780.898889
18 10894.8 10139.5 13535.42222 3.041 54.738 1759.604889
It is obvious from the above graph that the amount of CO2 saved does not change significantly after the installation of 8 solar collectors, thus area area of 24.328 m2 and a CO2 saving of 1796.97 is resultant
Type of number of solar natural gas saving area of collector total area of collector CO2 saving total area of collector % of CO2 saving
Solar collector collectors per annum m2 m2 per annum per annum
deficit excess
msc 32 2 12987.1 697.631 11443.12222 3.041 6.082 1487.605889 6.082 0.46840025
2 perfectly 4 11018.1 2618.2 13412.12222 3.041 12.164 1743.575889 12.164 0.54899714
insulated storage 6 10361.2 5165.79 14069.02222 3.041 18.246 1828.972889 18.246 0.57588597
tanks 8 10081.6 7522.6 14348.62222 3.041 24.328 1865.320889 24.328 0.58733081
10 9944.18 9591.48 14486.04222 3.041 30.41 1883.185489 30.41 0.59295581
12 9855.72 11419.8 14574.50222 3.041 36.492 1894.685289 36.492 0.59657674
14 9825.72 13038.8 14604.50222 3.041 42.574 1898.585289 42.574 0.59780472
16 9849.14 14500.6 14581.08222 3.041 48.656 1895.540689 48.656 0.59684607
18 9898.18 15824.8 14532.04222 3.041 54.738 1889.165489 54.738 0.59483872
It can be seen that the optimal amount of installed solar collectors is approx 8 solar collectors with an area of 24.32m2 and a CO2 saving of 1865.32 KG per year
Type of number of solar natural gas saving area of collector total area of collector CO2 saving total area of collector % of CO2 saving
Solar collector collectors per annum m2 m2 per annum per annum
deficit excess
msc 32 2 12833.9 847.929 11596.32222 3.041 6.082 1507.521889 6.082 0.47467117
with storage tank of volume 4 10730.6 3290.4 13699.62222 3.041 12.164 1780.950889 12.164 0.56076535
preheat storage = 30m3 6 10016.9 6639.81 14413.32222 3.041 18.246 1873.731889 18.246 0.58997917
main storage = 150m3 8 9692.36 10415.8 14737.86222 3.041 24.328 1915.922089 24.328 0.60326354
10 9595.65 13949.5 14834.57222 3.041 30.41 1928.494389 30.41 0.60722216
12 9575.67 17299.4 14854.55222 3.041 36.492 1931.091789 36.492 0.60804
14 9612.23 20370.4 14817.99222 3.041 42.574 1926.338989 42.574 0.60654349
16 9692.97 23234 14737.25222 3.041 48.656 1915.842789 48.656 0.60323857
18 9831.12 25990.8 14599.10222 3.041 54.738 1897.883289 54.738 0.59758369
It can be seen that the optimal amount of installed solar collectors is approx 8 solar collectors with an area of 24.32m2 and a CO2 saving of 1915.92 KG per year
The following table gives an indication of the different CO2 savings associated with various volumes of storage associated with the solar collectors collector 
volume of storage CO2 saving per annum
0.03 1796.96
0.15 1865.32
150 1915.84
It can be seen that there is a massive jump in the  storage from 0.15 m3 to 150 m3 for a small increase in CO2 saving.
Thus the most optimal installtion of solar collectors is 8 solar collectors with an installed area of around 25.32 m2 and storage of 0.15m2 per solar collector