Low Energy Data Centre
Solar Thermal Collector
To improve the energy efficiency of our data centre and doing some substantial energy saving, we made the choice of settling solar panel collector on the site.
We have 5 person from midnight to 8a.m., then 50 from 8 a.m. to 4p.m. and again 5 from 4p.m. to midnight.
It’s an average of 20 people per day and we need 50 litres of hot water per person per day.[1]
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1000L/day of hot water
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Water T° of 40°C. Sometimes heated to 60°C to delete legionella
We can’t kill the legionella with the Solar Thermal Collector, we will use a biomass boiler to do it. As recommended, a heating to 60°C during 45 seconds is enough to prevent any risk of legionellae.
We have to design a total storage volume of 1200L because the recommendation are a total volume of 120% of the daily consumption in hot water.
We chose a forced circulation with separate heat exchanger because it is compulsory for large collective installations and it is the method which has the best efficiency.
For the following simulations of the energy gains from the solar panel collector, we are considering are walls with a U value of 0,15W/m²K according to PassivHaus standard.
We chose the following type of solar panel collector as shown below:
Figure 1 : Bosch Thermotechnologies SAS Solar 7000 TV VK-140
The geometrical specifications of the panels are as follow:
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Collector Slant 66°/horizon ( Latitude+10°)
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Orientation 0°/south (best possible)
Our model has an aperture are of the collector of 1,28m².
With 150 collectors we have a surface of 192 m² and these results:
Table 1 : Calculation spreadsheet
We have a solar fraction of 96.1%, the biomass boiler will only be used to heat the water to 60°C sometimes and the remaining 3.9%.
We still have 47 kWh to heat with the biomass boiler. Cycle of 45s are enough to kill the legionella. Once a week is enough so we need 52*45s=0,65h of functioning of biomass boiler in the year. This additional heating correspond to an energy consumption of additional 43kWh/year.
Need a power of 125 kW installation boiler. We chose the 195kW 195 XXL from KSM Multifuel Boilers.
Total electrical consumption: 91kWh/year.
If we used the boiler only without Solar panels collectors the total annual load is 12077kWh.
In conclusion, we managed to use the solar energy to supply 95.74% for hot water in the offices.
