Demonstration of energy savings and indoor climate with sustainable adiabatic cooling using rainwater

The main objective of this project is to evaluate the opportunity for adiabatic cooling with rainwater in public buildings in terms of energy, cooling capacity and water consumption.

The results are only from the month of June 2019, and does not reflect several years. However, the June of 2019 seems to be quite warm compared to 2017 (and on par with 2016), which means the results are generic.

The cooling capacity of the adiabatic systems was 20-30 W/m2 and the system was capable of reducing the supply temperature by approx. 5°C.

The indoor temperature was acceptable in the range 22-25°C and would have been higher if no cooling was provided. The CO2-concentration (not disclosed in this report) was maximum 1000 ppm.

The water consumption in the warmest week of June was approx. 1 m3 per day. With the tank volume of 10 m3, and in the (rare) event of no precipitation for 14 days, the system may run for 10 school days before switching to tap water. The switch did not occur in the summer of 2019.

The energy costs are on par with conventional compressor cooling, but the calculation is sensitive to chosen input.
In terms of operation costs, two inexpensive filters in the rainwater supply should be changed every year. There are no required yearly inspection of the cooling installation as with compressor-driven cooling.

The risk of biofilm forming inside the unit has been in the focus of this project. The day water tank is disinfected by UV-light to minimize the risk of bacteria and vira and members of the project team visited an operating Menerga unit in Belgium using harvested rainwater, to investigate the risks. The Belgian unit was very clean inside, however, more references are necessary to address this concern.

To conclude, the system performs as expected and has had no operation disruption for the whole summer of 2019. This demonstrates that adiabatic cooling is a realistic alternative to compressor cooling for comfort in public buildings, especially in a climate adaptation context where surplus of rainwater can be converted into a sustainable cooling resource.