Absorption water washers revert the plants’ natural transpiration process. The researchers of the ZHAW’s Institute for Energy Systems and Fluid Engineering (IEFE) chose an innovative approach for their project: instead of heating or cooling the entire greenhouse, only the individual plant shelves are supplied with perfectly conditioned air. This is achieved with so-called absorption water washers, which revert the plants’ natural transpiration process. Over the course of several months, the researchers tested the new technology in a 600 sqm greenhouse at Meyer Orchideen AG. Over this trial period, they established that the energy consumption for the heating and cooling of greenhouses can be reduced by roughly half. Another advantage of this direct plant shelf air-conditioning is that it allows for precise and controlled climatic growth conditions independent of the weather. What is more, plants with varying climatic requirements can be cultivated side by side in one greenhouse.

Dovetailing with a European research project
The project unites economic value with a considerable reduction in energy consumption. At the same time, the project can be integrated in a cutting-edge storage network currently developed by ZHAW students in the framework of the EU’s H-DisNet research project. The latter is based on thermochemical networks, which, in contrast to thermal heat distribution networks, do not transport heat energy as such, but stored thermal/chemical potential in the shape of concentrated saline solutions, which are then used to produce useful heat our cooling wherever needed. Advantages compared to traditional heat distribution networks include higher energy density, lower investment costs and the potential for long-term, loss-free storage.

More than just a trophy
The Federal Office of Energy awards the annual “Watt d’Or” to particularly innovative energy projects. The ZHAW project won in the Energy Technologies Category. For Serena Danesi of the “Thermal Energy Systems” research group, the award is more than just a trophy: “This is a great recognition of our research work, but it also provides publicity for our project, which may prove useful for its further development with industry partners,” says the researcher. Her goal is to see the technology used by multiple greenhouse operators in Switzerland and expand to include additional applications such as building climate control or drying processes.