AirWaterHarvest

The “AirWaterHarvest” research project at the Faculties of Engineering and Construction at HTWK Leipzig is dedicated to analysing the conditions under which it is possible to harvest water self-sufficiently from the ambient air, for example for greening façades and roofs. It establishes the data basis for the self-sufficient irrigation of urban vegetation.

A green city helps to reduce the so-called heat island effect in large cities and thus counteracts urban warming. Drinking water or rainwater is generally used to irrigate green facades and roofs, a practice that is also recognised as the current state of research. However, particularly during periods of extreme weather conditions when water is scarce, the security of supply for both people and plants must still be guaranteed. As an alternative and retrofittable option, particularly in existing buildings, so-called atmospheric water harvesting is a viable solution. This makes it possible to actively collect condensation from the ambient air on cold surfaces – this type of water harvesting can be operated sustainably using renewable energy sources.

In addition to implementing such a water harvesting prototype, extensive building simulations and metrological studies are being carried out around the building envelope to assess the correct operating conditions for the atmospheric water harvester and the quantities of water that can be achieved.

The project aims to produce a planning tool that enables the virtual estimation of achievable water volumes and suitable greening options and plant species.

Background:

Extreme weather events caused by climate change are increasingly leading to prolonged periods of drought across Germany and Europe. The associated lack of rainfall ultimately leads to water shortages in urban regions and cities. Alongside this, there is a strong push to green balconies and façades in order to counteract, for example, urban heat island effects and insect decline (biodiversity). The artificial and, in some cases, energy-intensive irrigation of urban greenery using drinking water can exacerbate water shortages. The greening of existing buildings proves particularly problematic, as additional irrigation infrastructure must be retrofitted here (without utilising rainwater). The atmosphere contains 0.001% of the world’s fresh water [1, p. 4]. Therefore, utilising the water content of the ambient air to irrigate urban vegetation is an obvious consideration, for example by condensing water on the cold surface of a solar-powered Peltier element. The aim of the project is thus to investigate the fundamentals for implementing such self-sufficient water harvesting systems. In addition, boundary conditions for the deployment of the systems in existing buildings are to be defined as a resource-efficient and retrofittable approach. To this end, a database is to be created on the distribution of maximum humidity, temperature, pressure and solar radiation near the building envelope, depending on height, orientation (cardinal direction), the surrounding built environment, the time of day and the season. A wireless sensor network is used to record these and other parameters. Together with a mathematical model, this data forms the basis for calculating the water yield of an energy-self-sufficient water harvesting system. The simulation results for water yield and the generalisability of the measurement data with regard to different building types (residential complex, detached house, block of flats) are evaluated using a functional model of the water harvesting system.

Visit the project website