Heat Harvest - Harvesting urban solar waste heat from buildings and surfaces to prevent summer overheating in the city
In order to avoid urban heat islands, greening measures as well as green and/or water surfaces are already being propagated and used in many places. However, the use of these solutions is not always sufficient, approvable or desirable, such as in old, historic or listed buildings. A simple, invisible and seasonal solution is the "harvesting" of solar urban excess heat from building surfaces, sidewalks, roads and squares through shallow absorber ducts, which are then used in borehole heat exchanger (BHE) fields for later use as heat source for the buildings. However, since temperatures in urban surfaces are sometimes very high (up to 50 ° C) and these cannot easily be introduced into BHE fields, common calculations and simulations are not sufficient to accurately predict the thermal behaviour of the subsoil in the densely built sensitive urban space with a lot of area competition.
Conventional calculation and simulation methods for the design of BHE fields are limited by the conditions that occur in strongly heated inner city areas, or simulations with higher temperatures are not easily possible. The underground temperatures of a city are already increased by building and use compared to the climatic conditions. The introduction of waste heat for seasonal storage and the integration of heat pumps is therefore very sensitive and must be based on reliable and accurate figures and calculations.
Therefore, some technical questions still need to be clarified before a planned pilot project. A pilot project is envisaged and supported by the Municipal Department for Energy Planning of the City of Vienna. The aim of the project Heat Harvest is to carry out comprehensive investigations of the thermal behavior of the subsurface in the case of solar thermal waste heat in a large-scale test facility on an open-air site and accompanying laboratory experiments as well as simulations under different conditions. In this way, the appropriate framework conditions for the harvest of solar waste heat in urban areas can be explored purposefully in order to later embed the approach into a larger cooperative research project.
Project Start
June 2019
Project Duration
18 months
Project Partner
AIT Austrian Institute of Technology GmbH
Funding tool
The project was carried out within the framework of "Stadt der Zukunft". "Stadt der Zukunft" is a research and technology program of the Federal Ministry for Climate Action, Environment, Energy, Mobility Innovation and Technology. It is managed on behalf of the BMK by the Austrian Research Promotion Agency (FFG) together with Austria Wirtschaftsservice Gesellschaft mbH (AWS) and the Austrian Society for Environment and Technology (ÖGUT).
