Building technologies
Final Report Abstract
In the context of the Research Unit UCaHS related to heat stress in mid-latitude cities, Research Module (RM) 4.3 "Building technologies" was responsible for the analysis of the feedback effects of modern air conditioning systems. Air-conditioning-systems are one possible means in adaptation to elevated heat-related risks. These systems typically are employed whenever the heat-stress risk needs to be decreased, as they impact on the hazard, namely on the indoor climate. A the beginning of the study it was found that the handling of risk and hazard in typical epidemiological studies does not include the building structure and its thermal characteristics, or air-conditioning equipment, despite the fact that humans spend most of their time inside of buildings. Obviously, these effects have an enormous, if not dominant, impact on the heat related risk. Therefore, a risk concept that includes the indoor climate was developed. This risk concept has shown that fit parameters in epidemiological studies, e.g., threshold temperatures or vulnerabilities, are influenced by the thermal properties of the prevailing building structure. The effects of air-conditioning technologies on risk now can be re-analyzed for past data and used for more reliable projections. The findings are useful to also analyze existing epidemiological studies and separate the effects of the building structure. As a further advantage the risk concept also allows for better analyzing countermeasures to the urban heat island effect which are addressing the outdoor environment, e.g. greening, shading, or cool surfaces. Simplified building models were analyzed to calculate indoor temperatures of a building with sufficient accuracy. These models can be applied as an interface model between outdoor and indoor climate in the risk concept. The project furthermore investigated the feedback of different cooling technologies on the regional climate. Surprisingly, regenerative technologies are not always the best option with respect to reduction of the outdoor hazard as they might have a larger net energy input into the local climate compared to efficient central fossil-driven technologies. This effect is influenced by the efficiency of the energy system, its localization, and the albedo of the surfaces on which the solar electric or solar thermal collectors are installed. Centralized regenerative systems and cooling networks are most advantageous and should be promoted especially in urban regions. The performance of the air-conditioning systems is dependent both on indoor and outdoor conditions. Reliable models of the systems are therefore needed to estimate the efficiency with respect to risk reduction. In the project several regression models to describe absorption chillers and heat pumps were compared with respect to the statistical contribution of the number of model parameters. It was shown that simple grey box models statistically perform better than black box models with much more parameters. Feedback effects in an open liquid desiccant system were analysed. The study has shown that these systems exhibit limitations which originate from mass flow ratios, heat exchanger quality, and internal recirculation of the solution. The overall research unit attracted media reporting. An important means to disseminate the work of this project to the public was the presentation at the open days of the Technische Universität Berlin (Lange Nacht der Wissenschaften).
Publications
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(2014). Limitations and feedback effects in liquid desiccant airconditioning systems. 31. March - 03. April 2014, International Sorption Heat Pump Conference, Washington, U.S.A.
Buchin, O. and Ziegler, F.
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(2014). Solar Cooling. [Special Issue]. International Journal of Refrigeration, vol. 39
Albers, J. and Auracher H. (Eds.)
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(2014). The role of building models in the evaluation of countermeasures to urban heat islands with a heat stress related risk concept. 13.-15. Oct 2014, International Conference on Countermeasures to Urban Heat Islands, Venice, Italy
Buchin, O., Jänicke, B., Meier, F., Scherer, D., Nytsch-Geusen, C., and Ziegler, F.
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(2015). Evaluation of the health-risk reduction potential of countermeasures to urban heat islands. Energy and Buildings, 114, 27-37
Buchin, O., Hoelscher, M. T., Meier, F., Nehls, T., and Ziegler, F.
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(2016). Review of regression models for absorption heat pumps. 13.-15. Oct 2016, Heat powered cycles conference, Nottingham, UK
Buchin, O., Albers, J., and Ziegler, F.
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(2016). The role of building models in the evaluation of heat-related risks. Natural Hazards and Earth System Sciences, 16(4), 963-976
Buchin, O., Jänicke, B., Meier, F., Scherer, D., and Ziegler, F.
