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Exergetic assessment and contribution of solar energy systems to the energy performance of buildings

: Torio, H.; Schmidt, D.

Rode, C. ; Technical University of Denmark -DTU-, Lyngby:
8th Nordic Symposium on Building Physics in the Nordic Countries 2008. Proceedings. Vol.2 : Copenhagen, June 16-18, 2008
Lyngby, 2008 (DTU Byg Report 189)
ISBN: 978-87-7877-265-7
Nordic Symposium on Building Physics in the Nordic Countries <8, 2008, Kopenhagen>
Conference Paper
Fraunhofer IBP ()

Analyses of the exergy flows are common for the optimization of many thermodynamic systems since half of last century. Several international ongoing research projects try to extend this approach to the building sector, in order to develop more efficient buildings and supply structures by reducing the exergy losses in each step of the buildings´ energy supply chain.
Most of the energy in the building sector is used for heating and cooling purposes, i.e. to maintain constant room temperatures of around 20°C. Because of the low temperature level, the actual demand for exergy in space heating and cooling applications is low. In turn, solar radiation is undisputedly a high quality source, and thus high exergy losses arise when solar energy based technologies are used to cover a low exergy demand. Following, solar energy based technologies seem to be unsuitable to cover these demands from an exergy perspective. This evaluation schema however, is physically inconsistent with the one used for the assessment of any other energy sources.
In the paper a new assessment framework for technologies making a direct use of solar radiation is presented. Several solar-based technologies for heating and cooling of buildings are analysed using the proposed framework, and compared to the results obtained using the conventional assessment approach. From the results of the analysis the suitability of these technologies is shown, and first estimations on the contribution of these technologies for increasing the energy and exergy performance of buildings are derived.