High temperature solar heating and cooling systems for different Mediterranean climates: Dynamic simulation and economic assessment

The paper presents a dynamic model of an innovative solar heating and cooling system (SHC) based on the coupling of Parabolic Trough Collectors (PTC) with a double-stage LiBr–H2O absorption chiller; auxiliary energy for both heating and cooling is supplied by a biomass-fired heater. The system layout also includes a number of additional components such as: cooling tower, pumps, heat exchangers, etc. The consumption of non-renewable energy resources is only due to the small amount of electrical energy consumed by some auxiliary device. A case study is presented, in which the SHC provides space heating and cooling and domestic hot water for a small university hall, all year long. Both the SHC system and the building were dynamically simulated in TRNSYS. In order to evaluate the performance of the investigated system in various climatic conditions, the analyses were performed for seven Mediterranean cities in Italy, Spain, Egypt, France, Greece and Turkey. The analysis was also performed for a similar SHC in which the biomass heater was replaced by a gas-fired heater, in order to evaluate the influence of biomass to the overall system economic and energetic performance. In addition, a parametric analysis was performed in order to evaluate the sensitivity of the results, when varying some of the main design and operating parameters, such as: collector field area, tank volume and set-point temperatures. The results showed that the SHC system layout investigated can be competitive for the majority of the locations analysed, although the economic profitability is higher for the hottest climates.

► In the high temperature SHC system the auxiliary heat is provided by biomass.
► The energetic performance of the system is excellent during the summer.
► In the winter the system suffers of the low beam radiation incident on the PTC.
► The Simple Pay Back Period is encouraging, particularly in case of public funding.
► An increase of the solar field area improves the energetic and economic parameters.