 Heat-transmission model based on the method of characteristics  Inclusion of the thermal capacity effect related to the turbulent boundary layer  Calculation 10 3 times faster than the finite-volume method at the same level of accuracy  Very good agreement with experimental data

Abstract. Ray-Tracing software tools have been widely used in the optical design of solar concentrating collectors. In spite of the ability of these tools to assess the geometrical and material aspects impacting the optical performance of concentrators, their use in combination with experimental measurements in the framework of collector testing procedures as not been implemented, to the date, in none of the current solar collector testing standards. In the latest revision of ISO9806 an effort was made to include linear focusing concentrating collectors but some practical and theoretical difficulties emerged. A Ray-Tracing analysis could provide important contributions to overcome these issues, complementing the experimental results obtained through thermal testing and allowing the achievement of more thorough testing outputs with lower experimental requirements. In order to evaluate different available software tools a comparison study was conducted. Taking as representative technologies for line-focus concentrators the Parabolic Trough Collector and the Linear Fresnel Reflector Collector, two exemplary cases with predefined conditions -geometry, sun model and material properties -were simulated with different software tools. This work was carried out within IEA/SHC Task 49 "Solar Heat Integration in Industrial Processes".

BC 6 ÿ ÿ 8ÿ Dÿ 1 2ÿ 1 ÿ 89ÿ 925 4 25ÿ 891 34 ÿ 4 84 ÿ 8ÿ =229ÿ 811234 25ÿ 1 ÿ 3= 184 9 ÿ 0ÿ 8ÿ 2 12ÿ 4 ÿ 14 2 ÿ E2ÿ 8 2ÿ 3 5 9ÿ 4 ÿ 28 ÿ 2 9ÿ 1 ÿ 4 2ÿ 891 34 ÿ 62ÿ 891 34 ÿ E ÿ 952 1325 4 9 ÿ 4 3224 4 9 ÿ 895ÿ 2 2Eÿ 1 ÿ 4 2ÿ 2 4 9ÿ 3 1 ÿ =21 2ÿ 4 ÿ ÿ 3= 25ÿ 9ÿ 4 ÿ 1 98 ÿ 1 ÿ 282 94 2ÿ 4 84 ÿ 5 9ÿ 4 2ÿ 3 514 9ÿ 3 12ÿ 2 ÿ 8ÿ =2ÿ 5 12 25ÿ E 1ÿ 1 5ÿ 81 1 214 ÿ 4 2ÿ 194 294 ÿ 895ÿ 8 28 ÿ 5 1 8 2 ÿ 4 84 ÿ 833 ÿ 4 ÿ 4 2ÿ / 98 ÿ 32 4 8 9

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District heating and cooling (DHC), when combined with waste or renewable energy sources, is an environmentally sound alternative to individual heating and cooling systems in buildings. In this work, the theoretical energy and economic performances of a DHC network complemented by compression heat pump and sewage heat exchanger are assessed through dynamic, year-round energy simulations. The proposed system comprises also a water storage and a PV plant. The study stems from the operational experience on a DHC network in Budapest, in which a new sewage heat recovery system is in place and provided the experimental base for assessing main operational parameters of the sewage heat exchanger, like effectiveness, parasitic energy consumption and impact of cleaning. The energy and economic potential is explored for a commercial district in Italy. It is found that the overall seasonal COP and EER are 3.10 and 3.64, while the seasonal COP and EER of the heat pump alone achieve 3.74 and 4.03, respectively. The economic feasibility is investigated by means of the levelized cost of heating and cooling (LCOHC). With an overall LCOHC between 79.1 and 89.9 €/MWh, the proposed system can be an attractive solution with respect to individual heat pumps.