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Water-to-Water heat pump (WtWHP) is an efficient alternative to the current technologies used in Domestic Hot Water (DHW) production. However, this application is characterized by high secondary temperature lifts and irregular demands that define critically its design. In order to maximize the efficiency, transcritical cycles coupled to stratified storage tank has been the preferred solution. Nevertheless, recently subcritical cycles with a subcooling control system has been also considered also as a promising alternative because of the cost with the right desing the efficiencies could be in the range of transcritical system. The objective of this work is to compare the performance of both heat pump systems for DHW production in a heat recovery application where there is no restriction in the low temperature energy source availability. This situation could correspond to a source coming from sewage water or a system of low temperature district heating. The comparison has been made for the optimum configuration of both system which has implied the definition of the proper control strategy, proper sizing of the WtWHP and the tank and incorporation of a primary recovery heat exchanger in order to compare both systems in what is considered as the optimum working conditions. Results show that while both systems are able to operate with similar SCOPs, the CO2 system is more sensitive to water temperature lifts variations and temperature of the heat source than the propane WtWHP resulting in lower performances.

[EN] Straw presents several benefits when considering it for the construction sector in substitution of conventional materials. Not only has lower embodied energy and density, but also has valuable thermal properties for passive construction. Using rice-straw bales for construction could reduce the current waste-management problem for the city, saving costs for the material supply in the construction sector while providing better building and air-quality for the city. This research compiles different studies addressing the issue of using straw-bales for the construction, concluding with the main advantages of this material for professional building. The study also presents a monitored case study constructed in Villareal (Spain) using prefabricated modules of straw-bales. The study also comprises a detailed dynamic energy simulation with Energy Plus, and the detail of the calibration of the model., This work is framed inside the Chair of Urban Energy Transition of the city of València in the Universitat Politècnica de València and from the Institute for Energy Engineering. We thank the cooperative OKAMBUVA.