• Energy Research

The deployment of Positive Energy Districts (PEDs) is currently facing a set of diverse and complex challenges, mainly arising from their novelty and the lack of practical experience. In that sense, there is a clear need for translating concepts and strategies into instruments that support the design, planning and operation of PEDs. The present research aims to address this gap by introducing a methodology to assess the potential of an existing district to be converted into a PED in the specific context of Mediterranean cities, which, in addition to presenting similar climatic characteristics, share a common urban pattern and culture. The first step consists of analyzing the initial state of the district through the study of its bioclimatic and urban characteristics and estimation of its energy demand. Then, the second step allows for selecting and designing a set of passive and active strategies for the district. Finally, the technical feasibility of the scenario is evaluated by calculating its annual energy balance. The methodology is applied to a district of Alcorcón, Spain. Results show that the selected district could achieve an annual surplus of 4 GWh and, therefore, has the technical potential to be converted into a PED.

In this paper, a methodology for the integral energy performance characterization (thermal, daylighting and electrical behavior) of semi-transparent photovoltaic modules (STPV) under real operation conditions is presented. An outdoor testing facility to analyze simultaneously thermal, luminous and electrical performance of the devices has been designed, constructed and validated. The system, composed of three independent measurement subsystems, has been operated in Madrid with four prototypes of a-Si STPV modules, each one corresponding to a specific degree of transparency. The extensive experimental campaign, continued for a whole year rotating the modules under test, has validated the reliability of the testing facility under varying environmental conditions. The thermal analyses show that both the solar protection and insulating properties of the laminated prototypes are lower than those achieved by a reference glazing whose characteristics are in accordance with the Spanish Technical Building Code. Daylighting analysis shows that STPV elements have an important lighting energy saving potential that could be exploited through their integration with strategies focused to reduce illuminance values in sunny conditions. Finally, the electrical tests show that the degree of transparency is not the most determining factor that affects the conversion efficiency.

Whereas the modern architecture trends to an extensive use of glazing elements, buildings are increasingly required to minimize the external energy demand, cutting down the energy needed and covering the residual demand using local energy generation solutions. In this context, the integration of optimized Semi- Transparent Photovoltaic (STPV) elements seems to present a promising energy saving potential, leading to significant reductions of the heating, cooling and lighting loads while the on-site electricity generation is supplied. In mild climate areas, building glazings are required to perform as solar control systems with a low solar factor in order to avoid overheating. However, g-value is frequently unavailable in the data sheet of the STPV elements, making it difficult to design the optimal building solution. In the present work, an indoor testing facility to analyze the solar factor of STPV elements has been further developed and validated. The operating principles of the calorimetric system as well as the experimental data obtained in the validation stage are presented. Results show that the system accuracy and sensitivity are fully adequate to perform detailed analyses of the solar factor of STPV glazings. Furthermore, g-value variations with the transparency degree have been analyzed over different electrical operating points. 31st European Photovoltaic Solar Energy Conference and Exhibition; 2633-2638

Experimental characterization and implementation of an integrated autoregressive model to predict the thermal performance of vegetal façades

Nowadays, there is an increasing interest in more efficient building materials and new technologies to accomplish the objectives defined by energy policies. The combination of energy efficient building designs and integration of renewable energies makes the use of thermal energy storage (TES) necessary. Within this context, the improvement of building envelopes by the use of phase change materials (PCM) has been widely studied. The PCM selection should fulfil the requirements of the specific application. In this study, a benchmarking of PCM available in the market was performed to undertake a material selection for a specific building application. The incorporation of PCM into a radiant wall technology present several requirements with especial interest on long-term thermal stability. A complete laboratory-scale characterization has been carried out considering the following properties: temperature of phase change, specific heat capacity, thermal conductivity, and stability. Financiado por el proyecto RTC-2015-3583-5 (INPHASE) del Ministerio de Economía y Competitividad, dentro del Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, en el marco del Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016, y ha sido cofinanciado con FONDOS FEDER, con el objetivo de promover el desarrollo tecnológico, la innovación y una investigación de calidad. The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER) and ENE2015-64117-C5-2-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537 and 2017 SGR 188). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. Camila Barreneche would like to thank ACCIO for her Grant TecnioSpring Plus TECSPR17-1-0071. Aran Solé would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva FJCI-2015-25741.

The use of vegetal systems in facades affects the reduction of the buildings' energy demand, the attenuation of the urban heat island (UHI) and the filtration of pollutants present in the air. Even so, up to now the knowledge about the effect of this type of systems on the thermal performance of insulated facades is limited. This article presents the results of an experimental study carried out in a vegetal facade located in a continental Mediterranean climate zone. The objective is to study the effect of a vegetal finishing, formed by plants and substrate, on the thermal-energy performance of an insulated facade under summer conditions. To this effect, the thermal data obtained from two full-scale experimental mock-ups of the same dimensions and composition of the enclosure and only different in the south facade's enclosure where one incorporates a vegetation layer are compared and analysed. The results show that, in spite of the high thermal resistance of the enclosure, the effect of the vegetation is very positive, particularly in the warmer hours of the day. Therefore, vegetal facades can be used as a passive cooling strategy, reducing the consumption of energy for refrigeration and improving the comfort conditions of the users. (C) 2014 Elsevier Ltd. All rights reserved.