Experimental Study on the Performance of RT 25 to be Used as Ambient Energy Storage

AbstractThe proposed experimental work intends to analyse the thermal performance of a TES unit incorporated into a ventilation system under different working conditions. The influences of the air inlet temperature and velocity on the air outlet temperature and heat transfer rate were investigated The air inlet temperature used for the solidification of RT25 were 10°C, 12°C and 14°C and for the melting 34°C, 36°C and 38°C. The selected air inlet velocities were the same for the melting and solidification process: 0.5 m/s, 1.4 m/s and 2.5 m/s. The results suggest that an increase of the air inlet velocity reduces linearly the temperature difference between the air inlet and outlet for the solidification process of the RT25. Contrary, for the melting of the RT25, increasing the air inlet velocity does not reduce the temperature difference linearly, increasing the air inlet temperature furthermore from 36°C to 38°C did not affect the melting time. The air inlet temperature plays a significant role on the melting process, reducing linearly the air inlet and outlet temperature difference and the heat transfer rate, however does not influence the solidification process, similar air inlet and outlet temperature difference and the heat transfer rate were obtained for all condition.Thus, air inlet velocity and air inlet temperature have to be carefully balanced to optimize the whole running cycle of both melting and solidification processes

A Portuguese study on building renovation towards a nearly zero energy building (nZEB)

The social and environmental urgency of large-scale integrated retrofitting of the European residential building stock is widely acknowledged and supported by all Member States. However, the European building sector is currently still not able to offer an integral solution for deep renovation toward nearly Zero Energy Building (nZEB) for reasonable costs. MORE-CONNECT project aims to tackle this issue by developing cost optimal solutions to renovate buildings towards nZEB. In this project, the optimal solutions include the development of prefabricated, multifunctional renovation elements for the total building envelope (façade and roof) and installation/building services. This paper presents the first stage of the project, namely the analysis and comparison of three scenarios following the current national requirements in Portugal i) 80% reduction of the current primary energy consumption of the building, ii) cost optimal solution (nZEB) and iii) net zero energy (NZEB). The optimization of the building envelope will be the main driver for the three scenarios as well as the inclusion of renewable energy strategies. Overall, results suggest that it is possible to achieve cost-effective solutions for the renovation of Portuguese residential buildings. Moreover, the cost-optimal solution (scenario ii) matches approximately with the 80% reduction of energy scenario (scenario i).MORE-CONNECT is funded by the European Commission within the framework of the Horizon 2020 progra

Soluções de reabilitação de fachadas como contributo para assegurar os nZEB – um caso de estudo em Portugal

O sector dos edifícios é o maior consumidor de energia final na União Europeia. Isto deve-se ao facto de a maioria dos edifícios apresentar um fraco desempenho térmico da envolvente. O parque edificado da União Europeia é, na sua maioria, anterior a 1960, de uma época pautada pela ausência de regulamentos de eficiência energética e em que as questões relacionadas com o consumo de energia e as emissões de carbono não assumiam a premência que apresentam na atualidade. A reabilitação energética apresenta-se hoje como a ferramenta mais eficaz para fazer face ao desafio de melhorar o desempenho energético do parque edificado existente. Servirá não só para atingir as ambiciosas metas de redução de consumo energético até 2020 e 2050 como para garantir um ambiente construído de qualidade e sustentável. Com taxas de construção nova muito reduzidas, a reabilitação é uma solução alternativa que apresenta inúmeras vantagens e é cada vez mais reconhecida como o futuro no sector dos edifícios. A revisão da diretiva Europeia relativa ao desempenho energético dos edifícios introduziu o conceito de edifício de necessidades quase nulas de energia (nZEB) e a obrigatoriedade de todos os edifícios novos após 2020 serem nZEB. Da mesma forma, também o conceito deverá ser aplicado aos edifícios existentes, adaptando-os para nZEB, através da reabilitação energética. Estes edifícios apresentam um desempenho energético muito elevado, sendo que as reduzidas necessidades energéticas que apresentam devem ser asseguradas em grande parte por energia proveniente de fontes renováveis, produzida no local ou nas proximidades. Complementarmente, as soluções nZEB devem obedecer a critérios de racionalidade económica. Para tal, a Comissão Europeia desenvolveu um quadro metodológico aplicável a todos os Estados Membros, que permite a identificação e análise dos níveis ótimos de rentabilidade do desempenho energético dos edifícios. O presente estudo enquadra-se no âmbito do projeto Europeu More-Connect que se centra no desenvolvimento de elementos modulares prefabricados de reabilitação energética para atingir edifícios nZEB. É apresentada a análise preliminar de três cenários de reabilitação energética aplicados ao caso de estudo em Portugal e o desenvolvimento inicial de um elemento prefabricado de reabilitação de fachada.Projeto Europeu H2020-EE-2014-2015/H2020-EE-2014-1-PPP, grant agreement no 633477, “MORE-CONNECT – Development and advanced prefabrication of innovative, multifunctional building envelope elements for Modular Retrofitting and smart CONNECTions

Life cycle energy of vehicles on lightweighting and alternative powertrain strategies—A review

To improve vehicles environmental performance, different strategies have been explored namely to reduce the use stage energy. In order to avoid problem shifting, a life cycle perspective should be used to compare alternative solutions. This paper aims to compare existing studies focused on life cycle energy (LCE) of vehicles to analyze the impacts and benefits regarding two trending improvement strategies: lightweight materials and alternative powertrain selection. A Literature review was performed to systematize quantitatively the LCE results of different studies (e.g. presented among figures, tables, and literature text). The LCE results were compiled and normalized for the same driving distance, 200 000 km, per life cycle stage. Moreover, the study discusses research findings on the application of the two strategies to improve overall vehicles’ LCE. As lightweight materials have generally higher embodied energy, the material selection is highly influenced by end-of-life scenarios. It was observed that carbon/glass fiber composites generally have the highest embodied energy, being a preferable option for vehicles that last longer driving distances. Innovative powertrains sourced by renewable energy sources, electric mixes, can significantly reduce vehicles’ LCE use stage, counteracting the benefit of lightweight design. Thus, the benefit of both strategies should be studied together.This research was funded by European Union’s Horizon 2020 research and innovation programme under grant agreement “No. 810764”, and by the regional European and development fund through the grant POCI-01- 0247-FEDER-046095. This work was supported by project Base Funding – UIDB/04730/2020 of the Center for Innovation in Engineering and Industrial Technology – CIETI; LA/P/0045/2020 (ALiCE) and UIDB/00511/2020 - UIDP/00511/2020 (LEPABE) funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Testing of a low-cost dry cell prototype for oxyhydrogen production

This work aims to study the production of oxyhydrogen gas by a small low-cost prototype consisting of six dry cells. Firstly, a molecular composition study of the gas was carried out, presenting concentrations of 67% H2 and 28% O2. The deviation from the stoichiometric yield is discussed to be caused by water vapor production and/or oxygen dissolution in the liquid phase. Secondly, an efficiency study was done, considering the ratio between the reversible voltage of an electrolytic cell and the voltage applied to the dry cell by an external power source. Different working conditions (electrolyte concentration, 3% (w/w) of KHO and 20% (w/w) of KHO) have been tested to analyze their effect on the efficiency of the system. The results show that a lower electrolyte concentration increases the applied cell voltage, and so the necessary power input for gas production to occur, resulting in lower cell efficiency. Overall, the efficiencies are below 69.8 +/- 0.6% for the studied electrolyte concentrations and approach approximately the same value around 50% for higher powers

An innovative window heat recovery (WHR) system with heat pipe technology: Analytical, CFD, experimental analysis and building retrofit performance

This paper addresses the numerical and experimental performance analysis of a windows heat recovery system made of heat pipes. For modelling, the heat pipe is considered as a pseudo solid material with high value of effective thermal conductivity. An experimental investigation using a window heat recovery prototype was carried out to predict the value of effective thermal conductivity of the heat pipes and to validate the numerical model. After validation, a parametric analysis was conducted to investigate the performance of the recovery system for different working conditions (mass flow rate and temperature difference between exhausted and supplied air). Based on the performance obtained in the parametric analysis, energy performance in building and the impact on velocity and pressure distributions are also evaluated with the support of CFD analysis. It is found that the effectiveness of window heat recovery made of heat pipes depends on ventilation rate and temperature difference between exhausted and supplied air. Increasing ventilation rates and temperature differences decrease the effectiveness. For ventilation rate between 10–60 m 3/h and temperature difference 10–30 °C, effectiveness between 65%–95% and pressure drop 4–80 Pa are obtained. For performance in building, the power consumption can be reduced between 3%–24% and the thermal comfort increased