Potential fuel saving in a powertrain derived from the recovery of the main energy losses for a long haul European mission

[EN] The reduction of automotive fuel consumption and emissions remains one of the main challenges. This paper presents the potential fuel saving in a CNG-powertrain derived from the recovery of the main energy losses. The analysis includes the kinetic energy recovery by a belt starter generator (BSG), the exhaust gas waste heat recuperation by using in a cascade approach, a thermoelectric generator (TEG) and a turbo-generator (TBG)- and the electrification of the main auxiliaries. An additional 48 V board net as well as the addition of a storage system are also included in the study. To support on the design phase of the project and in the operation strategy, a dynamic model in Matlab/Simulink (R) has been used. The model includes all the new components/major changes required in the vehicle- experimentally validated-. It has been used on backward simulations for the ACEA long haul mission in order to maximize the vehicle's efficiency. Estimations at rating point (600 Nm and 1200 rpm) result in an electric production up to 4 kW h and a fuel saving of 7.5%. The most convenient technologies in the ACEA cycle turns out to be the KERs followed by the TBG.This work has been developed in the frame of the project of the European Seventh Union Framework Program by the project High efficiency energy conversion for future heavy duty transport High efficiency energy conversion for future heavy duty transport GASTone grant agreement 605456. The authors are grateful for the given support.Hervas-Blasco, E.; Navarro-Peris, E.; De Rosa, M.; Corberán, JM. (2017). Potential fuel saving in a powertrain derived from the recovery of the main energy losses for a long haul European mission. Energy Conversion and Management. 150:485-499. https://doi.org/10.1016/j.enconman.2017.08.01848549915

Energy optimization of a thermal storage tank for Domestic Hot Water production

[EN] According to the European Commission, the residential sector is responsible at this moment of the 40 % of the energy consumption and 36 % of the associated CO2 emissions in Europe. Regarding the water heating consumption, it is currently responsible for 14.5 % energy consumption of the average European dwelling. This percentage is expected to increase drastically within the concept of Near Zero Energy Building (NZEB) since the associated heating consumption percentage will be decreased largely. In this way, the energy consumption associated for water heating should be reduced, and it only can be done by using highly energy efficient technologies, such as heat pump (HP), and decreasing the energy losses associated to the facilities. In the frame of the European Project NEXTHPG of the 7th framework program, a new prototype of heat pump booster for the production of domestic hot water was developed. The developed prototype uses an innovative subcooling control system, which allows increasing the COP of the system in more than 30% compared to conventional subcritical heat pump systems. Nevertheless, in a real installation apart from the heat pump there are other factors contributing to the final energy consumption of the whole system like system configuration, control algorithm, tank size and the like. Therefore, an estimation of the final energy consumption of the system could be significantly different from the obtained taking into account only the pump performance. The present work is focused on the development of a model in order to optimize the design of the whole system using the prototype of the NEXTHPG project in order to satisfy the domestic hot water demand of a building for 20 people. The integrated system model will include the heat pump, the water tank, a heat exchanger in order to recover part of the waste heat (such as the heat coming from the sewage water in the domestic sector or from condensing loops in tertiary sector) and a random generator of domestic hot water demand profile. From the results of this work, the proper sizing of the heat pump and the water tank, as well as the control algorithm, are obtained and the potential annual energy consumption of this type of system is estimated.Part of the work presented was carried by Estefanía Hervás Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500 x 074478XV0. The authors would like also to acknowledge the Spanish MINISTERIO DE ECONOMIA Y COMPETITIVIDAD¿, thorugh the project. MAXIMIZACION DE LA EFICIENCIA Y MINIMIZACION DEL IMPACTO AMBIENTAL DE BOMBAS DE CALOR PARA LA DESCARBONIZACION DE LA CALEFACCION/ACS EN LOS EDIFICIOS DE CONSUMO CASI NULO with the reference ENE2017-83665-C2-1-P for the given support and REDUCCIÓN DE LAS EMISIONES DE CO2 EN LA PRODUCCIÓN DE AGUA CALIENTE A ALTA TEMPERATURA A PARTIR DE LA RECUPERACIÓN DE CALOR RESIDUAL MEDIANTE EL USO DE UNA BOMBA DE CALOR with the reference SP20180039.Masip, X.; Álvarez-Piñeiro, L.; Hervas-Blasco, E.; Navarro-Peris, E.; Corberán, JM. (2019). Energy optimization of a thermal storage tank for Domestic Hot Water production. Universidad de Castilla-La Mancha José Antonio Almendros Ibáñez. 167-175. http://hdl.handle.net/10251/180696S16717

Study of different subcooling control strategies in order to enhance the performance of a heat pump

[EN] The performance of vapor-compression systems working with subcritical refrigerants varies with the degree of subcooling. There is an optimal subcooling that maximizes efficiency. However, it depends on the operating conditions and the control of the system needs to be adapted. Most of the works available in literature are able to operate in optimal conditions only at the design point or if a system is designed to be able to adapt its subcooling, only complex control algorithms that usually are difficult to set and time-costly, are used. This work focuses on the study of the main variables influencing the optimal subcooling and analyzes two different control methodologies from the theoretical point of view. Based on the theoretical study a final control strategy is selected and tested experimentally. The reliability, stability and robustness of the selected strategy are experimentally demonstrated for a wide set of operating conditions. (c) 2018 Elsevier Ltd and IIR. All rights reserved.Part of the work presented was carried by Estefania Hervas Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500 x 074478XV0. The authors would like also to acknowledge the Spanish 'MINISTERIO DE ECONOMIA Y COMPETITIVIDAD', through the project. "MAXIMIZACION DE LA EFICIENCIA Y MINIMIZACION DEL IMPACTO AMBIENTAL DE BOMBAS DE CALOR PARA LA DESCARBONIZACION DE LA CALEFACCION/ACS EN LOS EDIFICIOS DECONSUMO CASI NULO" with the reference ENE2017-83665-C2-1-P for the given support.Hervas-Blasco, E.; Pitarch, M.; Navarro-Peris, E.; Corberán, JM. (2018). Study of different subcooling control strategies in order to enhance the performance of a heat pump. International Journal of Refrigeration. 88:324-336. https://doi.org/10.1016/j.ijrefrig.2018.02.003S3243368

Evaluation of optimal subcooling in subcritical heat pump systems

[EN] The performance of a transcritical cycle is highly dependent on the rejection pressure. The optimal rejection pressure depends mainly on the inlet and outlet temperatures at the heat sink (secondary fluid). For the subcritical cycles, recent studies have demonstrated that the performance of these systems depends significantly on the degree of subcooling and its optimal value varies depending on the application. This paper presents a general methodology to calculate the optimal subcooling depending on the boundary conditions. The refrigerants R290, R134a, R1234yf and R32 are analyzed. Exergy analysis is used in order to see the subcooling effect at condenser and expansion valve independently. The optimal subcooling strongly depends on the temperature lift at the secondary fluid, and it is found when two pinch points are given in the condenser, one at the condenser outlet and another one inside the condenser (at the refrigerant dew point).Part of the results of this study were developed in the mainframe of the FP7 European project "Next Generation of Heat Pumps working with Natural fluids" (NxtHPG). Part of the work presented was carried by Miguel Pitarch-Mocholi with the financial support of the PhD scholarship from the Universitat Politecnica de Valencia. The authors would like to acknowledge the Spanish "MINISTERIO DE ECONOMIA Y COMPETITIVIDAD", through the project ref-ENE2014-53311-C2-1-P-AR "Aprovechamiento del calor residual a baja temperatura mediante bombas de calor para la produccion de agua caliente" for the given support.Pitarch, M.; Hervas-Blasco, E.; Navarro-Peris, E.; Gonzálvez-Maciá, J.; Corberán, JM. (2017). Evaluation of optimal subcooling in subcritical heat pump systems. International Journal of Refrigeration. 78:18-31. https://doi.org/10.1016/j.ijrefrig.2017.03.015S18317

Heat Pump control comparison of a conventional superheat system over a subcooling control system for Domestic Hot Water production

[EN] The water heating consumption of the average European dwelling accounts at this moment for 14.5 %, according to the European Commission, whereas heating and cooling percentage account for 64.7 %. The European Union, with the introduction of the Nearly Zero Energy Buildings (NZEB) concept, intends to decrease in a great amount the total energy consumption of the residential sector acting over the percentage associated to heating. This will have an effect on the water heating consumption, increasing its consumption percentage. Therefore, in order to reduce the residential sector consumption and more concretely the percentage associated to water heating consumption, it will be key the use of highly energy efficient technologies since it is not possible to reduce the water heating energy consumption by acting on the demand without the risk of not satisfying the user comfort. In that sense, heat pumps are a technology of increasing interest. It is considered as renewable when its SPF is above 2.5, its production does not depend on external factors (as sunlight) and will play a key role in the cities of the future since it has the capability of acting as a booster from heat distribution networks. At this moment, the heat pumps available in the market for domestic hot water production using subcritical cycles are cost-effective but its design does not differ significantly from the used for heating applications. In the frame of the European project NEXTHPG, a heat pump system specifically designed for domestic hot water production with a variable subcooling control was developed. In this work, a comparison between the energy consumption at the system level of this prototype with a commercial water-to-water heat pump for domestic hot water production is performed. The results show a big difference in terms of energy efficiency between both cases. The variable subcooling case results in a 26.68 % positive energy efficiency difference regarding the conventional case when compared in their maximum efficiency point. The sizing of the heat pump-storage tank duality plays an important role since it could lead to an energy efficiency loss of almost 17 %. These results show clearly the advantages of the innovative heat pump model in front of the conventional heat pumps used for domestic hot water production.Part of the work presented was carried by Estefanía Hervás Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500 x 074478XV0. The authors would like also to acknowledge the Spanish MINISTERIO DE ECONOMIA Y COMPETITIVIDAD, through the project. MAXIMIZACION DE LA EFICIENCIA Y MINIMIZACION DEL IMPACTO AMBIENTAL DE BOMBAS DE CALOR PARA LA DESCARBONIZACION DE LA CALEFACCION/ACS EN LOS EDIFICIOS DE CONSUMO CASI NULO with the reference ENE2017-83665-C2-1-P for the given support and REDUCCIÓN DE LAS EMISIONES DE CO2 EN LA PRODUCCIÓN DE AGUA CALIENTE A ALTA TEMPERATURA A PARTIR DE LA RECUPERACIÓN DE CALOR RESIDUAL MEDIANTE EL USO DE UNA BOMBA DE CALOR with the reference SP20180039.Masip, X.; Álvarez-Piñeiro, L.; Hervas-Blasco, E.; Navarro-Peris, E.; Corberán, JM. (2019). Heat Pump control comparison of a conventional superheat system over a subcooling control system for Domestic Hot Water production. Universidad de Castilla-La Mancha José Antonio Almendros Ibáñez. 158-166. http://hdl.handle.net/10251/180676S15816

Conception d une pompe à chaleur eau-eau optimisée pour la récupération de chaleur perdue à basse température basée sur la régulation du sous-refroidissement

[EN] Traditional heat pumps designs have been optimized for heating applications based on small secondary temperature lifts (around 5K); however, in applications with other characteristic temperature lifts, different design criteria could be required. For instance, transcritical cycles have demonstrated to have a high efficiency for domestic hot water production with high water temperature lifts. This work presents the experimental results of a new water-to-water heat pump composed by the basic heat pump components (condenser, compressor, evaporator, expansion valve and liquid reliever) able to adapt its performance depending on the required water temperature lift. Domestic hot water production from grey water waste heat recovery has been chosen as experimental application to test this heat pump. Results show COP values up to 5.5 at the design condition (20-15 degrees C at the inlet-outlet of the evaporator and 10-60 degrees C at the inlet-outlet of the condenser) and an optimal degree of subcooling of 47 K. (C) 2019 Elsevier Ltd and IIR. All rights reserved.Part of the results of this study were developed in the mainframe of the FP7 European project 'Next Generation of Heat Pumps working with Natural fluids' (NxtHPG). Part of the work presented was carried out by Estefania Hervas Blasco with the financial support of a PhD scholarship from the Spanish government SFPI1500 x 074478XV0. The authors would like also to acknowledge the Spanish 'MINISTERIO DE ECONOMIA Y COMPETITIVIDAD', through the project "MAXIMIZACION DE LA EFICIENCIA Y MINIMIZACION DEL IMPACTO AMBIENTAL DE BOMBAS DE CALOR PARA LA DESCARBONIZACION DE LA CALEFACCION/ACS EN LOS EDIFICIOS DE CONSUMO CASI NULO"with the reference ENE2017-83665-C2-1-P for the given support.Hervas-Blasco, E.; Navarro-Peris, E.; Barceló Ruescas, F.; Corberán, JM. (2019). Improved water to water heat pump design for low-temperature waste heat recovery based on subcooling control. International Journal of Refrigeration. 106:374-383. https://doi.org/10.1016/j.ijrefrig.2019.06.030S37438310