Suchergebnisse

Thermal energy storage (TES) is moving towards thermochemical materials (TCM) which present attractive advantages compared to sensible and phase change materials. Nevertheless, TCM are more complex to characterize at lab scale and also the implied technology, which belongs to the chemical engineering field, needs to be contextualized in the TES field. System configurations for thermochemical energy storage are being divided into open/closed storage system and separate/integrated reactor system. Reactors, which are the core of the system, are the focus of this paper. Different gas–solid thermochemical and sorption reactors for building applications are reviewed from lab to pilot plant scale, from 0.015 to 7850 dm3. Fixed bed reactors are the most used ones. Mainly, mass transfer is limiting to achieve the expected energy density. The geometry of the reactor and contact flow pattern between phases are key parameters for a better performance. ; Aran Solé would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for her research fellowship. The authors would like to thank the Catalan Government for the quality accreditation given to the research group GREA (2014 SGR 123). The work is partially funded by the Spanish government(ENE2011-22722). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE).

The paper presents an analytical discussion of how to improve the energy efficiency of the steam cushion system operation for a Thermal Energy Storage (TES) tank. The EU's green deal 2050 target policy requires an increase in the energy efficiency of energy production and use, as well as an increase in the share of renewable energy in the overall energy production balance. The use of energy-efficient TES is considered as one of the most important technologies to achieve the objectives of this EU policy. The analyses presented in the paper of energy-efficient operation of steam cushion (SC) systems were carried out by using operational data received from three District Heating Systems (DHSs) that supply heat and electricity to one of the largest cities in Poland and are equipped with the TES systems. These three analyzed TESs differ in capacities from 12,800 to 30,400 m3, tank diameters from 21 to 30 m and shell height from 37 to 48.2 m. The main purpose of using a steam cushion system in the TES tank is to protect the water stored in it against the absorption of oxygen from the surrounding atmospheric air through the surge chamber and safety valves located on the roof of the tank. The technical solutions presented here for the upper orifice for charging and discharging hot water into/from the tank and the suction pipe for circulating water allow to us achieve significant energy savings in the steam cushion systems. Both the upper orifice and the end of suction pipe are movable through the use of pontoons. Thanks to the use of this technical solution, a stable insulating water layer is created above the upper orifice in the upper part of the TES tank, where convective and turbulent transport of heat from the steam cushion space to the hot water stored in the tank is significantly limited. Ultimately, this reduces the heat flux by approximately 90% when compared to the classic technical solutions of steam cushion systems in TES tanks, i.e., for the upper orifice and circulation water pipe. The simplified analysis presented in the paper and comparison of its results with experimental data for heat flow from the steam cushion space to hot water stored in the upper part of the TES tank fully confirms the usefulness of the heat-flow models used.

Energy consumption in buildings accounts for up to 34% of total energy demand in developed countries. Thermal energy storage (TES) through phase change materials (PCM) is considered as a promising solution for this energetic problem in buildings. The material used in this paper is an own-developed shape stabilized PCM with a polymeric matrix and 12% paraffin PCM, and it includes a waste from the recycling steel process known as electrical arc furnace dust (EAFD), which provides acoustic insulation performance capability. This dense sheet material was installed and experimentally tested. Ambient temperature, humidity, and wall temperatures were measured and the thermal behaviour and acoustic properties were registered. Finally, because of the nature of the waste used, a leaching test was also carried out. The thermal profiles show that the inclusion of PCM decreases the indoor ambient temperature up to 3 °C; the acoustic measurements performed in situ demonstrate that the new dense sheet material is able to acoustically insulate up to 4 dB more than the reference cubicle; and the leaching test results show that the material developed incorporating PCM and EAFD must be considered a non-hazardous material. ; The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research innovation programme under grant agreement No 657466 (INPATH-TES). Furthermore, the work is partially funded by the Spanish government (ENE2011-28269-C03-02 and ENE2011-22722). The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543). Alvaro de Gracia would like to thank Education Ministry of Chile for Grant PMI ANT 1201.

From the literature review it was observed that there is no established methodology, neither a common pattern, when selecting a phase change material for a thermal energy storage application. Melting temperature and enthalpy have traditionally been the considered thermal properties for the material selection. Therefore, the authors of this paper propose a new method of investigation on the suitability of a PCM that takes into account not only thermal properties but also health hazard and both cycling and thermal stability. Health hazard is related with the handling of the material, and both cycling and thermal stabilities with durability. This methodology is applied to five different PCM in the 150–200 °C range: salicylic acid, benzanilide, d-mannitol, hydroquinone, and potassium thiocyanate. Results show that for an application in the 150–200 °C range the suitable PCM are benzanilide and d-mannitol. Moreover, hydroquinone is also suitable but only in closed systems. ; The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement N° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). The work is partially funded by the Spanish government (ENE2011-22722). The authors would also like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). Aran Solé would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for her research fellowship. Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861).

This review is focused on the study of the requirement of high thermal conductivity of thermal energy storage (TES) materials and the techniques used to enhance it as this is one of the main obstacles to achieve full deployment of TES systems. Numerical and experimental studies involving different thermal conductivity enhancement techniques at high temperature (>150 °C) are reviewed and classified. This article complements Part 1, which reviews the different requirements that TES materials and systems should consider for being used for high temperature purposes and the approaches to satisfy them. The enhancements identified for this temperature range are the addition of extended surfaces like fins or heat pipes and the combination of highly conductive materials with TES material like graphite or metal foam composites and nanomaterials. Moreover the techniques presented are classified and discussed taking into account their research evolution in terms of maturity and publications. ; The work is partially funded by the Spanish Government (ENE2011-22722 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). The research leading to these results has received funding from the European Union׳s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861).

Thermal energy storage (TES) is a technology with a high potential for different thermal applications. It is well known that TES could be the most appropriate way and method to correct the gap between the demand and supply of energy and therefore it has become a very attractive technology. In this paper, a review of TES for cold storage applications using solid–liquid phase change materials has been carried out. The scope of the work was focussed on different aspects: phase change materials (PCMs), encapsulation, heat transfer enhancement, and the effect of storage on food quality. Materials used by researchers as potential PCM at low temperatures (less than 20 C) are summarized and some of their thermophysical properties are reported. Over 88 materials that can be used as PCM, and about 40 commercially available PCM have been listed. Problems in long term stability of the materials, such as corrosion, phase segregation, stability under extended cycling or subcooling are discussed. Heat transfer is considered both from theoretical and experimental point of view and the different methods of PCM encapsulation are reviewed. Many applications of PCM at low temperature can be found, such as, ice storage, conservation and transport of temperature sensitive materials and in air conditioning, cold stores, and refrigerated trucks. ; The work partially funded by the Spanish Government (ENE2008-06687-C02-01/CON and ENE2011-22722) and the European Union (COST Action COST TU0802 and project EFFIBUILDINGS – FP7-PEOPLE-2009-IIF-/-253914). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534). Eduard Oró would like to thank the University of Lleida for his research fellowship.

At this moment, the global energy consumption in buildings is around 40% of the total energy consumption in developed countries. Thermal energy storage (TES) is presented as one way to address this energyrelated problem proposing an alternative to reduce the gap between energy supply and energy demand. One way to store energy is using thermochemical materials (TCM). These types of materials allow accumulating energy through a chemical process at low temperature, almost without heat losses. In addition, it is a stable way to perform the heat storage and TCM can be implemented for seasonal storage or/and long term storage. This study compares the cyclability, from the thermophysical point of view, CaCl2 which follows a chemical reaction and zeolite which follows a sorption process to be used as TCM for seasonal/long term storage. The main results show that the chemical reaction TCM is more energy-efficient than the sorption TCM. The CaCl2 calculated energy density is 1.47 GJ/m3 , being the best option to be considered to be used as TCM, even though the dehydration process of the zeolite is simpler and it occurs at higher temperatures its calculated energy density is only 0.2 GJ/m3 . ; The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/ 2007-2013) under grant agreement No ENER/FP7/1295983 (MERITS) and under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE). Furthermore, the work is partially funded by the Spanish government (ENE2011-28269-C03-02 and ENE2011- 22722), and the European Union by Cost Action TU0802. The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543).

This study was carried out within the HYBUILD project, as part of the task aimed at developing novel evaporators for compact and direct integration of phase-change materials (PCM) into air-conditioning systems for efficient utilization of solar energy. To achieve this, novel evaporators were designed to contain PCM between refrigerant and heat transfer fluid (HTF) channels, allowing a three-media heat exchange mechanism. This paper experimentally assesses the influence of the configuration/arrangement of the channels on the performance of the evaporators, using three different lab-scale prototypes. Key performance indicators (KPI) relevant for thermal energy storage (TES) and heat exchangers (HEX) were used to study the influence of the design on the performance of the different designs of the novel evaporators. The results show that the change in the PCM, refrigerant, and HTF channel configuration affects the performance of the novel evaporators independently. The coefficient of performance (COP) of the refrigeration system and the energy storage density of the modules are the least affected KPIs (less than 16%), whereas the state of charge (SOC) at thermal equilibrium is the most affected KPI (about 44%). A discussion on how these effects provide unique strength for specific applications is included. ; The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. Boniface Dominick Mselle would like to thank Programa Santander Predoc UdL for his research fellowship.

The implementation of thermal energy storage systems using phase change materials to support the integration of renewable energies is a key element that allows reducing the energy consumption in buildings by increasing self-consumption and system efficiency. The selection of the most suitable phase change material is an important part of the successful implementation of the thermal energy storage system. The aim of this paper is to present the methodology used to assess the suitability of potential phase change materials to be used in two innovative energy storage systems, one of them being mainly intended to provide cooling, while the other provides heating and domestic hot water to residential buildings. The selection methodology relies on a qualitative decision matrix, which uses some common features of phase change materials to assign an overall score to each material that should allow comparing the different options. Experimental characterization of the best candidates was also performed to help in making a final decision. The results indicate some of the most suitable candidates for both systems, with RT4 being the most promising commercial phase change material for the system designed to provide cooling, while for the system designed to provide heating and domestic hot water, the most promising candidate is RT64HC, another commercial product. ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 768824 (HYBUILD). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31 - MCIU/AEI/FEDER, UE). This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) (RED2018-102431-T). This work is partially supported by ICREA under the ICREA Academia programme. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (GREiA 2017 SGR 1537).

Concentrated solar power plants (CSP) combined with thermal energy storage (TES) offers the benefit to provide continuous electricity production by renewable energy feed. There are several TES technologies to be implemented, being the thermochemical energy storage the less studied and the most attractive since its volumetric energy density is 5 and 10 times higher than latent and sensible TES, respectively. Thermochemical energy storage technology is based on reversible chemical reactions, also named thermochemical materials (TCM). One of the main challenges of TCM is to achieve a proper reversibility of the reactions, which in practical conditions leads to lower efficiencies than the theoretically expected. A new concept based on changing from reversible TCM reactions towards TCM consecutive reactions aims to eliminate reversibility problems and therefore improve the overall efficiency. Consecutive TCM reactions can either be based in one cycle, where reactants are needed to feed the reaction, or two coupled cycles which offer the possibility to work without any extra mass reactants input. The plausibility of the implementation of both concepts in CSP is detailed in this paper and case studies are described for each one. ; The authors would like to thank the Catalan Government for the quality accreditation given to the research group GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007–2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). Dr. Camila Barreneche would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-22886.

The final goal of this study is to implement and to test a thermal energy storage (TES) system using different phase change materials (PCM) for solar cooling and refrigeration applications. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly by three parts: heating system, cooling system, and different storage tanks. The pilot plant uses synthetic thermal oil as heat transfer fluid (HTF) and has a working temperature range from 100 ºC to 400 ºC. Two different PCM were selected after a deep study of the requirements of a real solar cooling plant and the available materials in the market, finally d-mannitol with phase change temperature of 167 ºC and hydroquinone which has a melting temperature of 172.2 ºC were used. ; The work is partially funded by the Spanish government (ENE2011-22722). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2009 SGR 534). Antoni Gil would like to thank the Col·legid'Enginyers Industrials de Catalunya for his research appointment. Eduard Oró would like to thank the University of Lleida for his research fellowship.

Sorption is used for absorption/adsorption heat pumps (sorption refrigeration) and sorption for thermal energy storage (TES). This paper is the first review where the research on both applications is shown together. Sorption has advanced very much due to the immense amount of research carried out around heat pumping and solar refrigeration. Moreover, sorption and thermochemical heat storage attracted considerable attention recently since this technology offers various opportunities in the design of renewable and sustainable energy systems. The paper presents the operation principle of the technology and the materials used or in research are listed and compared. Absorption heat pumping and refrigeration research is today more focussed in the decrease of unit costs and increase of energy efficiency, adsorption is focussed in finding more efficient working pairs, and storage is testing the first prototypes and designing new ones with different or enhanced storage materials and new reactor concepts to optimize energy output. ; The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA and DIOPMA (2014 SGR 123, and 2014 SGR 1543, respectively). Dr. Camila Barreneche would like to thank Ministerio de Economia y Competitividad de España for the grant Juan de la Cierva, FJCI-2014-22886.

Renewable energies are main players to ensure the long-term energy supply. Solar power plants with thermal energy storage (TES) are one of the available renewable technologies which have more potential. Nowadays, there are still several aspects in the design and operation of these power plants which need to be improved, such as the correct operation of some specific instrumentation, the compatibility between TES materials and storage tanks materials, and operational process strategies. This paper presents the acquired experience during the design, start-up, and operation of a kWh scale pilot experimental facility built at the University of Lleida (Spain) together with Abengoa Research (Spain) in 2008. The versatility of this facility has allowed simulating real working conditions and therefore testing different TES systems, TES materials, solar power plant components, and operational strategies focused on TES for temperatures up to 400 °C. In the present paper, the authors show the lessons learnt at pilot and present the main problems and limitations encountered, and give advices of this experimental set-up to extrapolate the data to real plant, to provide solutions to technical problems and reduce the cost of commercial plants. ; The authors want to thank specially to Dr. Eduard Oró (today at Institut de Recerca d'Energies de Catalunya, Spain) and Dr. Antoni Gil (today at Massachusetts Institute of Technology, USA) for their help in the design, start-up and operation of the pilot plant facility. The research leading to these results has received funding from Spanish government through CDTI granted projects (Fondo tecnológico IDI-20090393, ConSOLida CENIT 2008-1005) and from Abengoa Solar NT. The work is partially funded by the Spanish government (ENE2008-06687-C02-01/CON, ENE2011-22722, ULLE10-4E-1305, and ENE2015-64117-C5-1-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). GREA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia. This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement NºPIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2017FI_B1 00092).

Thermal energy storage (TES) in molten salts is the storage dominating technology in solar power applications today. In two-tank molten salt storage systems energy density ranges from 30 to 70 kW h/m3 are achievable. The salt material used is a binary system, composed of 60% NaNO3 and 40% KNO3. In the 8 MWhth pilot plant built and tested by Abengoa, the storage tanks were made of steel A516Gr.70 using the Appendix M of code API 650 for their design. A specific testing device was developed to evaluate thermo-mechanical properties, and a study was conducted in order to evaluate tensile properties of A516Gr.70 specimens under operation conditions for the hot tank at the pilot plant that is in contact with molten salts at 380 °C. Results confirmed the outcomes of the work: the reduction of the yield limit, elongation before fracture, and Young modulus at 380 °C after having been 5 min immersed in molten salts. Moreover, after a creep-test simulating operating 7 days conditions during, an additional reduction of the yield limit was measured. ; The research leading to these results has received funding from Spanish government (Fondo tecnológico IDI-20090393, ConSOLida CENIT 2008-1005). The work is partially funded by the Spanish government (ENE2011-28269-C03-02, ENE2011-22722, ENE2015-64117-C5-1-R, and ENE2015-64117-C5-2-R). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and research group DIOPMA (2014 SGR 1543). Dr. Camila Barreneche would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva FJCI-2014-22886.