• Energy Research

The energy transition can only be achieved if the global energy sector is transformed from a fossil-based system to a zero-carbon-based source system. To achieve this aim, two technologies have shown promising advances in high-temperature application. Concentrating solar power (CSP) plants are seen as a key technology to achieve the needed energy transition, and carbon dioxide (CO2) capture and storage (CCS) is a promising technology for decarbonizing the industrial sector. To implement both technologies, molten carbonate salts are considered promising material. However, their corrosive behavior needs to be evaluated, especially at high temperatures, where corrosion is more aggressive in metal structures. This paper presents an experimental evaluation of the static corrosion of two molten carbonate salts, a Li2CO3-Na2CO3-K2CO3-LiOH∙H2O (56.65-12.19-26.66-4.51wt.%) mixture and a Li2CO3 salt, under an air atmosphere with five corrosion-resistant metal alloys, including Alloy 600, Alloy 601, Alloy 625, Alloy 214, and Alloy X1. In this study, the corrosion rate and mass losses were quantified. In addition, in all the cases, the results of the experimental evaluation showed corrosion rate values between 0.0009 mg/cm2·yr and 0.0089 mg/cm2·yr.

Increasing the energy efficiency of residential and non-residential buildings is a crucial point towards the development of the sustainable cities of the future. To reach such a goal, the commonly employed intervention measures (for instance, on facades and glass) are not sufficient and efforts in reaching a fully renewable energy generation are mandatory. In this context, this paper discusses the applicability of a system with solar and biomass as the main energy sources in different climates for heating, cooling, domestic hot water and electricity generation in office buildings. The energy system includes solar thermal collectors with thermoelectric generators, a biomass boiler, a reversible heat pump/organic Rankine cycle and an adsorption chiller. The results showed that the system can operate with a share of renewables higher than 70% for all energy needs, with up to 80% of the overall energy demand supplied only by solar and biomass sources even in the northern locations.

Abstract This work investigates the technical and economic feasibility of a Liquid Air Energy Storage (LAES) for building demand management applications. The thermodynamics and processes of the LAES configuration, as well as the description of the daily cooling energy demand profile, are described in details and the assumptions and constrains are pointed out. The quantitative analysis has been carried out for a daily cooling energy demand of an existing office building, located in Singapore, locality characterized by a typical hot climate. A thermodynamic analysis has been carried out for LAES configuration by means of the Aspen HYSYS® process simulation code. Under the technical assumptions formulated, LAES achieves an overall round trip efficiency of 45% with a specific consumption of 0.20 kWh/kgLA. The exergy analysis shows that LAES is characterized by an exergy efficiency of 84% and 67% for the liquefaction and the discharge processes, respectively; the compressor and the power turbines account for the highest exergy losses. Finally, the economic results show that under the actual condition of peak tariff and off-peak tariff in Singapore, the investment proposed is not convenient but in case of high values of LAES round trip efficiency and lower OPT the investment may be attractive. However, future works have to deal with the limitations introduced in the analysis, such as neglecting LAES operation costs, and the uncertainty related to capital costs figures.

The design of thermal energy storage (TES) tank is the key part that can limit charging and discharging process. Most research findings highlight that the use of fins augments the heat transfer rate. This work experimentally investigates the use of aligned copper wools as fillers to enhance the thermal performance of a lab-scale shelland- tube TES tank filled with phase change material (PCM). Two copper wools with different fibre thicknesses were chosen and discretely laid around the TES tank tubes in two design patterns. Accordingly, five shell-andtube TES tank configurations were obtained, including the reference, for performance evaluation. The TES tank was loaded with n-octadecane as PCM for all the cases studied. The results showed up to a 16 % reduction in melting time with the inclusion of copper wool. The TES tank significantly increased the mean power during charging (53 %) and discharging (205 %). The addition of metal wool into the TES tank enables the PCM to release the heat at a constant temperature during the entire phase transition process. And the overall efficiency of the TES tank was found to get improved. Therefore, a copper wool integrated TES tank would be a beneficial addition to thermal energy storage systems. This project was funded by the European Union's Horizon Europe Research and Innovation Programme under grant agreement 101084182 (HYBRIDplus). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. This work was partially funded by the Ministerio de Ciencia e Innovación - Agencia Estatal de Investigación (AEI) (PID2021-123511OB-C31- MCIN/AEI/10.13039/501100011033/FEDER, UE and RED2022-134219-T). This work is partially supported by ICREA under the ICREA Academia programme. The authors would like to thank the Department de Recerca i Universitats of the Catalan Government for the quality accreditation given to their research group (2021 SGR 01615). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia.

Increase in energy demand is shaping both developed and developing countries globally. As a result, the endeavour to reduce carbon emissions also encompasses electrical energy storage systems to ensure environmentally friendly power production and distribution. Currently, the scientific community is actively exploring and developing new storage technologies for this purpose. The focus of this work is to compare the eco-friendliness of a relatively novel technology such as liquid air energy storage (LAES) with an established storage solution such as Li-Ion battery (Li-ion). The comparison is carried out through Life Cycle Assessment (LCA) methodology which aims to assess the environmental impacts from each life stage, according to different impact categories. In particular, the study refers to the unitary storage and the delivery of electricity as well as cooling energy, considering all the inefficiencies and limits of each technology. The results show that in the full electric case study Li-ion battery environmentally outperform LAES due to (1) the higher round trip efficiency and (2) the significantly high environmental impact of the diathermic oil utilized by LAES, accounting for 92 % of the manufacture and disposal phase. Conversely, the cogeneration case study highlights that the "flexibility" and "dualism" of LAES, capable to efficiently deliver both electricity and cooling, offset the impact related to the higher electricity consumption during the use phase. Notably in energy mix frameworks with high share of primary energy source from fossil fuels, cogenerative LAES demonstrates superior environmental performance compared to Li-ion battery (i.e. 1302 kgCO2eq/MWhe vs 1140 kgCO2eq/MWhe for Singapore energy mix), attributable to its reduced electricity consumption.

The energy consumption in the built environment represents one of the major contributors of carbon emissions to the atmosphere. This leads to the need for a transition in the building sector and the introduction of policies that pursue high efficiency in residential and non-residential buildings with an increasing share of renewables. The benefit of the use of thermal energy storage is widely recognized to increase the efficiency of energy systems in different building typologies, to help in the introduction of renewable energies in buildings and to reduce the energy demand needed for heating and cooling. Nowadays, different thermal energy storage technologies are available, including sensible, latent, and sorption and chemical reactions (also called thermochemical) energy storage. Although in the past twenty years, the scientific literature showed an increasing trend in the research of thermal energy storage integrated to the building sector, it was only in recent years that this concept was extended to the built environment, which includes residential and non-residential buildings, districts, and urban networks. This paper provides a comprehensive review and classification of thermal energy storage technologies applied in the built environment considering the trends and the future perspective of the past and current research. This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31 - MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) (RED2018-102431-T). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREiA (2017 SGR 1537). GREiA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme.