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Open Access

Modelling the building-related photovoltaic power production potential in the light of the EU's Solar Rooftop Initiative

2024, Molnar, Gergely, Cabeza, Luisa F., Chatterjee, Souran, Ürge-Vorzatz, Diana

Decarbonizing the building sector is key to meet the EU climate goals by 2050. Although the recent policies recognized the importance of on-site solar energy production in the energy transition, there are only a few modelling studies analyzing how much the gap between the technically possible and policy-driven power generation of rooftop photovoltaic (PV) panels can be reduced. This study, therefore, uses geospatial techniques and the high-resolution Building Integrated Solar Energy (BISE) supply model to estimate the main spatial and temporal characteristics of the rooftop PV energy production potential. To support decision-making, important implications of the Solar Rooftop Initiative action plan of the European Commission on the future dimension of the PV electricity supply are also assessed in the context of the achievable potential. The modelling results indicate that the current rooftop PV technical potential could be about 2.7 PWh, being in similar extent with the EU power consumption. The largest country-level PV potentials can be found in Germany, France, Italy and Poland, with an increase of 30% by 2060. Our findings also underline that by following the latest policies, major improvement could be achieved in the EU's rooftop solar energy production by around 2040, depending greatly on the structure and energy efficiency niveau of the future building stock.

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Open Access

Sustainability of international research: evidence from an H2020 European project

2023, Fabiani, Claudia, De Albuquerque Landi, Fabiana Frota, Cabeza, Luisa F., Pisello, Anna Laura

Greenhouse gas emissions reduction is a critical topic in the scientific community, as researchers strive to produce knowledge for the betterment of society. However, it is important to acknowledge that researchers themselves engage in activities that have a significant environmental impact. Group meetings and conferences are under the spot due to their extensive contribution to emissions through travel, catering, hosting, and other event-related activities. To address this issue, our work aims to conduct an environmental diagnosis of an ongoing H2020 European project, focusing on the impacts associated with the periodical group meetings organized in each country involved. We also sought to evaluate researchers' stance on online meetings and collected environmental and personal opinions through dedicated online forms. Results show that while travel is the primary contributor to emissions, catering, meeting structures, and hosting support should not be overlooked. Conference location and availability of public transportation also play a crucial role in the final impact of the event, as they affect directly the 87% share of emissions due to travels. Besides, using local distributors and reducing hotel stays (representing about 5% of the final impact) may reduce the potential environmental burden of these events. On the other side, besides the obtained positive feedback from online meetings, in-person activities are still more effective for reinforcing human bonds and collaborations.

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Open Access

Analysis of a heat pump-based energy system exploiting a low GWP refrigerant in different European climates

2023-08-25, Rehman, Omais Abdur, Palomba, Valeria, Frazzica, Andrea, Cabeza, Luisa F.

The objective of this research is to assess the operation of a heat pump (HP) under varying climatic conditions in Europe. To achieve this, a Dymola model is developed for a solar-assisted reversible water-to-water HP that utilizes a low global warming potential (GWP) refrigerant, R1234ze(E), and includes thermal and electrical energy storage systems. Experimental data is used to validate the primary components of the model. Simulations are conducted for both summer and winter seasons to determine the system’s overall annual performance. The analysis covers energy exchange between the system and the grid and utilizes key performance indicators such as self-sufficiency and self-consumption index. Furthermore, a techno-economic analysis is conducted to determine the payback period of the heating and cooling energy system based on the components’ capital expenditure and available incentives.

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Open Access

Renovation assessment of building districts: Case studies and implications to the positive energy districts definition

2023, Guarino, Francesco, Rincione, Roberta, Mateu Piñol, Carles, Teixidó Cairol, Mercè, Cabeza, Luisa F., Cellura, Maurizio

As the built environment is among the main contributing sectors to climate change, it is needed to investigate new paradigms to push decarbonization efforts towards the ambitious objectives defined internationally. It is a shared understanding that shifting the perspective from the single building to the district perspective is required to fully take into consideration the complexity of all interactions undergoing within the built environment, thus the concept of Positive Energy District emerged as a district with annual net zero energy import and net zero CO2 emission working towards an annual local surplus production of renewable energy. In this framework, this paper explores the investigation of the potential for achieving the level of Positive Energy District in a group of nonresidential buildings in Balaguer, Catalonia, Spain. These buildings, occupying 8,825 m2 in the city centre, require significant refurbishment for improved energy performance. The analysis includes building energy modelling and simulation, renovation studies, several alternative balance calculations, and carbon emissions assessment. The paper also considers mobility and embodied energy and their impact on energy/carbon balances. The results show that Positive Energy Districts carbon and primary energy balances are not met with rooftop PV installations when retrofitting an existing district towards the Positive energy target but further significant PV areas (roughly + 50%) are required to meet merely the use stage balances: negative results are traced when mobility and embodied energy are computed. A formulation alternative to the simple mathematical balance to facilitate the diffusion of Positive Energy District as catalyst of urban decarbonisation could be needed, including context factors and alternative systems (e.g., rating systems).

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Open Access

Modelling the building-related photovoltaic power production potential in the light of the EU's Solar Rooftop Initiative

2024, Molnar, Gergely, Cabeza, Luisa F., Chatterjee, Souran, Ürge-Vorzatz, Diana

Decarbonizing the building sector is key to meet the EU climate goals by 2050. Although the recent policies recognized the importance of on-site solar energy production in the energy transition, there are only a few modelling studies analyzing how much the gap between the technically possible and policy-driven power generation of rooftop photovoltaic (PV) panels can be reduced. This study, therefore, uses geospatial techniques and the high-resolution Building Integrated Solar Energy (BISE) supply model to estimate the main spatial and temporal characteristics of the rooftop PV energy production potential. To support decision-making, important implications of the Solar Rooftop Initiative action plan of the European Commission on the future dimension of the PV electricity supply are also assessed in the context of the achievable potential. The modelling results indicate that the current rooftop PV technical potential could be about 2.7 PWh, being in similar extent with the EU power consumption. The largest country-level PV potentials can be found in Germany, France, Italy and Poland, with an increase of 30% by 2060. Our findings also underline that by following the latest policies, major improvement could be achieved in the EU's rooftop solar energy production by around 2040, depending greatly on the structure and energy efficiency niveau of the future building stock.

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Embargo

Characterisation of the COMFORTBOARD gypsum board for thermal energy storage in buildings

2024, Marín, Paula E., Ushak, Svetlana, Gracia Cuesta, Alvaro de, Cabeza, Luisa F.

Currently, the construction sector contributes considerably to the total energy consumption and greenhouse gas emissions into the atmosphere. Thermal energy storage (TES) systems are alternatives to increase the thermal inertia of buildings, aiming to use less energy, improve thermal comfort and reduce temperature fluctuations of interior spaces. One of the possible applications in buildings is to increase their thermal mass by impregnating phase change materials (PCM) in porous construction materials, e.g., gypsum boards. In this investigation, a commercial gypsum board impregnated with PCM (Knauf Comfortboard - BASF) was investigated by carrying out a structural and thermal characterisation. The thermal response obtained agrees with the product's technical data sheet provided by the supplier. The results of the thermal characterisation show that the inclusion of PCM in the gypsum board decreased the U-value by 2 % compared to the control sample (no PCM), increased the heat storage capacity by around 45 %, improved the thermal dynamic characteristics of the material by decreasing the thermal stability coefficient from 0.92 to 0.76 and increasing the thermal lag from 0.27 to 0.49 h. Our results sustain the potential application of commercial gypsum boards with PCM under environmental conditions across a wide range of daily temperature fluctuations (e.g., The North of Chile).

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Open Access

Lactic acid production from cow manure: Technoeconomic evaluation and sensitivity analysis

2023, Garrido, Ricard, Cabeza, Luisa F., Falguera Pascual, Víctor

Recently, the industrial focus has shifted to renewable raw materials due to the exhaustion and rising pressures about environmental and political issues. Lignocellulosic biowaste can be derived from a range of sources, such as animal manure, forestry waste, and agricultural waste, and it can be transformed into lactic acid through a biochemical process. There are 942.63 million cattle in the world and annually generate 3.7 billion tons of manure, which could be used to produce lactic acid. The economic viability of a lactic acid plant from cow manure has not yet been determined and is, thus, considered in this study. Using the modeling program Aspen Plus data and other sources, as well as collecting all economic inputs, the feasibility analysis of a lactic acid plant handling cow manure is assessed in this paper. Three scenarios are calculated to check the feasibility depending on the plant size: scenario I handles 1,579,328 t·year-1, scenario II handles 789,664 t·year-1, and scenario III handles 315,865 t·year-1. The results demonstrate that treating the tested lignocellulosic biomass for the manufacture of lactic acid is economically feasible because the economic analysis shows positive net present values for scenarios I, II, and III. The technoeconomic analysis reveals that the minimum lactic acid selling price for scenario I is 0.945 EUR·kg-1, which is comparable to the cost of commercial lactic acid produced from starch feedstock. Scenario II achieves a minimum selling price of 1.070 EUR·kg-1, and scenario III 1.289 EUR·kg-1. The sensitivity analysis carried out reveals that the factor with the biggest impact on the NPV is the yield. Moreover, this study provides a model of industrial application and technoeconomic evaluation for lactic acid production from cow manure.

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Open Access

Molten salts tanks thermal energy storage: aspects to consider during design

2024, Prieto, Cristina, Blindu, Adrian, Cabeza, Luisa F., Valverde, Juan, García, Guillermo

Concentrating solar power plants use sensible thermal energy storage, a mature technology based on molten salts, due to the high storage efficiency (up to 99%). Both parabolic trough collectors and the central receiver system for concentrating solar power technologies use molten salts tanks, either in direct storage systems or in indirect ones. But even though this is a mature technology, it still shows challenges in its implementation and operation. This paper underscores the critical importance of stringent design criteria for molten salt tanks in thermal storage technology. Focusing on the potential ramifications of design failures, the study explores various dimensions where an inadequate design can lead to severe consequences, even jeopardizing the viability of the entire technology. Key areas discussed include structural integrity, corrosion, thermal shock, thermal expansions, and others. By elucidating the multifaceted risks associated with design shortcomings, this paper aims to emphasize the necessity of thorough reviews and adherence to robust design principles for ensuring the success, safety, and sustainability of thermal storage technology.

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Open Access

Experimental evaluation of different macro-encapsulation designs for PCM storages for cooling applications

2023, Rehman, Omais Abdur, Palomba, Valeria, Vérez, David, Borri, Emiliano, Frazzica, Andrea, Brancato, Vincenza, Botargues, Teresa, Ure, Zafer, Cabeza, Luisa F.

Extensive research has been conducted on utilizing phase change materials for cooling applications, making it one of the most explored techniques in this domain. This research paper presents a comprehensive performance evaluation of a latent heat thermal energy storage unit featuring three distinct macro-encapsulation designs for phase change materials. The study aims to assess the thermal performance, efficiency, and practical applicability of these macro-encapsulation designs in a storage system. The PCM macro-encapsulation designs under investigation include cylindrical and rectangular shapes, each possessing different geometry. Two different configurations have been considered in this study. One configuration contains same PCM mass in order to have similar storage capacity while the other configuration has maximum PCM mass that can be inserted inside the tank. The used phase change material is a salt hydrate with melting temperature of 17 °C. The experimental setup consists of a controlled test rig that simulates real-world conditions and enables the comparative analysis of the three designs. Key performance parameters such as the charging and discharging time, temperature profiles, heat transfer rate, and energy storage/retrieval rates are measured and analysed. The results obtained from the experimental study provide valuable insights into the thermal behaviour, energy storage capacity, and overall effectiveness of the three macro-encapsulation designs. It is important to mention that use of an encapsulation design is highly dependent on application. The findings of this study contribute to the understanding of the impact of different macro-encapsulation designs on performance of thermal energy storage units. The results serve as a basis for optimizing macro-encapsulation designs, improving the efficiency and reliability of latent heat storage systems, and promoting their wider adoption in various energy management applications.

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A transient heat losses model for two-tank storage systems with molten salts

2023, Tagle-Salazar, Pablo D., Prieto, Cristina, López-Román, Antón, Cabeza, Luisa F.

Concentrating Solar Power (CSP) is a proven and mature technology for energy supply. In recent years, electricity generation based on this technology has increased worldwide, to a large degree due to its high dispatchability when coupled with an energy storage system. Commercially, most plants store the energy in molten salts in a two-tank configuration. This study focuses on this storage configuration and proposes a mathematical model for the thermal losses in these tanks, both at nominal conditions and during transients. With this model at its core, a computational tool for thermal performance analysis in OpenModelica is developed. This dynamic thermal model includes the estimation of local heat loss due to assembly defects, which are heat flows that cannot be determined by theoretical modelling. The development of a semi-empirical correlation for estimating local heat loss is also presented. Simulation results showed that this local heat loss may represent a share about 40% of the total heat loss in a small-scale tank. A comparison of the characteristics of the model proposed in a previous work is also presented to establish the innovation of the model. Two thermal storage systems with different tank designs and sizes were simulated to compare the results using the present model with data available in the literature. Results show good agreement in transient thermal behaviour of heat flows, temperatures, and cooling rates when compared with data from other authors for the same tank.