Thermoelectric (TE) heating, ventilation, and air-conditioning (HVAC) systems represent a sustainable alternative to conventional vapor-compression technologies, but they remain limited by modest coefficients of performance (COPs) and a lack of robust optimization methods. This study presents a comprehensive experimental, computational, and deployment pipeline to address these challenges. A custom-built test rig was designed to generate high-quality data under controlled laboratory conditions, capturing all key thermodynamic variables relevant to TE operation. Multiple regression and machine learning models were systematically benchmarked, with Linear Regression emerging as the most accurate and parsimonious predictor of hot-side exit temperature. Beyond statistical metrics, predictions were validated against recomputed heat transfer rate and COP, ensuring thermodynamic consistency and physical interpretability. The best-performing model was embedded into an interactive Shiny-based graphical user interface (GUI) to bridge the gap between research outputs and practical usability. The GUI allows real-time adjustment of system inputs, dynamic prediction of outputs, and visualization of performance through bar, point, and time-series charts, supported by logged historical data. By combining experimental rigor, comparative regression analysis, thermodynamic validation, and deployment into an accessible decision-support tool, this work demonstrates a practical pathway for advancing TE HVAC systems from laboratory studies toward real-world applications in sustainable building energy management.

Thermochemical energy storage (TES) is emerging as a transformative solution for enhancing thermal energy management in buildings and industrial applications. Unlike conventional sensible and latent heat storage, TES systems store energy through reversible chemical reactions, offering significantly higher energy densities and minimal standby losses. This review provides a comprehensive overview of recent developments in TES materials and system configurations, including both closed-cycle systems (e.g., chemical heat pumps, adsorption/absorption cycles) and open-cycle systems integrated with solar thermal collectors. Advances in material engineering—particularly in salt hydrates, composite sorbents, and nanostructured materials—have led to improvements in cyclic stability, regeneration temperature, and thermal efficiency. The paper also highlights innovative reactor designs such as fixed-bed, fluidized-bed, and plate-fin heat exchangers, alongside smart control and additive manufacturing approaches. Key technical challenges, including reaction kinetics, long-term stability, and heat/mass transfer complexity, are discussed to identify future research needs. This review aims to support the development of high-performance, scalable TES systems for sustainable and flexible energy infrastructure.

The accelerating impacts of climate change and the growing urgency to limit global warming have placed decarbonisation at the centre of international policy, technological innovation, and economic transformation. Achieving a net zero carbon future requires coordinated action across energy systems, industrial processes, transport, urban infrastructure, and societal behaviour. Global Decarbonisation (GD) is established as an international peer reviewed open access journal dedicated to advancing research that supports this transition. This editorial outlines the journal’s scope, interdisciplinary focus, and commitment to publishing high quality research that contributes to the development of practical pathways toward a low carbon global economy.

Supercooled phase change materials are highly promising for space heating applications due to their ability to release latent heat upon crystallisation initiation, even at ambient temperatures. This property enables more effective solar energy utilisation and significant reductions in carbon emissions for short-to medium-term thermal storage. However, the widely used sodium acetate trihydrate has a melting point of 56-58 degrees C, which often necessitates auxiliary heating in cold seasons or when sudden short-term demand arises during morning warm-up and evening peaks. To address this limitation, this study proposes a bypass tank configuration incorporating a coil-integrated latent heat storage unit filled with erythritol, enabling rapid high-temperature boosting (10-20 degrees C) during morning warm-up and evening peak periods for a short time. The erythritol tank is charged via PV-powered electric heaters and engaged only when sodium acetate trihydrate storage cannot maintain the required supply temperature and heating. A dynamic model of the coil-integrated tank was developed, experimentally validated, and further examined through CFD simulations to capture discharge behaviour under varying inlet temperatures and flow rates. Real weather data and building heating profiles were used to evaluate the system's practical boosting capability. Results show that a 35 L erythritol tank can sustain outlet temperatures above 50 degrees C at moderate flow rates, deliver boosting durations of up to 22 min, and reliably support dual-peak operation within a single day. The findings highlight the effectiveness of erythritol as a high-temperature bypass storage medium for improving quick start-up performance, reducing reliance on auxiliary electric heaters, and enhancing operational flexibility in solar-assisted heating systems.

Solar-powered organic Rankine cycles (s-ORCs) are promising technologies for converting solar radiation into electrical energy, offering a viable alternative to conventional photovoltaics. However, the intermittent nature of solar radiation presents operational challenges, as these systems cannot regulate their heat input and rely entirely on solar energy availability. This study investigates the transient performance of a small-scale s-ORC system without thermal energy storage, focusing on how operational parameters influence system behaviour under variable solar conditions. A simulation model is developed, integrating effectiveness–NTU-based heat exchanger models and a validated expander–generator coupling sub-model that accounts for real-world responses such as torque balance, rotational speed, and internal leakage. Key control parameters, including the flow rates of the refrigerant, cooling water, and thermal oil, are examined to assess their influence on overall performance. The results show that solar heat input is the dominant factor affecting system efficiency, followed by the cooling water flow rate, which has a more significant impact than thermal oil flow. Based on a one-day simulation, the expander’s volumetric efficiency was found to average around 60% due to leakage losses, and the expander predominantly operated under off-design conditions. The generator efficiency varied between 49% and 58%, with lower rotational speeds resulting in better conversion efficiency.

Emerging trends in heat pump (HP) and electric vehicle (EV) adoption within communities aim to reduce carbon emissions in the heating and transportation sectors. However, these technologies rely on grid electricity, whose carbon intensity varies over time. This study explores how the carbon-saving potential of these technologies can be further enhanced through demand-shifting operations and renewable energy integration. The research compares photovoltaic–thermal (PV/T) and hybrid solar heat pump systems that integrate EV charging and PCM-enhanced heat storage to improve space heating efficiency under low solar irradiance in the UK while reducing CO2 emissions. The study simulates solar collector configurations and sizes, combining PV modules and heat pumps to enhance system performance. Control systems synchronize operations with periods of low grid CO2 intensity, minimizing the environmental impact. The analysis evaluates PV/T systems, separate PV and thermal collectors, highlighting their energy efficiency and CO2 reduction potential. Control systems further optimize HP operation and EV charging during periods of high renewable energy availability, preventing uncontrolled use that could result in elevated emissions. Using real weather data and a detailed building model, the findings show that a solar-assisted HP with 100% thermal collectors achieves a daily COP of 3.49. Reducing thermal collectors to 60% lowers the COP to 2.57, but PV output compensates, maintaining similar emission levels. The system achieves the lowest emission with high-efficiency evacuated flat plate PV/T collectors.

The rapid adoption of electric vehicles (EVs) presents significant challenges to urban energy networks due to increased demand and potential overloading risks. Integrating renewable energy sources (RES) offers a sustainable solution, reducing carbon emissions while meeting future energy needs. Using Nottingham, UK, as a representative case within a broader European urban energy context, this study investigates the interactions between EVs, RES, and urban energy systems, focusing on supply-demand dynamics under constrained renewable output conditions. A stochastic modelling approach, guided by the Future Energy Scenarios (FES) developed by the National Energy System Operator (NESO), is employed to analyse EV-RES integration under four distinct scenarios - Consumer Transformation, System Transformation, Leading the Way, and Falling Short - projected for 2035 and 2050. Key focus areas include balancing energy supply and demand, managing peak loads, and utilising Vehicle-to-Grid (V2G) technology to address grid stability issues. Results demonstrate the heightened challenges of integrating EVs on days with suboptimal renewable energy generation, where energy shortfalls exacerbate system strain. By 2050, low renewable energy generation days aggravate energy shortfalls, emphasising the importance of V2G. In the most constrained scenario, up to 97 % of EVs remain uncharged or partly charged, demonstrating the risk of severe energy deficits. Conversely, in an ambitious renewable energy scenario, significant renewable utilisation is achieved but is accompanied by challenges such as overgeneration and energy management complexities.

Supercooled phase change materials offer a promising solution for space heating due to their ability to release latent heat upon crystallization initiation, even when stored at ambient temperatures. This unique property makes them ideal for solar-assisted space heating, where external activation enables on-demand heat release, addressing the critical need for energy-efficient heating solutions. In this study, a system promoting demand shifting is proposed, aiming to transfer energy consumption from morning and evening peak periods to daytime and high solar irradiance days, thereby enhancing the efficiency of solar heat pumps and reducing grid stress through the use of supercooled crystallization-controllable phase change materials. A model was developed, consisting of evacuated tube collectors, a buffer tank, heat storage tanks with crystallization-controllable phase change material, and a building heating demand model. The study introduces a novel system control methodology, focusing on an effective operation of tank shifting based on the heating requirement and solar energy availability. Real weather data were used to calculate system performance. With 50 m2 of collectors, a 1000-liter buffer tank, and a heat pump with a maximum output of 7 kW, the heat storage tanks are charged and discharged following the developed operational methodology. The system achieved a weekly coefficient of performance of 3.56 and successfully shifted electricity demand to solar hours, with only 28.5% of the total consumption occurring during domestic morning and evening peak times.

Electric vehicles (EVs) and heat pumps (HPs) are key in reducing carbon emissions from transportation and domestic heating, yet their adoption may increase peak load demands on electrical networks. One of the aims of this research is to assess the potential impact of uncontrolled EV charging on community-scale distribution networks, exploring how this could stress the existing electrical infrastructure. It also explores the role of EVs in Vehicle-to-Grid (V2G) and smart charging applications, aiming to enhance community distribution systems. The study investigates the maximum stabilisation level achievable under various scenarios, highlighting the importance of smart energy management in integrating renewable energy and addressing uncertainties in the modelling process. Additionally, this study discusses the proposed systems' scalability, consumer behaviours' impact on the suggested energy solutions, and the potential implications of recent technological advancements for simulated communities. The research employs a sophisticated, integrative approach, combining stochastic methods with several robust energy software. Key findings suggest that uncontrolled EV charging can lead to grid capacity issues at high EV penetration levels, particularly during colder months. While smart charging and V2G technologies can moderate peak loads in many scenarios, achieving 100% sustainable technology integration requires enhanced energy management or increased network capacity, especially in winter. Wind and solar power integration demonstrates strategic complementarity, particularly in winter, enhancing the reliability and stability of the community grid. It is also observed that peak solar generation hours misalign with the community's highest demand times, posing challenges for solar energy utilisation in EV charging in residential-based areas.

This paper proposes a novel approach for improving the performance of a direct-expansion solar-assisted heat pump (DX-SAHP) system by integrating a crystallisation controllable phase change material (PCM) and building energy demand shifting strategy. The proposed system aims to reduce buildings' energy consumption while utilizing solar energy efficiently. Sodium acetate trihydrate (SAT) as the crystallisation controllable supercooled PCM has a promising feature of releasing the stored latent heat when it is externally triggered, allowing the user to control the stored heat whenever needed. In the study, the PCM can store the thermal energy generated by the DX-SAHP during peak solar hours in an efficient way. This stored energy can be released when solar energy is unavailable, but the heating is requested. This approach not only reduces the load on the heat pump system but also makes efficient use of the stored thermal energy by crystallisation controllable PCM. A detailed controlling methodology of the system is given, and heating output is controlled considering the level of solar irradiance. The proposed system was modelled and simulated using MATLAB, and the results show that the integration of crystallisation controllable PCM and building demand shifting strategy can significantly reduce the energy consumption of the buildings. On the low solar radiation day, the COP improvement compared to the air source heat pump system was found 9.4%, this improvement value can reach 77% on high solar radiation days. The system can also effectively utilize solar energy and reduce the overall carbon footprint of buildings.

Supercooled sodium acetate trihydrate (SAT) allows the latent heat can be released when it is externally trig-gered regardless of the supercooling degree. Thus, the implementation of SAT into heating systems can eliminate the negative effects of weather variation and increase the utilization of solar energy by storing the heat for days. However, supercooled PCMs can lose a serious amount of latent heat when their temperature falls to ambient temperature. Moreover, the poor heat conductivity of the SAT can cause providing insufficient temperature in the houses for different heating profiles which require auxiliary heating. In this study, the dynamic thermal behaviour of a supercooled PCM-immersed storage tank for heating different dwellings is investigated based on different activation orders of the PCM tubes. The controlled PCM activation order shows that the hot water supply temperature can be increased compared to the activation of all tubes at midnight. Controlled triggering resulted in performance improvement in all heating profiles by an increment of 1.5 degrees C, but it is more promising for the Eco-house heating profile as it reaches 4.3 degrees C. Moreover, this method reduces the daily heat loss from the PCM storage tank by up to 1.3 kWh. It is also found that the PCM loses its 35% of latent energy after three days of storage.

This study aims to build a dynamic model of a direct steam generation (DSG) solar power system coupled with a steam accumulator to meet electricity demands for a hospital under transient environmental conditions in Libya. The main components of the system are DSG parabolic trough collectors, a steam accumulator, a turbine, a condenser and a circulation pump. The system is modelled via using Simulink\Simscape software blocks with integrated MATLAB functions to run a dynamic simulation. As the simulation tool reflects the transient operation of the components, advanced control strategies were applied to the model. Using the proportional integral controller (PI controller), safe operation of the system is secured by pump flow rate control, safe turbine oper-ation is provided by pressure control and power output is matched with the demand by using a throttle valve control. 1584 m2 solar collector area and 160 m3 total volume of pressurized steam tank are used in the simulation considering the electricity demand of the hospital and solar radiation in the location. The produced work output was controlled to match the demand profile of the hospital, which needs 200 kW in the peak period and 50 kW at the night. The designed system shows a maximum thermal efficiency of 23.5% for the operation condition.

Dual-source heat pump unit can utilize the evaporation of the refrigerant at two different pressures. By adopting an ejector, high-pressure refrigerant stream can be used to lift compressor inlet pressure which results in a higher coefficient of performance (COP). This study proposes a renewable energy sourced and high-efficiency heat pump system which can be easily building integrated to offer a renewable heating solution. The system is devised on the complementation of dual thermal sources; one is air and the other one is solar, to maximize the utilization of ambient energy for highly efficient operation of heat pump. Using the advantage of the relatively lower operating temperature in the solar collector line, the thermal efficiency of the collector would be sufficient in winter. Adaptation of photovoltaics in the collector as a PV/T unit, will benefit the system from the produced electricity for further reduction of the demand from the grid. Along with the use of PV/T collector, the system can be potentially carbon neutral for larger collector areas. In this study, the performance improvement potential of a dual-sourced heat pump unit with an ejector as a booster is investigated for different locations in Turkey which presents different solar and weather profiles. The optimum collector evaporation temperatures are determined, and COP improvement potentials are discussed for different conditions. For a heating supply of 5 kW, the COP of the system can be improved by 22.6 % under 400 W/m2 and 10 degrees C ambient using 15 m2 PV/T collector. Including the electricity generated from the PV, reduction of the electricity demand from the grid can reach to 75 % for the same conditions.

The demand for electricity has been increasing worldwide and it is predicted that this trend will be particularly reinforced in developing countries by the gradual electrification of the transport sector and heat generation in buildings. The energy supply infrastructure required to meet the additional electricity demand should be carefully managed in light of the climate change carbon emission targets and commitments. A large proportion of the new electricity loads will be met from renewable sources. Therefore, means of power storage become vital to smooth out the intermittent nature of these energy supplies. The introduction of Electric Vehicles (EVs) could provide a viable and dynamic power storage solution through the concept of Vehicle-to-everything (V2X). This involves the storage of renewable energy (RE) in EV batteries during the charging cycle and restitution to the grid (V2G) or homes (V2H) when needed. In this context, this paper presents a methodology involving several strategies to stabilise the grid system and examines the impact of various types of EVs and heat pumps (HPs) for supplying heat in buildings. The results of this research approach show that the synergy of using V2H could reduce the carbon footprint of a typical domestic building in the United Kingdom (UK) by up to 87% and potentially recover up to 21.9 kWh/day of surplus renewable energy.

In short to long-term heat storage, the heat loss of common phase change material (PCM) systems is a big problem where heat is lost continuously to the ambient environment and is thus wasted, even when the system is not in use. Controllable supercooled PCM in the proposed system offers a solution to this problem. Latent heat is only released when the supercooled PCM is triggered to induce crystallization, so it can be stored at ambient temperature. To control the release of heat, the installation will be constructed as a group of PCM storage units, each with its own trigger, which can be activated according to the heating demand of a building perhaps over several days. The proposed versatile PCM energy storage system can play an essential role in synchronizing energy demand and supply, on a short to long-term basis (days/weeks). In this study, an electrical triggering mechanism is constructed and tested in the laboratory to control the crystallization of the PCM. The PCM temperature increased from 20 degrees C to 56.4 degrees C in 20s after triggering. After validation of controllable crystallization and melting time, a solar-assisted heat pump coupled with supercooled PCM storage units was simulated considering the heating demand profile of an eco-house in Nottingham, UK. The charging time of the PCM tank was found 6.5h when 8 cm diameter PCM tubes were adapted. During discharging period, the hot water supply temperature was achieved at higher than 43 degrees C, considering the one-day heating profile of the building.

ABSTRACT This paper presents the development of a sustainable and affordable domestic refrigerator for rural areas where grid setting is weak or non-existent. The refrigerator uses a miniature refrigeration unit based on a micro direct current (DC) compressor, which can adjust its speed according to photovoltaic output variation with solar radiation intensity, in order to maximize cooling production. The experimental investigation aims to define the cooling capacity management of the refrigerator through the use of phase change materials (PCMs). PCM packs in the fridge are charged during the period of high solar radiation and, afterward, melting of PCM releases cooling to maintain a cold temperature for extra hours when solar radiation is low or not available. The paper presents the design and construction of an experimental refrigerator with a miniature refrigeration unit of a finned tube heat exchanger for the fridge cabinet; PCM selection and, particularly, the effect of heat transfer enhancement at the condenser are discussed. Lab-scale tests were carried in the UK and field tests were carried out in Ghana in a collaboration project. In lab-scale tests, it is found that a condenser modification can decrease the transient power consumption by up to 26%. In contrast, the field-testing results show that the daily power consumption can be reduced only from 0.9 to 0.84 kWh. Additionally, field testing results show that the cabinet temperature of the PCM-enhanced refrigerator rose from 7°C to 11°C after a period of 5 hr power outage.

This study presents an experimental investigation into a novel incorporation of chilled ceiling with transparent membrane cover and phase-change material (PCM) to form a new type of PCM chilled ceiling panel. The membrane cover is infrared transparent to facilitate radiant cooling, but serves as a barrier of convection to avoid moisture condensation for applications in humid climate regions. As reliable electricity supply is still not accessible to millions of people, especially in sub-Saharan and South Asian countries where these countries also face the combined problems of high cooling demand and inadequate power supply, the use of solar energy would help to overcome these problems. To address such problems, the proposed PCM chilled ceiling can be applied along with a solar photovoltaic (PV) directly driven vapour-compression cooling system. Electricity generated by the photovoltaic (PV) panels drives the variable speed direct current (DC) compressor for cooling production, while excessive cooling is stored in the PCM packs for use at night. The variable speed compressor can adjust to match fluctuation in solar radiation and hence increases the utilization of solar energy. A small-scale experimental setup was prepared using a mini DC compressor refrigeration system. Integration of salt hydrate type PCM in chilled beam and chilled ceiling, respectively, and application of transparent membrane cover in chilled ceiling were tested to verify the proposed design.

Industrial processes and the building sector (e.g., for space and water heating) are responsible for the majority of the total energy consumed for heat. Although fossil fuels remain to dominate the heating sector, renewable heating technologies have been lately widely deployed. Thermochemical energy storage (TES) can be a promising advanced technology in addressing the mismatch between renewable energy supplies and the end-user's demand. In this paper, a novel Vermiculite-based Solar Thermochemical Heat Storage (VS-THS) system was proposed for domestic space heating applications, which could also overcome the intermittency challenges and realise long-term solar energy storage. A small-scale prototype was set up to evaluate the energy storage performance of the proposed system using a patented ChainStore panel to accommodate vermiculite-based composite. The unique design of the ChainStore arrangement offers great heat and mass transfer and good flexibility for system resizing in the case of varying the building energy demand. Due to the low regeneration temperature (63 °C) and high energy storage density (253.8 kWh/m3) of the vermiculite-based adsorbent impregnated with MgSO4 and CaCl2, it was chosen as the THS composite in the experiments. The experimental results showed that the proposed VS-THS is feasible for domestic space heating, with the highest space heating supply temperature of 37.6 °C, and the system COP in the reaction process is 7.9–10.4. In addition, the results also demonstrate that the composite of vermiculite impregnated with MgSO4 and CaCl2, with a good water adsorption performance. This proposed concept of VS-THS could be sized for different building applications.