Recently, multi-channel flat heat pipes have been developed to improve the heat recovery from flat surfaces, such as solar panels and batteries. In this paper, the thermal performance of a multi-channel flat heat pipe is experimentally investigated and analytically predicted. The multi-channel heat pipe studied transmits heat from silicone flat heaters to a water flow circulating inside a cooling manifold. The manifold heat sink is a flat aluminium surface comprising channels in which water recovers thermal energy by forced convection. The impact of the water flow rate on the working temperature of the heat pipe is investigated. To predict the performance and working temperature of the multi-channel flat heat pipe, a theoretical model has been developed. The thermal model considers the two-phase heat transfer in a multi-channel heat pipe geometry. It is shown that the heat pipe working temperature decreases with the water flow rate as a result of a reduced forced convection resistance of the manifold. Finally, the analytical multi-channel flat heat pipe model developed is compared with experimental data. It is shown that the thermal model, considering both cooling manifold and the multi-channel heat pipe geometry, is able to predict the heat pipe working temperature evolution within 7%.

The interest in the energy efficiency of buildings and the integration of new technologies to reduce the heating and cooling loads through the building envelope is not new. The European Union (EU) is committed to decarbonising its building stock as almost 50% of the Union’s final energy consumption is for heating and cooling, of which 80% is used in buildings. The article analysis the performance of a PV/T system (with a heat mat) for the heat demand of a low-energy two-zone, single-family building during the year. For this purpose, a building model was built in TRNSYS using Multizone building model and TRNbuild in two variants of heating (internal - as reference and external). Then the building model was connected to a mechanical ventilation system providing heating during winter for which the heat source is a PV/T system to demonstrate if the heating requirements for the household can be provided during different seasons of the year. Additionally, it was indicated how much energy consumption reduction can be obtained in comparison to the case when a heating unit is used.

Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming. In order to reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their capacity to transform thermal energy directly into electric power through the Seebeck effect. Due to the unique advantages they present, thermoelectric systems have emerged during the last decade as a promising alternative among other technologies for green power production. In this regard, thermoelectric device output prediction is important both for determining the future use of this new technology and for specifying the key design parameters of thermoelectric generators and systems. Moreover, TEGs are environmentally safe, work quietly as they do not include mechanical mechanisms or rotating elements and can be manufactured on a broad variety of substrates such as silicon, polymers and ceramics. In addition, TEGs are position-independent, have a long working life and are ideal for bulk and compact applications. Furthermore, Thermoelectric generators have been found as a viable solution for direct generation of electricity from waste heat in industrial processes. This paper presents in-depth analysis of TEGs, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect, the Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types. Moreover, performance simulation examples such as COMSOL Multiphysics and ANSYS-Computational Fluid Dynamics are investigated.

Energy consumption in the housing sector, is significantly high and continues to escalate. Urbanisation due to population growth and migration from rural areas to cities are two main reasons for this rising demand. With the uncertainty in the energy market and the increasing awareness of the impact of fossil fuels on the environment, research work in efficient building design has gained momentum. Energy conservation guidelines in many countries have become mandatory. Howerver, more emphasis has been given to commercial, institutional, governmental and industrial buildings, which commonly employ more efficient HVAC systems than those deployed in houses. Thus, the push towards energy conservation in the residential sector is less noticeable. This is further compounded with the absence of will power to enforce the same energy conservation rules as the case with other sectors. In this paper five passive cooling and heating strategies have been reviewed (passive building design, night ventilation, nocturnal cooling, PCM (Phase Change Material) and IEC (Indirect Evaporative Cooling), solar thermal energy). The aim is to evaluate how to implement them better in a cost-effective way in existing and new houses. The literature review confirmed the need for further investigation of energy efficient HVAC systems with passives strategies solutions for contemporary residential dwellings is required to make a meaningful impact on the energy map of this sector. Also, the viability of an easy to deploy and configure HVAC system for retrofit and new applications for more benefits of these passive strategies either individually or in a hybrid configuration needs to be explored.

In this work, computational modelling and performance assessment of several different types of variable thermoelectric legs have been performed under steady-state conditions and the results reviewed. The study conducted has covered geometries, not previously analysed in the literature, such as Cone-leg and Diamond-leg, based on the corresponding thermoelectric generator leg shape structure. According to the findings, it has been demonstrated that the inclusion of a variable cross-section can have an impact on the efficiency of a thermoelectric generator. It has been concluded that the Diamond configuration generated a slightly larger voltage difference than the conventional Rectangular geometry. In addition, for two cases, Rectangular and Diamond configurations, the voltage generated by a TEG module consisting of 128 pairs of legs was analysed. As thermal stress analysis is an important factor in the selection of TEG leg geometries, it was observed based on simulations that the newly implemented Diamond-leg geometry encountered lower thermal stresses than the traditional Rectangular model, while the Cone-shape may fail structurally before the other TEG models. The proposed methodology, taking into account the results of the simulation carried out, provides guidance for the development of thermoelectric modules with different forms of variable leg geometry.

Lithium-ion batteries are widely used in high power applications and, with more industries focusing on the electrification of their processes, the need for an effective battery thermal management system is growing. The use of a thermal management system serves multiple purposes such as safeguarding the battery from catastrophic thermal runaway and increasing the lifespan of the battery pack. In the present paper, the thermal management of a sixteen-cell battery module, by two different configurations of a heat pipe based thermal management system, is investigated experimentally. In the first configuration, the module is fixed on top of a single horizontal ‘heat mat’. The second configuration consists of the module sandwiched between two vertical heat mats. The comparison of the cooling performances of these two configurations showed their ability to efficiently absorb the heat generated by the cells and maintain their temperatures close to the ideal operating range. During representative cycles of operation, the maximum cell temperature was kept below 28.5 °C and 24.5 °C for the horizontal and vertical heat mat configurations respectively. The cell temperature uniformity across the module stays in a +/-1 °C range, which will reduce cell voltage imbalance, loss of useable capacity and non-uniform ageing. The maximum temperature difference across the height of the cells was 6 °C for the horizontal configuration and 2 °C for the vertical one. The second part of this paper compares the heat removed in both configurations when loaded with a quasi-steady-state heat generation. The third study uses a faster (6C) charge rate during a representative cycle and shows that the maximum temperature stays below 30 °C and 28 °C for the horizontal and vertical configurations respectively.

Analyses will be conducted to indicate the energy performance of a photovoltaic-thermal (PV/T) system. In this regard, a simulation tool using the transient system simulation (TRNSYS) software will be developed to investigate if the system can be used to provide electrical and thermal energy to a household located in London, UK. Based on this, it will be indicated if the modelled system is capable of providing the required demand and how the energy output from the system can be delivered to thermal and electrical storage components. Having indicated that, it will be demonstrated how by utilising the developed model, the energy output from the system can be improved. Furthermore, it will be discovered how different thermal energy storage systems can help to store or dissipate the absorbed excessive heat from the system. The analyses will be conducted on the most optimal short- and long-term thermal storage systems and during warm seasons of the year.

This article discusses the functionalities and developments of different types of solar panels. It explains the latest technological advances in this field, especially in the context of different types of solar panels, namely, photovoltaic (also known as PV), thermal collectors, photovoltaic-thermal (known as PV/T) panels and concentrating solar panels. Specifically, the paper examines how each of the technologies analysed operates to produce heat and electrical power, how to improve the energy efficiency and which technology provides the best system efficiencies and fastest return on investment. Finally, it also assesses the extent to which the exploitation of renewable energy sources and incentives to achieve energy efficiency is supported by the European regulatory framework and policies.

The achievement of European climate energy objectives which are contained in the European Union's (EU) “20–20–20″ targets and in the European Commission's (EC) Energy Roadmap 2050 is possible, among other things, through the use of energy storage technologies. The use of thermal energy storage (TES) in the energy system allows to conserving energy, increase the overall efficiency of the systems by eliminating differences between supply and demand for energy. The article presents different methods of thermal energy storage including sensible heat storage, latent heat storage and thermochemical energy storage, focusing mainly on phase change materials (PCMs) as a form of suitable solution for energy utilisation to fill the gap between demand and supply to improve the energy efficiency of a system. PCMs allow the storage of latent thermal energy during phase change at almost stable temperature. The article presents a classification of PCMs according to their chemical nature as organic, inorganic and eutectic and by the phase transition with their advantages and disadvantages. In addition, different methods of improving the effectiveness of the PCM materials such as employing cascaded latent heat thermal energy storage system, encapsulation of PCMs and shape-stabilisation are presented in the paper. Furthermore, the use of PCM materials in buildings, power generation, food industry and automotive applications are presented and the modelling tools for analysing the functionality of PCMs materials are compared and classified.

In this paper, a standalone photovoltaics-thermal solar panel is modelled using the TRNSYS simulation engine. Based on this, it was explored how such a system can be comprised of thermal and electrical storage components to provide electricity and hot water for a dwelling in a warm location in Europe. Furthermore, it was investigated how, by cooling the temperature of the solar cells, the electrical power output and efficiency of the panel was improved. The performance of the system was also studied, and the amount that the solar panel was able to convert the solar energy into electricity was investigated. Through this, we discovered that when the temperature of the panel was reduced, on average, by 20%, the electrical power output increased by nearly 12%. Moreover, it was demonstrated that the modelled system can provide hot water under different solar radiation conditions and during all seasons of the year.

The development of waste heat recovery technologies has surged as a result of climate change initiatives, which require energy intensive industries to curb their emissions and lower energy consumption. Installing heat pipe heat exchangers has proven to be a reliable and effective method of recovering waste heat due to their passive operation, superconductive properties and small footprint. This paper highlights the application of a vertical multi-pass heat pipe heat exchanger to a lab scale ceramic kiln system used to transfer heat from the kiln exhaust to water. The innovative heat pipe heat exchanger exists as a novel variable unit able to recover heat energy for a range of inlet temperatures and flow rates. The installed unit has shown a heat recovery rate of up to 63 kW. A range of exhaust gas temperatures from 135 to 270 degrees C were trialled at varying heat source and sink mass flow rates. The results of the experiments as well as simulation results using a model built using the software TRNSYS are given. The investigation has confirmed that the TRNSYS simulation results agree well with the experimental results. Additionally, return on investment analysis predicted 33 months payback for a theoretical full-scale unit preheating water for space heating. (C) 2020 Elsevier Ltd. All rights reserved.

In this paper, the performance of a heat pipe based thermal management technique for batteries has been investigated experimentally. In this regard, a test rig was developed and used to demonstrate the effectiveness of flat heat pipe (heat mat) technology at controlling and maintaining the temperature of a prototype battery module, which consisted of sixteen prismatic lithium-titanate (LTO) cells. Test results were obtained which proved the ability of the technology to keep the battery cells at an optimal temperature, during cycling representative of real-world operation, from either a cold or hot start. The heat mat was shown to efficiently absorb the heat generated by the cells and transfer it effectively to an external cooling medium of either water or refrigerant. In conclusion, it was demonstrated that the maximum cell temperature is significantly reduced and the overall temperature uniformity of the module is greatly improved, when compared to a module with no thermal management. The maximum cell temperature was kept below 28 °C and the module temperature uniformity was maintained at +/−1 °C. By using test cycles that generated a quasi-steady-state heat load from the cells, it was shown that approximately 60% of the heat generated by the cells was removed by the heat mat. The results obtained from this work demonstrate that heat mat technology can improve battery performance and longevity by reducing the degradation and ageing process and cell imbalances, that result from high cell temperatures and module/pack-level temperature non-uniformity.

The work presented in the paper provides a detailed TRaNsient System Simulation (TRNSYS) model that simulates the performance of a solar photovoltaic – thermal (PV/T) collector and examines its potential contribution for household heating applications in the UK. Based on this, a system is modelled to simulate the hot water demand of a house through connecting the solar – thermal panel with a thermal storage tank, a pump and a controller. The results obtained from the simulation indicated by how much the solar panel is able to convert solar energy into electrical power and heat over different seasons of the year and provide the hot water needs of the household. The model was validated based on the experimental configurations of a hybrid heat pipe based solar PV/T module and through applying cooling cycles, the thermal and electrical outputs and efficiencies of the system were indicated. Through this, it is investigated that the temperature of the solar panel can be reduced on average by almost 25%, which subsequently, will result in an increase of the electrical power output by nearly 15%. The simulation results also assisted in investigating and analysing aspects such as the effectiveness and efficiency of the panel over different times of the year and helped to optimise the performance of the system. For instance, it is simulated that the system can provide hot water for the household throughout all seasons of the year and under different solar radiation conditions. However, it is discovered that in order for the system to meet the required output demand, input from an auxiliary power unit may always be necessary.

In this review, the operation and functionality of batteries used in industrial applications will be investigated. It will be discussed how and why batteries degrade and lose efficiency because of improper thermal management and based on that it will be explained what methods and techniques can be applied to reduce this impact. Through this, it will be explained how heat management methods could be used to thermally control batteries. In addition to this, it will be indicated what technologies can be employed to manage thermal boundaries of batteries. A comprehensive review of the current state of the art technologies currently used will be followed by that which will include how these technologies can be applied as thermal management systems for batteries.

Industrial waste heat is the energy that is generated in industrial processes which is not put into any practical use and is lost, wasted and dumped into the environment. Recovering the waste heat can be conducted through various waste heat recovery technologies to provide valuable energy sources and reduce the overall energy consumption. In this paper, a comprehensive review is made of waste heat recovery methodologies and state of the art technologies used for industrial processes. By considering the heat recovery opportunities for energy optimisation in the steel and iron, food, and ceramic industries, a revision of the current practices and procedures is assessed. The research is conducted on the operation and performance of the commonly used technologies such as recuperators, regenerators, including furnace regenerators and rotary regenerators or heat wheels, passive air preheaters, regenerative and recuperative burners, plate heat exchangers and economisers and units such as waste heat boilers and run around coil (RAC). Techniques are considered such as direct contact condensation recovery, indirect contact condensation recovery, transport membrane condensation and the use of units such as heat pumps, heat recovery steam generators (HRSGs), heat pipe systems, Organic Rankine cycles, including the Kalina cycle, that recover and exchange waste heat with potential energy content. Furthermore, the uses of new emerging technologies for direct heat to power conversion such as thermoelectric, piezoelectric, thermionic, and thermo photo voltaic (TPV) power generation techniques are also explored and reviewed. In this regard, the functionality of all technologies and usage of each technique with respect to their advantages and disadvantages is evaluated and described.