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Cooling of the Li-ion battery module is a critical issue for electric vehicles in regard with the battery performance and lifetime, particularly at abused operating conditions. A water cooling system consisting of two novel cover plates with T-shape bifurcation structures and eight traditional cold plates was proposed and investigated for cooling of prismatic LiFePO4 battery modules. A computational fluid dynamics simulation model of the cooling system was established and validated by experimental data. The results show that a cold plate with four circular mini-channels flowing water can keep the maximum temperature of a single battery around 35 °C at 1 °C discharging rate and ambient temperature of 40 °C. Effect of the coolant flow rate is much less significant than the inlet coolant temperature on the cooling performance. Two sets of the proposed water cooling systems can significantly reduce the maximum temperature of a battery module consisting of 15 batteries. Moreover, great temperature distribution uniformity between different batteries can be achieved because the novel cover plate is able to distribute water evenly into each mini-channel of the cold plates. The cooling system can keep the maximum temperature of the module below 32.5 °C and the difference between the highest and lowest temperatures around 1.5 °C at abused operating conditions.

We present the design, fabrication, characterization, and field testing of transmissive active cooling for use in a point-focus spectrum-splitting hybrid concentrator photovoltaics/thermal (CPV/T) system. Seven parallel-path 100 μm thick microchannels are made using polydimethylsiloxane and attached to a CPV module containing a 6 × 6 array of 5.5 mm transmissive CPV cells on a sapphire substrate. Water is flowed through the microchannels to actively cool the CPV cells. The total transmittance of the CPV module reduces by 5.2% with the addition of the active cooling microchannels, relative to the module transmission with no microchannels. The peak cell temperature is measured as 69 °C with a thermal resistance of 9.35 K/W at 157 suns, well below the 110 °C maximum allowed temperature. A maximum flowrate of 16.7 g/s is achieved from a 13 psi pressure drop across the microchannels and manifold assembly. The flow characteristics within each microfluidic channel show maximum fluid velocity of 4.3 m/s (Re = 953) with a calculated convection coefficient of 1.7 × 104 W/m2 K (Nu = 5.36). The CPV/T module and cooling system performance was validated during week-long outdoor tests under varying solar conditions up to 250 suns using a 2.7 m2 parabolic dish collector mounted to a two-axis tracking system.

The hybrid system that integrates active cooling into phase change materials (PCMs)/expanded graphite (EG) shows great prospects for power battery thermal management. But because of the heavy weight, the system need to be optimized with a balance of the cooling capacity contributed by the active and passive cooling. This study develops an optimization method based on the response surface methodology (RSM) and a numerical heat transfer model to minimize the weight and volume of such a battery thermal management system. With the PCM thermo-physical property models incorporated, the method can optimize the PCM composition along with the active cooling structure – taking the contributions of both the active and passive cooling into account. We minimize the PCM mass of the system with this method, and analyze the effects of the PCM composition, the battery module layouts and the active cooling configuration on the thermal management performance. Then we present an optimal design for this hybrid thermal management system, which helps save the PCM mass by up to 94.1% and the volume by up to 55.6%. The thermal management performance of the design is verified with an experiment. The results show the maximum battery temperature in a 20-battery module during the 1.5C discharge is limited to 37.0 °C while the maximum temperature difference is limited to be smaller than 3 °C. Compared with the conventional liquid cooling system, the hybrid system is not only highly efficient, but lightweight, with simple structure and flexible to the batteries with arbitrary shapes.

Numerical simulations were performed to investigate a microchannel heat sink device as cooling option for a high concentration photovoltaic system. COMSOL Multiphysics 5.1 software is used to solve three-dimensional equations which consider conjugate heat transfer, viscous dissipations, and temperature-dependent-properties. This study investigates the integration of microchannels with complex geometric features on its inner walls into the solar cell structure, to enhance the heat transfer performance of a microchannel heat sink-based active cooling system. Inner sidewall mounted forward triangular ribs are considered in aligned and offset distributions along the microchannel walls. In addition, numerical analysis is developed for a conventional flat plate heat sink integrated to a high concentration photovoltaic system to stablish a baseline solar cell temperature. The numerical results show that a micro-channel heat sink device can control and keep in very low range the solar cell temperature ( 200. At Re = 400, the pumping power reaches 41% and 23% of the total power generated by a multi-junction solar cell in the aligned and offset rib distribution, respectively. The pumping power is greatly reduced while using smooth microchannel, because the maximum pumping power is only 9.5% of the solar cell power at Re = 400, however, the resulting solar cell temperature is slightly higher compared to microchannels with aligned and offset rib configurations. A microchannel heat sink provides a more effective cooling solution compared to a passive flat plate heat sink for a high concentration photovoltaic system. In addition, the possibility of direct integration of a microchannel heat sink into a solar cell structure as proposed in this study, represents an interesting option to feasibly increase thermal performance to a considerable level by maintaining the solar cell temperature in a very low range.

A single-phase thermosiphon is developed for cold collection and storage of radiative cooling. Compared to the conventional nocturnal radiative cooling systems that use an electric pump to drive the heat transfer fluid, the proposed single-phase thermosiphon uses the buoyancy force to drive heat transfer fluid. This solution does not require electricity, therefore improving the net gain of the radiative cooling system. A single-phase thermosiphon was built, which consists of a flat panel, a cold collection tank, a water return tube, and a water distribution tank. Considering that outdoor radiative cooling flux is constantly changing (i.e. uncontrollable), an indoor testing facility was developed to provide a controllable cooling flux (comparable to a radiative cooling flux of 100 W/m2) for the evaluation of thermosiphon performance. The testing apparatus is a chilled aluminum flat plate that has a controlled air gap separation relative to the flat panel surface of the thermosiphon to emulate radiative cooling. With an average of 105 W/m2 cooling flux, the 18 liters of water in the thermosiphon was cooled to an average temperature of 12.5 °C from an initial temperature of 22.2 °C in 2 h, with a cold collection efficiency of 96.8%. The results obtained have demonstrated the feasibility of using a single-phase thermosiphon for cold collection and storage of radiative cooling. Additionally, the effects of the thermosiphon operation conditions, such as tilt angle of the flat panel, initial water temperature, and cooling energy flux, on the performance have been experimentally investigated. Modular design of the single-phase thermosiphon gives flexibility for its scalability. A radiative cooling system with multiple thermosiphon modules is expected to play an important role in cooling buildings and power plant condensers.

Active cooling of thermoelectric generators (TEGs) is problematic since mechanical devices such as pumps and fans draw a high proportion of the limited power generated. Increasing the coolant fluid flow rate is typically a scenario of diminishing gains since the increased TEG power can be more than offset by the increase in power required for the fluid mover. Passive air cooling is an option, however the high air-side thermal resistance results in poor TEG power performance and low thermal efficiency. To address these issues, and others, a passive single phase liquid thermosyphon cooling system for use with TEGs has been designed, computationally simulated and experimentally tested. The novelty of the cooling system centres not only on the hot-side heat exchanger design, but also on the use of an open liquid reservoir as a dual-purposed heat store and air-side heat sink. This results in an effective source-to-sink heat exchange system that is entirely passive while providing effective cooling. This work describes the Simulation-Driven Design approach used to design the system for an example of a single TEG, experimental verification of the simulation results and TEG performance characteristics with the new cooling system.

The present study examines the use of a vertical double-pipe single-flow heat exchanger as part of an active air cooling system for a 150 W LED street light. The air is circulated inside the lamppost by an internal fan to form a closed-loop system. The heat is dissipated to the surrounding air by natural convection, reaching Rayleigh numbers up to Ra = 6.5 × 1010. Experiments with a 5 m high prototype were conducted, and the data were used to validate the numerical model. The experimental results show that the LED excess temperature can be lowered to about 42 °C. A two-dimensional axisymmetric numerical simulation was performed to study the influence of various parameters, including pipe length, material conductivity, flow direction, pipe diameter ratio, and mass flow rate, on the heat transfer rate. The findings show that the additional heat loss created by extending the lamppost largely depends on the flow rate. When extending the lamppost from 3 to 5 m at a high mass flow rate of 0.014 kg/s, the heat loss increases by 34.1% to 120.2 W. The numerical study was also used to visualize the hydrodynamic boundary layers on the surface of the lamppost and the temperature contours in and outside of the heat exchanger.

Hybrid concentrator photovoltaic-thermal systems can cogenerate electricity and heat by beam-splitting incoming concentrated light onto photovoltaic cells and a thermal receiver to increase total conversion efficiency and potentially reduce system cost. To demonstrate this, we have designed and prototyped a transmissive spectrum-splitting concentrator photovoltaic module that maximizes solar energy conversion by utilizing the entire solar spectrum. Visible light is collected using infrared-transmissive triple-junction photovoltaic cells to achieve an in-band module efficiency of 43.3% for light of wavelength λ 873 nm is transmitted through for collection by a thermal receiver. During testing on a dual-axis tracked parabolic concentrator dish at up to 166 suns, cell temperatures were maintained at 119 °C or below via a novel active cooling method. This cooling system strictly flows silicone oil directly across both sides of the cells, without inhibiting optical transmission, as verified through experimentation and simulation. The module was validated outdoors for 572 sun·hrs, and achieved a maximum thermal receiver temperature of 180 °C. 86.1% of incident solar power is collected at 166 suns average concentration collectively among the electrical, cooling, and thermal receiver subsystems. The remaining 13.9% is lost to mirror reflectivity, dish shadowing, receiver reflection, and thermal losses. The ability to directly cool the cells with an inert silicone oil offers the potential for reduced system cost relative to previous transmissive hybrid concentrator photovoltaic-thermal systems, including microfluidic-cooled designs. This solar cogeneration capability is valuable in a wide range of commercial and industrial applications.

This study investigates a new system which utilizes a solar driven adsorption chiller to provide natural cooling of a one-story building with domed roof, theoretically. The domed roof provides natural ventilation, and the ambient air flowing into the building is cooled in a cooling channel with the assistance of the adsorption chiller. The influence of geometric parameters such as the size of the inlet and outlet vent, and the depth of the cooling channel on air change per hour (ACH) is studied. In addition, the room temperature is evaluated for different values of room cooling demand and ACH, under different ambient conditions. The system’s ability to provide thermal comfort in the room is also investigated. The results show that ACH can be controlled by changing the size of the inlet air vent. It is also found that adaptive thermal comfort condition (ATCS) is achieved under larger cooling demand values when ACH goes up. Furthermore, use of three cooling plates in the channel instead of two plates increases the maximum cooling demand for which thermal comfort is achieved, according to ATCS, from 775 W to 1295 W. Moreover, application of the proposed system for cooling of a building in Bandar Abbas consumes 45% less electric energy in comparison with a split air conditioner of the same capacity.

The use of photovoltaic thermal (PVT) technologies enables improvement in the electrical efficiency of a photovoltaic (PV) module by reducing the temperature of the PV module via active waste heat removal. In current PVT systems, the removed heat is mainly used for specific applications, such as water and/or room heating, but their need is intermittent and seasonal. For a more efficient and versatile use of the removed waste heat, we propose a new architecture where the PV module is integrated with a dual-functional electrolyzer that removes the waste heat by active cooling and produces hydrogen via electrolysis. The excess heat from the PV cell is utilized to enhance the reaction kinetics of the electrolysis process (due to an increase in temperature) inside an electrolyzer, which is located below the PV module. In this paper, we used finite-element analysis (FEA) simulations to optimize the geometry and operating conditions of an electrolyzer to maximize overall energetic efficiency and hydrogen production. To evaluate the practical feasibility of the approach, we performed a comprehensive energy analysis of the PVTE system using data from Phoenix, AZ. The energetic efficiency of the proposed PVTE system was calculated to be 56–59%, which is comparable to those of current PVT systems. Additionally, the integration of the electrolyzer with the PV module led to an almost 2.5-fold increase in hydrogen production compared to a stand-alone electrolyzer operated at ambient temperature. The analyzed hybrid approach potentially represents a viable and useful alternative for utilization of waste heat energy from PV cells. This approach may further increase the use of photovoltaic technologies as a renewable energy source.

The present paper analyzes the feasibility of an exhaust gas driven jet-ejector cooling system for charge air cooling of turbocharged gasoline engines in addition to the conventional charge air cooler to increase the engine efficiency. Thereto, steady-state experiments of a jet-ejector cooling system and an exhaust gas heat exchanger prototype working with the refrigerant R134a are used to analyze the operation and control of the compound system and determine feasible cooling capacities, charge air temperatures, thermal COP th and hydraulic COP h . Moreover, the cooling system is rated regarding its power densities and engine backpressure. The exhaust gas waste heat recovery, system power densities, and engine backpressure are acceptable. However, the hydraulic COP h and the amount of reject heat need to be improved, necessitating for instance a multi-staging of the jet-ejection.

This paper presents new metrics to measure the effect of thermal mass on the energy required to heat and cool buildings. Previous studies have been flawed as they have not considered the interaction between intermittent occupancy and thermal mass, which has a significant impact on overall energy use. However, existing parameters do not adequately capture these effects, so the new metrics developed in this paper are used to analyse the impact of thermal mass in hot climates with active cooling, and cold climates with active heating. The results agree with existing literature that high thermal mass structures are likely to be effective in hot climates; however, in cold climates the drawbacks of high thermal mass likely outweigh the advantages, and high thermal mass can cause an increase in energy use. This finding has implications for the design of buildings in cold climates, and contradicts the commonly-held assumption that high thermal mass is correlated with low energy use. The new metrics (transient energy ratio and effective U-value) provide a generalisable method to quantify these effects. They are further used here to analyse the dynamic performance of heavily insulated buildings and show that high thermal mass often leads to higher energy use in cold climates.

A case is made that while it is important to mitigate dissipative losses associated with heat dissipation and mechanical/electrical resistance for engineering efficiency gain, the “architect” of energy efficiency is the conception of best heat extraction frameworks—which determine the realm of possible efficiency. This precept is applied to building energy efficiency here. Following a proposed process assumption-based design method, which was used for determining the required thermal qualities of building thermal autonomy, this paper continues this line of investigation and applies heat extraction approach investigating the extent of building partial homeostasis and the possibility of full homeostasis by using cooling tower in one summer in seven selected U.S. cities. Cooling tower heat extraction is applied parametrically to hydronically activated radiant-surfaces model-buildings. Instead of sizing equipment as a function of design peak hourly temperature as it is done in heat balance design-approach of selecting HVAC equipment, it is shown that the conditions of using cooling tower depend on both “design-peak” daily-mean temperature and the distribution of diurnal range in hourly temperature (i.e., diurnal temperature amplitude). Our study indicates that homeostatic building with natural cooling (by cooling tower alone) is possible only in locations of special meso-scale climatic condition such as Sacramento, CA. In other locations the use of cooling tower alone can only achieve homeostasis partially.

We present a systematic study of a coupled geothermal cooling system with an earth-to-air heat exchanger and a solar collector enhanced solar chimney. Experiments were conducted with an existing test facility in summer to evaluate the performance of the system, in terms of passive cooling capability, active cooling capability, and soil thermal capability. Correspondingly, three different tests were carried out in 43 days in a sequence, from a passive cooling mode to an active cooling mode, and then back to a passive cooling mode. The results show that the coupled geothermal system is feasible to provide cooling to the facility in natural operation mode free without using any electricity. The solar collector enhanced solar chimney can provide more airflow to the system during the daytime with a stronger solar intensity. The thermal sensation analysis based on predicted mean vote and predicted percent of dissatisfied people indicates that the indoor air condition under the natural airflow stage was more acceptable in terms of thermal comfort than that of the forced airflow stage. The cooling capacity of the coupled system drops quickly after the one week forced airflow test due to the underground soil temperature increase. It takes the soil over two weeks to fully recover from the thermal saturation after the forced air test. In addition, the underground soil temperature test results indicate that the underground heat dissipation in the horizontal level was greater than that in the vertical level. The findings suggest that a minimum level of control on the system and consideration on soil saturation is needed to further improve the overall performance.

Latent heat thermal energy storage (LHTES) integrated active free cooling stores night time cold and serves as heat sink for cooling when demand rises. Passive buildings, albeit their advantages in limiting heat loss during winter time, are often paired with excessive internal overheating in summer, as shown in the first part of this study. Under the climate condition in Stockholm, LHTES systems may provide solutions for sustainable cooling with use of renewable cooling sources. This study presents a multi-objective optimization on system cost and cooling supply for various LHTES configurations followed with a sensitivity analysis on phase change material cost and energy price. Results indicate that optimized LHTES may meet cooling needs while retaining economic viability. However, LHTES based cooling systems may require substantially higher electricity demand than conventional air conditioning unit for applications where high cooling thermal power rate is to be met, a tradeoff to indoor comfort level needs to be considered to reach the concept of sustainable free cooling. We here provide a novel techno-economic feasibility study of active free cooling LHTES in Stockholm as well as new insights to cost, comfort level and energy requirement with use of multi-objective optimization algorithm.

A novel chiller with open-cycle rotary desiccant cooling has been investigated experimentally. The technologies of two-stage dehumidification and regenerative evaporative cooling have been integrated together in this chiller. The objective of this study is to extend the ability for handling sensible heat of the rotary desiccant cooling system. Based on the experimental results, it is found that the novel chiller is a good choice for space cooling using low-grade heat source. The temperature of the supply chilled water from this unit is around 15–20 °C. The thermal coefficient of performance is about 0.3–0.6 in terms of the chilled water production. Furthermore, the rotary desiccant cooling system, which produces both dry air and chilled water, is proved to be superior to the conventional rotary desiccant cooling system in handling the sensible heat. Especially, under humid and high humid conditions, the effective cooling capacity of the novel system is still at a favorable level. The specific thermal coefficient of performance of the novel rotary desiccant cooling system is around 0.8–0.9 considering the production of both chilled water and dry air.

Thermal designers of data centers and server manufacturers are showing a greater concern regarding the cooling of the new generation data centers, which consume considerably more electricity and dissipate much more waste heat, a situation that is creating a re-thinking about the most effective cooling systems for the future beyond conventional air cooling of the chips/servers. A potential significantly better solution is to make use of on-chip two-phase cooling, which, besides improving the cooling performance at the chip level, also adds the capability to reuse the waste heat in a convenient manner, since higher evaporating and condensing temperatures of the two-phase cooling system (from 60-95°C) are possible with such a new “green” cooling technology. In the present project, two such two-phase cooling cycles using micro-evaporation technology were experimentally evaluated with specific attention being paid to (i) controllability of the two-phase cooling system, (ii) energy consumption and (iii) overall exergetic efficiency. The controllers were evaluated by tracking and disturbance rejection tests, which were shown to be efficient and effective. The average temperatures of the chips were maintained below the limit of 85°C for all tests evaluated in steady state and transient conditions. In general, simple SISO strategies were sufficient to attain the requirements of control. Regarding energy and exergy analyses, the experimental results showed that both systems can be thermodynamically improved since only about 10% of the exergy supplied is in fact recovered in the condenser in the present setup.

Phase change materials (PCMs) are increasingly being used for thermal energy storage in buildings and industry to produce energy savings and reduce carbon dioxide emissions. PCM slurries are also being investigated for active thermal energy storage or as alternatives to conventional single phase fluids because they are pumpable and have advanced heat transport performance with phase change. The present study investigates several types of phase change materials for the preparation of PCM slurries which have potential for cooling applications. The thermophysical properties of paraffin in water emulsions, such as latent heat of fusion, melting and freezing temperature ranges, viscosity and the effect of surfactants, have been tested using appropriate experimental techniques. It has been identified that the use of small quantities of higher melting temperature paraffin and surfactants in the emulsion can reduce the effect of supercooling and increase the useful heat of fusion. However there are negative impacts on viscosity which should be considered in heat transport applications.

The electrical efficiency of photovoltaic (PV) cell is adversely affected by the significant increase of cell operating temperature during absorption of solar radiation. A hybrid photovoltaic/thermal (PV/T) solar system was designed, fabricated and experimentally investigated in this work. To actively cool the PV cells, a parallel array of ducts with inlet/outlet manifold designed for uniform airflow distribution was attached to the back of the PV panel. Experiments were performed with and without active cooling. A linear trend between the efficiency and temperature was found. Without active cooling, the temperature of the module was high and solar cells can only achieve an efficiency of 8–9%. However, when the module was operated under active cooling condition, the temperature dropped significantly leading to an increase in efficiency of solar cells to between 12% and 14%. A heat transfer simulation model was developed to compare to the actual temperature profile of PV module and good agreement between the simulation and experimental results is obtained.

This article experimentally investigates the thermal performances of a heat pipe with phase change material for electronic cooling. The adiabatic section of heat pipe is covered by a storage container with phase change material (PCM), which can store and release thermal energy depending upon the heating powers of evaporator and fan speeds of condenser. Experimental investigations are conducted to obtain the system temperature distributions from the charge, discharge and simultaneous charge/discharge performance tests. The parameters in this study include three kinds of PCMs, different filling PCM volumes, fan speeds, and heating powers in the PCM cooling module. The cooling module with tricosane as PCM can save 46% of the fan power consumption compared with the traditional heat pipe.

International audience; This article presents the concepts of an air-source Heat Pump for Simultaneous heating and cooling (HPS) designed for hotels and smaller residential, commercial and office buildings in which simultaneous needs in heating and cooling are frequent. The main advantage of the HPS is to carry out simultaneously space heating and space cooling with the same energy input. Ambient air is used as a balancing source to run a heating or a cooling mode. The second advantage is that, during winter, energy recovered by the subcooling of the refrigerant is stored at first in a water tank and used subsequently as a cold source at the water evaporator to improve the average performance and to carry out defrosting of the air evaporator using a two-phase thermosiphon. Unlike conventional air-source heat pumps, defrosting is carried out without stopping the heat production. A R407C HPS prototype was built and tested. Its performance on defined operating conditions corresponds to the data given by the selection software of the compressor manufacturer. The operation of the high pressure control system, the transitions between heating, cooling and simultaneous modes and the defrosting sequence were validated experimentally and are presented in the second part of this article [1].

Thermal adaptation composite material is a kind of composite material with required thermal conductivity or coefficient of thermal expansion through the selection and design of its components. A kind of thermal adaptation composite material that has excellent thermal conductivity and heat storage capacity is prepared by absorbing paraffin into expanded graphite. An electronic cooling experimental system based on the thermal adaptation composite material is built. The temperature variations of the simulative chip are respectively measured in this system and the traditional cooling system to investigate the effect of the thermal adaptation composite material on electronic cooling. At the same time, the impacts of composite material dosage and combining active cooling manner on the performance of electronic cooling are also studied. The experimental results show that the apparent heat transfer coefficients of the electronic cooling experimental system are 1.25–1.30 times higher than those of the traditional cooling system. It also can be found that the dosage of composite material has positive impact on the performance of electronic cooling. By combining active cooling manner, it can compensate the deficiency of cooling capacity in phase change thermal control.

The suitability of the low-temperature cycle of a vapour power-plant based on an organic fluid for cooling technical equipment that requires cooling during operation, e.g. power transformers, has been presented. The stream of the intermediate fluid, usually oil, which removes heat from the equipment being cooled is the upper heat reservoir of a power plant based on the Clausius–Rankine cycle. The byproduct of the operation of such an installation is electricity, which can be used to drive the fan cooling tower of the power plant. The assumed working parameters of the cycle, and mainly the criteria for selecting the organic working-fluid, whose properties have a major impact on the operating effectiveness of the solution, are proposed.