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This paper systematically describes the technical principles, evaluation indicators, system forms and research progress of air-side evaporative cooling air conditioning systems, water-side evaporative cooling air conditioning systems and freon-side evaporative cold coagulation heat air conditioning systems of Data center. In order to reduce the energy consumption of the refrigeration and air-conditioning system in the Data center, the application conditions and scenarios of the different forms of evaporative cooling air-conditioning systems should be considered comprehensively. Therefore, it is very important that the renewable energy-dry air can be used to the greatest extent. These efforts would contribute to China's 2030 "Carbon Peak" and 2060 "Carbon Neutral."

The radiant systems consume less energy and provide better thermal comfort as compared to the conventional system, but the main drawback of radiant technology is inability to cater the latent load and condensation. This problem has engaged researchers to push their emphasis on Personalized Conditioning System (PCS). It forms a micro-climate region near the occupant. This study is aimed at PCS combined with a radiant conditioning system, which evaluates the performance of the PCS and compares it with different radiant cooling systems. A radiant cubicle was used to investigate the performance of the PCS for both heating & cooling modes. For heating mode, the Standard Effective Temperature (SET) was calculated with the help of thermal comfort surveys which were in a range of 23.4°C to 27.3°C. For cooling mode, four different cases compared the performance of the system which are: Conventional Air Conditioning System (CACS), Radiant Cooled Ceiling System (RCCS), Personalized Radiant Conditioning System (PRCS), and both PRCS-RCCS coupled. It was observed that PRCS alone reaches the thermal comfort criteria with low energy consumption. The energy-saving of RCCS-PRCS was achieved 38% when compared with CACS. It can be concluded that PRCS is a new step in the field of thermal comfort.

Energy conservation is a practice of reducing the energy used, which may be achieved by efficient use of energy. The existing old buildings generally consume more energy than the new buildings because of their unavoidable stagnations in physical performances. Distribution side load management of buildings play a vital role in the field of energy management. And 30% of this distribution side loads are Heating, Ventilation and Air Conditioning (HVAC) loads. So the accurate estimation of heating load (HL) and cooling load (CL) of HVAC system in a building is very much important. It has been studied that the building design parameters optimization approach alone can provide up to 62.1% electrical energy consumption reduction compared to buildings that are not designed for efficient energy usage. Recent research has demonstrated that a combination of existing HVAC technologies can offer effective solutions for energy conservation and thermal comfort. So in this study various energy saving strategies for HVAC systems are investigated and different measures on further energy and cost savings in buildings are discussed.

There are prototypes of social housing massively built in contrasting climatic conditions, generating thermal comfort needs that are difficult to satisfy by the users themselves. Variation of indoor air volume in living spaces where the use of air conditioning and natural ventilation strategies provides elements to improve thermal comfort conditions. This research shows the thermal performance located in a representative social housing according to Mexico's National Housing Commission. Operative temperature results from a benchmark case were compared to six Virtual Evaluation Models, using the Dynamic Thermal Simulation tool Design Builder® from the perspective of probability. The main objective was to determine the minimum use of active systems with different indoor air volumes and improve comfort conditions to promote sustainable living in social housing. The analysis was conducted under an adaptive comfort range according to three different climate conditions in Mexico adopting a Numerical Theoretical Method. The main findings can be divided into two parts: a) the impact of the indoor air volume on thermal performance was evidenced in a proportion of time in three representative climates of the central region of Mexico, and b) no relationship was found between indoor air volume and thermal comfort in sub-humid cold climate; in sub-humid temperate climate, the same number of comfort hours was found in two different models, and in sub-humid warm climate, an inversely proportional relationship was found between indoor air volume and the comfort hours. This findings implies a greater knowledge relative to what we know about sub-humid cold, temperate and warm climates.

Global warming has become one of the major environmental problems facing mankind in the 21st century. The existing refrigeration technology of buildings, like air conditioning, consumes a lot of energy. Passive daytime radiative cooling technology works without consuming energy, nor emitting carbon dioxide and other greenhouse gases. This review summarizes the development of daytime passive radiative cooling technology from the basic principles, structure and materials of radiative coolers; analyses and evaluates the various existing radiative coolers. The core of radiative cooling lies in the combination of multi-scale micro/nano structures. The cooler reflects sunlight thus preventing the building from being heated up; while allows the building to radiate its own heat out thus being cooled down; meanwhile maintains the temperature difference by the heat insulation effect of the porous structure in the film. The common challenges and potential solutions for the commercialization of radiative cooling technologies are analyzed, which may promote the applications of the technology in the near future.

This paper takes solar-powered organic Rankine-vapor compression air conditioning as the research object, and uses thermodynamic simulation methods to study the type of working fluid, system design and influencing factors. The results show that the temperature and condensation temperature of the working fluid have an important effect on the performance of the system. The cooling power per unit area collector and the total efficiency of the system first increase and then decrease with the temperature of the working fluid, and decrease with the increase of the condensation temperature. Through performance comparison, it is found that R123 is a more suitable working fluid, the thermodynamic feasibility of a solar-powered organic Rankine-vapor compression air-conditioning system was demonstrated.

According to the few researches on Nearly zero energy residential buildings (NZERB) in hot-summer and cold-winter zone, although it could reduce the cooling load of buildings due to its high thermal insulation and air tightness, it still needed for certain cooling in summer. This paper studied indoor environment of NZERB under three kinds of air-conditioners (split-type air-conditioner, multi-line air-conditioner and ceiling radiant air-conditioner). Firstly, a simulation model of NZERB was established based on Nanjing, a typical city in hot-summer and cold-winter zone. Secondly, variation of indoor air temperature and building load characteristics with outdoor air temperature were studied. Thirdly, indoor environment and energy consumption under three selected conventional air-conditioners in summer were simulated. Finally, the discussion was given, and an air-conditioner combining with convective and radiant cooling were proposed. The results indicated that the air-conditioner needed to be turned on in NZERB in hot-summer and cold-winter zone due to the room air temperature in off-air condition ranged from 32 °C to 36 °C, which was higher than designed indoor environment temperature in summer, but the indoor environment of NZERB under three selected conventional air-conditioners could not meet the requirements of energy saving and comfort at the same time, and a proposed convective-radiant air-conditioner could be fast, stable, and energy saving. The findings can provide a reference for conducting active technology in NZERB.

Increasing air conditioner use for cooling indoor spaces has the potential to be a primary driver of global greenhouse gas emissions. Moving indoor air with residential fans can raise the temperature threshold at which air conditioning needs to be turned on to maintain the thermal comfort of building occupants. We investigate whether fans can be used to reduce air conditioner use and associated greenhouse gas emissions.We developed an integrated framework, featuring a dynamic adaptive thermal comfort model with a geographical information system-based spatially gridded map of Australia, further complemented with census data. We assessed the change in energy use and associated greenhouse gas emissions for five scenarios of air conditioner and fan use: an air conditioner-only scenario (no fans); and four fan-first scenarios with fans operating at speeds of 0·1 m/s, 0·3 m/s, 0·8 m/s, and 1·2 m/s, with air conditioning used only once the upper temperature threshold for thermal discomfort is exceeded. For each day of the selected case study year, we estimated the upper temperature limit for thermal comfort and the number of hours in which air conditioning would be switched on.The thermal comfort threshold was increased by the use of fans compared with air conditioner use alone. We found that widespread indoor fan use had the potential to reduce energy demand and greenhouse gas emissions attributable to air conditioner use, without compromising thermal comfort. Taking an annual perspective, the use of fans with air speeds of 1·2 m/s compared with air conditioner use alone resulted in a 76% reduction in energy use (from 5592 GWh to 1344 GWh) and associated greenhouse gas emissions (5091 kilotonnes to 1208 kilotonnes).A common strategy to cope with hot weather is the use of air conditioners, which feed a cycle of high electricity consumption, often delivered by fossil fuel power stations that in turn contribute to further increases in emissions. Moving air with electric fans could serve as a sustainable alternative, reducing air conditioner use and associated greenhouse gas emissions without sacrificing thermal comfort.Australian Research Council, New South Wales Department of Planning, Industry and Environment, and The University of Sydney.

Air conditioners (AC) are responsible for the largest portion of energy use among all auxiliary components of vehicles. Most white-box models developed for dynamic modeling of vapor compression systems (VCS) are not adequate to model vehicle ACs due to stronger dynamics and disturbances caused by frequent door open/close, random numbers of passengers entering/leaving the vehicles as well as intermittent shading effect on roads. In this study, a novel physics-guided deep learning method is proposed for dynamic modeling of vehicle ACs based on both domain knowledge and historical operational data. To maximize the practical values of the model in control and diagnosis of ACs, this research aims at developing an integrated VCS model consisting of individual models of major AC components rather than a black-box model of the entire system. Domain knowledge guides the determination of model inputs and outputs, design of the model structure, and understanding of temporal relationship in developing dynamic heat exchanger models. A newly developed NARX-LSTM-MLP neural network is proposed for heat exchange process modelling. The compressor is modelled by a multiple-layer perception (MLP). Component models are integrated by referring to the physical system structure. Field AC operation data from a city bus collected by IoT sensors are used in this study. Validation results indicate good accordance between measurements and simulation results. The model developed is less expensive, more convenient, and more feasible for health monitoring of numerous vehicle ACs at city level in the context of IoT.

Automotive air conditioning heat pump systems draw increasing attention as an alternative to conventional electric heaters. Once the air temperature falls below the freezing point, frost begins to form on the surface of the evaporator. The accurate defrost strategies could avoid heat exchange efficiency reduction and prevent heating capacity from decaying, which are the main factors affecting the energy efficiency of electric vehicle heat pump systems. The frost characteristic on micro-channel heat exchanger of the electric vehicle heat pump system is tested, and a novel defrosting strategy which is based on the dimensionless analysis method is introduced too. Conclusions could be drawn as following: a correlation that considers the effects of ambient parameters and structural parameters has been developed to predict the frost thickness on fins with dimensionless analyses. Based on this correlation, the relative error and the RMS error between the experimental data and the predicted value are 8.44% and 12.54%, respectively; the effective blockage ratio (EBR), a parameter that accurately reflects the blockage ratio and directly linked to the system operation state, is first proposed. Through the analysis between the EBR and system heating capacity, it can be concluded that the optimal defrosting start-point is identified as the EBR reaches 30%. With this method, the defrosting start-time can be found accurately and effectively to avoid unnecessary defrost cycles, thus leading to a highly efficient operation and low energy consumption for the electric vehicle heat pump system.

In the air conditioning machine, condenser is considered to be the important component. The present study illustrates the condenser’s performance with relevant experiments. The role of a condenser is to release the observed heat from the cooling system because the energy is removed out and the condensed air get drained out and proceeds with its path through the presence of the expansion valve. This present study literally focuses on the external fins and the condenser tubes through the heat transfer mode by the process of forced convection. The temperature changes were calculated for both air temperature system and refrigerator system and appropriate analysis was performed for evaluating the performance of the condenser. The dimensions of the fins, shape and tubing arrangements are also analyzed. The principle of a condenser is to expel the heat out of the refrigeration system by the condensation of vapor. Generally, there is no phase change occurring in the external fluids. In the condenser operated with forced convection mode, the circulated air over the specific surface is maintained with the help of a blower for effective heat transfer. The heat rejection from the condenser is theoretically calculated from the standard value of the compression cycles, without the considering the addition of heat supplied by the compressor inefficiency. The fluid flow of the refrigerant is assisted by the external gravity and hence the inlet tube is aligned at the top whereas the outlet tube is aligned at the bottom. The concept of pipe rising is excluded from the design and extensive care is taken for the adjustment of pipe levels during installation process. Horizontal or vertical air flow is commonly preferred. In the attempt of comparison with various tubes of different diameters, it is considered to focus on smaller tubes with varying diameters to match with the internal surface area of a larger segmental tube.

Heat transfer enhancement is the essential region to protect energy, and furthermore, to accommodate a financial perspective is a concern. Heat transfer enhancement techniques are utilized into different mechanical applications as into heat exchanger, air conditioners, solar tubes, chemical reaction tube and refrigerating devices. The few passive types of equipment as twisted tapes, irregular components, wires inserts etc. are an efficacious technique to upgrade into heat transfer. Amongst the transcendent techniques utilizing in heat transfer for passive type is twisted tape inserts. The present research paper reviews the heat transfer enhancement region with twisted tapes into recent years. Past examinations on various kinds of twisted tapes (basis of review) were shown. Also, the paper unveiled the research for future on twisted tapes will more noteworthy improvement in heat exchanger device additionally gives scope for various altered methods for the new advancement of heat transfer improvement. [copyright information to be updated in production process]

Global warming is a harsh reality of today’s century. All human and animals are facing challenges for survivals. Sometimes challenges are very big. According to the environment and nature’s role all of us make the arrangement for the leaving comfort. Undoubtedly, as the ambient temperature increases, the inside and outside temperature of the building also increases. This increase in the temperature affects the living condition of human being as well as other biota. Those who can afford they can use a mechanical system called as Refrigeration and air conditioning system. The green roof top is an idea where the cost cutting is done in the energy consumption and increases the comfort level of the biota. Thus, the overall objective of the paper is to investigate the impact of green roof on thermal performance for Indian climate. The thermal performance of the green roof over conventional roof has been compared for the results. The temperatures, cooling potential parameters have been compared for the results.

Summer days are quite difficult to live in a non-ventilated house, thus most people choose for air conditioning or air coolers at home, which consumes electricity, money, and other resources. In this research paper, you will learn about the HVAC (Heat, Ventilation, and Air-conditioning) system, which is a revolutionary means of producing air conditioning by utilising natural resources such as wind and sunlight. The component required for this system is readily available. The maintenance is free, and it may be mounted on the roof of a house or elsewhere in the garden. Because the energy used in this system is freely available in nature, it is absolutely free and extremely efficient.

Nowadays, most of the cars have air conditioning as a standard feature, which improves comfort and safety. Automatic temperature control, incorporated cooling, warming, de-misting and de-frosting, air filtration, humidity management, and safety are all characteristics of modern systems. The interior cabin temperature has the greatest impact on passenger thermal comfort. Cabin temperature is to determine by the size of the cabin, the quantity and form of air vents, the overall HVAC system's mass flow rate, and the dashboard, trimmings, and seating materials. The vanes are adjusted manually to establish the airflow direction and in few, it is automatically adjusted. The round-shaped set-up in the cabin's HVAC system has a dynamic mechanism that is mean to spin at a constant speed along its axis. In this work, SUV vehicle cabin has investigated with different speed and find the suitable temperature range. It should be test using CFD software and steady state thermal analysis. According to ANSYS FLUENT, the observed cabin findings include a temperature of roughly 23 °C and an airflow velocity of 5 m/sec.

The desiccant wheel based air conditioning systems are superior over conventional vapour compression systems in terms of the efficiency and power consumption. Researchers are consistently focusing on the various aspects of the desiccant wheel such as the architecture of the wheel, effect of operating parameters on the performance of the wheel and the overall configuration of air-conditioning systems. For the simulations of the air-conditioning systems it is essential to have an accurately performing model of the desiccant wheel. Thus, for solving this purpose, the radial basis neural network is applied to forecast the performance of a desiccant wheel data. The input parameters are the inlet process air humidity, temperature, regeneration temperature, number of rotations per hour of the desiccant wheel and the ratio of the volume flow rates of the process air and the regeneration air. The output parameters are the temperature and humidity of the process air outlet stream. The model is able to predict the original data within ± 5% accuracy and the r-square value is obtained to be 0.9963. A parametric study presenting the variations of the process air outlet temperature and humidity with respect to the various input parameters is also included in the article.

The present study represents theoretical and applied experimental test to advise new configuration of split air conditioning unit with compressor energy saving. The conventional cycle that consists of evaporator, compressor, condenser and expansion valve was set as the base cycle. Three cases will be investigated theoretically; conventional, conventional with partial compression in the compressor with compression completion via evacuated tube and conventional with partial compression in the compressor with compression completion via evacuated tube in the presence of heat exchanger. Five refrigerants are tested theoretically, R- 134a, R-152a, R-290, R-600a and R-1234yf; however the experimental test rig is tested with only R- 134a which is available. The results include cooling capacity, compressor power, condenser heat load and the cycle coefficient of performance (COP).‏ Good performance of the new ‏proposed system ‏with partial compression in the compressor with compression completion via the evacuated tube in the presence of heat exchanger has been found. The results showed that the utilization of evacuated tube with heat exchanger leads to maximum enhancement in system COP by 20.3% in case of using R-290 as a result of consumed power reduction in the compressor by 8.22% and increasing in the cooling capacity by 10.1%.

In this paper, a novel swing compressor with two discharge channels (SCTC) is introduced, which can be an alternative compressor applied in household air-conditioner. SCTC has two discharge ports. The first one without discharge valve operates at all shaft speed and the other one with a high stiffness discharge valve operates at high shaft speed, which is helpful to improve the service life of compressor and discharge valve. Additionally, the discharge close volume is eliminated and the liquid strike can be prevented. In order to obtain the performance of SCTC, a prototype has been tested at three different shaft speeds and its volumetric efficiency, adiabatic efficiency, COP and noise characteristic have been analyzed. The performance of SCTC is always better than that of the swing compressor with no valve (SCNV). Besides, compared with the conventional swing compressor, the COP of SCTC increases by 2.26% at the shaft speed of 1800 r•min−1.

To dehumidify a humid air stream, existing air conditioning (AC) systems substantially overcool the outdoor humid air below its dew point, thereby significantly reducing energy efficiency. Directly capturing humidity, membrane-based liquid-desiccant dehumidification systems separate sensible and latent cooling (SSLC) loads and thus offer a promising pathway for a high-performance AC solution. Design of an energy-efficient SSLC-AC system, however, rests largely on detailed understating of the dehumidification process. While some studies have identified the dehumidification process mainly depends on membrane characteristics, other studies have argued that the process is limited by desiccant liquid or alternatively air thermo-hydraulic physics for typical humid climate conditions. The present study examines performance and physics of the membrane-based liquid-desiccant dehumidification process over a wide range of climate conditions through a novel 3D, two-phase, multi-species CFD model. Decoupling the thermodynamic and hydraulic effects, the study reveals that the dehumidification rate is a linear function of the water vapor pressure potential (J=α ΔP) summarizing the system's thermodynamic state. The slope of the curve (i.e., α) depends on hydraulic transport characteristics of the membrane pores, air stream, and desiccant solution. More importantly, it was found that the air dehumidification process is mainly limited by the air-side transport physics for thin liquid-desiccant films and commonly used porous superhydrophobic membranes. Additionally, results show that, depending on ambient/desiccant conditions and physical dehumidifier characteristics, energy effectiveness and dehumidification rate vary from 13 to 34% and from 0.13 to 1.4 g m−2 s−1, respectively. Therefore, the present study allows to efficiently design future SSLC-based AC systems exhibiting high performance energy metrics.

Due to the great potential of propane in environmental protection and thermodynamic properties, the promotion of propane room air conditioner will make a great contribution to environmental protection. The defrosting behaviors of propane room air conditioner system and rotary compressor were studied by experiments in this paper. Experimental analysis redefines and distinguishes defrosting time and frost melting time, and their relationship with condition temperature is different. The experimental results show that the lower the ambient temperature was, the longer the defrosting time was, but the shorter the frost melting time on the outdoor heat exchanger was. The state of the oil sump and foam layer in propane rotary compressor using Mineral Oil (MO) was recorded and the variation reason for liquid level was analysed during defrosting. Combined with the change of viscosity and liquid level of the oil sump, the experimental results show that the compressor has abnormal oil discharged, and the lower the ambient temperature was, the larger the oil discharge was under three conditions during defrosting process. The total mass of the mixture in the oil sump under the three working conditions is 275.18 g, 289.10 g and 276.41 g, the lubricating oil is 202.97 g, 200.23 g and 189.71 g, and the refrigerant mass is 72.21 g, 88.87 g and 86.71 g respectively when the defrosting process ended. This study will provide an experimental basis of the reliability study and application of propane air conditioners.

Global electricity consumption is continuing to grow at a faster pace over the past few years. Electricity is used most often in buildings and in the growing demand for appliances and air conditioners. Basic strategies to minimize energy consumption include implementing energy efficiency measures and adopting renewable energy. Photovoltaics in particular has received considerable attention. Thus, this paper presents the detailed techno-economic feasibility analysis and environmental utility of a solar PV powered air conditioner system for an office building. The design, simulation and optimization of the system were performed using HOMER software. The system performance analysis was performed using various criteria such as Total Net Present Cost (TNPC), Cost of Energy (CoE), Renewable Fraction (RF) and CO2 emission analysis as objective functions. Energy purchased from the grid, energy sales, net energy purchases, and grid interactions were also analyzed. The simulation results reveal that the values of TNPC, CoE and RF are 2277.61 $, 0.0655 $/kWh and 79.2%, respectively. The total system generation is estimated to be 2875 kWh, of which 80.5% (2315 kWh) comes from PV and 19.5% from the grid. The system reports a grid energy purchase, energy sales and net energy purchase of 559 kWh, 1094 kWh and −534.11 kWh, respectively. The air conditioner's energy demand is fully met at 100%, records 0% unmet load and capacity shortage, and an excess energy of 73.5 kWh. The total annual CO2 emission mitigated is 1459.548 kg, a savings of 36488.7 kg (40.22 tons) is achieved over the system project lifetime.

Cost optimization of heating, ventilation and air conditioning systems (HVAC) in buildings has been approached by using sophisticated methodologies such as model predictive control (MPC) and real-time optimization. However, such techniques are not usually user-friendly to individuals without a process control background. Namely, it can be very difficult for building managers to estimate the economic impact of set point changes. For this reason, it is proposed an economic nonlinear model predictive control (eMPC) using a budget constraint. Using this concept, building managers will be able to balance the trade-off between operational cost and thermal comfort. To demonstrate the proposed approach, a first-principles model of a HVAC system is extended from a previous authors contribution to consider two new features: (1) thermal lag due to energy accumulation in the building envelope; (2) energy consumption by the fans. Then, the implemented HVAC system is tested in open- and closed-loop conditions. The closed-loop simulations showed the advantage for building managers of using the budget-constrained eMPC over the classical approach and On–Off control when using two different budget strategies. This approach ensures an user-friendly interface between building managers (i.e., non-expert users) and eMPC.

Aiming at the problems of extensive management and energy waste in the operation of shopping malls, this paper proposed a shopping mall building energy-saving diagnosis model based on an improved PSO-SVM neural network. Firstly, the operation data with good energy-saving characteristics were selected from the collected historical data of energy consumption by clustering algorithm as the data basis for the establishment of the model. Secondly, the Adaboost algorithm was used to optimize the PSO-SVM neural network to complete the model construction, and the energy-saving data was used to complete the training of the model. Finally, the judgment criteria for abnormal energy consumption were established, and the energy consumption situation at the current moment was diagnosed by using the trained energy-saving diagnosis model. The abnormal judgment criteria of energy consumption were used to analyze the diagnostic results, and the energy-saving diagnosis process was completed, which was verified by case analysis. Through case analysis and verification, the energy-saving rate of the energy-saving diagnosis model established in this paper has been increased from -1.1% to 11.9%, and the problem moments generated during the operation of air conditioning in shopping malls have been successfully diagnosed. The model established in this paper can not only find out the unreasonable conditions in the operation of the air-conditioning system, but also provide a reference for building energy-saving management and operation.

Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.

A method of using condensate water to reduce the airflow temperature around the air conditioner condenser and improve the performance of air conditioner is presented in this study. The structure of traditional split air conditioner is adjusted by changing the installation direction of fan and adding disk-type atomization cooling element (ACE) in the outdoor unit. The performance of the air conditioner under four modes is tested in different environment temperatures. Four modes were named, i.e. the original unit without ACE, original unit with ACE, blowing mode without condensate water and blowing mode with condensate water. The blowing mode with condensate water is used to pre-cool the incoming airflow, and the maximum temperature reduction at the air outlet surface of the condenser is up to 2.2 °C in 35 °C. With the environment temperature increasing, the refrigerating capacity of four modes decreased, and the power consumption increased, leading to the decrease of EER. However, owing to the cooling effect of condensate water, the performance of blowing mode with condensate water was greatly improved compared with the original unit without ACE. The variation rates of refrigerating capacity, power consumption and EER at environment temperature of 43 °C were 8.1%, -9.5% and 20%, respectively. The unit with condensate water could greatly improve the performance of air conditioning in high environment temperatures.

Owing to the recent uprise in summer temperatures, the use of air conditioners has been increasing accordingly. Air conditioners consume a significant amount of energy, and defects in air conditioners usually could lead to even more consumption of energy. Hence, early detection of defects could not only enhance user satisfaction, but also conserve energy. In the present work, quantitative fault detection models for single- and dual-failure modes have been developed using a support vector machine technique based on refrigeration cycle simulation data including normal and defective conditions. The defect modes investigated in the present work include refrigerant shortage and degraded air flow rates for the evaporator and condenser of an air conditioner. The results indicate that the proposed method can predict the values of more than 95% of the defective parameters within ± 5 % for the single-failure mode, and more than 90% of the data within ± 10 % for the dual-failure mode.

Knowledge of sizes of leak holes arising in refrigeration, air conditioning and heat pump systems is critical for safe application of flammable refrigerants, especially hydrocarbons such as R290. Data for leak hole sizes is currently lacking so safety standards have used a range of assumed leak rates that maybe unreasonable and lead to severe restrictions on charge limits and/or high costs for addressing potential ignition sources. Over 1000 leak holes have been measured from various systems. The leak hole areas were found to be clustered around very small values with more than 90% below 0.10 mm2 and 98.8% smaller than 1.0 mm2, irrespective of type, age and size of the system. The largest leak hole size that should be considered for safe design of systems is around 0.5 mm2, or about 70 g min−1 of R290 vapour or adjusted according to the system operating conditions or type of refrigerant.

A parallel power/refrigeration cogeneration Kalina cycle (PPR-KC) system with adjustable refrigeration/power ratio that developed on the basis of the triple-pressure Kalina cycle system was analyzed. The PPR-KC system can produce refrigeration with temperature ranging in either air conditioning or ice making by switching the exhaust refrigerant vapor to the mid-pressure absorber or to the low-pressure one. The influences of the dilute solution from generator to the destination of either mid-pressure absorber (plan A) or low-pressure absorber (plan B) via recuperators on the performances of the PPR-KC system for air conditioning were investigated. The results show that the PPR-KC system matches well the heat source in cascade arranged boiler and generator thus showing excellent thermal performance by optimizing the solution concentrations, boiler superheat and other parameters. Under the given temperatures of heat source 400°C and cooling water 30°C respectively, the variation trends of the cycle parameters and performances of both plan A and plan B are presented. The power recovery efficiency of plan B is about 1.6% higher than that of plan A. When boiler bubble point temperature difference increases from 20 K to 60 K the refrigeration/power ratio of plan B climbs from 0.475 to 1.192.

In grid-connected PV systems, the inverter is one of the important components. Inverter efficiency may vary depending on the input power and voltage of the PV array. This paper analysed three factors affecting inverter efficiency. The first one was the effect of the duration of inverter operations. Analysis of the operation of a PV system that has been operating four years showed an annual average inverter efficiency of 0.90, almost equal to the manufacturer’s specification of 0.91. The study showed that there was no significant degradation in inverter efficiency because a cool temperature (of 25°C) was maintained for the inverter storage room through an air conditioning system. The second analysis investigated the effect of the power input from different types of PV module technology. The study showed that the inverter connected to p-Si PV modules operated the highest efficiency at 0.91. However, detailed analyses showed that PV module technology had less or minimal impact on inverter efficiency. It was the power input from the PV module that has influence on the inverter efficiency. The third analysis involved the study of the effect of irradiance distribution on inverter efficiency. The study shows that the inverter operates at the maximum efficiency of 0.90 at irradiance of above 350 W/m2, at which range solar energy potential is at its highest at around 85% of the total generation. This means that inverter converts almost all the energy supplied from solar PV at this irradiance range. In conducting the third analysis, a location-specific equation, η PHS, for determining inverter efficiency was also developed. The η PHS equation generates the actual inverter efficiency values based on the local irradiance conditions in Phitsanulok province.

To solve the problems of high energy consumed by the cooling system in the data center, this article puts forward a composite air conditioning system. The simulation platform for system operation performance is established, and the accuracy of the simulation platform is verified by experiments. The influence of operation parameters on system performance is analyzed by simulation. Finally, the optimal operation control parameters are determined. The results show that the system can adjust the condenser wind speed and the refrigerant pump operating frequency to meet the cooling requirements and solve the problem of low evaporation temperature in the heat pipe. The evaporative cooling effectively expands the working range of the heat pipe mode and raises the upper limit of outdoor temperature from 8 °C to 15 °C. In the vapor compression mode, when the ambient temperature is lower than 26 °C, the performance of the air-cooled mode is better than that of the evaporative-cooled mode. The condensation temperature can be ensured within a reasonable range by adjusting the condenser cooling wind speed and the compressor frequency. When the outdoor temperature is not less than 26 °C, the evaporative cooling can effectively improve the operation performance

Improving the coefficient of performance (COP) of air conditioner with air-cooled condenser is a challenge especially in areas with hot weather. A spray evaporative cooling system is coupled with the air-cooled condenser of an air conditioning unit, and influence of different outdoor temperatures, mass flow rates of nozzles and operation modes of spray system on the performance of air conditioning system under are investigated. Experimental results show that the application of spray evaporative cooling system has significant effect on the performance improvement of the unit and the improvement rate rises as outdoor temperature increases. By using the spray evaporative cooling system in hot weather conditions, the power consumption can be reduced up by 22% and the COP can be improved by around 42.6%. Even if the spray energy consumption is taken into account, the values of COP are higher than the threshold value of the secondary energy efficiency (3.2). This study demonstrates that an air-cooled air conditioning unit coupled with spray cooling system is a kind of energy-efficient technique, which has a significant potential to improve the unit performance and reduce the electricity demand.

Electric vehicles (EVs) are an increasingly popular option to decrease global greenhouse emissions in the transportation sector. The largest limiting factor is their range, significantly decreased by the cooling load required. In conjunction with the shift to incorporating low-Global Warming Potential (GWP) refrigerants in cooling systems, it is critical to reexamine the design of traditional air conditioning (AC) systems. To this end, a model of a cooling system for an EV was created, while incorporating an ultrahigh-speed miniature centrifugal compressor, allowing for the performance comparison of multiple refrigerants. From these simulations, a centrifugal compression system using HFC-134a provided sufficient cooling capacity for the modeled vehicle (13.07 kW) with lower input power requirements (2.05 kW) than a commercial EV AC system. However, this requires improved heat exchanger efficiencies. A straightforward system design may be attainable with lower operating pressures utilizing the low-GWP HFO-1336mzz(Z) while achieving a nearly equivalent cooling capacity (12.39 kW) at reduced power requirements (1.86 kW). Performance and safety tradeoffs were examined for a variety of refrigerants and azeotropic mixtures. The use of azeotropic refrigerants increased the cooling capacity and energy efficiency compared with the individual components, but with the tradeoff of higher pressure and compressor exit temperatures. Overall, this effort provides specified conditions for EVs while being among the first to demonstrate the potential of low-GWP and low-Ozone Depletion Potential refrigerants in AC systems utilizing ultrahigh-speed centrifugal compressors.

Ground source heat pumps (GSHPs) are considered to provide very efficient air conditioning systems, and this assists in achieving sustainability goals as well as reducing electricity consumption and carbon emissions. The design of such systems, however, depends on the climatic conditions and the geological characteristics of the site; in practice, the optimum design of the system also depends on the characteristics of the surrounding soil. The majority of the research into GSHPs has been focused on cold regions, thus this work is a very useful reference and important in GSHPs’ design in Saudi Arabia and therefore in other hot and arid regions. For the first time in such a hot/dry climate, a rigorous sensitivity analysis method applying the Ground Loop Design software has been employed to analyse 12 parameters that most affect the behaviour of the system. It is concluded that the most important four design parameters are the: thermal conductivity, soil temperature, building load, and fluid flowrate. On increasing these values they have opposing effects on arid environmental conditions, such as those found in the city of Riyadh in Saudi Arabia. In addition, the near-optimum design of a GSHP system in the city of Riyadh in Saudi Arabia has been investigated. The temperature of the water entering the heat pump is an adjustable factor that determines the performance of a GSHP unit. Because of the coefficient of performance of the heat pump, it can also be measured by the value of the entering water temperature. Thus, the entering water temperature (EWT) was selected to be the performance measure of the system, as all the heat transfer processed between the ground heat exchanger components and the surrounding soil is manifested in the entering water temperature. The value of the EWT was fixed both at the baseline and in the proposed design systems, and these were tested over the lifespan of 20 years. The results showed that the length of the ground heat exchanger and power consumption in the proposed design could be reduced by 15% and 1.12% respectively, compared to the baseline system. These results can be used to simplify the design of buildings in similar arid regions worldwide.

Desiccant coated heat exchanger (DCHE) has shown great potential for dehumidification in vapor compression cooling systems and has been widely concerned in the research field of air conditioning, as well as heat and mass transfer in recent years. This paper is aimed at providing fundamental knowledge and research progresses on DCHE for dehumidification and cooling. Initially, DCHE dehumidification is chosen as the research object in this review due to its superiority of the principle by comparing with other two typical dehumidification processes, which are condensation dehumidification and rotary-wheel dehumidification. Then, intermittent dehumidification and continuous dehumidification as two operation modes of DCHE are compared. Finally, the variation characteristics of temperature and humidity during operation are discussed. The current studies of DCHE are reviewed from four aspects, including desiccant coating, cooling source, regeneration heating source and basic heat exchanger. The performance analysis of DCHE is then conducted, according to the different effects of above aspects acting on dehumidification performance, cooling performance and energy efficiency of DCHE. The ongoing researches indicate that the rational construction of DCHE is an effective way to achieve its multi-objective performance optimization. The significant progress of DCHE lays the foundation for applications on other fields. However, further research is required in the field of the selection of desiccant coatings and the structure of heat exchangers to broaden its application market.

Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems “from cradle to grave.” This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work. The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method, the data-driven method, and the database searching method. The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics.

In most countries, buildings are responsible for significant energy consumption where space heating and air conditioning is responsible for the majority of this energy use. To reduce this massive consumption and decrease carbon emission, thermal insulation of buildings can play an important role. The estimation of energy savings following the improvement of a building's insulation remains a key area of research in order to calculate the cost savings and the payback period. In this paper, a case study has been presented where deep retrofitting has been introduced to an existing building to bring it closer to a Passivhaus standard with the introduction of insulation and solar photovoltaic panels. The thermal performance of the building with its improved insulation has been evaluated using infrared thermography. Artificial intelligence using deep learning neural networks is implemented to predict the thermal performance of the building and the expected energy savings. The prediction of neural networks is compared with the actual savings calculated using historical weather data. The results of the neural network show high accuracy of predicting the actual energy savings with success rate of about 82% when compared with the calculated values. The results show that this suggested approach can be used to rapidly predict energy savings from retrofitting of buildings with reasonable accuracy, hence providing a practical rapid tool for the building industry and communities to estimate energy savings. A mathematical model has been also developed which has indicated a life-long monitoring will be needed to precisely estimate the benefits of energy savings in retrofitting due to the change in weather conditions and people's behaviour.

Research on refrigerant mass migration and distribution could not only provide deep understanding of the system performance enhancement, but also contribute to searching the high risk components caused by the Boiling Liquid Expanding Vapor Explosion (BLEVE) due to the high operation pressure of transcritical CO2 system. An experimental bench and a mathematical model of the transcritical CO2 automotive air-conditioning system were set up to explore the refrigerant migration characteristics at different operation conditions. Simulated results of the system were validated by experiments. The distribution characteristics of the refrigerant under different charge were studied and the refrigerant charge suggestions were given. Then, under the appropriate refrigerant charge, the migration characteristics of the refrigerant in the automobile air conditioning system were simulated in the process of startup and shutdown of the compressor and conversion of cooling mode. Furthermore, influence of the parameters, such as ambient temperature, air flow rate, compressor speed on the characteristics of the refrigerant distribution in the air-conditioning system were studied. The results could provide reference for the system design and system safety.

In plant factories, the plant microclimate is affected by the control system, plant physiological activities and aerodynamic characteristics of leaves, which often leads to poor ventilation uniformity, suboptimal environmental conditions and inefficient air conditioning. In this study, interlayer cool airflow (ILCA) was used to introduce room air into plants’ internal canopy through vent holes in cultivation boards and air layer between cultivation boards and nutrient solution surface (interlayer). By using optimal operating parameters at a room temperature of 28°C, the ILCA system achieved similar cooling effects in the absence of a conventional air conditioning system and achieved an energy saving of 50.8% while bringing about positive microclimate change in the interlayer and nutrient solution. This resulted in significantly reduced root growth by 41.7% without a negative influence on lettuce crop yield. Future development in this precise microclimate control method is predicted to replace the conventional cooling (air conditioning) systems for crop production in plant factories.

Improving air quality in occupied area has always been the core focus of ventilation design in cleanrooms. A 10,000 class pharmaceutical cleanroom, with secondary return system, was firstly introduced. Full computational fluid dynamics procedure validated by on-site measurements was then applied to model such cleanroom airflow and particle transport. Energy balance of this ventilation system was also analyzed. Details of room airflow and contaminant fields for the specific zone (above the device and around the human body) were subsequently analyzed concerning the effect of delivering ventilation flow rate and return air volume. Representative parameters, mean age of air, contaminant removal effectiveness, and air change efficiency at the occupied zone and the whole space were evaluated. Results demonstrate that promotion of the return air volume in the occupied area could appropriately reduce pollutant concentration level. Moreover, an increase in ACH (air change rate per hour) did not always shorten the local age of air near the equipment. For a large ACH, it not only will raise the dust around the machine again, it will also cause uncomfortable flow draft. Additionally, when ACH = 20 h−1 and 25 h−1 were achieved respectively, the age of air was reduced by 32% and 21.4% in the whole room and further done by 31.1% and 23.5% in the occupied zone; with identical changes, room air change efficiency (RACE) was achieved at 49.3 % and 50.4 %, respectively. It shows that the increase of ACH seems to have little effect on the air change efficiency. When ACH increases from 15 h−1 to 20 h−1, the efficiency of pollutant removal at the occupied zone will not be significantly improved ( e = 1.78).

The energy sector with 70% public budget influence in Turkey is unsurprisingly one of the sectors over which most policies have been developed. Although Turkey is rich in terms of renewable energy sources such as solar, water, wind, geothermal; as the speed of the consumption of the energy generated through these resources is higher than the production, the use of other non-renewable energy sources is at stake, and increases the emission amount released into the environment depending on this type of energy used. In this study, Energy Extended Input-Output Analysis has been conducted using the data of emission occurred depending on energy use within the framework of energy economy as an interdisciplinary field of study. And research has been carried out on the mutual interdependency between energy and economy. This paper employs an analysis recently published as an input-output table of the year 2014 of Turkey and energy use emission data of the same year in the World Input-Output Database. The emission occurred as a result of one single unit of energy use in the sector of electricity, gas, steam, and air conditioning supply, which are one of the two sectors including the whole components of the energy sector in Turkey, comes first with 51.4327 TJ/million-dollar coefficient, manufacture of coke and refined petroleum products, which is the other sector, ranks at the ninth row with the coefficient of 4.4556 TJ/million-dollar. As a result of the conducted analysis, while normalized total backward energy use emission linkages coefficients (BLj) equal 10.1074 TJ for Electricity, gas, steam, and air conditioning supply sector, they are 1.1676 TJ for the manufacture of coke and refined petroleum products. Normalized total forward energy use emission linkages coefficients (FLi) are 21.448 TJ for electricity, gas, steam and air conditioning supply, yet they are 1.3941 TJ for manufacture of coke and refined petroleum products. Policies on the sustainable use of energy in Turkey have been developed through the achieved results in the content of the study. Policies by focusing on the economy and prioritizing the role of energy in providing sustainable development, preferring environmentally friendly renewable energy sources, and encouraging less production of emission, have especially been mentioned.

Heating, ventilation, and air conditioning (HVAC) systems provide the people working/living inside buildings with ‘conditioned air’ so that they will have a comfortable and safe environment. Thermal comfort is considered as an aspect of a sustainable building in almost all sustainable building evaluation methods and tools. In fact, in the building sector, HVAC systems represent between 40 and 60% of energy consumption. In this paper, two thermal comfort methods have been experimentally analysed (Predicted Mean Vote or the so-called Fanger’s method, and the Adaptive Comfort Method). The measurement campaign was divided into two stages. In an initial stage, HVAC electrical consumption, indoor temperature, carbon dioxide concentration, relative humidity, global horizontal irradiance, and outdoor temperature were measured through controlled conditions, performing a considerable number of tests in 112 days, covering all seasons. Later, in a second phase, with the experimental data, the two thermal comfort methods were calculated analytically. In both cases, the main conclusion is that – when the HVAC system was working with minimum energy consumption – more than 80% of the possible occupants would be satisfied with the indoor temperature, by more than 90% of the time.

Due to the consensus on energy conservation and environmental protection in the international community, and considering the environmental protection and thermophysical properties, R290 has great advantages as an alternative working fluid compared with R22 in the field of air conditioner and heat pump. In the promotion process of the R290 air source heat pump (ASHP), the potential safety hazard caused by flammability can be controlled, but effective control methods are needed to ensure the reliability of the low-temperature heating process. In this paper, a new modified control strategy (MST) was proposed for R290 ASHP. The experimental results showed that the lubricating oil discharged from the compressor with MST was 10.55g less than the original control strategy (OST). In addition, when the temperature judgment condition for starting to adjust the opening of MST was 4°C, the performance was improved (using the MST) by about 1%. Whether from the point of view of reducing the discharge of lubricating oil from the compressor or the storage of refrigerant in the compressor and accumulator, the MST can effectively eliminate the oil blockage, thus improving the reliability of the heat pump system, while having beneficial impacts on the performance of the R290 heat pump.

Heat extremes (ie, heatwaves) already have a serious impact on human health, with ageing, poverty, and chronic illnesses as aggravating factors. As the global community seeks to contend with even hotter weather in the future as a consequence of global climate change, there is a pressing need to better understand the most effective prevention and response measures that can be implemented, particularly in low-resource settings. In this Series paper, we describe how a future reliance on air conditioning is unsustainable and further marginalises the communities most vulnerable to the heat. We then show that a more holistic understanding of the thermal environment at the landscape and urban, building, and individual scales supports the identification of numerous sustainable opportunities to keep people cooler. We summarise the benefits (eg, effectiveness) and limitations of each identified cooling strategy, and recommend optimal interventions for settings such as aged care homes, slums, workplaces, mass gatherings, refugee camps, and playing sport. The integration of this information into well communicated heat action plans with robust surveillance and monitoring is essential for reducing the adverse health consequences of current and future extreme heat.

The variation in the cyclic performance of air conditioning systems (conforming with the latest rating standards) is investigated. Two code testers of very different sizes but meeting the standards’ requirements are used to evaluate the cyclic degradation coefficient (Cd) for the same air conditioner. The measured Cd from the two code testers shows a deviation of about 20%. A validated Modelica model is used to analyze the code testers’ thermal inertia as it is suspected to be a significant contributor. A new parameter called “thermal inertia factor” is defined to account for these thermal inertia effects on the measured Cd. However, all the deviations in Cd are not resolved at this point. The measurement uncertainty is simulated with the Monte Carlo method and discovered to be a critical contributor to the Cd deviation. The current study is the first of its kind and is expected to facilitate improved test procedures by accounting for the variations arising from differences in code tester designs at different laboratories.

Heat and mass transfer capacities of dehumidifier and regenerator significantly affect the performance of a heat pump driven liquid desiccant air-conditioning (HPLDAC) system. When the dehumidifier and regenerator have the same air flow rates, an equal allocation of the total usable number of mass transfer units (NTUm) between the dehumidifier and regenerator is an intuitive choice. However, whether the equal allocation can result in the optimal system performance is still a pending question. Thus, the optimization principle of NTUm allocation between dehumidifier and regenerator in the HPLDAC system is theoretically deduced and illustrated in this study. The results reveal the equal allocation is recommended when the nonlinearity of the isoφ line is insignificant, whereas allocating more NTUm to the dehumidifier than regenerator is recommended when the nonlinearity of the isoφ line is significant. When the NTUm values of the dehumidifier and regenerator are large enough, further increases of the NTUm values show limited effect on performance improvements of the dehumidifier and regenerator. Only when the total NTUm is below 10, does the NTUm allocation optimization play an important role in the system performance improvement, and is a pre-estimation necessary for achieving the optimal system performance.

In warm and humid climates, a primary source of building energy consumption is dehumidification of conditioned air supplied to the building spaces. The system analyzed utilizes a selective membrane to remove water vapor from ambient air instead of a vapor compression cycle or a desiccant. This work analyzed a membrane dehumidification system with a focus on the system energy performance. A system performance goal was set by the project sponsor for an inlet air condition of 32.2 °C and 90% relative humidity, an outlet condition of 12.8 °C and 50% relative humidity and a total cooling load of 3.52 kW resulting in a target COPlatent for the system of 3.34. Models of the basic system components were used to develop the system, analyze operating parameters and predict performance. The results indicate that the system requires two optimizations to meet the target performance: condenser pressure optimization and the use of multiple membrane segments operating at different pressures. Subsequently, a model was developed to analyze the performance of the final system configuration under a variety of operating conditions and yielded a maximum COPlatent of 4.37 for membrane properties comparable to those of the earliest membrane module tested. This may be compared with a COP of about 3.5 for current refrigeration technology at these conditions. The best small membrane sample produced to date would increase the COPlatent of the membrane system to well above 8, suggesting that the membrane system has high promise. Uncertainty analysis was also performed to assess the simulation results.

In an urbanized city, about a third of total electrical consumption is allocated for indoor lighting and air conditioning system in residential and commercial buildings. The majority of the worldwide energy generation comes from burning of non-renewable fossil fuel which is not sustainable in the long run. The use of smart windows technology may catalyze the effort to reduce energy consumption of building and houses. More than 50% of heat entering a building through windows originate from the solar radiation in the near infrared (NIR) region. This candidate smart window material must exhibit dual-band (visible and NIR) modulation that allows selective modulation of NIR heat without affecting visible light transmission. A good electrochromic material in this respect should possess high visible light transmission, high NIR modulation, fast switching between colored and bleached state, and good stability over prolonged usage. In this work, we propose a novel Nd–Mo co-doped SnO2/α-WO3 electrochromic materials (ECs). As compared to the traditional SnO2/α-WO3 ECs, our Nd–Mo co-doped SnO2/α-WO3 ECs exhibits up to 90% visible light transparency (at λ = 600 nm), 62% NIR modulation (at wavelength 1200 nm), high coloration efficiency (~200 cm2 C−1), fast switching time with only 31% electrochromic performance drop (vs 59% of undoped sample) after up to 1000 reversible cyclic test. The enhanced electrochromic performance comes from the presence of Nd–Mo co-dopants that limit the trapping of Li + ion within α-WO3 framework, reduce the extent of crystallization of α-WO3 layer and enhancement of the electronic conductivity by transferring their excess electron to the conduction band of the SnO2. To the best of the authors’ knowledge, the present composition of ECs offers one of the better candidate materials for electrochromic to be used as thermal management layers on smart windows application.

Energy efficiency and thermal comfort can be improved by independent control of temperature and humidity. In recent work, an emerging class of cooling systems known as separate sensible and latent cooling (SSLC) systems have demonstrated 14 to 47% energy savings, while simultaneously providing better comfort control than conventional air conditioning. In this work, SSLC is defined as using two or more cooling processes with unequal sensible heat ratio (SHR) to control temperature and humidity independently and dynamically. Fundamental efficiency limits of SSLC systems are developed for the first time, demonstrating that the Carnot efficiency for SSLC is higher than that of conventional systems. It is revealed that SSLC has particularly high potential for moderate outdoor temperatures, high sensible building loads, and drier indoor conditions. In addition, this work proposes a classification scheme for SSLC systems, revealing an enormous number of feasible cycle permutations. This provides a framework for the important research task of developing SSLC systems that will save energy, be practical to construct, and be controllable.

Due to dependence of energy generation from renewable sources on weather conditions, such systems require cooperation with energy storage facilities. Thermal energy storage with phase change materials (PCM) is often used in systems working with solar collectors, photovoltaic panels, heat pumps, air conditioning systems, waste heat recovery systems and other. However, the appropriate application of PCMs requires a good knowledge of the thermo-physical properties of the materials and practical knowledge of the actual stored energy which depends on the PCM heating/cooling rate. The paper presents measurements of the latent heat for PCMs that are used in low-temperature thermal energy storage. The measurement method used was differential scanning calorimetry (DSC). In the experiments, two commercially available materials – RT15 and RT22 HC – were investigated. The tests were performed at different heating/cooling rates ranging from 0.5 to 10 K/min for samples of a mass 6–11 mg. On the basis of the test results and the proposed calculation method, the total values of energy stored during the phase transition, the temperature of phase change and the heat capacity distributions were determined as a function of temperature. Attention has been paid to the effect of temperature change rate on the measured latent heat capacity that is an important issue in practical applications of PCM. The heat capacity (energy stored) versus temperature distributions for RT15 and RT22 HC materials resulting from the tests can be used in design of latent heat thermal energy storage (LHTES) systems co-working with renewable energy systems. The presented methodology can also be used for investigation of other PCMs.

Green roofs represent a growing technology that is spreading increasingly and rapidly throughout the building sector. The latest national and international regulations are promoting their application for refurbishments and new buildings to increase the energy efficiency of the building stock. In recent years, vegetative coverings have been studied to demonstrate their multiple benefits, such as the reduction of the urban heat island phenomenon and the increase in the albedo of cities. On the contrary, this study aims to verify the actual benefit of applying a green roof on a sloped cover compared with installing a highly insulated tiled roof. The EnergyPlus tool has been used to perform dynamic analyses, which has allowed to understand the behavior of two different stratigraphies in accordance with weather conditions, rain, and irrigation profiles. Results have shown that the installation of a green roof cannot always be considered the best solution for reducing building energy consumption, especially if compared with a classic highly insulated clay tile roof. In terms of summer air conditioning, the maximum saving is 0.72 kWh/m2. The presence of water in the soil has also been proven a crucial factor.