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Cooling by solar energy is one of the key solutions to the global energy and environmental degradation issues. Solar liquid desiccant based on evaporative cooling is proposed as an eco-friendly alternative to the conventional vapour compression systems due to its huge untapped energy savings potential. In this paper, the recent works on solar assisted liquid desiccant cooling and its various applications combined with evaporative air-conditioning under different climates are reviewed and advantages the system may offer in terms of energy savings are underscored. A basic description of the principles of hybrid solar liquid desiccant with direct and indirect evaporative cooling is provided. Finally, solar regeneration methods and recent developments for the liquid desiccant air-conditioning system are presented. [ABSTRACT FROM AUTHOR]

Phase change material emulsions (PCMEs) are multifunctional fluids consisting of phase change materials (PCMs) and carrier fluids. PCMEs could be potential candidates as heat transfer media in heating, ventilation and air conditioning (HVAC) systems. This is mainly because PCME could take advantage of its high heat capacity to reduce flow rate and thus saving pumping power whilst delivering the same amount of cooling effect. PCME can also simultaneously act as cold storage to shift peak-load to off-peak time and improve the COP of systems. However, the optimum design of integrated system requires a good understanding of flow behaviour and heat transfer characteristics of PCMEs. In this paper, comprehensive reviews of their thermo-physical properties and potential applications as thermal energy storage and as alternative heat transfer fluids in air conditioning systems have been carried out to establish their limitations for future research. [ABSTRACT FROM AUTHOR]

Due to the complexity and diversity of energy conversions in HVAC systems, this paper is focused on the central air conditioning systems with water-cooled chiller and its operational energy consumption. Through analyzing the energy flows of the five consecutive loops which extract energy from the conditioned spaces and rejects it to the environment, the global energy intensity index is first to be put forwarded and then the decomposition method which analyzes the influence of the specific consumption (e) and delivered fluid ratios (p) on global energy intensity is proposed. The important conclusion drawn from this method is that it is necessary to decrease both the specific consumption and delivered fluid ratios of the main energy users in order to decrease the global energy intensity of HVAC system. Finally, the global energy intensity of central air conditioning system of a twenty six-story office building in Guangzhou, China in design and real condition is compared and analyzed by e–p decomposition method as a case study. [ABSTRACT FROM AUTHOR]

Control strategy is key technology for efficient and reliable operation of air conditioning system. Although VRV research is booming in recent years, the general control strategy of VRV system is still to regulate refrigerant flow rate while keeping evaporating temperature or discharge pressure constant during cooling or heating process. In this paper, a novel control strategy with variable evaporating temperature is explored under part load conditions. Based on running point determined by original control strategy, the new strategy further reduces running frequency under the same part load conditions. Correspondingly, energy consumption reduces and evaporating temperature rises. Theoretical analysis proves its feasibility of energy saving. Further experimental results show that the novel control strategy would help to improve VRV system energy efficiency and reduce cooling energy consumption especially for part load conditions lower than 50%. [ABSTRACT FROM AUTHOR]

Heating, ventilation and air-conditioning (HVAC) systems are widely equipped in modern buildings to provide indoor thermal comfort and guarantee indoor air quality. In a conventional design, the components of an HVAC system are sized according to a deterministic peak load, predicted according to typical weather condition, building physics and internal load. It has been shown by many studies that this prediction is associated with uncertainties since building physical parameters cannot be accurately set and the weather and the internal load used in the design may be different from the real situation after use. Therefore, uncertainty cannot be neglected in order to properly size a HVAC system. In this paper, a prototype of HVAC system design under uncertainty is proposed, which is able to take uncertainty directly in the design, and most importantly it can assess the performance of a design at the design stage in term of multiple performance indices and the customers’ requirements and preferences, i.e. the new design method falls in the framework of multiple criteria decision making. Case studies are used to illustrate the design procedure, and the result is compared with that of a conventional design method. [ABSTRACT FROM AUTHOR]

Solar-ground source heat pump system (SGSHPS) is a new type of high efficiency, energy saving and environmental protection air-conditioning technology. In this paper, experimental studies and numerical simulation on the performance of a SGSHPS operated in different heating modes were carried out. The experimental system was installed in Nanjing of China and solar collectors were coupled with ground heat exchangers (GHE) through an insulated water tank. Four operation modes including ground source heat pump (GSHP), combined operation mode, day and night alternate operation mode and solar U-tube feeding heat alternate operation mode were investigated during winter season. The heat pump performance, solar collecting performance and borehole wall temperature variations were analyzed and compared for various modes. The experimental results indicate that for the combined operation mode, the system operation efficiency during day can be improved by the assistance of solar energy, and the excess solar energy collected during day can be stored in ground by the GHE to improve the operation performance of GSHP during night. The proportions of heat source burdened by solar and geothermal energy are 43.3% and 50.2% respectively. For the alternate operation modes, the temperature resumption of ground surrounding the GHE can be well achieved due to the intermittent heat extraction of GHE or feeding solar heat into ground and thus the overall utilization efficiency of solar and geothermal energy can be improved greatly. During the whole experimental period, the average COPs are 2.37 and 2.72 for GSHP and SAHP operation mode respectively, and the corresponding parameters are 2.69, 2.65 and 2.56 for the combined operation mode, day and night alternate operation mode and solar U-tube feeding heat alternate operation mode, respectively. The average solar collecting efficiency are 43.6%, 47.3% and 38.8% for the combined operation mode, SAHP operation mode and solar U-tube feeding heat operation mode, respectively. Based on the unit modeling, a dynamic simulation program was constructed to investigate the seasonal performance of the SGSHPS operated in different heating modes, the simulation results show that the seasonal average COP are 3.67, 3.64, 3.52 and 3.48 for the combined operation, day and night alternate operation, solar U-tube feeding heat and GSHP mode, respectively. From the view of improving the overall efficiency and increasing heat source fraction of solar energy, the combined operation mode is the best. [ABSTRACT FROM AUTHOR]

China has been the world's largest producer and consumer of air conditioners, and more and more RACs 1 1 The RACs is short for room air conditioners. would be owned by China's households along with the rapid economic development. Air Conditioner is also considered as one of the largest potential contributors to energy reduction among home appliances because of the huge energy consumption. Therefore, the national energy efficiency standards were issued to promote the use and production of high-efficient RACs. According to China's energy efficiency standards, this paper investigated the electricity savings and CO 2 emission reductions from RACs over the period of 2005–2025. The results indicate that the rural RAC market which develops more slowly than the urban one still has great potential, and government has to revise subsidy policies to make the standards more effective, especially for rural areas. In 2025, the total electricity consumption of RACs is projected to be 598–674 TW h, while the amount without energy efficiency standards is 753 TW h. From 2005 to 2025, the energy efficiency standards for RACs can save 1430–2540 TW h electricity and reduce 908.3–1610. 1 Mt CO 2 emissions in different scenarios. Finally, we suggest that the standards should be revised every 4 or 5 years with higher revision pace of 8% to 10% [ABSTRACT FROM AUTHOR]

Obtained as a research result of conducted project, this paper presents an innovative, energy efficient multipurpose system for a sustainable globally cost-effective building's solar energy use and developed methodology for its dynamic analysis and optimization. The initial research and development goal was to create a cost-effective technical solution for replacing fossil fuel and electricity with solar energy for water heating for different purposes (for pools, sanitary water, washing) in one SPA. After successful realization of the initial goal, the study was proceeded and as a result, the created advanced system has been enriched with AC performance. The study success was based on understanding and combined measurements and by BPS made predictions of AC loads and solar radiation dynamics as well as on the determination of the synergetic relations between all relevant quantities. Further, by the performed BPS dynamic simulations for geographically spread buildings locations, it has been shown that the final result of the conducted scientific engineering R&D work has been the created system of confirmed prestigious to the sustainability relevant performance – globally cost-effective building integrated photovoltaic powered heat pump (HP), assisted by waste water heat recovery, for solar AC, water heating and saving. [ABSTRACT FROM AUTHOR]

In this paper the novel approach of a fuzzy model-based multivariable predictive functional control (FMBMPC) of a heating ventilating and air conditioning (HVAC) system is presented, which is implemented on a real-world test plant. The control law is derived in the state-space domain and is given in an analytical form without an optimization algorithm. The basic principles of the predictive control were extended in a fuzzy multivariable manner and the suggested tuning rules for the proposed control algorithm were depicted, which normally gives satisfactory results. The proposed approach introduces a compact and relatively simple design in the case of higher-order and nonminimal phase plants, but it is limited to open-loop stable plants. For the comparison a classical optimal proportional–integral (PI) controller was also designed and applied. The results show that the FMBMPC approach performs better due to the HVACs’ nonlinear dynamics. In case of interactions influence rejection by the HVAC system, the FMBMPC algorithm outperforms the classical PI approach. The results also show that the proposed approach exhibits better reference-model tracking across a wider operating range. The energy consumption comparison shows that the FMBMPC approach is also more energy-efficient. A shortened literature review of applications of energy-efficient and MPC control for HVAC systems is also presented. FMBMPC control is interesting in the case of batch reactors, furnaces, pressure vessels, HVAC systems and any processes that have strong nonlinear dynamics, multivariable natures and long transport delays. [ABSTRACT FROM AUTHOR]

The installation of smart meters has provided an opportunity to better analyze residential energy consumption and energy-related behaviors. Air-conditioning (A/C) use can be determined through non-intrusive load monitoring, which separates A/C cooling energy consumption from whole-house energy data. In this paper, a disaggregation technique is described and executed on 1-min smart meter data from 88 houses in Austin, TX, USA, from July 2012 through June 2013. Nineteen houses were sub-metered to validate the accuracy of the disaggregation technique. The R 2 value between the predicted and actual A/C energy use for the 19 houses was 0.90. The algorithm was then applied to all houses. On average, daily energy use from A/C increased by 25 ± 11 kWh between a mild temperature day of 15.5 °C (60 °F) and a hotter day of 31.5 °C (89 °F), with an 11 kWh increase just during peak hours (14:00–20:00). Average time operated, number of cycles, and A/C fraction of energy were found to increase linearly with outdoor temperature up to 25 °C (77 °F); a plateau was detected at higher temperatures. The accuracy of A/C disaggregation on 5-min data was found to be comparable to 1-min data. However, 15-min data did not yield accurate results due to insufficient granularity. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the Coefficient of Performance (COP)’s augmentation of an air conditioning system utilizing an evaporative cooling condenser. The experimental facility consisted of four major components, which are, the compressor, the evaporator, the thermal expansion valve, and the condenser. An evaporative cooling unit was located upstream from the condenser. Thermal parameters, such as relative humidity, dry bulb temperature, and wet bulb temperature were measured to evaluate the effect of in-direct evaporative cooling on the system's COP. The results indicated an inverse relation between the condenser inlet dry bulb temperature and the COP. The changes in specific enthalpy of the air across the evaporative cooled condenser were due to latent heat transfer and sensible heat exchanges, whereas the specific enthalpy changes for the conventional condenser were primarily caused by sensible heat exchanges. By using the evaporative cooling condenser to pre-cool the air, the saturation temperature drop through the condenser increased from 2.4 °C to 6.6 °C. It also resulted in an increase of the mass flow rate of refrigerant that went into the evaporator. This mass increase of liquid entering the evaporator consequently resulted in the increase of COP from 6.1% to 18%. A power reduction up to 14.3% on the compressor was also achieved. The result reveals the relation between water consumption and compressor energy saving regarding to their costs. Although greater power reductions were fulfilled at higher dry bulb temperatures, in this circumstance, the cost-optimal applicable temperature is around 33.1 °C. [ABSTRACT FROM AUTHOR]

Heat pump water heaters have been introduced to improve energy efficiency of water heating in buildings. Although much research has been conducted to make up for weak points of heat pumps which occur when their purpose is converted from air-conditioning into water heating, there remain some points to be improved to perform as stably as conventional water heaters. Recently, the hybrid water heating system, which is the combination of a heat pump and a traditional gas fired water heater, is proposed as an alternative water heater to perform more efficient water heating stably. In this paper, the hybrid system is designed for general residential houses in Korea, which have floor area of 106.47 m 2 and its performance characteristics are analyzed numerically. To obtain the performance of a hybrid water heating system, the mathematical models of heat pump components and the correlation, which is derived from experimental data of a gas fired water heater, are applied. Also, using the result of a performance calculation, the economic feasibility study is carried out, with the concept of energy cost savings, to quantify the merits of the system and to establish its operation strategy. The monthly electricity and heat consumption data in a Korean residential house and the price of electricity and gas are applied to reflect an actual situation. [ABSTRACT FROM AUTHOR]

The life cycle energy of a building consists of construction energy, operational energy and demolition energy. Construction refers to initial construction as well as recurring maintenance and repair work. Initial construction represents manufacturing of construction materials, transportation and site related on-site construction processes. Only a few studies focused on life cycle energy use of Indian residential buildings. However, the energy use due to on-site construction processes is either ignored or not modelled with adequate level of detail at present. This paper presents a case study on life cycle energy analysis of a residential development consisting of 96 identical apartment-type homes located in Southern India. Energy use due to transportation of materials and construction equipment use at site are quantified. Sensitivity analysis is carried out to study the influence of building service life and monthly electricity use per home on the relative significance of construction energy and operational energy. The construction energy is found to be a significant component of life cycle energy of residential buildings with partial or no air-conditioning. Further, reduced building service life period and increased energy efficiency achieved in the operational phase makes the construction energy as important as the operational energy with respect to life cycle. [ABSTRACT FROM AUTHOR]

• We propose a comparison study of basic data-driven fault diagnosis for VRF system. • The performance under single fault and multiple faults is tested and compared. • DNN is preferred for multiple faults, and SVM is selected for single faults. • All method has lower HR for F5 and F6 than the rest in the multiple fault diagnosis. • We came up with suggestions based on comparative analysis for subsequent research. HVAC systems occupy a large part of the building's energy consumption. The development of fault detection and diagnosis (FDD) techniques for HVAC system is becoming increasingly essential for building energy saving. The present paper proposes a comparison study on the basic data-driven methods for variable refrigerant flow (VRF) system fault diagnosis. And five widely used data-driven methods were analyzed, which were decision tree (DT), support vector machines (SVM), clustering (CL), shallow neural networks (SNN), and deep neural networks (DNN). The six common types of fault data in VRF system and three evaluation indexes were used to compare the performance of the proposed five FDD methods in single fault and multiple faults. Results indicate that the single fault diagnosis performance of all methods is better than multiple fault diagnosis. The performances of DNN, SNN, and SVM are better than CART and CL no matter single fault or multiple fault diagnosis. Among them, we believe that the SVM method is preferred for single fault diagnosis and the DNN method is preferred for multiple fault diagnosis. And the performance of method CL is the worst, especially in the case of multiple fault classification, the accuracy is only about 48%. The study results are dedicated to providing a reference for subsequent research in FDD of VRF system. Some important remarks are finally concluded in this paper. [ABSTRACT FROM AUTHOR]

As a viable alternative for HCFCs and HFCs in the refrigeration and air conditioning industry, R290 has obvious advantages in aspects of environmental protection and thermal properties. At present, the application of R290 in air source heat pumps (ASHPs) is still in the stage of exploration and promotion. In this paper, the dynamic behaviors of an R290 ASHP were experimentally investigated during defrosting process, and an experimental platform of an R290 ASHP system was built to conduct defrosting experiments in a multifunctional enthalpy-difference laboratory. The variation of pressure and temperature of main components and the refrigerant status in the accumulator during defrosting process are shown in this paper. Experimental data was analyzed by combining the physical characteristics of R290, and the dynamic characteristics under three different working conditions were compared. The defrosting time of the three working conditions was 420 s, 435 s and 865 s respectively. In addition, there was a point M that the temperature difference between the inlet and outlet of outdoor heat exchanger (ODHE) approached zero at 370 s of condition II. The results and analysis of this research can provide effective guidance for improving the reliability of R290 ASHPs. [ABSTRACT FROM AUTHOR]

• Moisture needed to be removed in three building types is calculated. • Salt supported porous composites satisfy most climates and building types. • Zeolites are suitable for return air state, ARI summer and ARI humid climates. • Polyelectrolytes can cope with humid climates and buildings with high wet load. Energy conservation and emission reduction have become a global consensus. As a novel promising energy-saving dehumidification technology, desiccant coated heat exchanger (DCHE)-based air conditioning systems have attracted immense attention recently. This paper provides a quick and reasonable selection of desiccant materials for DCHE systems using water as the cooling medium in different buildings and climates. By the theoretical calculation of moisture needed to be removed in three types of buildings (offices, residential buildings and restaurants) and the analysis of the dehumidification capacity of desiccants in DCHEs reported in the literature, optimal desiccants for different building types and ambient air conditions under given parameters are recommended. Salt-supported porous composite desiccants possess flexible dehumidification performance and can be utilized in most climates and building types, except for extremely humid indoor environments with high requirement for fresh air. Zeolites are especially suitable for return air states, American Air-Conditioning and Refrigeration Institute (ARI) summer and ARI humid climates in buildings with moderate indoor moisture gain, such as offices or residential buildings. Polyelectrolytes can be applied in humid climates and buildings with high indoor wet loads, such as restaurants. This paper offers a promising route to the applications of desiccant materials in novel energy-saving air conditioning technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Distributed real-time optimal control was developed for typical HVAC systems. • Physical meaning in decomposition was enhanced in the proposed scheme. • Computation load was significantly distributed from BEMS to local computation unit. • Global convergence of the distributed optimal control was investigated. • Distributed and centralized optimal control led to similar energy performance. Real-time optimal control (RtOpt) is an efficient tool to improve the energy efficiency of heating, ventilating and air-conditioning (HVAC) systems. RtOpt is always centralized and solved entirely in building energy management systems (BEMSs). However, centralized optimization is not be an efficient solution because real-time operation data in local loops need to be sent to the central computation unit in BEMS for optimization. This paper, therefore, proposes a distributed RtOpt scheme for typical centralized HVAC systems, which uses a dual decomposition mechanism to break the centralized problem into one mater problem and several sub-problems that can be solved in parallel and independently. The mater problem is converted to a simple mean value calculation using a projected sub-gradient method, thus distributing the computation load from the central computation unit into local computation units. Unlike available decomposition schemes in literature, the proposed method considered the functionality and spatial distribution of the major components of HVAC systems, which could enhance the physical meaning and facilitate the application of the decomposition scheme. The proposed distributed RtOpt scheme was tested in case studies, with numerical analysis being used to demonstrate its potential benefits. [ABSTRACT FROM AUTHOR]

[Display omitted] The presence of sensing and actuating equipment faults in Heating, Ventilation and Air-Conditioning (HVAC) systems may result in unsatisfactory indoor thermal conditions and significant wasted energy in the building sector. The design of fault diagnosis algorithms for multi-zone buildings is a highly challenging procedure due to the overall complexity of the system. This paper proposes a distributed model-based fault diagnosis algorithm for detecting, isolating and identifying faults that can affect the actuating devices of Air Handling Units (AHUs) and the sensor devices. Based on modeling the temperature dynamics of each local AHU and its underlying zone with respect to its neighboring zones, a local fault diagnosis agent that collects local control signals and local and neighboring sensor measurements is designed. Each local diagnosis agent is designed to estimate on-line the states of each AHU. For each estimation, a residual signal is derived that corresponds to the difference between the measured and estimated value at each time step. Considering healthy conditions, the residual is bounded by its corresponding adaptive threshold that is calculated considering the effects of modeling uncertainties. Each corresponding pair of residual and adaptive threshold forms an analytical redundancy relation which indicates the possible presence of one or more faults. Exploiting the dependency of each actuator and sensor fault with each Analytical Redundancy Relation (ARR), a decision logic is designed, that can reveal under certain conditions the location and type of the fault during the operation of the system. The proposed algorithm is evaluated using a simulation example of a primary school building with 25 zones. [ABSTRACT FROM AUTHOR]

Highlights: [•] A CFD simulation shows that In-row cooling system can solve the problem in case of cool air cannot reach to the top of rack. [•] This paper shows the new combined cooling system for using in data center. [•] A correlation of dimensionless parameters is presented by SHI and product of Re, Pr and β. [•] Correlation obtained helps to control the rack temperature at any height more effective. [Copyright &y& Elsevier]

Highlights: [•] New concept of a solar-biomass hybrid cooling system was presented. [•] This paper presents the design of a solar-biomass hybrid system. [•] 3-Possible configurations were considered, to get the most suitable for the design. [•] Design was to satisfy a cooling load of 4.5kW, and solar to biomass ratio of 0.7. [Copyright &y& Elsevier]

Abstract: HVAC energy savings have been a key focus of recent building energy management efforts, but the savings typically reduce thermal comfort for building occupants. Established thermal comfort models use complex and person-specific parameters, such as clothing insulation and metabolic rate, to predict individual comfort levels, making the design of automated comfort modelling systems a highly challenging endeavour. In this paper, we investigate the use of humidex, which encapsulates both temperature and humidity, as an easily measurable and highly representative indoor thermal comfort predictor. We verify the feasibility of humidex as an indoor thermal comfort predictor by contrasting its performance to that of the best feature set (the feature set that best predicts the thermal comfort) constructed jointly by recursive sequential forward selection and support vector regression. The analysis using the global datasets, including data from seven climate zones across three continents, shows that humidex is a favourable and easily measurable indoor thermal comfort descriptor when humidity is significant. We take away the message from the analysis and design, develop, and deploy a system that couples a deployment of sensor nodes in an office environment, where each node collects the ambient temperature and humidity at each person's desk, and an automated survey mechanism to record people's thermal sensation votes. We use subjective response through the surveys as ground truth to validate the performance of the thermal comfort prediction using humidex. The results confirm our analysis of global datasets and show that humidex is a good predictor of indoor thermal comfort at high humidity. [Copyright &y& Elsevier]

Highlights: [•] This paper reviews available hybrid liquid desiccant air conditioning system technologies. [•] We cover relevant information such as configurations, and the performances. [•] We focus on the hybrid liquid desiccant with vapor compression system. [•] Conclusions and some important suggestions are presented. [Copyright &y& Elsevier]

• Estimation of annual electricity consumption (EC) of more than 1,700,000 buildings. • EC models based on top-down, bottom-up, regression analysis, GRU and GIS mapping. • Contribution of building and socio-demographic variables on EC. • Effect of temperature on actual and predicted EC used for heating and cooling. • EC is spatialized on different territorial scales. This study financed by ERDF and the Wallonia Region estimates the annual electricity consumption (EC) of building stock, including the 3 building sectors namely residential, tertiary and industrial building. The estimation takes into account appliances, electrical heating, cooling, lighting, cooking and EC by m2 on a building level. The results are spatialized on different territorial scales. Using cadastral data of more than 1,700,000 Walloon buildings and annual EC data from a sample collected in 2012 from the energy reports, the paper assesses the EC of the whole building stock and tests to what extent different types of variables (building factors and socio-demographics) explain annual EC. It then shows which individual variables have the highest explanatory power. In contrast to many other studies, the research recognizes the problem of multicollinearity between predictors in regression analysis and uses Lasso regression to address this issue. Three separate regression models were used to study the predictors of annual EC of residential, tertiary and industrial buildings. EC building factors (appliances, auxiliary and main heating, domestic hot water and cooking) explained the largest share which is 66.46% of the variability in EC for residential buildings whereas the EC usages share for tertiary buildings (lighting, heating and domestic hot water, air conditioning, cooling, etc.) is about 50.53% and 38.55% for industrial buildings. Socio-demographic variables on their own explained about 61.59%, 26.34% and 3.41% of the annual EC, respectively for residential, tertiary and industrial buildings. Hence, the building variables present the highest explanatory power for EC, presumably because heating and cooling EC are included in this study. The study highlights that when attempting to explain EC related to Walloon households, including heating and cooling EC, appliances usage has the strongest predictive power in residential buildings. On the other hand, the projected decrease in EC use for heating in existing residential buildings is −8.82% and −10% for existing tertiary buildings while the projected increase in EC use for cooling in existing tertiary buildings is + 11.94% from 2012 to 2050 on a regional scale. These trends follow the predicted regional heating degree-days (HDD) of −11.76% and cooling degree-days (CDD) of 14.04% for the same period based on the gated recurrent unit (GRU) an implemented deep learning (DL) model. In addition, the produced EC maps on different territorial scales show that the highest EC is seen in large and main cities in general. [ABSTRACT FROM AUTHOR]

• Experiments on high-efficiency heat pump with two, three, four simultaneous faults. • Four faults increased refrigerant superheat up to 18 °C. • NC faults tend to increase refrigerant subcooling. • An existing virtual refrigerant charge sensor was tested with simultaneous faults. Faults in air-cooled vapor compression air-conditioning systems are known to reduce performance, including efficiency, capacity, and lifespan. Their effects have been studied, and fault detection and diagnostic (FDD) methods have been developed as tools for field technicians to install or repair systems, or for monitoring to alert operators to the fault's presence. Most of this work has focused on faults that occur singly. It is likely that in some systems, multiple faults occur simultaneously, but it is uncertain what effects this may have on diagnostics. This paper describes a laboratory study of a split system air source heat pump in which combinations of two, three, and four simultaneous faults occur. The study includes all combinations of: improper evaporator airflow; overcharge or undercharge of refrigerant; liquid line restrictions; and non-condensable gas in the refrigerant, each at multiple fault intensities. Fault features – those characteristics that can be determined from measurements, for use in diagnostics – are analyzed, and the key fault features are presented. A robust existing method for determining refrigerant charge, the virtual refrigerant charge sensor (VRC) is tested using the multiple fault data, in order to understand how its performance is impacted by the combined faults. The VRC performs well, typically able to correctly determine whether a system is undercharged or overcharged, but the magnitude estimates are impacted. The results suggest that simple subcooling-based methods of charging a system are likely to provide unsatisfactory results when other faults are present. [ABSTRACT FROM AUTHOR]

Poor building energy performance often arises from suboptimal operations such as inappropriate control sequences or hard faults in heating, ventilation, and air-conditioning (HVAC) systems. Furthermore, such deficiencies are often left unaddressed due to a lack of accessible analytical tools that can derive insights which identify energy-saving measures using multiple data resources. This paper presents a novel multi-source, data-driven building energy management toolkit as a synthesis of established inverse energy modelling, anomaly detection and diagnostics, load disaggregation, and occupancy and occupant complaint analytics methods in the literature. The toolkit contains seven functions that input HVAC controls, energy meter, Wi-Fi-based occupancy, and work order log data to detect hard and soft faults, improve sequences of operation, and monitor energy flows, occupancy patterns, and occupant satisfaction. The toolkit's unique multifaceted analytical approach was demonstrated on a case study building as a proof of concept. Five faults pertaining to the air handling units' mode of operation and heating coil valves were identified and the generated insights were used to pinpoint operational deficiencies stemming from inappropriate zone temperature overheating thresholds and perimeter heating devices. The toolkit, along with the data from the case study, is open-source and accessible through GitHub (Markus, 2021) to initiate and facilitate future development. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we outline a framework and the algorithms that will enable a home controller to accomplish occupancy-moderated multi-zone, multi-inhabitant space-conditioning under a demand-driven pricing scheme for electricity. We investigated the effects that influencing factors such as the number of zones and inhabitants, randomness of occupancy patterns and thermal mass of the residence can have on the efficacy of occupancy-moderated zonal space-conditioning (OZS) under different scenarios. Simulations driven by real data and highly realistic proxy data reveal that OZS can achieve improvements averaging 23% over the case without under certain settings. Our investigations also revealed that a house with heavier thermal mass stands to gain as much as 15% from OZS with pre-conditioning than a lighter one. We further offer a few pointers on reducing the cost of space-conditioning using OZS under a demand-driven pricing scheme to the average homeowner based on our findings. [Copyright &y& Elsevier]

Abstract: This paper presents the first and second law analyses of the developed solar-desiccant air-conditioning system (SDACS). The results of the analyses show that the solar collector is the main contributor to both energy loss and exergy destruction of the system at 35.56% and 55.30%. The water pipe network contributed to 13.45% and 1.65% of energy loss and exergy loss. Electric heater contributed to 0.66% and 7.94% of the energy loss and exergy destruction. Storage tank contributed to 5.80% and 6.70% of energy loss and exergy destruction. Desiccant wheel contributed to 3.25% and 0.58% of energy loss and exergy destruction. Air fans contributed to 0.44% and 1.51% of energy loss and exergy destruction. At present, the thermal energy system (TES) has energy and exergy performances based on electric consumption of 2.428 and 0.199. The desiccant cooling system (DCS) has energy and exergy performances based on thermal consumption of 0.403 and 0.093. The desiccant cooling system has in terms of energy and exergy performances based on electric consumption of 1.627 and 0.029. The whole system (SDACS) energy and exergy performance based on electric consumption are 1.238 and 0.084. [Copyright &y& Elsevier]

Abstract: A major portion of electricity consumption in buildings in residential, administrative, and commercial sectors is related to air-conditioning (A/C) systems. To reduce and shift the electricity consumption of A/C systems from on-peak hours to off-peak hours, an ice thermal energy storage (ITES) can be utilized. In this paper, thermo-economic optimization of an ITES system was carried out for A/C applications. In order to consider the environmental aspects, a penalty cost was considered for CO2 emission. Applying the genetic algorithm optimization technique, the optimum values of system design parameters were obtained. The objective function included the capital and operational costs as well as the penalty cost due to CO2 emission, without and with costs associated with exergy destruction. The results indicated that, on average, the amount of electricity consumption and CO2 emission of ITES system were lower 9% and 9.8%, respectively, in comparison with those of a conventional system. Furthermore, the ITES extra capital cost could be paid back through savings in electricity cost in 3.43 years. [Copyright &y& Elsevier]

Abstract: Earlier studies used field testing of swimming pool temperatures to validate a mathematical model for predicting the temperature of an unheated pool. Combining those results with manufacturers’ data on the performance of vapor-compression air conditioners as a function of heat rejection temperature, the analyses in the paper suggest that rejecting air conditioning heat to a swimming pool can save approximately 25–30% of single-family residential cooling electricity use and reduce cooling electricity demand during peak conditions by 30–35%, as compared to using the same compressor to reject the heat to ambient air. The savings is expected to vary depending on the severity of the climate, as well as the pool temperature experienced during the summer. The original model was refined so as to accommodate air-conditioner heat rejection to predict pool temperatures based on weather data, pool size, shading of the pool, and air-conditioner heat rejection to the pool. The results of an experimental validation of the augmented pool thermal model are presented here. In addition, the model of a pool-coupled air conditioning system was used to develop a design tool for determining the pool size needed to absorb realistic heat rejection from air conditioners in various California climate zones. [Copyright &y& Elsevier]

Abstract: This paper presents a novel thermoelectric radiant air-conditioning (TE-RAC) system, which employs the thermoelectric modules as radiant panels instead of conventional hydronic panels. The novel radiant system brings a lot of benefits including Freon free, convenient installation, no complex water distribution pipes, quiet and reliable operation, etc. Switching between cooling and heating modes can be easily achieved by reversing the input current. The purpose of this study is to investigate the feasibility and performance of the novel TE-RAC system, including its cooling and heating performances, condensation risk, dynamic thermal response and inertia, and cost-effectiveness. A case study of the TE-RAC system is presented to compare the TE-RAC system with conventional air-conditioning (AC) systems and radiant air-conditioning (RAC) systems in terms of cooling and heating capacities, energy consumption and operation reliability. It is found that the COP of the TE-RAC system could be comparable to conventional RAC systems and AC systems, besides many other benefits in life-cycle performances. [Copyright &y& Elsevier]

Abstract: Energy efficiency and energy saving are important concepts bearing in mind by governments and population during the last years. There exist a widespread concern about fossil fuel depletions and the consequent sharp rise in their value. In particular, building is an area highly influenced by those issues. Studies indicate that 40% of the energy generated worldwide is consumed inside buildings, and then, measures to reduce energy consumption are required. In this work, an optimal controller for distributing the energy consumption rate inside a building and preserving, at the same time, the user welfare is proposed. More precisely, the paper presents a predictive control approach that obtains a high thermal comfort level optimizing the use of an HVAC (Heating, Ventilation and Air Conditioning) system by means of a cost function. The optimization procedure is based on the Lagrangian dual method, which allows the use of parallel programming paradigms in an easy way. This may reduce the computational effort proportionally to the number of processing elements when the problem to solve is large. [Copyright &y& Elsevier]

Abstract: This paper aims to investigate the effects of retrofitting existing public buildings in the “Hot Summer Cold Winter” climate region of China, using simulation and a case study, to see how retrofitted public buildings perform in the face of climate change in the region. This area of China is one of the most challenging regions for providing occupant comfort in buildings, with high demands for heating as well as cooling, together with high humidity levels. The simulation results suggest that energy reduction of up to 40% with improvements to the building enclosure is possible by retrofitting current existing public buildings to the new Chinese National Standard for the Zhejiang Province. Requirements for combating possible increase in energy consumption from heating and cooling demands due to future climate change was also investigated, and it was found that by simply improving U-Values of the building envelope to the new national standards set for the Zhejiang Province, the effects of future climate change can be nullified up to the 2080s. Further improvements to having similar standards as developed countries such as England and Wales will have less significance and cannot nullify the effects of climate change from the newly retrofitted public buildings. However, this can be achieved by involving other energy-saving strategies and installing suitable energy-saving technologies for the region. [Copyright &y& Elsevier]

Abstract: The possibility of storing thermal energy within the building structure to reduce building energy consumption has been studied. Hollow core panels used for a building structure are able to pass air through core cavities and be utilized as thermal storage. Previously, thermal storage models for ventilated slab system using the panels have been developed but it has typically focused on the system development and performance evaluation under particular conditions. As a result, it has been difficult to understand the effect of the system on whole building energy performance. This study develops a computational model for a ventilated slab system and investigates its implementation in a whole building energy simulation program, EnergyPlus. The system has two major components: an auxiliary air handling unit (AHU) and a radiant slab with hollow core panels. The auxiliary AHU includes an outside air mixer, coils, and a fan to produce either conditioned or unconditioned air depending on the user''s input. The air is then controlled by a defined delivery method, after passing through the cavity of the panel. This paper illustrates the new model development for the building energy simulation program and provides some evaluation with an existing model from another study. [Copyright &y& Elsevier]

Abstract: Heat flow through the roof contributes in the total heat gain of a building. The contribution becomes more severe for single story houses covered by metal sheet roofing. This paper presents a new design for metal sheet roofing structure in order to improve its total thermal resistance. Its main concept is to utilize phase change material properties to firstly absorb the downward heat flow made by incident solar radiation to the room and then release it back to the environment by means of the naturally favored external convection especially during the nocturnal cycle. Experimental and numerical analyses have been conducted to compare thermal performance of the new design and the available normal roofing with the same materials and color. A general mathematic equation system, which can be used for further evaluation and prediction of the new design with varied parameters, has been derived for the thermal process through the roof. The results show that the new design can effectively reduce the downward thermal flow through the roof into the house. As a consequence, the cooling load of the house can be lower and more electricity for cooling attempt can be saved. [Copyright &y& Elsevier]

Abstract: Separate heat pipe heat exchanger (SHP heat exchanger) transports heat from the indoor air to the outdoor air by making use of the temperature difference. It consumes much less energy than split air-conditioners in telecommunication base stations (TBSs) because of no compressor. In this paper an annual energy-using simulation module of SHP was built up in the building energy simulation tool DeST. The SHP model was basing on the theoretical and experiment results of the heat transfer performance and the energy consumption. As the heat transfer quantity of SHP was interplayed with the indoor air temperature, the solution for the models of the dynamic thermal process in building and SHP heat exchanger was the key part, which was carried out by the coupling calculation. The reliability of SHP model and the coupling solution was verified by an empirical test. Finally, case study on the design of air-conditioning systems in TBSs was carried out to illustrate the engineering applications of SHP module. [Copyright &y& Elsevier]

Abstract: An experimental study is reported in this paper for a diffuse ceiling ventilation concept. The analyses were carried out with two different porous surfaces mounted in a suspended ceiling: perforated tiles of aluminium and of gypsum. Ventilation air was supplied above the suspended ceiling effectively creating a plenum for air distribution. The experiments were carried out in a climatic chamber and documented an air change efficiency equal to fully mixed conditions with a pressure drop of 0.5–1.5Pa and with no evidence of thermal discomfort. The magnitude of the pressure drop was enough to sustain the pressure of the plenum and ensure uni-directional airflow through the ceiling. Consequently only reverse flow of insignificant magnitude was observed which has a positive impact on the hygiene of the plenum. Furthermore, the measurements documented that the ceiling acts as a radiant cooling surface which increases the potential and applicability of the concept. Risk of thermal discomfort was not disclosed but the study did show evidence of large fluctuating air movements which could stem from transient behaviour creating sensations of draught to the occupants. [Copyright &y& Elsevier]

Abstract: Nowadays, dynamic analysis of air-conditioner units is essential to achieve satisfactory comfort conditions in buildings with low energy consumption and operation cost. In this paper, a nonlinear multi input–multi output model (MIMO) of an air-handling unit (AHU) is considered. In the presence of realistic harmonic disturbances, nonlinear dynamics of AHU is investigated. The effect of various thermodynamics and geometrical parameters on limit cycles behaviour of the indoor temperature is investigated. It is observed that the indoor space volume plays as the bifurcation parameter of the system. Decreasing the indoor space volume leads to the occurrence of secondary Hopf (Neimark) bifurcation and consequently the unstable quasi-periodic solution of the indoor temperature. To overcome this problem, a multivariable control strategy based on feedback linearization approach is implemented, in which the air and cold water flow rates are the control inputs while the indoor temperature and relative humidity are the control outputs. It is shown that the designed controller guarantees the comfort indoor conditions by preventing the unstable quasi-periodic responses and improving the limit cycles behaviour. [Copyright &y& Elsevier]

Abstract: This paper presents the effect of operating water mist system to enhance the energy efficiency of air-cooled chillers under various operating conditions. A thermodynamic model for an air-cooled chiller with twin refrigeration circuits coupled with a water mist system was developed and validated by measured operating data. The validated model was used to investigate how the thermal properties of the entering condenser air and the performance of the air-cooled chiller varied under different operating schemes with water mist pre-cooling. Under the conventional head pressure control (HPC) with a designed water mist generation rate, the coefficient of performance (COP) increased by up to 21.3%. The chiller performance could be improved further under variable condensing temperature control (CTC). Under CTC, chiller COP was increased up to 51.5% with optimal water mist generation rate. The potential energy savings of these chillers serving a representative office building in subtropical climate was evaluated, and CTC coupling with optimal water mist generation rate would reduce the annual total electricity consumption for cooling by 14.1%. The water consumption of the water mist system was comparatively small, comparing with the total water losses for an open-loop cooling tower system with equivalent heat rejection capacity. [Copyright &y& Elsevier]

Abstract: In general, a proper balance of temperature and humidity control is essential for efficient datacenter operation and is integral to protecting the significant investment in computer and network technology in datacenter facilities. However, the rising costs of energy and the drive to be green are resulting in a greater demand to conserve energy. One method of reducing facility costs for a chilled water plant is by adding an economizer. The purpose of this study is to develop energy models of the most common economizer systems. A normal chiller plant with an air-side economizer and a water-side economizer are compared. Results show that outdoor conditions influence facility energy consumption. This paper provides terminology and definitions for the two different types of economizer modes and compares their energy performance against key datacenter attributes in temperate or subtropical regions. The electrical end use breakdown and the Power Usage Effectiveness (PUE) value for a typical year were estimated. The water-side economizer made it possible to achieve a maximum energy performance improvement of about 16.6% over the reference base cooling system, whereas the air-side economizer made it possible to achieve about 42.4% improvement. [Copyright &y& Elsevier]

Abstract: Cool roofs are an emerging technique with a recent growing interest worldwide. The aim of the present paper is to present the application of cool roofs’ technology in a laboratory building located in Iraklion, Crete, Greece. The building is monitored towards its energy performance and indoor environment before and after the implementation of the cool roof technology. The specific case study is intended as a shining example of the cool roof capabilities in improving the thermal conditions in non-air conditioned and in reducing the energy consumption in air conditioned buildings. [Copyright &y& Elsevier]

Abstract: Cumulative sum (CUSUM) chart is a general method in statistical control engineering to monitor controlled variables. CUSUM chart has been applied to VAV terminal units by NIST for fault detection, known as VAV Box Performance Assessment Control Charts (VPACC) method. This paper combines CUSUM method with a fault counter approach, which extends the functionality of CUSUM method from fault detection to fault diagnostics. To use this method, user needs to specify a causal relationship between all the control variables, and between the control variables and their controlling components. Based on the real time monitored data, a CUSUM score is calculated for each control variable, and a fault counter is then updated based on an automatic count mechanism. The testing of this approach in a simulation case shows that it has good performance in detecting incipient faults. It is realized that the CUSUM method can only detect faults that lead to control problems, therefore the capability of this method is limited. But the proposed method has some strong advantages, for example, it requires only building control related sensor information, and it can be easily adapted if the system is changed or upgraded, which frequently happens in renovations. [Copyright &y& Elsevier]

Abstract: This paper presents a study of an ejector expansion CO2 air conditioner system. A comprehensive analytical model for 3-ton air-to-air controllable ejector expansion transcritical CO2 air conditioners was developed and validated. The ejector component efficiencies were estimated using empirical correlations, instead of being simply assumed to be fixed values as done in other literature studies. Parametric studies of the ejector expansion CO2 systems show that the coefficient of performance (COP) and the cooling capacity reach maximum levels when the motive nozzle throat diameter becomes 2.8mm; the maximum cooling COP and cooling capacity occurred for a mixing section constant-area diameter of between 4.1 and 4.2mm; COP and cooling capacity are affected by the outdoor air temperature. At particular ejector geometries and an outdoor temperature of 37.8°C, the transcritical CO2 system using an ejector as the expansion device outperformed a conventional expansion-valve transcritical CO2 system in COP and cooling capacity by approximately 30.7% and 32.1%, respectively. A careful selection of ejector geometry, such as motive nozzle throat diameter and mixing section constant-area diameter, is critical in order to improve the performance of an ejector expansion CO2 air conditioning system. [Copyright &y& Elsevier]

Abstract: This paper deals with individual air-to-air heat pumps in Danish dwellings and summerhouses and the question of to what extent they actually deliver savings of energy consumption. Results show that 20% of the expected reduction of electricity consumption is converted into increased comfort in the homes, including extended heating areas, keeping a higher temperature and a longer heating season and using the heat pump for air conditioning. Data include electricity consumption in 185 households before and after installation of heat pumps together with survey results of 480 households. Furthermore, 12 households were selected for in-depth analysis including technical inspection and qualitative interviewing. Especially for summerhouses, results indicate that on average there is no reduction in electricity consumption, as energy efficiency is counter balanced by increased comfort and changed heating practices. These results have to be taken into account when making long-term energy planning for a sustainable energy system. [Copyright &y& Elsevier]

Abstract: This paper presents a new hybrid steady-state modeling approach for air-conditioning systems. At the system level, it follows the first principles to keep the conservation of mass, energy, and momentum, respectively. At the component level, the physics-based component models are entirely or partially replaced with neural networks. Component neural networks can be trained using the data from laboratory or from the well-validated physics-based component models. Numerical comparisons between the system model consisting of component neural networks and that consisting of physics-based component models indicate that the two system modeling approaches give very close predictions in a wide range of operating conditions. With the proposed hybrid modeling approach, robustness and speed of system modeling can be significantly improved. [Copyright &y& Elsevier]

Abstract: Many parameters have been used to evaluate the thermal performance of envelope wall/roofs, most of them for air-conditioned buildings. In this paper, the interest is focused on parameters to assess the thermal performance of envelope wall/roofs for non air-conditioned buildings. Five groups of parameters, some previously used and some newly proposed, have been analyzed. To test the evaluation parameters, numerical simulations of the periodic heat transfer through five different roof configurations have been carried out. This research shows the suitability of the energy transferred through the wall/roof during a day, the decrement factor, the discomfort degree hours, and the hot (or cold) thermal performance index to be used for thermal evaluation of wall/roofs in non air-conditioned buildings. The sensitivity of these parameters with climatic conditions and with the outdoor surface solar absorptance is analyzed. Additionally, it has been shown that the steady-state thermal transmittance, the thermal admittance modulus, the periodic thermal transmittance modulus, and the surface decrement factor, calculated with surface temperatures, are not suitable parameters to evaluate wall/roofs in non air-conditioned buildings. [Copyright &y& Elsevier]

Abstract: The residential sector uses nearly 30% of all electricity in Canada, and, it is important to know how this energy is being used, so that savings may be identified and realised. We propose a method that can be applied to hourly whole-house electrical energy data to partially disaggregate total household electricity use into five load categories/parameters (base load, activity load, heating season gradient, cooling season gradient and lowest external temperature at which air-conditioning is used). This paper develops the proposed method, and verifies it using high-resolution end-use data from twelve households with known characteristics. We then apply the method to hourly whole-house (smart meter) data from 327 households in Ontario. The roll-out of smart (advanced) metering infrastructure in many countries will make hourly whole-house data abundant, and we propose that this method could be widely applied by utilities to target their demand-side management programs towards households more likely to provide benefits, thus increasing the cost-effectiveness of such programs. [Copyright &y& Elsevier]

Abstract: This paper presents an investigation of the influence of local insulated roofing materials used in Burkina Faso on air conditioning loads of typical individual houses located in dry tropical climates. The walls are made of a composite clay–straw mixture whereas the insulated materials are made of red wood, white wood, and two assembled insulated panels. The thermophysical properties of the insulating materials as well as the clay–straw composite have been studied, utilizing an experimental apparatus based on the hot plate method. The values of the thermophysical properties obtained are in the same range as those published in the literature. Afterward, the house has been modeled using TRNSYS together with the climatic data of Ouagadougou. This simulation shows that the clay–straw mixture reduces the air conditioning load by about 8% compared to clay walled houses. As for the roof, the study indicates the influence of the insulated materials on the air conditioning load. Hence, a 1.5cm thick insulator made of red wood induces a saving of energy about 6.2% and 12.1% for an insulation panel made of natural fiber and a lime–cement mixture on the air conditioning load. [Copyright &y& Elsevier]

Abstract: In Hong Kong, conventional air-conditioning (AC) systems cause a high energy consumption and poor indoor thermal comfort. This paper investigated the AC load profiles of three typical local commercial buildings, i.e. office, hotel and retail, and examined the energy consumption of liquid desiccant cooling system (LDCS) for these buildings. Simulation results showed that the cooling load contributed to more than 98% of total annual load, with high latent load proportion from March to September. The high reheating ratio, i.e. from 60% to 90%, is found to be the main reason for the poor thermal comfort. Therefore, the LDCS which could handle sensible and latent loads separately was proposed. However, the electricity-driven LDCS was found not suitable for local commercial buildings. significant energy saving could be achieved by the solar-assisted LDCS system with thermal storage, when the installation area for solar collectors is larger than the minimum required one, i.e. 9.7m2/(kWm−2) for office and 12.7m2/(kWm−2) for hotel buildings. Energy saving of different system types with different installation areas was also studied. The solar-assisted LDCS shows more energy saving in winter but less in summer. Results and conclusions can be useful for researchers and local engineers. [Copyright &y& Elsevier]

Abstract: The paper presents a study of solar electricity generation and energy demand for heating and cooling of housing units’ assemblages. Two-story single family housing units, located in northern mid-latitude climate are considered in the study. Parameters studied include geometric shapes of individual units, their density in a neighborhood, and the site layout. The plan shapes of the housing units included in this study are rectangles and several variants of L shape. Site layouts studied are characterized by a straight road, a south-facing or a north-facing semi-circular road. Rectangular units and a site layout with straight road serve as reference for evaluating the effect of shape and site parameters. Results indicate that a significant increase in total electricity generation (up to 33%) can be achieved by the building integrated photovoltaic (BIPV) systems of housing units of certain shape-site configurations, as compared to the reference. The energy load of a building is affected by its orientation and shape. Increased heating demand by L variants (by up to 8%) is more than offset by annual electricity production of their BIPV systems (by up to 35%). Heating and cooling loads depend significantly on unit density in a site; Attached units require up to 30% less cooling and 50% less heating than detached configurations of the same site. Variation of surface orientation, particularly in curved site layouts, enables the spread of peak electricity generation over up to 6h. This effect may be beneficial to grid supply efficiency. Energy balance assessment indicates that some unit shapes generate up to 96% of their total energy use. Neighborhood configurations studied generate between 65% and 85% of their total energy demand. [Copyright &y& Elsevier]

Abstract: Presently the essential research trend for sustainable buildings is the use of renewable energy sources and the development of new techniques of energy storage. Phase change materials (PCMs) may store latent heat energy in addition to the typical sensible energy capacity of current building materials, allowing to store significantly more energy during the phase change process (solid to liquid and vice versa). The incorporation of PCMs into building envelope solutions takes advantage of solar energy, contributing to the overall reduction of energy consumption associated to use of the air conditioning systems. This paper presents and discusses research developed in two main components: experimental testing and numerical simulation of a building component with PCM incorporation. The main goal of the experimental testing carried out was to evaluate the effect of the incorporation of PCM macro encapsulated into a typical Portuguese clay brick masonry enclosure wall. It is evaluated the influence of the phase change process of the PCM over the attenuation and time delay of the temperature fluctuations for indoor spaces. The experimental results allowed the calibration and validation of the numerical model, enabling to carry out parametric studies with different PCMs quantity analysing consequent temperature damping and time delay. [Copyright &y& Elsevier]