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Covering the radiant cooling surface with infrared-transparent membrane effectively improves the condensation resistance and cooling capacity of radiant cooling. However, the air layer structure formed by the infrared-transparent and double-layer hollow membranes is easy to destroy, resulting in condensation problems. Inspired by the hollow structure of natural bamboo, an infrared-transparent bubble wrap assisted radiant cooling panel (BWRCP) aiming at improving the strength and cooling capacity was proposed by using the infrared-transparent bubble wrap consisting of infrared-transparent membrane and air-filled pores to layer the radiant cooling panel. Both experimental investigation and numerical calculation of the cooling capacity of the infrared-transparent bubble wrap assisted radiant cooling system were carried out. Experimental results showed that the cooling capacity of BWRCP at condensation-free condition was 93.54 W/m2, which was 33% higher than traditional radiant cooling without covering infrared-transparent bubble wrap. Numerical results showed that the air-contact surface temperature of the infrared-transparent bubble wrap was higher than the dew point temperature. It provides condensation-free operation in the thermal environment of 26 °C and 45%–80% RH. Therefore, compared with traditional radiant cooling, BWRCP significantly improves the cooling capacity at condensation-free condition. It demonstrated a novel structure design and operation guidance for the high-performance radiant cooling technology. [ABSTRACT FROM AUTHOR]

Radiant cooling has well been acknowledged as energy efficient and thermal comfortable technology compared to conventional convective cooling. However, the radiant cooling exists two serious problems (viz., insufficient cooling capacity and high condensation risk) especially in hot and humid climate zones. By adding double-skin infrared transparent membranes (DIMs) onto radiant cooling panel, the air-contact surface can be separated from the cooling source surface, which makes it possible to use a low-temperature cooling source while maintaining air-contact surface higher than dew point temperature. The DIMs are transparent to radiant heat transfer which yields great cooling capacity while chilled ceiling has high emissivity (e.g., above 0.9). However, for metal chilled ceilings having low emissivity, radiant heat from cooling load to chilled ceiling would be reduced through DIMs, which results in insufficient cooling capacity. In this paper, a type of adaptive double-skin infrared membranes (a-DIMs) consisting a high-emissivity membrane and a high transparent membrane is proposed to improve cooling capacity of conventional metal chilled ceilings. The high-emissivity membrane serves as radiant cooling surface instead of low-emissivity chilled ceiling so as to improve radiant heat flux, while the high transparent membrane permits great radiant heat from cooling load to chilled ceiling. A combined heat transfer analysis based on semi-transparent surface radiation and natural convection were carried out to predict cooling capacity of condensation-free radiant cooling. The results indicate that the cooling capacity could be up to 101.9W/㎡ by adding a-DIMs consisting of a high-emissivity membrane of 0.96 and a high transparent membrane of 0.87, which is improved by 2 times compared to conventional metal chilled ceiling with low emissivity of 0.2. Moreover, the cooling capacity by adding a-DIMs is further improved by 25% compared to that by using both infrared transparent DIMs presented in our previous work. The results also indicate that the cooling capacity could be improved by above 2 times compared to conventional low-emissivity metal chilled ceiling by using the radiant cooling with a-DIMs for various humidity. It will be of great guidance for high-performance radiant cooling design without condensation and improved cooling capacity for low-emissivity metal chilled ceiling. [ABSTRACT FROM AUTHOR]

Passive radiative cooling, as a cooling technique with no energy input, can continuously radiate heat into the supercooled universe. However, the continuous cooling effect tends to cause the problem of nighttime overcooling. Moreover, non‐renewable radiative cooling materials and energy‐intensive processing methods lead to increased carbon emissions and resource consumption. Therefore, there is an urgent need to develop a renewable and environmentally friendly self‐adaption radiative cooling thermal management material. In this paper, a high‐performance self‐adaption thermal management wood composite aerogel material is designed and prepared by in situ growth of multi‐scale silicon dioxide on wood. The constructed passive radiative cooling material has a sub‐ambient cooling effect of up to 13.5 °C and 20.2 °C  during daytime in winter and summer, respectively. Meanwhile, it has a certain thermal insulation performance (2.0 °C above ambient) due to low thermal conductivity (0.063370 ± 0.000329 W m−1 k−1) at night in winter. In addition, the material is also suitable for fog–water harvesting (fog–water harvesting rate of 59.27 ± 0.76 mg min−1) due to its hydrophobicity. This work can significantly promote the practical application of passive radiative cooling materials. [ABSTRACT FROM AUTHOR]

The thermal sensation of people is subjective. It depends on the external climatic condition and thermal history of a person. Thermal comfort standards suggest a narrow temperature range to assert an environment as comfortable or otherwise. It is important to evaluate people's thermal perception in different climatic regions and set comfort limits based on their thermal perception. This study evaluates the thermal perception of subjects in hot and humid climatic regions at higher indoor temperatures and air velocities. Three different thermal environments chosen for the study are air conditioned (AC), naturally ventilated (NV), and radiant cooling (RC) thermal environments. The study shows that more than 80% of subjects voted as comfortable in AC and RC thermal environments for the measured Top and va range of 25.3 – 28.4℃/0.1 – 0.3m/s and 25.9 – 29.1℃/0.1 – 0.9m/s respectively. The findings gathered from the study in NV environment indicate that 68% of subjects opt for the use of table fans over ceiling fans. The subjects' free control of air movement improves their thermal sensation over no control of air movement, indicating that they prefer table fans and free control of air movement. In AC, NV, and RC thermal environments, humidity and air quality remain uncontrolled. In AC and RC thermal environments, less than 20% of subjects voted unacceptable for the humidity sensation and Perceived air quality (PAQ) scales in nearly all the studied experimental conditions. In NV thermal environment, the percentage of subjects voting dissatisfied on the humidity sensation scale and PAQ scale is 30-52% and 26-37%, respectively. This outcome shows that a thermally comfortable environment with air movement improves subjects' humidity sensation and PAQ even when humidity and air quality are unaltered. The study points out that air velocity played a vital role in influencing the thermal sensation, humidity sensation and perceived air quality of subjects in the three studied thermal environments. Further the study shows that with free control of air movement will significantly aid in rising the comfort temperature band of tropically acclimatized subjects. Practical application: The study shows the variation in limits of thermal comfort indices such as operative temperature and air velocity for tropically acclimatized subjects in three thermal environments. The same group of subjects participated in the subject study conducted in air conditioned, naturally ventilated and radiant cooling thermal environments. The outcomes indicate that subjects are comfortable at higher indoor temperature and air velocity. Further the outcomes showed that the humidity and air quality sensation of subjects is influenced by the subjects' thermal sensation and air velocity. [ABSTRACT FROM AUTHOR]

The radiant systems come to the fore due to energy saving potential and good integration. The effect of different forms of cold surfaces on human thermal comfort is focused on its application. A novel natural convection-radiant evaporator for heat pumps was developed and its influence on thermal comfort was investigated. A numerical model of the chamber with the evaporator was established and verified with experimental results. Thermal comfort experiments were conducted in a climate chamber and the influence of its asymmetric and uneven cold radiation on the thermal comfort was investigated. Due to the limitation of PMV in uneven radiation situations, the revised predicted mean vote (RPMV) was proposed to assess the thermal comfort in asymmetric and uneven radiation environments based on experimental results. Based on RPMV, the influence of the surface area and temperature of the evaporator on thermal comfort was numerically analyzed. The results indicate that indoor air temperature and relative humidity, RPMV increase with the increase of plate temperature, but decrease with an increase in plate area. The most favourable indoor thermal comfort environment was obtained at an indoor air temperature of 28°C and relative humidity of 50%, which is 2°C higher than traditional air conditioning system. [ABSTRACT FROM AUTHOR]

People usually experience transient thermal environments when entering or leaving a conditioned indoor environment. This has been previously explored but there is little knowledge on the impact of temperature step-changes on thermal comfort in a radiantly cooled environment. We aim to investigate human comfort and underlying physiological mechanism in such conditions. We assessed thermal comfort, sick building syndromes (SBS) symptoms, and physiological responses. Twenty healthy participants were exposed to three temperature step-change conditions with three outdoor air temperatures (29 ℃, 33 ℃ and 36 ℃) and one indoor air temperature of 26 ℃. Subjective evaluation was collected through a questionnaire. Blood oxygen saturation (SpO2), skin temperature, and electrocardiograph (ECG) were measured. As expected, the overall thermal sensation, comfort, acceptability, preference, and subjective air freshness changed significantly before and after temperature step-changes. Perceived sweat and chest tightness were also affected by the temperature step-changes. Skin temperature, heart rate, time-domain, and nonlinear heart rate variability were affected significantly under temperature step-changes. We observed the overshoot phenomenon with thermal sensation and subjective air freshness under temperature down-step. Thermal sensation had a faster stabilization time than the measured physiological parameters (i.e., skin temperature, heart rate and heart rate variability) under temperature step-changes. The stabilization time before starting a thermal comfort experiment should be at least 30 minutes. Thermal sensation and skin temperature had an asymmetry effect on temperature step-changes.

Taking the building in hot summer and cold winter zone as research object, the transient system simulation program (TRNSYS) simulation platform was used to build the active phase change energy storage floor module. The simulation model of the active phase change cold storage floor air conditioning system and the conventional fan coil plus fresh air conditioning system was established, and the energy saving and economy were simulated and calculated. The effects of chilled water temperature on energy storage and release characteristics of active phase change energy storage floor, room temperature fluctuation and coefficient of performance (COP) of heat pump were investigated under the condition of night cold storage operation in the cooling season and typical day. The results show that under the condition of phase change cold storage at night, the optimal chilled water temperature is 9 °C when the cooling load per square meter is 74.78 W. When the cold storage heat pump adopts the intermittent operation scheme with low electricity price at night, the COP of heat pump operation can be effectively improved with reduced operation cost. Compared with the conventional fan coil plus fresh air air conditioning system, the energy consumption of the active phase change energy storage floor air- conditioning system in the cooling season is reduced by 30.5% with operating cost reduced by 44.24%, and the comprehensive refrigeration energy efficiency ratio reaches 2.38 in summer. [ABSTRACT FROM AUTHOR]

Researching novel cooling and heating technologies as alternatives to conventional vapor-compression refrigeration cycles has received growing attention in recent years. Thermoelectric (TE) systems rank among promising emerging technologies within this category. This paper presents a comprehensive investigation, utilizing numerical modeling and analysis via COMSOL Multiphysics along with experimental validation, to evaluate the performance of a radiant cooling ceiling panel working on thermoelectric principles. Performance metrics are based on thermal comfort levels within the designed test chamber. The system comprises a rectangular test chamber (~1.2 m × 1.2 m × 1.5 m) with a centrally positioned ceiling panel (dimensions: 0.6 m × 0.6 m × 0.002 m). Four TE modules are attached on top of the ceiling panel, facilitating effective cooling to regulate the ceiling temperature to the desired setpoint. The resultant lower ceiling temperature enables heat exchange within the chamber environment via radiation and convection mechanisms. This study examines the time-dependent variations in mean radiant temperature and operative temperature under natural convection conditions, with comfort level assessment carried out using the PMV method according to ASHRAE Standard 55. An experimental chamber is built to validate the numerical model by performing experiments at various ceiling temperatures. Design challenges are discussed in detail. The results of this investigation offer valuable insights into the anticipated thermal comfort achievable through TE-based radiant cooling systems across various operating conditions. [ABSTRACT FROM AUTHOR]

Compared with the traditional radiant cooling combined with a displacement ventilation air conditioning system, an air conditioning system of radiant cooling combined with an attached jet can not only effectively prevent dew on the surface of the radiant cooling plate, but also further improve the cooling capacity of the radiant air conditioning system; however, most scholars have installed the radiant cooling plate on the radiant roof and the ground, and there are fewer studies on installing the radiant cooling plate on the two sides of the wall. Based on this, this paper builds an experimental system of radiant air conditioning and conducts experiments on summer working conditions in June–October to experimentally study the indoor thermal and humid environments and thermal comfort under different water supply temperatures when radiant cold panels are installed in single-side-wall, symmetrical-wall, and top-panel positions. The experimental results show that the optimal water supply temperatures of single-side-wall radiation combined with an attached-jet air conditioning system, symmetrical-wall radiation combined with an attached-jet air conditioning system, and roof radiation combined with an attached-jet air conditioning system are 18 °C, 22 °C, and 16 °C, respectively, and at the same time, the temperatures of the human body's working area under the above water supply temperatures are 26 °C, 26.3 °C, and 26.4 °C, respectively. The average humidities in the working area are 58%, 53%, and 57%, which can meet the requirements of our country's level II comfort when the indoor heat and humidity environment is stable, the energy consumption amounts of the radiant end are 5.71 kW·h, 3.99 kW·h, and 10.81 kW·h, respectively, and the highest efficiency of cooling and dehumidification is achieved with the symmetric-wall radiation combined with the adherent-jet air conditioning system. [ABSTRACT FROM AUTHOR]

In the current context of joint efforts towards the decarbonisation of buildings, integrating occupants' comfort and health with latest technological advancements for energy efficiency is at the center of the latest development of research, policies and professional practice. Radiant systems are encountering great success since the low-thickness systems can also be used in renovation projects for both heating and cooling, while guaranteeing optimal comfort. However, dehumidification is often required for optimal radiant cooling operation with no condensation risks, and the great potential of mechanical ventilation systems to optimally address the needs for dehumidification, air renewal, health and energy efficiency appears to be far from its full exploitation in the post-COVID-19 era. The present paper aims at providing a quantification of the energy and financial impacts of the implementation of a controlled mechanical ventilation system (CMV) coupled to a radiant system in a typical residential case study building in Italy. The results show that the sole CMV may decrease primary energy demand and energy costs by more than 30% and contribute to an increase in the smart readiness of the building by 8%, but further incentive policies must be developed to cover the still high investment and maintenance cost. [ABSTRACT FROM AUTHOR]

The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings' energy use patterns globally. The updated energy technology perspectives highlight the need for innovative cooling systems to address this growing cooling demand. Phase change material embedded radiant chilled ceiling (PCM-RCC) has lately acquired popularity as they offer more efficient space cooling together with further demand-side flexibility. Recent advancements in PCM-RCC applications have increased the necessity for reliable simulation models to assist professionals in identifying improved designs and operating settings. In this study, a transient simulation model of PCM-RCC has been developed and validated using measured data in a full-scale test cabin equipped with newly developed PCM ceiling panels. This model, developed in the TRNSYS simulation studio, includes Type 399 that uses the Crank-Nicolson algorithm coupled with the enthalpy function to solve transient heat transfer in PCM ceiling panels. The developed model is validated in both free-running and active operation modes, and its quality is then evaluated using several validation metrics. The results obtained in multiple operating scenarios confirm that the model simulates the transient behaviour of the PCM-RCC system with an accuracy within ±10%. Aided by this validated model, which offers the user detailed flexibilities in the system design and its associated operating schemas, PCM-RCC's potentials regarding peak load shifting, energy savings, and enhanced thermal comfort can be investigated more reliably. [ABSTRACT FROM AUTHOR]

For radiant cooling to maintain equivalent comfort conditions as all-air cooling it must remove more heat from a space, the peak space heat extraction rate must be larger, and the peak must occur earlier. In this article, we assess how the magnitudes of these differences are influenced by heat gain characteristics and by the use of natural ventilation night precooling. We present measurements from a series of multi-day side-by-side comparisons of radiant cooling and all-air cooling in a pair of experimental testbed buildings, with equal heat gains, and maintained at equivalent comfort conditions. In a five-day experiment with mixed internal heat gains, solar gains, and natural ventilation night precooling, radiant cooling had to remove 35% more heat than the all-air system in equivalent circumstances; and the peak heat extraction rate was 20% larger (median difference on multiple days). In a similar experiment with highly convective internal gains the differences were smaller (26% more thermal energy, 12% larger peak), while in an experiment with highly radiant gains the differences were larger (40% more thermal energy, and 21% larger peak). The differences were much smaller in an experiment without natural ventilation night precooling (7% more thermal energy, 5% larger peak). These findings have consequences for the choice, design, and control of mechanical cooling systems, especially in buildings that also use passive cooling strategies such as natural ventilation night precooling.

At present, radiant cooling technology is more and more widely used in building energy conservation, but the condensation problem still restricts the further promotion of radiant cooling technology. The ceiling radiant cooling panel with the sealed air layer was found to effectively eliminate the inhomogeneity of the surface temperature of the radiant plate by a recent study, resulting in a decent anti-condensation ability. The heat transfer analysis of the ceiling radiation cooling panel with the sealed air layer was carried out, and a mathematical heat transfer model was established and verified by an orthogonal experiment. Then, the experimental results and calculation results were compared and the heat transfer performance of the radiant plate under different parameters was discussed. The results show that the cooling capacity per unit area of the radiant panel can reach 136. 47 W/ m 2, and the surface temperature uniformity of the ceiling radiation cooling panel can reach 98. 4%, which proves that the radiant panel has superior cooling performance, uniform surface temperature and remarkable anti-condensation ability. [ABSTRACT FROM AUTHOR]

Radiant cooling is highly energy efficient and provides excellent thermal comfort; however, owing to the large area required, it has primarily been applied to indoor space cooling. In this study, a low-temperature condensation-free radiant cooling panel (RCP), proposed in a related paper (Part 1: Design process and feasibility evaluation with performance test), was applied to an actual vehicle to study its effect and impact on thermal comfort. Thermal satisfaction and sensation were assessed using a subjective survey, and skin temperature was investigated using objective measurements in 17 participants. The results showed that the proposed RCP provided the passengers with better thermal comfort under solar radiation; furthermore, 95 % of participants found it more satisfying when the RCP was turned on, and the overall thermal sensation vote tended to be neutral (0) from warm (2) after operating the RCP for 5 min. In addition, thermal sensation in the head and upper body had a major effect on the overall thermal sensation, whereas thermal sensation in the lower body was of no importance to the overall thermal sensation. The RCP used in this study can maximize the energy-saving effect through local cooling, particularly in vehicles with large spaces. [ABSTRACT FROM AUTHOR]

Buildings are responsible for over a third of energy consumption worldwide, particularly due to the increasing demand for air-conditioners in response to the more extreme heat around the globe. It is imperative to move towards more energy-efficient space cooling alternatives. The integration of phase change material (PCM) with radiant chilled ceilings (RCC) is a promising technology due to its benefits regarding energy efficiency and indoor environmental quality. This article presents a field study conducted on a newly-developed PCM embedded radiant chilled ceiling (PCM-RCC) installed in a stand-alone cabin located in Melbourne. The study evaluates the thermal and energy performance of the system through investigations of the transient thermal behaviour of PCM panels in charging-discharging cycles, the indoor comfort conditions, and the electricity peak demand. It was observed that the proposed PCM-RCC can provide satisfactory comfort conditions and contribute to load shifting if a refined operating strategy is applied. The efficiency of PCM recharge overnight depends on several factors that need to be carefully considered in design. The challenges related to the implementation of optimal operating dynamic schedules in response to the thermal behaviour of PCM-RCC, and accurate weather forecasting should be addressed to realise the full potential of this technology.

Today, it is common to use thin-layer nanocomposite coatings as insulation to reduce heat loss through building walls. One of the important advantages of these coatings is preventing energy loss as a thermal barrier in low thicknesses and with high efficiency. Investigations on the energy loss and saving of coated buildings are often practiced using numerical and experimental approaches. In this study, numerical simulation and experimental evaluation consisting of modification of nanoparticles and preparation powder coating nanocomposite, are used to study the effects of coated polyurethane nanocomposite containing nano Al2O3 and nano ZrO2 on both sides of the walls of a sample room on temperature distribution and heat transfer. For this purpose, a three-dimensional enclosure was assumed as a room having a radiant cooling panel, which is modeled under various features of the walls' interior and exterior coating. To determine the flow and temperature fields, the governing equations that include the continuity, momentum, turbulence, and energy equations, which are coupled through the buoyancy term, have been solved using the Fluent software. The SIMPLE algorithm to accommodate the pressure-velocity coupling, the k-ε model for turbulence modeling, the Boussinesq approximation for buoyancy term modeling, and the DO model for radiation simulation, are employed. The results of the thermography of the samples showed that the temperature reduction in the samples containing zirconium oxide compared to aluminum oxide had a better performance in the thermal insulation of the coating and the lowest temperature was observed in the nanocomposite containing 3% zirconium oxide. Numerical studies showed that this thin layer nanocomposite coating reduces energy consumption by 4% and 13%, respectively, compared to pure polyurethane coatings and acrylic paints.

Radiant cooling systems extract heat from buildings differently than all-air cooling systems. These differences impact the time and rate at which heat is removed from a space, as well as the total amount of thermal energy that a mechanical system must process each day. In this article we present measurements from a series of multi-day side-by-side comparisons of radiant cooling and all-air cooling in a pair of experimental testbed buildings, with equal heat gains, and maintained at equivalent comfort conditions (operative temperature). The results show that radiant cooling must remove more heat than all-air cooling – 2% more in an experiment with constant internal heat gains, and 7% more with periodic scheduled internal heat gains. Moreover, the peak sensible space heat extraction rate for radiant cooling (heat transfer at the cooled surface, not the cooling plant) must be larger than the peak sensible space heat extraction rate for all-air systems, and it must occur earlier. The daily peak sensible space heat extraction rate for the radiant system was 1–10% larger than for the all air system, and it occurred 1–2 hours earlier. These findings have consequences for the design of radiant systems. In particular, this study confirms that cooling load estimates for all-air systems will not represent the space heat extraction rates required for radiant systems.

Radiant cooling and heating have the potential for improved energy efficiency, demand response, comfort, indoor environmental quality, and architectural design. Many radiant buildings have demonstrated outstanding performance in these regards. However, there are no well-established best practices for design of radiant buildings and their control systems, and most industry professionals are unfamiliar with radiant systems. This study summarizes interviews with eleven professionals with substantial experience with design and operation of radiant buildings in North America. Interviews focused specifically on high thermal mass radiant buildings, referred to as thermally active building systems (TABS). Interviews revealed a diverse range of approaches for design and control of TABS buildings. While interviewees expressed many similar approaches, they also have manyunique preferences. Examples of consistent themes include the use of dedicated outdoor air systems for ventilation and for supplemental cooling, and the use of a relatively simple control schemes that target a constant slab temperature for all times of the day and night. However, interviewees described unique preferences for space types where TABS should be applied, design and types of valves or pumps used for radiant zone control, the control of changeover between slab heating to slab cooling, and many other design considerations. Preferences appear to be driven by project constraints and by personal experience. Interviewees report that their design preferences are effective, but there is no industry consensus about how alternatives compare for energy performance. This paper outlines opportunities for further research, improvement radiant design and control, and the development of best practices.

Decoupled radiant cooling units (DRCUs) are capable of increasing the cooling capacity without increasing condensation risks even using a much lower cooling temperature than conventional radiant cooling units (CRCUs). However, it is unclear whether DRCUs using low radiant cooling temperature will increase the cooling load of the conditioned indoor spaces. In this study, the cooling load characteristics of a thermal chamber conditioned by a DRCU was investigated through developing a steady-state analysis model suitable for both DRCUs and CRCUs. The total/radiative heat flux, as well as the heat exchange with a thermal manikin and walls were analysed under different surface temperatures of DRCUs. The effect of the emissivity of the thermal chamber' external wall on the cooling load was also investigated. Results indicated that the cooling load under the DRCU was slightly smaller than that under the CRCU when the same operative environment was created. Decreasing the infrared emissivity of the exterior wall's inner surface could lead to a significant decrease in the cooling load for both the DRCU and CRCU. By decreasing the wall emissivity from 0.9 to 0.1, the total cooling load of the DRCU can be decreased by 8.4% and the heat gain of the exterior wall decreased by 21.6%. This study serves as a reference for developing the analysis model and understanding the load characteristics when DRCUs are used to create the thermal environment for indoor spaces. [ABSTRACT FROM AUTHOR]

Evaporative cooling, using cooling tower systems, has the potential to offer an alternative approach for producing high temperature chilled water, particularly for buildings located in temperate climates. The current paper examines the performance of an integrated cooling system, where an open forced draught counter flow cooling tower is used for the provision of chilled water for a radiant cooling and displacement ventilation system. For this purpose, a low temperature low approach direct evaporative cooling tower is used which can provide cooling water with low approach temperatures (1-3 K), which defines the temperature difference between the tower water outlet temperature and ambient wet bulb temperature. The performance of the proposed cooling system has been investigated for internal buildings loads up to 66 W·m-2 in order to examine the limitations of the cooling system. Space thermal comfort conditions and system performance metrics were assessed for four different temperate climate types as follows: cool and dry (Helsinki), cool and semi-humid (Birmingham), warm and dry (Prague), and warm and humid (Paris). The assessment shows that for the proposed system, where a radiant floor was used, can provide acceptable thermal comfort conditions for approximately 80% of the occupant hours over the respective cooling seasons. [ABSTRACT FROM AUTHOR]

Efficient cooling and heating solutions for nearly zero-energy solar dwellings are required to mitigate climate change and to make dwellings sustainable. The installed pipeline for a radiant heating system, which is only used for space heating when heating is necessary, can also be used to cool the room with only the enthalpic use of natural city water by releasing the natural city water through the embedded pipeline already installed for radiant heating. Natural city water used for radiant cooling can be used in necessary locations such as for toilets, washing cars, laundry facilities, and garden water, which corresponds to approximately 56% of the water we use at home. As a result, the embedded pipes that make up a radiant heating system can be converted to a passive intelligent radiant cooling system with minimal added installation and control systems. Thermal comfort and behavior analyses in an enclosure with a radiant cooling system are fulfilled through experimentation, mean radiant temperature simulation, and asymmetric radiation calculation. No uncomfortable asymmetric radiation is encountered during the cooling period, so the cooling spaces are well controlled within the comfortable cooling range. A passive intelligent radiant cooling system that uses just the enthalpy of natural city water can be an appropriate ecological solution to better develop zero-energy dwellings. No extra cooling energy and power are required to cool a space that uses just enthalpy and pressure from natural city water. [ABSTRACT FROM AUTHOR]

Compared with the traditional radiant cooling combined with a displacement ventilation air conditioning system, an air conditioning system of radiant cooling combined with an attached jet can not only effectively prevent dew on the surface of the radiant cooling plate, but also further improve the cooling capacity of the radiant air conditioning system; however, most scholars have installed the radiant cooling plate on the radiant roof and the ground, and there are fewer studies on installing the radiant cooling plate on the two sides of the wall. Based on this, this paper builds an experimental system of radiant air conditioning and conducts experiments on summer working conditions in June–October to experimentally study the indoor thermal and humid environments and thermal comfort under different water supply temperatures when radiant cold panels are installed in single-side-wall, symmetrical-wall, and top-panel positions. The experimental results show that the optimal water supply temperatures of single-side-wall radiation combined with an attached-jet air conditioning system, symmetrical-wall radiation combined with an attached-jet air conditioning system, and roof radiation combined with an attached-jet air conditioning system are 18 °C, 22 °C, and 16 °C, respectively, and at the same time, the temperatures of the human body’s working area under the above water supply temperatures are 26 °C, 26.3 °C, and 26.4 °C, respectively. The average humidities in the working area are 58%, 53%, and 57%, which can meet the requirements of our country’s level II comfort when the indoor heat and humidity environment is stable, the energy consumption amounts of the radiant end are 5.71 kW·h, 3.99 kW·h, and 10.81 kW·h, respectively, and the highest efficiency of cooling and dehumidification is achieved with the symmetric-wall radiation combined with the adherent-jet air conditioning system.

The article summarizes the results of the 25-year time horizon performance analysis of the ground source heat pump that serves as a heat source in a detached house in the climatic conditions that prevail in Wrocław, Poland. The main aim is to assess the potential of ground regeneration and reduction of CO2 emission by passive cooling application. The study adds value to similar research conducted worldwide for various conditions. The behavior of the lower source of the heat pump was simulated using EED software. The ground and borehole properties, heat pump characteristics, heating and cooling load, as well as the energy demand for domestic hot water preparation have been used as input data. Based on the brine temperatures for all analyzed cases including the ground with lower and higher values of conductivity and heat capacity, the borehole filler of inferior and superior thermal properties, and the passive cooling option turned on and off, the seasonal efficiencies of the heat pump have been calculated. The energy and emission savings calculations are based on the values obtained. The application of passive cooling reduces the brine temperature drop by 0.5 K to over 1.0 K in consecutive years in the analyzed cases and the thermal imbalance by 65.0% to 65.9%. Electric energy savings for heating and domestic hot water preparation reach 4.5%, but the greatest advantage of the system is the possibility of almost emission-free colling the living spaces which allows reducing around 33.7 GWh of electric energy and 1186–1830 kg of CO2 emission for cooling. [ABSTRACT FROM AUTHOR]

Condensation risk has limited the deployment of radiant cooling systems for improving thermal comfort in hot and humid climates. Infrared-transparent membrane films emerged as a viable alternative to improve hybrid radiant cooling by preventing moisture condensation. This case study assesses the potential of membrane-assisted radiant cooling in a rural school building in Santa Lucia, Atlántico (Colombia), a location with a hot and humid tropical climate throughout the year. The study evaluates different cooling strategies, including natural ventilation, mechanical ventilation, hybrid radiant cooling, and membrane-assisted radiant cooling using EnergyPlus® software. Results for a radiant surface temperature of 4 °C below the dew point show that membrane-assisted radiant cooling could reduce annual discomfort hours by 3–6% compared to conventional radiant cooling. Further experimental and modeling studies should focus on the lowest achievable temperature below the dew point without condensation. Our results suggest that radiant cooling with infrared-transparent membranes is a potentially cost-effective alternative for improving thermal comfort in rural school buildings in hot and humid climates.

• An outdoor cooling spot is created using membrane-assisted radiant cooling panels. • Field data of thermal performance and heat extraction rate are obtained. • The impact of environmental factors on heat extraction is analyzed. • Energy efficacy index is proposed by coupling thermal comfort and energy needed. Membrane-assisted radiant cooling systems offer a promising solution for directly cooling human bodies in outdoor settings. In this study a prototype system is experimentally assessed, which comprised of two wall-mounted panels and one ceiling-mounted panel with the cooling provided by a water chiller system. Three different radiant panel surface temperatures (T s u r =14.3°C, 17.8°C, 21.9°C) were tested to observe possible condensation and to measure the heat flux, and a thermal comfort survey was conducted in combination to analyze the system energy efficacy. The results indicate that selecting appropriate panel surface temperatures under different ambient universal thermal climate index (UTCI) conditions can not only effectively avoid energy surplus but also improve thermal comfort for people. When the ambient UTCI is 38.1°C, the panel surface temperature needs to be lowered to 14.3°C to achieve neutral thermal sensation while 333.7 W of cooling energy is required; but when the ambient UTCI is 29.9°C, a panel surface temperature of 21.9°C would suffice with a much lower energy demand. It is also concluded that the surface condensation may occur but can be controlled. This experimental study provides solid data for the further development of radiant cooling technology for open-space applications. [ABSTRACT FROM AUTHOR]

• Radiant and air systems were compared at 26 °C and benchmarked against 23 °C. • Both systems produced similar thermal conditions with a difference in air velocity. • The radiant system extracted 33% more heat from space than the air system. • At 26 °C, the radiant system consumed 4 % less energy than the air system. • 60% of participants were satisfied with the thermal environment in both systems. In an experimental study set in Singapore's tropical climate, we evaluated the thermal environmental performance, energy consumption, and thermal comfort of air and radiant cooling systems, operating at an operative and air temperature of 26 °C. 78 participants across five groups answered thermal comfort surveys in a crossover study design. Environmental performance metrics indicated that both systems produced similar conditions, with a noticeable difference in air velocity. The mean radiant temperature to air temperature difference was less than 0.5 °C in both systems. The radiant system exhibited a 33 % higher heat flux extraction than the air system and required less electrical power for the transportation of the cooling medium and ventilation air. Overall, the radiant system used 4 % less energy than the air system when controlled at 26 °C and 34 % when operated at 23 °C. Results show that radiant and air systems provided equal thermal comfort in cooling, with over 60 % of participants expressing satisfaction and ∼ 20 % voted neutral thermal satisfaction. ∼ 40 % of participants preferred cooler conditions, and ∼ 30 % desired increased air movement. [ABSTRACT FROM AUTHOR]