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Abstract

The Thermoheliodome is an experimental pavilion that explores cooling without air conditioning. The two research aims were to explore the use of indirect evaporative cooling and the geometric reflection of radiant cooling. For evaporative cooling we utilize a cooling tower outside of the pavilion to indirectly supply water chilled near the wet-bulb temperature. The radiant cooling system is made up of 55 coaxial chilled pipes each located in the central axis of cones with reflective surfaces that spectrally reflect the surface of the pipes and expand their radiant view factor to the occupants inside the pavilion. The specific geometry was digitally fabricated using an industrial robot and hot-wire foam cutter. The mean radiant temperature (MRT) was shown to be significantly decreased using thermal imaging cameras and with a novel scanning MRT sensor. The radiant cooling delivered from the fluid is maximized by reflection and concentration of heat emitted by occupants on the pipes, while the convective cooling of the air is minimized because only the small pipes are cooled and the reflecting surfaces are not, so the convective heat transfer surface area is small. Under typical indoor conditions the ratio of radiant to convective cooling is slightly greater than one, and for warm daytime conditions it was greater than 10 inside the pavilion. Occupant surveys found that although the air temperature was not modified, they felt that inside the space there is a cooling sensation (p ≤0.01). The day of the survey they felt on average 3 ° C cooler.

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... Building on the diagrams from Arens [4] and Kessling [5], this framework is the first to truly expand the air based comfort zone and graphically provide answers for how radiation can be used to compensate for any air temperature, or what is the lowest acceptable wind speed for a given metabolic rate. Probing the corners of the psychrometric chart with a heat balance can allow for creative system design, perhaps leveraging 'free' heat from evaporation [12] or return condensate [13]. In short, this tool can allow for a simple high-level analysis of the following conditions: ...
... For example, energy benefits have been demonstrated when latent loads (dehumidification) can be separated from sensible loads (cooling) [14,15], as these two processes are linked with a conventional air conditioning system yet often are very different in magnitude [16]. Similarly, radiant systems [12] and personal comfort systems [17] can help separate comfort conditioning from required ventilation air. However, recent research has shown that in buildings with radiant systems, there often exists very little separation between the air temperature and mean radiant temperature [18], failing to take advantage of the separation of ventilation and comfort loads. ...
... Yet no case of such a low mean radiant temperature for a high air temperature exists in the ASHRAE thermal comfort database II [32]. However, this does not mean that the conditions could not be designed with creative thermal systems [12,25]. Particularly with recent advances on materials for radiant cooling [33,34], there is a renewed need to understand how occupants physically interact with comfort systems to realize energy savings with air temperature setbacks [35]. ...
... One of the perspective ways to reduce the energy intensity of traditional air conditioning systems using compressor refrigeration machines is to use the thermodynamic nonequilibrium of atmospheric air as a renewable energy resource [4]. Systems using this energy to produce cold include direct and indirect evaporative air cooling [5], which can be successfully used in solar air conditioning installations. The principle of operation of solar air conditioning units [6,7] based on pre-treatment of air in an adsorption dryer and subsequent cooling of the air flow in a rotating heat exchanger and evaporative chamber (figure 1). Figure 1 shows the principle of operation of a traditional solar installation of air conditioning [8]. ...
... Outside air pre-cleaned in the filter (F) with parameters (1) is drained and heated in the sorbing nozzle of the rotor (AD) to state (2). After "dry" cooling with constant moisture content (2-3) in a rotary regenerative heat exchanger (RRHE), the air is adiabatically humidified in the evaporative chamber (EC) to state (4) and, with these parameters, the air is fed into an air-conditioned room in which it assimilates heat and moisture excess (4)(5). The exhaust air is adiabatically humidified in the evaporative chamber (5-6), and then heated (6-7) in a rotating heat exchanger. ...
... By changing the ratio of air flows 12 and 13, you can adjust both the degree of cooling of the room and the humidity in it. 5 An important condition for the continuous operation of all evaporative coolers, including the test one, is the emission of used air from the refrigerated room into the atmosphere. Otherwise, sometime after the start of the operation of the evaporative cooler, the air in the room is saturated with water vapor (as a result of continuous evaporation of water), and the cooler ceases to fulfill its main function. ...
Article
Full-text available
The article is devoted to the development of promising low-power evaporative cooling systems using solar energy. At the same time, the placement of elements of the system in determining the temperature, the humidity of the air in such indoor areas is determined by the parameters at which the most favorable conditions for the optimal climate in the room are created. The article presents the structural and thermodynamic parameters of the developed two-stage evaporative cooler air. The creating two-stage evaporative cooling installation is shown the efficiency and effectiveness of the cooling air. Given preliminary studies where study the possibility of indoor climate and presented their results. Requirements to ensure the indoor climate. The test evaporative air cooler with rotated regenerative heat exchanger has a design air capacity of 160 m ³ / h and 200 W in the cold, it provides for an independent change in the rotation speed of heat exchangers, a change in the amount of sprayed water. The total consumed electric power is not more than 45 watts. Achieved cooling 7°C at an ambient temperature of 35÷40°C (July-August 2019).
... Knowing the room geometry and fixing the thermographic image could be a solution to the issue of calculatimg exact view factors. New tools [99,100] have been used to provide spatially resolved thermal geometries, creating point clouds with each point tagged with a temperature, measured with a thermopile. The scans from this device, known as the SMART sensor, allow the creation of MRT maps of an environment from a single scan. ...
... Researchers have also arranged 8 thermopiles on the vertices of a cube to measure the average temperature of each direction [100], which can then all be averaged to provide an overall point average. The thermopiles are not sensitive to convection, as they measure internal temperature to convert the radiant flux measured about the sensing array with Equation (2) to extract the surface temperature in a 90°field of view. ...
... Still, a precise measurement of MRT is a fundamental requirement of understanding and predicting how occupants feel in an environment [135] and in extracting maximal efficiency from thermal systems [58]. Recent attempts to provide spatially resolved measurements from thermal point clouds with the SMART sensor and a simpler cube sensor [99,100,136] begin to automate the process of extracting real-time MRT information for control of radiant systems. ...
... However, cooling load was highly dependent on internal gains. Meggers et al. (2017) adopted radiant cooling and indirect evaporation for "air conditioning", they found that although air temperature was not changed, there was a cooling sensation in the experimental building. Mikeska et al. (2017) conducted that wall radiant cooling system was able to provide cooling power at 29 W/m 2 and 59 W/m 2 of floor area with cooling water temperatures between 21.5 °C and 18.5 °C, resulting in room air temperatures between 25 °C and 22 °C. ...
... Also, based on our previous research (Zhou et al. 2016), both annual cooling energy consumption and indoor air relative temperature fluctuation rate could be reduced by 4.53% and 56.2% via being fabricated with active radiant cooling system. The radiant cooling wall has also been validated in terms of reducing local thermal discomfort with reduced vertical air temperature difference (Le Dréau et al. 2015;Meggers et al. 2017;Mikeska et al. 2017). To the author's knowledge, no paper specifically related to the construction and operation of double PCM wallboards for overheating mitigation, natural cooling energy storage efficiency improvement, and energy saving of radiant cooling wall has been published in the scientific literature. ...
Article
This study aims to evaluate thermal performance of a new ventilated Trombe wall integrated with phase change materials (PCMs-VTW). Double PCM wallboards are embedded in the building facade for different purposes, i.e. exterior PCM wallboard is to store natural cooling energy via night-time ventilation, and interior active PCM wallboard is for radiant cooling. Melting temperature and latent heat of PCM have been discussed for PCMs-VTW system from 1st August to 7th August in Changsha, China. Also, high-reflective coating is coated on the exterior PCM wallboard for reflecting solar radiation, thus ameliorating daytime overheating. Nighttime ventilation is for natural cooling energy storage via regenerating solid exterior PCM wallboard. The obtained result shows that under the weather condition in Changsha, melting temperature 22 °C for interior PCM and the latent heat 176 kJ/kg for exterior PCM show considerable benefit for cooling energy release. Compared with the classical Trombe wall system, annual cooling energy consumption is decreased by 20.8% and by 18.6% in the PCMs-VTW system when indoor air temperature is kept at 22 °C and 24 °C respectively. Our research has provided scientific evidences for potentials provided by PCMs-VTW system in reducing building energy consumption and improving indoor thermal comfort via exploiting natural cooling energy, mitigating overheating at summer condition and utilizing cold sources in high temperature.
... Refrigeration needs to impact all areas of people's lives and production activities and so the demand for cooling and air conditioning is increasing worldwide [1][2][3] . Concern about conventional cooling systems based on vapor compressors are also mounting as they consume large amounts of electricity and their refrigerants can often be harmful to the environment [4][5][6] . ...
... Chen). 1 These authors contributed equally to this work ing daytime and under sunlight, the heat loss to the cold sky is substantially larger than heating from sunlight if both of averaged solar reflectance ( R solar ) in the solar spectrum and averaged thermal LWIR emittance ( ε LWIR ) should be high enough or at least > 0.9 in the practical sub-ambient cooling applications [14][15][16][17] , such as: water cooling [18] , electric generation [ 19 . 20 ], and water collection [ 21 , 22 ]. ...
Article
Passive daytime radiative cooling (PDRC) is an electricity-free cooling technology that has received great interest for its' environmental benefits. Current organic polymer PDRC materials often require harmful organic solvents for dispersion and inorganic dielectric PDRC materials require costly vacuum processing or have poor flexibility and water-repellence. In addition, most PDRC applications focus on refrigeration at sub-ambient temperatures using a selective emittance spectrum. Here a scalable aqueous-based processing method utilizing commercially available hollow dielectric microspheres is reported to create dielectric PDRC coatings with broadband emittance spectra for the heat dissipation of outdoor devices used above-ambient temperatures. A high solar reflectance and thermal infrared emittance of 0.93 at a thickness of 500 μm can be achieved due to the multi-interface reflectivity between the dielectric material and air in the hollow stacked microspheres. The max temperature (∼ 46 °C) of the outdoor device at a heat density of 50 0 0 W m −2 can drop 20 °C at a solar intensity of ∼ 925 W m −2 compared to an Al metal wall (∼ 66 °C), which is only 4 °C higher than the ambient temperature of 42 °C. More importantly, the aque-ous paint does not require any volatile organic compounds and has great stability, water repellence, and excellent flexibility.
... Recently, Meggers et al. (2017) presented the concept of their Thermo-heliodome, an experimental pavilion located at Princeton University that 'cools without air conditioning'. The system operates using indirect evaporative cooling (a nearby evaporative tower supplies water chilled to nearly wet-bulb temperature) and radiant cooling panels with chilled pipes. ...
... As in the reported studies in the introductory section of this paper, particularly in Meggers et al. (2017), participants were able to perceive a superior performance of the passive environment despite negligible differences in air temperature in the rooms evaluated and relatively small differences in Tmrt. ...
Conference Paper
An experimental study compared the thermal response of subjects in two test rooms, one of which was cooled by a roof pond coupled to radiant cooling panels and the second by a conventional split AC unit. Measurements of the surface temperatures indicated that structural cooling and thermal stabilization were obtained in the roof pond room, whereas in the air-conditioned room thermal control was achieved only within the short period of the session through air temperature changes. For similar air temperature, there was a slight preference for the roof pond room, which had a lower Mean Radiant Temperature. The roof pond room was found to be more effective in ensuring comfort conditions continuously and without occupant intervention.
... Such a design would allow for a large thermal gradient to exist between the effective mean radiant temperature of panel's cold surface, as experienced by the human body, and the ambient environment it interacts with. Radiant cooling systems are more efficient at providing sensible cooling to building occupants, compared to air-based systems, since they allow for large air temperature setbacks ( Meggers et al. 2017). Applications of radiant cooling enable building operators to increase indoor air set-point tempera- tures, yielding direct energy savings (Hoyt, Arens, and Zhang 2015). ...
... However, should one wish to construct full 2-D or 3-D heat transfer models based on the empirical data provided, one issue should be noted. The FTIR data measured at orthogonal angles of incidence is sufficient for only certain, special geometric con- figurations, such as an outdoor spherical dome for thermal com- fort ( Meggers et al. 2017). For typical building interiors, where flat radiant 'chilled ceiling' panles would be expected, shal- lower angles of incidence are typical. ...
Article
In this study, we enhance the understanding and design of a radiant cooling technology for outdoor comfort in tropical climates, originally proposed by R.N. Morse in 1963, in this journal. We investigate a type of radiant cooling methodology whereby the cold temperature source is physically separated from the outdoor environment by an insulated enclosure using a membrane transparent to infrared radiation. The enclosure isolates the radiant cooling surface from ambient conditions, allowing the radiant surface to be cooled significantly below ambient dew point temperatures without incurring condensation. For this new study, a Fourier Transform Infrared (FTIR) Spectroscopy analysis on three candidate membrane materials is undertaken and a prototype experimental test panel is fabricated. Our study shows that for a 5 °C chilled panel temperature, the exterior membrane surface temperature reaches 26 °C in a 32 °C / 70% RH environment resulting in an effective mean radiant temperature of 15.8 °C. These results provide new evidence in support of Morse’s original proposal, that such panels could provide significant radiant cooling without condensation in humid environments. Radiant cooling products based on the studied technology may offer an ability to provide thermally comfortable conditions in hot environments without the energy required for dehumidification.
... Their conspicuousness has been codified by the ubiquitous use of the psychrometric chart as a tool for delineating a "comfort zone" based on these two variables alone. This is the result of a historical bias stemming from the prominence of air conditioning as control systems in buildings (Teitelbaum, 2017). ...
... Fanger assumed that the body strives towards thermal equilibrium between the heat it generates through metabolism, consumes through work and transfers to its environment. Fanger described the total amount of heat that must be removed in order to maintain homeostasis as the thermal load, L, according to Equation 6 (Teitelbaum, 2017). The first psychrometric diagram was published by Willis Carrier in 1911(Carrier 1911. ...
Thesis
The geometric and material characteristics of heat transfer at the scale of a building tie together the disciplines of architecture, engineering, and physics. However, contemporary practices create knowledge siloes that prevent a full leverage of the many potential trajectories for thermal energy flows in the built environment. Architects have spent the past decades developing multiple tools to describe and construct increasingly complex forms of building surfaces and volumes, yet have largely overlooked the impact of such design decisions on surface radiation and volumetric airflow. At the same time, engineers have developed and employed internal climatic control systems for buildings, but those most commonly reside hidden within mechanical rooms, plenums and shafts, detached from the building’s materiality and form, as well as from the external climatic forces. However, it is not sufficient to simply expose these existing systems to sight. Bridging these fields requires an integrated view of the building itself as a coordinated machine which regulates the transfer of heat from the human body to the external environment. In order to achieve this goal, several methods to characterize the dependencies of heat transfer on architectural elements are presented. Measurement, analysis, and simulation tools are developed to reveal the quantities and qualities of invisible energy exchanges. A special emphasis is given to radiant heat transfer, which is intrinsically connected to the geometry of architectural surfaces. Once characterized, it is possible to productively design the paths of energy flows through buildings, thus reducing their reliance on mechanical systems and external energy supply. A series of prototypes is constructed to test the interaction of heat and architectural form in full scale. These prototypes include experimental pavilions magnifying the influence of radiant heat fluxes on human occupants, and various designs for a roof aperture that combines radiant and evaporative cooling for desert climate through kinetic envelopes and adaptive materials. Sensor measurements taken from the prototypes are used to analyze their performance within their intended environments. This work is meant to demonstrate how the design field can contribute to the pressing need for energy conservation, and reciprocally, how the inclusion of thermodynamic interactions within the design process may enrich the pallet of the architect with generative formal and material strategies.
... However, radiant cooling panel systems also have limitations as well [1,2,9,[15][16][17][18][19][20][21][22][23][24]. First, a radiant cooling system is challenging owing to a risk of moisture condensation, for example, when a room is exposed to high internal moisture gains (e.g., due to the generation by an occupant, boiling water and the washing of a floor), high moisture infiltration from outside (e.g., due to rain, or hot and humid weather), and high humidity gains causing moisture condensation on the surface of the radiant cooling panels. ...
Article
A conventional radiant panel system offers advantages in terms of energy savings; however, compared with an all-air system, it has limitations such as moisture condensation risk, slow air movement, difficult space zoning, slow air pollutants removal from a highly polluted room, and time delay in start-up of the radiant panel system. This research performs an energy consumption analysis of a hybrid radiant cooling system for buildings in summer. The hybrid radiant cooling system combines a typical radiant panel with a decentralized air convector connected in series. The hybrid radiant panel system generates additional cooling output through its air convector, dehumidifies indoor air, increases indoor air movements, and reduces the time delay in start-up and a filter in the air convector removes air pollutants. This study exhibits the energy performance of the hybrid radiant cooling system compared with an all air system and a typical radiant panel system via numerical modeling using experimental data. This hybrid radiant panel system is effective for energy-saving, because it has a higher cooling impact ratio, and larger coefficient of performance of the chiller, and because the air movement increases the offset effect of the operation indoor temperature rise by an enhanced mixed convection effect. Thus it can reduce cooling energy consumption. The hybrid radiant cooling system can be used very effectively for saving energy in the summer season.
... Survey studies show that the exergy analysis has been applied on the building envelope [46,47], cooling system [48], heat pumps [49,50], energy storage systems [51] and HVAC [52] to improve the thermal performance. ...
Article
The building sector is the major energy consumer, accounting for over 40% of global energy demand. Heating and cooling together with domestic hot water energy consumption are estimated to account for 60% of the required energy for buildings’ maintenance and operation. Energy recovery is a suitable technique to tackle high energy consumption in the building. In this study, a new layout of heat recovery units installation (i.e., primary and secondary) is investigated. The main objective of this study is to reduce energy consumption in an air handling unit through the exergy analysis. Owing to adding heat recovery units, cooling and heating coil loads reduced by 7.8% and 43%, which in turn decreased the total required load of AHU by 17.84%. From the viewpoint of the second law and based on the results, incorporating the primary and secondary heat recovery units into the base AHU in hot and dry climate regions led to decrease in the total irreversibility up to 26.29%, while in hot and humid climate this figure is 14.25%. Consequently, the positive effect of using heat recovery units in the hot and dry climate region is superior to the hot and humid one.
... In this paper, the simulation of the thermal behaviour of a parabolic reflector, directing radiant flux from a hot or cold pipe will be discussed. Beyond the scale of a single heat reflector, the Thermoheliodome project (Meggers et al, 2017) provides an example of a constructed demonstrator of reflective expansion of radiant heat transfer. The project provided cooling to occupants through the reflection of thermal radiation emitted from chilled pipes using conical concentrators to provide cooling without conditioning the air. ...
Conference Paper
Full-text available
The inherent geometric and material dependence of radiant heat transfer can be leveraged to improve system efficiency and thermal comfort. Unlike in air-based systems, non-uniform temperature distribution can be highly controlled and beneficial in radiant systems, where temperature perception can be manipulated locally. An experiment was devised with the aim of creating a significant temperature gradient in a single space by using radiant heat transfer to cool certain parts of a room while simultaneously heating other parts. This was achieved by inducing radiant fluxes from hot and cold emissive pipes and directing them at different areas of the room through the use of curved infrared reflective surfaces. A 3D simulation was created to analyze the consequences of such a configuration for the Mean Radiant Temperature (MRT). The simulation utilizes a ray-tracing technique to account for multiple reflection bounces. The results are compared to MRT measurements taken in the physical experiment using Black Globe Thermometers. A simulation study of the heat transfer characteristics of a single pipe in a parabolic trough is also discussed.
... We believe modern electronic devices are now so inexpensive that it is appropriate to rethink whether multiple devices or the use of thermal imaging cameras can enable a better measurement of radiant heat transfer in space than the common globe thermometer. We have proposed several such devices in our previous work measuring radiant environments [54][55][56] . ...
Article
Full-text available
It is widely accepted that most people spend the majority of their lives indoors. Most individuals do not realize that while indoors, roughly half of heat exchange affecting their thermal comfort is in the form of thermal infrared radiation. We show that while researchers have been aware of its thermal comfort significance over the past century, systemic error has crept into the most common evaluation techniques, preventing adequate characterization of the radiant environment. Measuring and characterizing radiant heat transfer is a critical component of both building energy efficiency and occupant thermal comfort and productivity. Globe thermometers are typically used to measure mean radiant temperature (MRT), a commonly used metric for accounting for the radiant effects of an environment at a point in space. In this paper we extend previous field work to a controlled laboratory setting to (1) rigorously demonstrate that existing correction factors used in the American Society of Heating Ventilation and Air-conditioning Engineers (ASHRAE) Standard 55 or ISO7726 for using globe thermometers to quantify MRT are not sufficient; (2) develop a correction to improve the use of globe thermometers to address problems in the current standards; and (3) show that mean radiant temperature measured with ping-pong ball-sized globe thermometers is not reliable due to a stochastic convective bias. We also provide an analysis of the maximum precision of globe sensors themselves, a piece missing from the domain in contemporary literature.
... O resfriamento radiante gerou uma porcentagem maior de votos de conforto, embora as condições térmicas fossem equivalentes. Recentemente, Meggers et al. (2017) apresentaram estudo com voluntários em pavilhão experimental semi-fechado com sistema de resfriamento evaporativo indireto e painéis radiantes (PR) com serpentinas resfriadas. Em um dia de verão, embora as temperaturas internas e externas do ar fossem similares, a maior parte dos participantes estimou temperaturas internas inferiores às externas. ...
Article
Full-text available
Tetos-reservatório (TR) podem colaborar para obtenção de condições térmicas confortáveis, particularmente em edificações térreas. Possibilitam resfriamento ou aquecimento estrutural e estabilização das temperaturas superficiais e do ar. Uma alternativa para melhorar o desempenho do TR é acoplá-lo a painéis radiantes. Atualmente, há escassez de pesquisas enfocando a percepção térmica de usuários em ambientes fechados condicionados por TR. O objetivo desta pesquisa foi verificar, empiricamente, para condições de verão, a percepção térmica de voluntários em um ambiente condicionado por painéis radiantes acoplados a TR. Buscou-se também identificar qual modelo adaptativo melhor representaria os votos declarados pelos participantes do estudo. Como parâmetros para análise das percepções térmicas reportadas, adotaram-se o modelo PMV e os modelos para edificações passivas das normas Standard 55 e EN 15251. O experimento ocorreu em uma edificação-teste da Ben-Gurion University of Negev, em Israel. Foram consideradas respostas de 46 voluntários. O ambiente dotado de TR foi percebido como confortável pela maior parte dos voluntários. As respostas subjetivas apresentaram maior concordância com os modelos PMV e da EN 15251 do que com o modelo da ASHRAE.
... Embora as condições térmicas fossem equivalentes, o resfriamento radiante gerou uma porcentagem maior de votos de conforto. Meggers et al. (2017) apresentaram um estudo com voluntários em um pavilhão experimental semifechado com sistema de resfriamento evaporativo indireto e painéis radiantes (PR) com serpentinas resfriadas. Em um dia de verão, embora as temperaturas internas e externas do ar fossem similares, a maior parte dos participantes estimou temperaturas internas inferiores às externas. ...
Article
Full-text available
Among the components of a passive building, the roof is particularly important for the regulation of internal thermal conditions. Among the passive cooling systems that act from the roof, we can mention the roof pond (RP). In turn, radiant panels that use water as fluid can achieve high energy efficiency, enhancing the performance of the cold supply source. However, studies on the joint application of these technologies are lacking. This research study aimed to evaluate the thermal performances of different RP configurations, with and without radiant panels, applied to a test building during the summer. The experiment took place at the Sde Boqer Campus, Ben-Gurion University of Negev, Israel. The test environment with a conventional local roof was used as a parameter for comparison. The thermal performance was evaluated using Standard 55 and EN 15251, stabilisation of internal temperatures, and cooling. Compared to the conventional roof, the RP presented good results in terms of the moderation of the thermal conditions of the test building, especially when considering the European standard EN 15251.
... Yu et al. [27,28] proposed a novel system combining natural ventilation with diffuse ceiling inlet and thermally activated building systems (TABS) and investigated its cooling performance experimentally in Denmark, which has a relatively cold climate even in summer, and hence the condensation issue on the TABS was not considered. Meggers et al. [29] experimentally analyzed the thermal comfort of an open air pavilion using radiant cooling and indirect evaporation under the temperate climate of Princeton. Vangtook and Chirarattananon [30] employed water cooled by a cooling tower for radiant cooling and found that it was sufficient to achieve thermal comfort in night-time application, while the ventilation air precooled by chilled water at 10 • C was required to treat the latent load in day-time application. ...
Article
Full-text available
A hybrid cooling system which combines natural ventilation with a radiant cooling system for a hot and humid climate was studied. Indirect evaporative cooling was used to produce chilled water at temperatures slightly higher than the dew point. With this hybrid system, the condensation issue on the panel surface of a chilled ceiling was overcome. A computational fluid dynamics (CFD) model was employed to determine the cooling load and the parameters required for thermal comfort analysis for this hybrid system in an office-sized, well-insulated test room. Upon closer investigation, it was found that the thermal comfort by the hybrid system was acceptable only in limited outdoor conditions. Therefore, the hybrid system with a secondary fresh air supply system was suggested. Furthermore, the energy consumptions of conventional all-air, radiant cooling, and hybrid systems including the secondary air supply system were compared under similar thermal comfort conditions. The predicted results indicated that the hybrid system saves up to 77% and 61% of primary energy when compared with all-air and radiant cooling systems, respectively, while maintaining similar thermal comfort.
... In addition, Xu, Hong, Mi, and Yan (2018) found that pavilions are windproof measures in urban parks that help slow wind speed and improve thermal comfort. Meggers et al. (2017) designed an experimental pavilion to explore indirect evaporative cooling usage and radiant cooling geometric reflection. The study used thermal imaging cameras and a novel scanning MRT sensor and found that the mean radiant temperature inside the pavilion was significantly lower. ...
Article
Full-text available
Natural experiences in urban parks have a positive impact on the well-being and quality of life of people living in urban settings. Thus far, studies focused on urban parks have primarily surveyed general urban park spaces. There is a lack of research on specific rest environment settings, especially for leisure facilities such as pavilions. This study used virtual reality (VR) to create a simulation of people sitting in a pavilion, to evaluate the preferences and mental restoration of nine pavilions in Tokyo (N=61). The results showed that VR viewing effectively promoted mental restoration. The enclosure of the pavilion did not significantly affect people's preferences and perceived mental restoration in the environment setting. Moreover, the regression analysis revealed that the prospect and serene dimensions significantly influenced preferences; for restoration, the dimensions of “richness in species” and “serene” were significant predictors. Results indicate that providing visitors with spaces to sit, relax, socialize, read, and view the scenery could be beneficial. Urban park managers could consider adding people's preferred elements in these resting environments to create a generalized restorative environment setting. The results also suggest that VR can be used to simulate different resting environments for relaxation and restoration, as an alternative approach to experience nature.
... The proposed system was found more efficient than other insulated and uninsulated green roofs, where the indoor temperature was lower by 2℃. Meggers et al. [121] demonstrated an integrated energetic and architectural design of ''Thermoheliodome", a pavilion designed to fulfill cooling requirements using passive techniques or radiant (chilled pipes) and evaporative (cooling tower) cooling. ...
Article
There is an ever-increasing interest in radiant cooling systems (RCSs) due to their energy-saving potential and improved indoor thermal environment in modern buildings. In this part of the review, an overview of established practices and recent efforts in modeling, simulation, operation, control, and integration of RCSs is provided. Models and simulation tools are essential for reliable planning and design of RCSs due to the thermal inertia of activated slabs/panels. However, an increasing number of steady-state computational models of the indoor environment was highlighted, which does not match the highly dynamic nature of radiant systems, especially for thermally activated building systems (TABS). Integrated models of indoor environment and cooling systems, with high accuracy and moderate computational costs, are still lacking. Advanced control strategies, such as model predictive control, were found to reduce energy consumption by up to 44% while maintaining the space at favorable conditions. A major share of saved energy is due to intermittent operation of circulation pumps. Proposed strategies are often compared to conventional rule-based controllers. However, more studies are required to benchmark those predictive and adaptive controls. An emerging research direction on the integration of renewable energy resources was highlighted, yet coupling dynamics need to be further addressed in the literature, especially for solar power-driven systems. To boost this research direction, it is recommended to take advantage of previous studies on the integration of renewable energy systems with conventional cooling systems.
Article
Passive daytime radiative cooling (PDRC) is a low‐carbon energy technology to early achieve the “carbon neutrality” goal. Developing the commercial‐like colored PDRC coatings with sub‐ambient cooling performance is still a big challenge. Herein, a colored bilayer ZrO2‐PVDF PDRC coating with sub‐ambient cooling performance, self‐cleaning, and good weather resistance property is first reported. The colored bilayer coating is composed of a thick ultra‐white ZrO2‐PVDF reflective layer (Rsolar = 0.984) and a thin colorful layer. The obtained red bilayer ZrO2‐PVDF PDRC coating has a high solar reflectance (Rsolar = 0.950), which could realize the maximum temperature drop of 3.0 °C, and the calculated theoretical cooling power is as high as 131.66 W m−2, showing a good sub‐ambient cooling performance. Furthermore, they show a good self‐cleaning property. Meanwhile, the accelerated aging tests prove that they have a good weather resistance. This work provides a low‐cost, simple, and large‐scale method to prepare the commercial‐like colored PDRC coatings with the sub‐ambient cooling performance, showing a great practical application value. This work first reports a colored bilayer ZrO2‐PVDF passive daytime radiative cooling (PDRC) coating with sub‐ambient cooling performance, self‐cleaning, and good weather resistance property. The obtained red bilayer ZrO2‐PVDF PDRC coating has a high solar reflectance (Rsolar = 0.950), which could realize the maximum temperature drop of 3.0 °C, showing a great practical application value in daytime sub‐ambient radiative cooling.
Article
Pipe-embedded external wall using low-grade energy has been shown to significantly reduce the cooling or heating load of buildings. However, previous studies have generally focused on the heat transfer between water pipes and pipe-embedded wall and paid less attention on the energy use of water distribution. In this paper, a numerical model of serial pipe-embedded wall (SPW) considering water temperature changes in the pipeline is developed, and the load reduction and energy efficiency of the SPW are studied numerically under different climates and structures. The Influence of flow velocity and flow path on the performance of SPW is also investigated. The results show the following: (1) the SPW retains a satisfactory load reduction rate, which is only slightly less than that of the parallel pipe-embedded wall (PPW); (2) the coefficient of performance (COP) of the SPW is 10 times higher than that of the PPW after considering water distribution; (3) the water temperature affects the indoor load more than the sol-air temperature does, and the SPW has load reduction potential compared with the conventional wall when the water temperature is below 30 °C in summer or above 12 °C in winter; (4) increasing the flow path or flow velocity alone will not always result in better energy efficiency for a SPW system. There exists an optimum flow velocity or flow path that will maximize the energy efficiency of a SPW system.
Article
In this study, five layouts of using air-to-air heat exchangers (AAHE) were added in the Air Handling Unit (AHU) to diminish the cooling and heating coils energy usage through the energetic and exergetic analysis approach. In the first, second, and third techniques, the main focus is on cooling coil energy usage reduction. In the fourth and fifth layouts, new designs of using two AAHEs (i.e., primary and secondary units) have been incorporated to diminish simultaneously the energy demand of coils. The results showed if the objective function is defined to have the least cooling coil power, the fourth layout, and if the objective function is the lowest heating coil load, the fifth layout is recommended. In all layouts, installation of the AAHE reduced the irreversibility. In the best layout, AHU energy demand diminished by 23.68% which consequently improved the first law efficiency by 31.29%. Similarly, total exergy losses reduced by 26.58% and the second law efficiency improved by 11.79%. Calculations on cost analysis revealed that the least payback time and highest cost saving referred to first and fourth layouts, respectively.
Article
The mining industry is the largest electricity consumer in Chile. Sustainability reports of Chilean mining companies show that electricity consumption of mining camps is 350–500 kWh/m² per year. Despite cold climate conditions, mining camps show overheating, and 40% of the miners find them uncomfortable. Mining camps’ energy access is difficult because they are located in remote zones. This paper aims to optimize the building envelope and HVAC system to minimize the total energy consumption and eliminate the overheating risk of a real mining camp located at 4400 m.a.s.l. The mining camp is 30,000 m², built of timber prefabricated lightweight modules and hosts 1700 workers. The electricity consumption of the baseline case is 330 kWh/m²∙year and shows overheating. Multi-objective optimization is implemented to minimizing the electricity consumption while avoiding overheating. A hybrid multidimensional optimization algorithm (GenOpt), a building energy simulation program (EnergyPlus) and several scripts developed in Pyhthon for optimizing discrete variables and calculating the overheating risk of each thermal zone are coupled. Two different cases are optimized depending on the heating systems: electric heaters (Case I), which is the current situation; and heat pumps and chilled beams with free cooling option (Case II). This paper shows that an efficient HVAC system (Case II) is crucial for achieving thermal comfort and minimizing electricity consumption, which reaches 112.9 kWh/m²∙year, representing a significant reduction of 66% compared to the baseline case. The optimization process provides not only the optimum set of energy-efficient strategies but also a set of feasible solutions close to the optimum that allows flexibility to choose other strategies based on economic, transportation and on-site construction constraints.
Article
Public buildings such as libraries consume a vast amount of cooling energy for maintaining a comfortable and stable indoor environment in summer, especially in the hot-humid climate. This study used a case study approach to discuss the effect of low-energy strategies that can be applied to improve indoor thermal environment and cooling energy consumption of library buildings in hot and humid cities like Nanning City (a southern city, China). The use of cooling window shutters (a shutter with the effects of shading and evaporative cooling) and ceiling fans for generating airflow was considered as applicable energy-saving measures in this study, and a university library was selected as the study building in which the two energy-saving measures were employed. The SET* and annual cooling load before and after the adoption of the proposed measures were quantitatively investigated with a building energy consumption simulation software (DesignBuilder). Simulation results showed that the daytime SET* values can be reduced by 3.0 °C and 4.5 °C respectively on a typical summer day after the use of the cooling shutters and ceiling fans. Moreover, the cooling loads can also be decreased by 8.4% and 16.6% respectively. Particularly, the combination of these two measures enabled the daytime SET* value and annual cooling load lower by 7.0 °C and 60.8% respectively.
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Passive daytime radiative cooling (PDRC) can realize electricity‐free cooling by reflecting sunlight and emitting heat to the cold space. Current PDRC designs often involve costly vacuum processing or a large quantity of harmful organic solvents. Aqueous and paint‐like processing is cost‐effective and environmentally benign, thereby highly attractive for green manufacturing of PDRC coatings. However, common polymers explored in PDRC are difficult to disperse in water, let alone forming porous structures for efficient cooling. Here, a simple “bottom‐up” ball milling approach to create uniform microassembly of poly(vinylidene fluoride‐co‐hexafluoropropene) nanoparticles is reported. The micro‐ and nanopores among secondary particles and primary particles substantially enhance light scattering and results in excellent PDRC performance. A high solar reflectance of 0.94 and high emittance of 0.97 are achieved, making the coating 3.3 and 1.7 °C cooler than commercial white paints and the ambient temperature, under a high solar flux of ≈1100 W m⁻². More importantly, the volatile organic compound content in the aqueous paint is only 71 g L⁻¹. This satisfies the general regulatory requirements, which are critical to sustainability and practical applications.
Article
Purpose This study aims to simulate the flow and heat transfer through an air handling unit to reduce its energy consumption by a novel creative idea of using an air-to-air heat exchanger. Design/methodology/approach To do this, both first and second laws of thermodynamics energy and exergy balance equations were solved numerically by an appropriate developed computer code. Findings Using the air-to-air heat exchanger in dry conditions decreases the cooling coil load by 0.9 per cent, whereas the reduction for humid conditions is 27 per cent. Similarly, using air-to-air heat exchanger leads to an increase in the first law of efficiency in dry and humid conditions by 0.9 per cent and 36.8 per cent, respectively. Originality/value The second law of efficiency increases by 1.55 per cent and 2.77 per cent in dry and humid conditions, respectively. In other words, the effect of using an air-to-air heat exchanger in humid conditions is more than that in dry conditions.
Article
Air conditioning in buildings is energy intensive and takes up large proportion of global energy consumption. To pursue low energy expenditure, herein, we propose a radiant air-conditioning strategy with infrared transparent and low thermal conductive porous polyethylene aerogels. The aerogel allows direct heat exchange between the cooling panel and human body via radiation, and avoids cooling the entire space. Compared with traditional space air conditioning, a 6 mm-polyethylene aerogel assisted radiant air-conditioning saves the electricity by 31% under the same cooling and ambient temperature. Moreover, high solar reflectance and low thermal conductivity of the porous polyethylene holds great promise of the strategy in working outdoors. Our calculation demonstrates two thirds energy saving compared with direct space cooling in a typical summer day of Wuhan. These results show great potential of the cooling method in building cooling both in closed spaces and open conditions.
Article
Performing multi-objective optimization for actual public building design has become one of the most challenging subjects in buildings energy efficiency area. Gymnasium is a large energy consumer in public buildings. This study efforts to put forward a novel approach to tackle multi-objective optimization problems for building performance of Qingdao University (QUT) Gymnasium using a new metamodel method. For this purpose, the Nondominated Sorting Genetic Algorithm-II (NSGA-II) was dynamically combined with Multilayer Perception Artificial Neural Network (MLPANN) metamodel, which was previously trained with the co-simulation results conducted using EnergyPlus and Eppy. The new research method also proposes an optimal algorithm coupling Latin Hypercube Sample (LHS) with Principal Component Analysis (PCA) to minimize the total training samples, and guarantees the accuracy of optimization results. The most influential design factors like internal and external wall types, roof types, solar absorptance, windows shading as well as night ventilation (NV) strategy and displacement ventilation (DV) air conditioning system of the gymnasium were considered in three cases of 4×10⁸ possibilities to obtain the optimal trade-off results (Pareto front) between energy consumption and thermal comfort. Finally, a normalized minimum distance decision method was adopted to choose the optimal design configuration from the Pareto front. The optimization results of the study cases showed that reductions were achieved not only in the normalized objectives (88.0% less fh and 85.3% less fc) but also in the sub-objectives: up to 78.2% fewer heating energy and 71.3% fewer cooling energy in air conditioning seasons, and up to 97.7% less heating degree-hours and 99.2% less cooling degree-hours in naturally-ventilated seasons, compared to the original configuration by using optimal design takes simultaneous advantage of NV and DV strategies. The method was confirmed to be an efficient and robust tool for gymnasium design, it could reduce the calculation time of whole optimization process from 10 months to 2 days.
Conference Paper
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Maintaining the thermal comfort of building occupants is a challenge typically negotiated by air based heating and cooling systems that rigidly maintain supply air temperatures and humidity levels. Such a practice overlooks several other design variables, including the mean radiant temperature, TMRT , which is responsible for a significant portion of an occupant’s thermal comfort, or air velocity, v(air). The increased deployment of low exergy cooling strategies such as evaporative cooling and radiant cooling allows temperature potentials to be efficiently and effectively leveraged. However, the precise execution and subsequent control of these potentials in air based or radiant systems is driven by incomplete empirically based standards, removing heuristic guiding. Deciding where system setpoints should be for systems that go beyond simple air based cooling is difficult to arrive at through intuition and current metrics, as the inclusion and modulation of other thermal comfort variables such as air velocity, skin temperature, skin wettedness and metabolic rate are not entirely independent variables. The focus of this research is to approach thermal comfort with an occupant-centered stance, comparing heat loss through primary modes of heat transfer generated by an occupant’s metabolic rate. In doing so, the holistic integration of all comfort variables currently missing from the literature opens a window into an integrated design landscape including air temperature, T(MRT) , and relative humidity as the relevant independent variables for thermal comfort. Building on the array of low exergy building systems with integrated evaporative and radiative cooling systems in the literature, this new landscape will be presented as a tool for assessing a new radiant cooling system.
Conference Paper
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The understanding of thermal comfort has improved significantly since the introduction of the Fanger comfort model (1970), yet Predicted Mean Vote (PMV) and its adapted versions still are the predominantly used forms (Rupp et al., 2015). Out of the six variables contributing to the PMV values and occupant thermal comfort, Mean Radiant Temperature (MRT) and radiant exchanges account for up to half of an occupant's net heat loss. To better model the relationship between the human body and the radiant temperatures, a device to measure the MRT throughout an occupied space is required. This is a currently relevant piece of equipment as the number of radiant heating and cooling systems is increasing not only in the United States, but all around the world (Lin et al., 2016). We present the development and implementation of the SMART (Spherical Motion Average Radiant Temperature) Sensor as a means to improve available data and representation of comfort in building spaces.
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We present the design, construction and operation of a novel building systems laboratory, the BubbleZERO—Zero Emission Research Operation. Our objective was to design a space to evaluate the performance of Swiss-developed low exergy building systems in the tropical climate of Singapore using an integrated design approach. The method we employed for evaluation in the tropics was to design and build a test bed out of the shipping containers that transported the prototype low exergy systems from Switzerland to Singapore. This approach resulted in a novel laboratory environment containing radiant cooling panels and decentralized air supply, along with a self-shading, inflated “bubble” skin, experimental low emissivity (LowE) glazing, LED lighting, wireless sensors and distributed control. The laboratory evaluates and demonstrates for the first time in Singapore an integrated high-temperature cooling system with separate demand-controlled ventilation adapted for the tropics. It is a functional lab testing system in real tropical conditions. As such, the results showing the ability to mitigate the risk of condensation by maintaining a dew point below 18 °C by the separate decentralized ventilation are significant and necessary for potential future implementation in buildings. In addition, the control system provides new proof of concept for distributed wireless sensors and control for reliable automation of the systems. These key results are presented along with the integrated design process and real-life tropical operation of the laboratory.
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This study presents energy and exergy analyses and sustainability assessment of the novel evaporative air cooling system based on Maisotsenko cycle which allows the product fluid to be cooled in to a dew point temperature of the incoming air. In the energy analysis, Maisotsenko cycle’s wet-bulb and dew point effectiveness, COP and primary energy ratio rates are calculated. Exergy analysis of the system is then carried out for six reference temperatures ranging from 0°C to 23.88°C as the incoming air (surrounding) temperature. The specific flow exergy, exergy input, exergy output, exergy destruction, exergy loss, exergy efficiency, exergetic COP, primary exergy ratio and entropy generation rates are determined for various cases. Furthermore, sustainability assessment is obtained using sustainability index method. As a result, maximum exergy efficiency is found to be 19.14% for a reference temperature of 23.88°C where the optimum operation takes place.
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Human thermal physiological and comfort models will soon be able to simulate both transient and spatial inhomogeneities in the thermal environment. With this increasing detail comes the need for anatomically specific convective and radiative heat transfer coefficients for the human body. The present study used an articulated thermal manikin with 16 body segments (head, chest, back, upper arms, forearms, hands, pelvis, upper legs, lower legs, feet) to generate radiative heat transfer coefficients as well as natural- and forced-mode convective coefficients. The tests were conducted across a range of wind speeds from still air to 5.0 m/s, representing atmospheric conditions typical of both indoors and outdoors. Both standing and seated postures were investigated, as were eight different wind azimuth angles. The radiative heat transfer coefficient measured for the whole-body was 4.5 W/m2 per K for both the seated and standing cases, closely matching the generally accepted whole-body value of 4.7 W/m2 per K. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.4 and 3.3 W/m2 per K when standing and seated respectively. In the forced convective regime, heat transfer coefficients were higher for hands, feet and peripheral limbs compared to the central torso region. Wind direction had little effect on convective heat transfers from individual body segments. A general-purpose forced convection equation suitable for application to both seated and standing postures indoors was h c=10.3v 0.6 for the whole-body. Similar equations were generated for individual body segments in both seated and standing postures.
Article
There are few studies on the microclimate and human comfort of urban areas in hot dry climates. This study investigates the influence of urban geometry on outdoor thermal comfort by comparing an extremely deep and a shallow street canyon in Fez, Morocco. Continuous measurements during the hot summer and cool winter seasons show that, by day, the deep canyon was considerably cooler than the shallow one. In summer, the maximum difference was on average 6K and as great as 10K during the hottest days. Assessment of thermal comfort using the PET index suggests that, in summer, the deep canyon is fairly comfortable whereas the shallow is extremely uncomfortable. However, during winter, the shallow canyon is the more comfortable as solar access is possible. The results indicate that, in hot dry climates a compact urban design with very deep canyons is preferable. However, if there is a cold season as in Fez, the urban design should include some wider streets or open spaces or both to provide solar access.
Article
An equation is presented for wet-bulb temperature as a function of air temperature and relative humidity at standard sea level pressure. It was found as an empirical fit using gene-expression programming. This equation is valid for relative humidities between 5% and 99% and for air temperatures between -20 degrees and 50 degrees C, except for situations having both low humidity and cold temperature. Over the valid range, errors in wet-bulb temperature range from -1 degrees to +0.65 degrees C, with mean absolute error of less than 0.3 degrees C.
Article
In this paper the energy and exergy performance of a social dwelling of a multi-family building from the 1960s in Bilbao (Spain) is presented and various improved energy concepts based on exergy principles are proposed and investigated. The aim of this paper is to explore and demonstrate the usefulness of the exergy approach in the assessment and development of an energy system for the dwelling under consideration. The total energy supply system is analysed, including the demand (space heating, domestic hot water and electricity), the system components (for conversion, storage and distribution) and the energy input from energy resources (primary energy and renewable resources). The study includes a comparison of the primary energy input of all cases considered and an analysis of the energy and exergy losses of each system component. The study has shown that the exergy analysis reveals thermodynamic losses that are not revealed using energy analysis and secondly, that the development of an improved energy system based on exergy principles has resulted in a significantly reduced primary energy input compared to the reference situation.
Article
Low exergy (LowEx) building systems create more flexibility and generate new possibilities for the design of high performance buildings. Instead of maximizing the barrier between buildings and the environment using thick insulation, low exergy systems maximize the connection to the freely available dispersed energy in the environment. We present implementations of LowEx technologies in prototypes, pilots and simulations, including experimental evaluation of our new hybrid PV-thermal (PV/T) panel, operation of integrated systems in an ongoing pilot building project, and cost and performance models along with dynamic simulation of our systems based on our current office renovation project. The exploitation of what we call ”anergy sources” reduces exergy use, and thus primary energy demand. LowEx systems provide many heating and cooling methods for buildings using moderate supply temperatures and heat pumps that exploit more valuable anergy sources. Our implementation of integrated LowEx systems maintains low temperature-lifts, which can drastically increase heat pump performance from the typical COP range of 3–6 to values ranging from 6 to 13.
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The thermal conditions encountered in outdoor urban spaces are a major determinant of the patterns of usage of the spaces. For better urban planning and design, the issue of outdoor comfort should be highlighted. This paper summarizes an extensive literature review on outdoor comfort studies. It seeks to understand the effects of airflow on pedestrian comfort in three categories: wind force, wind chill, and thermal comfort. The paper then develops guidelines for urban Hong Kong based on the findings. A comfort outdoor temperature chart for Hong Kong was developed based on the results. Urban wind speeds ranging from 1.0 to 2.0 m/s are recommended for pedestrian comfort in shade on typical clear sunny days in summer Hong Kong.
Article
The mean radiant temperature (Tmrt) is one of the most important meteorological parameters governing human energy balance. In this paper, three different methods of obtaining the Tmrt in an outdoor urban setting are compared. Method A is based on integral radiation measurements and angular factors, method B is based on measurements with a 38-mm flat grey globe thermometer and in method C makes use of the Rayman 1.2 software is used. Measurements were performed in a large open square in a high latitude city—Göteborg, Sweden—during clear to overcast weather conditions in October 2005 and in July and August 2006. Results show that the difference between Method A and Method B was generally relatively small. Most of the discrepancy, caused by rapid changes in radiation, temperature and wind speed was smoothed out using 5 min mean values. By systematically and empirically changing the mean convection coefficient, the accuracy of Method B was improved and a new equation expressing the Tmrt was obtained. With this new equation the 38 mm flat grey globe thermometer could successfully be used to estimate the Tmrt in an outdoor urban setting provided that the wind speed and the air and globe temperatures are measured accurately. The study also shows that the flat grey colour of the globe thermometer slightly underestimates the level of short-wave radiation (i.e. sunshine). Method C works very well during the middle of the day in July, i.e. at high sun elevations. However, the model considerably underestimates the Tmrt in the morning and evening in July and during the whole day in October, i.e. at low sun elevations. In outdoor urban settings where thermal comfort researchers or urban planners and designers require an easy and reliable method of estimating mean radiant temperature, the 38 mm flat grey globe thermometer provides a good and cheap solution. Copyright
Article
The variables which are said to affect human temperature sensitivity are the skin temperature, the area of thermal stimulation and the rate at which the temperature of the skin is changed. Of these, the last has been only partially described. Measurements of the warm and cool thresholds were made on two males, experienced in making threshold judgments, when the rate of stimulus temperature change was varied between 0.01–0.3° C/sec. Both the warm and cool thresholds remained constant at rates of 0.1° C/sec and above but increased rapidly when slower rates were used. The effect of slow rates of stimulus temperature change was greater on the warm threshold than upon the cool threshold. It is concluded that the rate of temperature change does not represent information about the rate constants of stimulation of warm and cool receptors but that its effect is by way of the rate at which thermal adaptation occurs
Article
There is an obvious and indisputable need for an increase in the efficiency of energy utilisation in buildings and in the energy supply system within communities. Heating, cooling and lighting appliances in buildings account for more than one third of the world's primary energy demand. In turn, building stock is a major contributor to energy-related environmental problems and CO2 emissions. There are great potentials to be obtained through a more efficient supply of energy and rational use of energy in buildings.An optimisation of the exergy flows in buildings and related supply structures, similar to other thermodynamic systems such as power stations, can help in identifying the potential of increasing efficiency in energy utilisation. Through analyses, it can be shown that calculations based on the energy conservation and primary energy concept alone are inadequate for gaining a full understanding of all important aspects of energy utilisation processes. The high potential for a further increase in the efficiency of; for example, boilers, cannot be quantified exclusively by performing energy analyses—the energy efficiency is close to 100%; however, this potential can be demonstrated by using an exergy analysis, whereby the exergy efficiency of a common gas boiler is about 8%. It is necessary to work out new and more efficient ways to supply energy to satisfy the demand for energy services.This paper outlines the international co-operative work in the general framework of the International Energy Agency (IEA), the ECBCS Annex 49 “Low Exergy Systems for High Performance Buildings and Communities” [Annex 49, Energy Conservation in Buildings and Community Systems—Low Exergy Systems for High Performance Buildings and Communities, homepage: http://www.annex49.com, 2007].
Article
The research being undertaken seeks to achieve a better understanding of the richness of microclimatic characteristics in outdoor urban spaces, and the comfort implications for the people using them. The underlying hypothesis is that these conditions influence people’s behaviour and usage of outdoor spaces. The initial results demonstrate that a purely physiological approach is inadequate in characterising comfort conditions outdoors, and an understanding of the dynamic human parameter is necessary in designing spaces for public use. The thermal environment is indeed of prime importance influencing people’s use of these spaces, but psychological adaptation (available choice, environmental stimulation, thermal history, memory effect, expectations) is also of great importance in such spaces that present few constraints.
Article
In this article, we assess the potential development of energy use for future residential heating and air conditioning in the context of climate change. In a reference scenario, global energy demand for heating is projected to increase until 2030 and then stabilize. In contrast, energy demand for air conditioning is projected to increase rapidly over the whole 2000–2100 period, mostly driven by income growth. The associated CO2 emissions for both heating and cooling increase from 0.8 Gt C in 2000 to 2.2 Gt C in 2100, i.e. about 12% of total CO2 emissions from energy use (the strongest increase occurs in Asia). The net effect of climate change on global energy use and emissions is relatively small as decreases in heating are compensated for by increases in cooling. However, impacts on heating and cooling individually are considerable in this scenario, with heating energy demand decreased by 34% worldwide by 2100 as a result of climate change, and air-conditioning energy demand increased by 72%. At the regional scale considerable impacts can be seen, particularly in South Asia, where energy demand for residential air conditioning could increase by around 50% due to climate change, compared with the situation without climate change.
Article
This paper discusses the contribution of street design, i.e. aspect ratio (or height-to-width ratio, H/W) and solar orientation, towards the development of a comfortable microclimate at street level for pedestrians. The investigation is carried out by using the three-dimensional numerical model ENVI-met, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for a typical summer day in Ghardaia, Algeria (32.40°N, 3.80°E, 469 m a.s.l.), a region characterized by a hot and dry climate. Symmetrical urban canyons, with various height-to-width ratios (i.e. H/W=0.5, 1, 2 and 4) and different solar orientations (i.e. E–W, N–S, NE–SW and NW–SE), have been studied. Special emphasis is placed on a human bio-meteorological assessment of these microclimates by using the physiologically equivalent temperature (PET).The results show contrasting patterns of thermal comfort between shallow and deep urban streets as well as between the various orientations studied. A comparison of all case studies reveals that the time and period of day during which extreme heat stress occurs, as well as the spatial distribution of PETs at street level, depend strongly on aspect ratio and street orientation. This is crucial since it will directly influence the design choices in relation to street usage, e.g. streets planned exclusively for pedestrian use or including motor traffic, and also the time of frequentation of urban spaces. Both investigated urban factors can mitigate extreme heat stress if appropriately combined. The solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs for solar energy.
Article
The temperature difference between a clothed man and his surrounding objects can be easily detected and recognised by using a thermal camera. To thermally camouflage a clothed man, the apparent surface temperature pattern of the clothing fabric under a thermal camera should satisfy two criteria: these are temperature and spatial similarity to the surrounding natural objects. Temperature similarity can be achieved by either reducing the actual fabric surface temperature and/or reducing the fabric surface thermal emittance. In this study, theoretical analysis has been used to predict the fabric surface apparent temperature in a simulated man/clothing/environment system. An air gap of approximately 9 mm between the fabric and the hotplate surface was found to be the optimum for controlling the fabric surface temperature. The apparent temperature of the fabric matched its surroundings by adjusting its surface emissivity depending on the ambient temperature. Disruptive Pattern Combat Uniform (DPCU) fabric was used in the experimental assessment of the theoretical predictions which were in good agreement with the theoretical predictions. A sweating hotplate was used in the dry and wet states to assess the influence of evaporative heat on the fabric surface temperature. No significant difference was found between the dry and wet states of the sweating hotplate. This study recommends that a spaced structure fabric with an air gap thickness around 9 mm be developed for reducing the clothing fabric surface temperature. It is also recommended that the apparent temperature of natural foliage and other field objects, in hot harsh environment, be investigated in order to determine the appropriate fabric surface emissivity. Theoretical analysis is presented to predict the fabric surface temperature in a simulated man / clothing fabric / environment system. The predicted outcomes have been validated by comparison with the experimental results using a sweating hotplate in an environmental chamber. An air gap of approximately 9mm between the fabric and the hotplate surface was found to be the optimum for controlling the fabric surface temperature. The apparent temperature of the fabric can match its surrounding objects by further adjusting its surface emissivity depending on the ambient temperature. A Disruptive Pattern Combat Uniform (DPCU) fabric was used in the experimental assessment of the theoretical predictions which were in good agreement with the theoretical predictions. A sweating hotplate with dry and wet states was also used to assess the influence of evaporative heat on the fabric surface temperature. No significant difference was found in the fabric surface apparent temperature between the dry and wet states. DGDL-A
Human-Body Exergy Balance and Thermal Comfort
  • M Shukuya
  • M Saito
  • K Isawa
  • T Iwamatsu
  • H Asada
M. Shukuya, M. Saito, K. Isawa, T. Iwamatsu, H. Asada, Human-Body Exergy Balance and Thermal Comfort, Tech. rep., IEA ECBCS Annex 49 -Low Exergy Systems for High-Performance Buildings and Communities (2010).
Energy efficiency in commercial buildings with concrete core activiation
  • F Mauersberger
  • D Cibis
F. Mauersberger, D. Cibis, Energy efficiency in commercial buildings with concrete core activiation, in: International High Performance Buildings Conference, 2012, pp. 1-6. URL http://docs.lib.purdue.edu/ihpbc/64
The robotic touch: how robots change architecture
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F. Gramazio, M. Kohler, J. Willmann, The robotic touch: how robots change architecture, Park Books, Zurich, 2014.
Thermoheliodome design, optimization and fabrication
  • Y Rhode-Barbarigosc
  • S Anastasc
  • J Coffers
  • Pantelic
Rhode-Barbarigosc, Y. Anastasc, S. Coffers, J. Pantelic, Thermoheliodome design, optimization and fabrication, in: 6th International Building Physics Conference, IBPC 2015, Elsevier, Torino, Italy, 2015.
Different methods for estimating the mean radiant temperature in an outdoor urban setting
  • S Thorsson
  • F Lindberg
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S. Thorsson, F. Lindberg, I. Eliasson, B. Holmer, Different methods for estimating the mean radiant temperature in an outdoor urban setting, International Journal of Climatology 27 (14) (2007) 1983-1993. doi:10.1002/joc.1537. URL http://onlinelibrary.wiley.com/doi/10.1002/joc.1537/abstract
Evaporative Cooling in Constructed ENvelopes by Transmission and Retention Inside Casings of Buildings
  • E Teitelbaum
  • F Meggers
  • G Scherer
  • P Ramamurthy
  • L Wang
  • E Bou-Zeid
  • Buildings
E. Teitelbaum, F. Meggers, G. Scherer, P. Ramamurthy, L. Wang, E. Bou-Zeid, ECCENTRIC Buildings: Evaporative Cooling in Constructed ENvelopes by Transmission and Retention Inside Casings of Buildings, in: 6th International Building Physics Conference, IBPC 2015, Elsevier, Torino, Italy, 2015.