Experimental and theoretical investigation of a nocturnal radiator for space cooling

Bagiorgas, H.S.; Mihalakakou, G.

doi:10.1016/j.renene.2007.04.015

Cited by 81 publications

(32 citation statements)

References 16 publications

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“…The cooling energy consumption and the effect of energy-free radiation application were simulated in five typical cities across China. Bagiorgas and Mihalakakou [7] established an aluminum nocturnal radiator painted with appropriate white paint. The dynamic thermal performance of the system during summer was calculated using an accurate mathematical model through an extensive validation process.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

Pei

et al. 2015

International Journal of Photoenergy

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A spectral selectivity surface for both solar heating and radiative cooling was proposed. It has a high spectral absorptivity (emissivity) in the solar radiation band and atmospheric window band (i.e., 0.2∼3 m and 8∼13 m), as well as a low absorptivity (emissivity) in other bands aside from the solar radiation and atmospheric window wavelengths (i.e., 3∼8 m or above 13 m). A type of composite surface sample was trial-manufactured combining titanium-based solar selective absorbing coating with polyethylene terephthalate (TPET). Sample tests showed that the TPET composite surface has clear spectral selectivity in the spectra of solar heating and radiation cooling wavelengths. The equilibrium temperatures of the TPET surface under different sky conditions or different inclination angles of surface were tested at both day and night. Numerical analysis and comparisons among the TPET composite surface and three other typical surfaces were also performed. These comparisons indicated that the TPET composite surface had a relative heat efficiency of 76.8% of that of the conventional solar heating surface and a relative temperature difference of 75.0% of that of the conventional radiative cooling surface, with little difference in cooling power.

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Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

Pei

et al. 2015

International Journal of Photoenergy

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“…This is why it is very important that the radiant surface has high emissivity in this spectrum. The work of Bagiorgas et al [8] outlines the effect of coatings of different emissivity. Generally, non-metallic, light coloured surfaces are recommended.…”

Section: Free Cooling Based On Nocturnal Radiationmentioning

confidence: 99%

“…Mihalakakou et al [7] investigated the dynamic performance of a lightweight metallic radiator that cools air underneath its surface whereas its sky-facing side is covered by a single polyethylene wind shield. Bagiorgas et al [8] set up an experimental model of a nocturnal radiator and compared the results of measurements with a mathematical model. Two separate cases were examined, when the radiator surface was painted with two kinds of white paint, each with different emissivity.…”

Section: Introductionmentioning

confidence: 99%

Nocturnal Radiation: New Opportunity in Building Cooling

2017

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Free cooling systems are gaining increased attention as air conditioners are responsible for a remarkable amount of the electric peak load in summer. Several studies have shown that night ventilation of buildings reduces peak loads of the following day. However, their effect can be increased by a free cooling system based on nocturnal long wave radiation, which cools the air below ambient temperature. A perforated, corrugated metal plate which is used in transpired solar air heaters, functions as a radiating shield in this case. The air can reach temperatures below ambient as it passes the plate further increasing the free cooling's potential. A mathematical model has been set up to describe the cooling process. Based on governing equations diagrams are developed to show the correlation between the transpired radiant plate's temperature drop, as well as its cooling rate as a function of the long wave radiant heat flux and the air flow rate. Four European capitals are chosen to illustrate the cooling potential of nocturnal radiative air cooling. Building simulation is carried out using RETScreen 4 Clean Energy Project Analysis software. Results show that locations with drier climate reach higher nocturnal cooling performance as the moisture content of the atmosphere influences the radiant heat transfer.

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“…Cloudiness has an effect on the incident radiation which can be expressed by the factor C as shown in Equation (3.27) [18,19] and the effective emissivity of the sky is given by…”

Section: (325)mentioning

confidence: 99%

“…Drawing air underneath the solar panels has the benefit of reducing the panel temperature as described by [19] and a reduction in the temperature of the solar panels increases their electrical conversion efficiency. This benefit can be quantified using the temperature coefficient of the solar panels, β.…”

Section: Pv Electrical Efficiencymentioning

confidence: 99%

Development and optimization of an innovative HVAC system with integrated PVT and PCM thermal storage for a net-zero energy retrofitted house

Fiorentini

Cooper

2015

Energy and Buildings

141

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. (2015). Development and optimization of an innovative HVAC system with integrated PVT and PCM thermal storage for a net-zero energy retrofitted house. Energy and Buildings, Development and optimization of an innovative HVAC system with integrated PVT and PCM thermal storage for a net-zero energy retrofitted house AbstractThis paper describes a novel solar-assisted HVAC system developed for the Team UOW 'Illawarra Flame' Solar Decathlon house, the winner of the Solar Decathlon China 2013 competition. This HVAC system consists of an air-based photovoltaic-thermal (PVT) collector and a phase change material (PCM) thermal storage unit integrated with a reverse cycle heat pump, in a ducted system. The system was designed for operation during both winter and summer using daytime solar radiation and night-time sky radiative cooling, respectively. The PVT collector heats or cools fresh air from ambient and thereby provides heating or cooling either directly to the indoor space, or to the PCM storage unit. The heat stored in the PCM can be used later to condition the space or precondition the air entering the air handling unit. Analytical models for the PVT collector and PCM unit were developed in order to be easily implemented into a practical building management system (BMS). Experimental studies on the PVT collector and PCM unit were carried out and the data was used to validate the effectiveness of the models. It is shown that there is a good agreement between the model simulation results and experimental test data. A simple optimisation methodology of the operating modes that involve these components is also presented. collector and a Phase Change Material (PCM) thermal storage unit integrated with a reverse cycle heat pump, in a ducted system. The system was designed for operation during both winter and summer using daytime solar radiation and night-time sky radiative cooling, respectively. The PVT collector heats or cools fresh air from ambient and thereby provides heating or cooling either directly to the indoor space, or to the PCM storage unit. The heat stored in the PCM can be used later to condition the space or precondition the air entering the Air Handling Unit. Analytical models for the PVT collector and PCM unit were developed in order to be easily implemented into a practical Building Management System (BMS).Experimental studies on the PVT collector and PCM unit were carried out and the data was used to validate the effectiveness of the models. It is shown that there is a good agreement between the model simulation results and experimental test data. A simple optimisation methodology of the operating modes that involve these components is also presented.

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Experimental and theoretical investigation of a nocturnal radiator for space cooling

Cited by 81 publications

References 16 publications

Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

Theoretical and Experimental Study of Spectral Selectivity Surface for Both Solar Heating and Radiative Cooling

Nocturnal Radiation: New Opportunity in Building Cooling

Development and optimization of an innovative HVAC system with integrated PVT and PCM thermal storage for a net-zero energy retrofitted house

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