A model and heat transfer correlation for rooftop integrated photovoltaics with a passive air cooling channel

Mittelman, Gur; Alshare, Aiman; Davidson, Jane H.

doi:10.1016/j.solener.2009.01.015

Cited by 72 publications

(25 citation statements)

References 17 publications

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“…A comparison among the models is necessary as to conclude on the conditions T pv is predicted effectively and consistently. It is, therefore, necessary to compare T pv models extensively to examine their validity in any PV configuration as the ones studied in [20,[26][27][28][29].A time dependent temperature profile is developed in a PV cell when under solar irradiance, I T , [8,30]. The latter is the main factor contributing to the development of the temperature profile in which the ambient temperature T a and the wind speed play a role too.…”

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A New Dynamic Model to Predict Transient and Steady State PV Temperatures Taking into Account the Environmental Conditions

Kaplanis

Kaplani

2018

Energies

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Photovoltaic (PV) cell and module temperature profiles, T c and T pv , respectively, developed under solar irradiance were predicted and measured both at transient and steady state conditions. The predicted and measured T c or T pv covered both a bare c-Si PV cell, by SOLARTEC, at laboratory conditions using a solar light simulator, as well as various c-Si and pc-Si modules (SM55, Bioenergy 195W, Energy Solutions 125W) operating in field conditions. The time constants, τ, of the T c and T pv profiles were determined by the proposed model and calculated using the experimentally obtained profiles for both the bare PV cell and PV modules. For model validation, the predicted steady state and transient temperature profiles were compared with experimental ones and also with those generated from other models. The effect of the ambient temperature, T a , wind speed, v w , and the solar irradiance, I T , on the model performance, as well as of the mounting geometries, was investigated and incorporated in the prediction model. The predicted temperatures had the best matching to the measured ones in comparison to those from six other models. The model developed is applicable to any geographical site and environmental conditions. Energies 2019, 12, 2 2 of 17 b.Theoretical based semi-empirical models, a mixture of Physics based processes elaborated on implicit functions, which through regression analysis incorporate the environmental conditions and develop expressions to predict T pv including geometrical factors like PV module inclination, sun-tracking systems, BIPV [6,8,21]. c.Approaches based on Artificial Neural Networks (ANN) [5,10,22].An assessment of the T pv prediction models discloses that those which have incorporated the radiation exchanges and the air flow regimes, where heat extraction off the modules is affected specifically, provide values closer to the measured ones [6,7,[23][24][25]. A comparison among the models is necessary as to conclude on the conditions T pv is predicted effectively and consistently. It is, therefore, necessary to compare T pv models extensively to examine their validity in any PV configuration as the ones studied in [20,[26][27][28][29].A time dependent temperature profile is developed in a PV cell when under solar irradiance, I T , [8,30]. The latter is the main factor contributing to the development of the temperature profile in which the ambient temperature T a and the wind speed play a role too. This profile has a straight relationship with I T at low Concentration Ratio, C, conditions, with C < 4, where C = I T /10 3 W/m 2 , and a strong dependence on the wind speed, v w ; that is, T c (t; I T , v w ). T c (t) depends, also, on the cell structure and the material composition of its layers. Figure 1 shows a section of a PV cell with its characteristic layers which govern the heat conduction causing an effect on the time constant, τ, of the temperature profiles. T c (t) or T pv (t), either the PV module is heated or cooled due to changes in the environmental conditions, is described ...

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A New Dynamic Model to Predict Transient and Steady State PV Temperatures Taking into Account the Environmental Conditions

Kaplanis

Kaplani

2018

Energies

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“…Their experimental results were well matching the theoretical predictions for constrained flow, but were less accurate for ducts with opened ends. For the latter, Mittelman et al developed a generalized correlation for the average channel Nusselt number for the combined convective-radiative cooling [50]. Their solution of the governing equations and boundary conditions was computed through CFD analysis.…”

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confidence: 99%

Hybrid Solar: A Review on Photovoltaic and Thermal Power Integration

Chow

Tiwari

Ménézo

2012

International Journal of Photoenergy

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The market of solar thermal and photovoltaic electricity generation is growing rapidly. New ideas on hybrid solar technology evolve for a wide range of applications, such as in buildings, processing plants, and agriculture. In the building sector in particular, the limited building space for the accommodation of solar devices has driven a demand on the use of hybrid solar technology for the multigeneration of active power and/or passive solar devices. The importance is escalating with the worldwide trend on the development of low-carbon/zero-energy buildings. Hybrid photovoltaic/thermal (PVT) collector systems had been studied theoretically, numerically, and experimentally in depth in the past decades. Together with alternative means, a range of innovative products and systems has been put forward. The final success of the integrative technologies relies on the coexistence of robust product design/construction and reliable system operation/maintenance in the long run to satisfy the user needs. This paper gives a broad review on the published academic works, with an emphasis placed on the research and development activities in the last decade.

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“…Passive cooling methods have an advantage that no additional power is required. A scale analysis and numerical study on PV modules that involved an open-air channel were conducted by Mittelman et al [12]. In addition, Ebrahimi [13] developed a new cooling technology that used natural vapor as a coolant to extract heat from PV modules.…”

Section: Introductionmentioning

confidence: 99%

Study on the Cooling Effect of Attached Fins on PV Using CFD Simulation

Kim

Nam

2019

Energies

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The issue of efficiency decrease according to temperature increase is a pending problem in the PV market. Several active and passive technologies have been suggested but few quantitative studies on the estimation of the cooling effect have been carried out. In this study, a CFD (computational fluid dynamics) simulation model was developed to analyze a passive cooling technology using fins attached to the back of the PV module. Furthermore, a method to improve airflow at the back of the PV module by forming slits in the frame was analyzed. The simulation model reproduced the indoor test that uses a solar simulator and the cooling performance was analyzed according to the shape of the fins and the presence of slits. In the simulation results, the surface temperature and expected electrical efficiency without cooling were 62.78 °C and 13.24% respectively under nominal operating cell temperature conditions. Moreover, the temperature reduced by approximately 15.13 °C because the fins attached at the bottom of the PV module increased the heat transfer area with airflow. Thus, the electrical efficiency according to the PV module temperature was predicted as 14.39%. Furthermore, when slits were installed between the fins, they increased the airflow velocity and accelerated the formation of turbulence, thereby improving the cooling performance of the fins. The simulation results showed that the temperature could be further reduced by approximately 8.62 °C at a lower air velocity. As the fins and slits can also reduce the non-uniformity of the temperature, they are expected to supplement the efficiency and durability reduction of the PV modules caused by the hot spot phenomenon. In addition, it was shown that slits in the frame could further improve the cooling performance of the fins at a low-velocity airflow.

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A model and heat transfer correlation for rooftop integrated photovoltaics with a passive air cooling channel

Cited by 72 publications

References 17 publications

A New Dynamic Model to Predict Transient and Steady State PV Temperatures Taking into Account the Environmental Conditions

A New Dynamic Model to Predict Transient and Steady State PV Temperatures Taking into Account the Environmental Conditions

Hybrid Solar: A Review on Photovoltaic and Thermal Power Integration

Study on the Cooling Effect of Attached Fins on PV Using CFD Simulation

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