Abstract
Passively enhancing the convective cooling of solar photovoltaics (PV) panels by the prevailing atmospheric wind is possibly the simplest and yet an effective means to boost solar energy production. Among the numerous ways to promote turbulent convective cooling, the conventional tripwire concept is straightforward to implement. The square wire with sharp edges placed at varying angles of attack is explored for its effectiveness in augmenting the convective cooling of a surrogate PV panel. Specifically, the heat transfer performance over an approximately constant temperature flat plate downstream of a 4 mm2 wire, placed at 6 mm from the flat surface, with 15° to 75° attack angle is scrutinized in a wind tunnel at 5 m/s wind velocity. The resulting local Nusselt number enhancement is explained in terms of the perturbed turbulent flow characteristics, detailed using a triple-wire constant-temperature hot wire. A higher level of turbulence along with more energetic and larger energy-containing eddying motions are captured behind the 60° attack angle wire, contributing to the most efficacious cooling of the surrogate PV panel. These results translate into 2–3% increase in the PV panel energy output.
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Abbreviations
- \( A \) :
-
Area of the PTFE plate
- \( D \) :
-
Width of the square wire
- E :
-
Uncertainty
- F :
-
Frequency
- \( G_{T} \) :
-
Solar irradiance
- \( h \) :
-
Heat transfer coefficient
- \( K_{air} \) :
-
Thermal conductivity of air
- \( K_{PTFE} \) :
-
Thermal conductivity of PTFE plate
- \( Re \) :
-
Reynolds number
- \( Nu \) :
-
Nusselt number
- \( Nu_{0} \) :
-
Nusselt number without the square wire
- \( P \) :
-
Electric power output
- \( P_{0} \) :
-
Electric power output without the square wire
- \( PTFE \) :
-
Polytetrafluoroethylene
- PV :
-
Solar photovoltaics
- \( Q_{convection} \) :
-
Convective heat transfer
- \( Q_{radiation} \) :
-
Radiation heat transfer
- \( Q_{total} \) :
-
Total heat transfer
- St :
-
Strouhal Number
- \( T_{air} \) :
-
Temperature of the ambient air
- \( T_{c} \) :
-
Cell temperature of PV panel
- \( T_{bottom} \) :
-
Temperature of the bottom surface of the PTFE plate
- \( T_{ref} \) :
-
Reference temperature
- \( T_{top} \) :
-
Temperature of the top surface of the PTFE plate
- \( T_{top,0} \) :
-
Temperature of the top surface of the PTFE plate without the wire
- \( T_{wall} \) :
-
Wall temperature of the wind tunnel
- \( t_{PTFE} \) :
-
Thickness of the PTFE plate
- \( Tu,Tv,Tw \) :
-
Turbulence intensity in X, Y, and Z direction, respectively
- \( U,V,W \) :
-
Instantaneous velocity in X, Y, and Z direction, respectively
- \( \bar{U},\bar{V},\bar{W} \) :
-
Time-averaged velocity in X, Y, and Z direction, respectively
- \( U_{\infty } \) :
-
Free stream velocity in X direction
- \( u,v,w \) :
-
Instantaneous fluctuating velocity in X, Y, and Z direction, respectively
- \( u_{rms} ,v_{rms} ,w_{rms} \) :
-
Root mean square velocity in X, Y, and Z direction, respectively
- \( X \) :
-
Streamwise direction
- \( Y \) :
-
Widthwise direction
- \( Z \) :
-
Vertical direction
- \( \beta \) :
-
Temperature coefficient
- \( \varepsilon \) :
-
Emissivity
- \( \eta \) :
-
Electric efficiency
- \( \eta_{ref} \) :
-
Efficiency at reference temperature
- \( \Theta \) :
-
Square wire attack angle
- \( \varLambda \) :
-
Integral length scale
- \( \lambda \) :
-
Taylor microscale
- \( \nu \) :
-
Kinematic viscosity
- \( \tau \) :
-
Temporal distance
- \( \tau_{\varLambda } \) :
-
Integral time scale
- \( \tau_{\lambda } \) :
-
Taylor time scale
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This work was made possible by Natural Sciences and Engineering Research Council of Canada and Ontario Centres of Excellence.
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Yang, Y., Ahmed, A., Ting, D.SK., Ray, S. (2019). The Influence of Square Wire Attack Angle on the Heat Convection from a Surrogate PV Panel. In: Vasel, A., Ting, DK. (eds) The Energy Mix for Sustaining Our Future. EAS 2018 2018. Springer Proceedings in Energy. Springer, Cham. https://doi.org/10.1007/978-3-030-00105-6_7
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