Performance analysis of photovoltaic–thermal (PVT) mixed mode greenhouse solar dryer

Published Date
Solar Energy
August 2016, Vol.133:421–428, doi:10.1016/j.solener.2016.04.033

Author 

• Sumit Tiwari ^a,,
• G.N. Tiwari ^a
• I.M. Al-Helal ^b

• aCentre for Energy Studies, Indian Institute of Technology Delhi, Hauzkhas, New Delhi 110016, India
• bDepartment of Agricultural Engineering, College of Food & Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia

Received 6 November 2015. Revised 3 March 2016. Accepted 20 April 2016. Available online 29 April 2016. 

Highlights

• •
  Present system is designed for rural area in developing country where grid connectivity is not available everywhere.
• •
  Thermal modeling has been done with experimental validation.
• •
  Characteristic curve have been made for system and drying.
• •
  Overall thermal energy and overall exergy have been calculated with experimental validation.

Abstract

A hybrid photovoltaic–thermal (PVT) greenhouse solar dryer under mixed mode has been proposed and different parameters have been evaluated for climatic condition of Indian Institute of Technology, New Delhi (28_350N, 77_120E, 216 m above MSL), India. Further thermal modelling has been developed for the PVT greenhouse dryer by considering different parameter namely crop, greenhouse and solar cell temperatures, etc. Numerical computations have been done with the help of program made on MATLAB 2013a and the results are validated with experimental values. Characteristic curves have been developed for drying and system efficiency with experimental validation. Further, an overall thermal energy and exergy have been calculated. Theoretical and experimental values of overall thermal energy found to be 1.92 kW h and 2.03 kW h respectively. It can be seen that there is good agreement between theoretical and experimental value with r = 0.98 and e = 10.76. Further validation has also been done for energy and exergy of PVT dryer.

Keywords

Heat transfer coefficient

Overall thermal energy

Overall exergy

PVT greenhouse mixed mode dryer

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Nomenclature

A_c

area of crop surface (m²)

A_m

area of module (m²)

A_i

area of all side wall of dryer (m²)

C_f

specific heat of air (J/kg K)

C_cr

specific heat of crop (J/kg K)

C

air conductance (W/m² K)

D

diameter of fan (m)

h_i

heat transfer coefficient (htc) inside solar drying chamber (W/m² K)

h_cr

total htc from crop surface to solar drying chamber (W/m² K)

h_crc

convective htc from crop surface to solar drying chamber (W/m² K)

h_crew or h_ew

evaporative htc from crop surface to solar drying chamber (W/m² K)

h_o

heat transfer coefficient from top of module to ambient (W/m² K)

h₁

heat transfer coefficient from wall of dryer to ambient (W/m² K)

I_t

solar intensity (W/m²)

I(i)

solar intensity on the wall of drying chamber (W/m²)

I_eff

total radiation on the crop (W/m²)

k_g

thermal conductivity of glass of module (W/m K)

K_g

thermal conductivity of glazing (W/m K)

l_g

thickness of glass cover of module (m)

L_g

thickness of glazing (m)

mass flow rate of air (kg/s)

M_cr

mass of crop (kg)

N

fan speed (RPM)

P_fan

power of fan (W)

P_Tr

partial pressure at green house chamber temperature (N/m²)

P_Tcr

partial pressure at crop temperature (N/m²)

T_a

ambient temperature (°C)

T_o

cell temperature for optimum cell efficiency i.e. 25 °C

T_c

cell temperature (°C)

T_cr

crop temperature (°C)

T_cro

initial crop temperature (°C)

T_r

drying chamber temperature (°C)

U_bcr

heat transfer coefficient from bottom of module to drying chamber (W/m² K)

U_tca

heat transfer coefficient from top of module to ambient air (W/m² K)

Q_th,th,ov

overall theoretical thermal energy

Q_th,exp,ov

overall experimental thermal energy

Q_ex,th,ov

overall theoretical exergy

Q_ex,exp,ov

overall experimental exergy

α_c

absorptivity of solar cell

α_cr

absorptivity of crop

β₀

temperature dependent efficiency factor

β_c

packing factor of module

γ

relative humidity

η₀

standard efficiency at standard condition

η_c

solar cell efficiency

η_m

module efficiency

v

wind velocity (m/s)

v₁

air velocity in drying chamber (m/s)

th

thermal

τ_g

transmittivity of glass

Fig. 1a.

Fig. 1b.

Fig. 1c.

Fig. 2.

Fig. 3.

 Table 1

Table 1.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

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• ⁎ 
  Corresponding author.

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