Increasing energy and exergy efficiency in photovoltaic panels by reducing the surface temperature with thermoelectric generators

ABSTRACT

Many factors affect the efficiency of photovoltaic panels (PV), which convert solar energy directly into electrical energy. Among these factors, temperature is one of the most important one. While some of the radiation from the sun is converted into electrical energy, part of it emerges as heat energy. This causes the photovoltaic cells to heat up and reduce their electrical efficiency. Different methods are used in the literature to reduce the temperature in PV panels. In this study, in order to reduce the adverse effects caused by the high temperature in the PV panels, 30 Thermoelectric Generators (TEG) were applied to the back surface of the PV panel to increase the PV panel output power and to produce additional electrical energy. Energy and exergy analysis made on the data obtained from both PV panels in the climatic conditions of the installation site showed that the temperature of the PV panel is reduced, and the energy and exergy efficiency is increased with the TEG application. At the end of July, August, and September, when the experiments were carried out, an average of 8.4% more electrical energy was obtained from a single PV panel with TEG, compared to the standard PV panel. Our results suggests that combination of TEG with PV panels could significantly increase the electrical energy, especially when a series of PV panels are used together.

KEYWORDS:

• Photovoltaic
• temperature
• power
• energy
• exergy

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

PV	=	Photovoltaic
G	=	Solar irradiation (W/m2)
I	=	Electrical current (A)
V	=	Voltage (V)
Ic	=	TEG supply current (A)
P	=	Power (W)
τ	=	Transmissivity
α	=	Absorptivity
TEG	=	Thermoelectric Generator
ZT	=	Dimensionless figure of merit
Qin/A	=	Heat flux density (mW/cm2)
Th	=	Hot-side temperature (K)
Tc	=	Cold-side temperature (K)
Rc	=	Electrical contact resistance
ρc	=	Contact resistivity (Ω∙m2)
σ	=	Electrical conductivity (S/m)
S	=	Seeback coefficient (µV/K)
A	=	Surface area (cm2)
η	=	Efficiency (%)
k	=	Thermal conductivity (W/m∙K)
FF	=	Fill factor
${\dot{\mathrm{E}}}_{\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{a}\mathrm{r}}$	=	Solar radiation energy (W)
${\dot{\mathrm{E}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}$	=	Energy output (W)
${\dot{\mathrm{E}}}_{\mathrm{i}\mathrm{n}}$	=	Energy input (W)
$\dot{\mathrm{E}}{\mathrm{x}}_{\mathrm{o}\mathrm{u}\mathrm{t}}$	=	Exergy output (W)
$\dot{\mathrm{E}}{\mathrm{x}}_{\mathrm{i}\mathrm{n}}$	=	Exergy input (W)
$\dot{\mathrm{E}}{\mathrm{x}}_{\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{c}}$	=	Electrical exergy (W)
${\mathrm{P}}_{\mathrm{T}\mathrm{E}\mathrm{G}}$	=	Power generated by thermoelectric generator (W)