The maximum theoretical performance of unconcentrated solar photovoltaic and thermoelectric generator systems

•Tandem and combined photovoltaic (PV) and thermoelectric generator (TEG) systems are investigated.•An analytical and iterative model based on the Shockley-Queisser limit is derived.•Both TEGs with efficiency given by zT and Carnot engines are considered.•The maximum increase in efficiency is 4.5 pp...

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Bibliographic Details
Published in:Energy conversion and management 2018-01, Vol.156, p.264-268
Main Authors: Bjørk, R., Nielsen, K.K.
Format: Article
Language:English
Subjects:
Carnot
Efficiency
Electricity
Figure of merit
Generators
Mathematical models
Photovoltaic cells
Photovoltaics
Radiation
Solar cells
Solar energy
Sunlight
Temperature dependence
Thermal
Thermoelectric generators
Thermoelectricity
Thermoelectrics
Wavelength
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Summary:•Tandem and combined photovoltaic (PV) and thermoelectric generator (TEG) systems are investigated.•An analytical and iterative model based on the Shockley-Queisser limit is derived.•Both TEGs with efficiency given by zT and Carnot engines are considered.•The maximum increase in efficiency is 4.5 pp for a PV and TEG system compared to a PV alone.•A minimum value of zT is needed for the TEG to contribute positively to the combined efficiency. The maximum efficiency for photovoltaic (PV) and thermoelectric generator (TEG) systems without concentration is investigated. Both a combined system where the TEG is mounted directly on the back of the PV and a tandem system where the incoming sunlight is split, and the short wavelength radiation is sent to the PV and the long wavelength to the TEG, are considered. An analytical model based on the Shockley-Queisser efficiency limit for PVs and the TEG figure of merit parameter zT is presented. It is shown that for non-concentrated sunlight, even if the TEG operates at the Carnot efficiency and the PV performance is assumed independent of temperature, the maximum increase in efficiency is 4.5 percentage points (pp.) for the combined case and 1.8 pp. for the tandem case compared to a stand alone PV. For a more realistic case with a temperature dependent PV and a realistic TEG, the gain in performance is much lower. For the combined PV and TEG system it is shown that a minimum zT value is needed in order for the system to be more efficient than a stand alone PV system.
ISSN:0196-8904
1879-2227
DOI:10.1016/j.enconman.2017.11.009