A Structural Review of Thermoelectricity for Fuel Cell CCHP Applications

Table 3

Summary of the eighteen thermoelectricity case studies reviewed.

	Case studies analysed	Highlights, advantages and disadvantages
[4]	Case study A (Bell, 2008)	(i) the principle of thermoelectricity: construction, TEG, and TEC; (ii) : TE device dimensionless figure of merit. More , the better
[3]	Case study B (Gao, 2014)	Showed that TEG can be used as TERs to harvest exhaust heat and boost HT PEM FC efficiency with emphasis on (i) heat exchanger surface type, (ii) its housing dimensions, and (iii) power conditioning
[2]	Case study C (Huston et al., 2004)	(i) about 40 specific applications of TEG were researched and it was noticed that TEG form factor is crucial to enable mounting anywhere; (ii) TEG was used with various FCs to boost output power by 7-10%
[5]	Case study D (Zhao et al., 2016)	Showed how energy was harnessed from intermittent heat sources and converted into stored charge via the ionic Soret effect in an ITESC. Max efficiency is very low compared to TEG of the same
[6]	Case study E (Mahmud et al., 2017)	Demonstrated that TEGs connected in series and parallel generate more voltage and current, respectively, that also increases with
[7]	Case study F (Qu et al., 2018)	Developed a thermodynamic model for the TEG and microturbine. Showed that TEG almost doubled the hybrid CHP output power
[8]	Case study G (Katkus, 2015)	The manufacturing of a TEG involve choosing a TE material with good (>1), electrodes insulating plate, adhesives, and module architecture. A real system was built to characterise TEG modules
[20]	Case study H (Sullivan, 2012)	Modelled TEGs and TECs on a chip. TECs are more efficient using more and better if operated at a steady state for frequent hotspots. For infrequent hotspots, TECs may be cooled with square root transient pulses of a very short duration. TEG MPT occurred at greater load resistance. TEG useful power is firstly linear and later parabolically proportional to the heat flux. More TEGs increase output power but decrease later. Thinner TIM improves TEC and TEG capabilities
[10]	Case study I (Teffah et al., 2018)	TEC was used as a TEG cooler in simulated and practical setups. The was directly proportional to the TEC and TEG
[21, 22]	Case study J (Stockholm, 2016)	Demonstrated that the output power from TEG when pulsed doubles the conversion efficiency. An 8.4% increase was attained
[9]	Case study K (Kiziroglou et al., 2016)	Proved that thicker TEGs with good area coverage can be used to harvest electricity from the environment with fluctuating temperatures
[14]	Case study L (Sulaiman et al., 2017)	Showed the use of a TEG with FC under simulated natural (static) and forced convection cooling (dynamic) to convert heat to power; However, very high is required to generate significant power
[15]	Case study M (Hasani and Rahbar, 2015)	Demonstrated the duality of TECs as TEGs in a FC CHP using a THRS. Low gave low . MPT occurred at of 1–10 Ω
[23]	Case study N (Park et al., 2014)	Showed the use of a low-cost microcontroller and temperature sensor-based circuit, to track TEG MPP with a 1.1% tracking error
[24]	Case study O (Yildiz et al., 2013)	Compared TEG and solar energy conversion. A TEG generates more power relative to solar module of same size but more costly
[27]	Case study P (Apertet et al., 2014)	Deduced that a TEG output power and efficiency in a thermal environment can be simultaneously maximised if its heat flux is constant but not the case if its temperature difference is constant
[25]	Case study Q (Ebrahimi and Derakhshan, 2018)	Proved that a TEC LT-PEM FC hybrid CCHP system is capable of producing 2.79 kW of electricity, 3.04 kW of heat, and 26.8 W of cooling with a total efficiency of ~77% and fuel saving of 43.25%
[50]	Case study R (Mamur and Çoban, 2020)	TEGs have no moving parts, have long service life, operate quietly, and are green. TEGs have low efficiency and are expensive. By using the manufacturer datasheets, TEGs were modelled, simulated, experimented, and result correlated. Impedance matching with boost converter and P&O MPPT schemes gave 98.64% efficiency