Abstract
Recent developments of high performance thermoelectric (TE) materials have increased the interest of using this technology to directly convert waste heat into electricity. In the automotive sector, many automotive thermoelectric generators (ATEGs) designs use TE modules (TEMs) with high hot side temperatures to cope with high engine load regimes. Here, we develop a new concept of a radial ATEG that is specifically designed to work with low temperature TEMs, which enables the use of Pb-free modules and reduces the thermal stress of the device. A prototype is built and tested at different regimes in an engine test bench. A numerical model of the ATEG is developed and validated. The consequences of modifying (1) the exchange area between the heat absorber and the exhaust gases and (2) the effective figure of merit of TEMs on the electrical output power and fuel economy are investigated by means of simulations. Results indicate that the maximum fuel economy (1.3%) is not attained at the point of maximum output power (228 W). In terms of fuel economy, the back pressure at the exhaust penalizes high mass flow regimes. We use a dimensionless parameter to analyze the potential of the ATEG for reducing fuel consumption.
Highlights
Transport contributes to more than 20% of carbon dioxide (CO2 ) emissions worldwide [1].In Europe, this contribution rises up to 27%, becoming the biggest source of carbon emissions and the main cause of air pollution in cities [2]
We develop a new concept of a radial automotive thermoelectric generators (ATEGs) that is designed to work with low temperature TE modules (TEMs), which enables the use of Pb-free modules and reduces the thermal stress of the device
Since PATEG is proportional to ΔT2, the average increase in PATEG with reference to the initial design tested in the engine bench (Section 2) was 23%, 49%, and 75% when the total fin surface area of the absorber increased by 20%, 40%, and 60%, respectively
Summary
Transport contributes to more than 20% of carbon dioxide (CO2 ) emissions worldwide [1]. The heat absorbers of the ATEG may be circular tubes [7], straight fins [8,9,10,11], dimples [12], phase-change pipes [13], etc., and, to some extent, all of them increase the pressure upstream of the exhaust pipe This back pressure alters the regular functioning of the engine and increases the fuel consumption. Maximum values of fuel economy due to ATEGs are commonly not reported (see Table 1), values on the order of 1% have been estimated [10] These are slightly lower values than those claimed by using ORCs (up to 7% [16]), back pressure and weight effects in real on-vehicle tests may substantially reduce this figure, even leading to increments in fuel consumption [17].
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