Modeling assisted evaluation of direct electricity generation from waste heat of wastewater via a thermoelectric generator

Shiqiang Zou; Eurydice Kanimba; Thomas E Diller; Zhiting Tian; Zhen He

doi:10.1016/j.scitotenv.2018.04.201

Modeling assisted evaluation of direct electricity generation from waste heat of wastewater via a thermoelectric generator

Sci Total Environ. 2018 Sep 1:635:1215-1224. doi: 10.1016/j.scitotenv.2018.04.201. Epub 2018 Apr 24.

Authors

Shiqiang Zou¹, Eurydice Kanimba², Thomas E Diller², Zhiting Tian³, Zhen He⁴

Affiliations

¹ Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
² Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
³ Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. Electronic address: zhiting@vt.edu.
⁴ Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. Electronic address: zhenhe@vt.edu.

PMID: 29710576
DOI: 10.1016/j.scitotenv.2018.04.201

Abstract

The thermal energy represents a significant portion of energy potential in municipal wastewater and may be recovered as electricity by a thermoelectric generator (TEG). Converting heat to all-purpose electricity by TEG has been demonstrated with large heat gradients, but its application in waste heat recovery from wastewater has not been well evaluated. Herein, a bench-scale Bi₂Te₃-based waste heat recovery system was employed to generate electricity from a low temperature gradient through a combination of experiments and mathematical modeling. With an external resistance of 7.8 Ω and a water (hot side) flow rate of 75 mL min^-1, a maximum normalized energy recovery of 4.5 × 10^-4 kWh m^-3 was achieved under a 2.8 °C temperature gradient (ΔT). Model simulation indicated a boost in both power output and energy conversion efficiency from 0.76 mW and 0.13% at ΔT = 2.8 °C to 61.83 mW and 1.15% at ΔT = 25 °C. Based on the data of two-year water/air temperature obtained from the Christiansburg Wastewater Treatment Plant, an estimated energy generation of 1094 to 70,986 kWh could be expected annually with a saving of $163 to $6076. Those results have revealed a potential for TEG-centered direct electricity generation from low-grade heat towards enhanced resource recovery from wastewater and encouraged further exploration of this approach.

Keywords: Energy recovery; Mathematical modeling; Thermoelectric generator; Waste heat; Wastewater.