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Research Papers: Nuclear Power

# Upgrading of Waste Heat for Combined Power and Hydrogen Production With Nuclear Reactors

[+] Author and Article Information
C. Zamfirescu

Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, L1H 74K, Canadacalin.zamfirescu@uoit.ca

G. F. Naterer

Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, L1H 74K, Canadagreg.naterer@uoit.ca

I. Dincer

Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, L1H 74K, Canadaibrahim.dincer@uoit.ca

J. Eng. Gas Turbines Power 132(10), 102911 (Jul 07, 2010) (9 pages) doi:10.1115/1.4000803 History: Received March 06, 2009; Revised September 11, 2009; Published July 07, 2010; Online July 07, 2010

## Abstract

This paper presents a new heat upgrading method that utilizes waste heat from nuclear reactors for thermochemical water splitting with a copper-chlorine (Cu–Cl) cycle. Through combined power, hydrogen, and oxygen generation, the exergy efficiency of a power plant can be significantly augmented. The heat rejected to the environment for moderator cooling, a relatively small amount of low pressure superheated steam and a small fraction of generated power, are extracted from the nuclear reactor and used to drive a Cu–Cl hydrogen plant. More specifically, the moderator heat transfer at $∼80°C$ is used as a source to a newly proposed vapor compression heat pump with a cascaded cycle, operating with retrograde fluids of cyclohexane (bottoming cycle) and biphenyl (topping supercritical cycle). Additionally, the heat pump uses as input the heat recovered from within the Cu–Cl cycle itself. This heat is recovered at two levels: $∼80–130°C$ and $∼250–485°C$. This heat input is upgraded up to $600°C$ by work-to-heat conversion and then used to supply the endothermic water splitting process. The extracted steam is fed into the Cu–Cl cycle and split into hydrogen and oxygen as overall products. Electricity is partly used for an electrochemical process within the Cu–Cl cycle, and also partly for the heat pump compressors. This paper analyses the performance of the proposed heat pump and reports the exergy efficiency of the overall system. The proposed system is about 4% more efficient than generating electricity alone from the nuclear reactor.

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## Figures

Figure 1

Schematic diagram of the Cu–Cl thermochemical water splitting cycle

Figure 2

Ideal heat pump cycles operating between 80°C and 600°C; (a) Carnot cycle and (b) variable temperature cycle

Figure 3

Temperature levels for heating and heat recovery in the Cu–Cl cycle: (a) heating and (b) heat recovery

Figure 4

Proposed heat pump with two cascaded cycles: cyclohexane (bottom cycle) and biphenyl (top cycle). The sign (+) indicates the hot side and (−) cold side of the heat exchanger.

Figure 5

Thermodynamic cycle of the proposed heat pump

Figure 6

Influence of temperature level of condenser-evaporator on COP and COPex

Figure 7

Influence of isentropic efficiency on the heat pump’s performance

Figure 8

Influence of the maximum sink temperature on COP and COPex

Figure 9

Nuclear reactor multigeneration system for power, hydrogen, and oxygen. W is the work, Q is the heat, M (index) is the moderator, R (index) denotes Rankine, and Cu–Cl (index) is the reaction heat.

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