Economics of hydrogen production and utilization strategies for the optimal operation of a grid-parallel PEM fuel cell power plant

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Abstract

This paper integrates the hydrogen production and utilization strategies with an economic model of a PEM fuel cell power plant (FCPP). The model includes the operational cost, thermal recovery, power trade with the local grid, and hydrogen management strategies. The model is used to determine the optimal operational strategy, which yields the minimum operating cost. The optimal operational strategy is achieved through estimation of the following: hourly generated power, thermal power recovered from the FCPP, power trade with the local grid, and hydrogen production. An evolutionary programming-based technique is used to solve for the optimal operational strategy. The model is tested using different seasonal load demands. The results illustrate the impact of hydrogen management strategies on the operational cost of the FCPP when subjected to seasonal load variation. Results are encouraging and indicate viability of the proposed model.

Introduction

Alternate energy sources of power generation have gained tremendous interest due to depletion of conventional energy sources and their adverse environmental effects. Among the various types of alternate energy sources, fuel cell power plants (FCPPs) have been the focus of interest since such plants are capable of producing electricity, heat, and hydrogen. In such type of systems, unused capacity of the FCPPs can be harnessed to produce hydrogen. The hydrogen produced can, (a) be stored/reused by the FCPP to produce electrical energy or, (b) be sold to other customers for a profit. The literature [1], [2], [3], [4], [5], [6], [7], [8], [9] indicates that using the FCPP for the exclusive production of electrical energy is not cost effective. Economics suggest therefore, that utilization of the wasted thermal energy in addition to the production of hydrogen will materially improve the competitiveness of the FCPP in the power market.

To decrease the overall operational cost it is necessary therefore to develop an optimal operational strategy that utilizes the otherwise wasted thermal energy and manages the utilization of the produced hydrogen. The focus of this paper is to develop a cost based model of an FCPP system that is subjected to different hydrogen management strategies.

In [1], [2] an economic model has been introduced to estimate the optimal output power from the FCPP while satisfying system operational constraints. This simple model considers only the possibility of selling and buying energy from the local grid and the utilization of thermal power output from the FCPP.

In this paper, the model presented in [1], [2] has been extended to include the management of hydrogen utilization. The economic model is constructed as a cost optimization problem subject to system and operational constraints. To estimate the daily optimal operational strategy for the FCPP, a hybrid technique based on evolutionary programming (EP) and Hill-Climbing (HC) method [1], [10] is used. The evolutionary programming is employed to search for the near optimal solution while the HC method is used to ensure feasibility during the solution process.

The paper is organized as follows: Section 2 introduces an economic model for an FCPP system. Section 3 presents the solution methodology. Test results are presented in Section 4 and Section 5 presents the conclusions.

Section snippets

Fuel cell system economic model development

In this model many different strategies are developed to handle excess electrical and thermal energy and hydrogen production.

Evolutionary programming (EP)-based solution methodology

Evolutionary programming can be traced back to the early 1950’s when Turing discovered a relationship between machine learning and evolution [13], [14], [15]. Later, Bremermann, Box, Friedberg, and others developed evolutionary computation as a tool for machine learning and optimization. Great attention was given to EP as a powerful tool when Fogal, Burgin, Atmar, and others used it to predict the events of finite state machines on the basis of old observations. During the 1980’s evolutionary

Tests and results

The proposed model has been applied to a 250 kW grid-parallel FCPP that supplies a residential neighborhood. The IEEE-RTS load profile with a peak of 250 kW [17] is used to simulate the hourly electrical load profile of the system operation. In this test system, the weekly, daily and hourly peak load values are given in percent of annual, weekly and daily peak loads, respectively. Hot water usage and space heating rates for the winter in Atlanta, Georgia [12] is considered to represent the

Conclusions

In this paper, the impact of hydrogen production and storage on the optimal cost of operation of a PEM FCPP operating in a grid-parallel mode is presented. The economic model of the operational cost of the FCPP has been developed, which includes power trade with the local grid, thermal recovery, and hydrogen production/storage. The paper offers practical concepts concerning operational cost modeling of the FCPP. The model incorporates three different strategies for hydrogen production and

M. Y. El-Sharkh received his B.Sc. and M.Sc. from Ain Shams University, Cairo, Egypt in 1987, and 1990 respectively all in electrical engineering. He obtained the Ph.D. degree from the University of Alabama at Tuscaloosa in 2002. His research interests include using the new optimization techniques in solving the power system operation problems, power system stability and alternate sources of energy.

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M. Y. El-Sharkh received his B.Sc. and M.Sc. from Ain Shams University, Cairo, Egypt in 1987, and 1990 respectively all in electrical engineering. He obtained the Ph.D. degree from the University of Alabama at Tuscaloosa in 2002. His research interests include using the new optimization techniques in solving the power system operation problems, power system stability and alternate sources of energy.

M. Tanrioven received his B.Sc., M.Sc. and PhD from Yildiz Technical University, Istanbul, Turkey in 1993, 1996, and 2000 respectively all in electrical engineering. His research interests include power system, power quality and harmonics, fuzzy systems, alternate sources of energy. He is currently engaged in post-doctoral research at the University of South Alabama, Mobile, USA.

A. Rahman received the Ph.D. degree in electrical engineering from the University of Kentucky in 1974. He is currently an Associate Professor of Electrical and Computer Engineering at the University of South Alabama. His research interests are in the areas of electrical machines, power electronics and power systems. He is a life senior member of IEEE and member of ASEE.

M. Alam is a Professor of Electrical and Computer Engineering at the University of South Alabama. His research interests include smart energy management, ultrafast computer architectures and algorithms, signal/image processing, pattern recognition, and digital system design. He is a Fellow of OSA, a Fellow of the SPIE, a senior member of IEEE, a member of ASEE and AIP.

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