Design of Molten Carbonate Fuel Cell (MCFC) and Homogeneous Charge Compression Ignition (HCCI) Engine Hybrid System for Distributed Power Generation

Abstract

Recently, various energy issues, e.g. depletion of natural resources and growing environmental concerns, have been encountered year by year. For the reason, the demand for renewable power source increases, and fuel cell technology draws interest as a good applicant in the field due to high efficiency and low pollutant. In the previous work, a new MCFC hybrid system integrated with HCCI engine was developed. In the hybrid system, the HCCI engine replaces the catalytic combustor in the original fuel cell system and yields additional power by using the left-over fuel in the anode off-gas. In this thesis, the engine design is performed for the 250 kW-class MCFC system. For the thermodynamic analysis, thermodynamic modeling is performed and the parametric study is conducted with design options variation. With the determined engine specification, the hybrid system is analyzed at the design point and part-load operation. The hybrid system efficiency can achieve 57.1 %, which is 9.8 % higher than the standalone system efficiency at the design point operation. And the systematic control strategies are developed at the part-load conditions, and thus the hybrid system can operate at the various fueling levels. An economic assessment is also conducted for comparison between the standalone system and the hybrid system. The analysis is performed by calculating the levelized cost of electricity (LCOE) with total revenue requirement (TRR) method. The LCOE of the hybrid system is ~5.4 % lower than that of the standalone system, thus the economic feasibility of the hybrid system was verified. Based on the simulation results, the engine experiment is conducted to demonstrate the possibility of the HCCI engine operation in the system. As a result, the engine net indicated efficiency is measured to be ~17 %. Considering the small displacement volume of the tested engine with its relatively un-favorable heat transfer characteristic, the engine performances in the hybrid system are shown to be quite promising. It is anticipated that the results of this thesis would be considered the study leading up to the commercialization of the new MCFC-HCCI engine hybrid system for distributed power generation in near-future.