Solid Oxide Fuel Cell Cogeneration System Research Articles

Proposal and assessment of a solid oxide fuel cell cogeneration system in order to produce high-temperature steam aiming at industrial applications

The feature of operating at high temperature enables solid oxide fuel cell (SOFC) generating power at impressive efficiency while providing useful heat. Commercial SOFC cogeneration products for domestic hot water supply are already available, however, the potential of supplying high-temperature heat (especially in the form of steam) for industrial applications has not been well exploited yet. Here, a new SOFC cogeneration system layout is proposed and studied to address the problem. The core idea is to utilize the residual heat in parallel by the method of splitting the high-temperature streams, rather than in cascade as in traditional layouts. Therefore, the application of SOFC cogeneration can be expanded from providing low-temperature heat to high-temperature heat, from homes to industries. The simulation result shows that the layout with anode gas recycle (AGR) has the best performance in both net and cogeneration efficiency. The best predicted net efficiency is 56.9% and cogeneration efficiency 86.8% for the AGR layout. For the AGR layout with a net capacity of 10MW, the steam production ability of medium, low and super low pressures are 5903kg/h, 6436kg/h and 6748kg/h, respectively. The investigated gas split locations only have negligible effect on the steam production ability.

CFD Modeling of SOFC Cogeneration System for Building Application

Abstract This paper focuses on CFD modeling of Solid oxide fuel cell (SOFC) which is coupled with co-generation system. The SOFC cogeneration system is a low emission and energy efficient combined heat and power (CHP) is a most promising candidate in the field of electric and thermal energy generation technology for execution in future commercial buildings. Using finite volume approach CFD modeling of SOFC has been carried out by using commercial software COMSOL 4.3.1. The performance characteristic of an SOFC has been examined by performing parametric analysis. The effect of fuel utilization factor, recirculation ratio, operating temperature significantly affects the cell performance. It has been observed that, internal reforming is advantageous over the external reforming system in terms of thermo-economics and power supply.

電力・給湯需要のばらつきが固体酸化物形燃料電池コージェネレーションシステムの導入効果に与える影響<br>集合住宅へのコージェネレーションシステムの導入方法に関する研究 その1

Installation of residential solid-oxide fuel cell cogeneration system (SOFC-CGS) has been promoted as an energy-saving measure. Although SOFC-CGS is becoming popular among detached housing, the installation of SOFC-CGS in apartment buildings can also be effective in reducing residential energy consumption. In this study, the effectiveness of SOFC-CGS installation in an apartment building is evaluated by considering the variation of eletricity and hot water demands in different household settings. In order to simulate the demands, parameters are formulated and randomly distributed in a 50-unit apartment building model. The reduction rate of energy consumption by SOFC-CGS installation is generated for each unit and the impact of each parameter is examined.

Energy Performance of SOFC Cogeneration System for Residential Buildings in Chinese Cold Areas

Primary energy reduction and energy efficiency improvement are important targets to be achieved in every society and in residential buildings in particular. An energy-efficient and low-emissions solid oxide fuel cell (SOFC) cogeneration system is a promising electric and thermal energy generation technology for implementation in future residential buildings. This paper aims to analyze the energy performance in terms of primary energy demand and its reduction rate when SOFC cogeneration system is used in residential buildings. This study outlines SOFC cogeneration system and its simulation method, and then develops a standard family model for simulation under cold weather condition in China and selected Beijing city as an example, and finally compares them with traditional power and heat generation system based on gas and electricity. The results show that SOFC cogeneration system is an energy-efficient alternative power and thermal energy cogeneration technology for cold climatic cities such as Beijing, and can offer a large reduction rate (about 15.8% in winter) of primary energy demand in residential buildings. This study also finds that the significant reductions in primary energy demand of SOFC system result for the periods with air temperature decreasing.

Energetic analysis of SOFC co-generation system integrated with EV charging station installed in multifamily apartment

The authors propose a solid oxide fuel cell (SOFC) co-generation system integrated with an electric vehicle (EV) charging station. To examine the feasibility of the proposed system, the authors numerically simulated the operation pattern of the proposed system, using the electric and thermal demands measured at a multifamily apartment from May 2003 to April 2004. Based on the simulation results, the authors calculated the overall efficiency of the system as well as the primary energy saving rate. The available electric energy for EV charging was also evaluated for the case of the proposed system installed in the multifamily apartment. As a result, it is made clear that the annually averaged overall efficiency reaches about 77% (LHV) and the expected primary energy saving rate exceeds 30% throughout the year. In addition, it is also found that sufficient amount of electric energy for EV charging can be obtained from the proposed system. Therefore, it can be concluded that the proposed SOFC system can successfully combine electrical/thermal energy co-generation and electric vehicle charging while maintaining high energy efficiency and good matching to energy consumption patterns.

Field Test Results Of Residential SOFC Co-Generation System At Tokyo Gas

Field test results of residential SOFC co-generation system at Tokyo Gas T. Ishikawa, S. Yamashita Product Development Dept., Tokyo Gas Lo., LTD., Tokyo, JAPAN We are developing residential SOFC co-generation system in order to commercialize it. One of our activities is to operate SOFC systems in field tests to make sure effects of installation and find technical issues. The detail is as below. A serious accident at nuclear power plants in Fukushima which was triggered by a huge earthquake on 11th March 2011 forces drastic re-formulation of Japan’s energy policy. In a series of discussions on the new energy policy, promoted use of distributed power generation is demanded more than ever as one of the main power systems, with extremely strong expectations for the fuel cell co-generation system. Tokyo Gas has been conducting research and development of solid oxide fuel cell (SOFC) which is expected to achieve the highest efficiency among all distributed power systems. In parallel with it, to verify the applicability of the SOFC for residential use and to identify technical challenges of SOFC, we have started field tests of SOFC systems of multiple manufacturers in the “Solid Oxide Fuel Cell (SOFC) demonstrative research project” with financial support from NEDO (Figure 1) [1][2]. We have installed a total of 23 units of four manufacturers in the field test of over four years (from 2007 to 2010), of which 14 units are still under operation as of April 30, 2012 (table 1). And the operating time has reached 18,600 hours at the longest, with 268,500 hours in total of 23 units. We have acquired the knowledge as shown below during the field tests conducted at general residences which we selected to reflect a variety of electrical and hot water demands (Figure 2). (1) Residential SOFC co-generation system contributes to the saving the preliminary energy consumptions and CO2 emissions by households in Japan (Figure 3, Figure 4). (2) SOFC system shows high electricity efficiency exceeding 45%LHV, and the transition of efficiency indicates that the durability of SOFC system including cell stack is estimated to be almost practical use (Figure 5). (3) SOFC system shows high reliability because of its simple system configuration. We will report the detailed results of SOFC field tests based on the latest data. Acknowledgments Finally, we would like to express our appreciation to NEDO, as this report is prepared mainly based on the results of the project supported by NEDO. Figure 2 Residential Demand (/Month) References [1] Solid Oxide Fuel Cell demonstrative research project final report (2011) http://www.nef.or.jp/sofc/share/pdf/h22y.pdf [2] Y. KAWABATA, T.SEYAMA, T.SOBUE, International Gas Union Research Conference ( 2011 ) Development and Field Test of Residential SOFC Co-generation System with All-ceramics-segmented Cells

Feasibility study on combined use of residential SOFC cogeneration system and plug-in hybrid electric vehicle from energy-saving viewpoint

The energy-saving effect of a combined use of a residential solid oxide fuel cell cogeneration system (SOFC-CGS) that adopts a continuous operation, and a plug-in hybrid electric vehicle (PHEV) is discussed by optimal operational planning based on mixed-integer linear programming. This combined use aims to increase the electric capacity factor of the SOFC-CGS by charging the PHEV using the SOFC-CGS electric power output late at night, and targets the application in regions where the reverse power flow from residential cogeneration systems to commercial electric power systems is not permitted, like in Japan. The optimal operation patterns of the combined use of 0.7-kWe SOFC-CGS and PHEV for a simulated energy demand with a sampling time of 1h and various daily running distances of the PHEV show that this combined use increases the electric capacity factor of the SOFC-CGS and saves more energy in comparison with their separate use in which the SOFC-CGS is used but the PHEV is charged only with purchased electric power. Furthermore, it is found that at the PHEV daily running distance of 12km/d, the reduction rate of the annual primary energy consumption for this combined use increases by up to 3.7 percentage points relative to their separate use. Consequently, this feasibility study reveals that the combined use of the SOFC-CGS and PHEV provides the synergistic effect on energy savings in the residential and transport sectors. For the practical use, simulation scenarios considering the energy demand fluctuations with short periods and real-time pricing of the purchased electric power must be considered as future issues.

Development of Residential SOFC Cogeneration System

Since 2001 Kyocera has been developing 1kW class Solid Oxide Fuel Cell (SOFC) for power generation system. We have developed a cell, stack, module and system. Since 2004, Kyocera and Osaka Gas Co., Ltd. have been developed SOFC residential co-generation system. From 2007, we took part in the "Demonstrative Research on Solid Oxide Fuel Cells" Project conducted by New Energy Foundation (NEF). Total 57 units of 0.7kW class SOFC cogeneration systems had been installed at residential houses. In spite of residential small power demand, the actual electric efficiency was about 40%(netAC,LHV), and high CO2 reduction performance was achieved by these systems. Hereafter, new joint development, Osaka Gas, Toyota Motors, Kyocera and Aisin Seiki, aims early commercialization of residential SOFC CHP system.

STUDY ON ENERGY CONSERVATION EFFECTS OF HOUSING ELECTRICITY AND HEAT SOURCE EQUIPMENTS

This paper presents effects of housing electricity and heat source equipments. We studied about energy saving effects of 4 equipments, CO2 Heat Pump water heater (CO2-HP), Micro Gas Engine Co-Generation System (GE-μCGS), Polymer Electrolyte Fuel Cell Co-Generation System (PEFC-CGS), and Solid Oxide Fuel Cell Co-Generation System (SOFC-CGS). As the result, we have found that energy consumption and CO2 emission reduction rate is the highest in case of SOFC-CGS. Energy consumption is reduced by 17-20% using SOFC-CGS on Electric Power Load Tracking Operation, and 44-47% on Rated Operation. And CO2 emission is reduced by 5-20% on Electric Power Load Tracking Operation and 22-46% on Rated Operation.

Suitable operational strategy for power interchange operation using multiple residential SOFC (solid oxide fuel cell) cogeneration systems

A suitable operational strategy for a power interchange operation using multiple residential solid oxide fuel cell (SOFC) cogeneration systems for saving energy is investigated by an optimization approach based on mixed-integer linear programming. In this power interchange operation, electricity generated by residential SOFC cogeneration systems is shared among households in a housing complex without allowing a reverse power flow to a commercial electric power system in order to increase electric load factors of the system. For an SOFC cogeneration system operated continuously with the minimum output, two types of operational strategies for the power interchange operation are adopted: an operation to meet the total demand for electricity in intended households by the electricity output of SOFC cogeneration systems and an operation to meet the demand for hot water in each household by the hot water output of the SOFC cogeneration system. To clarify a theoretical limit of the energy-saving effects of the two strategies, this study numerically analyzes optimal operation patterns for 20 households on three representative days. The results show that the former operational strategy, which takes advantage of the high electricity generating efficiency of the SOFC, is more suitable for saving energy as compared to the latter strategy.

SOFC cogeneration system for building applications, part 2: System configuration and operating condition design

An SOFC (Solid Oxide Fuel Cell) cogeneration optimization study was carried out for one small-scale and one large-scale building under both hot and cold weather conditions. Several different configurations of the SOFC system are operated using a defined set of input parameters to meet the actual heating, cooling and electrical demands on those two buildings The results are discussed and compared from four different perspectives: electric-only vs. cogeneration, energetic vs. economic, large-scale vs. small-scale buildings and hot vs. cold weather conditions. The main conclusion of this study is that optimization results vary widely depending on different system configurations and loading conditions and thus SOFC systems should be optimized based on the specific conditions to which they are exposed and not simply on a single operating condition.

SOFC cogeneration system for building applications, part 1: Development of SOFC system-level model and the parametric study

A thermal and electrochemical model is developed for the simulation of Solid Oxide Fuel Cell (SOFC) cogeneration system in this study. The modeling algorithms of electrochemical and thermal models are described. Since the fuel cell stack itself is only a single component within the whole SOFC system, the modeling of the balance-of-plant (BOP) components is also performed to assess the system-level performance. Using the new model, a parametric analysis is carried out to investigate the effects of fuel flow rate, extent of methane gas pre-reforming, fuel utilization factor, recycling rate of cathode gas and cell voltage on the overall system performance. As a result of the parametric study, fuel flow rate, cell voltage, fuel utilization and recycling rate of cathode gas turned out to improve system power output. In addition, the internal reforming turned out to have advantage over external reforming in terms of system power supply.

The financial viability of an SOFC cogeneration system in single-family dwellings

In the near future, fuel cell-based residential micro-CHP systems will compete with traditional methods of energy supply. A micro-CHP system may be considered viable if its incremental capital cost compared to its competitors equals to cumulated savings during a given period of time. A simplified model is developed in this study to estimate the operation of a residential solid oxide fuel cell (SOFC) system. A comparative assessment of the SOFC system vis-à-vis heating systems based on gas, oil and electricity is conducted using the simplified model for a single-family house located in Ottawa and Vancouver. The energy consumption of the house is estimated using the HOT2000 building simulation program. A financial analysis is carried out to evaluate the sensitivity of the maximum allowable capital cost with respect to system sizing, acceptable payback period, energy price and the electricity buyback strategy of an energy utility. Based on the financial analysis, small (1–2 kW e) SOFC systems seem to be feasible in the considered case. The present study shows also that an SOFC system is especially an alternative to heating systems based on oil and electrical furnaces.

2256 10kW 級 SOFC システムの開発

The Solid Oxide Fuel Cell (SOFC) is composed of ceramics of the solid, and has the feature of high power generation efficiency and flexibility of fuel. TOTO LTD. has been conducting research and development of Tubular Type SOFC since 1989. We succeeded in the power generation of 3kW stack in 2000. Now we are developing the thermally self-sustaining module since 2001. Our development target is 10kW class SOFC cogeneration system for a apartment and a small-scale business use.

448 10kW 級 SOFC システムの開発

The Solid Oxide Fuel Cell (SOFC) is composed of ceramics of the solid, and has the feature of high power generation efficiency and flexibility of fuel. TOTO LTD. has been conducting research and development of Tubular Type SOFC since 1989. We succeeded in the power generation of 3kW class in 2000. Now we are developing the thermally self-sustaining module since 2001. Our development target is 10kW class SOFC cogeneration system for a housing complex and a small-scale business use.

Verification Test of a 25kW Class SOFC Cogeneration System

Osaka Gas and Tokyo Gas have high expectations for natural-gas-fueled Solid Oxide Fuel Cell (SOFC) cogeneration systems. SOFC offers many advantages for on-site cogeneration systems, such as high electrical efficiency, high quality by-product heat and low emissions. They are now executing a joint development program with Westinghouse Electric Corporation (hereinafter called as WELCO). This program is aimed to verify a 25kW class SOFC cogeneration system. This system, which was modified by replacing previous zirconia porous support tube cells (PST cells) with newly designed air electrode supported cells (AES cells), commenced operation on March 21, 1995. The system has been successfully operated for 13,100 hours as of February 7, 1997. This paper presents the performance evaluation of the new AES cells and the results of system operation at WELCO.