Polymer Electrolyte Fuel Cell Cogeneration Research Articles

Dealing with uncertainty in automated operational planning for residential fuel cell system: A comparative study of state-of-the-art approaches

Polymer electrolyte fuel cell cogeneration systems (PEFC-CGSs) provide hot water by utilizing exhaust heat produced in electricity generation process. The energy saving potential of PEFC-CGSs can be maximized by optimal operational plans, and most state-of-the-art approaches implement operational planning function (OPF) based on energy demand time-series prediction by using machine learning techniques. In general, prediction of demand time-series with small expected average errors is regarded as the most important point in obtaining appropriate operational plans; however, several recent studies have revealed that other complex factors such as the direction and timing of forecast errors greatly affect the quality of operational plans in some cases. Core ideas proposed in these previous studies are broadly classified into seven types. The purpose of this study is to characterize these OPFs from the two aspects: the output form of prediction model and prediction target variable, and to clarify “what kind of uncertainty should be focused on” and “how this uncertainty should be handled” in designing OPF. The seven kinds of OPFs were comprehensively evaluated via numerical simulations using real-world data. The results show the significance of OPF based on prediction of expected operational cost surface using multiple output prediction model.

Operational Planning of a Residential Fuel Cell System for Minimizing Expected Operational Costs Based on a Surrogate Model

This study proposes a novel operational planning method for polymer electrolyte fuel cell cogeneration systems (PEFC-CGSs). PEFC-CGSs provide hot water by utilizing waste heat produced in the electricity generation process, and hot water is stored in an attached tank. Generating and storing hot water based on an optimal operational plan according to household demand leads to further energy saving; therefore, operational planning methods based on household demand prediction have received significant attention. However, the improvement in the demand prediction accuracy does not necessarily lead to efficient PEFC-CGS operation in terms of operational costs; in other words, the accuracy in the demand prediction does not directly indicate the resulting operational efficiency. In this study, the authors propose a novel approach based on a surrogate model for deriving an appropriate plan that minimizes the expected operational costs among the operational plan candidates. In the proposed scheme, the error between expected and actual operational costs explicitly represents the relevance of the operational plan, so that the optimal operational plan can be selected directly from the perspective of the resulting operational efficiency. The practicality of the proposed approach is evaluated with the existing demand prediction-based approach via numerical simulations using real-world measurements of multiple customers in Japan. The proposed method reveals 30% reduction of the excessive operational costs by avoiding the inefficient operation of the auxiliary gas-heater in the experiments and will further enhance the value of introducing highly efficient residential fuel cell system that contributes to a low-carbon society.

Analysis of operation plans of residential PEFC–CGS: a perspective of cost optimality under demand uncertainty

This study mainly aimed to compare operation planning schemes for polymer electrolyte fuel cell cogeneration systems (PEFC–CGSs) to analyze derived operation plans from various perspectives. PEFC–C...

貯湯量に関する周期境界条件を考慮した家庭用PEFCコージェネレーションシステムの最適運用計画

This paper proposes a new operational planning method for residential PEFC (Polymer Electrolyte Fuel Cell) cogeneration system considering the periodical boundary conditions concerning hot water in storage tank. It can be easily expected that residential PEFC cogeneration system is likely to produce more hot water than needed, because heat efficiency of PEFC is higher than its electrical efficiency. In that case, the surplus hot water would be discarded, and it might deteriorate total operational cost. However, previous researches have not discussed and focused on how to deal with the surplus hot water, and when to discard it. Therefore, we introduce periodical boundary conditions concerning hot water amount in storage tank, and include the cost of disposal hot water as the penalty into our objective function in order to consider them in the operational planning. We simulate the operational planning in the conditions of 3 seasons by using 2 methods, which are proposed method considering periodical boundary constraints and conventional method of operational planning. The study system is configured of PEFC, commercial grid, storage tank, and auxiliary gas boiler. The simulation results show the efficacy of proposed method in many cases. In addition, the bird's-eye view figures composed of optimal solutions reveal some information about the way to decide the appropriate periodical boundary conditions.

Improved Optimal Operation Planning Method Based on Tabu Search for Residential PEFC-CGS Considering Ramping Rate

This paper proposes an improved optimal operation planning method for residential PEFC-CGS (Polymer Electrolyte Fuel CellCo-Generation System). Residential PEFC-CGS has recently been gathering attention as one of the distributed power sources with high efficiency and low environmental impacts. Previous research pointed out that the output variations of PEFC adversely affect the durability. It can be surmised that smaller output variations will be desired to extend durability years. However, in this field, ramping rate have not been sufficiently considered. For local search and tabu search, ramping rate constraint makes our operation planning difficult because it restricts the search for feasible neighborhood solutions. Therefore, the authors proposed a method to deal with typical and harsher ramping rate constraints in comparison with conventional methods. There are two key points for the improvement. One is the reinforcement of the search along the output power axis; the other is to make use of the strategy of tabu search which avoids the local optimal solutions. The simulation results show the effectiveness of the proposed method in the daily operation planning. Furthermore, in the case using typical ramping rate parameter, it is confirmed that tabu search doesn’t contribute the reduction of daily operational cost due to the above stated restriction of the search area.

S0830203 家庭用PEFC-CGSにおける需要予測精度が省エネルギー性に与える影響の分析

The main objective of this study is to clarify the impact of energy demand prediction accuracy on optimal operating result of residential energy supply system. In this paper, the energy system consists of polymer electrolyte fuel cell cogeneration system and electrical-driven heating, ventilating and air conditioning system. Primary energy of operational results with various demand prediction patterns are calculated in order to analyze the effect of demand prediction error. As a result, it is concluded that prediction error of energy demand causes 54.3 MJ/day increase of daily primary energy in the worst case, and annual primary energy consumption can be reduced by 13.2% with the best prediction in comparison with the worst one. Furthermore, the impact of energy demand prediction accuracy on daily primary energy has relationship with the amount of hot water demand. Therefore, the effectiveness of using the amount of hot water demand as a parameter for demand prediction is suggested in terms of energy saving.

Energy saving evaluation of PEFC systems with solar cell and battery

The main objective of this study is to evaluate energy saving potentials of polymer electrolyte fuel cell cogeneration systems integrated with solar cell and battery installed into residential houses. There exist many alternative operational policies in the above systems, and the mathematical planning approach is taken to derive the rational system's operational solution based on the mixed-integer linear planning method. In the numerical analysis of this study, energy saving characteristics of 12 alternative systems are compared respectively, and as one of main obtained results, it become clear that the energy saving effects to install battery into the systems depend largely on the operational policy of the system together with the evaluation criterion of adverse electricity from the solar cell to the electric grid. In other words, in the case of giving high priority to the self-consumption of electricity from the solar cell within the house, the energy saving potential to install battery increases largely, but few effects are noticed in other cases.

Energy-saving effect of a residential polymer electrolyte fuel cell cogeneration system combined with a plug-in hybrid electric vehicle

The energy-saving effect of a residential polymer electrolyte fuel cell cogeneration system (PEFC-CGS) that adopts a daily start–stop operation with no reverse power flow, combined with a plug-in hybrid electric vehicle (PHEV) is analyzed by optimal operational planning model based on mixed-integer linear programming. This combined use aims to increase the electric capacity factor of the PEFC-CGS by charging the PHEV using the PEFC-CGS 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. First, the optimal operational planning model that incorporates the daily start–stop operation of the PEFC-CGS is developed. The energy-saving effect of the combined use of the PEFC-CGS and PHEV is then analyzed on the basis of observations of the optimal operation patterns for a 0.75-kWe PEFC-CGS, a simulated energy demand with a sampling time of 5min, and various daily running distances of the PHEV. The results show that the combined use of the PEFC-CGS and PHEV increases the electric capacity factor and hot water supply rate of the PEFC-CGS and saves more energy in comparison with their separate use in which the PEFC-CGS is used but the PHEV is charged only using purchased electric power. Consequently, this feasibility study reveals that the combined use of the PEFC-CGS and PHEV provides the synergistic effect on energy savings in the residential and transport sectors.

リチウムイオン蓄電池を搭載した家庭用PEFCコージェネレーションシステム導入による一次エネルギー量とCO<sub>2</sub>排出量削減効果の評価

This paper presents the effects of introduction of residential polymer electrolyte fuel cell (PEFC) co-generation system with batteries in comparison with conventional systems that consist of a gas boiler and electric power from commercial grid, by computer simulation. The PEFC co-generation system in commercial use provides the average primary energy saving rate of 12.7% and CO2 reduction rate of 15.4% with respect to the conventional system. Addition of 8.0-kWh batteries to the PEFC system results in limited improvements of 0.8 points and 0.9 points in the reduction rates, respectively, yielding 13.5% and 16.3%, when using a conventional operation planning method. A new operation planning method is proposed in order to make a precise control of charging and discharging the batteries. The average primary energy saving rate reaches up to 16.9% by the improvement of 4.2 points, and CO2 reduction rate reaches up to 20.4% by the improvement of 5.0 points in the PEFC co-generation system with 8.0-kWh batteries using the new operation planning method. The new method can thus realize a substantial improvement in reduction rates. Furthermore, it is shown that the suitable battery module capacity for the residential PEFC co-generation system is 4.0kWh.

B104 戸建住宅における電力・給湯需要に対する各種エネルギー供給システムの比較分析(OS3 省エネルギー・コジェネ技術),動力エネルギーシステム部門20周年,次の20年への新展開)

Comparative evaluation has been studied on energy systems to supply hot water for detached houses, which are CO_2 heat pump, small scale gas engine and polymer electrolyte fuel cell cogeneration systems together with gas fired hot water boiler with latest heat recovery. For energy demand data measured at 15 houses through one year, energy saving and CO_2 emission characteristics of systems are evaluated comparatively by applying mathematical optimization method. As the numerical result, it is concluded that CO_2 heat pump system has advantage of saving energy and of reducing CO_2 emission compared with other systems.

An Evaluation Study of the Reduction Effects of the CO2 Emission Quantity and the Primary Energy in the Residential PEFC Co-generation System

This paper deals with the introduction effects on the basis of the comparative study of residential PEFC (polymer electrolyte fuel cell) co-generation systems and conventional systems that consist of a conventional gas boiler or a condensing gas boiler or a CO2 heat pump and the thermal power plant, by using the computer simulation. The target systems for estimation conform to real systems in the market and the energy demand data acquired from the past field tests was applied. As a result, it becomes clear that the residential PEFC co-generation systems have high performance in the energy saving and the CO2 reduction, from a comparison study with conventional systems and CO2 heat pump system. Concretely to say, the average energy saving rate that the residential PEFC co-generation system provides is 13.9% and the average CO2 reduction rate is 16.5% using quantity of reduction of CO2 as estimate function. Otherwise, the average energy saving rate that the CO2 heat pump system provides is 13.7% and the average CO2 reduction rate is 10.0%. Furthermore, we have proved the effectiveness a radiator in the residential PEFC co-generation 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.

A study on energy saving in residential PEFC cogeneration systems

We have been developing technologies for energy saving in the residential sector. Recently, we have been concentrating our resources specifically into the development of polymer electrolyte fuel cell (PEFC) cogeneration systems. The system has excellent energy saving characteristics. However, the total amount of energy saved depends on how the system is operated. The characteristics of residential energy consumption are more complicated than in industrial use and depend on individual living patterns. It is therefore not easy to develop a control method for a system that can be generally applied across a wide variety of residential use. In this paper, we propose a system configuration and operation planning method developed for a residential PEFC cogeneration system. Using an operation planning method we developed, we demonstrate that our system provides higher energy savings than the conventional method. The energy saving rates are 15.9% under a large heat demand, 18.4% under a relatively high electrical demand and low heat demand, 1.3% under relative low electrical and heat demands.

園芸施設におけるバイオマスガス化＋燃料電池CGSのシステム分析

The necessity of the low carbon society has been more significant since Toya Lake summit was held in Hokkaido, Japan. Under the circumstances, the biomass energy system and/or fuel cell system are promising systems for CO2 emission mitigation. In order to promote PEFC-CGS (Polymer Electrolyte Fuel Cell Co-generation), on the promotion of PEFC-CGS, we have to solve the discrepancy between the supply and the demand. In this paper, the operating cost, the equivalent CO2 emissions including N2O emissions and CO2 abatement cost for the greenhouse facility of strawberries in which PEFC-CGS was installed were analyzed. Through the Blue Tower process, which is one of gasification processes, the high concentration hydrogen gas (Bio-H2) is synthesized. The PEFC-CGS operation using Bio-H2 fuel, that is, the PEFC-CGS combined with BT gasifier would be extremely significant for the realization of low carbon emission society. In our analyses, the green house scale was assumed to be 1 to 5 ha. As a result, the power efficiency and the heat recovery efficiency were 24.0 LHV-% and 22.1 LHV-%, respectively. Also, the annual CO2 emissions in the case of 1ha green house were 2,350t-CO2/yr, and the abatement cost range was between 7,675 and 33,393 JPY/t-CO2.

集合住宅用固体高分子形燃料電池コージェネレーションシステムの運転方法

集合住宅用固体高分子形燃料電池コージェネレーションシステムの運転方法

家庭用固体高分子形燃料電池CGSの運転方法と導入効果 : 家庭用分散型電熱源の導入効果に関する研究 その1

This paper presents the effective operation methods and the regional energy conservation effects of housing Polymer Electrolyte Fuel Cell Co-Generation System (PEFC-CGS). We built the model-based simulation program to calculate the energy budget in a case that PEFC-CGS was introduced to detached houses considering specifications of a real PEFC-CGS. As a result of model-based simulations, we found that DSS (Daily Start and Stop) operation was the most effective method. Energy conservation effect is higher in cold areas because it varies by quantity of hot water supply load. The primary energy consumptions are reduced by 4-13% and CO_2 emissions are reduced by 7-20% in Japan. These values are increased by 1-2% in a case of the reverse power flow. Utility costs are also reduced by PEFC-CGS, but they vary by payment setting in each area.

04/02355 A quantitative approach for evaluation of negative impact of overmanning on electrical and mechanical projects: Gunduz, M. Building and Environment, 2004, 39, (5), 581–587

The performance of the novel Ru catalyst in a single-stage CO preferential oxidation removal reactor was investigated for residential polymer electrolyte fuel cell (PEFC) cogeneration systems. The outlet CO concentration of the CO removal reactor was reduced to less than 1 ppm even at [O2]/[CO]=1.5. The natural gas fuel processor equipped with the CO removal reactor achieved the target thermal efficiency of 77% (LHV). Moreover, the durability of the Ru catalyst has been confirmed for more than 16,000 h at a micro-reactor and for more than 8000 h at an actual CO removal reactor. Because of the low O2/CO molar ratio, the high CO removal conversion and the long-term durability, the Ru catalyst contributes to the development of residential PEFC cogeneration systems.

Cost Benefit Analysis for Polymer Electrolyte Fuel Cell Cogeneration

ABSTRACT Polymer electrolyte fuel cell (PEFC) cogeneration, which supplies whole space/water heating demand and 70% of electricity demand in a household in Japan, is considered to be a very attractive product for natural gas facilities to sell, because it is expected to double the natural gas sales to a household while letting the homeowner save electricity costs. On the other hand, the initial cost of fuel cell cogeneration equipment and installation is considered to be the main obstacles to its popularization. In this article, life cycle costs of both a conventional water heater and PEFC cogeneration was estimated, and it is concluded that a PEFC cogeneration system benefits homeowners, with a payback period of less than 4 years and system life cycle savings between $1000 and $1500 compared to a conventional water heating system.

Cost Benefit Analysis for Polymer Electrolyte Fuel Cell Cogeneration

Polymer electrolyte fuel cell (PEFC) cogeneration, which supplieswhole space/water heating demand and 70% of electricity demand in ahousehold in Japan, is considered to be a very attractive product fornatural gas facilities to sell, because it is expected to double the naturalgas sales to a household while letting the homeowner save electricitycosts. On the other hand, the initial cost of fuel cell cogeneration equip-ment and installation is considered to be the main obstacles to its popu-larization. In this article, life cycle costs of both a conventional waterheater and PEFC cogeneration was estimated, and it is concluded that aPEFC cogeneration system benefits homeowners, with a payback periodof less than 4 years and system life cycle savings between $1000 and$1500 compared to a conventional water heating system.

Development of residential PEFC cogeneration systems: Ru catalyst for CO preferential oxidation in reformed gas

The performance of the novel Ru catalyst in a single-stage CO preferential oxidation removal reactor was investigated for residential polymer electrolyte fuel cell (PEFC) cogeneration systems. The outlet CO concentration of the CO removal reactor was reduced to less than 1 ppm even at [O 2]/[CO]=1.5. The natural gas fuel processor equipped with the CO removal reactor achieved the target thermal efficiency of 77% (LHV). Moreover, the durability of the Ru catalyst has been confirmed for more than 16,000 h at a micro-reactor and for more than 8000 h at an actual CO removal reactor. Because of the low O 2/CO molar ratio, the high CO removal conversion and the long-term durability, the Ru catalyst contributes to the development of residential PEFC cogeneration systems.