Economic analysis of a combined heat and power molten carbonate fuel cell system

Fuel cells can be attractive for use as stationary combined heat and power (CHP) systems. Molten carbonate fuel cell (MCFC) power plants are prime candidates for the utilization of fossil based fuels to generate high efficiency ultra clean power. However, fuel cells are considerably more expensive than comparable conventional technologies and therefore a careful analysis of the economics must be taken. This work presents analysis on the feasibility of installing both a FuelCell Energy DFC^® 1500MA and 300MA system for use at Adams Thermal Systems, a manufacturing facility in the U.S. Midwest. The paper examined thoroughly the economics driving the appropriateness of this measure. In addition, a parametric study was conducted to determine scenarios including variation in electric and natural gas rates along with reduced installation costs.     

Dynamic modeling and evaluation of solid oxide fuel cell - combined heat and power system operating strategies

Operating strategies of solid oxide fuel cell (SOFC) combined heat and power (CHP) systems are developed and evaluated from a utility, and end-user perspective using a fully integrated SOFC-CHP system dynamic model that resolves the physical states, thermal integration and overall efficiency of the system. The model can be modified for any SOFC-CHP system, but the present analysis is applied to a hotel in southern California based on measured electric and heating loads. Analysis indicates that combined heat and power systems can be operated to benefit both the end-users and the utility, providing more efficient electric generation as well as grid ancillary services, namely dispatchable urban power.Design and operating strategies considered in the paper include optimal sizing of the fuel cell, thermal energy storage to dispatch heat, and operating the fuel cell to provide flexible grid power. Analysis results indicate that with a 13.1% average increase in price-of-electricity (POE), the system can provide the grid with a 50% operating range of dispatchable urban power at an overall thermal efficiency of 80%. This grid-support operating mode increases the operational flexibility of the SOFC-CHP system, which may make the technology an important utility asset for accommodating the increased penetration of intermittent renewable power.     

The anode supported internal cathode tubular solid oxide fuel cell: Novel production of a cell geometry for combined heat and power applications

An effective strategy for generating combined heat and power (CHP) systems is to use the combustion of hydrocarbons to provide fuel reforming and heat production for solid oxide fuel cell (SOFC) operation. Though tubular SOFCs (tSOFCs) are well suited to the thermal cycling associated with combustion systems, they have a geometric limitation which requires significant alteration to the combustion chamber. These alterations can be eliminated by producing an anode supported internal cathode-tSOFC (IC-tSOFC) which can be directly integrated into the chamber with minimal alterations. Novel methods used to produce IC-tSOFCs are discussed in this work. Scanning electron microscopy (SEM) and performance characterization are used to analyze fabricated cells. With a peak power density of 369 mW∙cm⁻², and an open circuit voltage (OCV) of 0.98 V, it is confirmed that novel production methods for IC-tSOFCs have been successful.     

Estimating the power and number of microturbines in small-scale combined heat and power systems

Utilizing the combined heat and power (CHP) systems to produce both electricity and heat is growing rapidly due to their high efficiency and low emissions in domestic, commercial, and industrial applications. In the first two categories among available drivers, due to the compact size and low weight, microturbines are attractive choice. In this paper, by using an energy–economic analysis the type and number of the required microturbines for the specific electricity and heat load curves during a year were selected. For performing this task an objective function annual profit (AP) was introduced and maximized. The operation strategy and the payback period of the chosen system was also determined in this study.     

垃圾焚烧电厂热电联产的经济性分析

合理利用垃圾资源进行热电联产,是节能减排、改善环境的有力措施。以某2×750 t·d^-1垃圾焚烧电厂为例,通过模型研究发现热电联产可以减少垃圾焚烧电厂的冷源损失,提高全厂热效率;利用一抽蒸汽进行热电联产可实现蒸汽品质的梯级利用,获得较高的经济效益;供热量为30 t·h^-1,垃圾热值由4185.9 kJ·kg^-1增加至8371.7 kJ·kg^-1时,发电量越多,供热能力越强,年热电联产经济效益由7822.76万元增加到14641.07万元;垃圾热值为8371.7 kJ·kg^-1,供热量从10 t·h^-1增加到60 t·h^-1时,垃圾焚烧电厂热效率从28.96%增加到48.50%,年经济效益从13602.74万元增加到15455.66万元。当该地区垃圾热值较高并具备供热条件时,实现垃圾热电联产具有较高的收益。     

Impact of heat,power and hydrogen generation on optimal placement and operation of fuel cell power plants

In this paper, a stochastic model is proposed for planning the location and operation of Fuel Cell Power Plants (FCPPs) as Combined Heat, power, and Hydrogen (CHPH) units. Total cost, emissions of FCPPs and substation, and voltage deviation are the objective functions to be minimized. Location and operation of FCPPs as CHPH are considered in this paper while their investment cost is not taken into account. In the proposed model, indeterminacy refers to electrical and thermal loads forecasting, pressure of oxygen and hydrogen, and the nominal temperature of FCPPs. In this method, scenarios are produced using roulette wheel mechanism and probability distribution function of input random variables. Using this method, the probabilistic problem is considered to be distributed as some scenarios and consequently probabilistic problem is considered as combination of some deterministic problems. Considering the nature of objective functions, the problem of locating and operating FCPPs as CHPH is considered as a mixed integer nonlinear problem. A Self Adaptive Charged System Search (SACSS) algorithm is employed for determining the best Pareto optimal set. Furthermore, a set of non-dominated solutions is saved in repository during simulation procedure. A 69-bus distributed system is used for verifying the beneficiary proposed method.     

Design of a combined heat,hydrogen, and power plant from university campus waste streams

This paper presents analysis of a combined heat, hydrogen, and power (CHHP) plant for waste-to-energy conversion in response to the 2012 Hydrogen Student Design Contest. Our team designed the CHHP plant centered on a molten carbonate fuel cell (Fuel Cell Energy DFC-1500) fueled by syngas derived primarily from an oxygen-fed municipal waste gasifier. Catalytic methanation and supplemental utility natural gas increase the fuel methane content to meet the DFC-1500 fueling requirements for maintaining stack thermal energy balance. Internal reforming converts excess fuel from the fuel cell to an H₂-rich stream, which is purified downstream in a pressure-swing adsorption system. The separated H₂ (1000 kg per day) is compressed for storage to provide fuel for a campus fleet of PEM fuel cell buses. The system provides more than 1.1 MWe for the campus grid with approximately 20% of the fuel cell power used for H₂ compression and running the plant. Heat recovery steam generators provide steam for the methanation reactor and 0.4 MW of thermal energy for district heating or steam turbine-driven chillers. Cost analysis indicates that the system requires incentives for economic viability with current estimated operating costs, but advances to reduce capital expenses of comparable urban waste-driven CHHP systems can make them attractive for future implementation.     

Life cycle assessment of domestic fuel cell micro combined heat and power generation: Exploring influential factors

Residential Fuel Cell micro combined heat and power (FC-μCHP) systems can help decarburizing the energy system. In the European ene.field project, the environmental performance of FC-μCHP under different conditions was therefore evaluated by means of a comprehensive Life Cycle Assessment (LCA). Important influential factors were explored, i.e. heating demands, full load hours (FLHs) and electricity replacement mixes (ERMs). The systems were compared with a stand-alone Gas Condensing Boiler (GCB) and a heat pump (HP, only in single family homes, SFHs). For the initially assumed FLHs and the current ENTSO-E ERM, relevant environmental impacts including climate change are generally smaller for the FC-μCHPs than for the HP and the stand-alone GCB. In the setting “existing SFHs in central climate” with the highest deployment potential, GHG emission savings are higher the more carbon-intensive the ERM is and/or higher the net electricity export into the grid is. The results are discussed and put into perspective. Further research demands as well as product development opportunities are outlined. The importance of a green hydrogen economy is emphasized.     

Integrating renewable sources of energy into an existing combined heat and power system

In recent years, renewable energy sources have played an increasingly important role in potential energy production. The integration of renewables into energy production plants has therefore become a major challenge for many organizations. This study concerns the modernization of a small power plant in a large hospital. The design criteria include the possibility of utilizing renewable energy sources and providing a potential increase in heat production (with additional heat being supplied to a nearby university campus). The existing boiler conditions (i.e. controls, efficiency, etc.) are unable to satisfy the desired requirements and therefore require an extensive retrofit.     

Experimental study of engine performance and emissions for hydrogen diesel dual fuel engine with exhaust gas recirculation

With an alarming enlargement in vehicular density, there is a threat to the environment due to toxic emissions and depleting fossil fuel reserves across the globe. This has led to the perpetual exploration of clean energy resources to establish sustainable transportation. Researchers are continuously looking for the fuels with clean emission without compromising much on vehicular performance characteristics which has already been set by efficient diesel engines. Hydrogen seems to be a promising alternative fuel for its clean combustion, recyclability and enhanced engine performance. However, problems like high NOx emissions is seen as an exclusive threat to hydrogen fuelled engines. Exhaust gas recirculation (EGR), on the other hand, is known to overcome the aforementioned problem. Therefore, this study is conducted to study the combined effect of hydrogen addition and EGR on the dual fuelled compression ignition engine on a single cylinder diesel engine modified to incorporate manifold hydrogen injection and controlled EGR. The experiments are conducted for 25%, 50%, 75% and 100% loads with the hydrogen energy share (HES) of 0%, 10% and 30%. The EGR rate is controlled between 0%, 5% and 10%. With no substantial decrement in engine's brake thermal efficiency, high gains in terms of emissions are observed due to synergy between hydrogen addition and EGR. The cumulative reduction of 38.4%, 27.4%, 33.4%, 32.3% and 20% with 30% HES and 10% EGR is observed for NOx, CO2, CO, THC and PM, respectively. Hence, the combination of hydrogen addition and EGR is observed to be advantageous for overall emission reduction.     

Transient characteristics investigation of the integrated ejector-driven hydrogen recirculation by multi-component CFD simulation

The hydrogen supply of the fuel cell system is realized by the cooperation of multiple components. Transient characteristics of a single component can affect the performance of other components. In this study, a three-dimensional multi-component computational fluid dynamics (CFD) model was developed to investigate the synergistic transient characteristics of the hydrogen recirculation components such as hydrogen injector, ejector, and purge valve in an 80 kW PEMFC. The results show that the entrainment performance of the ejector is reduced under unsteady purge conditions compared with steady conditions. The pressure fluctuation of the secondary flow is significant even under purge closed durations. There are drastic changes in velocity and pressure in the ejector, especially in the mixing chamber. Moreover, an abundant hydrogen supply capacity of the injector is necessary to deal with the excessive anode pressure fluctuation. The feedforward-feedback integrated control of the injector is a more efficient strategy to reduce pressure fluctuations compared with the feedback control.     

Techno-economic evaluation of medium scale power to hydrogen to combined heat and power generation systems

The European Hydrogen Strategy and the new « Fit for 55 » package indicate the urgent need for the alignment of policy with the European Green Deal and European Union (EU) climate law for the decarbonization of the energy system and the use of hydrogen towards 2030 and 2050. The increasing carbon prices in EU Emission Trading System (ETS) as well as the lack of dispatchable thermal power generation as part of the Coal exit are expected to enhance the role of Combined Heat and Power (CHP) in the future energy system. In the present work, the use of renewable hydrogen for the decarbonization of CHP plants is investigated for various fossil fuel substitution ratios and the impact of the overall efficiency, the reduction of direct emissions and the carbon footprint of heat and power generation are reported. The analysis provides insights on efficient and decarbonized cogeneration linking the power with the heat sector via renewable hydrogen production and use. The levelized cost of hydrogen production as well as the levelized cost of electricity in the power to hydrogen to combined heat and power system are analyzed for various natural gas substitution scenarios as well as current and future projections of EU ETS carbon prices.     

Economic and environmental assessment of phosphoric acid fuel cell-based combined heat and power system for an apartment complex

Economic and environmental potential of medium-scale combined heat and power (CHP) systems in the residential sector was assessed by introducing a 400 kW_el-scale phosphoric acid fuel cell (PAFC)-based CHP system into an apartment building in New York City. Simulation-based analyses were carried out under two different CHP operation strategies; electrical-load-following (ELF) and thermal-load-following (TLF). Technical and economic analyses indicated that ELF would be the appropriate operation mode for this CHP application. Economic analysis indicated that the CHP/ELF system operation could economically benefit users within 10 years under the present grid prices in New York City. However, because the CO₂ emission factor of the NY grid is very low (300 g/kWh), the CHP/ELF system operation would increase CO₂ emission. Achieving carbon neutrality in this application thus requires improvement in the utilization ratio of recovered heat.     

Integration of direct carbon and hydrogen fuel cells for highly efficient power generation from hydrocarbon fuels

In view of impending depletion of hydrocarbon fuel resources and their negative environmental impact, it is imperative to significantly increase the energy conversion efficiency of hydrocarbon-based power generation systems. The combination of a hydrocarbon decomposition reactor with a direct carbon and hydrogen fuel cells (FC) as a means for a significant increase in chemical-to-electrical energy conversion efficiency is discussed in this paper. The data on development and operation of a thermocatalytic hydrocarbon decomposition reactor and its coupling with a proton exchange membrane FC are presented. The analysis of the integrated power generating system including a hydrocarbon decomposition reactor, direct carbon and hydrogen FC using natural gas and propane as fuels is conducted. It was estimated that overall chemical-to-electrical energy conversion efficiency of the integrated system varied in the range of 49.4–82.5%, depending on the type of fuel and FC used, and CO₂ emission per kW_elh produced is less than half of that from conventional power generation sources.     

A parametric comparison of three fuel recirculation system in the closed loop fuel supply system of PEM fuel cell

Anodic fuel recirculation system has a significant role on the parasitic power of proton exchange membrane fuel cell (PEMFC). In this paper, different fuel supply systems for a PEMFC including a mechanical compressor, an ejector and an electrochemical pump are evaluated. Furthermore, the performances of ejector and electrochemical pump are studied at different operating conditions including operating temperature of 333 K–353 K, operating pressure of 2 bar–4 bar, relative humidity of 20%–100%, stack cells number from 150 to 400 and PEMFC active area of 0.03 m²–0.1 m². The results reveal that higher temperature of PEMFC leads to lower power consumption of the electrochemical pump, because activation over-potential of electrochemical pump decreases at higher temperatures. Moreover, higher operating temperature and pressure of PEMFC leads to higher stoichiometric ratio and hydrogen recirculation ratio because the motive flow energy in ejector enhances. In addition, the recirculation ratio and hydrogen stoichiometric ratio increase, almost linearly, with increase of anodic relative humidity. Utilization of mechanical compressor leads to lower system efficiency than other fuel recirculating devices due to more power consumption. Utilization of electrochemical pump in anodic recirculation system is a promising alternative to ejector due to lower noise level, better controllability and wide range of operating conditions.     

Parameter extraction of fuel cells using hybrid interior search algorithm

Precise modelling of fuel cells is very important for understanding their functioning. In this work, an application of hybrid interior search algorithm (HISA) is proposed to extract the parameters of fuel cells for their electromechanical equations based on nonlinear current‐voltage characteristics. Proposed hybridised algorithm has been developed using evolutionary mutation and crossover operators so as to enhance the modelling capability of interior search algorithm (ISA). To assess the modelling performance of HISA, parameter extraction of two types of fuel cell models, namely, proton exchange membrane fuel cell (PEMFC) and solid oxide fuel cell (SOFC) have been considered. Modelling performance of HISA, assessed using mean squared error between computed and experimental data, is found to be superior to ISA and several other recently reported prominent optimisation methods. Based on the presented intensive simulation investigations, it is concluded that HISA improves the performance of the basic ISA in terms of fitter solutions, robustness, and convergence rate and therefore offers a promising optimisation technique for parameter extraction of fuel cells.     

Energy and cost analysis of a solar-hydrogen combined heat and power system for remote power supply using a computer simulation

A simulation program, based on Visual Pascal, for sizing and techno-economic analysis of the performance of solar-hydrogen combined heat and power systems for remote applications is described. The accuracy of the submodels is checked by comparing the real performances of the system’s components obtained from experimental measurements with model outputs. The use of the heat generated by the PEM fuel cell, and any unused excess hydrogen, is investigated for hot water production or space heating while the solar-hydrogen system is supplying electricity. A 5 kWh daily demand profile and the solar radiation profile of Melbourne have been used in a case study to investigate the typical techno-economic characteristics of the system to supply a remote household. The simulation shows that by harnessing both thermal load and excess hydrogen it is possible to increase the average yearly energy efficiency of the fuel cell in the solar-hydrogen system from just below 40% up to about 80% in both heat and power generation (based on the high heating value of hydrogen). The fuel cell in the system is conventionally sized to meet the peak of the demand profile. However, an economic optimisation analysis illustrates that installing a larger fuel cell could lead to up to a 15% reduction in the unit cost of the electricity to an average of just below 90 c/kWh over the assessment period of 30 years. Further, for an economically optimal size of the fuel cell, nearly a half the yearly energy demand for hot water of the remote household could be supplied by heat recovery from the fuel cell and utilising unused hydrogen in the exit stream. Such a system could then complement a conventional solar water heating system by providing the boosting energy (usually in the order of 40% of the total) normally obtained from gas or electricity.     

Optimum generation capacities of micro combined heat and power systems in apartment complexes with varying numbers of apartment units

A dynamic simulation of micro combined heat and power (micro-CHP) systems that includes the transient behavior of the system was developed by modeling the generation of electricity and recovery of heat separately. Residential load profiles were calculated based on statistical reports from a Korean government agency, and were used as input data to select the optimum capacities of micro-CHP systems based on the number of apartment units being served, focusing on both economic and energetic criteria. The capacity of internal combustion engine (ICE) based micro-CHP was assumed to be in the range 1–500 kW, and the dependence of the efficiency of the generator unit on the capacity was included. It was found that the configuration (i.e., the capacity and number of generator units) that maximized the annual savings also had favorable energetic performance. Additionally, the statistical mode calculated from the annual electrical load distribution was verified as a suitable indicator when deciding the optimum capacity of a micro-CHP system.     

Electrolyzer-fuel cell combination for grid peak load management in a geothermal power plant: Power to hydrogen and hydrogen to power conversion

This study provides comprehensive energy, exergy, and economic evaluations and optimizations of a novel integrated fuel cell/geothermal-based energy system simultaneously generating cooling and electricity. The system is empowered by geothermal energy and the electricity is mainly produced by a dual organic cycle. A proton exchange membrane electrolyzer is employed to generate the oxygen and hydrogen consumed by a proton exchange membrane fuel cell utilized to support the network during consumption peak periods. This fuel cell can be also used for supplying the electricity demanded by the network to satisfy the loads at different times. All the simulations are conducted using Engineering Equation Solver software. To optimize the system, a multi-objective optimization method based on genetic algorithm is applied in MATLAB software. The objective functions are minimized cost rate and maximized exergy efficiency. The optimum values of exergy efficiency and cost rate are found to be 62.19% and 18.55$/h, respectively. Additionally, the results reveal that combining a fuel cell and an electrolyzer can be an effective solution when it comes to electricity consumption management during peak load and low load periods.     

Combined heat and power in the Swedish district heating sector—impact of green certificates and CO2 trading on new investments

Combined heat and power (CHP) has been identified by the EU administration as an important means of reducing CO₂-emissions and increasing the energy efficiency. In Sweden, only about one third of the demand for district heat (DH) is supplied from CHP. This share could be significantly larger if the profitability of CHP generation increased. The objective of this study was to analyse the extent to which the profitability for investments in new CHP plants in the Swedish DH sector have changed thanks to the recently implemented trading schemes for green certificates (TGCs) and CO₂ emissions (TEPs). The analysis was carried out using a simulation model of the Swedish DH sector in which the profitability of CHP investments for all DH systems, with and without the two trading schemes applied, is compared. In addition, a comparison was made of the changes in CHP generation, CO₂ emissions, and operation costs if investments are made in the CHP plant shown to be most profitable in each system according to the model. The study shows that the profitability of investments in CHP plants increased significantly with the introductions of TGC and TEP schemes. If all DH utilities also undertook their most profitable CHP investments, the results indicate a major increase in power generation which, in turn, would reduce the CO₂ emissions from the European power sector by up to 13 Mton/year, assuming that coal condensing power is displaced.