Performance of Gas-Steam Combined Cycle Cogeneration Units Influenced by Heating Network Terminal Steam Parameters

The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems.This paper investigated the coupling performance of a cogeneration heating and power system multidimensionally based on the operating characteristics of the cogeneration units,the hydraulic and thermodynamic characteristics of the heating network,and the energy loads.Taking a steam network supported by a gas-steam combined cycle cogeneration system as the research case,the interaction effect among the source-side prime movers,the heating networks,and the terminal demand thermal parameters were investigated based on the designed values,the plant testing data,and the validated simulation.The operating maps of the gas-steam combined cycle cogeneration units were obtained using THERMOFLEX,and the minimum source-side steam parameters of the steam network were solved using an inverse solution procedure based on the hydro-thermodynamic coupling model.The cogeneration operating maps indicate that the available operating domain considerably narrows with the rise of the extraction steam pressure and flow rate.The heating network inverse solution demonstrates that the source-side steam pressure and temperature can be optimized from the originally designed 1.11 MPa and 238.8°C to 1.074 MPa and 191.15°C,respectively.Under the operating strategy with the minimum source-side heating parameters,the power peak regulation depth remarkably increases to 18.30%whereas the comprehensive thermal efficiency decreases.The operation under the minimum source-side heating steam parameters can be superior to the originally designed one in the economy at a higher price of the heating steam.At a fuel price of$0.38/kg and the power to fuel price of 0.18 kg/(kW·h),the critical price ratio of heating steam to fuel is 119.1 kg/t.The influence of the power-fuel price ratio on the economic deviation appears relatively weak.

Low molecular weight alkane-fed solid oxide fuel cells for power and chemicals cogeneration

This paper presents a review of low molecular weight alkane-fed solid oxide fuel cells(SOFCs),which,unlikely the conventional use of SOFCs for only power production,are utilized to cogenerate produce useful chemicals at the same time.The cogeneration processes in SOFC have been classified according to the different types of fuel.C_(2)and C_(3)alkenes and synthesis gas are the main cogenerated chemicals together with electricity.The chemicals and energy cogeneration in a fuel cell reactor seems to be an effective alternative to conventional reactors for only chemicals production and conventional fuel cells for only power production.Although,the use of SOFCs for chemicals and energy cogeneration has proved successful in the industrial setting,the development of new catalysts aimed at obtaining the desired chemicals together with the production of a high amount of energy,and optimizing SOFC operation conditions is still a challenge to enhance system performance and make commercial applications workable.

Evaluation of Process and Economic Feasibility of Implementing a Topping Cycle Cogeneration

Industrial applications that require steam for their end-use generally utilize steam boilers that are typically oversized,citing operations flexibility.Similarly,gas turbine-based power plants corroborate a gas turbine system that may eventually relieve the usable exhaust into the atmosphere.This study explores the economic and technical feasibility of a topping cycle combined heat and power(CHP)system.It does so by leveraging a partially loaded boiler or gas turbine by increasing its unused load to generate steam and heat for subsequent usage.To this end,a decision support tool(COGENTEC)was developed,which emulates a given facility’s boiler or gas-turbine system,and its operational parameters with the application of steam turbines.The tool provides necessary insights into the most appropriate parameters that enable a CHP system to be technically and economically advantageous.Based on input variables such as boiler-rated capacity,steam pressure,steam temperature,and existing boiler load,among others,COGENTEC designs a topping cycle CHP system to inform a user whether this system is feasible in their facility or not.If applicable,the tool assists the user to realize the point of break-even(fuel cost incurred and cost savings)at the desired steam flow rate.It also conducts sensitivity analyses between energy usage,cost savings,and payback on the investment of the operating parameters to understand the relationship between relevant variables.By utilizing parameters from a pulp and paper manufacturing facility,the research determines that the fuel cost,electricity cost,and steam flow rate are the most important parameters for the feasibility of the system with a desirable payback on the investment.

Research on a simulated 60 kW PEMFC cogeneration system for domestic application

The electrical and thermal performances of a simulated 60 kW Proton Exchange Membrane Fuel Cell (PEMFC) cogeneration system are first analyzed and then strategies to make the system operation stable and efficient are developed. The system configuration is described first, and then the power response and coordination strategy are presented on the basis of the electricity model. Two different thermal models are used to estimate the thermal performance of this cogeneration system, and heat management is discussed. Based on these system designs, the 60 kW PEMFC cogeneration system is analyzed in detail. The analysis results will be useful for further study and development of the system.

Biomass Cogeneration Technologies: A Review

Currently, fossil fuels such as oil, coal and natural gas represent the prime energy sources in the world. However, it is anticipated that these sources of energy will deplete within the next 40 - 50 years. Moreover, the expected environmental damages such as the global warming, acid rain and urban smog due to the production of emissions from these sources have tempted the world to try to reduce carbon emissions by 80% and shift towards utilizing a variety of renewable energy resources (RES) which are less environmentally harmful such as solar, wind, biomass, etc. in a sustainable way. Biomass is one of the earliest sources of energy with very specific properties. In this review, we present the different cogeneration systems to provide electrical power and heating for isolated communities. It has been found that the steam turbine process is the most relevant for biomass cogeneration plants for its high efficiency and technological maturity. The future of CHP plants depends upon the development of the markets for fossil fuels and on policy decisions regarding the biomass market.

Model and Design of Cogeneration System for Different Demands of Desalination Water, Heat and Power Production

In order to improve the energy efficiency, reduce the CO2 emission and decrease the cost, a cogenera- tion system for desalination water, heat and power production was studied in this paper. The superstructure of the cogeneration system consisted of a coal-based thermal power plant （TPP）, a multi-stage flash desalination （MSF） module and reverse osmosis desalination （RO） module. For different demands of water, heat and power production, the corresponding optimal production structure was different. After reasonable simplification, the process model ot each unit was built. The economical model, including the unit investment, and operation and maintenance cost, was presented. By solving this non-linear programming （NLP） model, whose objective is to minimize the annual cost, an optimal cogeneration system can be obtained. Compared to separate production systems, the optimal system can reduce 16.1%-21.7% of the total annual cost. showing this design method was effective.

A Cogeneration System for an Apartment Building Based on Distributed Heat Storage Technology

In order for economically viable distributed generation systems for apartment buildings to spread, it is essential to develop an efficient and low-cost heat supply system. We have developed a new eogeneration system called the Neighboring Cogeneration system （NCG）. The key concept of this system is to install a heat accumulator with a hot water supply and a room heating function at each household and to connect different households by a single loop of hot water pipe. As a result, time leveling of the heat supply and heat transferring among households becomes possible. Thus, the costs of the pipe and the heat source equipment decrease. Furthermore, because all of the heat accumulators store heat, the total heat storage capacity is large enough for cogeneration to generate exhaust heat according to the electricity demand and with a high operating rate. In this paper, we report the results of the NCG system for 7 lived-in households. The controlling system worked efficiently. All of the households were able to use hot water without any difficulties. Further, we report the results of the energy saving effect of the NCG system for 50 lived-in households by means of a simulation based on the experimental results for NEXT21.

Integration of a Gas Fired Steam Power Plant with a Total Site Utility Using a New Cogeneration Targeting Procedure

A steam power plant can work as a dual purpose plant for simultaneous production of steam and elec-trical power. In this paper we seek the optimum integration of a steam power plant as a source and a site utility sys-tem as a sink of steam and power. Estimation for the cogeneration potential prior to the design of a central utility system for site utility systems is vital to the targets for site fuel demand as well as heat and power production. In this regard, a new cogeneration targeting procedure is proposed for integration of a steam power plant and a site utility consisting of a process plant. The new methodology seeks the optimal integration based on a new cogenera-tion targeting scheme. In addition, a modified site utility grand composite curve(SUGCC) diagram is proposed and compared to the original SUGCC. A gas fired steam power plant and a process site utility is considered in a case study. The applicability of the developed procedure is tested against other design methods(STAR? and Thermoflex software) through a case study. The proposed method gives comparable results, and the targeting method is used for optimal integration of steam levels. Identifying optimal conditions of steam levels for integration is important in the design of utility systems, as the selection of steam levels in a steam power plant and site utility for integration greatly influences the potential for cogeneration and energy recovery. The integration of steam levels of the steam power plant and the site utility system in the case study demonstrates the usefulness of the method for reducing the overall energy consumption for the site.

Maximum useful energy rate and efficiency of a recuperative Brayton cogeneration plant

A thermodynamic model was developed to analyze the performance of cogeneration plant based on irreversible recuperative Brayton cycle. A parameter, dimensionless total useful energy rate (DTUER), was used as the criterion for performance optimization of cogeneration plant. The effects of cycle parameters, internal irreversibilities, and recuperator efficiency on maximum DTUER and on the efficiency at maximum DTUER were numerically investigated. The relation between DTUER and cogeneration efficiency was also analyzed. The results show that there exists an optimal compressor pressure ratio which maximizes the DTUER. It is also found that there exists an optimal power-to-heat ratio which results in a dual-maximum DTUER.

Energy-Saving and Economical Evaluations of a Ceramic Gas Turbine Cogeneration Plant

A ceramic gas turbine can save energy because of its high thermal efficiency at high turbine inlet temperatures. This paper deals with the thermodynamic and economic aspects of a ceramic gas turbine cogeneration system. Here cogeneration means the simultaneous production of electrical en-ergy and useful thermal energy from the same facility. The thermodynamic performance of a ceramic gas turbine cycle is assessed using a computer model. This model is used in parametric studies of performance under partial loads and at various inlet air temperatures. The computed performance is compared to the measured performance of a conventional gas turbine cycle. Then, an economic evaluation of a ceramic gas turbine cogeneration system is investigated. Energy savings provided by this system are estimated on the basis of the distributions of heat/power ratios. The computed economic evaluation is compared to the actual economic performance of a conventional system in which boilers produce the required thermal energy and electricity is purchased from a utility.

Case Studies of Energy Saving and CO₂Reduction by Cogeneration and Heat Pump Systems

This paper describes two case studies: 1) a cogeneration system of a hospital and 2) a heat pump system installed in an aquarium that uses seawater for latent heat storage. The cogeneration system is an autonomous system that combines the generation of electrical, heating, and cooling energies in a hospital. Cogeneration systems can provide simultaneous heating and cooling. No technical obstacles were identified for implementing the cogeneration system. The average ratio between electric and thermal loads in the hospital was suitable for the cogeneration system operation. An analysis performed for a non-optimized cogeneration system predicted large potential for energy savings and CO2 reduction. The heat pump system using a low-temperature unutilized heat source is introduced on a heat source load responsive heat pump system, which combines a load variation responsive heat pump utilizing seawater with a latent heat-storage system (ice and water slurry), using nighttime electric power to level the electric power load. The experimental coefficient of performance (COP) of the proposed heat exchanger from the heat pump system, assisted by using seawater as latent heat storage for cooling, is discussed in detail.

Potential Impact of Biomass Cogeneration Plants on Achieving Climate Neutrality of BIH until 2050

The paper analyzes the potential of Biomass Combined Heat and Power (BCHP) plants in Bosnia and Herzegovina (BiH) in achieving climate neutrality until 2050. Two scenarios for reducing GHG emissions from the power generation sector in BiH until 2050 were developed. Scenarios were developed using LEAP, a software tool for energy policy analysis and climate change mitigation assessment. The complete final energy consumption and existing primary energy mix in BiH were included. Both scenarios imply a significant reduction in electricity generation from coal-fired power plants (CFPP). The first scenario (S1) involves the construction of a substitute CFPP unlike the second scenario in which there is no construction of a new CFPP, but part of the reduction in electricity generation from the CFPPs is compensated by BCHPs. The second scenario (S2) achieves a significantly higher reduction in GHGs emissions and provides an answer to the question of how much wood biomass is needed for the operation of BCHP for enabling the decarbonization of the power generation sector by 2050. S1 also represents a step toward reducing GHG emissions. Emissions from power generation in 2030 are about 60% lower than in 2015, i.e. by closing part of the existing CFPPs fleet, while in 2050 GHG emissions will be reduced by 12.26 million tons of CO2eq compared to 2015. The main advantage of S2 is the gradual phase-out of CFPPs and construction of BCHPs, which means incomparably lower GHG emissions, negligible in 2050, representing a key argument for the deployment of biomass potential for power generation. The technical potential of unused wood biomass in BiH is 7.44 PJ annually or 620,620 t annually. These quantities would be sufficient for the levels of electricity production in Scenario 2 by 2035. After that, the existing available technical potential is not enough. This means that BiH needs to increase biomass production and its technical potential to enable the implementation of that scenario.

New type steam turbine for cogeneration

A concept of energy saving & efficiency improving from cold source for cogeneration steam turbine was discussed herein. A new type "NCB" cogeneration steam turbine was proposed,which could considerably increase heat supply capacity,thermal efficiency and electric power. Taking 300 MW cogeneration steam turbine as an example,the results show that heat supply capacity reaches the maximum,i.e. increases by 30 %,thermal efficiency is improved by 12 %,and electric power is enhanced by 15 MW during peak heat load.

Feasibility Study of Optimal Sizing of Micro-Cogeneration System for Convenience Stores in Bangkok

In this paper, the optimization of micro-cogeneration (μ-CHP) system sizing for convenience stores in Thailand is conducted under the present condition of fuel prices and tariff rates. The assessment of (μ-CHP) system performance is analyzed by using Primary Energy Saving (PES) Ratio for evaluating the energy performance. Also, the Annual Cost Saving Ratio (CSR) and Payback Period (PBP) are used for evaluating the economic performance of μ-CHP system. The analysis results show the optimal size of μ-CHP system under possible conditions including the operating schedule and system’s efficiency were conducted.

Current Situation and Development of Cogeneration in China

1. The Power Industry and Cogeneration in China 1.1 The Power Industry in China The power industry has developed rapidly in China in recent decades. In 1994, total electricity generation was 927.8 TWh and the total installed capacity was 199.80 GW. It is broken down as follows: hydropower 49.0 GW. 24.5 %; thermal power 148.73 GW, 74.4c/c: and nuclear power 2.1 GW, 0.7%.

A Decision Method of Cogeneration Operation Schedule by Combining Use of SOFCs and PEFCs

In this paper, the authors propose a cogeneration system by combining two kinds of FCs （fuel cells） for a collective housing. The good points which each FC has are applied to the cogeneration operation schedule. In this study, some rooms interchange electric power and heat with each other for high efficiency and reduction of energy loss. The authors determine an operation schedule of FCs by multi-evaluation from viewpoints of energy cost and CO2 emissions.

Cogeneration Potential in the Industrial Sector and Gas Emission Reduction: A Case Study

The aim of the current paper is to discuss the replacement of diesel oil (DO) consumption by natural gas (NG) in a cogeneration system. A specific industrial consumption case study was chosen to be the method used to accomplish a robust analysis. The results have shown the advantages in reducing CO2, CH4, N2O and particulate matter emissions, as well as the need to keep the NOx emission rates. After proceeding with theoretical studies concerning our case, we concluded that the diesel oil replacement by natural gas is beneficial for gas emission reduction. Public policies should consider local development based on the use of different fuels, such natural gas, to achieve the integration between decentralized energy generation and energy-efficient initiatives.

Methodology for Defining of Eligible Capacity for Wood Fuel Based Cogeneration Plants in Small Towns in Estonia

There is a high potential for small-scale and medium scale wood-fired cogeneration in Estonia. The purpose of this research is to define the eligible capacity for wood fuel based cogeneration plant operating on the base of district heating systems in small towns. Results were checked and approbated by economical and environmental factors. Two optimal sizing methods were used maximizing of amount of heat year-round while working at full installed capacity and maximizing of amount of heat year-round while working with partial loads. Results of defining optimal capacities for wood-fired cogeneration plants in small Estonian towns showed that method of maximizing of amount of heat year-round while working with partial loads is more adequate to real situation.

First phase project of Huaneng Yingkou Cogeneration Plant completed

On December 2, 2009, Unit 1 of Huaneng Yingkou Cogeneration Plant smoothly passed 168-hour triaoperation. 11 days later, Unit 2 also successfully passed the trial operation. The project