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.

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.

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.

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.

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.

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%.

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.

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.

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

Electron Beam Desulfurization Project of Chengdu Cogeneration Power Plant Started Construction - A new cooperation in environment protection between China and Japan

On March 25 1996, the electron beam flue gas desulfurization demonstration project of Chengdu Cogeneration Power Plant started formal construction This is at present the largest electron beam desulfurization project in power plants in the world, and is jointly constructed by Sichuan Electric Power Bureau and the EBARA Works of Japan, This is an important cooperation project in environment protection between

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.