Energy conservation through industrial cogeneration

Combined generation of process steam and electric power in coal-fired industrial power plants is examined, and a rate of return on various investments of this type is estimated. The effect on these rates of return of a 20% investment tax credit is calculated, which appears to be slight. We note that positive incentives such as investment tax credits allow the firm to face lower energy prices and could result in more energy intensive operation at the level of the firm.     

Evaluating the role of cogeneration for carbon management in Alberta

Developing long-term carbon control strategies is important in energy intensive industries such as the oil sands operations in Alberta. We examine the use of cogeneration to satisfy the energy demands of oil sands operations in Alberta in the context of carbon management. This paper evaluates the role of cogeneration in meeting Provincial carbon management goals and discusses the arbitrary characteristics of facility- and product-based carbon emissions control regulations. We model an oil sands operation that operates with and without incorporated cogeneration. We compare CO₂ emissions and associated costs under different carbon emissions control regulations, including the present carbon emissions control regulation of Alberta. The results suggest that incorporating cogeneration into the growing oil sands industry could contribute in the near-term to reducing CO₂ emissions in Alberta. This analysis also shows that the different accounting methods and calculations of electricity offsets could lead to very different levels of incentives for cogeneration. Regulations that attempt to manage emissions on a product and facility basis may become arbitrary and complex as regulators attempt to approximate the effect of an economy-wide carbon price.     

Thermal-economic analysis of heat-matched industrial cogeneration systems

Recent federal incentives in the U.S. concerning tax credits, fuel-use exemptions, and facilitation of sale of electric power to local electric utilities have greatly stimulated interest in industrial cogeneration. In particular, the ability to sell excess or all cogenerated electric power (i.e. arbitrage) has widened the options available to a potential cogenerator. In the present paper we consider a comparison of alternate cogeneration plants with an existing steam-only plant in terms of energy conservation and engineering economics. The concept of marginal cost of production is applied throughout. The criterion of economic selection is acceptable incremental rate of return on incremental investment based on the challenger-defender test of successively greater capital costs. As an example, coal-fired topping steam turbines as well as natural-gas-fired gas turbines and oil-fired diesels with waste-heat boilers are considered to replace a gas-fired steam-only plant and provide a range of electric power for the same thermal load.     

Government policy and industrial investment in cogeneration in the USA

This paper presents an economic analysis of investment in cogeneration in selected industries and assesses the impact of investment tax credits policy directed at cogeneration. We use a dynamic partial equilibrium model that is derived under the assumption that investment in cogeneration occurs if and when the annualized cost of the incremental investment is less than the annualized benefits of avoiding electricity purchase from the utilities. Policy simulations show that investment in cogeneration is economically feasible even without the tax credits; the tax credit policy marginally increases investment in cogeneration. The welfare distortions and revenue loss to the US Treasury are also estimated. External benefits required per barrel of oil to offset distortion costs would come to $2.83.     

Optimal efficiency as a design criterion for closed loop combinedcycle industrial cogeneration

In comparison to conventional industrial cogeneration plants, the closed loop combined cycle cogeneration (CLCC) system has the advantage that it needs virtually no enhancement in steam handling capability of the existing plant, both in terms of steam pressure as well as volume flow rates. An optimal design procedure is introduced in this paper for the configuration of a CLCC system between existing steam headers of an industrial setup. While aiming primarily at maximization of generation efficiency for the CLCC configuration, the design approach simultaneously attempts to configure a suboptimal number of units for each item of cogeneration equipment. The suboptimal (integer) number of units is maintained within a specified suboptimal margin of the corresponding optimal (real) number of units that emerges from efficiency maximization. The design procedure relies heavily on a database including all available makes of cogeneration equipment. Consequently, the approach is very much market dependent, as illustrated adequately by a suitable case study     

Dynamic energy and exergy analyses of an industrial cogeneration system

The study deals with the energetic and exergetic analyses of a cogeneration (combined heat and power, CHP) system installed in a ceramic factory, located in Izmir, Turkey. This system has three gas turbines with a total capacity of 13 MW, six spray dryers and two heat exchangers. In the analysis, actual operational data over one‐month period are utilized. The so‐called CogeNNexT code is written in C++ and developed to analyze energetic and exergetic data from a database. This code is also used to analyze turbines, spray dryers and heat exchangers in this factory. Specifications of some parts of system components have been collected from the factory. Based on the 720 h data pattern (including 43 200 data), the mean energetic and exergetic efficiency values of the cogeneration system are found to be 82.3 and 34.7%, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Dynamic optimization of a cogeneration plant for an industrial application with two different hydrogen embedding solutions

Seasonal storage of hydrogen is a valuable option today increasingly considered in order to optimize cogeneration plants under continuous operation in an incentive framework where electricity sale to the national grids is becoming less economically profitable than in the past. The paper concerns the numerical study and optimization of a cogeneration plant installed in an industrial site having an availability of hydrogen over a continuous time scale, to meet the energy needs and mitigating the environmental impact of the plant operation by reducing the energy withdrawal from traditional sources. Two alternatives are analyzed into detail: the former regards energy production through an internal combustion engine, this last properly controlled to be fueled with blends of natural gas and increasing percentages of hydrogen, the latter concerning the addition of fuel cells to the proposed layout to further reduce the electricity integration by the grid. The dynamic response of the cogeneration system under examination is dynamically evaluated to efficiently fulfill the industrial loads to be fulfilled. First, optimization is performed by implementing a PID controller to better track the industrial demand of electric energy. The main results of this solution reveal a ?81% reduction of excess electricity, a ?7% reduction of natural gas consumed but a 47% raise of CO₂ emissions due to the increase in thermal integration. Then, an additional energy generation from fuel cells is assumed. An economic analysis is carried out for each of the implemented configurations. The adoption of fuel cells, despite requiring a greater initial investment, allows obtaining a SPB of 1,4 years (? 16%), 1,17 Mln € of avoided costs (? 18,5%) and 1320 t/year of CO₂ emissions avoided (? 95%) with respect to the initial layout.     

Organic Rankine Cycle coupling with a Parabolic Trough Solar Power Plant for cogeneration and industrial processes

Over the last 25 years solar power plants based on parabolic trough concentrators have been developed for the commercial power industry. On the other hand, in recent years, a way to harness the solar energy is to cogenerate through Concentrated Solar Power (CSP) technology coupled to an Organic Rankine Cycle (ORC) with potential applications to industrial processes. In this work we present a study of a small CSP plant coupled to an ORC with a novel configuration since useful energy is directly used to feed the power block and to charge the thermal storage. In order to analyze this novel configuration we consider a case study with cogeneration applied to textile industrial process at medium temperature. It turns out that this configuration reduces the size of the thermal storage disposal. The performance of the solar power plant was simulated with TRNSYS to emulate real operating conditions. We show the design, study and simulation results, including the production and efficiency curves for our load profile. Our results show that our system is a promising option for applications to medium temperature processes where electrical and heat generation is required.     

Experimental activity on two tubular solid oxide fuel cell cogeneration plants in a real industrial environment

The EOS project carries on an industrial research on stationary fuel cells based on the SOFC technology developed by Siemens, through a co-operation between TurboCare S.p.A. and Politecnico di Torino. Two SOFC units have been installed and operated in the TurboCare workshop. The running hours of the CHP100 generator are more than 16,400 h; the 5-kW Alpha6 generator is in operation since more than 10′000 h.     

Enhancement of transient stability of an industrial cogeneration system with superconducting magnetic energy storage unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an external fault of utility power system occurs. An actual external fault case and a simulated internal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, an SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.     

Economic evaluation for adoption of cogeneration system

An optimal planning for gas turbine cogeneration system was applied to find whether or not the adoption of the system to an office building or hotel in Seoul, Korea is profitable. The planning problem considered in this study is to determine the optimal configuration of the system equipments and optimal operational policy of the system when the annual energy demands of electric power, heat and cooling are given a priori. The optimal configuration of the system equipments has been determined based on annual cost method with proper choice of representative energy demand patterns obtained for the building and hotel in a 1-year period. A mixed-integer linear programming and the branch and bound algorithm have been used to obtain the optimal solution. The planning method employed here may be applied to making decision on the adoption of the cogeneration plant to any specific office building or hotel.     

Assessment of potential for natural gas-based cogeneration in Thailand

Using the results of a comprehensive data analysis of final energy consumption in industry and commercial buildings, the assessment has been made of the potential for gradual implementation of cogeneration plants in these facilities. In doing so, plans for the expansion of the natural gas pipeline distribution network in Thailand are taken into consideration. The sample comprises of 2540 factories and 1651 commercial buildings from which it was found that 817 factories and 966 commercial buildings were suitable for the implementation of natural gas-based cogeneration technologies until 2020. By the implementation of cogeneration in these facilities, it is possible to save 3.2% of the total primary energy consumption in Thailand in 2003.     

Exergy optimization for an endoreversible cogeneration cycle

Exergy optimization has been carried out for an endoreversible cogeneration cycle using finite-time thermodynamics. The optimum values of the design parameters of the cogeneration cycle at maximum exergy output were determined. Our model is more general than the endoreversible power cycle found in the literature. The effects of design parameters on exergetic performance are investigated and the results discussed.     

How process and power plant changes can increase industrial cogeneration: The case of kraft pulp mills

Industrial cogeneration can be substantially increased in energy intensive process industries, such as pulp and paper, by making process and operating changes such as reducing water use, minimizing effluent discharge, generating chemicals on-site and drying biomass fuels. The economic benefits of cogeneration are demonstrated by comparing three cases. The first is the no generation case in which steam is generated for process use and electric power is purchased from the utility. The second is the thermal match case in which steam is generated at a pressure substantially higher than needed for process and passed through a turbine to generate electric power before being used to meet the plant's thermal demands. In the third case, the minimum cogeneration case, more steam is produced than required by the plant. The additional steam is expanded through the turbine-generator to a condenser and generates additional electricity which can be sold. The study is based upon the conceptual design of a hypothetical 1000 tons/day bleached kraft pulp mill scheduled to begin operation in the United States in 1985, but the general approach and conclusions are applicable to a wide variety of industries with high energy demands.     

Market value for thermal energy of cogeneration:: using shadow price estimation applied to cogeneration systems in Korea

This study empirically analyzes the appropriateness of the current tariffs for district heating in Korea. For this purpose, we adopt the duality concept applied to the output distance function, and estimate the shadow price of heat produced from cogeneration. In addition, the analytical model takes account for the inputs of labor and capital as well as fuel as input outlays of cogeneration. The empirical results show that the current heat tariff determined by the public energy policy might be undervalued by about 15–53%. This implies that the retail price of district heating in Korea might be distorted at least in the sense of economics.     

热、电、煤气三联产环境影响评价若干问题探讨

本研究在对比分析不同工艺路线的基础上,针对热、电、煤气联产项目,进行了环境影响因素的识别,提出进行该类项目环境影响评价需特别关注的若干问题,主要包括：（1）由于热电煤气三联产工程增加了煤干馏气化系统与煤气净化系统,工艺构成中环境影响因素与污染因子发生了较大变化,环境影响识别与评价因子的筛选必须要充分反映出由于增加干馏气化系统与煤气净化装置带来的新的影响与相关问题的分析。（2）应及时对评价内容与评价重点做出调整。考虑到煤气净化过程中含有酚氰废水,荒煤气中含苯并芘等,因此需要将水环境影响评、环境风险评价也作为评价的重点问题。（3）由于热、电、煤气三联产项目生产环节,存在着有毒有害气体突发性环境污染事故的可能性,含酚氰废水处理工艺的状况,热、电、煤气三联产项目的厂址选取不仅仅是满足于一般热电联产项目的选址要求,同时还必须考虑突发性环境污染风险事故的影响。     

Energy balance and cogeneration for a cement plant

The cement industry is an energy intensive industry consuming about 4 GJ per tonne of cement produced. A thermodynamic analysis for cogeneration using the waste heat streams is not easily available. Data from a working 1 Mt per annum plant in India is used to obtain an energy balance for the system and a Sankey diagram is drawn. It is found that about 35% of the input energy is being lost with the waste heat streams. A steam cycle is selected to recover the heat from the streams using a waste heat recovery steam generator and it is estimated that about 4.4 MW of electricity can be generated. This represents about 30% of the electricity requirement of the plant and a 10% improvement in the primary energy efficiency of the plant. The payback period for the system is found to be within two years.     

Targeting for cogeneration potential through total site integration

Total site integration offers energy conservation opportunities across different individual processes and also to design as well as to optimize the central utility system. In total site integration of the overall process, indirect integration with intermediate fluids or through a central utility system are preferred as it offers greater advantages of flexibility and process control but with reduced energy conservation opportunities. To achieve the maximum possible indirect integration between processes assisted heat transfer, i.e., heat transfer outside the region between process pinch points, plays a significant role. A new concept is proposed in this paper for total site integration by generating a site level grand composite curve (SGCC). Proposed SGCC targets the maximum possible indirect integration as it incorporates assisted heat transfer. In this paper, a methodology is proposed to estimate the cogeneration potential at the total site level, utilizing the concept of multiple utility targeting on the SGCC. The proposed methodology to estimate the cogeneration potential is simple and linear as well as utilizes the rigorous energy balance at each steam header.     

Study of a cogeneration plant for agro-food industry

A technical and economic feasibility study for a natural gas fueled cogeneration plant was conducted in an important Italian pasta and animal feed factory. The layout analysis pointed out three main divisions; in each division electric and thermal users were pointed out and their effective energy consumption and power demand rate was monitored. A technical feasibility analysis was then carried out to determine the type and scale of the possible Combined Heat and Power (CHP) plants focusing on Internal Combustion Engines (ICEs) and gas turbine based power plants. The actual energy costs were evaluated on the base of the energy bills for the biennium 1996–97 while the detailed economic feasibility analysis was conducted on the base of the offers received from manufacturers on the market. The results obtained show the possibility to have low payback periods and appealing internal rate of returns when investing on ICEs based CHP plants covering the entire electric demand and partially fulfilling the thermal needs of the factory.