Proposal and characteristics evaluation of a CO2-recovering hybrid power generation system utilizing solar thermal energy

A CO₂-recovering hybrid power generation system utilizing solar thermal energy is proposed. In the system, relatively low temperature saturated steam around 220°C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine in which generated CO₂ is recovered based on the oxygen combustion method. Hence, solar thermal utilization efficiency is considerably higher as compared with that of conventional solar thermal power plants in which superheated steam near 400°C must be produced for use as the working fluid of steam turbines; the requirement for solar radiation in the location in which the system is constructed can be significantly relaxed. The proposed system is a hybrid energy system using both the fossil fuel and solar thermal energy, thus the capacity factor of the system becomes very high. The fuel can be used exergetically in the system; i.e., it can be utilized for raising the temperature of the steam heated by utilizing the turbine exhaust gas more than 1000°C. The generated CO₂ can be recovered by using an oxygen combustion method, so that a high CO₂ capturing ratio of near 100 percent as well as no thermal NO_x emission characteristics can be attained. It has been shown through simulation study that the proposed system has a net power generation efficiency of 63.4 percent, which is higher than 45.7 percent as compared with that of the conventional power plant with 43.5 percent efficiency, when the amount of utilized solar energy is neglected and the temperature of the saturated steam is 220°C.     

Life cycle assessment and economical evaluation of superconducting magnetic energy storage systems in a power system

In recent years, the introduction of superconducting magnetic energy storage systems (SMES) into a power system is drawing considerable research effort because of their high efficiency rate and large storage capacity characteristics. In this paper, the introduction of SMES into a power system and its effects on energy and on environmental issues are addressed. The analysis results show that the introduction of SMES can considerably cut down CO₂ emissions without increasing the production cost if it substitutes for the operation of thermal plants during peak load period. However, to achieve this, nuclear plants are also needed for charging purposes. Thus, an algorithm to find the best generation mix, subject to CO₂ emissions constraints and nuclear plant introduction constraints, is proposed. The inclusion of nuclear plant constraints increases the coal consumption, hence CO₂ emissions. Nevertheless, in most of the analyzed cases, the introduction of SMES could attain important cost savings and environmental conservation. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 32–44, 2000     

Influence of the Emissions Trading Scheme on generation scheduling

The paper investigates the effects of emissions constraints and Emissions Trading Scheme (ETS) on the generation scheduling outcome. ETS is a cap-and-trade market mechanism that has been introduced in European Union in order to facilitate CO₂ emissions management. This scheme gives generators certain amount of CO₂ allowances which they can use to cover emissions produced during energy generation. In a current setting, most of the allowances are given for free. However, under ETS generators also have an opportunity to buy and sell CO₂ allowances on the market. Since generation power outputs are bounded by the amount of CO₂ emissions that they are allowed to produce over time, it is becoming increasingly important for generating units to manage their allocations in the most profitable way and decide when and how much of permissions to spent to produce electricity. The method proposed here allows for modeling of this new limitation by including costs of buying and selling of CO₂ allowance in the generation scheduling procedure. It also introduces additional emissions constraints in the problem formulation. Although CO₂ permissions and energy are traded in separate markets, the proposed formulation permits analysis on how emission caps and emission market prices can influence market outcome. The method is illustrated on a 5-unit system. Given examples compare (i) a base-case when all generators have made a decision to use portions of their total free allocations that do not cause any shortfall during the investigated time period; (ii) two cases when the least expensive generators’ decisions on the amount of free allowances they are willing to use during the considered period are insufficient. In all cases generators also submit prices at which they expect to be able to “top-up” or sell allowances on the market, however, only in the second and third case the “buying” option becomes active and affects generation scheduling and total costs.In addition, the paper investigates how aggregation of emissions allowances of generators belonging to the same company can affect market clearing.     

提高能源效率的主要技术与途径

与1978年相比,2008年我国电力工业通过降低供电煤耗及线损节约了3．8亿tce,减少二氧化碳排放约9．2亿t,减少二氧化硫排放约320万t,为我国节能减排作出了巨大贡献。但未来我国电力工业将随着中国经济的发展而持续增长,其能源消耗量以及二氧化碳、二氧化硫的排放量将呈不断增加的趋势。这将对电力工业的能效提出严峻的挑战。研究提高发电、输电、配电及用电的能效将具有重要的现实意义。介绍了美国发电、输电、配电及用电方面提高能效的先进技术,结合我国发布的行业标准,探讨提高我国发输配用电效率的途径。     

Proposal and Evaluation of a New‐Type Cogeneration System for Energy Saving and CO2 Emission Reduction

The paper proposes a cogeneration system which generates four types of energy or material resources: electricity, steam, hot water, and freshwater. The proposed system can capture CO₂, and be constructed on the basis of a combined cycle power generation system which consists of a gas turbine and a back‐pressure extraction turbine. In the proposed system, power is produced by driving the gas turbine system. High‐pressure saturated steam with medium temperature is produced in the heat recovery steam generator by using gas turbine exhaust gas, and then superheated with a regenerative superheater in which the fuel is burned by using oxygen instead of air for driving the steam turbine generator. Water and CO₂ are recovered from the flue gas of the regenerative superheater. It has been estimated that the proposed system has a net power generation efficiency of 41.2%, a heat generation efficiency of 41.5%, and a total efficiency of 82.7%. Freshwater of 1.34 t/h and CO₂ of 1.76 t/h can be recovered. It has also been shown, when a case study was set and evaluated, that the proposed system can save 31.3% of energy compared with the conventional energy supply system, and reduce CO₂ emission by 28.2% compared with the conventional cogeneration system. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Evaluation of energy saving and CO2 emission reduction technologies in energy supply and end‐use sectors using a global energy model

Assessments of global warming mitigation technologies are important for achieving the Kyoto target and planning post‐Kyoto regimes. Regional differences in energy resources, growth in energy consumption, current technology diffusions, etc., should be considered in the assessments. A global energy systems model, DNE21+, with high regional resolution had treated the energy supply sectors in a bottom‐up fashion and the end‐use sectors in a top‐down fashion, which was expressed by using long‐term price elasticity. However, the assessments of technological options in the end‐use sectors are currently more important, particularly for the near and middle terms. In order to evaluate the technological options not only in the energy supply sectors but also in the end‐use sectors for energy savings and CO₂ emission reductions, DNE21+ has been modified for treating two energy‐intensive end‐use sectors, i.e. steel and cement sectors, in the bottom‐up fashion. The results reveal that the cost‐effective global CO₂ emission reductions in 2030 for stabilizing the atmospheric CO₂ concentration at 550 ppmv in comparison with that in the reference case would be approximately 68 MtC/yr and almost zero in the steel and cement sectors, respectively. The cost‐effective options include next‐generation coke ovens and coke dry quenching (CDQ) in the steel sector. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Characteristics and economic evaluation of a CO2‐capturing solar thermal hybrid power generation system with heat storage

For wide use of a power plant utilizing solar energy, improvement of its economics is important. Both the economics and characteristics of a CO₂‐capturing solar thermal hybrid power generation system are evaluated in this paper. Since a relatively low temperature steam of 220 °C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine, the solar collector can attain high heat collecting efficiency. The net fuel‐to‐electricity conversion efficiency of the hybrid system is estimated to be higher than 60% on the lower‐heating‐value‐ basis. It has been estimated that the gross income and the period of depreciation of the proposed system are 34.8 × 10⁵ yen/year and 8.89 years, respectively, and that the system is economically feasible, under the assumptions of a solar collector area of 10 ha, a maximum net power output of 4 MW, and a heat storage capacity of 2000 m³. The amount of fuel saving and reduction of CO₂ emission of our system, compared to a conventional natural gas firing plant, are also estimated in the paper. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 21–29, 1999     

An evaluation of the optimal generation mix for controlling carbon dioxide emissions

This paper presents an efficient computational algorithm for selecting the optimal generation mix considering CO₂ emissions. To demonstrate the effectiveness and feasibility of the proposed method, a fundamental study of the evaluation of the optimal generation mix for controlling CO₂ emissions is indicated. Furthermore, by using a parametric analysis which considers load characteristics as parameters, a general trend for the optimal generation mix which is affected by controlling CO₂ can be derived. The proposed method is based on an optimization method known as simulated annealing. In the method, solutions in a generation mix problem are equivalent to state of a physical system, and the cost of a solution is equivalent to the energy of a state. The proposed method can easily accommodate not only CO₂ emissions but also many practical constraints of generation expansion planning, such as integer solutions of unit capacities, condition of existing units, and so on. Case studies with various annual load patterns (combinations of annual load factors and the shapes of annual load duration curve) are presented and discussed. Consequently, a general trend for selecting generation technologies that should be added to a power system is derived, i.e., a useful guideline for studying generation expansion planning under controlling CO₂ emissions can be provided.     

实施非水可再生能源配额情景下的发电行业CO2排放预测

发电行业是落实中国碳减排目标的重点领域。为实现中国到2020年单位国内生产总值CO₂排放比2005年下降40%~45%和非化石能源占一次能源消费比重达到15%左右的碳减排目标,国家能源局拟实行可再生能源配额制,要求2020年各煤电企业承担的非水可再生能源发电量配额与煤电发电量的比重达到15%以上。分别基于国家《能源发展战略行动计划（2014-2020年）》和征求意见的15%非水可再生能源发电量配额政策,对发电行业到2020年的CO₂排放情况进行了预测,并基于2020年全国的碳减排目标对发电行业的碳减排任务进行了计算。预测结果表明,实施15%的非水可再生能源配额之后,2020年非水可再生能源发电量将在行动计划预计值的基础上进一步提高,达到7514亿kW·h,在总发电量中占比9.94%,相应地,单位发电量CO₂排放量为580.5 kg/（MW·h）,比2005年下降27.4%。     

Proposal and evaluation of a gas engine and gas turbine hybrid cogeneration system in which cascaded heat is highly utilized

A high‐efficiency cogeneration system (CGS) is proposed for utilizing high‐temperature exhaust gas (HTEG) from a gas engine (GE). In the proposed system, for making use of heat energy of HTEG, H₂O turbine (HTb) is incorporated and steam produced by utilizing HTEG is used as working fluid of HTb. HTb exhaust gas is also utilized for increasing power output and for satisfying heat demand in the proposed system. Both of the thermodynamic characteristics of the proposed system and a gas engine CGS (GE‐CGS) constructed by using the original GE are estimated. Energy saving characteristics and CO₂ reduction effects of the proposed CGS and the GE‐CGS are also investigated. It was estimated that the net generated power of the proposed CGS has been increased 25.5% and net power generation efficiency 6.7%, compared with the original GE‐CGS. It was also shown that the proposed CGS could save 27.0% of energy consumption and reduce 1137 t‐CO₂/y, 1.41 times larger than those of GE‐CGS, when a case study was set and investigated. Improvements of performance by increasing turbine inlet temperature were also investigated. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 37– 45, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20708     

Game theoretic analysis for carbon emission permits trading among multiple world regions with an optimizing global energy model

Carbon emissions which would cause global warming were agreed to be constrained at COP3 in Kyoto. In addition, carbon emission permits trading was also approved to be introduced. The emission permits trading is expected to achieve efficient carbon emission reduction, equalizing the marginal costs of the emission reduction for the participating countries. In other words, the permits trading allows participants to reduce emissions where it is least expensive to do so. However, the inadequate introduction of the trading systems may impose an unfairly greater burden on some countries, and therefore careful evaluation of the system would be indispensable for its implementation. In this paper, we attempt to analyze emission permits trading, using the theory of cooperative games with a global energy model of optimization type. We assume that seven world regions as players participate in the permits trading system under the condition of the emission reduction target presented at COP3 and so on, and show the nucleolus of the grand coalition games, and the computational results of primary energy supplies and CO₂ shadow prices. The insights of this research indicate that in order to stabilize the grand coalition, a noticeable amount of additional transfer of money would be needed besides the payments associated with the emission permits transactions. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 40–50, 2000     

A method for load frequency control using battery in power system with highly penetrated photovoltaic generation

It is generally believed that large battery systems will be needed to store surplus electric energy due to the high penetration of renewable energy (RE) such as photovoltaic generation (PV). Since the main objective of high penetration of RE is to reduce CO₂ emissions, reducing kWh output of thermal generation that emits large amounts of CO₂ in power systems should be sufficiently considered. However, thermal generation plays an important role in load frequency control (LFC) of power systems. Therefore, if LFC could be performed with batteries and hydropower generation, the kWh output of thermal generation could be reduced significantly. This paper presents a method of LFC using batteries in a power system with highly penetrated PVs. An assessment of the effect of the proposed method considering mutual smoothing effect of highly penetrated PVs is made. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(4): 22–31, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22425     

The Conceptual Process Arrangement of a Steam–Gas Power Plant with Fully Capturing Carbon Dioxide from Combustion Products

The article proposes a new concept for designing power plants operating on natural gas and involving means for fully removing carbon dioxide from the cycle in the liquid phase form in order to subsequently bind or bury it for reducing the emissions of greenhouse gases into the atmosphere. In contrast to means used in the conventional power plant process arrangements for capturing CO₂ from the combustion products, the proposed concept involves the need to develop fundamentally new power engineering technologies, in which the CO₂ utilization system is intrinsically built into the cycle structure already at the initial stage of power plant design and optimization of its parameters. As an example, the process flow diagram of a natural gas fired power plant generating electricity and heat is considered. The integral indicators characterizing the thermal efficiency of such a power plant are given and compared with the similar indicators of the operating or newly designed plants fitted with CO₂ capturing systems, the process arrangement of which implies direct emission of carbon dioxide into the atmosphere. The comparison is carried out for the average ratio between the generated electricity and heat that has historically been established in the climatic zone of central Russia. It is shown that the proposed cycle features high thermodynamic efficiency and competitiveness with respect to the same indicators of alternative systems for combined generation of electricity and heat. The article suggests versions of the CO₂ capturing system configuration that allows, with the modern technological level of equipment, the carbon dioxide emissions to be reduced down to 0.5–5.0% of the total amount produced in firing natural gas.     

A Service Business Model for Saving Energy and Reduction of CO2 Emissions Using Inverters

This paper considers the effectiveness of the service business approach for reducing CO₂ emissions. “HDRIVE” is a service business using inverters to reduce the energy consumption of motor drive. The business model of this service is changed to find new opportunities of CO₂ emission reduction by combining various factors such as financial services or long‐term service contracts. Risk analysis of this business model is very important for providing stable services to users over the long term. The HDRIVE business model is found to be suitable for this objective. This service can be applied effectively to industries such as chemicals or steel, where CO₂ emissions are very large, and has the possibility of creating new business considering CDM or trading CO₂ emission rights. The effectiveness of this approach is demonstrated through several examples in real business. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 40–48, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21242     

A method for compensating customer voltage drops due to nighttime simultaneous charging of evs utilizing reactive power injection from battery chargers

When we consider global warming, the reduction of CO₂ emissions is one of the most important issues which require urgent solutions. One option is to integrate low‐CO₂‐emission generators to the grid as much as possible. Another option is to replace ine?cient vehicles based on internal‐combustion engines with electric ones (EVs). Due to the latter, we can easily predict that most consumers will charge EVs' batteries during nighttime. Thus, excessive voltage drops due to nighttime simultaneous charging are expected to be a possible future problem. This paper proposes a method for compensating the voltage drops by injecting reactive power from EV battery chargers. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(1): 19–29, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22390     

Evaluation of a plug‐in hybrid electric vehicle considering power generation best mix

In the transport section, it is necessary to reduce the amount of CO₂ emissions and oil dependence. Bio fuels and fuel cell vehicle (FCV), electric vehicle (EV) and plug‐in hybrid electric vehicle (PHEV) are expected to reduce CO₂ emissions and oil dependence. We focus on PHEV. PHEV can reduce total energy consumption because of its high efficiency and can run with both oil and electricity. Introduction of PHEV reduces oil consumption, but it also increases electricity demands. Therefore, we must evaluate PHEV's CO₂ reduction potential, not only in the transport section but also in the power grid section. To take into account the distribution of the daily travel distance is also very important. All energy charged in the PHEV's battery cannot always be used. That influences the evaluation. We formulate the total model that combines passenger car model and power utility grid model, and we also consider the distribution of the daily travel distance. With this model, we show the battery cost per kWh at which PHEV begins to be introduced and oil dependence in the passenger car section is to be reduced to 80%. We also show PHEV's CO₂ reduction potentials and effects on the power supply system. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 12–22, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20920     

The influence of nuclear generation on CO2 emissions and on the cost of the Spanish system in long-term generation planning

This paper presents the influence of a nuclear generation option on CO₂ emissions and on the cost of the Spanish long-term generation system by means of the development of a stochastic linear model, based on the software GAMS, where multiple aspects have been contemplated: the uncertainty regards fossil fuel and CO₂ emission allowance prices by analysing different scenarios, the stability and supply security of the system by considering different restrictions, the maximum grade of penetration of the different technologies by means of commissioning plans, etc. Only two of the conclusions drawn are focused on here. First, it is possible to get a clean system without nuclear power generation but the cost would be higher than in the case where the existing nuclear power plants continue to operate. Second, the development of clean coal technologies could be affected negatively by the development of nuclear generation.     

Mechanism of CO_2 Emission Reduction by Global Energy Interconnection

The challenge of global warming has become a driving force for a global energy transition. The Global Energy Interconnection(GEI) is a modern energy system aimed at meeting the global power demand in a clean and green manner. With the development of clean replacement, electricity replacement, and grid interconnection strategies, GEI contributes to the global temperature control by dramatically reducing the level of energy-related CO_2 emissions. This study proposes an integrated framework for analyzing the mechanism of CO_2 emission reduction via GEI implementation. The obtained results demonstrate that the total cumulative contribution of GEI to mitigating the effects of CO_2 emissions(estimated by conducting a scenario analysis) corresponds to a total reduction of 3100 Gt CO2. The contributions of the clean replacement, electricity replacement, and carbon capture and storage GEI components to this process are equal to 55, 42, 5%, respectively. Using GEI, the utilization of clean energy in 2050 will increase by a factor of 4.5 at an annual growth rate of 4.4%, and the electrification rate will be 2.4 times greater than the current one.     

电力行业污染物排放权交易模型

为了实现排污配额的优化配置,以某一区域的电力行业为例,基于电力企业运营资源费用、发电成本、污染物治理成本、污染物减排绩效、污染物排污交易价格以及污染物排放配额等因素,构建主要大气污染物（SO2、NOx、CO2）排污交易优化模型,采用多情景分析方法,对比分析各因素对电力行业污染物交易以及电厂运行的影响.结果表明,改变排放配额的交易价格和政府的绩效价格,各电厂的电力生产量以及区域的外购电量不变,但各电厂污染物的交易状况发生改变,出现多种交易类型.该模型能够有效解决区域环境治理及电力行业污染物减排问题,实现对区域污染物排放总量和优化能源结构的有效控制,为未来区域能源规划、区域环境质量改善、电厂运行优化以及建立区域污染物排放交易机制提供参考.     

Life cycle CO2 emissions of a photovoltaic/wind/diesel generating system

A photovoltaic/wind/diesel generating system with a battery (PWD system) is discussed from the viewpoint of total CO₂ gas emissions during system lifetime. The total emissions are the sum of the emissions occurring at manufacturing and operating. First, the manufacturing CO₂ emissions of the photovoltaic generator and the wind turbine generator are calculated by “the process analysis method.” This method considers the material used in each generator, its weight and its CO₂ emission rate. On the other hand, the manufacturing CO₂ emissions of the diesel generator and the battery are calculated using “the interindustry (input‐output) table.” Second, the PWD system is operated on a computer so that the fuel consumption of the diesel generator is a minimum assuming that hourly series data of electric load, insolation intensity, wind speed, and air temperature are known during the year. And CO₂ emissions occurring at system operation are obtained from the annual fuel consumption of the diesel generator. The results show that CO₂ total emissions of the PWD system are lower than those of the conventional diesel generator system. The CO₂ total emissions reach a minimum when the photovoltaic/wind generating ratio is 50/50. The CO₂ emissions of manufacturing decrease with increasing of the wind generating ratio from 100/0 to 0/100. The CO₂ total emissions decrease as the natural energy ratio increases. It is, however, saturated to about 60% when the ratio is more than 60%. And the CO₂ total emissions increase with increasing of the battery capacity. It is concluded that the PWD system plays an important role in decreasing considerably the CO₂ total emissions while the total system cost is high under the present price circumstances. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 14–23, 2002