Evaluation of output and unit cost of power generation systems utilizing solar energy under various solar radiation conditions worldwide

Characteristics and economics of three power generation systems which utilize solar energy were investigated and compared for systems located in five different regions. The three systems investigated were a solar thermal system, a solar photovoltaic system, and a CO₂‐capturing hybrid power generation system utilizing solar thermal energy (referred to as the hybrid system) which has been proposed by the authors. The net generated power energy and the net exergetic efficiency of the hybrid system have been estimated to be larger and higher, respectively, than those of the others. Economic evaluation reveals that the unit cost of generated power energy of the solar thermal system changes most widely corresponding to the change in solar radiation condition and that the cost of the hybrid system changes the least. In general, the most economical system has been estimated to be the solar thermal system in a location which is superior in solar condition and to be the hybrid system in a not so good solar condition. The solar photovoltaic system has the possibility of being the most economical if its construction cost is greatly improved, though the hybrid system is still the most economical under considerably worse solar conditions such as in Osaka. © 1999 Scripta Technica, Electr Eng Jpn, 127(3): 1–12, 1999     

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.     

CO2 reduction effect of the utilization of waste heat and solar heat in a city gas system

We evaluated total energy consumption and CO₂ emissions in the phases of a city gas utilization system from obtaining raw materials to consuming the product. Assuming monthly and hourly demand figures for electricity, heat for space heating, and hot water in a typical hospital, we explore the optimal size and operation of a city gas system that minimizes the life cycle CO₂ emissions or total cost. The cost‐effectiveness of conventional cogeneration, a solar heating system, and hybrid cogeneration utilizing solar heat is compared. We formulate a problem of mixed integer programming that includes integral parameters that express the state of system devices such as the on/off condition of switches. As a result of optimization, the hybrid cogeneration can reduce annual CO₂ emissions by 43% compared with the system without cogeneration. The sensitivity of CO₂ reduction and cost to the scale of the CGS is also analyzed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(1): 22–32, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10369     

Potential evaluation of energy supply system in grid power system,commercial, and residential sectors by minimizing energy cost

If the economic activity in the commercial and residential sector continues to grow, improvements in energy conversion efficiencies of energy supply systems is necessary for CO₂ mitigation. In recent years, the electricity driven hot water heat pump (EDHP) and the solar photovoltaic (PV) have been commercialized. The fuel cell (FC) of co‐generation system (CGS) for the commercial and residential sector will be commercialized in the future. Copyright © 2004 Wiley Periodicals, Inc. The aim is to indicate the ideal energy supply system of the users sector, which manages both the economical cost and CO₂ mitigation, considering the grid power system. In this paper, cooperative Japanese energy supply systems are modeled by linear programming. It includes the grid power system and energy system of five commercial sectors and a residential sector. The demands of sectors are given by the objective term for 2005 to 2025. Twenty‐four‐hour load for each three annual seasons are considered. The energy systems are simulated to minimize the total cost of energy supply, and to mitigate the CO₂ discharge. As a result, the ideal energy system at 2025 is shown. The CGS capacity grows to 30% (62 GW) of the total power system, and the EDHP capacity is 26 GW, in commercial and residential sectors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 9–19, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20361     

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.     

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     

基于Petri网的太阳能集热系统的研究

太阳能集热系统是连续变量动态系统和离散事件动态系统相互作用的混杂系统。基于层次型结构模型框架下,分析了太阳能集热控制系统的混杂特性。在传统的混合Petri网基础上,建立了推广混合Petri网的太阳能集热仿真模型。并利用Matlab中的Simulink和Stateflow对太阳能集热系统推广混合Petri网模型进行仿真分析,为进一步优化混合控制器性能奠定了基础。     

Characteristics evaluation of a CO2‐capturing power generation system with reheat cycle utilizing regenerative oxygen‐combustion steam‐superheater

A new CO₂‐capturing power generation system is proposed that can be easily realized by applying conventional technologies. In the proposed system, the temperature of medium‐pressure steam in a thermal power plant is raised by utilizing an oxygen‐combusting regenerative steam‐superheater. The CO₂ generated by combusting the fuel in the superheater can be easily separated and captured from the exhaust gas at the condenser outlet, and is liquefied. The superheated steam is used to drive a steam turbine power generation system. Using a high‐efficiency combined cycle power generation system as an example, it is shown that the proposed system can increase the power output by 10.8%, and decrease the CO₂ emissions of the entire integrated system by 18.6% with a power generation efficiency drop of 2.36% compared with the original power plant without CO₂ capture, when the superheated steam temperature is 750 ^°C. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(1): 35–41, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20575     

Influence of system operation method on CO2 emissions of PV/solar heat/cogeneration system

A PV/solar heat/cogeneration system is assumed to be installed in a hotel. The system is operated with various operation methods: CO₂ minimum operation, fees minimum operation, seasonal operation, daytime operation, and heat demand following operation. Of these five operations, the former two are virtual operations that are operated with the dynamic programming method, and the latter three are actual operations. Computer simulation is implemented using hourly data of solar radiation intensity, atmospheric temperature, electric, cooling, heating, and hot water supply demands for one year, and the life‐cycle CO₂ emission and the total cost are calculated for every operation. The calculation results show that the two virtual and the three actual operations reduce the life‐cycle CO₂ emission by 21% and 13% compared with the conventional system, respectively. In regard to both the CO₂ emission and the cost, there is no significant difference between the two virtual operation methods or among the three actual operation methods. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 54–63, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20414     

A CO2-recovering nonpolluting high-efficiency gas-turbine power-generation system utilizing saturated steam as its working gas

A carbon dioxide-recovering high-efficiency gas-turbine power-generation system is proposed in which carbon dioxide (CO₂) generated is recovered by adopting the oxygen (O₂) combustion method and no thermal nitrogen oxide is generated. In the system, saturated steam produced by utilizing waste heat is adopted as the working fluid of the gas turbine. Thus, the compressing process of the working fluid gas, which is the most energy-consuming process in generating power by using a gas turbine, is not needed. This makes the system extremely high efficient. By taking saturated steam of 210°C as an example, the characteristics of the system were simulated. The net exergetic efficiency of the system has been estimated to be 48.4 percent by considering both the exergy of the saturated steam and the electric power required not only to generate high-pressure oxygen, but also to liquefy the recovered CO₂. The value is higher than the exergetic efficiency 37.8 percent of large-scale thermal power generation plants using the same natural gas, and is 28.0 percent higher than its efficiency of 37.8 percent, the one estimated if the CO₂ generated is removed and recovered from the stack gas by using alkanolamine-based solvent and the recovered CO₂ is liquefied.     

Construction and power generation characteristics of H2O turbine power generation system utilizing waste heat from factories

A new gas turbine power generation system has been proposed, in which the steam (H₂O) produced by utilizing waste heat from factories is used as the working fluid of gas turbine. A simulation model has been constructed to estimate power generation characteristics of the proposed system by adopting C++ language. It has been shown from simulation results that the proposed system has high exergetic efficiency, that is, the total exergetic efficiency is 46.3% and fuel‐based efficiency is 56.3% for a case where steam with a temperature of 275 °C produced from a garbage incineration plant is used. Sensitivity analysis has also been carried out when usable steam temperature and pressure is changed, together with the case when condenser outlet pressure is changed. Characteristics of a dual fluid gas turbine cycle power generation system (DFGT) have also been estimated in this study. It has been shown that the proposed system has 16.9% higher exergetic efficiency and 41.8% higher fuel‐base exergetic efficiency compared with DFGT. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 38–47, 2000     

Evaluation of the reduction in CO2 emissions by applying Micro‐Grid to home energy supply system

Dispersed generators such as wind power systems, photovoltaic systems, and cogeneration systems are expected to mitigate the environmental burden of energy consumption, and their installation has been promoted recently. Micro‐Grid is focused on as a method to solve some problems in a commercial electric power line when installing a large number of dispersed generators, and some demonstrative research on Micro‐Grid for large‐scale systems is being carried out now. Also, small cogeneration systems for houses, such as gas engines and fuel cells, are expected to improve CO₂ emissions. However, if the power and heat demand of a family are relatively small or are unbalanced, the cogeneration system does not operate effectively. The authors have studied the application of Micro‐Grid for home energy supply, and have developed a control system to solve this problem. The system achieves a reduction of CO₂ emissions and energy costs by sharing electric power and heat among some houses with cogeneration systems. This paper presents an outline of the newly developed system, and in particular describes the effect of the reduction in CO₂ emissions compared with a conventional energy supply method, and the case in which dispersed generators are installed in some houses and operate independently. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 19–27, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20879     

太阳能热发电集热器接收面辐射分布研究

为分析太阳集热器接收面太阳辐射的接收情况, 根据太阳高度角、太阳方位角、晴天模型和集热器进口的几何设计, 采用蒙特卡洛法建立了太阳辐射能束的方向、大小、位置以及抛物反射面镜面反射的关键算法。以西安地区( 纬度) 为例, 分别对夏至、冬至与春分太阳时12 点, 8 点和16 点时进行了计算。结果显示了不同时刻接收面的太阳辐射接收分布情况; 并由面积分求解接收面上的平均辐射强度, 反演了常规设计方法确定的聚光比。研究表明, 该方法可模拟一年中任意时间接收面的太阳辐射情况, 为太阳能热发电系统用集热器辐射分布研究提供了方法。     

Adaptive repetitive control for resonance cancellation of a distributed solar collector field

This paper deals with modelling and control of the outlet temperature in a distributed solar collector field. The resonance dynamics characteristics of this kind of system are similar to those of tubular heat exchangers in the closed‐loop system bandwidth when fast responses are required. Simple low‐order rational models are unable to capture the resonance dynamics, which can be excited by changes in both the heat transfer fluid flow and solar irradiation. This paper proposes a new model derived from a similar model for a tubular heat exchanger. This model allows the use of low‐order controllers, which can be extended to an adaptive control scheme to account for varying resonance frequencies, as a new functionality achieving fast, well‐damped responses. Copyright © 2008 John Wiley & Sons, Ltd.     

含光热集热模块的先进绝热压缩空气储能系统容量配置策略

先进绝热压缩空气储能(AA-CAES)技术不但具有环境友好、成本低、容量大等优点,还拥有热电联储/联供的独特优势,并且能够与外接热源耦合运行。充分考虑AA-CAES电站的热电联储/联供特性,将光热集热模块作为AA-CAES系统的外部扩展热源,提出了光热集热模块耦合AA-CAES系统的优化规划模型。该模型除了计及影响光热集热模块各项实际运行效率的约束外,还综合考虑了AA-CAES电站的规划约束、运行约束以及AA-CAES电站备用出力约束等,并采用大M法对模型中的非线性项进行等价转换,将优化规划模型转化为能被常规商用优化求解器高效求解的混合整数线性规划模型。基于某地区的典型日数据和改进的IEEE 30节点系统进行算例仿真,仿真结果验证了所提模型的有效性。     

Energy saving performance of distributed heating and cooling system

An advanced distributed heating and cooling system utilizing small‐scale high‐performance heat pumps was designed to replace the central heating and cooling system for the AIST laboratory buildings, which have a total floor area of 36,100 m², of which 20,100 m² is occupied by laboratories. In the old system, the total primary energy required for hot water was 44 TJ, and it was 12 TJ for chilled water in FY 2001. The new system is composed of small‐sized high‐performance heat pumps, with an average coefficient of performance (COP) of 3.1. After the reconstruction, the energy consumption was reduced to 37%, and with a total energy saving of 44 TJ for one year. The total CO₂ emission is estimated to be 26%, a reduction of 3000 tons per year. The energy saving is caused by the high‐performance small‐scale heat pumps, the high‐performance total system design that takes laboratory into account, and the suitable operation of the system. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(2): 46–53, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.20977     

太阳能光-热-电转换利用系统的分析

在太阳能光-热-电转换利用的"三环节理论"模型的基础上,对太阳能光-热-电转换利用进行了(火用)经济学分析,并与常规火力发电的(火用)经济学作了对比,提出了化石能源的稀缺(火用)价值和环境成本的观点.探讨了聚焦型太阳能集热器的设计参数对太阳能光-热-电转换利用系统中单位输出(火用)价Cu的影响.     

扩容蒸发式光煤互补发电系统变辐照特性研究

为避免槽式太阳能集热器内变热流量传热和汽液非均匀分布产生,提出了扩容蒸发式太阳能蒸汽发生系统。采用NASA SSE6.0数据库收集的辐照数据,将扩容蒸发式太阳能直接蒸汽发生系统与燃煤机组互补组成复合发电系统,建立复合发电系统的变工况计算模型,并以600 MW机组为例进行了复合发电系统变辐照情况下的日、月、年热力性能分析。研究结果显示：复合发电系统日发电功率与辐照强度曲线变化趋势类似,各月复合发电系统的发电量呈现出夏季较高的趋势,6月份达到峰值2.95×10⁸ kW·h,集热场效率与其趋势相反,机组热功转换率夏季较高,全年为32%~35%;太阳能平均热功转换效率为22.5%,研究结果可为太阳能与燃煤机组互补发电系统的工程应用提供新的方向和思路。     

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     

太阳能热气流发电系统非稳态耦合数值分析

太阳能热气流发电技术是目前国际太阳能研究领域的热点之一，但对带有蓄热层的太阳能热气流发电系统的研究并不多。该文分别建立了集热棚、烟囱和蓄热层的流动与传热数学模型。以西班牙试验电站模型为例进行的非稳态耦合数值计算结果表明：土壤具有较强的蓄热作用且能很好调整系统昼夜发电峰谷差；太阳辐射强度对系统散热损失的影响相当显著，太阳辐射越强，散热量越大；集热棚的顶棚是系统散热损失的主要部件，散热热流密度约为太阳辐射的10%。