A competitive evaluation of urban energy systems from viewpoints of energy conservation and mitigating environmental impact

Although various energy system alternatives for business, commercial, and residential customers have recently been developed in order to reduce energy consumption and CO₂ emission, it is important to evaluate competitive characteristics among such new energy system alternatives quantitatively, in consideration of tradeoff relations among economic cost, energy consumption, and CO₂ emission. In this paper, using multiobjective optimization model for urban energy system planning, two competitive evaluations are performed. One is the break‐even cost analysis for introducing more efficient, but more expensive energy equipment, such as photovoltaic system and fuel cell system. The other is that we evaluate the competitiveness of a certain energy system from the viewpoint of a whole urban area because there are multiple alternatives for attaining the same target of reducing CO₂ emission of energy consumption. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 71–79, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20421     

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 multi‐objective optimization model for determining urban energy systems under integrated energy service in a specific area

The integrated energy service system for a specific area is supposed to deliver electric and thermal energy in an integrated manner for the purpose of reducing cost, primary energy consumption, and CO₂ emission. Under an assumption of the service system, this paper develops a multi‐objective optimization model for determining urban energy systems. Considering the various energy system alternatives, such as photovoltaic generations for residential houses and fuel‐cell cogenerations for business and commercial customers, the model determines the share of the energy system alternatives in order to minimize the above three indices. As numerical examples, this paper illustrates trade‐off analyses in the case when the proposed model is applied to a 2 km × 2 km square area in Osaka. Finally, this paper illustrates the role of various energy system alternatives from CO₂ reduction and fossil energy reduction points of view. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(3): 20–31, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10275     

An Evaluating Model of Photovoltaic Power Output Variations for an Energy System Planning in an Urban Area

This paper presents a mathematical model to evaluate the power output variations from photovoltaic systems (PV) in collaboration with an energy system planning in an urban area, and applied the model to a demonstrating energy system. The evaluating model is developed from per-floor area PV power output variations on the basis of the past 1 year of actual solar insolation. The evaluation of the power variations is represented in terms of a per-floor area standard deviation curve. In case of considering two alternatives, battery-less and battery-installed PV systems, a correlative coefficient curve is calculated, then a total standard deviation curve representing the total PV power variations can be formulated on the basis of a random variable (RV) model. The model is applied as a tool to evaluate the power variation in an energy system. The energy system planning demonstration approaches the optimal planning by minimizing total cost under CO₂ emission reduction and the power variation constraints. The results show the impacts of the constraint of power variation that limit the installation of PV system. The constraint results the increase of the proportion of PV system with battery installation against PV system without battery installation. Consequently, the constraint also degrades the maximum potential of the entire system to reduce CO₂ emission corresponding to the decrease of PV system. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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     

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.     

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.     

离岸微型综合能源系统多目标随机规划

离岸微型综合能源系统与海洋工程的生产工艺环节结合紧密,并独立运行。因此,如何在克服生产工艺环节或外界环境不确定性影响的同时,尽可能减少CO_2的排放,并尽量节省成本是其规划的难点。文中从综合能源系统优化规划的角度,根据能源集线器的思想,建立离岸微型综合能源系统的电-热-CO_2耦合模型,构建以总成本最小、CO_2排放量最少为目标,以电、热网络平衡等条件为约束,并考虑生产工艺环节和外界环境不确定性影响的多目标随机规划模型,进而利用多目标进化算法求解该模型,实现兼顾成本与环保的离岸微型综合能源系统多目标优化规划。通过海上油气平台群及全电舰船的微型综合能源系统的优化规划,验证了所提方法的可行性与有效性。     

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 motivating mitigation mechanism for generators on condition of coordinated regulation of emission and electricity market

Applying supply function equilibrium (SFE) and the first sealed bidding auction, this paper designs a motivating mitigation mechanism for generators based on coordinated regulation of emission market and electricity market. The mechanism separates emission market as two parts: initial emission market and secondary emission market. It begins with electricity regulator and environment regulator promulgating regulatory information. Then generators participate in initial emission market bidding for emission allowances. Based on allocated emission allowances, generators participate in electricity market bidding for load and set emission secondary trade for profit maximization. The mechanism divides generator’s bidding decision into two dynamic and coordinated stages: firstly in initial emission market, then in electricity market. We depict generator’s decision making as two stochastic parameter linear programming models. Solving these models, generator’s optimality demand function in initial emission market, optimality supply function in electricity market, and equilibrium of each market are achieved. We found that under the new mechanism, (i) both bidding price and bidding quantity in each market are ordered based on generators’ operation advantages from higher to lower respectively and (ii) the pricing and allocation rules in each market can effectively motivate generator to mitigate its CO₂ emission. The new mechanism is truly an effective way to coordinate emission market and electricity market. Finally, we present a simulation to test its validity, and these results are fit well to the theoretical conclusions.     

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     

Impacts of ubiquitous technology advances on energy consumption in Japan

We created a mathematical model of the Japanese economy using a macro‐economic modeling framework called a computable general equilibrium model. We used the model to estimate the impacts of the ubiquitous network technology advances on CO₂ emissions in Japan. Four scenarios of the ubiquitous network society in Japan in 2010 were selected. The four scenarios correspond to four different levels of ubiquitous society advancement. In each scenario, we estimated electricity consumption by electronics products, the effects of ubiquitous network application systems on improving energy efficiency, and the industrial structural changes induced by the expansion of the ubiquitous network application services market. Our results indicate that advanced ubiquitous technologies would potentially reduce the CO₂ emissions of the Japanese economy by 2.8%. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(3): 22–30, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20419     

A method for evaluating effects of energy efficiency improvement on carbon dioxide emission reduction

Global warming due to increasing atmospheric carbon dioxide (CO₂) is a matter of serious concern. Energy efficiency improvement has been considered to be the most effective strategy for reducing CO₂ emissions. The acceleration of R&D for energy technologies which have large effects on CO₂ emission reduction should be effective in abating global warming. In this study, the author proposes a method for evaluating the effects of energy efficiency improvement on CO₂ emission reduction. This method utilizes a compact energy system model combined with analytical calculations. Using this method, effects of energy efficiency improvement in Japan in the year 2030 are analyzed. Energy efficiency improvement in thermal power generation, nuclear power generation, and heat utilization are especially effective for reducing CO₂ emissions. The author estimates that CO₂ emissions per capita can be stabilized at the present level by energy efficiency improvement.     

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     

Evaluation of the introduction of a micro‐cogeneration system into residential houses based on monitored daily‐basis energy demand data

In order to reduce CO₂ emission from residential sectors in Japan, PEFC with high efficiency and low environmental impact is expected as one of the promising micro‐cogeneration (µCGS) systems. However, the energy demands in houses largely differ from each other and the profiles are also changed every day. Thus, when µCGS is actually introduced, it is necessary to examine the equipment capacity and operation of µCGS in each house. In this paper, the optimization model is developed in order to evaluate the µCGS based on daily‐basis demand data. Using actually monitored energy demand data in four households, the differences between using daily‐basis data and using the monthly‐average data are evaluated from viewpoints of economic and environmental performance of µCGS systems. Moreover, by adding the penalty factor to disposal heat of µCGS, it is seen that system configuration and system operation of µCGS can attain CO₂ reduction and energy conservation as well as cost reduction. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 20–30, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20653     

Modified multiobjective particle swarm optimization method and its application to energy management system for factories

Conventional energy management systems (EMS) for factories have been developed to minimize energy costs. However, we have to reduce energy consumption and CO₂ emissions to preserve the environment. This paper proposes a multiobjective optimization method based on particle swarm optimization (PSO) to minimize energy costs and CO₂ emissions, and presents its effectiveness through simulation results. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 33–42, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20269     

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     

现货市场下基于混合储能技术的微电网偏差电量优化

现货市场的开展为以微电网运营商为代表的市场新兴主体提供了处理不平衡电量又一渠道.但如何协调其与储能技术的配合,成为市场主体运营的关键之一.首先,对含有微电网主体的现货市场交易和不平衡电量的处理机制进行分析,提出了可跟随偏差电量数值变化的动态考核方法.其次,根据不同来源性质的偏差电量,针对性地调用储能系统的不同单元,构建各市场主体自身利益最大化的博弈模型,并采用改进和声搜索算法进行求解,得到微电网储能系统接收偏差的最佳选择.最后,采用双目标权重模糊处理方法,对构建的储能单元调度模型进行求解,明确储能电池各单元的具体出力情况.中国南方某地区实际案例仿真结果表明:所提出的优化控制策略可以对市场主体的偏差进行有效处理,实现各主体自身利润的显著提升.     

基于纳什议价方法的虚拟电厂分布式多运营主体电能交易机制

伴随着电力市场售电侧的日益开放化,虚拟电厂(virtual power plant,VPP)内不同利益体可通过电能交易提高经济效益.首先,文章针对包含分布式电源的运营商(distributed generation operator,DGO)、云储能运营商(cloud energy storage operator,C...     

Development of an analytical model for generation expansion planning as a tool to provide guidelines for preventing instability in the long‐term electricity market

This paper considers the problem of deciding multiperiod investments for generation expansion planning (GEP) in restructured power systems. This problem has presented a challenge for both market managers and suppliers regarding the stability in the electricity market and minimum income for suppliers over the planning period. In this paper, an analytical model for studying the GEP problem from the viewpoint of a central management entity is presented. The aim of this method is to establish a dynamic balance between energy supply and demand by adjustment of GEP over the horizon of planning so that not only the expected profit is provided for all new generating plants but the long‐term stability in the electricity market is also improved. This analytical model can be utilized by regulatory bodies to obtain some guidelines and thereby to set their policies for improving GEP and preventing instability in the long‐term electricity market. To do so, in this study, the uncertainties of demand and supply have been modeled through two stochastic processes. Furthermore, the market price dynamics and their mutual effects on the GEP's results have been considered. Finally, this nonlinear dynamic optimization problem is solved using a modified genetic algorithm (GA). The efficiency and ability of the proposed method are examined on a test power system. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.