Suitable operational strategy for power interchange operation using multiple residential SOFC (solid oxide fuel cell) cogeneration systems

A suitable operational strategy for a power interchange operation using multiple residential solid oxide fuel cell (SOFC) cogeneration systems for saving energy is investigated by an optimization approach based on mixed-integer linear programming. In this power interchange operation, electricity generated by residential SOFC cogeneration systems is shared among households in a housing complex without allowing a reverse power flow to a commercial electric power system in order to increase electric load factors of the system. For an SOFC cogeneration system operated continuously with the minimum output, two types of operational strategies for the power interchange operation are adopted: an operation to meet the total demand for electricity in intended households by the electricity output of SOFC cogeneration systems and an operation to meet the demand for hot water in each household by the hot water output of the SOFC cogeneration system. To clarify a theoretical limit of the energy-saving effects of the two strategies, this study numerically analyzes optimal operation patterns for 20 households on three representative days. The results show that the former operational strategy, which takes advantage of the high electricity generating efficiency of the SOFC, is more suitable for saving energy as compared to the latter strategy.     

Optimal sizing of residential gas engine cogeneration system for power interchange operation from energy-saving viewpoint

A power interchange operation, in which electricity generated by residential gas engine cogeneration systems is shared among the residences in a housing complex without a reverse power flow to a commercial electric power system, has a high energy-saving effect. In this study, the optimal sizing of the residential gas engine cogeneration system for the power interchange operation is discussed from the energy-saving viewpoint by conducting optimal operational planning based on mixed-integer linear programming. First, the scale effect of the residential gas engine cogeneration system on its performance is identified from the nominal performances of commercial devices. Then, the energy-saving effect of the power interchange operation is analyzed from the optimal operation patterns for various system scales. The result shows that the energy-saving effect increases with the system scale because the heat to power ratio of the system decreases and approaches that of the demand because of the increase in generating efficiency. However, systems with a rated electric output larger than 1 kW exhibit almost the same energy-saving effect. Hence, it is concluded that a system with a rated electric output of 1 kW, which is a commercial device for residential applications, is the optimal scale for the power interchange operation.     

300 MW湿冷汽轮机双转子互换高背压供热改造应用

随着用户需求增加及国家节能减排政策要求,对亚临界300 MW湿冷汽轮机组进行高背压供热改造成为火力发电厂满足对外供热需求和提高机组效率的重要措施之一,而汽轮机在供热期和非供热期双低压转子互换是实现高背压供热改造一个行之有效的手段.以某电厂2号机300 MW机组采用双低压转子互换技术进行高背压循环水供热改造为例,简述了汽轮机在改造过程中需要考虑的主要问题及相应的改造方案.     

Responsiveness of low-income households to hybrid price/non-price policies in the presence of energy shortages: evidence from Colombia

At the beginning of 2016, Colombia was experiencing an energy shortage, and in order to avoid mandatory power cuts, the government launched an unexpected hybrid price/non-price energy-saving policy. In this paper, I evaluate how low-income households in a major Colombian city respond to this policy. Using hourly household electricity consumption data, I find that, on average, households reduce electricity consumption by 4.5% as a result of the policy. It is striking that even low-income households, who consume relatively small amounts of electricity, respond to energy-saving policies and engage in conservation behaviors in the short term. In my analysis, I also find that the effect is stronger the higher the household pre-treatment electricity consumption levels and smaller among poorer households. However, the heterogeneity in terms of income level vanishes once I control for household pre-program electricity consumption levels. Finally, my point estimates are comparable to the impact estimates of policies that are similar to the one I analyze in this paper.     

Effectiveness of an energy-consumption information system on energy savings in residential houses based on monitored data

Reducing energy demand in the residential sector is an important problem worldwide. This study focused on the awareness of residents to energy conservation and on the potential of reducing energy demand through energy-saving activities. To carry out quantitative analysis, an on-line interactive “energy consumption information system” for motivating energy-saving activities is constructed, and it was installed in nine residential houses. By utilizing data of measured power consumption, ambient and room temperatures before and after installation of the system, and the responses of the residents to the system, its effectiveness was evaluated. Major findings were as follows: (1) installation of the system led to a 9% reduction in power consumption, (2) comparisons of daily-load curves and load-duration curves for each appliance, before and after installation, revealed various energy-saving behaviors of the household members such as the reduction of standby power and better control of appliance operation, and (3) energy-conservation awareness affected not only the power consumption of the appliances explicitly shown on the display monitor, but also other household appliances.     

A comparative evaluation of household preferences for solar photovoltaic standalone and mini-grid system: An empirical study in a costal village of Indian Sundarban

Solar PhotoVoltaic (SPV) based systems have been widely accepted technology for rural electrification in developing countries. The standalone SPV home lighting system has increasingly been popular among rural households, while SPV mini-grid supply system is being promoted for rural electrification schemes. This study uses data from household survey to explore the impact of household characteristics on the preference for electrical energy from SPV systems. Econometric evidence shows heterogeneity in behavioural pattern for these two SPV systems. The flexibility in use and cost of systems might explain this difference. Household characteristics such as monthly household income, household size, occupational status of household head, number of room and type of house significantly influence household’s decision for SPV standalone home lighting systems. For SPV mini-grid supply household’s income and monthly expenditure on kerosene are significant predictors. The result reported in this paper might be a valuable input for policy makers to frame right policy mix with regard to provide subsidy on rural electrification programmes.     

Organizing prosumers into electricity trading communities: Costs to attain electricity transfer limitations and self‐sufficiency goals

Among household electricity end users, there is growing interest in local renewable electricity generation and energy independence. Community‐based and neighborhood energy projects, where consumers and prosumers of electricity trade their energy locally in a peer‐to‐peer system, have started to emerge in different parts of the world. This study investigates and compares the costs incurred by individual households and households organized in electricity trading communities in seeking to attain greater independence from the centralized electricity system. This independence is investigated with respect to: (i) the potential to reduce the electricity transfer capacity to and from the centralized system and (ii) the potential to increase self‐sufficiency. An optimization model is designed to analyze the investment and operation of residential photovoltaic battery systems. The model is then applied to different cases in a region of southern Sweden for year 2030. Utilizing measured electricity demand data for Swedish households, we show that with a reduced electricity transfer capacity to the centralized system, already a community of five residential prosumers can supply the household demand at lower cost than can prosumers acting individually. Grouping of residential prosumers in an electricity trading community confers greater benefits under conditions with a reduced electricity transfer capacity than when the goal is to become electricity self‐sufficient. It is important to consider the local utilization of photovoltaic‐generated electricity and its effect on the net trading pattern (to and from the centralized system) when discussing the impact on the electricity system of a high percentage of prosumers.     

Application of superconductive magnetic energy storage in anasynchronous link between power systems

The concept that superconductive magnetic energy storage (SMES) can be incorporated into a back-to-back DC link is introduced. With an SMES-DC link, an SMES system can be shared between several neighboring power systems. This results in better economics for SMES usage for each participating power system. In addition to SMES operation, an SMES-DC link also allows asynchronous connection and interchange of power between the interconnected systems. It is demonstrated that an SMES-DC link can achieve significant economic benefits over pure power interchange or SMES operation alone. The basic principle of an SMES-DC link, which is able to interconnect any number of neighboring power systems with a single SMES unit, and various interconnected system operation modes are presented. A battery-DC link is discussed and compared with the SMES-DC link     

Analysing socioeconomic diversity and scaling effects on residential electricity load profiles in the context of low carbon technology uptake

Adequately accounting for interactions between Low Carbon Technologies (LCTs) at the building level and the overarching energy system means capturing the granularity associated with decentralised heat and power supply in residential buildings. The approach presented here adds novelty in terms of a realistic socioeconomic differentiation by employing dwelling/household archetypes (DHAs) and neighbourhood clusters at the Output Area (OA) level. These archetypes are combined with a mixed integer linear program (MILP) to generate optimum (minimum cost) technology configurations and operation schedules. Even in the baseline case, without any LCT penetration, a substantial deviation from the standard load profile (SLP) is encountered, suggesting that for some neighbourhoods this profile is not appropriate. With the application of LCTs, including heat pumps, micro-CHP and photovoltaic (PV), this effect is much stronger, including more negative residual load, more variability, and higher ramps with increased LCT penetration, and crucially different between neighbourhood clusters. The main policy implication of the study is the importance of understanding electrical load profiles at the neighbourhood level, because of the consequences they have for investment in the overarching energy system, including transmission and distribution infrastructure, and centralised generation plant. Further work should focus on attaining a superior socioeconomic differentiation between households.     

5G通信基站节能供电系统运行控制策略研究

5G通信基站耗电量较大,引入分布式供电(DG)单元能对其进行一定的电能补充,但DG单元易受气象条件的影响,导致通信基站节能供电系统运行不稳定。为提高通信基站节能供电系统运行的稳定性,提出了一种基于直流母线电压信息自动切换的控制策略,系统内各单元可根据当前直流母线电压状态实现并网、孤岛模式的无缝切换。仿真结果表明,所提控制策略能够维持通信基站节能供电系统稳定运行,实现不间断供电,为未来设计节能型5G通信基站供电系统提供了一定理论依据。     

Managing the future megacity: an appraisal of knowledge about energy challenges and energy-saving attitudes among households in Dhaka

Energy saving is now an important household priority in Dhaka. Energy crisis especially electricity crisis is one of the most important sufferings of the residents in Dhaka. As tackling such immense problem requires initiatives from both government and household ends, this study focuses on appraising the energy saving attitudes of the households in Dhaka to help government in designing and implementing appropriate policy options. Using a sample of 400 households, surveyed in a cross-section of locations in Dhaka, the study reveals that there is an encouraging level of homogeneous knowledge about energy challenges and various dimensions of energy-saving attitudes. Furthermore, the price of the energy-saving appliances is considered as one of the most important impediments in achieving a more comprehensive energy-saving response among the household is quite well match with the socioeconomic characteristics of the majority of the residents in Dhaka.     

Effectiveness of an energy-consumption information system for residential buildings

The authors have proposed a method of reducing the energy consumption in residential buildings by providing household members with information on energy consumptions in their own houses. An on-line interactive “energy-consumption information system” that displays power consumptions of, at most, 18 different appliances, power and city-gas consumption of the whole house and room temperature, for the purpose of motivating energy-saving activities has been constructed and the effectiveness of the system investigated by installing it in 10 residential buildings. The experiment showed that energy-saving consciousness was raised and energy consumption was in fact reduced by the energy-saving activities of the household members. In this paper, the system is described in detail and the effectiveness of reducing energy-consumption of the whole house and for space heating will be discussed. Also the energy-saving activities in a certain household are shown by using load duration curves.     

Performance of residential fuel-cell-combined heat and power systems for various household types in Japan

A residential fuel-cell-combined heat and power (FC-CHP) system is considered a promising low-carbon technology that can reduce residential energy consumption and thus, achieve Japan's greenhouse gas (GHG) emissions reduction targets. However, to consider future directions for the systems' research and development, it is critical to understand the relationships between the performances of FC-CHP systems and residential energy demand profiles, which vary by household characteristic. This study evaluates the effects of applying city gas-fueled FC-CHP systems to Japanese households with different attributes. We compare total costs and GHG emissions for residential energy use between the FC-CHP systems and a conventional system. The economic performance results suggest that the basic PEMFC-CHP systems have an economic advantage only for four-person families with teenage children and further development efforts for low-output FC-CHP systems are required to enable various households save energy costs. The environmental evaluation results show that SOFC-CHP systems can drastically reduce GHG emissions from particularly small-sized households.     

Evaluating the reliability of distributed photovoltaic energy system and storage against household blackout

Distributed energy resources have been proven to be an effective and promising solution to enhance power system resilience and improve household-level reliability. In this paper, we propose a method to evaluate the reliability value of a photovoltaic (PV) energy system with a battery storage system (BSS) by considering the probability of grid outages causing household blackouts. Considering this reliability value, which is the economic profit and capital cost of PV+BSS, a simple formula is derived to calculate the optimal planning strategy. This strategy can provide household-level customers with a simple and straightforward expression for invested PV+BSS capacity. Case studies on 600 households located in eight zones of the US for the period of 2006 to 2015 demonstrate that adding the reliability value to economic profit allows households to invest in a larger PV+BSS and avoid loss of load caused by blackouts. Owing to the differences in blackout hours, households from the 8 zones express distinct willingness to install PV+BSS. The greater the probability of blackout, the greater revenue that household can get from the PV+BSS. The simulation example shows that the planning strategy obtained by proposed model has good economy in the actual operation and able to reduce the economic risk of power failure of the household users. This model can provide household with an easy and straightforward investment strategy of PV+BSS capacity.     

综合医院电气节能技术措施探讨

以降低A综合医院电能损耗为目的,通过测算空调系统、照明系统、医疗器械等用电负荷,分析医院电耗现状,探讨综合医院电气节能技术措施,有针对性采取更换LED照明、新增电梯电能回馈装置、更换新型节能变压器等措施。通过节电前后的数据对比分析,取得了较好的节电效果,为其他医院电气系统安全可靠、节能经济地运行提供参考。     

Contribution to the analysis of urban residential electrical energy demand in developing countries

Access of large segments of the population to electrical energy continues to be limited in the cities of developing countries where the standards pertaining to installed power and consumption are ill suited to the level of appliances owned by households. In this paper, a new evaluation method of residential users’ actual needs in electricity is proposed for Cameroon. The approach is based on the determination of the nature, number and power of the appliances, as well as their operation periods. The method used is a survey administered to a representative sample of households. A detailed questionnaire appraises specific consumption and installed power and is also used to construct the households’ load curve. The need for electrical energy varies according to the size of the city and, inside the city, to household income. The average power used per dwelling accounts for less than half the value prescribed by current norms. If implemented, the method would help optimise network investments and operation. The load curve obtained in the experiment shows that the peak output power is recorded in the evening and that household demand makes up most of this charge. The proposed strategy would reduce electrical energy costs, thus being of great potential interest for poor urban populations.     

A comprehensive energy solution for households employing a micro combined cooling,heating and power generation system

In recent years, micro combined cooling, heating and power generation (mCCHP) systems have attracted much attention in the energy demand side sector. The input energy of a mCCHP system is natural gas, while the outputs include heating, cooling and electricity energy. The mCCHP system is deemed as a possible solution for households with multiple energy demands. Given this background, a mCCHP based comprehensive energy solution for households is proposed in this paper. First, the mathematical model of a home energy hub (HEH) is presented to describe the inputs, outputs, conversion and consumption process of multiple energies in households. Then, electrical loads and thermal demands are classified and modeled in detail, and the coordination and complementation between electricity and natural gas are studied. Afterwards, the concept of thermal comfort is introduced and a robust optimization model for HEH is developed considering electricity price uncertainties. Finally, a household using a mCCHP as the energy conversion device is studied. The simulation results show that the comprehensive energy solution proposed in this work can realize multiple kinds of energy supplies for households with the minimized total energy cost.     

家用并网光伏系统仿真与运行性能计算

设计了一个家用并网光伏系统并计算其年发电量以研究其运行性能。在设定指定地点地理位置并导入气象数据,并根据屋顶可用面积决定光伏阵列的排布和逆变器参数后,利用PVsyst软件对光伏系统进行模拟,并计算发电量。结果表明：所设计的光伏系统年发电量约为7 114 kW·h,发电效率为75.1%。结合调查数据发现,该光伏系统发电量超过了当地用户年平均用电量;光伏系统一年中日输出电量的变化趋势显示,光伏系统发电量高峰时的日发电量均值可达35 kW·h以上;而光伏系统发电量低谷时的日发电量均值不足20 kW·h;光伏系统各项损失在理论发电量中的占比变化趋势显示,每年6、7、8月系统的光伏阵列损失最大,其原因是夏季气温升高使得光伏阵列运行性能受到影响。该光伏系统发电量可以满足一般家庭的用电需求,且用户可以参考光伏系统发电量的变化趋势选择合理的用电方式。     

Uncertainties in the design and operation of distributed energy resources: The case of micro-CHP systems

Large-scale diffusion of distributed energy resources (DERs) will have a profound impact on electricity infrastructure functioning: it will bring radical changes to the traditional model of generation and supply as well as to the business model of the energy industry. DERs comprise distributed power generators, distributed energy storages and controllable loads. There are, however, many uncertainties that influence the design and operation of DERs. This paper clarifies these uncertainties by proposing and applying a comprehensive framework for uncertainty analysis. We thereby adopt an integrated approach that considers not only the technical, but also the economic and institutional uncertainties. A delineation of the work is a focus on residential DERs and on micro-CHP systems specifically. After the proposed framework for uncertainty analysis is explained the uncertainties pertaining to the design and operation of residential DERs and micro-CHP systems are identified. In a case study system a selection of the uncertainties are quantitatively analysed. The case study system consists of a household that intelligently applies a micro-CHP unit in conjunction with energy storages and that interacts with its energy supplier. With a sensitivity analysis of the system model the salient impacts of the uncertainties on system behaviour and performance are enunciated.     

Modelling of electricity savings in the Danish households sector: from the energy system to the end-user

In this paper, we examine the value of investing in energy-efficient household appliances from both an energy system and end-user perspectives. We consider a set of appliance categories constituting the majority of the electricity consumption in the private household sector, and focus on the stock of products which need to be replaced. First, we look at the energy system and investigate whether investing in improved energy efficiency can compete with the cost of electricity supply from existing or new power plants. To assess the analysis, Balmorel, a linear optimization model for the heat and power sectors, has been extended in order to endogenously determine the best possible investments in more efficient home appliances. Second, we propose a method to relate the optimal energy system solution to the end-user choices by incorporating consumer behaviour and electricity price addition due to taxes. The model is non-exclusively tested on the Danish energy system under different scenarios. Computational experiments show that several energy efficiency measures in the household sector should be regarded as valuable investments (e.g. an efficient lighting system) while others would require some form of support to become profitable. The analysis quantifies energy and economic savings from the consumer side and reveals the impacts on the Danish power system and surrounding countries. Compared to a business-as-usual energy scenario, the end-user attains net economic savings in the range of 30–40 EUR per year, and the system can benefit of an annual electricity demand reduction of 140–150 GWh. The paper enriches the existing literature about energy efficiency modelling in households, contributing with novel models, methods, and findings related to the Danish case.