Levelized cost of storage — Introducing novel metrics

The increasing share of variable renewable generation capacity leads to a growing interest in electricity storage technologies and a summarizing cost metric to analyze the economic viability of such electricity storage units. For conventional generation technologies, the levelized cost of electricity (LCOE) is a well-known metric. In the context of electricity storage however, such LCOE-like metrics are only limitedly applicable as the finite energy storage capacity can limit the charge and discharge scheduling decisions of the storage operator. In addition, the “fuel”, i.e., charged electricity, and “generated electricity”, i.e., discharged electricity, is one and the same commodity which provides the opportunity to use an adapted levelized cost metric. This work analyzes three different levelized cost metrics and their application to electricity storage units used for electric energy arbitrage. The strengths and shortcomings of these storage cost metrics are analyzed in order to determine how they can be applied correctly. This analysis results in the following recommendations. First, it is recommended to use a levelized cost metric in combination with an analysis of a representative price profile upon which the storage operator will act. This allows a more accurate estimation of the number of charging and discharging hours and the associated charging cost and discharging revenue, given the energy storage capacity constraints of the storage unit. Second, when a number of different representative price profiles, hence with different charging costs, is available, it is recommended to use a cost metric which is independent of the charging cost as this single metric can be compared to each price profile, thereby facilitating the interpretation of the results. The results and conclusions from this work provide a framework on how to use levelized cost metrics in the context of electricity storage. Such metrics may help policy makers and investors in prioritizing energy storage investment decisions.     

Study on key parameters design and economic evaluation of the electric heating and solid sensible heat thermal storage device

电制热固体储热系统对可再生能源消纳、能源清洁化利用具有重要意义。电制热固体储热装置的关键参数设计以及经济性分析是提高经济效益的重要手段。因此,本文提出了电制热固体储热装置投资运行费用计算方法。通过对比不同供暖方式所需费用分析了电制热固体储热装置的经济性。同时研究了谷电利用系数对电制热固体储热装置经济性的影响。最后,采用案例分析验证本文所提经济性评估方法的合理性与正确性。本文的研究内容为用户对电制热固体储热装置的选择提供参考。     

Economic analysis of heating and cooling systems from the various perspectives: Application to EHP and GHP in Korea

Energy flow from the primary energy to the final energy use varies depending on which device is used for the heating and cooling energy service. This paper presents economic analyses of medium capacity space heating and cooling systems from three perspectives – primary energy, final consumer, and social cost perspective. From the analysis results of primary energy and final consumer perspective, electric heat pump (EHP) system is found to be superior to the gas engine driven heat pump (GHP) system for the energy consumption and cost-effectiveness due to its higher system efficiency. However, the result of social cost perspective shows the GHP system is superior to the EHP system considering incurred incremental electricity generation capacity construction cost and avoided gas storage tank construction cost due to a new installation of each system. And this paper suggests three analysis methodologies – the primary energy, final consumer, and social cost perspective – can be used for developing various measures and policies for integrated demand side management.     

The dynamics of integrated compressed air renewable energy systems

An integrated compressed air renewable energy system is defined here as one which harvests renewable energy directly in the form of compressed air and later converts that to the form of electrical power for transmission. There are two main motivations for considering such systems: firstly the lifetime cost per kW h exported has the potential to be substantially lower than the lifetime cost per kW h of a system generating electricity directly. Secondly these systems offer the intrinsic capability to store large amounts of energy in a very cost effective way. The only marginal costs associated with energy storage are those connected with providing some means for storing the compressed air and some means for managing heat. This paper describes an approach to simulating the performance of such systems including a controller to determine how much power to generate at a given time and it explains an appropriate rationale for the design of that controller. The simulations conducted indicate three remarkable performance measures. Specifically: (a) the marginal loss of energy associated with passing some energy through storage may be below 15% even with energy residency times in the order of months, (b) the marginal increase in total output electrical energy arising from integrating some solar heat capture can be as high as 60% of the captured solar heat for solar heat inputs up to 5% of total mechanical power and (c) the average value of the total power output may easily be raised by over 30% if power values continue to fluctuate at rates exhibited today and if the capacity for expansion-generation matches the peak input power of the primary (mechanical) energy harvesters.     

A novel latent heat storage for solar space heating systems: Refrigerant storage

This paper proposes a novel latent heat storage which is applicable to solar space heating systems. The device is similar to an absorption refrigerator and stores liquid refrigerant which is subsequently evaporated to release the latent heat. It will recover the energy in a heat pump mode for application to solar space heating systems which are seen to be more cost effective—and hence to have a better market potential—than space cooling systems.     

Cost optimization of the design of CHCP (combined heat,cooling and power) systems under legal constraints

Combined heat, cooling and power (CHCP) systems are interesting for the supply of different energy services in urban districts and in large buildings. CHCP systems utilize a fuel's energy to a greater extent, because the cogenerated heat can be used for heating in winter as well as for cooling in summer with an absorption refrigerator. The use of thermal energy storage (TES) provides the additional advantage of covering variable thermal demands while the production system operates continuously at nominal conditions. Thus, energy supply systems integrating the technologies of cogeneration, absorption refrigeration and thermal storage can provide substantial benefits from economic, energetic and environmental viewpoints. In this paper an optimization model is developed, using mixed integer linear programming (MILP), to determine the preliminary design of CHCP systems with thermal storage. The objective function to be minimized is the total annual cost. Taking into account the legal constraints imposed on cogeneration systems in Spain, the optimization model is applied to design a system providing energy services for a set of buildings constituted of 5000 apartments located in the city of Zaragoza (Spain). The effect of legal constraints in the design and operation of CHCP systems is highlighted in this study.     

Dynamic modelling and multi-objective optimization of off-grid hybrid energy systems by using battery or hydrogen storage for different climates

The energy storage problem is an essential issue in renewable energy-based power systems. A comprehensive study is performed to evaluate off-grid hybrid renewable energy systems with a battery bank or a hydrogen system employed as the energy storage option. Dynamic modelling is proposed to see daily and seasonally changes in the system. The economic feasibility of the system and its environmental impacts are investigated in three locations. A multi-objective optimization method based on the Taguchi approach is employed to minimize both levelized cost of energy and the CO₂ emissions. Various weight factors were assigned to understand the response of different optimization targets. The results highlight that the hybridization of energy resources allows the annual emissions to be cut by 68–78% for battery storage, 84–90% for hydrogen storage, compared to a diesel-only system. Despite having higher costs, the systems with hydrogen storage can store energy in the long term; therefore, they have lower CO₂ emissions.     

A superstructure model of an isolated power supply system using renewable energy: Development and application to Jeju Island,Korea

In this study, we aim to develop a superstructure-based optimization model using mixed integer linear programming (MILP) to determine the optimal combination and sizing for a hybrid renewable energy system to be used in an isolated area. The developed model has a three-layered energy structure to reflect the current reality in which energy production and consumption sites are generally separate. A variety of economic factors, including distance between facilities and an installation area, are considered for a more accurate estimation of the total annualized cost. Two types of optimization models, i.e., with and without a battery, are proposed to evaluate the economic and technical effects of a storage device to resolve operation issues caused by intermittent resources. An application case study on Jeju Island, Korea, confirms that the proposed model is suitable for decision making at the planning stage of a renewable energy system.     

微网风电系统的储能火用模型与火用经济研究

微网风电系统加装储能装置联合运行时,存在多种异质能量的相互转化,因此对系统性能的有效评估较为困难。为了准确衡量风能在系统中的利用、转化、损失特性,文章基于[火用]经济学基本原理,建立微网风储系统[火用]平衡及[火用]成本守恒模型,并依据所建模型确定系统各单元[火用]效率;同时确立[火用]优化潜力、成本差及[火用]经济因子的系统性能评估指标,并对微网热力学特性及经济性进行有效分析。通过试验表明,该模型能够可靠地对微网风储系统能效及经济性进行评估,可指明系统[火用]效率极大化的优化目标。     

风电场含退役动力电池的混合储能系统容量优化配置

针对退役电池在风电场平抑功率波动场景的应用,提出一种考虑退役电池时间尺度的混合储能系统容量配置方法。首先分析退役电池和新电池储能的优势,并介绍储能系统的成本构成;然后建立以全寿命周期经济性最优、考虑退役动力电池充放电时间尺度的混合储能容量配置模型,线性化后可调用求解器求解获取储能容量配置结果;最后用风电场实际数据进行分析,验证容量配置方法的有效性,并分析风电场不同储能配置时长政策要求、退役动力电池不同时间尺度以及不同控制策略下的混合储能容量配置结果。     

Optimal insulation of solar heating system pipes and tanks

A compact and time-effective insulation design procedure for solar heating system piping and water-filled thermal storage tanks was developed. Recognizing the particular sensitivity of solar systems to cost, the economic aspect of the problem was treated by a comprehensive present-value life-cycle cost analysis. In the development of the method, a numerical sensitivity analysis was performed to determine the relative effects of all relevant independent variables (within their pertinent ranges) on piping and tank heat transfer coefficient values. For the acceptable error limits of ± 14% for pipes and ± 19% for tanks, it was found that one may assume that only the nominal pipe diameter (or tank diameter), the thermal conductivity of the insulation, and the insulation's thickness have an effect on the overall heat transfer coefficient. Based on this result, design graphs and tables are presented which can be used to determine the optimal insulation thickness and type, total annual heat losses, present-value annual costs of insulation and lost heat, and overall insulation R-values. The use of the method is illustrated by calculating all the above quantities for all piping and storage tanks for the University of Pennsylvania SolaRow House. The present method provided insulation thicknesses slightly greater than those obtained by the ETI technique.A major conclusion of the study is that the cost of insulation in solar systems is not insignificant (e.g., ~15% in SolaRow), and that heat losses through insulation could amount to an important percentage of the useful solar energy collected (e.g., 24% in SolaRow). This re-emphasizes the need for a careful design of insulation in solar systems.     

Lifetime prediction and sizing of lead-acid batteries for microgeneration storage applications

Existing models of microgeneration systems with integrated lead-acid battery storage are combined with a battery lifetime algorithm to evaluate and predict suitable sized lead-acid battery storage for onsite energy capture. Three onsite generation portfolios are considered: rooftop photovoltaic (2.5 kW), micro-wind turbine (1.5 kW) and micro combined heat and power (1 kW). With no embedded energy storage, the dwelling exports energy when the microgeneration system generates excess power leading to a high level of generated export throughout the year. The impact that the size of installed battery has on the proportion of the generated export that is reserved onsite, along with the annual energy discharged per year by the energy store is assessed. In addition, the lifetime algorithm is utilised to predict corresponding lifetimes for the different scenarios of onsite generation and storage size, with design tables developed for expected cost and weight of batteries given a predicted generated export and lifetime specification. The results can be used to indicate optimum size batteries for using storage with onsite generation for domestic applications. The model facilitates the choice of battery size to meet a particular criteria, whether that be optimising size, cost and lifetime, reducing grid export or attempting to be self-sufficient. Suitable battery sizes are found to have lifetimes of 2-4 years for high production microgeneration scenarios. However, this is also found to be highly variable, depending on chosen microgeneration scenario and battery size.     

Economic analysis for room-temperature sodium-ion battery technologies

随着人们对新能源和环境的重视,锂离子电池的应用逐渐扩展到电动汽车和储能领域,这势必增加了锂资源的使用和消耗.在锂资源日益紧缺的形势下,锂离子电池原材料成本必然难以降低,使其在大规模储能中的应用受到限制.而室温钠离子电池由于其资源丰富,成本低,能量转换效率高,循环寿命长,维护费用低等诸多优势已成为目前研究的热点.本文对室温钠离子电池材料选择和原材料成本进行了分析,并与当前常用的锂离子电池体系进行对比,从电池经济性角度表明室温钠离子电池是大规模储能领域的优秀备选电池.     

Economical assessment of a wind–hydrogen energy system using WindHyGen software

This paper considers the problem of analyzing the economical feasibility of a wind–hydrogen energy storage and transformation system. Energy systems based on certain renewable sources as wind power, have the drawback of random input making them a non-reliable supplier of energy. Regulation of output energy requires the introduction of new equipment with the capacity to store it. We have chosen the hydrogen as an energy storage system due to its versatility. The advantage of these energy storage systems is that the energy can be used (sold) when the demand for energy rises, and needs (prices) therefore are higher. There are two disadvantages: (a) the cost of the new equipment and (b) energy loss due to inefficiencies in the transformation processes. In this research we develop a simulation model to aid in the economic assessment of this type of energy systems, which also integrates an optimization phase to simulate optimal management policies. Finally we analyze a wind–hydrogen farm in order to determine its economical viability compared to current wind farms.     

Optimization of operational cost for a grid-supporting PV system with battery storage

Coupling an energy storage to a photovoltaic (PV) system not only increases the self-consumption but also solves the over-voltage issues if the cycling of the storage is properly controlled. Whatever the application the storage is used for, the primary concern of the system owner is to maximize the profits. Therefore, this paper addresses an energy management system for a PV system coupled with battery energy storage, which maximizes the daily economic benefits while curtailing the power injection to the grid in such a way that helps to mitigate over-voltage problems caused by reverse power flow. A time dependent grid feed-in limit is proposed achieve this objective. The daily operational cost that includes the energy cost and the battery degradation cost is considered as the objective function. The non-linear constrained optimization problem is solved using dynamic programming. The analyses are made to investigate the economic benefits of charging the battery from the grid. It is found that there is a possibility for these systems for participating in load-levelling if batteries are charged from the PV system. In order for that to be feasible, the peak-hour sell-back price for the energy from storage should be higher than the off-peak utility electricity price.     

飞轮储能在区域电网中的调频应用及经济性分析

介绍了飞轮储能在区域电网的应用现状,提出了飞轮储能用于电网调频的经济性分析评估方法。通过美国加利福尼亚州的工程实例详细分析了飞轮储能在电网调频中的效益投资情况。结果表明,飞轮储能的投资效益比接近1,具有良好的投资回报价值;在大规模商业化应用后,收益投资比可达1．97。     

A novel multicriteria sustainability investigation of energy storage systems

Affordable, clean, efficient, flexible, and reliable energy storage is an important component of sustainable energy systems. There are several studies in the literature concentrating on improving the sustainability performance of energy storage systems from economic and technical perspectives. However, a comprehensive performance investigation of energy storage systems that take economic, environmental, social, and technical criteria into account is still needed. For that reason, in the present study, it is aimed to perform a complete assessment and analysis of the sustainability of energy storage systems for residential applications in communities and cities. Pumped hydro, conventional batteries, high‐temperature batteries, flow batteries, and hydrogen are the selected energy storage systems. In order to handle the vagueness and ambiguity during the assessment and to eliminate the perceived hesitancy in the decision makers' preferences, an innovative method, a hybrid hesitant fuzzy multicriteria decision‐making (MCDM) methodology composed of hesitant fuzzy analytic hierarchy process (HFAHP) and hesitant fuzzy technique for order preference by similarity to ideal solution (HFTOPSIS), is utilized to assess the sustainability of the selected systems. In this study, four different performance criteria: economic (power cost and energy cost), environmental (pollutant emissions, area requirement, wastewater quality, and solid waste production), social (safety, accessibility, ease of use, and public acceptance), and technical (efficiency, storage capacity, cycling limit, and performance degradation) are taken into consideration. The performance evaluation results indicate that technical performance has the highest influence and social performance has the lowest influence when evaluating the sustainability of the selected energy storage systems. And hydrogen has the highest sustainability performance compared with the other selected energy storage options.     

考虑运行经济成本的风电场储能容量优化

储能技术作为一种新兴的调节风电功率输出方法,能够有效平抑风电出力波动.储能系统容量规划问题正成为重要的研究课题.以蓄电池作为研究对象,将放电深度和过放电现象对电池寿命的损伤折合为运行经济成本,同时考虑惩罚成本及固有成本,在确保风电出力尽可能接近期望出力的前提下,建立了以总经济成本最小为目标,以容量限制、功率限制及充放电次数限制为约束条件的储能容量优化模型,采用遗传算法求解目标函数.算例分析结果表明,该方法可以配置合理的储能容量,使得储能系统在平抑风电出力波动的同时使总经济成本降至最低,实现稳定性和经济性的相协调.     

Retailer energy management of electric energy by combining demand response and hydrogen storage systems,renewable sources and electric vehicles

The increasing pollution caused by conventional cars and the problems caused by the use of fossil fuels have drawn the attention of researchers and manufacturers to the design of cars that use clean fuels. Electric vehicles connected to the network have a significant impact on reducing environmental pollution and transportation costs, especially in big cities. The cost of supplying loads to subscribers in the distribution network also includes generation and transmission costs. These costs are directly related to the intelligence of the distribution network and the total amount of energy of electric vehicles. The contribution of each generation unit and each transmission line must be calculated to determine the generation and transmission costs. In this research, in order to maximize the profit of the parking lot owner, improve voltage drop and load factor, a comprehensive framework for optimal energy management in a parking lot is presented, which can provide a method to control the charging of electric vehicles, in addition to meeting the needs of their owners, only as a series of controllable loads that they need to receive electrical energy to charge their batteries. In the next step, considering the inherent characteristic of electric cars, i.e. having a battery, and looking at them as a series of storage resources that can return the electric energy in their battery to the grid if necessary, a method to simultaneously control their charging and discharging is provided. In the final step of the paper, it is assumed that hydrogen storage systems will also enter the circuit, and thus, a comprehensive method for energy management is proposed. Finally, the linearized model of demand response and the proposed scheme along with the modeling of hydrogen storage and electric vehicles are considered to be part of contribution to improve the operation and economic situation of the network.     

Heat pipe based cold energy storage systems for datacenter energy conservation

In the present paper, design and economics of the novel type of thermal control system for datacenter using heat pipe based cold energy storage has been proposed and discussed. Two types of cold energy storage system namely: ice storage system and cold water storage system are explained and sized for datacenter with heat output capacity of 8800 kW. Basically, the cold energy storage will help to reduce the chiller running time that will save electricity related cost and decrease greenhouse gas emissions resulting from the electricity generation from non-renewable sources. The proposed cold energy storage system can be retrofit or connected in the existing datacenter facilities without major design changes. Out of the two proposed systems, ice based cold energy storage system is mainly recommended for datacenters which are located in very cold locations and therefore can offer long term seasonal storage of cold energy within reasonable cost. One of the potential application domains for ice based cold energy storage system using heat pipes is the emergency backup system for datacenter. Water based cold energy storage system provides more compact size with short term storage (hours to days) and is potential for datacenters located in areas with yearly average temperature below the permissible cooling water temperature (∼25 °C). The aforesaid cold energy storage systems were sized on the basis of metrological conditions in Poughkeepsie, New York. As an outcome of the thermal and cost analysis, water based cold energy storage system with cooling capability to handle 60% of datacenter yearly heat load will provide an optimum system size with minimum payback period of 3.5 years. Water based cold energy storage system using heat pipes can be essentially used as precooler for chiller. Preliminary results obtained from the experimental system to test the capability of heat pipe based cold energy storage system have provided satisfactory outcomes and validated the proposed system concept.