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Energy storage is a cutting edge front for renewable and sustainable energy research. In fact, a massive exploitation of intermittent renewable sources, such as wind and sun, requires the introduction of effective mechanical energy storage systems. In this paper we introduce the concept of a trigenerative energy storage based on a compressed air system. The plant in study is a simplified design of the adiabatic compressed air energy storage and accumulates mechanical and thermal (both hot and cold) energy at the same time. We envisage the possibility to realize a relatively small size trigenerative compressed air energy storage to be placed close to the energy demand, according to the distributed generation paradigm. Here, we describe the plant concept and we identify all the relevant parameters influencing its thermodynamic behavior. Their effects are dissected through an accurate thermodynamic model. The most relevant technological issues, such as the guidelines for a proper choice of the compressor, expander and heat exchangers are also addressed. Our results show that T-CAES may have an interesting potential as a distributed system that combines electricity storage with heat and cooling energy production. We also show that the performances are significantly influenced by some operating and design parameters, whose feasibility in real applications must be considered. [ABSTRACT FROM AUTHOR]

By storing hydrogen in an oil-based slurry with powdered magnesium hydride, inexpensive and safe hydrogen storage can he realized. This paper describes the characteristics and benefits of cycling hydrogen in and out of magnesium hydride slurry. An application of magnesium hydride slurry in a baseload wind power system is discussed. It concludes that a 150MW baseload wind power system can produce an internal rate of return (IRR) of 10% with an electric price of $0.088/kWh. The costs and performance characteristics of this power plant are described. [ABSTRACT FROM AUTHOR]

The first transport vehicles were the sleighs and the only power available was human. Later on, certain animals were domesticated and the wheel invented they become the main source of energy for different civil and military applications. When other forms of energy were discovered, like wind and hydro, available free of charge, these replaced the animal power in many applications including in transport. 200 years ago, the steam power produced by burning coal took their role. Later on, there were developed motors with internal combustion for cars, Diesel rail locomotives and big ships were built. In order to make vehicles more efficient with higher performances and less pollutant, hybrid mechanical and electrical solutions or plug-in were developed with lithium based on batteries. The future of storage is practically based on nanotechnologies, High Temperature Superconductors for excitation of large power electrical machines and for electrical energy transfer. The suggested new sources of energy based on direct conversion of water in hydrogen and oxygen by sun radiation and nuclear fission of deuterium and tritium initiated by powerful lasers, sounds very much science fiction today, but may be a solution in several years on. [ABSTRACT FROM AUTHOR]

Climate change considerations stimulate to switch to wider use of renewable energy sources for electricity generation. However in case of solar and wind energy, the use is burdened with non-regular generation trends. Electricity storage technologies, for example heat pumps, are observed as a potential technology to solve the non-regularity issue of the renewable electricity generation, reduction of fossil fuel generated greenhouse gas emissions and increasing the share of renewables in energy production sector. The process of heat pumps integration in district heating system can differ for each heating and electricity production and distribution system.Energy system's behaviour types plays significant role while performing an integration efficiency analysis. The present paper analyses the possibilities of integration of heat pumps in district heating systems of Latvia, Estonia and Lithuania as a tool for accumulation of renewable resources generated electricity. [ABSTRACT FROM AUTHOR]

In the present paper, a new approach to energy resources management in a residential microgrid is proposed and evaluated in simulation, using energy and economic criteria. Its aim is to improve energy efficiency as well as interaction with the electricity grid. So, a grid-connected building located in Perpignan (south of France) and equipped with energy production and storage systems has been modelled using the TRNSYS software. We designed and managed these systems optimally and highlighted configurations that promote self-consumption of energy. In addition, the negative impact on the grid of local power generation (related to both energy injection and extraction) is minimized. The combination of photovoltaic solar panels and a vertical-axis wind turbine as a viable energy mix option for residential buildings in Southern France has also been evaluated. At least, we appraised the way electricity storage impacts on performance as well as the savings one can achieve by shifting some domestic loads from on-peak to off-peak periods. [ABSTRACT FROM AUTHOR]

Meeting time-varying peak demand poses a key challenge to the U.S. electricity system. Building-based electricity storage – to enable demand response (DR) without curtailing actual appliance usage – offers potential benefits of lower electricity production cost, higher grid reliability, and more flexibility to integrate renewables. DR tariffs are currently available in the U.S. but building-based storage is still underutilized due to insufficiently understood cost-effectiveness and dispatch strategies. Whether DR schemes can yield a profit for building operators (i.e., reduction in electricity bill that exceeds levelized storage cost) and which particular storage technology yields the highest profit is yet to be answered. This study aims to evaluate the economics of providing peak shaving DR under a realistic tariff (Con Edison, New York), using a range of storage technologies (conventional and advanced batteries, flywheel, magnetic storage, pumped hydro, compressed air, and capacitors). An agent-based stochastic model is used to randomly generate appliance-level demand profiles for an average U.S. household. We first introduce a levelized storage cost model which is based on a total-energy-throughput lifetime. We then develop a storage dispatch strategy which optimizes the storage capacity and the demand limit on the grid. We find that (i) several storage technologies provide profitable DR; (ii) annual profit from such DR can range from 1% to 39% of the household’s non-DR electricity bill; (iii) allowing occasional breaches of the intended demand limit increases profit; and (iv) a dispatch strategy that accounts for demand variations across seasons increases profit further. We expect that a more advanced dispatch strategy with embedded weather forecasting capability could yield even higher profit. [ABSTRACT FROM AUTHOR]

This paper examines the potential role for Power to Gas (P2G) as applied to an island energy system with high levels of renewable electricity penetration. P2G systems require both a supply of green electricity and a source of CO 2 . Cheap electricity is essential for a financially sustainable P2G system. Using a PLEXOS model it was determined that deploying 50 MW e of P2G capacity on the 2030 Irish electrical grid may reduce absolute levels of curtailed wind by 5% compared to the base case. CO 2 capture is expensive. The cheapest method of sourcing CO 2 for a P2G system is to employ a methanation process whereby biogas from anaerobic digestion is mixed with hydrogen from surplus electricity. Anaerobic digestion in Ireland has a potential to produce biomethane to a level of 10.2% of energy in transport (19.2 PJ/a). The potential CO 2 resource from anaerobic digestion could allow for a further 8.9% of energy in transport (16.6 PJ/a) from P2G production. An optimal model is proposed including for co-location of a biogas system with a P2G system. The model includes for demand-driven biogas concepts allowing electrical grid balancing and the supply of gaseous transportation fuel. Biofuel obligation certificates allows for a financially viable industry. [ABSTRACT FROM AUTHOR]

Increasing the proportion of electricity produced by intermittent renewable energy sources raises impact on power systems. The goal of the study was to evaluate the benefits from “vehicle-to-grid” (V2G) systems for integration of intermittent sources using the Latvian power system as the case. The energy system analysis tool “EnergyPLAN” was used for modeling of scenarios. The results show that the V2G system could provide an important benefit for “peak shaving” by supplying up to 700 MW of electric capacity back to grid, which is about 11% of the capacity of all the V2G cars connected to the grid. The potential reduction of CO 2 by V2G systems is about 100 kg CO 2 per one passenger car. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess the potential of biogas plants in Latvia to balance power supply from wind power plants. Several balancing options are discussed in the paper, including demand driven biogas production with biogas storage, flexible biogas production, and the use of biogas in Power-to-Gas systems. Theoretical surplus wind energy accumulation potential using operational biogas plants in Latvia has been calculated. Results show that 83.75 MW of surplus wind power capacity in Latvia could be theoretically balanced by using dynamic biogas upgrading in biogas CHP plants in Latvia. That would allow balancing 3.6% of surplus wind electricity in a 100% wind energy scenario. [ABSTRACT FROM AUTHOR]

In this paper, a storage system has been considered to be added to a private electricity facility in order to reduce the electricity bill. This kind of system could make sense with a time-of-use (TOU) tariff (with two or three periods of different electricity price) or a real-time pricing (RTP) tariff (which can vary hourly depending on wholesale market), where each day, electricity is bought from the AC grid during off-peak hours (at low price) to store energy, and during on-peak hours (at high price), the storage supplies the whole load or a part, avoiding the purchase of expensive electricity from the AC grid. A new optimisation model to obtain the best storage size and control of the charge–discharge process under RTP tariff has been developed, minimising the net present cost of the system. This methodology allows the electricity consumer to evaluate the profitability of adding storage. A case study of battery storage with a hypothetical hourly RTP tariff based on the Spanish electricity market pool of 2013 is shown. Considering the cost of batteries per kW h cycled expected in the near future (0.045 €/kW h cycled ), even the optimal storage size with the optimal control is not profitable compared to the system without storage. A much lower battery cost (0.0225 €/kW h cycled ) would be needed so that the storage system could be economically profitable. Considering a stretched RTP hourly pricing tariff (hourly prices higher than the average of each day multiplied by 1.3 and the lower ones by 0.7), the storage system with the costs expected in the near future (0.045 €/kW h cycled ) is profitable. We conclude that an hourly tariff that takes the base of the Spanish electricity market pool is not adequate to stimulate this technology, as the difference between maximum and minimum prices during the day is too low to compensate the capital cost plus replacement, operation, and maintenance of the storage system. In other countries, with much higher difference between minimum and maximum electricity price of the day, present battery cost could make it profitable. [ABSTRACT FROM AUTHOR]

Large-scale deployment of intermittent renewable energy (namely wind energy and solar PV) may entail new challenges in power systems and more volatility in power prices in liberalized electricity markets. Energy storage can diminish this imbalance, relieving the grid congestion, and promoting distributed generation. The economic implications of grid-scale electrical energy storage technologies are however obscure for the experts, power grid operators, regulators, and power producers. A meticulous techno-economic or cost-benefit analysis of electricity storage systems requires consistent, updated cost data and a holistic cost analysis framework. To this end, this study critically examines the existing literature in the analysis of life cycle costs of utility-scale electricity storage systems, providing an updated database for the cost elements (capital costs, operational and maintenance costs, and replacement costs). Moreover, life cycle costs and levelized cost of electricity delivered by electrical energy storage is analyzed, employing Monte Carlo method to consider uncertainties. The examined energy storage technologies include pumped hydropower storage, compressed air energy storage (CAES), flywheel, electrochemical batteries (e.g. lead–acid, NaS, Li-ion, and Ni–Cd), flow batteries (e.g. vanadium-redox), superconducting magnetic energy storage, supercapacitors, and hydrogen energy storage (power to gas technologies). The results illustrate the economy of different storage systems for three main applications: bulk energy storage, T&D support services, and frequency regulation. [ABSTRACT FROM AUTHOR]

The exploration of future energy system trajectories needs to be based on long-term scenarios, which in turn requires using long-term modelling tools. Introducing a strong decarbonisation constraint, for instance, profoundly modifies the power sector, which is impacted by increasing shares of variable renewable energy sources. Long-term modelling tools working on different assumptions increasingly factor in these impacts, the assessment of which requires a clear description and categorization of the technical and economic choices for representing the tools in question. A new typology based on a literature review is presented for both power sector models and long-term models of the energy system. New comparing criteria focussing on the power sector's components are put forward, such as electricity storage and grid. An analysis carried out by means of this categorization on five chosen models shows that, up until now, energy modelling tools and power system tools have been designed to meet separate objectives and have not combined their advantages. [ABSTRACT FROM AUTHOR]

This paper compares various flexibility options to support renewable energy integration across the energy transition using energy system modelling. We analyse new flexibility assets such as electricity storage, heat pumps, demand-side response with existing wet appliances, electric boilers for domestic hot water and distribution grid expansion, along with energy efficiency measures in electrical appliances and building retrofitting. We propose an open-source sector coupling model (GRIMSEL-FLEX) to minimise, from a social planner perspective, the total cost of the energy system for electricity and residential heating supply in Switzerland, including various types of consumers and urban settings. We find relevant feedback mechanisms among various flexibility options. Firstly, electric boilers have a larger flexibility potential than demand-side response with wet appliances since they reduce storage investments by more than 26% by 2050 (only 12% for demand-side response). Secondly, 34% more electricity storage is needed if heat pumps replace all fossil-based heating and 80% to replace all heating systems entirely. Thirdly, we find a shift in the operation of heat pumps, electric boilers and wet appliances from night to midday, resulting in larger photovoltaic deployment (22%–66% for the residential sector). Finally, electricity storage capacity induced by heat pump deployment is highly dependent on the retrofitting rate. With 1% per annum, 86% of storage investments can be avoided and it can be counterbalanced with a high retrofitting rate of 2% per annum. • Open-source sector coupling modelling framework with different flexibility assets. • Optimal DHW boilers operation and DSR can save up to 40% of storage investments. • 34%–80% more electricity storage is needed to support larger heat pump deployment. • Retrofitting buildings reduces storage needs by 86%. • Flexible heat pumps, DHW boilers and appliances increase PV deployment by 22%–66%. [ABSTRACT FROM AUTHOR]

During the past decade governments across Europe have set in place a series ofprogrammes to expand investment on grid-connected solar power technology, mostespecially Photovoltaics (PV). Recently most of these programmes have beenrolled back, in face of rapidly declining costs. Using a simple model thisarticle shows that basic PV electricity costs are presently below 0.10 €/kWh inlarge swaths of the continent, entering levels where previously only nuclear andfossil fired electricity where found. Due to the scalable nature of PV, manyhouseholds in Europe are now able to produce their own electricity at a costconsiderably lower that the rates demanded by grid utilities. If governmentsproceed with the complete roll back of fixed electricity rates to PV suppliersthe most likely result is a shift to off-the-grid systems. Long term thistrend presents serious challenges to utilities and traditional electricitysuppliers, putting at stake the traditional electricity market framework.

Several of the emerging technologies for electricity storage are based on some form of thermal energy storage (TES). Examples include liquid air energy storage, pumped heat energy storage and, at least in part, advanced adiabatic compressed air energy storage. Compared to other large-scale storage methods, TES benefits from relatively high energy densities, which should translate into a low cost per MW h of storage capacity and a small installation footprint. TES is also free from the geographic constraints that apply to hydro storage schemes. TES concepts for electricity storage rely on either a heat pump or refrigeration cycle during the charging phase to create a hot or a cold storage space (the thermal stores), or in some cases both. During discharge, the thermal stores are depleted by reversing the cycle such that it acts as a heat engine. The present paper is concerned with a form of TES that has both hot and cold packed-bed thermal stores, and for which the heat pump and heat engine are based on a reciprocating Joule cycle, with argon as the working fluid. A thermodynamic analysis is presented based on traditional cycle calculations coupled with a Schumann-style model of the packed beds. Particular attention is paid to the various loss-generating mechanisms and their effect on roundtrip efficiency and storage density. A parametric study is first presented that examines the sensitivity of results to assumed values of the various loss factors and demonstrates the rather complex influence of the numerous design variables. Results of an optimisation study are then given in the form of trade-off surfaces for roundtrip efficiency, energy density and power density. The optimised designs show a relatively flat efficiency vs. energy density trade-off, so high storage density can be attained with only a modest efficiency penalty. After optimisation, losses due to pressure drop and irreversible heat transfer in the thermal reservoirs are only a few percent, so round-trip efficiency is governed mainly by the efficiency of the compression and expansion processes: overall roundtrip efficiencies approaching those for pumped hydro schemes might be achievable whilst simultaneously attaining energy storage densities of around 200 MJ m –3 , but this is contingent upon attaining compression and expansion efficiencies for the reciprocating devices that have yet to be proven. [ABSTRACT FROM AUTHOR]

Recent advancements in battery technologies may make bulk electricity storage economically feasible. We analyze the value of two electrochemical storage technologies and traditional pumped hydropower storage in the 2010 PJM day-ahead energy market, using a reduced-form unit commitment model. We find that large-scale storage would increase overall social welfare in PJM. However, the annualized capital costs of storage would exceed social welfare gains. Consumers would save up to $4 billion annually due to reduced peak prices and reduced reliance on expensive peaking generators. These savings are equivalent to $$\sim $$ 10% of sales in the PJM day-ahead energy market. Savings come largely at the expense of generator surplus. Existing market mechanisms are insufficient to encourage the socially optimal quantity of storage. Storage reduces the profitability of generators and the need for peaking generation capacity. Storage modestly increases emissions of CO $$_{2}$$ and other pollutants in a system with 2010 PJM characteristics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Storage-based demand response (loadshifting) is underutilized in residential sector. [•] Economics (arbitrage savings versus equipment cost) are not well understood. [•] Stochastic demand models and real-life tariffs can illuminate economic viability. [•] A range of available storage options provide economically viable DR. [•] Daily/seasonal stochastic demand variations crucial to understanding optimum capacity. [ABSTRACT FROM AUTHOR]

Highlights: [•] A superstructure-based model is developed for hybrid power system design. [•] The model considers various power losses occurring in hybrid power systems. [•] The model locates rigorous outsourced electricity targets. [•] The model determines the minimum electricity storage capacity required. [•] Three literature case studies are solved to demonstrate the use of the model. [Copyright &y& Elsevier]

Highlights: [•] The research proposed an autonomous smart charging framework for achieving consumer savings. [•] The proposed demand side management scheme incorporates both appliance scheduling and energy storage. [•] The concept of load clustering is introduced for grouping the loads within the same time period. [Copyright &y& Elsevier]

Abstract: Halotechnics, Inc. is developing an energy storage system utilizing a low melting point molten glass as the heat transfer and thermal storage material. This work is supported under a grant from the Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E). Advanced oxide glasses promise a potential breakthrough as a low cost, earth abundant, and stable thermal storage material. The system and new glass material will enable grid scale electricity storage at a fraction of the cost of batteries by integrating the thermal storage with a large heat pump device. Halotechnics is combining its proven expertise in combinatorial chemistry with advanced techniques for handling molten glass to design and build a two-tank thermal energy storage system. This system, operating at a high temperature of 1200°C and a low temperature of 400°C, will demonstrate sensible heat thermal energy storage using a uniquely formulated oxide glass. Our molten glass thermal storage material has the potential to significantly reduce thermal storage costs once developed and deployed at commercial scale. Thermal storage at the target temperature can be integrated with existing high temperature gas turbines that significantly increase efficiencies over today's steam turbine technology. This paper describes the development and selection of Halotechnics’ molten glass heat transfer fluids with some additional systems considerations. [Copyright &y& Elsevier]

Abstract: Following the 2011 Fukushima nuclear disaster, Japan is having to re-design its energy policy. With the danger of nuclear power in an earthquake-prone country exposed, renewable energies are being seen as a potential alternative. An assessment of the feasibility of a 100% renewable energy electricity system in Japan by the year 2030 was shown to be able to achieve a higher level of electricity resilience. The assessment is based on a simulation of the hourly future electricity production based on wind and solar meteorological data, that can cope with the estimated future hourly electricity demand in Japan for the year 2030. Such as system would use pump-up storage and electric batteries to balance the daily fluctuations in supply and demand, though the most important challenge of the system would be providing sufficient electricity to meet the summer demand peak. These findings have import implications at the policy making level, as it shows that the Japanese electricity generation system is technically able to increase the share of renewables up to 100%, guaranteeing a stable and reliable supply. [Copyright &y& Elsevier]

Abstract: The long history of the attempts to harness the power of the wind to generate electricity from the late 19th Century to the present day is outlined. The article discusses the way that the filing of patents has reflected the waxing and waning of enthusiasm for this free, but challenging, resource and the commercial realities of trying to convert an unpredictable and sometimes violent energy source into an economically viable contributor to the world's energy needs. The author opines that the key to unravelling this dichotomy may lie in the successful development of alternative, improved methods of storing electricity. [Copyright &y& Elsevier]

The continuous expansion of electricity generation from intermittent renewable energy sources has already changed the structure of electricity spot prices in Germany considerably. The common method to describe the spot price impacts of renewable energies is to shift the residual load along the merit-order curve of thermal power plants. But, this procedure is undefined if electricity is entirely generated from renewables and conventional power plants are turned off. This paper describes the general feasibility and future challenges to assess the spot price effects of price-elastic demand, substitutive demand and storage during times with surplus of generation from renewable energies. [ABSTRACT FROM AUTHOR]

Abstract: A possible way to calculate the cost-effectiveness of a photovoltaic system combined withelectric energy storage for a household is presented in this paper. To evaluatethe electricity costs, of the PV-battery system, the progression of the power demand and electricity production is evaluated and compared with cost and revenue of the resulting energy flow based on the electricity purchase prices and the EEG bonus for the feed in of renewable solar energy.The results show that solar applications with electricity storages can be profitable. But the high purchase price of the storage reduces the financial gain of the photovoltaic system. This paper also reveals that in the examined case redox flow batteries are the most promising technology and lead acid batteries are more lucrative than lithium ion batteries due to their lower initial costs. The calculation can predict the cost- effectiveness of a solar system with energy storage and therefore help to find the bestbattery sizefor a certain household. [Copyright &y& Elsevier]

Abstract: The ability to store excess intermittent renewable electricity is increasingly being seen as a key option for integrating large quantities of renewable capacity. However, intermittent energy sources currently account for very small amounts of total generation. Despite this fact, policymakers have begun implementing requirements that will dramatically increase the amount of bulk storage capacity. This paper examines the social benefits provided by bulk storage in the Texas electricity market, which has a large amount of renewable capacity relative to other states, but still quite limited renewable penetration. We focus on the impact of arbitraging electricity across time—a major service of bulk storage. Using current storage technologies, we demonstrate that electricity arbitrage will increase daily CO2 emissions by an average of 0.19 tons for each MWh stored. In addition, daily SO2 emissions will increase by an average of 1.89pounds/MWh while NO X emissions will fall by an average of 0.15pounds/MWh. [Copyright &y& Elsevier]

Abstract: Supported amine sorbents, prepared by impregnation of silica and polymer supports with tetraethylenepentamine (TEPA) and polyethylenimine (PEI) are evaluated for CO2 capture from atmospheric air. The effect of CO2 concentration and temperature is investigated. Regeneration was done at elevated temperatures up to 150°C and CO2 pressures up to 10bar. Two potentially attractive fields of application were identified: (1) production of CO2 enriched air using low regeneration temperatures and (2) the production of pure CO2 at elevated pressure. The latter option can be considered for geoengineering (via CCS) or for synthetic fuels from renewable energy and atmospheric CO2. [Copyright &y& Elsevier]

Efficient energy generation and consumption is a key factor to achieve ambitious goals related to air pollution and climate change. Modern electricity networks can include different kind of sources, such as renewable energy sources (RES). Then, hybrid systems are obtained by combining several sources and storage types in the new concept called microgrid (MG). In order to draw the best performance from these hybrid systems, a proper design and operation is essential. The purpose of this paper is to present a detailed report to properly undertake the building and management of a hydrogen MG in a simple and reliable way to continue struggling for more comprehension on the MG operation modes and prevent the reported failures in the literature. The experimental platform developed will provide the valuable knowledge and solid guidelines for future test centers and demonstration plants. The MG, located in Seville, Spain, incorporates an electrolyzer, metal hydride storage, fuel cell, and a battery bank as main components. The developed MG laboratory has been successfully tested. The results indicate reliable operation incorporating the hydrogen and batteries as energy storage. [ABSTRACT FROM PUBLISHER]