<strong>Energy</strong> Storage | Integrated approach<strong>Energy</strong> <strong>storage</strong> is a promising solution to maintain the power balance in the electricity gridof tomorrow. However, the adaptable and successful use of <strong>storage</strong> technologies requires anintegrated approach in the context of various value chains.Text Marjolein RoggenIn Europe, traditionally, it has been national grid operators thathave had the task of matching the (centralized) production ofelectricity to the fluctuating demand. In North America, marketoperators and vertically integrated utilities are responsible for thetask. Supply-side fluctuations are now complicating this task asmore renewable sources come on line and the growth forecastedin electric transport begins to materialize.We envision electricity <strong>storage</strong> becoming a vital component ofvarious value chains. We can be of service in the context ofvarious value chains like electricity, automotive andmanufacturing of <strong>storage</strong> systems, power electronics andtransport.Need and necessity<strong>Energy</strong> <strong>storage</strong> begins with a vision of how energy can best bestored for a particular purpose or purposes and on a particularscale. Large-scale energy <strong>storage</strong> may be the solution for dealingwith surpluses more efficiently, so that sources such as windenergy can be utilized to the full. Moreover, large-scale energy<strong>storage</strong> provides options to tackle instability in the grid, andcan play a role in generation load-balancing, power quality andsolving network control issues. Currently, we are investigatingthe value of and need for large-scale energy <strong>storage</strong> in theNetherlands within the European Union context. We execute arealistic simulation, based on our European market model thatcovers much of the European electricity grid. Previously, we8 | Global Contact - June 2009
developed plans for a large-scale energy <strong>storage</strong> ‘island’. Thisartificial island in the North Sea will have a <strong>storage</strong> capacity of20 GWh and could fulfill other ‘functions’ such as wind turbines,aquatic biomass, harbor facilities, and recreation.Benefits of fast-response<strong>storage</strong> devicesComply with regulationVarious groups have a stake in energy <strong>storage</strong>. Manufacturers,governments, regulators, energy producers, supply companies,grid operators, business users and homeowners all have theirown interests and responsibilities. Therefore, the appropriatenessof the existing legislative and regulatory framework needs tobe examined because problems in this area could hinderintroduction. Furthermore, if energy <strong>storage</strong> is to reach a state ofmass deployment, standardization will be essential. Standardsopen the way for mass production by numerous manufacturers,which in turn brings down costs and encourages product use.KEMA has a long tradition of providing all parties with advice andpractical assistance. We are represented on internationalstandardization committees and we have the capability toconduct low, medium and high-voltage tests.Cost reduction<strong>Energy</strong> can be stored in a variety of ways: batteries, flywheels,super capacitors, compressed air or pumped hydro-electric<strong>storage</strong>. The suitability of each technology for use in a givencontext depends on the amount of energy to be stored, the<strong>storage</strong> period and the charging and discharging times. Forsystems of more than 100 MW(h), only pumped <strong>storage</strong> andcompressed air energy <strong>storage</strong> (CEAS) are viable options. Bothsystems have a major geographical impact. For small-scaleelectricity <strong>storage</strong>, the redox flow battery is an attractivealternative. What matters most is optimizing the system as awhole at the lowest possible cost. Present day redox flowelectricity <strong>storage</strong> batteries consist of two large vessels ofelectrolyte in an acidic environment. A project has been set upwith the aim of finding a way of using oxygen from the air as areactant for the electrolyte. The expectation is that this thirdgeneration will cost only half as much as the present systems.Best suitedDeveloping a technology is one thing, putting it to practical use isanother. Which system best meets the requirements? Whatspecifications should be defined? Is the system better suited to aresidential neighborhood or a business park? We therefore set updemonstration projects to establish which systems work best inthe field. In the European Grow-Ders project two different mobile<strong>storage</strong> systems – a flywheel system and two Li-ion batteries –plus a combined rig will be evaluated on five sites using atechnical-economic assessment tool to determine optimal<strong>storage</strong> applications.The application of high-performance energy <strong>storage</strong> systems,such as advanced batteries, flywheels or compressed air foruse in electricity system regulation are all candidates to joinpumped hydro as viable <strong>storage</strong> solutions for bulk powersystems. This is particularly so in Independent System Operator(ISO) environments where there can be significant revenuepotential. However, the prospect of widespread use of <strong>storage</strong>for regulation raises a number of complex questions abouteffectiveness and economics. Therefore, we developed a detaileddynamic model of ISO operations, including traditionalgeneration resources, loads, real time energy markets,regulation, automatic generation control signals, and theinterconnected grid and other control areas. One overarchingfinding is that a fast-response <strong>storage</strong> device with anappropriate duration period (energy-to-power capacity ratio) isat least as effective as conventional generation for the supply ofregulating services. Under existing regulation protocols, durationof an hour or less was sufficient for regulation services.Furthermore, it established that the overall economics ofregulation revenues, net balancing energy revenues andpayments, including electrical losses in the battery system, werefavorable, and it demonstrated that a new 'fast regulationservice’ concept could be a win-win for system operators and<strong>storage</strong> operators. There may also be additional benefits, suchas decreasing dependence on traditional generation units, thusreducing adverse emission effects.SelectionAnother important field of interest is consultancy and modeling.For example, a US based utility commissioned us to make both<strong>storage</strong> component model and controler models to select <strong>storage</strong>systems for wind energy integration in the network. For anotherUS based utility we conducted a cost comparison study for aflywheel-based frequency-controlled power plant. With clean,dependable operation at a projected low cost, the flywheel powerplant has the potential to be an ideal alternative technology toprovide this critical ancillary service application.
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