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Dictionary

German Grid-Storage Technology

Energy storage is an important element in the production, transport and effective use of electricity. Till recently, most electricity has been generated in large power stations, and used on demand, and not stored. Now there is a great deal of interest in large-scale storage systems which can be a central part of the renewable energy revolution.

Energy storage is an important element in the production, transport and effective use of electricity. Till recently, most electricity has been generated in large power stations, and used on demand, and not stored. Now there is a great deal of interest in large-scale storage systems which can be a central part of the renewable energy revolution.

The six main categories of energy storage system are:

  • Pumped hydro-power
  • Switzerland is able to exploit its alpine location to pump water from low reservoirs to elevated reservoirs. This is done utilising electricity from wind power, or from imported electricity during periods when the price is low, allowing the water to be released to generate electricity during peak periods when the price is high.

  • Thermal
  • Excess energy can be stored in large masses or salt bodies. Electricity can be generated or the thermal energy used directly later.

  • Solid state batteries
  • Batteries took over the static charge storage Leyden jar when around 1800 Alessandro Volta discovered that two different metals separated by acid soaked parchment could release electricity - the pile battery. Today, batteries are a broad range of electrochemical storage systems, and included so-called 'advanced batteries' and capacitors (charged plates).

  • Flow batteries
  • Large-scale batteries can utilise tanks of fluid electrolytes. These can release energy quickly and efficiently.

  • Flywheels
  • An ancient technology revived to provide small to large-scale power on demand from rotational energy.

  • Compressed air energy storage
  • Energy can be stored by compressing air. By releasing it through a valve electricity can be generated.

Some terms and their definition used by power station operators and transmission system operators.

  • AAU
  • Assigned amount units

  • ACER
  • Agency for the cooperation of Energy Regulators

  • AEA
  • Annual emission allocations

  • Ancillary services
  • A range of services that System Operators (SOs) procure to respond to unexpected shocks, such as the sudden shutdown of a power plant, to guarantee system security in real-time. These include black-start capability (the ability to restart a grid following a blackout); frequency response (to maintain system frequency with automatic and very fast responses); fast reserve (which can provide additional energy when needed); the provision of reactive power and various other services (ENTSO-E, 2016).

  • AUS CPM
  • Australia Carbon Pricing Mechanism

  • AVR
  • Accreditation and Verification Regulation

  • Balancing markets
  • These operate after trading in the wholesale electricity market ends (after gate closure). In the balancing market, system operators manage a number of ancillary services to balance supply and demand in and near-real time (ENSTO-E, 2016).

  • Baseload, mid-merit, and peak-load generation
  • Different operation modes of generating plants based on a combination of technical and commercial factors (e.g. how economically the plant can run at different load factors). A power plant that runs all or most hours to meet minimum electricity needs is referred to as ‘baseload’. An operation that runs for short periods during times of high demand or resource scarcity is referred to as ‘peak load’, and an operation between baseload and peak that is adjusted to respond to fluctuating demand throughout the day is referred to as ‘mid-merit’ (Gottstein and Skillings, 2012).

  • Capacity
  • The maximum power that is available from the power sector or a power station at any point in time (NIC, 2016). Power stations do not operate at full capacity at all times, therefore generation is not the same as capacity. Capacity mechanisms (CM): A mechanism that rewards market participants for available capacity, on top of revenues generated by selling electricity in the wholesale market. These payments are meant to ensure security of supply by incentivising sufficient investment in new capacity or preventing the retirement of existing capacity. CMs take many forms and are sometimes referred to as capacity remuneration mechanisms (CRMs).

  • CCS
  • Carbon capture and storage

  • CDM
  • Clean Development Mechanism

  • CEN
  • Comité Européan de Normalisation

  • CENLEC
  • European Committee for Electrotechnical Standardisation

  • CER
  • Certified Emission Reduction credits

  • CITL
  • Community Independent Transaction Log

  • CMP
  • Conference of the Parties Serving as the Meeting of Parties to the Kyoto Protocol

  • CMP
  • Conference of the Parties

  • CSLF
  • Carbon Sequestration Leadership Forum

  • Demand response aggregators
  • Third party intermediaries or suppliers that reduce or shift demand on behalf of consumers in return for a compensatory payment, and that sell aggregated demand response products on the wholesale electricity market.

  • Demand-side response (DSR)
  • The intentional modification of electricity usage during system imbalances or in response to market prices (Hurley et al., 2013). Currently, demand side response consists mostly of industrial users that withdraw, lower or shift their demand when there is limited supply, or that allow system operators or third-party aggregators to do so in return for a compensatory payment. In addition, new products are increasingly available that enable households to reduce or shift their electricity consumption in response to price signals (OECD, 2015).

  • DENA
  • German energy Regulator

  • Dispatchable generation
  • Sources of electricity that can increase or decrease output on command. These include hydroelectricity, gas-fired and biomass power and some coal-fired generation. Some types of base load generation, such as nuclear power, cannot easily adjust output, and wind and solar power are also less controllable because of their variability.

  • DSO
  • distribution system operator

  • ECCP
  • European Climate Change Programme

  • ECJ
  • European Court of Justice

  • EEX
  • European Energy Exchange

  • EEZ
  • Exclusive Economic Zone

  • EIB
  • European Investment Bank

  • EIF
  • European Investment Fund

  • EITE
  • Energy Intensive Trade Exposed

  • Energy-only markets
  • These have no explicit mechanism for procuring or paying for capacity. Revenues are earned primarily by selling electricity on the wholesale electricity market (Hogan, 2012).

  • ENTSOE
  • European National transmission system operators for electricity

  • ENTSOG
  • European National transmission system operators for gas

  • ERU
  • Emission Reduction Units

  • ESD
  • Effort Sharing Decision

  • ETS
  • Emissions Trading Scheme

  • EU ETS
  • European Union Emissions Trading Scheme

  • EUTL
  • European Union Transaction Log

  • EWEA
  • European Wind Energy Assocation

  • FIT
  • Feed-in Tariff

  • Flexibility
  • The ability to modify supply and demand to the needs of the electricity system within a given timeframe. Gate closure: The moment when trading on the wholesale electricity market ends and the system operator takes on the role of ensuring a balance between demand and supply near or in real time in the balancing market (Keay-Bright, 2013).

  • GWP
  • Global Warming Potential

  • HCFCs
  • Hydrochlorofluorocarbons

  • HFCs
  • Hydrofluorocarbons

  • ICE
  • Intercontinental Exchange Futures Europe

  • IEA
  • International Energy Agency

  • IETA
  • International Emissions Trading Association

  • Interconnectors
  • Electricity cables that facilitate the physical linking of electricity systems, allowing electricity to flow across borders and sub-national electricity markets. This enables the exporting of electricity when supply is abundant, and the importing of electricity in times of system stress (Ofgem, 2016).

  • ITO
  • Independent Transmission Operator

  • Load factor
  • A measure of the average output of power stations relative to their installed capacity and, therefore, an indicator of capacity utilisation. It is expressed in the ratio of kilowatt-hours (kWh) produced in a given period, divided by the total possible kWh that could have been produced over the period.

  • Loss of load expectation (LOLE)
  • LOLE represents the number of hours or days per year in which it is estimated that supply will not meet demand. Merit-order principle: In wholesale electricity markets, bids for electricity generation are ranked (or ordered) from the lowest cost to the highest cost. Based on this ranking, electricity generation available at the lowest price is deployed first to meet demand needs.

  • Missing money problem
  • In energy-only markets, where market operators earn revenues primarily by selling electricity in the wholesale electricity market, government regulation or market failures may prevent prices from rising to sufficiently high levels (and frequently enough) for mid-merit and peaking plants to recover their fixed costs. Typically, this provides the rationale for the introduction of CMs.

  • Mothballing
  • The preservation of an electricity production facility, which remains idle. In other words, power plants are turned off but kept in working order so that production can be restored if needed.

  • NAP
  • National Allocation Plan

  • NEEAP
  • National Energy Effciency Allocation Plan

  • Non-dispatchable generation
  • Energy sources that cannot or can only limitedly be controlled in response to demand fluctuations or supply interruptions. This includes nuclear, run-of-river hydroelectric plants, solar, wave and wind power.

  • OFTO
  • offshore transmission owner

  • Operating reliability
  • The ability of the electricity system to ensure short-term power system reliability and to withstand unanticipated disturbances or imbalances. Balancing and ancillary services contribute to operating reliability. A reliable power system requires both resource adequacy and operating reliability (Keay-Bright, 2013; NERC, 2013).

  • PFCs
  • Perfluorocarbons

  • Power system reliability
  • A power system is reliable when it has both adequate resources to meet the highest levels of electricity consumption (resource adequacy) and is able to balance demand and supply in real-time, including in response to unexpected outages (operational quality).

  • Providers of capacity
  • Electricity market participants that either provide generating capacity or reduce electricity demand in response to supply shortages. Examples include owners of generation capacity, demand side response aggregators, consumers that actively manage their demand, interconnection, and storage.

  • Ramping
  • Ability of an energy resource (generation or demand) to change its power output or consumption up or down. The ramp rate is the speed of output/consumption change measured in MW per minute (Keay-Bright, 2013).

  • Reliability standard
  • In some countries the regulator or system operator sets a performance standard for the power system. Different metrics are used. Some European countries, for example, use a Loss of Load Expectation (LOLE) reliability standard, defined as the average number of hours a year for which it is estimated that supply will not meet demand (Keay-Bright, 2013).

  • RES
  • renewable energy source

  • REZ
  • renewable energy zone

  • Resource adequacy
  • The availability of sufficient generating and demand side capacity to ensure that forecasted electricity needs can be met.

  • RGGI
  • Regional Greenhouse Gas Initiative

  • SAVE
  • Specific Actions for Vigorous Energy Efficiency

  • Scarcity prices
  • High wholesale electricity prices that occur when electricity demand is high or when there is an imbalance between electricity demand and supply that leads to the deployment of higher-cost technologies. Scarcity prices allow providers of peaking capacity to recover their fixed costs and provide price signals for investments in new electricity generation or demand-side capacity when this is needed. In some countries, price caps prevent scarcity prices.

  • Scarcity value
  • The value of uninterrupted service to consumers often expressed as Value of Loss Load (VOLL) (Baker and Gottstein, 2013).

  • Security of Electricity Supply
  • the ability of the electrical power system to provide electricity to end-users with a specified level of continuity and quality in a sustainable manner (Eurelectric, 2006).

  • Smart technologies
  • Appliances and technology that automatically control the use of energy – often remotely (NIC, 2016).

  • SM-CG
  • Smart Meters Coordination Group

  • Storage
  • A wide range of technologies that can store electricity and can act as sources of demand at times of low demand and sources of supply when demand increases or when other sources reduce output (World Bank, 2015). While some storage technologies will store energy for minutes or hours, others can store electricity from night to day or across seasons. Examples include hydroelectric pumped storage, compressed air, water heaters, flywheels, the transformation of excess electricity into hydrogen, storage in the form of molten salts in concentrated solarpower plants and different battery technologies (flow, lead-acid, lithium-ion, sodium and zinc batteries).

  • Stranded assets
  • Assets that lose value or turn into liabilities before the end of their economic life. This can be caused by a number of risks, including technological innovation and market developments, but also climate and energy policy and regulation (adapted from HSBC, 2015). Examples of potential risks to the value of conventional electricity generation assets include competition from new technologies (such as renewable energy technologies or storage), falling demand for electricity or emission reduction policies.

  • Suppliers
  • Suppliers buy electricity from generators or in the wholesale electricity market and then sell it to firms and households in the retail market (NIC, 2016).

  • System peak
  • The highest level of total energy demand on the power system at a given time (e.g. daily peak, seasonal peak, annual peak) (Keay-Bright, 2013; NIC, 2016).

  • TEN
  • trans-European Networks

  • Transmission network
  • The high voltage network that is used to move electricity long distances (NIC, 2016).

  • Transmission System Operators (TSOs)
  • These are responsible for balancing supply and demand in the electricity system on a second-by-second basis, which ensures grid stability. TSOs are tasked with the operation of the electricity system after gate closure by dispatching power plants and demand response on the basis of bids in the wholesale electricity market. They are also responsible for balancing capacity in the case of system stress caused by unexpected weather conditions, technical deficiencies or short-term changes in electricity demand (Grigorjeva, 2015). The TSO in the UK is National Grid, in France the TSO is Réseau de Transport d’Électricité (RTE), while Germany has multiple TSOs. In the US they are often called Independent System Operators or Regional System Operators.

  • UCPTE
  • Union for the Coordination of Production and Transmission of Electricity

  • UKDECC
  • UK Department of Energy and Climate Change

  • Value of lost load (VOLL)
  • The estimated maximum price that customers would be willing to pay to avoid a loss of supply. The value of VOLL is often different for each class of consumer (industrial, commercial, domestic) and for individual consumers within those broad classes (Baker et al., 2015; IEA, 2016).

  • Variable generation
  • The term variable describes the fluctuating nature of wind and solar electricity generation in response to changing weather conditions, independently of changes in demand. This makes these sources less controllable for network operators than dispatchable resources (such as hydropower, gas-fired generation or demand side response), for which output can be increased or decreased in response to supply scarcity or fluctuations in demand (Hogan, 2012).

  • WCI
  • Western Climate Initiative

  • Wholesale electricity market
  • The market where trading takes place between generators, retailers and other financial intermediaries for delivery of electricity to meet forecasted demand before gate closure. After gate closure, system operators are responsible for balancing supply and demand in real-time (see balancing markets).

  • ZEP
  • Zero Emissions Platform