Technology (VRFB)


Additional information

Informative Africa energy and general energy storage links








Energy storage terminology

Seasonal storage
The ability to store energy for days, weeks, or months to compensate for a longer-term supply disruption or seasonal variability on the supply and demand sides of the energy system (e.g. storing heat in the summer to use in the winter via underground thermal energy storage systems)
Arbitrage/Storage trades
Storing low-priced energy during periods of low demand and subsequently selling it during high-priced periods within the same market is referred to as a storage trade.1 Similarly, arbitrage refers to this type of energy trade between two energy markets
Frequency regulation
The balancing of continuously shifting supply and demand within a control area under normal conditions is referred to as frequency regulation. Management is frequently done automatically, on a minute-to-minute (or shorter) basis
Load following
The second continuous electricity balancing mechanism for operation under normal conditions, following frequency regulation, is load following. Load following manages system fluctuations on a time frame that can range from 15 minutes to 24 hours, and can be controlled through automatic generation control, or manually
Voltage support
The injection or absorption of reactive power to maintain voltage levels in the transmission and distribution system under normal conditions is referred to as voltage support
Black start
In the rare situation when the power system collapses and all other ancillary mechanisms have failed, black start capabilities allow electricity supply resources to restart without pulling electricity from the grid
T&D congestion relief and infrastructure investment deferral
Energy storage technologies use to temporally and/or geographically shifting energy supply or demand in order to relieve congestion points in the transmission and distribution (T&D) grids or to defer the need for a large investment in T&D infrastructure

Demand shifting and peak reduction
Energy demand can be shifted in order to match it with supply and to assist in the integration of variable supply resources. These shifts are facilitated by changing the time at which certain activities take place (e.g. the heating of water or space) and can be directly used to actively facilitate a reduction in the maximum (peak) energy demand level
Off-grid energy consumers frequently rely on fossil or renewable resources (including variable renewables) to provide heat and electricity.1 To ensure reliable off-grid energy supplies and to support increasing levels of local resources use, energy storage can be used to fill gaps between variable supply resources and demand
Variable supply resource integration
The use of energy storage to change and optimize the output from variable supply resources (e.g. wind, solar), mitigating rapid and seasonal output changes and bridging both temporal and geographic gaps2 between supply and demand in order to increase supply quality and value
Waste heat utilization
Energy storage technology use for the temporal and geographic decoupling of heat supply (e.g. CHP facilities, thermal power plants) and demand (e.g. for heating/cooling buildings, supplying industrial process heat) in order to utilize previously wasted heat
Combined heat and power
Electricity and thermal energy storage can be used in combined heat and power (CHP) facilities in order to bridge temporal gaps between electricity and thermal demand
Spinning and non-spinning reserve
Reserve capacity for the electricity supply is used to compensate for a rapid, unexpected loss in generation resources in order to keep the system balanced. This reserve capacity is classified according to response time as spinning (15 minute response time). Faster response times are generally more valuable to the system. In some regions, reserve capacity is referred to as "frequency containment reserve"
  1. The term "arbitrage" is used for both arbitrage and storage trades in this roadmap
  2. This is also the case for energy users who produce most of their own heat and electricity (i.e. self-generation)
  3. When combined with other energy system infrastructure (e.g. transmission lines

Source: US DoE - Grid Energy Storage report 2013