Electrical Energy Storage (EES) is the process of converting electrical energy from a power network into a form that can be stored for converting back to electricity when needed. EES enables electricity to be produced during times of either low demand, low generation cost, or during periods of peak renewable energy generation. This allows producers and transmission system operators (TSOs) the ability to leverage and balance the variance in supply/demand and generation costs by using stored electricity at times of high demand, high generation cost, and/or low generation capacity.
EES has many applications including renewables integration, ancillary services, and electrical grid support. This blog series aims to provide the reader with four aspects of EES:
- An overview of the function and applications of EES technologies,
- State-of-the-art breakdown of key EES markets in the European Union,
- A discussion on the future of these EES markets, and
- Applications (Service Uses) of EES.
Table: Some common service uses of EES technologies
Storage Category |
Storage Technology |
Pumped Hydro |
Open Loop |
Closed Loop |
|
Electro-chemical |
Batteries |
Flow Batteries |
|
Capacitors |
|
Thermal Storage
|
Molten Salts |
Heat |
|
Ice |
|
Chilled Water |
|
Electro-mechanical |
Compressed Air Energy Storage (CAES) |
Flywheel |
|
Gravitational Storage |
|
Hydrogen Storage
|
Fuel Cells |
H2 Storage |
|
Power-to-Gas |
Unlike any other commodities market, electricity-generating industries typically have little or no storage capabilities. Electricity must be used precisely when it is produced, with grid operators constantly balancing electrical supply and demand. With an ever-increasing market share of intermittent renewable energy sources the balancing act is becoming increasingly complex.
While EES is most often touted for its ability to help minimize supply fluctuations by storing electricity produced during periods of peak renewable energy generation, there are many other applications. EES is vital to the safe, reliable operation of the electricity grid by supporting key ancillary services and electrical grid reliability functions. This is often overlooked for the ability to help facilitate renewable energy integration. EES is applicable in all of the major areas of the electricity grid (generation, transmission & distribution, and end user services). A few of the most prevalent service uses are outlined in the Table above. Further explanation on service use/cases will be provide later in this blog, including comprehensive list of EES applications.
Area |
Service Use / Case |
Discharge Duration in h |
Capacity in MW |
Examples |
Generation |
Bulk Storage |
4 – 6 |
1 – 500 |
Pumped hydro, CAES, Batteries |
Contingency |
1 – 2 |
1 – 500 |
Pumped hydro, CAES, Batteries |
|
Black Start |
NA |
NA |
Batteries |
|
Renewables Firming |
2 – 4 |
1 – 500 |
Pumped hydro, CAES, Batteries |
|
Transmission & Distribution |
Frequency & Voltage Support |
0.25 – 1 |
1 – 10 |
Flywheels, Capacitors |
Transmission Support |
2 – 5 sec |
10 – 100 |
Flywheels, Capacitors |
|
On-site Power |
8 – 16 |
1.5 kW – 5 kW |
Batteries |
|
Asset Deferral |
3 – 6 |
0.25– 5 |
Batteries |
|
End User Services |
Energy Management |
4 – 6 |
1 kW – 1 MW |
Residential storage |
Learn more about EES in the EU in the next post.
(Jon Martin, 2019)
This post is also available in Deutsch.