Energy Storage Offers Tailored Grid Solutions, But at What Cost?

The grid must maintain a full balance between generation (supply) and load (demand) at all times. In small-scale networks, imbalances occur more often and are generally more difficult to manage when compared to large-scale networks that often incorporate interconnector links.

Tackling Imbalance

Any imbalance situation between generation and load must be counteracted instantly in order to prevent wider issues, which can include a grid blackout in a worst-case scenario. In order to cope with larger amouts of distributed energy, networks should consider introducing or expanding energy storage to meet higher grid stabilizing demands and energy surpluses.

All power-generating sources, renewable and non-renewable, are characterized by specific inherent technology and operating features. In classic conventional electricity systems such as coal or nuclear, plants provide baseload energy because their operating output levels can only be varied gradually. Much faster-reacting natural gas-fired power plants are therefore necessary for managing rapid network demand fluctuations.

Utilities recognize and address the characteristics of each energy technology. For example, in Europe wind farms produce the bulk of their yield during autumn and winter, whereas PV plants yield best in summer and inherently do not produce during night hours. Combining these two complementary sources in an electricity network offers some grid stabilization and other benefits without actual storage.

The Stability Phenomenon

Biomass plants that burn sustainable dry fuels like wood pellets fit into the baseload category, whereas liquid biofuels can add to both baseload and fast-response variable capability. Geothermal has also been proven to be both a baseload and responsive technology. Combining biomass and geothermal with wind and solar in a single network inherently adds storage capacity through the contained energy in the biomass and geothermal resources.

Public discussions about network stability and grid disturbance often overlook the fact that fluctuations in demand are an inherent system phenomenon independent of the generating resource. There will always be demand differences during daytime and night hours, on work days versus weekends, between months and seasons, and during special events like electricity demand peaks during football match breaks. 

Wind power is wrongly blamed as a primary electricity network disturbance that endangers stability. PhD research conducted under specific Dutch conditions showed that “natural” network demand fluctuations are far greater compared to the variability caused by wind power. The study also showed that a need for energy storage would only arise when wind capacity, as a share of total generating capacity, exceeds around 33 percent — it currently stands at about 4 percent. Nevertheless, below we explore some potential energy storage applications that could work in parallel with wind power.

Hydrogen Technology

Rather rudimentary “island” wind-diesel systems comprised of one or more fixed-speed stall-regulated turbines and diesel generators do not incorporate energy storage, and wind surpluses are simply “burned” via a dump load. More sophisticated modern wind-diesel systems that include modern (active) pitch-controlled variable-speed wind turbines do not require dump loads.