2. Stored Energy, electrical or deliverable as heat, (MJ/kg)
Energy in MJ/kg Can view energy density in terms of either per unit volume or per unit mass

4. Same thing, but on a log scale

5. Pumped heat electricity storage (PHES),
PHES, on the other hand, is much simpler – electricity from a source such as a solar or wind farm is used to run a heat pump. The pump heats water stored in a large tank (normally about 100,000 cubic metres in volume) and then, when needed, the heated water is sent to a heat engine and electricity is produced. A heat pump, rather than an electric heater, is used to heat the water because it makes the whole process much more efficient.

6. Pumped Hydro

10. MW rating a function of the number and capacity of turbines, but does not directly reflect the size of the reservoir

11. Hydropower sites much more numerous than pumped-hydro sites.

12. Batteries

13. Battery Energy Density
For a Vehicle, both weight and volume energy densities are important

26. The question that motivates our research is, “how does incorporating grid-flexibility technologies affect the energy return on energy investment (EROI) for low-carbon energy systems?”
The comparative metric I developed adopts life cycle assessment techniques and is called the “Energy Stored on Energy Investment” (ESOI). It is a ratio of all the energy stored over the entire life of storage technology to the amount of energy required to acquire the device’s raw materials and assemble them. The greater the ESOI value the less of an energetic drag a storage technology will be on the low-carbon energy system.

27. The results show that ESOI values for battery technologies are between 2 and 10. ESOI values are greater than 200 for geologic storage technologies like pumped-hydroelectric storage (PHS) and compressed air energy storage (CAES). There are two reasons why geologic storage technologies perform over an order magnitude better than battery technologies. Firstly, they are made from abundant and relatively energetically low-cost materials: earth, water, cement and steel. Secondly, they are very durable and can be charged and discharged tens of thousands of times. This high cycle-life means that the amount of energy stored over its life is much greater than a lead acid battery, for example, which can only be cycled a few hundred times.

28. Energy storage systems provide a wide array of technological approaches to managing ourpower supply in order to create a more resilient energy infrastructure and bring cost savings to utilities and consumers. To help understand the diverse approaches currently being deployed around the world, we have divided them into six main categories:
Solid State Batteries - a range of electrochemical storage solutions, including advanced chemistry batteries and capacitors
Flow Batteries - batteries where the energy is stored directly in the electrolytesolution for longer cycle life, and quick response times
Flywheels - mechanical devices that harness rotational energy to deliver instantaneous electricity
Compressed Air Energy Storage - utilizing compressed air to create a potent energy reserve
Thermal - capturing heat and cold to create energy on demand
Pumped Hydro-Power - creating large-scale reservoirs of energy with water
You can learn more about each of these technologies by using our navigation on the right hand side of this page, and each category includes real-world examples of how these approaches being deployed in the field.