There are many new developments in the search for an effective way to store and distribute electricity
The problem of autonomy and recharging of zero-emission vehicles is central to the success of the revolution in motorised transport. This requires largescale planning and investment, both of which can be well-served by commitment by the car and petrol distribution companies. Is there a market motivation for them?
Lithium batteries are the choice of Elon Musk and his $2-billion Gigafactory for Tesla electric vehicles. However, these would be expensive and relatively inflexible for the needs of grid storage. The erratic feeds from renewables would cause too much variation in load for the batteries to be efficient. Price: $250 per kWh, total cost (including building the South Australian 100-MWh plant) is $500 per kWh to connect the batteries to the griid. The SA 100MWh plant costs $50m.
AES, a global energy company, is developing a large-scale lithium-ion battery project.
Sodium as an alternative to lithium would be cheaper, since sodium is more abundant.
By end of 2016, battery installations in America, led by utility-scale storage, doubled to 336MWh. Much of this is in California.
[The Economist, 18.03.17 p. 58: Elon Musk and batteries] See also GTM (consultancy) and Energy Storage Association (US).
Energy Storage Systems (ESS) in Portland, Oregon, proposes a solution of iron ions in water. Being liquid, this opens the possibility of cars ‘retanking’ their electrolytes, rather than waiting for a battery to recharge the usual way.
Halotechnics in Emeryville, Calif., propose a system by which energy is stored by melting phosphate-based glass, which has a relatively low melting point. The very low-viscosity liquid (behaves like honey at 400°C) can be pumped as a liquid, and the thermal energy released as it cools used to evaporate steam for a traditional turbine. It plans to run a trial at an aluminium plant, using the waste heat from smelting.
Air takes energy to be compressed, and releases it when needed. The air can be stored underwater, where the water’s weight provides the pressure containment needed. Alternatively, the air could be stored down abandoned mine shafts, or in salt basins.
Not a new technology, but undergoing a surge in interest. Excess energy is used to pump water up to a reservoir for later hydro-generation.
A microgrid is a small, networked section of the grid that can generate its own electricity from distributed generation, and can be disconnected from the grid to operate autonomously. Energy sources are: solar panels, wind turbines, CHP, geothermal installations, biodigesters. Microgrids can feed excess power to the grid. They can also have large battery banks to store excess power for own use. Green Mountain’s 7,700 solar panels generate 2.5MW to 3,000 households, and has enough lithium-ion and lead-acid batteries to store 3.5MWh.
Advanced Rail Energy System ARES
A pilot programme run by Valley Electric Association, Nevada, to store electrical power by a system where the gravitational potential of a heavily-laden train stores electrical power from renewable sources during low demand periods, and releases it during high demand periods by running the train down a 6-8% grade slope.
The test system is rated at 50MW, but claims to double the capacity of a 500MW system and increase capital costs (c. $1,100 per kW, $4,400/kWh storage) by only 20%. costs comparison with other storage systems:
- ARES: $1,100 /kW
- lithium ion batteries: $1-2,000 /kW
- compressed air storage: $1,600-2,200 /kW
- pumped hydro storage: $1,200-2,100 /kW