A new type of long-duration energy storage that can facilitate 24/7 wind and solar energy has been inaugurated at the world’s largest concentrated solar power (CSP) plant in Morocco.
The pilot technology from Swedish start-up Azelio — which stores energy in molten aluminium — has been installed at the 580MW Noor Ouarzazate solar complex (510MW of CSP and 70MW of PV), and will be tested with a view to installing a larger commercial system on the site later this year, “followed by volume production in 2021”.
The technology uses electricity to heat recycled aluminium to 600°C, with the molten metal acting as the storage medium. When power is required from the storage unit — which sits inside a shipping-container-style box — the stored thermal energy is transported to a Stirling engine using a heat-transfer fluid. The Stirling engine, which is powered by the heat, then runs a generator to produce electricity. Waste heat at a temperature of 65°C can also be sold to industrial users or local district heating systems.
According to Azelio, the process has a 90% round-trip efficiency — ie, the amount of energy that goes in, compared to the amount that comes out — when both electricity and waste heat are utilised.
The company has given no indication of the system cost or the levelized cost of storage — nor the size of the pilot or future installations at Noor Ouarzazate, which is owned by the Moroccan Agency for Sustainable Energy (Masen).
It is therefore difficult to compare Azelio’s system with other build-anywhere long-duration intermittent energy storage (Baldies) technologies.
The global leader in this nascent market is Highview Power, with its liquid-air storage technology fully commercialised; Siemens Gamesa’s hot-rock thermal system, which uses volcanic rocks as its storage medium, is still undergoing testing in Germany; while Google spin-off Malta’s molten-salt storage hardware and Stiesdal Technologies' hot-rock thermal system are still in the development stage.