Cost-effective small-scale storage (in the range of a few megawatts) has great possibilities to assist the economics of renewable energy generation.

In stand alone mini-grids MW scale storage could dramatically reduce use of liquid and fossil fuels during peak demand, and with grid connected renewable projects, well sized storage would increase the opportunity of renewable generators to sell into demand peaks.

In May this year the Federal Government awarded $17.6 million in funding to five companies to demonstrate advanced electricity storage systems.

Four of the five are essentially large scale chemical batteries, variously using vanadium oxides, zinc bromide, or ammonia as the compounds through which to store and release energy.

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One of these four projects, a large ammonia storage project planned for South Australia, does however recover stored energy by using heat released when the solar thermally disassociated ammonia recombines from its constituent elements of hydrogen and nitrogen.

The fifth project to win funding support is completely novel, deceptively simple and also uses thermal energy. Lloyd Energy Systems has developed a very high performance thermal storage system based on crystalline graphite. The $5 million grant secured from the Federal Government will be matched with a further $5 million in private funding to demonstrate a 15 MW graphite storage system.

The system was first invented and developed by Bob Lloyd, who worked on the technology for 20 years in a shed in Cooma, in the NSW southern highlands.

The core of the technology is the ability for high purity crystalline graphite to store thermal energy for long periods, with near zero degradation of the structure of the material.

In the process Lloyd Energy Systems has developed a suite of intellectual property across the manufacture of high quality crystalline graphite, and its fabrication into energy storage systems.

The project will use 16,000 sq m of heliostats to concentrate solar thermal energy on 16 seven tonne crystalline graphite blocks sitting atop low rise towers.

The sixteen 2.7 m3 graphite blocks will each have a 1,000 sun beam focused on their receivers.

The heat is then recovered when required by flooding embedded boiler tubing with water and producing steam to drive small turbines. The capacity of the graphite to store thermal energy is exceptional and in this first plant the graphite store has to be limited to about 1,000ºC to avoid the destruction of the heat exchange elements and other equipment.

This project should be able to store sufficient energy to provide grid support for up to five hours in winter and nine hours in summer, delivering up to 3 MWh during peak demand periods to Country Energy’s distribution network at Lake Cargellico and Condobolin in mid-west NSW.

Lloyd Energy Systems CEO Steve Hollis says the system is about 35 to 40 per cent efficient in recovering thermal energy to produce electricity.

However in this sort of grid support role, where the cost of augmenting the distribution network to deliver the extra power to such a distant part of the grid is simply prohibitive, the economics stack up.

Given the success of the first project future applications will almost certainly look at similar solar thermal storage arrangements however an effective thermal store can of course accept heat from any source.