Back into the dark ages

The government must look beyond the near-term future if the UK’s utility companies are to have a chance of providing enough electricity for our grandchildren. William Nuttall reports.

The Regenesys project was designed to store electricity commercially, challenging the fundamental premise of the electricity market: that electricity is not a storable commodity.

But German utility company RWE has abandoned work on the Regenesys regenerative fuel cell project at Little Barford in Cambridgeshire. The origins of the move lay in the economics of an electricity industry operating on razor-thin margins.

The economics of Regenesys were always going to be difficult and multifaceted. The economics of electricity storage dictate that there will be significant price differences between periods of high and low demand. This raises the question of whether stored electricity could ever be supplied more cheaply than fresh electricity generated in conventional ways.

However, I am convinced that increased electricity storage research should be a national priority. The government should therefore look hard at Regenesys (in which it has already invested almost £900,000 from the DTI Sustainable Energy Programmes) and act to ensure that the national interest is best served in this important area.Regenesys adopted a sensible phased approach to the technical challenges involved in creating a power storage facility. It started with a small 1MW experiment at Aberthaw in south Wales, where things went so well that it moved forward to industrial-scale development at Little Barford.

The Regenesys approach used 24,000 stacked ion exchange membranes to separate two electrolytes: sodium bromide and sodium polysulphide. When a voltage was applied across the Regenesys cell, sodium ions migrated through the semi-permeable membrane from the sodium bromide to the sodium polysulphide. This left behind an electrolyte rich in sodium tribromide and created an electrolyte rich in sodium sulphide. The electrolytes store electricity as a result of their modified chemistry. The altered electrolytes could be pumped away into large tanks. The liquids themselves contained the stored electricity.

The Regenesys facility could charge or discharge 12MW and, importantly, switch between charging and discharging so fast that there would be no disruption to the electricity grid. The total electricity storage capacity would be limited solely by the size of the electrolyte tanks.

The Little Barford facility would have been able to store an impressive 120MWh at about 65 per cent efficiency, making it the world’s largest electrochemical storage device.

The technical challenge was substantial, in particular the need for semi-permeable membranes that would not leak or become clogged over 15 years of operation. But it appears that, despite some difficulties, the project faced no unavoidable technical show-stoppers.In the US the Tennessee Valley Authority (TVA) was so impressed with Regenesys’s technology that it invested $30m (£16.5m) to build a plant in Columbus, Mississippi.

Following RWE’s cancellation of the UK project, a TVA press release said: ‘Though unproven, the Regenesys technology may be viable. It encountered a number of engineering difficulties during its scaling-up to commercial size, but these might be adequately addressed with sufficient time and investment of resources.’

Opportunities for Regenesys, however, not only included buying electricity cheaply and selling it later when prices are high. The technology also promised to help with the task of restarting an electricity grid after a major blackout. Another key focus was the possibility of selling the Regenesys concept and design to utilities world-wide. The collaboration with the TVA was important in that regard.

It is important to consider the environmental issues relating to electricity storage. Regenerative fuel cells (or redox flow batteries as they are also known) really are storage devices. The electricity they provide is as green as the electricity originally stored. If the electricity stored is renewable, then the environmental benefits are clear.

Large-scale storage technologies, such as Regenesys, are of key importance to intermittent technologies such as wind and solar power. However, the environmental benefits of electricity storage go still further. Large-scale storage might allow nuclear power to operate far more economically, by allowing it to escape from its market position as the most base of ‘base-load’ technologies.

Large-scale storage might also allow for a reduction in the use of inefficient spinning reserves – extra power plant generating capacity that is kept running to respond quickly to sudden rises in power demand – and stand-by capacity. Fossil-fuelled plants contributing to the grid would be able to run at far closer to their best thermodynamic efficiencies if they did not have to fluctuate their outputs to maintain grid stability.

However, none of these environmental factors plays a part in the electricity markets of today. And utility firms such as RWE must operate according to the dictates of how the market is now, rather than trusting to the emergence of better electricity markets in future. Bearing this in mind, RWE has probably made the right business decision in terminating Regenesys.

Nevertheless, there is a strong case for continuing research into electricity storage projects such as Regenesys. An expert workshop convened by the Institute of Energy (now the Energy Institute) in March 2002 concluded that electricity storage research priorities should include electrolytic devices such as the Regenesys system.

In August 2002, The Royal Academy of Engineering announced that ‘as more renewable sources are connected to the grid, electricity storage will become essential – our only current storage capacity is through hydroelectric storage schemes.’

EA Technology’s Future Energy Solutions said in September 2002 that ‘more attention should be given to the development of next-generation energy end-use devices, processes and integration concepts. Examples would include advanced electricity storage systems.’

The government knows that the UK must increase its spending on energy R&D. Electricity storage is a tricky technology and policy problem, as it combines numerous public and private stakeholders with different skills and interests.

Any argument that such matters are not the concern of government as they are now ‘competitive’ has, I would suggest, been shown to be way off the mark by RWE’s recent actions.

Dr William Nuttall is director of the MPhil in technology policy at Cambridge University