Energy storage is integral to life as we know it. Since it was discovered that electricity could be put to use in practical applications, scientists have been searching for more efficient ways to store and utilise it, and this search still goes on.
It is now widely understood that a move towards a low carbon future must involve the generation of electricity using renewable sources of energy such as geothermal, wind, solar, hydro and tidal power.
Facts and Figures
Renewable sources generated 15% of the UK’s electricity in 2013 (figure 1) (Digest of UK Energy Statistics, Chapter 6)
The global energy storage industry currently generates sales of $50-60 billion per year (Energy Storage Association)
Scotland’s installed capacity of renewable energy has increased by almost 250% since 2007 (Scottish Renewables)
As we well know, wind and sunlight are never present at a consistent level (readers based in Scotland may understand this more than others) and our demand for energy also varies greatly. TV pickup is the phenomenon that during the advert break of a prime time Saturday night TV program, extra power stations must come online within minutes in order to power the millions of kettles suddenly turned on and demanding several further gigawatts from the grid.
In the past, Energy Storage with fossil fuels was largely taken care of by having a big enough coal store, fuel tank, or gas supply. Being able to manage the phasing of supply with demand is therefore imperative for renewables to continue to displace fossil fuels, and so energy storage is one of the most important issues in energy today, and one of the main factors holding back the low carbon transition.
Energy Storage Technology
The oldest form of rechargeable battery for electricity storage is the ‘wet cell’ lead acid battery, which is heavy, unsealed and so prone to leakages, and has to be kept well-ventilated due to the mix of hydrogen and oxygen gas it produces when overcharged. Fortunately, the technology has moved onwards, to sealed dry cell batteries such as nickel-cadmium (NiCd) and lithium-ion (Li-ion) cells that are used in mobile phones and laptops.
Flow batteries are similar to fuel cells in that the two liquid reactants are kept in separate containers. Energy can then be extracted or fed in by flowing the reactants past two electrodes separated by a membrane. The amount of energy stored is only then limited by the size of the reactant tanks. In comparison with other types of rechargeable battery described above, flow batteries have a much longer lifespan although they are not currently widely used due to the cost and difficulty in maintaining the materials needed.
However, new research from scientists at Harvard has identified new materials that could significantly reduce the costs associated with flow batteries.
Organic molecules called quinones are extremely good at grabbing and releasing electrons – and so are ideal for use as the liquid reactant in flow batteries. Quinones are plentiful in all green vegetables (especially in rhubarb). They are also about one third of the cost of existing flow battery materials. This research is still ongoing – but the team at Harvard envisage a flow battery the size of a conventional oil tank for individual households that could store a few days’ supply of energy needs.
Similar flow battery technology from UniEnergy Technologies using a Vanadium electrolyte is also approaching the commercial stage.
Electric Vehicles for Energy Storage?
How about using your electric vehicle (EV) battery to power your home? This would be feasible using the electricity generated by a small wind turbine or solar panels to charge the car, using the car battery for storage, then using the stored electricity to support powering your home during expensive peak times. The residential sector is responsible for 13% of UK CO2 emissions, while transport is responsible for 21% (figure 2), so large scale deployment of and strategic use of EV power storage systems could greatly reduce national CO2 emissions.
There are some massive benefits of more advanced, efficient energy storage solutions. To energy customers these include:
- Improved match between intermittent supply and consumer demand.
- Reliable delivery
- Reduced emissions
- Mobile power
- Ultimately – a more affordable and secure energy supply
To the energy industry these include:
- Improved stability and reliability of transmission and distribution system
- Improved availability and increased market value of distributed generation sources
- Improved energy security
In the low carbon space, all of the early focus has been on generation technologies. Only recently have the implications of low carbon generation systems for power distribution and storage started to be addressed. Despite being critical to the future of a low carbon system, much more focus on energy storage is required, especially at a commercial and industrial level. Many opportunities and challenges exist;
- Potential to use hydrogen as an energy carrier and as an energy store
- Connecting the gas and electricity grids (see: Power to Gas: Connecting the Grids)
- Power grids not being designed for distributed generation
- The need for commercial models to support storage developments
- Spreading the load more evenly, managing growth in peak demand and avoiding spending on asset augmentation or reinforcement
- Energy storage for remote areas not serviced by the grid
- The need for new storage technologies
- Energy losses during storage
Significant improvement in energy storage is possible, and such a revolution would be comparable to the transformation seen in data storage over the past few decades – from floppy discs to SD cards to cloud storage. In 2013, the cloud was estimated to contain the data equivalent of 728 billion floppy disks.
Developing a form of energy storage that could meet electricity supply and demand smoothly and simply, represents an enormous breakthrough in electricity distribution and to delivering a low carbon future. More efficient and low cost forms of energy storage will benefit individuals, businesses, and society as a whole.
This article was written by Jen Hickling.