Battery based energy storage systems (ESS) are growing in importance as renewable energy sources like wind power, wave power and solar are being commissioned and connected to the grid at an ever-increasing rate. Energy Storage Systems are needed to help the grid deal with the instability and unpredictability of such power generation systems and match them to equally variable consumer demand.

In the UK, renewables currently produce over 20% of the country’s electricity and this is likely to exceed 30% by 2020. The current installed capacity is in the region of nine gigawatts indicating the nation’s reliance on more environmentally friendly forms of energy generation into the future.

Battery-based systems are rapidly gaining market share for use as energy storage and gaining acceptance due to advances in their design. Other energy storage approaches can use a range of media, including compressed air, pumped hydro and flywheel. Properly packaged, battery-based systems offer advantages in portability and size.

The configuration of batteries and the set-up of the system can bring a variety of benefits to grid quality; some configurations are useful for rapid response short-term discharge to maintain grid frequency stability and power quality, others meanwhile can supply a longer duration output to perform load balancing and peak shaving, or even backup power on a micro-grid.

The technical capabilities and benefits of a battery energy storage system can address multiple aspects of power quality and storage.

  1. Frequency regulation – Because utilities must maintain their output within a narrow frequency range, this is a common application. High demand can cause a slight drop in frequency, especially on systems of lower capacity. Batteries can compensate for peak loading with a high-energy discharge within a second.
  2. Ramp rate control and capacity firming – This is especially important with renewable energy sources such as wind and solar farms. In these applications, the storage element can fill the gaps that occur when output dips due to a major reduction in wind energy or when clouds move over a solar farm.
  3. VAR support – Reactive loading reduces the efficiency of transmission and distribution lines, but an appropriately designed battery storage system can compensate by supplying an adjustable range of real or reactive power. This allows more efficient use of power lines and distribution equipment.
  4. Replacing spinning reserve – Reserve capacity helps maintain output during generator failure or unexpected transmission loss, which could require power reductions to customers. Keeping generator capacity online but unloaded wastes fuel and causes unwanted air emissions. Batteries can take the place of conventional spinning reserve generation and improve efficiency.
  5. Black start – This capability allows a power plant to bootstrap itself after a blackout, grid connection loss and/or loss of generation capacity.
  6. Arbitrage/time shifting – This is the storage of low-cost power for later sale at higher prices. Generally this occurs during hours of lower demand.
  7. Transmission and distribution upgrade deferral – Being able to defer additional infrastructure costs is attractive to utilities that are experiencing significant, albeit uneven, growth in power usage. Generally, demand is characterised by ever higher peak loads that occur with increasing frequency. Eventually, existing transmission and distribution infrastructure becomes the weak link between a power plant and customers. A utility-scale BESS can be deployed near the load to level out power flow and delay a costly upgrade.


Market growth for battery storage
Market growth for battery storage

Current battery storage market

In terms of Grid level storage, most of the focus is currently centred around frequency response. In the UK, battery storage has dominated the outcome of the National Grid’s 200MW Enhanced Frequency Response tender.

This was developed to bring forward new technologies to provide sub-second response solutions to system volatility, improving on the previous fastest frequency response which could be delivered in under ten seconds. This enhanced ability to control variations in frequency almost immediately is expected to result in reduced costs of approximately £200 million. The speed of response is also critical to counteracting the loss of system inertia, which relates to how well the grid resists changes and is affected by increased levels of renewables on the grid.

According to Citigroup, the global battery storage market (not including car batteries) will surge to 240 gigawatts (GW) and $400 billion by the year 2030. The main drivers of this growth, according to the report, will be a reduction in battery storage system costs to $230/megawatt-hour (MWh) within the next 7–8 years, and growth in solar energy generation — which will combine to make the technologies financially attractive to growing numbers of countries.

Historic price declines in battery prices
Historic price declines in battery prices

According to the report — Dealing with Divergence — the only thing standing in the way of huge growth in the battery storage market is the still relatively high cost associated with its use. According to Citigroup, though, the market is likely to see a similar growth trajectory in the next few years as that seen in the solar energy market over the last few — with a similar cause: falling costs lead to increased deployment, and increased deployment then leads to further falling costs.

Charging forward

Others, however, take a dimmer view believing that storage will not be economical any time soon. That pessimism cannot be dismissed. The transformative future of energy storage has been just around the corner for some time, and at the moment, storage constitutes a very small drop in a very large ocean. In 2015, a record 221 megawatts of storage capacity was installed in the United States, more than three times as much as in 2014—65 megawatts, which was itself a big jump over the previous year. But more than 160 megawatts of the 2015 total was deployed by a single regional transmission organisation, PJM Interconnection and 221 megawatts is not much in the context of a total US generation capacity of more than a million megawatts.

For the near future, the dominant form of energy storage, pumped hydropower, is sure to remain the principal method of storing energy. Aside from pumped hydro, a plethora of energy storage technologies exist with a growing number of new solutions being tried, tested and installed on a commercial basis. An even larger number reside anywhere between blueprint designs and various levels of research and development.

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    • Hi David – thanks for the kind words and my view would that we’re really at an interesting transition point in the energy sector at the moment. The old centralised one to many relationships which have been the cornerstone of generation for 70 years is going flip; distributed generation, embedded systems, localised demand responses etc etc in concert with the reduction in cost and growth in data will present numerous opportunities.

      What happens when we’re in a world of many-to-many or many-to-one generation? How do investors maximise generation asset value when we’ve large scale electric vehicle deployment or the ability to smooth of the suuply/demand function? As importantly, are we even set up to manage, analyse and secure the vast swaths of data we’re going to be generating?

I'd love to hear what your thoughts are...please feel free to leave a reply