Electricity storage is used to overcome short and long-term fluctuations in the balance between supply and demand for electricity. Overcoming short term interruptions is the preserve of power quality and uninterruptible power supply, but maintaining frequency on the system by responding to rapid falls or rises in frequency or high rates of change of frequency, is also an important duty for many modern energy storage assets. As the time period increases, the important parameter is not necessarily power, but the energy content, and there is a viable role for energy storage to balance energy over minutes, hours or even days.
This becomes important when our future power markets may have periods of very low or negative prices as well as times when the market is short, and energy becomes scarce. A third benefit of storage is to consider its use as a means of optimising the assets of a power network – operating lines, cables and transformers at constant load, and not having to size these expensive items to meet a peak load that is only achieved at irregular intervals.
Quantifying the benefits of storage is complex – because the benefits accrue from a number of separate income streams, but this is a regulatory and commercials market issue – this is not just applicable to storage, but also to many of the smart grid and active network management issues.
Imperial College produced a useful and informative report in 2012 on the role and value of storage. It looked at a number of scenarios for the GB system up to 2050. The report shows the value of storage as a complete system asset, and the modelling used to compile its results suggests that 2000 MW of additional storage installed by 2020 would have an annual benefit of about £120 million / year. If the amount of storage were increased, in line with the requirements of the system, then it should reach 15 GW by 2030 and 25 GW by 2050, when the total benefit would be £10 billion.
Not everyone sees this benefit – electricity storage tends to act on behalf of the whole system and we shall need a new regulatory structure and new business models to capture all the value, but in the meantime, some early adopters will be able to capture a significant portion of the value.
In recent years, we have seen targets and objectives for many new technologies, going through the stages of market introduction and commercial viability. Sometimes these targets are ambitious and merely aspirational – as demonstrated by the growth figures for fuel cells and electric vehicles of the 1990s, but other targets, such as those for wind and PV solar development have been a useful guide as to what might be possible. The electricity storage network, the group which promotes the role of electricity storage development in the UK, is proposing a target of 2000 MW of new electricity storage to be operational by 2020. 2000 MW has been adopted as a realistic target and it should be measured against the following benchmarks:
A) The imperial College report uses 2000 MW as the grassroots scenario for 2020 delivering benefits of £120 million / year
B) 2000 MW spread over the next seven year is about 300 MW / year – which would be a challenge in the next couple of years, but could be easily achieved in the period 2015 – 2020
C) Good progress is already being made through various LCNF projects to demonstrate the value and benefits of electricity storage
D) In terms of order of magnitude, 2000 MW is of the same scale as the Dinorwig Pumped Hydro station in North Wales
E) 2000 MW is about 3% of the nation’s peak demand, which would make a useful contribution to the reserve requirement
F) 2000 MW represents about 25% of the STOR requirement described by National Grid
G) There was 2000 MW of solar PV installed in the last two years – 2000 MW of storage would be a balancing for between 6000 and 8000 MW of solar PV
H) 2000 MW is the same order of magnitude as 10% of the planned installation of new wind turbines in the period up to 2020
While there are various strategies and scenarios for the adoption of targets for renewables, the UK government has not published a strategy for the need to incorporate storage in the nation’s power systems. This is in stark contrast to the detailed plans for changing the carbon intensity of generation, the adoption of targets for renewables and the introduction of technologies such as smart meters and electric vehicles.
We believe that setting a target, which is achievable, beneficial and comprehensively covers all electricity storage technologies is an essential step forward in delivering our sustainable, secure and economic power system of the future.