Energy journalist and former Renewable Energy World editor David Appleyard explores developments in battery storage and how this evolving technology can best support Demand Side Response.
Increasing renewable energy penetration has led to some challenges for electricity transmission and distribution network operators. With variable-output renewables like wind and solar rapidly superseding traditional thermal and nuclear generation, concerns over balancing supply with demand and grid stability are growing.
While renewable energy has many benefits, it is largely uncontrollable. If it is not windy, you can’t ramp up wind capacity even if the demand for power is at peak levels.
Furthermore, renewable growth has seen system inertia fall. Fewer traditional thermal power plants means there is far less of the spinning metal found inside, say, a large coal-fired power station. That makes it much harder to keep the grid operating at 50 hertz and at a stable voltage.
As a result, operators are seeking alternative methods to keep the grid balanced and to control voltage and frequency excursions.
The role of Demand Side Response
One approach to address these challenges is the use of Demand Side Response (DSR). With DSR, loads on the grid are typically reduced to match the available energy supply.
There is also growing interest in using DSR to deliver other so-called ancillary services like frequency and voltage response.
Indeed, according to the Association for Decentralised Energy (ADE), there is potentially a 9.8 GW market from DSR by 2020 in the UK industrial and commercial sector alone.
Large consumers of energy are ideally placed to provide this kind of flexibility. However, many businesses typically demand continuous power to sustain operations. One solution is the use of energy storage capabilities, such as batteries, to provide more flexibility.
Delivering flexibility with energy storage
“While battery technology and associated chemistries are still evolving, commercial energy storage is already a reality,” explains Dan Connor, DSR Development and Delivery Manager at Energy HQ, npower Business Solutions. “Certainly, the functionality and flexibility of a battery may be delivered by a number of different techniques.”
A battery is all about being able to store energy, but not necessarily electrical or chemical energy. It can be heat or cold, compressed air, a spinning flywheel or water in a pumped storage reservoir such as the 288MW Dinorwig plant in Wales, known as the Electric Mountain.
“While large-scale energy storage using hydropower is limited by geography, energy flexibility may be delivered from a wide variety of sources that can yield significant benefits for businesses,” says Dan.
“For example, a cold storage system may be able to successfully operate between -18˚C and -22˚C. By cooling the unit to the minimum -22˚C before a peak electricity pricing period, a business may be able to turn off cooling compressors and allow the system to warm up to the maximum -18˚C over a period of hours.”
By not consuming peak priced energy, the cold storage facility can utilise its inherent flexibility and in effect can operate as a battery.
“This kind of capability can not only save a business considerable sums on purchasing, but may also represent a secondary revenue stream by delivering DSR services for the grid operators, such as via National Grid’s range of Balancing Services,” continues Dan.
Choosing the right storage capabilities
Different energy storage technologies have different characteristics in terms of energy density, speed of response and their capacity or energy volume.
“This is typically defined as a C Rating – an indicator of the continuous discharge rate determined as the ratio of peak output in kW to the total storage capacity – and gives an indication of total discharge time at full capacity,” explains Dan.
The C-rating is also a necessary consideration in determining what type of applications or revenue streams are available to businesses using such storage solutions.
“For example, one potential benefit comes from load shifting and avoiding peak period charges,” says Dan. “Smaller cabinet battery solutions with a relatively low C rating could support this activity, or other approaches – such as using cold storage – that can provide energy over a two or three hour period.”
Larger units with higher C ratings are able to deliver cost avoidance benefits for businesses, but also revenue generation from supplying other ancillary services such as National Grid Firm Frequency Response.
Still larger systems like directly connected utility-scale batteries of 20 MW or more can play a role in frequency services or the wholesale marketplace.
“In each case, businesses looking to invest need to consider capex, financing and return on investment, as well as lifecycle issues,” advises Dan. “Chemical batteries, for example, have a finite number of charge and discharge cycles as the system degrades over time.”
Building a market for DSR
Storage functionality represents a growing opportunity in the power and ancillary markets providing balancing, voltage or frequency response services from DSR.
It is a market that is maturing rapidly as asset owners and the system operator get to grips with the potential benefits and revenue streams available from flexibility. And as we start to see more Distribution Network Operators transition to Distribution System Operators, we expect there to be more local DSR opportunities in the future.
Like renewables, battery storage technology is still rapidly evolving, but the commercial case for storage and DSR stacks up already.
To find out more about the suitability of using battery storage to support your business’s DSR strategy, contact the DSR experts at Energy HQ via [email protected] or call 0800 994 9382.
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