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Spinning Reserve Displacement with Batteries: Saving fuel, reducing emissions, lowering costs

image credit: © Leowolfert | Dreamstime.com

Everything benefits from a backup.

In professional sports, bench players step in to allow starters to catch their breath. Movie actors take a seat when stunt doubles take the stage. In such cases, primary and backup performers can combine forces to maintain continuity and enhance outcomes.

The energy sector is no different. Backups for energy systems traditionally are provided in the form of fossil fuel-based generators. But, unlike alternate players sitting on the bench, they don’t just come on when the going gets tough – they run all the time at a reduced capacity. This means they are ready to balance sudden changes in load or generation by providing so-called system services like frequency regulation, voltage control and blackstart capability. 

These fossil fuel resources remain on perpetual standby until called upon to support primary generators, making them a physically rotating spinning reserve. The only problem is that they run on expensive and carbon emitting fuels, constantly generating power even when the grid is already fully supplied by renewable sources. In some cases, this may even lead to a situation whereby renewable generation has to be kicked off the grid to make space for the so-called “must-run” spinning reserve capacity. Constant consumption of fossil fuels for standby generation through rotating spinning reserves also contributes to greenhouse gas (GHG) emissions.

However, a new technology has shown up on the field in the last decade which has the potential to take over the stage: battery storage systems. With their ability to provide grid services within milliseconds they replace spinning reserve generators with so-called “synthetic inertia,” in which the battery counteracts frequency variations, removing the need for constant fossil fuel-based generation, and providing a high degree of efficiency and stability.

This new model for providing system services doesn’t require burning excess fossil fuel. It also avoids the need to run generators based on a sub-optimal load point, resulting in lower costs of electricity and operations and management. In other words, it allows for the remaining generators to run at optimal load values, and therefore at higher efficiencies, while maintaining overall system availability and runtime through the resiliency provided by battery storage. 

A new spin on a traditional service

In the utility sector, a range of reliability demands are imposed by regulators. Perhaps the most significant is that there must be mechanisms in place to immediately accommodate the loss of the largest generator in its network with minimal interruption in service.

With the incorporation of batteries, a standalone power plant can be designed to maintain enough power and energy as reserves to allow the system to instantly meet contingency requirements that could arise from the sudden loss of a generator, a rapid change in load, or impacts from a fluctuating generation source (as is often the case with intermittent renewables, such as wind or solar generation).

Sizing matters

This technology can also make a massive difference at an industrial site or in a remote community. Simply put, when utilizing energy storage the system can serve the same load at higher efficiency and reliability and with fewer generators. If a generator were to trip offline, the battery would temporarily step in and replace the lost generation. In addition, the battery helps increase average loading of the generators, which improves the overall efficiency of the system, thanks to an upward shift on the generator efficiency curve. Such an approach results in considerable fuel savings, improved generator utilization, reduced runtime and operations and maintenance costs, and reduced GHG emissions.

A hybrid takes root in the Amazon

A prime example of how battery storage can provide spinning reserve displacement (SRD) is found deep in the Amazonas region of Brazil. Here, a fully integrated hybrid power system operating around the clock will serve multiple remotely located residential communities. With thermal generators as the primary power source, a 1 MW battery storage system provides the backup power for several of the sites. The provision of SRD by the battery system is fully automated and performed autonomously without operator interaction in normal operations. The battery is continuously available to provide power instantly should a generator trip off for any reason – and bridge the gap seamlessly while another generator comes online.

The battery also delivers significant fuel savings and other economic benefits. The addition of the 1 MW battery unit allows an increase in the average loading of the generators by 10%, which increases overall system efficiency by boosting generator efficiency and reduces annual fuel consumption by 1%. Runtime on the generators is also reduced by 11%, which will extend their operating life and reduce maintenance costs.

From jungle to desert

Another example of spinning reserve displacement on a larger scale is based on a 24 MW gas-battery hybrid power system at United Steel Industries’ Fujairah steel mill in the United Arab Emirates (UAE). The plant supplies 1.1 million tons of steel components annually to the construction and manufacturing sectors in the UAE and beyond.

United Steel is deploying a range of specialized mobile and modular power equipment on the site, including 13 gas generators, delivering 19 MW of primary power, and a 5 MW battery system. The battery system will displace the need for a spinning reserve to be provided by other generators and balance out sudden variations in the mill’s load.

Traditionally, these spikes would have been managed by diesel generators that run constantly at part load, consuming excessive amounts of fuel and impacting overall GHG emissions. Instead, this hybrid solution will deliver a 49% savings in fuel cost, while also significantly reducing the company’s GHG emissions.

Batteries and Benefits

Battery storage can be used at almost all generator-supported locations that require a significant amount of system services – especially remote communities and industrial operations. The result of this pairing is a range of tangible end-user benefits that include fuel and cost savings; improved generator utilization; reduced operating time and maintenance; and lower emissions. Such an approach is field-tested, environmentally friendly, and provides a high level of stability and performance.

Having a proven resource prepared and ready to step in to deliver a needed service provides continuity and efficiency – just as when an understudy seamlessly delivers lines to support a successful theatrical production. The beauty of different machines working together autonomously and in an integrated fashion by intelligent controls to deliver energy services to the end user, is akin to a symphony orchestrated by a conductor to deliver harmonious music.

Sriram  Emani's picture

Thank Sriram for the Post!

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