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Battery energy storage systems for black start capability

Posted to Siemens Energy in the Generation Professionals Group
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Thorben Fohrmann's picture
Strategic Analyst for Energy Storage Siemens Energy

Unleashing the potential of energy storage and helping customers to master the energy transition

  • Member since 2021
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  • Nov 15, 2021
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Power plants are under constant pressure to provide a supply of energy – continuously, in flexible operation or on demand. This means dealing with frequent fluctuations in demand and handling major incidents such as blackouts. When a severe failure in the power network occurs, black starts are key to getting things back up and running.

 

For many years, the responsibility for carrying out successful black starts has rested largely with diesel generators. These machines remain an important component of a resilient power plant, given their track record in delivering during emergencies and the fact that the technology underpinning them is well established. However, diesel generators do have some notable limitations, the principal disadvantage being their reliance on fossil fuels to operate and the required maintenance efforts. In an era where clean energy and decarbonisation are the order of the day, leaning too heavily on diesel can be problematic.

 

For this reason, companies operating power stations need an alternative when it comes to black start capability. This is where battery energy storage systems (BESS) have a major role to play. It is relatively new in the energy industry, but it is also growing rapidly in popularity. With the global BESS market estimated to be worth $13.9 billion by 2026 (up from just $2.7 billion in 2020) it looks set to figure prominently as we strive towards building a lower-carbon world.[1]

 

When an outage occurs and a black start is needed, battery energy storage systems can deliver the boost that power stations need to get turbines back up and running, thereby minimising the effect on consumers, businesses, and public services. They can also enable a plant to enter island mode when a facility needs to go off-grid by absorbing excess energy. Effectively, BESS can carry out the role of a diesel generator reliably and safely, but without the carbon footprint and with many extras on top.

 

BESS has numerous advantages – it provides a clean, consistent source of capacity or power that adds no carbon emissions. It also gives power plants an extra option when it comes to responding to fluctuations in demand. For example, battery storage can be used to temporarily increase a turbine’s maximum power output when spinning reserve is needed. This can be crucial when a facility is tasked with delivering extra supply to the grid in the event of a blackout elsewhere. BESS is also very flexible, as it can be used in conjunction with steam turbines, gas turbines or combined cycles, and can be installed in both new and existing power plants. And finally, it ensures stability, by delivering immediate, stable load changes even without grid connection or stable transmission. This means black starts can be carried out without delay whenever needed.

 

Making energy generation cleaner, more reliable, and more sustainable is one of the most pressing goals of our time. The impact of climate change is undeniable, but a rapidly growing global population means we will retain our insatiable desire for electricity. To keep disruption to an absolute minimum in the coming years, having the right black start capabilities in place is paramount.  There are many ways in which energy providers can achieve this, so it is important that leaders explore all the options available to them. Battery energy storage systems deliver many advantages that the industry has lacked for many years, so it is likely they will become a fixture in power plants across the world as businesses, governments and individuals work towards building a brighter future.

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Matt Chester's picture
Matt Chester on Nov 15, 2021

Making energy generation cleaner, more reliable, and more sustainable is one of the most pressing goals of our time. The impact of climate change is undeniable, but a rapidly growing global population means we will retain our insatiable desire for electricity. To keep disruption to an absolute minimum in the coming years, having the right black start capabilities in place is paramount.

These are the base facts we're all operating under, and they're so important to recognize. How do you think these type of systems apply to the developing grids across the world? While modern, developed regions worry about the interruptions, many places are trying to get access to energy for the first time. Can these solutions come into play there as well? 

Roger Arnold's picture
Roger Arnold on Nov 15, 2021

I'm no expert on issues of black start and fault clearance, but I'm pretty sure that carbon emissions from diesel-powered generators used in such situations are not a credible concern. Grid crashes that lead to the need for black starts are exceptional events. They can happen, and the system must be able to recover from them. However, if it only meant running diesel generators for a few hours every ten years, the carbon emissions would be a tiny fraction of what's emitted in one good sized forest fire.

 

On the other hand, perhaps it's a matter of "Hey, we've got these big battery banks that we need to cope with the intermittency of wind and solar resources; couldn't we adapt them to handle black starts and scrap these old diesel generators"? 

 

I imagine the answer is yes. And it probably makes both technical and economic sense. But it might not be entirely straightforward. I've corresponded with power system engineers who insist that batteries cannot be used for black starts and fault recovery. The problem is that they don't supply true rotational inertia. Their power controllers can be designed to supply a degree of synthetic inertia for handling small load fluctuations. That's good for frequency regulation. However they can't handle the large surges and heavy transient loads that arise when restoring power to a region after a blackout.

 

As I say, I'm no expert in this area. It does seem to me, however, that rotational inertia could be handled through use of battery banks for the energy to spin up synchronous condensers. I'd love to see followup from anyone who knows more than I do about this.

Jim Stack's picture
Jim Stack on Nov 16, 2021

Battery storage is very good for Black Starts and even preventing a Black start being needed. Battery storage can keep the power from having a Brownout or Blackout since they are available in milli seconds. They have the GRID more efficient and pay for themself. 

Roger Arnold's picture
Roger Arnold on Nov 17, 2021

I demur. Battery storage may sometimes be good for black starts and even preventing a black start from being needed. But only if the battery bank carries sufficient charge at the time the contingency event occurs. If it occurs at a point when high load conditions or low output from renewables has depleted battery charge, the batteries won't help. And if you've already scrapped the diesel backup generators, what then?

 

Of course, one could propose an operational policy in which battery banks are never allowed to fully discharge under "normal" operation. The idea would be to always maintain a reserve capacity sufficient to ride through contingency events or supply power for a black start in the event that the contingency event led to a grid crash that the reserve capacity wasn't able to prevent. That would be an exceedingly costly policy, however. It's equivalent to purchasing and maintaining a battery bank of size equal to the set-aside reserve, and never using it except for contingency response. Batteries are currently way too costly for that to be economically justified. 

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