DALL·E generated image of a big flywheel with lots of inertia and lightning bolts, digital art

The Power Of Spin: How Old Mechanical Solutions Are Ensuring Modern Grid Stability

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About six years ago, I published a series on grid innovation. Recently, an article crossed my screen specifically about one aspect from that, ancillary services markets for frequency control, and I thought I’d check in a bit. Let’s start by summarizing the points I made then.

Ancillary services, as defined by the United States Federal Energy Regulatory Commission (FERC), are those that support the transmission of electricity and maintain reliable operations of the interconnected transmission system. This includes scheduling and dispatch, reactive power and voltage control, loss compensation, load following, system protection, and energy imbalance. These services provide new revenue opportunities that could be met by new providers or technologies not currently compensated for such.

Emerging technologies, such as modern wind and solar generation plants, now incorporate technologies that allow them to provide some of these ancillary services. For instance, utility-scale wind and solar farms have electronic components that allow them to match grid frequency and voltage, outperforming traditional physical assets like coal, nuclear, and hydro plants. Additionally, these renewable sources can readily meet load-following needs, quickly adjusting to the demand fluctuations. Furthermore, the flexibility of renewable energy sources allows them to meet the ever-changing energy needs of modern economies.

The evolution of the grid system towards digital and renewable technologies, however, presents certain challenges. Energy imbalance, for example, can be a concern with renewables due to the natural and predictable variation of energy generation. However, this issue is being addressed through regional markets that distribute the variance over a larger geography. As the grid continues to evolve, markets and proto-markets are emerging, offering innovations that might reduce administrative burdens and quicken response of both supply and demand.

A combination of technical, market, and regulatory innovation was ensuring that the grid remained reliable, but differently than it had previously. My assumption at the time that the electronic components would always out-compete mechanical ones, a truism I incorporated in my set of reasons why the future of all energy is electricity. For completeness, the full set of conceptual filters I applied were fungibility, ubiquity, loose coupling, electronics outperform the physical, human nature economics, and the future is already here. I use these premises as the positive perspective on the red flags questions I ask of new purported solutions and firms around their technologies, business models, and marketing to see how likely they are to be credible and viable.

But there have been two or three challenges to my assertion that electronics outperform the physical, niggling questions that are either exceptions that test the rule, or simply an indication that the set of truisms are simply guidelines as I intended them, not hard and fast rules.

Most obviously is my love of closed loop, off-river pumped hydro. That’s a very physical solution to a decarbonization problem, which is where to put energy when we have too much of it so that we can use it later when we have too little.

Projection of grid storage capacity through 2060 by major categories by author
Projection of grid storage capacity through 2060 by major categories by author

My projection of grid storage through 2060 has it continuing to dominate the space, as it has since 1907 when we built the first one. It has a lot of advantages, and there’s about 100x the resource capacity compared to global requirements, per the Australian National University global atlas. Certainly right now, lithium-ion cell-based batteries are going in with tremendous speed, but globally we’re still building less battery storage than the pumped hydro under construction. That said, recently an 8-hour storage requirement RFP in Australia had batteries coming out as the winner, a first globally. This is about the economic limit, per lithium-ion expert Nate Brinkerhoff, but it was reached more quickly than I expected.

I discussed this with Bent Flyvbjerg, global megaprojects expert, earlier in the year, and wrote at the time:

“I explored the example of grid storage with Flyvbjerg, as I’ve been very bullish on pumped hydro, and less bullish on cell-based battery storage. But one, batteries, is vastly modular, has a global supply chain and is easy to pre-assemble in TEU containers, shipped to sites, put on pads, and connected. Would the modularity of batteries trump the decoupling of power and energy and deep maturity advantage of pumped hydro? It’s been a niggling doubt for me.”

I’m not at the point where I’m changing my projection, as I expected cell-based batteries to dominate a lot of grid storage through 2030 simply because the low-hanging fruit was shorter duration storage, with longer duration storage being an end game requirement. But it’s an interesting question I’m tracking, along with other ancillary services. I was discussing pumped hydro just the other day with a multi-billion dollar infrastructure investment fund, and will be having dinner with a Scottish pumped hydro and battery storage developer in Glasgow in a week around the maritime decarbonization debate — batteries and biofuels dominate my projection through 2100 — that a Scandinavian shipping concern is flying me in for, so I continue to engage in the space.

Locations of current, planned and in construction HVDC projects globally from Open Street Maps
Locations of current, planned and in construction HVDC projects globally from Open Street Maps

Another technology I’m very bullish on is high-voltage direct current transmission. As I continue to say, HVDC is the new pipeline, and strategic energy interdependence between jurisdictions will be balanced with electricity transmission through HVC with hedged redundancy. And yet, and yet.

As I pointed out in 2017, HVDC only became scalably viable when ABB licked the breaker speed and resilience challenge in 2012. Electronic-only breakers were fast enough, but not robust enough, while mechanical breakers had the opposite problem. Hybrid breakers became the solution, and sharp eyes will note that they aren’t purely electronic, but that’s true of all energy in one way shape or form. Does it challenge my thesis? Maybe.

And now, frequency control on grids is the latest area where my thesis might be being challenged with a physical solution.

Inertia is a key aspect of legacy power grid operation and plays a crucial role in frequency control. In the context of a power grid, “inertia” refers to the energy stored in large rotating masses, such as generators or industrial motors. When power demand and supply are in balance, the grid operates at a stable frequency, typically 50 or 60 Hz.

When there’s a sudden change in the grid, such as a sudden loss of generation (for example, if a large power plant unexpectedly goes offline) or a sudden spike in demand, the frequency of the grid can start to deviate from its nominal value. This is where inertia comes in. The stored rotational energy in the large rotating masses can be used to compensate for this sudden imbalance and keep the frequency stable. This stored energy can be released or absorbed to provide an immediate but temporary response to these changes, giving the grid operator a few crucial seconds to bring additional resources online or to shed load and restore balance to the grid.

As I said in 2017 in the series, ancillary markets for inertia would emerge, and these would allow electronics related to asynchronous or direct wind and solar assets to bid on them, as well as legacy generation technologies such as nuclear and hydro, with their large synchronous turbines. That projected future is here now.

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Per T&D World, in response to the declining inertia in the power grid due to the rise of renewable energy sources and energy efficiency technologies, the National Grid Electricity System Operator (NGESO) in the UK has created a market for inertia services. This market was initiated with the launch of NGESO’s Stability Pathfinder project in January 2020.

Through this project, NGESO has awarded contracts worth around $400 million over a 6-year period to various parties, including Statkraft, for providing inertia and other stability services. The idea is to procure services that maintain the grid’s stability without delivering extra electricity onto the grid, thus allowing more renewable generation to operate, and ensuring system stability at lower costs.

The first phase of the project is set to procure 12.5 GJ of inertia, equivalent to the inertia provided by about 5 coal-fired power stations. This initiative is anticipated to save consumers up to $158 million over the 6-year period, though the actual savings could be higher considering the surge in gas prices.

And one of the first projects to tap into this market is mechanical more than electronic, Statkraft’s Greener Grid Park Project in Liverpool, featuring ABB’s high-inertia synchronous condensers coupled with a flywheel. A bit of electricity from the grid keeps the flywheel spinning, and when grid frequency changes, the flywheel’s inertia helps keep it within tolerances. These condensers, once commonplace in the power industry, are seeing a resurgence as they offer a range of stability services, including inertia support for frequency stability, fault level contribution, and voltage regulation. Furthermore, their design allows for redundancy and system availability while providing a cost-effective means of maintaining system stability. The Lister Drive Greener Grid Park project will contribute to around 1% of the UK’s projected minimum total inertia requirement for 2025, marking a significant step in the right direction.

There’s ABB again, and again providing a physical solution, not a purely electronic one. It provides fully electronic ones as well, but if it spec’ed this old synchronous condenser technology for this project, it’s because it was completely fit for purpose.

The combination of technical, market, and regulatory innovation sometimes brings old technical solutions back to life. Such is the case for synchronous condensers, it seems. It will be fascinating to watch power engineers dig into dusty toolboxes and rusted warehouses to uncover more solutions like this one in the coming decades.

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Michael Barnard

is a climate futurist, strategist and author. He spends his time projecting scenarios for decarbonization 40-80 years into the future. He assists multi-billion dollar investment funds and firms, executives, Boards and startups to pick wisely today. He is founder and Chief Strategist of TFIE Strategy Inc and a member of the Advisory Board of electric aviation startup FLIMAX. He hosts the Redefining Energy - Tech podcast (https://shorturl.at/tuEF5) , a part of the award-winning Redefining Energy team.

Michael Barnard has 747 posts and counting. See all posts by Michael Barnard