Doubters of the transition have always been quick to share doom scenarios about grids losing stability once wind and solar supplied a large share of their power. In the Energy Transition Show's early episodes, our host Chris noted how defenders of the status quo "have claimed for decades that the grid can't support more than 3 percent or 5 percent or 20 percent, it's a moving target, of variable renewables without risking blackouts…"
Years later, reality leaves transition skeptics less and less room to maneuver. So is there really an upper limit on how much wind and solar a grid can handle? In 2025, renewables provided more than 77% of South Australia's electricity generation, nearly half of it from wind. And for half an hour in April 2026, 98.8% of the power on Britain's transmission grid came from zero-carbon sources, by NESO's own measure.
Certainly along the way there have been blackouts blamed on renewables, such as 2016 in South Australia, or Spain and Portugal in 2025. If you only followed the headlines, you'd think the doubters had been right all along.
But grid engineers keep learning how to adapt, and the target keeps moving. In this episode of our documentary series, we start with conversations from the show's past and how they connect to recent ones about grid stability, including what the official investigation into Spain's blackout actually found, and how Britain gives its grid inertia without burning fuel.
Featured in this episode, in the order we hear their conversations, with titles as they were at the time of each recording:
- Paul Denholm, principal analyst at the National Renewable Energy Laboratory (now the National Laboratory of the Rockies), on Episode #58 (2017)
- Julian Leslie, Head of Networks and Chief Engineer at National Grid ESO, on Episode #174 (2022), and Director of Strategic Energy Planning and Chief Engineer at NESO, on Episode #245 (2025)
- Mackay Miller, senior analyst at the National Renewable Energy Laboratory, speaking in a personal capacity, on Episode #2 (2015)
- Jenny Riesz, Principal at the Australian Energy Market Operator, on Episode #39 (2017)
- Ivor Frischknecht, former CEO of the Australian Renewable Energy Agency, on Episode #71 (2018)
- Willie Phillips, Acting Chairman of the Federal Energy Regulatory Commission, at the commission's open meeting on Order 901, October 19, 2023 (“FERC Commission Meeting | October 2023 Open Meeting”). Source: Federal Energy Regulatory Commission. Public domain
- Leonhard Gandhi, Fraunhofer ISE, from the Energy-Charts Talk “Analyse und Bewertung des Stromausfalls in Spanien und Portugal am 28. April 2025” (1 April 2026). In German, with an English voice-over translation by XE Network.
- Professor Janusz Bialek of Imperial College London, interviewed by Dr Giordano Scarciotti on his YouTube channel, Prof Gio, in the video “Why Everyone Got Spain’s Blackout Wrong” (July 24, 2026)
- Wallace Kenyon, PhD candidate at the University of Colorado Boulder, affiliated with the National Renewable Energy Laboratory, on Episode #153 (2021)
- Guy Nicholson, Head of Grid Integration UK, Statkraft, from Modo Energy’s Transmission podcast, “Synchronous compensators, and Stability Pathfinders with Guy Nicholson” (2025)
- Kayte O'Neill, Chief Operating Officer, NESO, from Modo Energy’s Transmission podcast, “Connections, Capacity & Clean Power: Britain’s Grid Reform – NESO” (2026)
Thanks to Fraunhofer ISE’s Energy-Charts Talk, Giordano Scarciotti and his Prof Gio channel, and Modo Energy’s Transmission podcast for permission to use their clips. Every clip in this episode is used with permission, under license, or from the public domain.
Paul Denholm is a senior research fellow—the highest technical position at the National Laboratory of the Rockies (NLR), formerly the National Renewable Energy Laboratory (NREL)—leading research in grid applications for energy storage and solar energy.
When he first appeared on Episode #58 – Solar with Storage in December 2017, Paul was a principal analyst at NREL. Part of that conversation also features in Episode #286 – A Moving Target (2026). He returned for Episode #188 – Getting to a 100% Clean Grid in December 2022, as a senior researcher at NREL.
He pioneered a variety of research methods for understanding the technical, economic, and environmental benefits and impacts of the large scale deployment of renewable electricity generation. He has delivered over 100 invited presentations to agencies including the National Science Foundation, the World Bank, and the International Energy Agency. He has co-authored over 100 articles related to renewable energy integration. While his official title at the time of his first appearance was principal analyst, he is still an engineer at heart and in his free time he likes to build contraptions of dubious functionality, like a concentrating solar marshmallow cooker.
On the Web: Paul Denholm’s page at NLR
Julian Leslie is Director of Strategic Energy Planning and Chief Engineer at the UK’s National Energy System Operator (NESO).
When he first appeared on Episode #174 – Decarbonizing Britain’s Grid in June 2022, Julian was Head of Networks and Chief Engineer at National Grid ESO. By the time he returned for Episode #245 – Evolving the UK Energy System Part 3 in March 2025, he was in his current role at NESO. Parts of both conversations also feature in Episode #286 – A Moving Target (2026).
Julian is a chartered engineer with three decades of transmission system operation, planning and investment experience. Julian’s role is to prepare Great Britain’s electricity network for net zero operation, defining future network needs so that market and network owners can invest in the right technology solutions at the right time. Julian is also developing whole energy system plans on a national and regional basis.
On Twitter: @JulianLeslie6
On the Web: Julian’s profile at NESO
Mackay Miller is a Partner at ERM, where he leads the firm’s work at the nexus of energy and corporate strategy, with a focus on data centers, utilities, and financial sector clients.
When he first appeared on Episode #2 – Limits on the Grid – Part 1 in September 2015, he was a senior analyst at the National Renewable Energy Laboratory (now the National Laboratory of the Rockies), speaking in a personal capacity. Part of that conversation also features in Episode #286 – A Moving Target (2026). He returned for Episode #63 – Pathways to Deep Decarbonization in February 2018.
After NREL, he later served as Principal Analyst in the US Strategy division of National Grid.
On Twitter: @mackaymiller
When Dr. Jenny Riesz appeared on Episode #39 – Transition in Australia in March 2017, she was a Principal in the Australian Energy Market Operator’s (AEMO’s) Future Power System Security program, working on adapting AEMO’s processes and functions to ensure ongoing security and reliability as the power system transforms over the coming decades. Part of that conversation also features in Episode #286 – A Moving Target (2026).
Before joining AEMO, she was a research associate at the University of New South Wales, modelling energy markets for 100% renewable power systems, and a specialist in modelling renewables and climate policy at ROAM Consulting.
On Twitter: @jennyriesz
On the Web: https://jenny.riesz.com.au/
Ivor Frischknecht is Managing Partner at Sosteneo. He is a widely acknowledged expert and innovator in the energy industry.
When he appeared on Episode #71 – Australia at the Cutting Edge in June 2018, Ivor was CEO of the Australian Renewable Energy Agency (ARENA), where he led its efforts to accelerate the commercialization and integration of renewable energy into Australia’s energy system, as well as playing a leading role in transforming the electricity sector. Part of that conversation also features in Episode #286 – A Moving Target (2026).
Before joining ARENA, Ivor was responsible for clean tech investments at venture capital firm Starfish Ventures, which managed $400 million primarily on behalf of Australian pension funds, and served as CEO and investor in cleantech in Silicon Valley, California.
On Twitter (ARENA): @arena_aus
On the Web: Ivor Frischknecht’s LinkedIn profile
Dr. Rick Wallace Kenyon is Chief Product Officer at encoord.
When he appeared on Episode #153 – Grid-forming Inverters in August 2021, he was a PhD candidate at the University of Colorado Boulder focusing on power system dynamics under conditions of high penetrations of renewable, inverter-based resources, and he has since completed his PhD there. His primary interests were the frequency stability of these systems and the implications of inverter control techniques at various penetrations. Throughout his studies he maintained a strong affiliation with the National Renewable Energy Laboratory (now the National Laboratory of the Rockies), through which he developed a highly detailed electromagnetic transient model of the Maui power system for these near-future operating conditions. Part of that conversation also features in Episode #286 – A Moving Target (2026).
On the Web: Wallace Kenyon’s page at encoord
Recording date: October 25, 2026
Air date: October 28, 2026
Geek rating: 5