How inverters can stabilize a renewables-heavy grid. A conversation with Daniel Duckwitz of SMA Solar Technology and Catarina Augusto of SolarPower Europe. Volts David Roberts 5 Sept 2025 Today's electricity grids are kept stable by the inertia of spinning masses — mostly fossil fuel generators. But what happens when those spinning masses are replaced by inverter-based resources like wind, solar, and batteries? The answer is that inverters must take over the stabilizing job, becoming "grid-forming" rather than merely “grid-following.” I chat with two experts about how grid-forming inverters work, how many are out there, and what the future holds for them. And you're right, there is. In the seconds or milliseconds between when demand rises or falls on a grid and a grid operator is able to respond by adding or subtracting supply, the energy to buffer that transition and keep frequency and voltage under control is provided by inertia.
Specifically, almost every electricity generator involves a large spinning mass, rotating coils through a magnetic field. And there is kinetic energy in that spinning mass. Like a flywheel, that inertial energy can be tweaked very quickly. The mass can spin more quickly, thereby absorbing energy, or spin more slowly, thereby releasing energy, keeping the grid in balance in those key seconds. Collectively, spinning masses constitute a kind of shock absorber for the grid. Now here's the first: solar panels, batteries, and most wind turbines, the building blocks of tomorrow's energy system, do not connect to the grid via large spinning masses. Rather, they connect through inverters, which are all electronics. No moving parts, nothing spinning, no kinetic energy. Lacking inertia, inverter-based resources have not, to date, actively contributed to grid stability. In fact, there are widespread worries that replacing (primarily fossil fuel-based) spinning masses with clean inverter-based resources will leave grids with too little inertia, too little buffer, prone to accidents and breakdowns like what happened in Spain and Portugal recently. But here's the second twist. A modern inverter, properly programmed, can effectively mimic a spinning mass, adding or subtracting tiny increments of energy to the grid in milliseconds. This ersatz spinning mass provides what is called in the business "synthetic inertia." Inverters attached to batteries are best at this, for reasons we'll get into. But inverters on solar panels and wind turbines can contribute as well.
So the problem is solved and we can all go home? Haha, of course not. It is never that simple. To get into the details, I have with me today two experts: Daniel Duckwitz works on grid stability products for SMA Solar Technology, a large power conversion company based in Germany; Catarina Augusto is a renewable energy engineer who works on grids and flexibility for the nonprofit SolarPower Europe.
As you could probably tell from the lengthier-than-usual intro, this subject can get somewhat technical. But the larger issue we're circling around here could not be more simple and profoundly important: can we or can we not run a stable electricity grid on renewable energy?
All right then, with no further ado, Daniel Duckwitz, Catarina Augusto, welcome to Volts. Thank you so much for coming......READ OR LISTEN TO THE DISCUSSION.......
https://www.volts.wtf/p/how-