Much of the energy-harvesting research published in Nature Energy relates to a few leading technologies, such as photovoltaics, reflecting their key role in advancing fundamental research and developing new solutions for sustainable energy. This emphasis contrasts somewhat with the current global energy mix, where hydropower remains the largest source of low-carbon electricity, followed by nuclear power. Wind and solar are growing rapidly but still generate less electricity, though the gap is narrowing.

Nuclear energy’s share of global electricity generation has declined over recent decades, largely owing to aging plants, slow deployment of new reactors, and growing competition from other low-carbon sources. However, the sector is experiencing renewed interest, driven by energy security concerns, supply–demand challenges, climate goals, and advances in engineering and technology. Global nuclear power generation is expected to increase in 2025, supported by reactor restarts, maintenance completions and new plants coming online worldwide1. Over 70 gigawatts of new capacity are currently under construction, and more than 40 countries are planning to expand their nuclear programmes. This momentum suggests nuclear energy could continue to play a significant role in the global energy transition.

Within the nuclear landscape, fission is the established technology supplying much low-carbon power today. Fusion offers long-term promise for abundant, clean electricity with minimal waste. One leading approach — plasma confinement in reactors such as tokamaks — aims to replicate the processes that power stars. Projects like the International Thermonuclear Experimental Reactor are working toward this goal, aiming to produce more energy from fusion than is needed to sustain the reaction. Nevertheless, major engineering hurdles remain, particularly in stabilizing plasma, managing extreme temperatures, and safely removing excess heat from the reactor2.

One of the biggest challenges is handling the heat that escapes the plasma. This heat can severely damage the reactor walls if not carefully controlled. To prevent this, scientists and engineers inject extra fuel and gases to cool the plasma and create a buffer zone that shields the reactor’s inner walls. But balancing wall protection while sustaining the fusion reaction is complex, and current systems often struggle to respond quickly enough.

One experiment designed to address this challenge is the UK’s Mega Amp Spherical Tokamak (MAST)-Upgrade. It features a specialized system known as the Super-X Divertor, part of a broader class of designs called advanced alternative divertor configurations (ADCs). Simply put, this design spreads the escaping heat over a wider area, easing extreme thermal loads and reducing damage to the reactor’s inner walls. While early results under steady conditions have been encouraging, the system had not yet been tested under more demanding, reactor-like scenarios.

In this issue of Nature Energy, an international team of scientists and engineers reports successful real-time control of heat exhaust using ADCs3. By combining advanced imaging with data analysis, the team was able to monitor the plasma edge — the critical region where most of the heat is released — and adjust the cooling gas flow on the fly to help manage it.

Their results also demonstrate that ADCs provide not only reliable, real-time control but also protection against sudden heat surges — intense bursts of thermal energy that occur during power spikes, which is crucial for shielding reactor walls. The system further enables near-independent operation of the upper and lower divertors (components managing heat at both ends of the reactor). This added flexibility is essential for future fusion reactors, which are expected to face uneven heat loads. Together, these advances mark an important step toward realizing compact fusion power plant concepts — such as the UK’s Spherical Tokamak for Energy Production and the US-based Affordable Robust Compact design — where safely managing extreme heat in limited spaces is a key engineering hurdle.

While MAST-Upgrade focuses on heat exhaust, other efforts address different fusion bottlenecks. Researchers at TAE Technologies have developed a way to start and maintain a type of fusion plasma called a field-reversed configuration (FRC)4. Unlike conventional methods relying on complex magnetic fields this technique uses neutral beam injection to form and sustain a stable FRC. Compact and high-power relative to their size, FRCs could simplify reactor design and accelerate the development of practical fusion power.

These advances highlight the essential role of engineering in bringing emerging energy technologies closer to reality. While fundamental science lays the groundwork, it is system-level innovation that enables progress toward reliable, scalable applications. At Nature Energy, we aim to showcase both foundational research and the engineering breakthroughs that move the energy transition forward.

Fusion holds long-term promise, but it is just one part of a much broader effort toward a sustainable and resilient low-carbon future — and its practical contribution remains uncertain. The broader transition requires a diverse mix of energy sources — including hydropower, nuclear, wind, solar, bioenergy, geothermal, and others — each playing a distinct role in meeting our energy needs. Equally important is improving not only how we produce, distribute, store, and use energy efficiently, but also the economic, social, and political frameworks that govern its management and deployment. Innovation across these dimensions is essential for building a balanced, reliable energy system capable of meeting global demand — a challenge that Nature Energy continues to report on.