Could the World Safeguard Power System Reliability with 100% Renewable Energy?
The energy transition is now underway on a global scale. This transition takes many forms, but one of its main features is the increase in the share of intermittent renewable generation in the electricity mix. At the same time, demand for electricity is set to rise sharply over the coming decades. This is due not only to economic development, but also to the growing share of electricity in the energy mix, as a result of the energy transition, the emergence of AI and the proliferation of data centers.
This growth in demand, combined with the increase in the share of intermittent renewable energies, will require massive investment in generation, but also in power grids worldwide. This represents a major challenge to system operators and while no definitive technical answer has yet been found, political and societal choices must already be made.
Intermittent renewables like photovoltaic (PV) or wind generation represent a challenge to system operators
Variable renewable energy sources (VRE) such as solar and wind, being intermittent have an obvious consequence: solar output during the day can be reduced by clouds or mist, and wind is also variable during the day and depending on the time of year. Despite much progress, these variations are difficult to forecast accurately.
But the challenge is also due to more technical reasons, as the frequency of the grid varies on the interconnected network according to production or demand. In traditional generation (gas-fired, hydroelectric or nuclear power plants), the stabilization of the grid is achieved by rotating machines at constant speed. This rotation provides energy, also known as “inertia,” which automatically corrects any imbalance in the system's frequency. PV energy does not provide inertia, and wind turbines have variable rotation. When the share of PV or wind is small, this is a minor problem. Today, when PV or wind accounts for tens of percent of the electricity generated at any given time, the question of frequency stability becomes crucial.
Moreover, every MW of Greenhouse Gas (GHG) emitting plant must be replaced by 3 MW of intermittent generation to guarantee system reliability.
Our sector must also turn toward innovation and new solutions
Storage will play an important role in ensuring reliability. Among the emerging technology, battery energy storage systems (BESS) have now reached industrial maturity. As they store energy at times to feed it back at others, they are particularly welcome in high-volume photovoltaic energy systems. In the California ISO area, installed BESS have risen from 0.5 GW in 2020 to 12 GW in 2024, and the growth will continue in the years ahead. However, this is not a purely technical issue, and markets or development mechanisms are needed to attract new projects. Other disruptive technologies are emerging, such as new digital technologies or mathematical models to map energy production and consumption, and artificial intelligence will obviously be instrumental.
Scarcity of resources may jeopardize the required upgrade of power transmission systems
In its “Building the Future Transmission Grid” report of February 2025, the International Energy Agency evaluates that reaching national emission goals means adding or refurbishing a total of over 80 million kilometers of grids by 2040, the equivalent of the entire existing global grid. It represents an investment of about USD 600 billion per year over the next decade. Beyond the financial aspects, the world is experiencing a massive shortage of engineers and technicians, which is slowing down projects and actions.
Finally, raw materials are also in short supply. While lithium is obviously a critical challenge, basic materials such as copper are also sorely lacking. Copper reserves, so strategic for building new lines and reinforcing networks, are expected to be exhausted by 2070.
Regulatory issues are still slowing down or limiting our capacity to carry out major projects.
Many investment projects in new generation or power grids are experiencing increasingly long delays. This may be due to financial difficulties, supply chain issues or permitting delays.
The authorization processes are often too slow, leading to “zombie projects” (ie projects that were planned several years ago in a different economic and energy context, losing their coherence and pertinence over time). In the United States, even if the rules are currently evolving, the average waiting time to connect a project to the grid has risen from 1 to 6 years in just a few years. This number is even higher in some European countries.
Today, we must therefore focus on available manpower, raw materials and a new wave of network investment on a global scale. Industry leaders and key players need to communicate the urgency of the situation to political decision-makers and the wider public. This makes dialogue between government and the private sector more important than ever to develop an effective strategy and release the hundreds of billions of dollars needed to facilitate today's vital energy revolution in the best possible conditions.
