Can We Run a Grid Entirely On Renewables?

The short answer is yes...but it’snot quite that simple.

As the world races toward net zero, the question “Can we run a grid entirely on renewables?” is no longer theoretical. With wind and solar now dominating new power installations, grid operators and policymakers must grapple with the real-world challenges and opportunities of a clean, reliable, and affordable energy system.

The answer, is yes...but only with careful planning, flexible technology, and a pragmatic approach to grid stability.

How the Modern Grid Works

The electricity grid is a complex, interconnected network designed to deliver power where and when it’s needed. It consists of:

• Generation: Power plants (historically coal, gas, nuclear, hydro; increasingly wind and solar) that produce electricity.
• Transmission: High-voltage lines that move power across regions.
• Distribution: Local networks that deliver electricity to homes and businesses.

Grid stability relies on maintaining a constant frequency (50 or 60 Hz depending on where you are in the world).

The reason is that supply must balance demand in real time, if we all put the kettle on at half time, then the demand on the grid goes up. This increase in demand shows up by putting more strain on the turbines that are spinning in power stations making them slow down marginally. This slow down reduces the frequency, which is an indication for the grid managers to add in extra power from another power station.

With half time over and cuppas in hand, the demand drops and so those turbines have a little less demand on them and so they speed up marginally and the frequency increases, indicating that demand has dropped and so the extra power can be stood down.

Traditionally then, this stability has been provided by the inertia of large spinning turbines in fossil-fuel or hydro plants, which help buffer sudden changes in supply or demand.

The Renewable Revolution: Benefits and Challenges

Renewables are now the fastest-growing part of the global energy mix, driven by policy, economics, and climate goals.

They are clean, increasingly cost-competitive, and can be deployed at scale. However, their variability-dependent on weather and time of day-creates new challenges for grid stability.

The Inertia Problem

Wind and solar connect via inverters, which lack the stabilizing inertia of spinning generators. As renewables replace traditional plants, the grid can become more sensitive to frequency fluctuations and sudden changes in supply or demand.

Mismatched Supply and Demand

Solar peaks at midday, while demand often surges in the evening. Without storage or flexible backup, excess energy during the day can be wasted, and shortages can occur at night.

Real-World Example: Texas 2021

In February 2021, Texas suffered a catastrophic blackout during a severe winter storm. Over 4.8 million customers lost power, some for days, and at least 246 people died. The crisis was primarily caused by a failure to winterize natural gas infrastructure, but it also exposed the risks of inflexible generation and lack of grid resilience.

Solutions for a Stable, Renewable-Powered Grid

1. Advanced Energy Storage

Battery energy storage systems (BESS) store excess renewable energy and release it when needed. They provide rapid frequency response and are essential for short-term balancing, but current technology is best suited for durations of minutes to a few hours.

2. Synchronous Condensers and Grid-Forming Inverters

Synchronous condensers are spinning machines that provide inertia and short-circuit current, stabilizing the grid without generating electricity. Grid-forming inverters can mimic these effects, allowing renewables and batteries to “form” the grid and maintain frequency.

3. Flexible Gas Engines and Marine-Inspired Reciprocating Engines

Modern flexible engines, especially those based on marine technology, are crucial for balancing renewables. Unlike traditional gas turbines, these engines can start and stop within minutes, run efficiently at partial loads, and operate on a variety of fuels-including natural gas, biogas, and hydrogen.

Key Advantages:

• Rapid start/stop: Engines can reach full load in minutes, compared to 5–8 minutes for gas turbines.
• Minimal minimum up/down time: Engines can be cycled quickly, while turbines require longer intervals.
• Low minimum stable load: Engines can operate down to 10% of capacity, compared to 40–50% for turbines.
• Fuel flexibility: Modern engines are being certified for 100% synthetic and carbon-neutral fuels, including hydrogen and methanol
• These engines can also provide grid stability services, such as inertia and short-circuit current, by operating as synchronous condensers when not generating electricity.

This flexibility means that a relatively small amount of engine capacity (often 20–25% of grid capacity) can provide essential backup and stability services, while only supplying 2–4% of total electricity over the year.

This approach avoids “locking in” fossil fuels, as these engines can transition to zero-carbon fuels as they become available.

The 90–95% vs. 100% Renewables Debate

Modelling by Wärtsilä and others shows that achieving 90–95% renewables is technically and economically feasible with today’s technology, especially if flexible engines are included. Pushing to 100% renewables, however, becomes exponentially more expensive and complex, requiring massive overbuilding of renewables and storage or the use of emerging solutions like green hydrogen.

Wärtsilä’s Crossroads to Net Zero report estimates that supplementing renewables and batteries with a modest amount of flexible engine power plants can reduce system costs by up to $65 trillion globally by 2050, while cutting CO2 emissions by over 20% compared to a renewables-only approach.

Flexible engines also dramatically reduce renewable curtailment (wasted energy, not using the energy from solar or wind as there is no demand for it at the time it is produced), making the system more efficient and affordable.

Beyond Generation: Smart Grids and Demand Response

A renewable-powered grid also relies on:

• Smart grid technologies: Real-time data and AI optimize electricity flows, predict demand, and enable two-way communication between utilities and consumers.
• Vehicle-to-grid (V2G): Electric vehicles can act as distributed storage, giving power back to the grid during peak times. Octopus energy claim to be able to already do this with 5% of the UK’s EV fleet.The effect is to have the equivalent of 1.5 Nuclear powerplants on tap - at 100% UK EVs, this is up to 30 Nuclear power station equivalents on standby.
• Home, Microgrids and distributed energy resources:Home or localized grids and decentralized renewables boost resilience and can operate independently during outages.
• Demand response: Smart meters and IoT devices enable consumers to shift usage in response to grid needs, smoothing peaks and valleys in demand.

Global Lessons: Pragmatism, Not Absolutism

Countries like the UK, Ireland, and Chile are already demonstrating how a pragmatic, flexible approach can enable high renewable penetration while maintaining stability. For example, replacing inflexible coal with flexible engines in Chile cut fossil energy from 25% to just 4% of total electricity, dramatically reducing emissions and costs.

In Finland, flexible engines running just 3% of the time provide backup for a grid dominated by wind, hydro, and nuclear.

Conclusion: The Path to Net Zero Is Flexible, Clean, and Reliable

The transition to a zero-carbon grid is not about picking technological winners or adhering to ideological purity. It’s about building a system that is clean, affordable, reliable, and resilient. That means embracing renewables, but also investing in flexible, future-proof backup-especially advanced engines that canin the long run, runon zero-carbon fuels.

In summary: We can run a grid without fossil fuels, but only if we plan for flexibility and invest in the right mix of technologies. The grid of tomorrow will be cleaner, smarter, and more resilient-powered by innovation, not inertia.

For more insights on the future of clean energy and climate solutions, visit climatemarketinglab.org.

Citations:

YouTube: Can You Run a Grid Entirely on Renewables? Ep208 – Cleaning Up

Wärtsilä: Three reasons engines are driving the energy transition

EBSCO: 2021 Texas power crisis

1898 & Co.: Stability Challenges in Grids With Large Penetrations of Renewables

Michael Liebreich/LinkedIn: Can You Run a Grid Entirely on Renewables?

Michael Liebreich/LinkedIn: Flexible gas generation and grid stability

Wärtsilä Annual Report: Engine power plants and fuel flexibility