In a short space of time, Covid-19 has dramatically altered our way of life and its impact on the energy sector is only just beginning to be understood. We have already begun to see some of the short-term effects such as drops in electricity demand, which have led to higher percentages of renewable energy sources on the grid.
This unique situation has allowed many countries to experience a glimpse of what it will be like operating a high-renewable, low-inertia energy system. As such, this summer will provide a glimpse into the renewables-heavy future of the grid.
While the growth of renewables generation is undoubtedly positive, operating an energy system with a high penetration of renewables is a challenging task and the stability of many grids will be tested under these low-demand, low-inertia conditions. Crucially, these conditions have highlighted the need to question what can be done to prepare and support grids as they adapt to deal with the rapidly accelerating energy transition and prepare for the energy systems of the future.
Inertia is the physical force created by large, spinning pieces of metal — for example, turbines in gas, coal and nuclear power plants, which push electricity throughout the grid. Without it, electricity networks become unstable, increasing the risk of power outages. As renewables have become more prevalent, there are fewer such turbines and renewables cannot materially contribute to inertia, making the system less predictable.
Recent lockdowns around the world have exacerbated the day-to-day fluctuations in system inertia experienced by system operators as the fuel mix and nature of demand changes. Reductions in commercial and industrial activity combined with changes to working patterns due to working from home and unemployment have made power demand more diverse across the day, with the UK specifically experiencing a significant fall in demand across the morning peak of up to 20% — a trend reflected across Europe and the US.
Grids with higher renewables penetration are facing an increased challenging in managing inertia, forecasting and balancing supply with demand. The UK blackouts of 2019 and South Australia blackouts of 2016 are two major examples of the issues that can be caused by declining inertia, but the failure to understand and manage grid stability has broader implications for system operators, including having to curtail excess renewables production and incurring significant balancing costs — all of which increase the cost of effectively integrating clean energy.
However, the low-demand conditions offer a prime opportunity for grid operators managing their way through the low-carbon transition to understand the issues they are due to face in the coming years and develop solutions.
Fortunately, many progressive system operators have already begun preparing for these future scenarios. The UK’s National Grid recently held their first ever “inertia auction”, allowing companies to feed inertia into the grid without needing to simultaneously provide electricity, and last year signed an agreement with Reactive Technologies for the implementation of the world’s first real-time inertia measurement service.
Alongside improved forecasting and planning, with more accurate weather predictions and location of renewables facilities, inertia measurement will contribute to significant reductions in curtailment and balancing costs. This is because it tells grid operators exactly how much inertia they have at any given time, and thus means they can procure the required inertia in a precise and cost-effective way.
Solutions are being increasingly provided in a physical form with the use of synchronous condensers — motors used to adjust conditions on the transmission grid — to replace the inertia lost by a reduction in the use of thermal power plants. Batteries also offer potential opportunities with the “Tesla big battery” at the Hornsdale Power Reserve in Australia set to become the first to provide virtual inertia, and approximately 50% of South Australia’s inertia demand when required.
As regional and national governments continue to set ambitious net-zero targets, the grid systems upon which they will depend have been presented with a crucial insight into what a high-renewable energy system will look like and what challenges will have to be overcome to get there safely. Those system operators that have been proactively implementing solutions will not only fair better during the current spell of low-demand conditions, but will also be the most resilient and best placed to facilitate the future energy transition.
Chris Kimmett is director of power grids at Reactive Technologies, a UK-based provider of technology solutions for grid operators and renewable asset owners