The green agenda has taken center stage in developed nations for over a decade, pushing transmission and distribution (T&D) issues to the back of the queue despite its importance. However, this dynamic is changing due to the growing gap between demand and supply which has seen an increase in eye-catching statements such as: “A return to 1970s era blackouts!” in the UK press, for instance.
Our view is that the green agenda may be pushing nations towards these energy gaps, along with a few other key issues. Our recent report looks at why that is, and what should be done to sustain growth and ensure the continuity of the energy supply whenever possible.
T&D grids around the world are buckling under escalating pressure which, in turn, places strain on those responsible for the support, management and regulation thereof.
The pressures on T&D grids broadly stem from the need to:
- build larger grids to cope with the continued increase in demand (greater in developing than developed countries)
- upgrade existing ageing grid infrastructure (greater in developed countries)
- upgrade from old structures and technologies to smart grids in order to meet new challenges faced by the transmission grid (renewables) and the distribution grid (distributed generation)
The high level challenges are, in principle, broadly the same for both grids. However, the detail of the solution differs between the two because they have different start points and fulfill different roles in the overall electricity supply chain.
Transmission grids are located close to the primary generation facility and handle massive amounts of energy which is dispatched along very long distances (typically hundreds of miles) across HVDC wires. The transmission grid is constructed as a true network, allowing for substantial redundancy in terms of the route that the supply may follow. It also creates a number of system anomalies, including transmission congestion and loop flow effects (energy overloads parts of a system by flowing back over parts of the grid through which it has already traveled).
The main challenge is to eliminate issues caused by the physics of transmission and the topology of individual grids, achieved at high level by increasing the grid size. This calls for cooperation between different regional grids, often crossing state or national boundaries in the process. As a result, financial and physical issues may arise as different operators attempt to manage the energy flow as transmission interacts with regulatory regime in a material way.
At the same time, the government encourages transmission system operators to change the profile of the electricity mix tcarried. In some instances, this leads to growth in the nuclear sector. More commonly, electricity generated from renewable sources is indicated and such sources tend to produce more intermittent electricity which may be less stable. In addition, grids may be more difficult to balance and manage.
The challenge for the distribution grid is similar to transmission in terms of the need to expand and carry more electricity to a growing number of end-users more effectively. Differences arise from the fact that the distribution grid usually carries smaller loads over a shorter distance and – crucially – that it has historically been built according to a radial or loop design. This design feature of the distribution grid is critical as it means that many, particularly older distribution grids, have been optimized for uni-directional flow from the centre outward.
Distribution grids were not built to switch electricity from location to location within the distribution grid. In addition to this, they are not designed to cope with locally -generated electricity (distributed generation). Rather, the grids are predicted to become a significant segment of the energy market over the next two decades, being fed upwards and potentially into the transmission grid where it will be traded alongside centrally generated outputs.
Transmission, Distribution and the Smart Grid
Smart grid is seen as a major part of the solution to the challenges of managing the transmission and distribution (T&D) grids. However, the implementation of smart grid will be very different between the T&D grids.
For T&D grids, “smart” involves:
- adding massive new sensing capability
- generating and communicating large amounts of data on the grid at any given time
- automating and remote control
At both T&D levels, the challenges are similar. The new sensing devices will produce a surplus of data which may threaten to overwhelm storage systems, as well as the efficient real-time assimilation and analysis of data. This is compounded by the fact that in order to make use of the new measuring systems, data needs to be communicated within the system at near instantaneous speeds which will minimize the amount of noise accompanying that data. Finally, data must be transmitted securely due to the growing risk to systems which may be caused by an internal error or cyber-attack.
While the drive to renewables is laudable and attainable, 20% of Germany’s electricity now comes from renewable sources. Regulators, policy makers and pressure groups need to take time to understand its effect on the T&D infrastructure and focus on solutions which will make this fit for purpose otherwise renewables will risk becoming the problem rather than the solution.