The Evolution of Embedded Capacity Register in the UK From 1990 to 2024

Not so long ago, the sole role of the distribution network was to feed electricity from the transmission network down to consumers. Generation was centralised, with a handful of generators providing electricity for the whole country. Now we're seeing a dramatic shift where generators are embedded within the distribution networks.

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This data set showing the embedded capacity register shows over 19,000 connected or accepted to connect generators and storage within GB with a combined capacity of 210GW in 2024. This is in comparison to 423MW of embedded generation coming from 39 generators in 1990. Its extremely impressive what GB has been able to achieve especially with the substantial ramp up in solar and storage in the last 10 years. This is only expected to grow in order to hit the NESO 2030 clean energy targets that looks to increase the rate of deployed solar capacity per year by 3X by 2030 and the rate of onshore wind by 2X compared to 2023 levels. Of which 29% of onshore wind and 90% of solar capacities are connected within distribution networks.

Diverse and Distributed Generation: Solar leads the way among these new resources especially in the last decade, accompanied by biogas and wind generators, supporting a more diversified energy mix. The map also shows a substantial rise in storage capacity, a necessary addition to balance the variable output from renewable sources like wind and solar. Also note the increase in storage near centres of high demand as storage can closer to demand centres can provide more flexibility. Its not a coincidence that there are many big purple dots near London. This rise in storage and hence flexibility is for at least two reasons:

1. To time shift the energy generated by intermittent renewable energy to match fluctuating demand.
2. To provide grid stability. The grid is follows alternating current. Historically, when you have a few generators all with thermal generators spinning in sync, these created an intrinsic inertia in the grid to withstand sudden changes in frequency which come as a result of sudden fluctuations in supply or demand. Substantial deviations in frequency can have catastrophic consequences in terms of safety and infrastructure damage. Most embedded generators including renewable energy sources produce asynchronous DC power and do not contribute to inertia. Frequency can still be stabilised though with storage that can add or remove electricity from the grid on demand to stabilise frequency and other grid services. In other words things are getting a lot more complex requiring ‘smart’ solutions.

This shift in embedded generation comes with its challenges, of course. In short, balancing supply and demand becomes a lot more difficult with thousands of asynchronous generators. It requires sophisticated methods with different products offered by the various system operators and the wholesale energy markets in order achieve this harmony. In a competitive market, this means that prices for energy, anciary services and network maintenance all have time of use elements to them and can vary for periods as granular as 15 mins in GB . While it takes approximately 0.1kWh to boil your kettle and that energy can come from any source, the cost of boiling the kettle on the grid is impacted by the time you choose to boil it.

Some of the products offered by the different actors to try to balance supply and demand through price signals. Notice how all the products offered have a temporal element to them representing an attempt to incentivise demand to shift to when there is adequate supply and less pressure on the grid. See below for some of the services offered in GB, but similar products exist in other markets.

Its a lot to consider when planning an investment. Gridcog can help. We run an optimisation considering the unique price signals that each investment is exposed to showing you how to optimally operate your flexible assets in conjunction with distributed generation and on-site demand and what this means in terms of your investment's cashflows.

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