Rationalising the way in which the grid is operated
Changing the energy mix is essential if we want to generate carbon-free electricity. However, it also poses other problems: the intermittent nature of renewables, their unequal geographical distribution and new uses of electrical power. RTE’s challenge is to accommodate these new means of power generation and consumption.
RTE is developing flexibility mechanisms to continue maintaining security of supply and electrical solidarity, both in France and across Europe.
While the increasing use of renewables is essential for generating carbon-free electricity, it also raises new issues: the intermittent nature of renewables, their unequal geographical distribution and new uses of electrical power.
In order to effectively accommodate these new means of power generation and consumption, RTE must come up with flexible solutions. These will enable it to maintain security of supply as well as electrical solidarity both in France and across Europe, whilst at the same time helping to meet the targets set for reducing greenhouse-gas emissions.
RTE’s challenge is therefore to upgrade its grid, enabling it to integrate a growing proportion of renewables while at the same time maintaining the same quality of supply and electrical solidarity across the regions.
Managing intermittent sources of power
The power generated by wind and solar facilities varies with the seasons and even within the course of a single day. The transmission system must become more flexible in order to cope with this variability.
The whole challenge entails rationalising power flows when solar and wind farms are generating at maximum capacity and conversely, offsetting their intermittence when their output drops. RTE is developing new flexibility mechanisms for the power system: demand-side response, storage solutions and adjustments to the grid. Some concrete examples are given below.
New-generation smart substations
These high and ultra-high-voltage substations can accommodate up to 30% more electricity from renewable energy sources. Fitted with optical fibres and sensors, they monitor real-time power flows and gather the data required for dynamically controlling the power system.
These substations are a world first and the result of a joint venture between RTE, major manufacturing companies (Alstom, ENEDIS, Schneider Electric, Alcatel Lucent) and the Neelogy start-up company, which developed the current-monitoring technology with the support of ADEME.
5 new-generation substations have been built in Brittany, Pays de la Loire and Provence-Alpes-Côte d’Azur.
A pilot storage project using virtual RINGO power lines
RTE is piloting a system of software-controlled batteries known as RINGO. The first battery absorbs the excess local renewable-energy output, which is simultaneously released by another battery located in an area that needs it.
With its 10 MW of storage capacity, tantamount to the output of 5 wind turbines, Ringo helps to prevent losses of renewable power and to curtail the construction of power lines.
Adapting to the new geography of power generation
Accommodating new energy sources within the new energy mix means having to consider their specific geographical location. Wind and solar resources are not necessarily located near high-consumption areas or near the existing grid, thus requiring new connections. Additionally, their output seldom matches local needs, meaning that excess power has to be routed to high-consumption areas (not only in France) whilst conversely, power deficits have to bridged.
The transmission system is an ideal tool for dispatching renewable power and for maintaining electrical solidarity at a local, nation-wide and European level. Differences in climate between southern and northern Europe will multiply long-distance exchanges.
Integrating marine power
Building on its experience acquired from the connection of onshore facilities, RTE is now using its expertise to connect offshore windfarms. The State has placed it in charge of the project. As soon as the offshore windfarm is built, the offshore electrical platform is included in the connection infrastructures managed by RTE. This reduces the risks for the generating facility, accelerates project completion and minimises their environmental footprint.
Off the coast of Saint-Nazaire, grid-connection work on the first offshore windfarm began in November 2019: 80 wind turbines and 480 MW of installed capacity, meaning that 20% of the electricity required by the Loire-Atlantique region will be covered by green energy sources as of 2022.
New forms of electricity usage
Smart buildings are now able to communicate with one another and with the grid in order to generate energy savings. Electric mobility is forging ahead: the number of electric vehicles tripled in France over the period of 2014 to 2016. Self-consumption and charge-control systems further illustrate these new forms of electricity usage, stimulated by high tech and the growing number of players: from traders to demand-side response aggregators through to the consumers themselves.
RTE is rethinking the way in which the grid is set up, traditionally revolving around a few key players. It is banking on a cocktail of flexible solutions and more specifically, on the modulation of power consumption. In France, the available demand-side response potential, i.e. the ability of some consumers to temporarily reduce their consumption, reached 2 650 MW in 2017, tantamount to more than two nuclear power plants.
Anticipate the development of electric vehicles
In France, the number of electric vehicles is expected to reach 15.6 million by 2035. This is good news for RTE: CO2 emissions reduced by a factor of 4 compared with a fossil-fuelled vehicle and annual fuelling costs reduced by a factor of 3, or even 5 with a charge-control system.
RTE sees the development of electric mobility as an opportunity for France’s power system, and is already preparing for it. It will require 48 TWh of power at most, tantamount to 10% of France’s consumption. The current system is therefore able to absorb it.
RTE could also capitalise on electric vehicle batteries and use them as an additional grid-management tool based on the RINGO model. In concrete terms, smart-grid vehicle batteries become storage units. They are able to supply the grid if there is a peak in demand and conversely, are able to recharge themselves if there is a peak in solar output, for example.