The MARI project is growing

The Manually Activated Reserves Initiative (MARI) project, which implements a pan-European market for the activation of manual restoration reserves (mFRR), was first launched on October 5, 2022. The MARI market belongs to a series of projects aiming at further integrating the European electricity market, not only at the day-ahead and intraday timescale, but all the way down to the balancing activation timescale. This brings further benefits to the European grid by optimising the activation of balancing reserves and create substantial gains, both economically and for grid security. 

These balancing services impose very challenging operational requirements to market operators, as auctions are run every 15 minutes or even every 30 seconds. This leaves very little time to run the algorithm in charge of optimizing the bid selection before sending results back to TSOs and market participants (and leave them enough time to ramp up or down). Given the large number of participants and the complexity of the grid at the European scale, this is no easy task.  

This is where Artelys’ expertise in mathematical optimisation and electricity markets came into play. Artelys has developed the market clearing engine behind MARI (also called Activation Optimization Function – AOF). The optimization function can be called up to every 30 seconds and shall return an optimized result within 15 to 60 seconds, while accounting for complex bid, network constraints, pricing rules, etc. You can find more details on our previous post we wrote for the launch of MARI. 

At the time of launch, the MARI market consisted of the four German TSOs and Čeps, the Czech Transmission System Operator. The market then expanded further in June 2023 with the integration of Austria.  

In the second half of 2024, this integration dynamic picked up with the go-live of several TSOs over the last several months: 

• APG (Austria) joined on June 22nd, 2024 
• The Baltic TSOs: Litgrid (Lithuania), AST (Latvia), Elering (Estonia) joined on October 10th, 2024 and also recently successfully synchronized with the Continental Europe electricity system 
• REN (Portugal) joined on November 27th, 2024 
• SEPS (Slovakia) joined on December 3rd, 2024 
• REE (Spain) joined on December 10th, 2024 

While the Baltic countries remain physically disconnected from the other MARI countries for exchanging balancing energy cleared on the MARI platform, Spain and Portugal can exchange with the central European countries thanks to sharing of ATC by the French TSO RTE since July 18, 2024. 

Geographical coverage of the MARI project as of January 2025 (taken from ENTSO-E website)

First results provided in the 2024 ENTSO-E Balancing report show the positive impact of the coupled mFRR activation market. The figure below, taken from the report, shows the monthly gains in social welfare of the coupled mFRR market compared to a decoupled scenario over the operational year 2023. 

Social Welfare gains from market coupling of mFRR  
(taken from p.45 of ENTSO-E’s Balancing market report 2024) 

After these encouraging developments, what’s ahead of us?

Let’s keep an eye out for Belgium, Bulgaria and Slovenia, which should be entering the market in the coming months, as well as the Netherlands and Poland by the end of this year. The latter will also connect the Baltic countries to the rest of central Europe where MARI is already operational.

More details about MARI can be found on ENTSO-E website and technical details about the functioning of MARI AOF are available in MARI AOF documentation.