Dutch 800 MWh battery uses flexible grid connection

The approximately €180 million project will connect to TenneT’s Meeden substation under a Time-Dependent Transmission Rights agreement, or TDTR.

Commercial operation is expected in the fourth quarter of 2027.

The battery receives capacity for at least 85% of the time

TenneT’s TDTR model gives connected customers transport capacity for a defined number of hours each year, with capacity available for at least 85% of the time.

During the remaining period, TenneT can partially or fully restrict import or export when the transmission network is under greater pressure. Restrictions are communicated in advance.

For Sirius, that means charging and discharge can be scheduled around available grid capacity instead of requiring a firm connection that guarantees full transport capacity at every hour.

Flexible connections make use of capacity outside network peaks

TenneT developed TDTR to make greater use of spare transmission capacity outside peak periods in areas where new firm connections are difficult to obtain.

The arrangement does not remove grid congestion. TenneT is explicit that grid reinforcement is still required, but flexible customers can sometimes connect earlier without adding demand during the most constrained periods.

That works particularly well for assets such as batteries because charging and discharge can be moved in time.

The same principle is relevant to high-power charging

Large EV charging hubs are often designed around a requested grid connection as though that capacity will be continuously available.

Flexible or non-firm connections create another option: a site may be able to install substantial charging capacity while accepting that its permitted grid import is reduced during certain periods.

For EV charging, that would require the site to respond operationally through load management, battery storage, charging reservations, reduced charger output or a combination of these measures.

A multi-MW hub does not necessarily need a grid contract that guarantees its theoretical maximum charger demand at every moment, provided the operating model can tolerate restrictions.

Sirius combines commercial and grid flexibility

Under the long-term tolling agreement, Vattenfall will decide when Sirius charges and discharges and will pay Return a fixed fee for access to the battery’s capacity.

Return says the project is financed within a wider battery portfolio facility of up to €400 million involving five banks.

Sirius is a battery-storage project rather than an EV charging development, but the connection model is directly relevant to how future high-power charging sites could be integrated into congested networks.