TenneT answers TDTR questions from industry
TenneT recently explained the implementation of the TDTR in an online webinar (time-based transportation law). This included a discussion of available residual capacity and some questions from developers. The storage sector appreciates the public explanation, but at the same time is left with questions that have not yet been adequately addressed. To provide the sector with information, ESNL has bundled the questions as much as possible. TenneT's responses are below.
Is it true that over 2 GW of the 9.1 GW of residual space found has already been allocated, leaving about 7 GW to be allocated in this iteration of the residual space calculation? How often do these iterations take place?
Indeed, this first set of iterations identified 9.1 GW of residual space of which 2.3 GW has indeed already been forgiven.
Iterations take place until there is no more TDTR capacity to give away, or until there are no more interested parties for the remaining available TDTR capacity. A future iteration only makes sense if profiles of existing customers on the grid change substantially and/or if grid reinforcements are put into operation that are not already factored into the currently calculated results. No new iterations are therefore anticipated in the short term. It is therefore not to be expected that additional TDTR capacity will be forgiven in the short term. It is possible, however, that parties currently eligible for TDTR space may decline the offer, after which that space will become available to the next on the waiting list.
The webinar talked about both FCFS and social prioritization in determining the order of treatment. This can create contradictions and, moreover, cannot be implemented until it is clear who qualifies as a congestion mitigator. So how does TenneT make this consideration in practice, and what does this mean for parties that do not (yet) qualify as congestion easers?
Recently, the ACM decision for social prioritization was annulled by the Trade and Industry Appeals Tribunal. Until the end of the current year, this annulled framework for social prioritization is still valid. The framework includes three categories that can be allocated transport capacity with priority.
Of particular relevance to the TDTR discussion is the category of "congestion reliever." In the case of parties that have registered themselves as congestion relievers at an earlier stage, TenneT assesses the extent to which these parties meet the criteria of congestion relievers. Relevant here include the location of the asset, the commissioning date, the capabilities of the asset and the conditions for providing congestion management services that TenneT and the applicant can agree on. This determines whether these parties actually qualify as congestion sitters. "Congestion sitters" are thus given priority subject to actual qualification as congestion sitters. Should it turn out that they do not qualify as congestion sitters after all, they will lose their priority, after which the TDTR capacity will still go to the next on the waiting list.
How are applicants for transmission capacity who receive and accept a TDTR offer for part of their application, but do not yet receive an offer for part of it? Will they then be returned to the bottom of the waiting list for that second portion?
No, in the event that the full transmission capacity is not available at the time of application, the applicant retains his place on the waiting list for the remaining capacity.
The webinar stated that TDTR can only be entered into in conjunction with a CBC and bid obligation contract. Looking at the grid code, intraday obligations could be met through redispatch bidding. Why has it now been chosen to link a non-congestion product (TDTR) to these congestion products? And does TenneT also plan to do this for connected parties in non-congestion areas?
Based on Grid Code Article 9.1, TenneT requires connected parties to enter into a CBC and bid obligation contract, regardless of whether a connected party has a firm or an alternative transmission right. TenneT considers connected parties that use TDTR power to be flexible (for the share of TDTR in the contracted transmission capacity) and therefore also able to make their power available, for a fee, by means of a CBC and mandatory bid contract.
TDTR calculations contain assumptions about use of transportation capacity. There are inherent uncertainties in these assumptions. As a result, there is a risk that in a given year TenneT may nevertheless need the connected party's flexibility more than 15% of the time. For that matter, conversely, TenneT may also need this flexibility less than 15% of the time.
Through the CBC and the bidding obligation contract, TenneT hedges the risk of higher required deployment. This makes the risk no longer a physical risk (physical overload of infrastructure), but a financial risk for TenneT. The connected party receives fair compensation for its additional flexibility through the CBC and or redispatch bidding.
How are BESS profiles included in the calculation of the load duration curve? Does this differ between iterations, such as when in the first iteration a BESS accepted a TDTR offer?
When determining the load duration curve, for determining the available TDTR power, the profile of the applicant for TDTR power is not taken into account. In accordance with Grid Code Article 7.1c, the profile of the applicant is in fact not important for the amount of available TDTR capacity.
If TDTR power has been issued, a profile is assumed for that issued power, however, to determine the TDTR power remaining thereafter (second iteration). For standalone BESS, a profile of maximum feed-in and offtake at any time is adopted. TenneT chose this profile because it currently best reflects current insights into the behavior of batteries. However, it is expected that in the future batteries will increasingly exhibit behavior more similar to that which can be predicted on the basis of day-ahead market prices. However, it is still unclear from which battery size in the grid this applies and to what extent this applies to the battery population in general or also to individual batteries. TenneT is monitoring these developments. If new insights in the TDTR calculations justify switching to a different profile, TenneT will do so.
For existing firm applications that wish to convert their capacity to TDTR, does that include the firm capacity in the load duration curve?
No, in that case TDTR capacity would be unfairly forgiven.
The capacity calculation assumes block profiles with maximum input and off-take at each moment in time. Batteries can both feed-in and feed-out, but one installation never does this at the same time. Is TenneT also preparing an analysis distinguishing between feed-in and offtake at each moment in time? And if so, will a form of contract also be made for this?
TenneT does not actually assume that a battery will currently have maximum input and off-take; that is not physically possible. However, TenneT does have to take into account the possibility that a battery could realistically have maximum input and off-take at any time of the year, which is why TenneT currently uses a block profile. See also the answer to question 5.
The TDTR is currently available for both feed-in and offtake. TenneT does not currently foresee a new form of contract that distinguishes (differently) between feed-in and offtake.
The webinar did not address the question of what the residual space found at the TenneT level means for the RNB grid. How can this residual capacity be used at the MS/LS level, and can TenneT also choose to allocate this residual space to RNBs so that they can fulfill transmission requests?
The Grid Code defines three products for residual capacity. These are the TDTR, TBTR and the VVTR. The TDTR is only available to TenneT customers. The TBTR only for RNB customers. VVTR only in congestion areas.
The TBTR and TDTR only interfere with each other to a very limited extent in practice. The TBTR must be available every day (or period or season) at a fixed time. In effect, this makes the "worst day" leading for the amount of capacity offered at the TBTR. With the TDTR, it is agreed that the customer can use transportation right a minimum of 85% of the time but is confirmed the actual availability only shortly in advance. Thus, both products operate primarily in separate portions of residual space.
Calculation of TBTR profiles by TenneT on behalf of the RNBs' customers will be carried out in Q2 of 2025.
How are planned grid expansions currently factored into the determination of available TDTR capacity?
The highest asset load determines the size of the TDTR that can be released. In areas without congestion and with sufficient grid capacity, a 15-year period is used. The predicted load over 15 years is then the starting point.
Within congestion areas (which, incidentally, are also considered for a 15-year forward period), the highest asset load will occur in the last congestion year. This reference year is used to determine the TDTR capacity. When grid reinforcement is realized, more TDTR space can usually be released in these areas.
ESNL remains in discussion with TenneT regarding the implementation of TDTR. Questions or comments about this can be sent to Stan van den Broek.
