Understanding CDM Methodologies - SuSanA
Understanding CDM Methodologies - SuSanA
Understanding CDM Methodologies - SuSanA
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Build Margin<br />
Build Margin:<br />
newest Plants<br />
providing 20%<br />
of Grid Electricity<br />
or last 5 Plants if<br />
generating more<br />
than 20%<br />
Ex ante or ex-post<br />
Calculation of OM<br />
allowed<br />
Weighting OM<br />
and BM: Default<br />
50-50, for Wind<br />
and Solar 75-25<br />
The BM emission factor is to be calculated as the generation-weighted<br />
average emission rate (tCO 2<br />
/MWh) of recent capacity additions to the<br />
system. These capacity additions consist of either the five power plants that<br />
have been built most recently, or the power plant capacity additions to the<br />
system that comprise 20% of the system generation and that have been built<br />
most recently. The sample group that comprises the larger annual power<br />
generation shall be used.<br />
Ex-ante vs. ex-post BM calculation: The BM emission factor can be<br />
calculated either ex-ante based on the most recent information available at<br />
the time of PDD submission, or ex-post and updated annually. The ex-post<br />
calculation is allowed only during the first crediting period. For subsequent<br />
crediting periods, it should be calculated ex-ante. The choice between exante<br />
and ex-post vintage should be specified in the PDD and cannot be<br />
changed during the crediting period.<br />
Combined Margin<br />
The CM emission factor is to be calculated as the weighted average of the<br />
OM and BM emission factors. The OM/BM weights are set 50% by default.<br />
But for wind and solar projects, the default weights are 75% for the OM and<br />
25% for the BM due to their intermittent and non-dispatchable nature (see<br />
Box 15). Alternative weights can also be chosen upon justification 228 .<br />
Box 15: OM/BM weights for different project classes<br />
Weighting for<br />
different Types of<br />
Renewables<br />
Use average Plant<br />
Efficiency<br />
ACM0002 has set default OM/BM weights as 50% since its original version, with<br />
possible alternative weights upon justification. Over time, several arguments and<br />
proposals have been made for the use of alternative weights. The salient example<br />
is the exclusive use of OM for small power generation projects arguing that small<br />
capacity additions would only have negligible impacts on future capacity additions<br />
to the grid. The issue was clarified by the guidance given by EB 22 229 . As per the<br />
guidance, project size is not a legitimate basis for changing the OM/BM weights.<br />
the other hand, timing of project output, predictability of project output, and<br />
suppressed demand can be important factors in determining alternative weights.<br />
The OM weight can be increased for highly off-peak projects (e.g. solar PV<br />
projects in evening peak regions, seasonal biomass generation during off-peak<br />
seasons) or projects with output of an intermittent nature (e.g. wind or solar<br />
projects). The BM weight can be increased for highly on-peak projects (e.g. air<br />
conditioning efficiency projects) or project under suppressed demand that are<br />
expected to persist through over half of the first crediting period. However,<br />
neither weight can exceed 75% during the first crediting period given that it is<br />
unlikely that a project will impact either the OM or BM exclusively during the<br />
period.<br />
228<br />
See ACM0002 (version 06) for further guidance.<br />
229<br />
See EB 22, Annex 2.<br />
49