CALC-055

The RD2 capacity-factor double-count hypothesis

Calculation · Cited by CLM-0247 , CLM-0259

What this is

This is the project's own arithmetic, published in full so it can be checked rather than taken on trust. It is not a source. Every input it uses is cited to a record, and the conclusion it reaches only carries as far as those inputs do.

Feeds CLM-0247. Answers QST-004.

Script. lcoe-model.py SECTION 6B, section_nasa_formula_check(), line 632. This section exists specifically to run NASA's own formula on this model's inputs, which is what makes the finding attributable rather than merely a disagreement.

Why it was needed. CALC-054 left a 36 per cent RD2 gap that the cost build could not explain. A gap that appears only where capacity factor is far from unity, and not where it is near unity, has a shape. The shape is checkable.

Inputs.

Quantity	Value	Source	Stated or assumed
RD2 nameplate power	3,369.9 MW	derived in CALC-053	STATED (derived)
RD2 capacity-factor-adjusted delivered power	2,021.95 MW	derived in CALC-053; also SRC-012's own figure	STATED
RD2 capacity factor	0.60	SRC-012	STATED
RD1 capacity factor	0.997	SRC-012	STATED
NASA's LCOE formula and cell references	SRC-012 p.56	SRC-012	ASSUMED to be accurately reconstructed; could not be confirmed against the underlying spreadsheet, which was not available

Working, transcribed.

RD2, normalising overnight capital and fixed O&M by CF-ADJUSTED power (2,021.95 MW),
     with (8760 x capacity factor) also in the denominator:
                                                   1.597 $/kWh
     [NASA's published RD2 figure: 1.59 - reproduced]

RD2, normalising by NAMEPLATE power (3,369.9 MW) instead:
                                                   0.958 $/kWh

This model's own independent multi-year DCF for RD2 (CALC-054):
                                                   1.015 $/kWh

The two normalisers differ by exactly the capacity factor:
     1.597 x (2,021.95 / 3,369.9) = 1.597 x 0.60 = 0.958

The same three routes for RD1, where CF = 0.997 (near unity):
     0.612   /   0.610   /   0.623   $/kWh - no equivalent gap

Result. Correcting the normalisation gives 0.958 $/kWh, which sits close to this model's independently built 1.015 $/kWh. The 0.60 appears twice: once implicitly in the normaliser and once explicitly in the denominator.

Conclusion. A specific, falsifiable hypothesis about a calculation error in a published study, offered because it is checkable and because two independent methods converge on the same corrected answer. If confirmed, RD2 is materially less bad relative to RD1 than published - 1.6x RD1's cost rather than 2.6x. It does not change the qualitative conclusion that both designs are far from terrestrial-competitive.

Where this fails. MEDIUM confidence, not certainty. The reconstruction of NASA's formula could not be confirmed against the source spreadsheet. An alternative, unidentified explanation for the same RD2-specific, capacity-factor-correlated pattern cannot be ruled out. The RD1 control is what makes the hypothesis worth stating: the mechanism predicts the effect is invisible when capacity factor is close to 1, and it is.

Cite this

energyaperture.com/calc/calc-055

CALC-055. The working above, not a source document.