In terms of fuel quantities, the general equation for the green energy fraction (GREF) of a solar power plant system is, by definition,

GREF = (gr baseline — gr input)/ gr baseline (1)

i. e., GREF = 1 — (gr input)/(gr baseline)

Where,

gr input — — total fuel consumption in the hybrid system

in grams per 1kWhe net electrical plant-output (gr/kWhe)

gr baseline — — 160 gr/kWhe, the specific fuel consumption of the chosen reference (baseline standard), (i. e., a CC using fuel of around 9000 kcal/kg).

For simplicity, both the hybrid system and the reference power system here use the same fuel. It should be realised that the grams ratio expressions signify the inverse efficiencies ratio. The use of grams emphasises the requirement that any fuel used in the plant should be counted and included in the equation.

The concept of fuel avoidance requires comparing a fuel-blended, renewable hybrid system to a real, competing, efficient, non-renewable system for reference (as baseline standard). On circumstances where CC systems cannot be considered as a useful alternative fuel fired electricity generator, thence the 60% baseline is not practical. Therefore, another a locally competing, fuel-fired, efficient system is to be selected for reference standard. Thus, the 40% Rankine-cycle system may serve as a secondary reference against which solar systems will have to compete. In such a case, because by definition the green energy is a reference — dependent parameter, the resulting value for the green energy fraction will be different.

Transformation of a green energy fraction from one reference standard to another can be performed by

TOC o "1-5" h z GREF1/GREFF2 = (B2/B1) (B1-gr)/ (B2-gr)) (2)

Where,

GREF1 — — green energy fraction 1

GREF2 — — green energy fraction 2

B1 — — baseline 1- — in gr/kWhe, (reference standard 1)

B2 — — baseline 2- — in gr/kWhe, (reference standard 2)

gr — — the total fuel consumption in grams per 1kWhe net electrical plant-output

This equation converts a GREF 1 of baseline 1 to GREF 2 of baseline 2. It is significant for enabling comparison between technologies and systems.