At the lower left side of Figure 1 a PV-diesel (or Rankine-cycle generator) hybrid system is modelled. The use of fuel enables the photovoltaic SEGS (solar electricity generation system) to accomplish increased generation capacity, e. g., extend more hours of operation throughout the year far beyond the solar hours (say, 2000 solar hours as shown), by fuel firing the SEGS generator (33.2% net efficiency). At the lower left side of the figure three kinds or modes of such systems are noted. Mode 1 (the 2 kHrs point on the horizontal scale) indicates no use of any fuel during the solar hours (GREF = 1). Mode 2 (the full circular point), the use of 30% fuel, and mode 3 (the full triangular point), of 50% fuel.

At the point of 2000 operation hours with mode 1 the FCR will be zero, as there is no use of fuel. With mode 2, the FCR will be 0.11, and with mode 3, FCR of 0.2. The Green Energy Fraction (GREF) values will show 1,0.89 and 0.8, for the 3 modes, respectively. With full fuel firing beyond the 2000 solar hours, the steep, relatively thick, dashed lines show how fast the fuel-consumption grows. At around 6000 hours they reach the horizontal baseline standard line, which stands for the fully fuel fired CC (gas turbine combined cycle) (FCR=1). In other words, by operation for 6000 hours and beyond, the PV hybrid has consumed fuel (and produced emissions) as much as a 60% efficient fuel fired CC during a full year. At around 8000 hours, the PV hybrid will have produced emissions much more than the CC and nearly as much as a residual fuel oil fired Rankine cycle running at a 40% level conversion (which is a secondary standard). Figure 1 shows distinct, gradual differences between the 3 modes. In

terms of GREF (green energy fraction) the green energy (fuel avoidance energy) which has been produced by the PV system during the solar hours, now will largely diminish or be totally wiped out because of the extended operation hours. This green energy annihilation results from the long hours of firing fuel relatively inefficiently (33.2%) as compared to the baseline standard of 60%. It may also be nearly so with respect to the secondary standard of 40%.