Page 232 - Advanced Gas Turbine Cycles

1 94 Advanced gas turbine cycles

0 50 loo 150 200 250
CARBON DIOXIDE TAX $/TONNE
Fig. B.S. Effect of carbon dioxide tax on electricity price for a combined cycle gas turbine plant.

added to the cost of generation, making it 5.1 c/kWh. This may make the plant
uneconomic when compared to a nuclear station or even windmills. This point is
illustrated in Fig. B.5 which shows how the generation cost for this CCGT plant would
vary with the tax level and how other plants might then come into competition with it.
If however, the original CCGT plant was modified to reduce the amount of C02
entering the atmosphere from the plant (say to 0.15 kg/kWh) at an additional capital cost it
may lead to an increase in the untaxed cost of electricity (say from 3.6 to 4.2 c/kWh).
Then the effect of a carbon dioxide tax of 5 ckwh would be to increase the electricity
price to (4.2 + 0.15 X 5) = 4.95 ckWh and this is below the ‘taxed’ cost of the original
plant. In fact, the new plant would become economic with a carbon dioxide tax of T ckg
C02, which is given as (3.6 + T X 0.3) = (4.2 + T X 0. IS), i.e. when T = 4 c/kg C02.

References
11 I Williams, R.H. (1978). Industrial Cogeneration, Annual Review of Energy 3, 313-356.
121 Wunsch, A. (1985). Highest efficiencies possible by converting gas turbine plants, Brown Boveri Review 1,
455-456.
I31 Horlock, J.H. (1997). Cogeneration-Combined Heat and Power Plants, 2nd edition, Krieger, Malabar,
Florida.
[41 Horlock. J.H. (1997), Aero-engine derivative gas turbines for power generation: thermodynamic and
economic perspectives, ASME Journal of Engineering for Gas Turbines and Power I 19( I), 119- 123.
[SI Davidson, B.J. and Keeley, K.R. (1991), The thermodynamics of practical combined cycles. Roc. Instn.
Mech. Engrs., Conference on Combined Cycle Gas Turbines, 28-SO.