In a recent U. S. regional power plan discussion document (North West Council, 2002) the cost of a 400 MWe pulverised coal plant was found to be $1468/kWe in the North West USA. This plant is used as a coal cost baseline for comparison costings against two CLFR/cavern scenarios, one with 54% capacity factor and one with 68%. In Table 1, the coal plant is given an 80% capacity factor, within the normal range for capacity factors in the USA. David and Herzog (2003), for example, use 75% in a study of carbon sequestration. The coal plant IRR was held to 14%, assumed as a reasonable payback for solar plants in NREL (2003), by adjusting the wholesale price for electricity. premium charged for peaking sales, because as the capacity factor is reduced, there is a greater opportunity to indulge in ‘peak lopping’, giving a higher return per kWhe. The IRR for such trading can only be determined using a complex grid pricing model not available to the authors.

The solar plants were then evaluated on this selling price and it was found that their IRR is comparable to coal; slightly higher than coal for the 68% capacity factor plant and slightly lower for the 54% plant. The optimal capacity factor depends upon the

In Fig. 2, the capacity factor of new pulverized coal plant is now varied to produce a range of electricity wholesale prices which meet the desired IRR of 14%. This is compared to the 68% CF CLFR/cavern storage solar plant which is also held to an IRR of 14%. The graph shows that the coal fired plant is more costly up to about a CF of 82%, and even at a CF of 90% is only $5 per MWhe less expensive than the 68% CF solar plant. This suggests that minimal measures such as low priced carbon trading

would be sufficient to provide solar competitiveness against the cheapest baselaod coal fired plant.