Techno-Economic Evaluation - Cleaner Coal Plant Operability

Abstract:

Clean power technologies have been developed to achieve high efficiencies and low emissions due to stringent environmental regulations. The obvious benefits of clean technologies were adequate while the power market was relatively stable and the plant could operate in base-load condition. However, in the current liberalised power market, electricity prices fluctuate, and thus the operational flexibility plays an important role in the plant profitability.

Powergen and UMIST (Department of Process Integration) have collaborated in a project to develop a means of ascribing a financial value to the operational flexibility (start-up times, ramp rates, minimum stable generation etc) of generating units. The project was partly funded through Powergen (£55k) and partly through support from the DTI's Clean Coal Technology Programme (£50k). This report summarises the Ph.D. study undertaken and presents the results and conclusions.

The basic purpose is to investigate the operational flexibility for power plants generating using coal or heavy fuel oil, in particular looking at Integrated Gasification Combined Cycle plants (IGCCs). The operational flexibility is defined as the ability of the plant to change its operation to respond to the fluctuating electricity prices. The profit that a plant makes is then compared to the profit of a perfectly flexible plant (i.e. instantaneous start-up and shutdown times) to give the cost of inflexibility (Operational Inflexibility Cost (OIC)).

Of the plants studied, the fully integrated IGCC has the best overall thermal performance. The higher the fuel price, the more beneficial it is to operate the IGCC compared with PF plant. In terms of the degree of integration, the fully integrated IGCC has better performance rather than the non-integrated and the partially integrated IGCC plant. The calculated operational inflexibility costs ranged between 0 (for base load operation) and about £2.5M p.a. (for about 55% utilisation) on a 250MW unit.

The overall profitability (excluding fixed costs and capital cost payback) is more dependent on the base capability of the plant than its flexibility. The higher the efficiency of the plant, the less relevant operational flexibility becomes, since high efficiency plant will run base load more often and for longer than lower efficiency plant (if all other factors are equal, such as fuel price, etc). The higher efficiencies of highly integrated IGCCs can offset the cost associated with the longer start up times of the gasifier, due to the increased likelihood of base load running).

1. Introduction
2. Background
3. Theory and Implementation
4. Summary of the Methodology
5. Results
6. Conclusions
7. References

Publication Year:

2004

Publisher:

Department of Trade and Industry

DOI:

No DOI minted

Author(s):

Norris,D.P., Tabberer, R.J., Dimou, E. & Zhang, N.