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Conversion of Coleson Cove oil-fired unit to natural gas combined cycle
University of New Brunswick
This project is a technical and economic feasibility study for the conversion of Unit #1 conventional oilfired unit to a natural gas combined cycle at NB Power’s Coleson Cove Generating station. A natural gas combined cycle offers several advantages over a conventional oil-fired boiler including lower fuel cost, higher thermal efficiency, faster plant start-up times, superior cycling ability, as well as a smaller carbon footprint. As the contribution to the electrical grid supply from wind power continues to increase, it is increasingly more important for NB Power to have generating stations that are capable of starting up quickly in response to wind power fluctuations. The proposed system includes a Siemens SGT6-8000H Gas Turbine that generates 286 MW at full load. The hot gases from the gas turbine flow to the HRSG which generates steam and powers an existing steam turbine that generates 140 MW. The total net power produced by the proposed combined cycle plant, accounting for station services and generator efficiencies is 418 MW. The planned start-up is in 2020 with an expected plant life of 30 years. The total capital investment for this project is $289 million, and would require another investment, estimated at $50 million, at the end of year 18 to extend the life of the aging steam turbine. The annual profit generated by the plant is $12.3 million. It was calculated that it would take 50 years to reach the break-even point for this project based on today’s natural gas and electricity prices. The payback period is very sensitive to the relative price of electricity and natural gas. It was found that if the price of natural gas were to decrease by 3%, with no change in the sale price of electricity, the plant would reach the break-even point at the end of 30 years. Based on the long payback period and the sensitivity to changes in energy prices, a positive investment decision is not recommended at this time. If NB Power determines that a natural gas combined cycle is required in order to fulfill their mandate to supply safe and reliable power to the Province, it is recommended that the steam turbine also be replaced as a part of the conversion. This would improve the payback period from 50 years to 31 years based on today’s natural gas and electricity prices due to the higher thermal efficiency that is achievable with an entirely new plant (60% versus the designed 58%). A brownfield project with all new equipment would eliminate the need for an expensive, mid-life, refurbishment to reach the desired 30 year plant life. The existing land, utilities and personnel could still be leveraged in a brownfield project, making this an attractive option if it is determined that a NGCC is required.