Colorado Springs looks at gas, renewable alternatives to coal plant

Colorado Springs Utilities (CSU) is looking at various alternatives, including new gas-fired combined-cycle generation and coal-to-gas conversion, as it ponders when and how to decommission the coal-fired Martin Drake power plant.

A June 25 draft alternatives outline from consultant HDR Engineering includes a number of alternatives. “This listing includes the Base Case modeling requirements, the mandatory alternatives required in the project [request for proposals] RFP, and additional alternatives that will be screened in the subsequent phases of the study,” said the report.

The alternatives outlined are focused upon those that best simulate an in-kind replacement of the Drake facility with respect to generation capacity, operability, and dispatchability. The list will be reduced to no more than 12 alternatives for the purpose of detailed modeling analysis and Sustainable Return on Investment evaluation.

The study of all alternatives will assume the first year of operation beginning on Jan. 1, 2014, and will extend until Dec. 31, 2043.

The Base Case scenarios are intended to initially compare ongoing Drake facility operation based upon the current forecast of capital additions and performance to that of a natural gas-fired combined cycle of an equivalent capacity.

Under the scenario “Ongoing Drake Operation on Coal”:

  • All units will continue to run and will be retired in 2033;
  • Units will be abandoned in place with no decommissioning costs;
  • NeuStream emissions control system operational in January 2015;
  • Selective Catalytic Reduction (SCR) additions operational in 2023 (or date as agreed with CSU per HDR assessment of need); and
  • Replacement generation will be assumed as natural gas combined cycle of equivalent capacity.

The “Alternative Base Case–Combined Cycle Equivalent” scenario includes:

  • Drake 5 retired in 2016;
  • Drake 6 and 7 retired in 2020 with new combined cycle placed into service on Jan. 1, 2020; and
  • Greenfield combined cycle plant assumed with transmission upgrades incorporated to deliver power to downtown Colorado Springs.

On-site alternatives are those that will involve modification to the existing Drake facility and/or addition of new generation equipment on the Drake site. Gas-fired options will also require an assessment and evaluation of the natural gas supply infrastructure to the Drake site with respect to firm gas supply and supply pressure availability.

Potential on-site alternatives include:

  • Gas operation of existing steam boilers;
  • Gas and coal co-firing of existing boilers to meet emissions limits;
  • Additional biomass and coal co-firing of existing boilers;
  • Nominal 260 MW, gas- and diesel-fired engine generator plant;
  • Nominal 260 MW simple cycle turbine installation (gas and diesel) with air cooling;
  • Nominal 260 MW aeroderivative combined cycle (gas and diesel) using existing wet cooling towers;
  • Nominal 260 MW frame type combined cycle (1×1 or 2×1, gas and diesel) using existing wet cooling towers;
  • Phasing the addition of 60 MW incremental gas generating units (either engines or turbines) to match staggered retirement dates of Drake Units 5, 6 and 7.

The evaluation of greenfield alternatives will require an assessment of electrical transmission system upgrade and/or synchronous condenser needs for the delivery of power into downtown Colorado Springs. Greenfield options include:

  • New most efficient and best performing 260 MW combined cycle alternative with air cooled condenser, near firm gas pipeline and electric transmission line;
  • New most efficient and best performing 260 MW gas engine generator plant, near firm gas pipeline and electric transmission line;
  • Use dual fuel capability instead of firm gas pipeline;
  • Phase in simple cycle and/or combined cycle units to allow for staged retirement of Drake Units 5, 6 and 7 (either engines or turbines).
  • Installation of over 260 MW of wind capacity with a corresponding installation of natural gas generation to allow for a firm generation resource. Size of each to be defined through the evaluation;
  • Alternative assuming an agreed upon quantity of demand-side management and energy efficiency load reductions to understand the implications of this on the most suitable retirement date for Drake.

Representative purchased power agreements (PPAs) for delivery into Colorado Springs may be evaluated based upon regional characteristics and agreements. Alternatives include:

  • Review of representative purchased power options that are available;
  • Review the Fountain plant owned by Southwest Generation. May need to firm up gas pipeline capacity or add dual fuel capability.
  • “Firmed” renewable PPAs.

City aiming to complete Drake alternatives study by the end of 2013

The Colorado Springs City Council, sitting as the Utilities Board, requested a study to evaluate alternatives for when and how the Drake plant can be decommissioned. The study will be completed by the end of 2013, with a decision about the future of the Drake facility expected in 2014. In phase I of the effort, an RFP was developed and evaluated. A contract was awarded to HDR Engineering to perform the study. Phase II began in May and is exploring energy source alternatives for replacement power, considering a broad range of economic, environmental, social, and health impacts. 

At a June 28 task force meeting, HDR Engineering presented the project schedule and status, draft alternative cases, draft quantitative work metrics, draft assumptions and other study details.  Also at the meeting, two upcoming public open houses were announced for Aug. 15 and Nov. 5 The next task force meeting is scheduled for Aug. 15.

The Drake plant began operating in 1925. Units 1-4 have been removed. The units currently operating are:

  • Unit 5 – 46 MW, built in 1962;
  • Unit 6 – 77 MW, built in 1968; and
  • Unit 7 – 131 MW, built in 1974.

All three units are capable of burning either coal or natural gas. In 2011, the Drake units were available 92% of the time. The units meet or exceed state and federal regulations for emissions. Baghouses collect more than 99.8% of fly ash. All units have low NOx burners, with additional NOx controls to be installed by 2017 to achieve further reductions. Drake uses very low sulfur coal from the Powder River Basin in Wyoming. Additional emissions control equipment will be installed at Drake to comply with Regional Haze Rules, with construction to begin in 2013.

Colorado Springs Utilities has a mix of coal, natural gas, hydro, renewable energy and firm power purchases that can provide up to 1,147 MW. If Martin Drake’s 254 MW were eliminated, 161 MW would need to be replaced with some other resource to meet customer requirements and maintain required planning reserve margins. Additional power would also be needed to serve any new business or residential customer load.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.