Western Wind & Solar Integration Study Phase 2: Cycling Impacts on Thermal Generators

1. Western Wind & Solar Integration StudyPhase 2: Cycling Impacts on Thermal Generators Dick Piwko, Gary Jordan March 16, 2011

2. Cycling Costs: what are we missing now? Additional cost of cycling, when incremental costs are not included in commitment and dispatch : MAPS Solution Incremental Variable Cost Cycling Variable Operating Cost, VOC (per MAPS) Addition VOC for Cycling (outside of MAPS) Total Variable Operating Cost, VOC • “Cycling”? • Means lots of things, but in broad terms we are concerned about 2 chunks: • Start/stop - decommit • Ramp – up/down, turnback, dispatch

3. Cycling Costs: new optimum Incremental Variable Cost Cycling • Additional cost of cycling, when incremental costs are included in commitment and dispatch : VOC (per MAPS) Addition VOC for Cycling (outside of MAPS) Total VOC Solution considering Total VOC

4. Cycling Costs: looking for benefits • Quantifying the VOC benefit of reducing the additional cost of cycling: VOC (per MAPS) Addition VOC for Cycling (outside of MAPS) Total VOC Reduced cycling cost with mitigations implemented Incremental Variable Cost Solution considering Total VOC Cycling

5. Cycling Costs & Production Cost Simulations • What is presently in the MAPS model: • Start up cost (not a function of any frequency, past or subsequent dispatch) • Non-fuel variable cost (O&M, a fraction of MWhr) • Minimum down time • Heat rate vs P (static multi-segment curve) • Minimum and maximum dispatch • Emissions vs MWhr (as a function of static heat rate) • What is presently not in the MAPS model: • Non-fuel O&M cost as a function of (a) depth of cycle; (b) ramp rate; (c) duration of cycle • Heat rate (and emissions) impacts due to rate-of-change of power during ramps • Minimum down time as a function of previous history • Variable minimum downtime/start up – and cost, heat rate / fuel penalty, emissions penalty associated with shorter/longer downtime • Lots more . . . . . . • Plexos has similar characteristics.

6. Mitigation Options: From Solution to Value • Power plant technical experts define specific modifications • What is the modification (boiler features, pumps, controls, fans, coal mills, etc.) • How does it modify operation of the power plant (faster ramp, lower turndown, etc.) • What is the cost (capital cost, variable cost) • What is impact on emissions • GE team translates these modifications into data and/or procedures for evaluating operational impacts/costs with production simulation tools (MAPS & Plexos) • Variable cost parameters for items included in MAPS & Plexos • Post-processing of annual operation profiles to assess costs that are not specifically modeled in MAPS or Plexos • Iterative MAPS & Plexos simulations to refine unit operation profile with new operating cost characteristics • Bottom Line: Calculate system-wide production cost impacts with mitigation in place; Establishes the value of the solution.

7. Mitigation Options: From Need to Solution(and its value) • Postulate an attractive solution (eg., turndown to 20% load) • If achieved, what is its value to overall operating cost of the power grid? • Can the required physical modifications can be done to the plant within that value? • Initially focus on a few units • Then generalize to groups or types of generating units