An Analysis of Power Sector Modeling Used in the STAR Report

As a continuation of our series discussing the STAR report, we provide an overview of the modeling methodology used to analyze Colorado's electricity sector by 2050. The modeling entitled, "Power Sector and Colorado Climate Action Plan Scenario Analysis for the Strategic Transmission and Renewables Report," was used to develop a picture of the generation and transmission infrastructure that will be required in response to expected future Colorado loads. The conclusions from the modeling report are used in the STAR report to define strategies for the state to respond to increased energy needs while decreasing the state's carbon footprint to meet the goals of the Colorado Climate Action Plan (CAP).

Brief Overview:
The modeling predicts that by 2030, in order to meet the 40% reduction in CO2 emissions from the 2005 level, the Colorado power generation mix will need to have about 7,750 MW of wind, 480 MW of CSP, and 255 MW of Solar PV bolstered by about 1,700 MW of combined cycle generation equipped with carbon capture and sequestration technology.
The modeling further predicts that a majority of the retired coal-fired generation will be replaced with conventional combined cycle technology requiring by 2030 about 2,400 MW of advanced combined cycle technology with higher efficiencies to replace retired capacity. However, about 4,400 MW of additional combined cycle technology will be necessary to support a high load growth scenario.

Parameters of the Modeling Study:
The modeling study defined three scenarios to use in assessing the potential evolution of the electricity sector: (1) achievement of the newly implemented 30% RES enacted under HB10-1001; (2) achievement of CAP; and (3) determination of the expected CO2 reductions and fuel mix that would result from retirement of aging coal-fired power plants - an expanded version of the Clean Air Clean Jobs Act enacted under HB10-1365.
The model was further based on a number of assumptions: (1) Colorado's electricity sector will meet the CAP; (2) Colorado will experience an aggregate statewide annual average load growth of 1.7 percent to 2030 and beyond to 2050; (3) all of PSCo's conceptual SB07-100 transmission lines were assumed in service by 2030; (4) for the retirement scenario, all CO coal-fired generating plants assumed retired by age 45 beginning in 2017; (5) The 30% RES will be met; (6) 33% wind penetration by 2035 and increasing to 45% by 2050; and (7) nuclear power was modeled starting in 2017.

Viable Scenarios to Achieve CAP Targets:
1. The most viable pathway to meet the CAP targets is demand side measures to reduce or contain load growth.
2. The most attractive scenario to reduce overall CO2 emissions is the one that starts with the base case, adds the benefit of demand side management, then introduces the benefits of RES and CAP compliance, as well as the benefits of coal plant retirements beginning in 2017 until they reach age 45.
3. The most viable alternatives to reach the CAP targets are to deploy demand side management and set a schedule for retiring coal-fired generation plants when they reach the age of 45.
4. The modeling clearly indicates that unless a much greater commitment to demand-side measures is instituted, major supply-side capacity additions, in the form of renewable energy and natural gas, must be brought on line to meet load growth and CAP goals.
5. Transmission is needed to develop Colorado's wind and solar resources.