E3: Energy+Environmental Economics
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Renewable Energy Flexibility (REFLEX) Model

REFLEX is a first-in-class model that calculates the need for power system flexibility under high renewable penetration. REFLEX builds on conventional bulk power system reliability models by introducing new flexibility-related reliability metrics and incorporating operating parameters into the reliability assessment. REFLEX traces the full distribution of load, generation and ramping conditions that a system is likely to encounter by sampling daily profiles of load, wind, solar and hydro conditions from a multi-year database of actual and modeled values. Reduced-form production simulation determines optimal unit commitment and economic dispatch at daily, hourly and five-minute timesteps. Reliability metrics are calculated such as expected unserved energy, expected overgeneration and ramping deficiencies to form a stochastically robust picture of flexibility deficiencies.

REFLEX can be used to evaluate investments in flexible resources such as combustion turbines, reciprocating engines, energy storage, or demand response, as well as changes in operating procedures such as improved forecasting, participation in a regional market, or renewable curtailment. Addition of new resources reduces the expected quantity and cost of flexibility shortages. These cost savings are compared against the cost of procuring and operating the new resources, as illustrated in the chart below. REFLEX identifies the optimal flexibility procurement plan as the quantity of flexible capacity that minimizes the total cost, including both operating costs and the cost of flexibility violations.

REFLEX is available as a commercial software package on the ProMaxLT and PLEXOS for Power Systems production simulation modeling platforms. E3 is currently using REFLEX for PLEXOS to support the California Independent System Operator’s (CAISO) modeling of flexibility needs to accommodate high renewable penetration in the context of the California Public Utilities Commission’s (CPUC) Long-Term Procurement Planning proceeding.

E3 Papers

"REFLEX: An Adapted Production Simulation Methodology for Flexible Capacity Planning"

"Optimal Investment in Power System Flexibility"

"Renewable Energy Flexibility (REFLEX) Results"