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Decarbonizing electricity generation through deployment of renewable technologies such as wind and solar is a key component of many climate change mitigation efforts. With increasing penetrations, the need to manage variability in renewable generation becomes critical. However, renewable variability is often poorly represented in energy planning studies which focus on energy and capacity adequacy. In this study, we used a hybrid capacity expansion and dispatch model with explicit inclusion of ramping and regulation services to examine balancing requirements in a decarbonizing electricity system. We find that ramping and regulation services needed for management of variable renewables alter the optimal mix of generation and transmission capacity relative to simpler planning models. In particular, we find enhanced value in expanding transmission capacity to access flexibility. • Representing short-term constraints in long-term energy models changes the outcome. • Flexibility is a key constraint in systems with high penetrations of renewables. • Interregional transmission can help provide system flexibility. [ABSTRACT FROM AUTHOR]

The use of forest residue may mitigate greenhouse gas emissions by displacing the use of coal or other fossil fuels for electricity generation. However, economic viability of bioenergy requires availability of feedstock at appropriate cost. The current work attempts to quantify delivered biomass cost at plant gate and estimate cost and emission benefits to the electricity system associated with the conversion of coal units to bioenergy. This study is carried out with the optimization model OSeMOSYS, analyzing the Alberta electrical system, its mid-term coal phase-out and renewable energy targets. Alternative scenarios were compared to evaluate the effect of a biomass retrofit option on the incentives needed to achieve 30% renewable penetration by 2030. Results show that although bioenergy has a higher levelized cost than wind power, the system requires less backup capacity and less renewable energy credits to meet renewable energy goals when the biomass retrofit is allowed. In addition, the total system cost to 2060 is found to be 5% less than the scenario without the biomass option. The firm capacity provided by biomass compensates for its higher levelized cost of energy. [ABSTRACT FROM AUTHOR]