Designing electricity grids with high variable renewable energy penetrations in Ontario, Canada

Significance 

Global consensus on climate change have been impactful in influencing the current drive towards renewable energy resource development, as the pinch of excessive carbon deposition in the atmosphere is becoming a reality. Integrated assessment models have become the de facto method for representing the global energy-economic-environmental scale over multi-decade time periods to identify transformation pathways for climate mitigation. To do so, most integrated assessment models adopt a reduced-form approximation approach, which have a handful of limitations particularly for representing variable renewable energy. Until recently, variable renewable energy has been a marginal contributor to the total electricity supply in most jurisdictions. However, as the contribution of variable renewables increases, representing their impact on electricity systems is becoming increasingly important. Previously undertaken studies have considered incomplete combinations of balancing options, with few considering all flexibility options simultaneously. Moreover, most variable renewable energy analysis studies have been limited in their analysis area, to only those where access to renewable data access is available. Consequently, there is need to focus on variable renewable energy integration at the operational scale with high temporal and spatial resolution.

Madeleine McPherson (who is joining the Civil Engineering faculty at the University of Victoria, Canada) and Bryan Karney (from the Department of Civil Engineering, University of Toronto, Canada) introduced a novel scenario-based electricity system model, SILVER, for the Strategic Integration of Large-capacity Variable Energy Resources. They hoped that SILVER, a production cost dispatch model, would address several limitations associated with previously used models. The purpose of this model was to inform the asset dispatch for a user-defined electricity system configuration that specifies demand response availability, generation assets, storage assets and transmission infrastructure. Their work is currently published in the research journal, Energy.

The research team commenced their studies by formulating and modeling a workable SILVER model framework that included a long-term scenario planning module, day-ahead unit commitment, and the real-time economic dispatch and optimal power flow. Next, the research explored the impact of increasing variable renewable energy penetration on Ontario’s electricity system using data inputs such as the hourly demand schedule and available demand response, renewable resource availability, technology cost and emission assumptions, imports and exports with neighboring jurisdictions, and installed transmission capacity within the province.

The authors observed operational differences between balancing options: demand response with a fixed price remuneration was dispatched in proportion to net load curve variability, whereas storage technologies which take advantage of price arbitrage were dispatched in proportion to marginal cost variability. Additionally, the work noted that while variable renewable energy had a minimal impact on operational costs, since it mostly displaced low marginal cost nuclear generation, there was a significant increase in the system’s installed costs for increasing renewable penetration scenarios.

The McPherson-Karney study has successfully presented a novel scenario-based electricity system model, SILVER, which explores the trade-offs among alternative balancing strategies for high variable renewable energy electricity grids. In this study, the role that storage, demand response, electric vehicles and transmission expansion play in balancing variable renewable energy has been analyzed. It has been seen that while GHG emissions fall with increasing variable renewable energy penetrations, there are local maxima when natural gas replaces nuclear generation, which interrupt this trend. Altogether, Ontario planners have several interdependent difficulties to contend with prior to establishing effective remuneration mechanisms to improve grid flexibility.

SILVER model has been also utilized by Madeleine McPherson and colleagues in more recent papers demonstrating its benefit in variable renewable energy resources.

References

Madeleine McPherson, Bryan Karney. A scenario based approach to designing electricity grids with high variable renewable energy penetrations in Ontario, Canada: Development and application of the SILVER model. Energy, volume 138 (2017) pages 185-196.

Madeleine McPherson, Samiha Tahseen. Deploying storage assets to facilitate variable renewable energy integration: The impacts of grid flexibility, renewable penetration, and market structure. Energy 145 (2018) 1e15.

Madeleine McPherson, L.D. Danny Harvey, Bryan Karney. System design and operation for integrating variable renewable energy resources through a comprehensive characterization framework. Renewable Energy 113 (2017) 1019e1032.

Madeleine McPherson, Malik Ismail, Daniel Hoornweg, Murray Metcalfe. Planning for variable renewable energy and electric vehicle integration under varying degrees of decentralization: A case study in Lusaka, Zambia. Energy 151 (2018) 332e346

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