PNNL

Like the great and powerful Oz behind the curtain, a lot of different behind-the-scenes levers have to be pulled to deliver reliable power to homes across the country. 

Hydropower's ability to throttle power up and down helps maintain a balanced grid. This is where power system models are particularly important because they inform grid operation decisions, including how much energy is needed from which power plant.

The representation of hydropower in power system models is challenging because water as a fuel source has its own constraints. For example, there is competition among water uses, environmental requirements, and river regulations typically addressed by water models. Hydropower operations are optimized in both water models and power system models, although inconsistently because hydropower is valued and constrained differently in both models. As a result, hydropower isn’t being used to its full potential, and the value it brings to the grid isn’t valued appropriately. 

A new report by Pacific Northwest National Laboratory (PNNL) and the National Renewable Energy Laboratory identifies a path forward for hydropower research and strategies to resolve gaps in power system modeling for hydropower. The report is based on gaps identified during a workshop held in 2019. The workshop brought together 40 experts, ranging from water managers to power system engineers, to discuss the challenges in hydropower’s representation to the grid.  

This workshop has already led to studies that will help represent hydropower in power system models. The outcomes are intended to support the hydropower industry by evaluating operations and grid resilience and clarifying the value of hydropower services to water managers. 

“Thanks to our hosts and partners at the Western Electricity Coordinating Council (WECC) in Salt Lake City, we were able to bring together technical experts from around the world into one room to talk about this important issue," said Nathalie Voisin, a PNNL water resource engineer and lead author on the report. "Representatives from market operators, utilities, developers for commercial water management, power system models, and energy-water researchers discussed data availability and needs, modeling computation and co-simulation techniques, and computational tradeoffs for different applications. The report that we published reflects the many priorities and recommendations presented at that workshop.” 

Workshop helps HydroWIRES take shape

The workshop and report are helping to shape the vision of the U.S. Department of Energy’s Water Power Technologies Office (WPTO) HydroWIRES Initiative. HydroWIRES is expected to improve the understanding of how hydropower and pumped-storage hydropower contribute to the reliability, resilience, and integration of the evolving U.S. electric grid. The initiative is working to improve data, models, and technology to advance capabilities and inform decision-making for hydropower owners and operators, regulators, original equipment manufacturers, and environmental organizations. 

“Since the workshop, WPTO has invested in resolving critical modeling gaps with foundational investments,” said Rebecca O’Neil, a PNNL program manager and one of the report authors. “Improving hydropower optimization has the potential to enhance rivers, make hydropower more competitive, and [make] grids more reliable.” 

Outcomes described in the report were based on the four primary workshop goals: 

• understand the current representation and challenges of characterizing hydropower assets between electricity dispatch and water management models; 
• discuss the consequences of model limitations related to unused flexibility; 
• increase economic opportunities and provide investment strategies; and 
• prioritize research and modeling to improve hydropower’s representation in power system models. 

Gaps and solutions

The workshop focused on bridging the gap in hydropower representation between power system and water management models. By addressing this major gap, the grid can operate more reliably and use hydropower more efficiently. According to the report, the representation of hydropower in power system models has not evolved at a rate that sufficiently captures the range and availability of hydropower resources. Many water management models support decision-making for a variety of stakeholders and river systems. 

The workshop participants identified the absence of available data as a challenge for developing and evaluating hydropower models. 

“The lack of information available for identifying important processes such as hydropower flexibility and its variation through time makes evaluation of hydropower models difficult, eventually making hydropower modeling a “black box” in many research projects,” Voisin said. Another focus for resolving gaps between power and water systems models is to improve model validation as well as a model’s overall uncertainty characterization, specifically for hydropower representations. 

Workshop discussions also noted that current models and modeling frameworks don’t adequately address the current variations of energy management and water management decisions. Participants suggested using advances in computing power and modeling techniques to develop new and improved models and to conduct comparative model studies. 

The gaps and vision of modeling needs have already resulted in a collaboration with the hydropower industry to develop a database of hydropower operations. 

Next steps 

New HydroWIRES projects emphasize the collaboration between power system and water modelers. For example, Voisin is leading a project to develop algorithms that can be used in production cost models to improve the representation of hydropower. The project’s goals are to reduce the costs of energy and electricity and to provide more resilient, flexible, and reliable energy systems. To achieve these goals, the research team is working to: 

• develop tools to evaluate the dispatch of hydropower as simulated by production cost models; 
• create hydrologic and hydropower data sets to inform production cost models; 
• use developed tools to improve accuracy and opportunities when data sets are running; 
• engage with system operators and entities to look at system reliability studies; and 
• make data sets available for long-term planning studies. 

“The DOE HydroWIRES initiative was built on the premise that hydropower has a unique and competitive role in the U.S. energy system,” Voisin said “It's important for water resilience and energy security to improve the accuracy and capability of power system modeling. This emerging research is helping us achieve these goals.”