NREL Models The Increasing Use Of Wind & Solar On Eastern US Power Grid

September 6th, 2016 by Joshua S Hill

The US National Renewable Energy Laboratory has modeled in “unprecedented detail” how the US eastern power grid could accommodate higher levels of wind and solar PV electricity generation.

Many have been the claims that existing power power grids are unable to deal with the influx of fluctuating renewable electricity such as wind and solar generated electricity. It is believed that the ageing nature of so many power grids around the world make them incompatible with the perceived future of widespread renewable energy, with its natural fluctuations that come with the sun rising and setting, and the wind blowing and not.

However, a new study representing work done by the United States Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) has used high-performance computing capabilities together with visualization tools to model, in what the NREL describes as “unprecedented detail,” how the power grid along the eastern United States could operationally accommodate higher levels of wind and solar PV electricity generation than are currently in place, but which are likely to be over the next decade.

Just how “unprecedented” is this study? Other studies which have attempted to detail these concerns have studied operations at one-hour intervals, however, the model used by NREL’s Eastern Renewable Generation Integration Study (ERGIS) analyzed a year of power grid operations at 5-minute intervals — that’s the same real-time interval used currently by grid operators.

“By modeling the power system in depth and detail, NREL has helped reset the conversation about how far we can go operationally with wind and solar in one of the largest power systems in the world,” said the Energy Department’s Charlton Clark, a DOE program manager for the study. “Releasing the production cost model, underlying data, and visualization tools alongside the final report reflects our commitment to giving power system planners, operators, regulators, and others the tools to anticipate and plan for operational and other important changes that may be needed in some cleaner energy futures.”

The study relied on a high-resolution model of the entire Eastern interconnection — which includes power traded in from Canada — and modeled more than 5,600 electricity generators and more than 60,000 transmission lines in a power system that spans the territory running from Florida to Maine, portions of Canada, and extends west as far as New Mexico. Four separate hypothetical scenarios were concocted, with varying levels of fossil fuels, wind, solar, and natural gas — including renewable energy penetration of up to 30%.

“Our work provides power system operators and regulators insights into how the Eastern Interconnection might operate in future scenarios with more wind and solar energy,” said Aaron Bloom, NREL project leader for the ERGIS study. “More importantly, we are sharing our data and tools so that others can conduct their own analysis.”

According to NREL, the findings from the ERGIS report shows that as wind and solar power generation increase:

The operation of traditional power sources (such as coal, natural gas, and hydropower) changes. Turning up or down more quickly to accommodate seasonal and daily variations of wind and solar in order to maintain the balance between demand and supply. In addition, traditional generators would likely operate for shorter periods of time as wind and solar resources meet more of the demand for electricity.

Flows of power across the Eastern Interconnection change more rapidly and more frequently. During periods of very high wind and solar generation (e.g., 40 percent or more of daily load), model regions trade frequently and in large volumes according to new net load patterns.

Regulatory changes, market design innovation, and flexible operating procedures are important to achieving higher levels of wind and solar. Looking at a year of operations at a 5-minute level, ERGIS shows that the power system can meet loads with variable resources — like wind and solar — in a variety of extreme conditions. However, technical feasibility depends on other transmission and generation operators providing the necessary ramping, energy, and capacity services; wholesale market design changes; and various capital expenditures, all of which will have financial and other implications that may need to be addressed and were outside of this study.

What’s interesting about these findings is that they appear (at time of writing, the NREL websites were having trouble, and I do not currently have access to the report in question) not to include the use of battery storage technology to mitigate any of the variance found in renewable energy generation. This further underscores the mis-truths that have been portrayed — namely, that it appears at least the eastern US power grid will be able to stand up to more fluctuations than originally suspected. Integration with battery storage will only serve to further solidify renewable energy’s position in the future energy mix.