Introduction

Cynics might argue that it’s impossible to operate the power grid economically with 100% renewable energy on an hourly basis, but a model developed by Peninsula Clean Energy, a community choice aggregation agency that serves San Mateo County and the City of Los Banos, California, suggests it’s possible. To prove it, Peninsula Clean Energy intends to do it by 2025. “Our default product, which all of our customers receive at this time, is 50% renewable, 100% clean,” Jan Pepper, CEO of Peninsula Clean Energy, said as a guest on The POWER Podcast. “Our goal is to have the power that we deliver by 2025 be 100% renewable, and matched on a time-coincident, hour-by-hour basis.” Under current California regulations, renewable energy percentages are matched on an annual basis. “For example, if we have a 3,700 gigawatt-hour load, for us to be 50% renewable, which we are right now, we procure 1,850 gigawatt-hours per year of renewables and 1,850 gigawatt-hours of additional clean resources, which for us is large hydro, and that meets our needs on an annual basis,” Pepper explained. That basically means there are times when Peninsula Clean Energy is supplying more than 50% renewable power to its customers and times when it’s supplying less, but over the course of the year, everything averages out so the agency hits its 50% renewable energy target. However, by 2025, the agency expects to match its supply with its load every hour of every day. “In order to do that, we’ll be adding a lot of storage,” said Pepper. Peninsula Clean Energy’s modeling tool, which it calls MATCH (which stands for Matching Around-The-Clock Hourly energy), was built, tested, and used over the past two years. The goal was for the agency to determine the optimal 24/7 renewable energy portfolio. Leaders wanted to know how much it would cost, the level of emission reduction benefits that could be achieved, and the impacts it might have on the broader energy system. A team of workers, which included Planning and Analytics Manager Mehdi Shahriari, Power Resources and Compliance Manager Sara Maatta, and Greg Miller from the University of California, Davis, started with an open-source model called the “Switch Power System Planning Model” and modified it significantly to create MATCH. Using the model, the team outlined in a 44-page white paper how matching customer electricity demand with renewable energy supply 99% of the time achieves the ideal balance of being cost-competitive, reducing portfolio risk, and reducing emissions. “We find that a ‘sweet spot’ goal of providing 100% renewable energy on a 99% time-coincident basis results in only a 2% cost increase relative to our baseline, while achieving critical emission reductions and providing other benefits to the grid,” the team wrote in the report’s executive summary. “We were pleasantly surprised,” said Pepper. However, while achieving the last 1% is doable, it’s not quite as practical. “Our model also found there are diminishing returns in trying to match the last 1% of customer demand, with a 10% increase in portfolio cost needed to go from 99% time-coincident to 100% time-coincident,” the report says. “We’re excited about what the future holds and being able to show that we can do this in a cost-effective way, so that we can all have a much more sustainable and clean energy future,” Pepper concluded.