Cambium Offers Forward-Looking, Publicly Available Data To Build Into Grid Planning Workflows

NREL Energy Systems Researcher Pieter Gagnon Discusses Value of NREL’s Cambium Tool in Planning Power Grid and Grid-Connected Systems Down To the Hour

Feb. 20, 2023 | By Pieter Gagnon | Contact media relations

Pieter Gagnon is a part of the Grid Planning and Analysis Center at the National Renewable Energy Laboratory (NREL). In this installment of NREL's Tell Me Something Grid series, he discusses the value of forward-looking emission, cost, and generation metrics at the hourly resolution for planning power grid and grid-connected systems.

Did you know the inner growing layer of a tree is called the cambium? This inspired the name of our newest power sector data set, Cambium, at the National Renewable Energy Laboratory. Much like a tree, the power sector may be large and old, but it is still constantly growing and changing. Sometimes to make the right choice for the future, you have to take that growth into consideration.

Cambium data are publicly available and include modeled hourly emission, cost, and generation metrics for a range of possible U.S. electricity sector futures, projecting out through 2050. The granular metrics illuminate trends across the ongoing changes in the power sector. Cambium can support anyone who is making decisions about the future power grid or grid-connected systems but may not have time or expertise to do the modeling themselves.

Cambium is one of many open-source grid planning tools at NREL that, together, can answer questions about the transition to more reliable, resilient, low-carbon power systems—no matter the complexity of the question.

Standard Scenarios vs. Cambium

Since 2015, I have been supporting NREL's efforts to project the possible future of the U.S. electric grid in our annual Standard Scenarios, a suite of forward-looking scenarios of the U.S. electricity sector based on timely and transparent projections of technology cost and performance.

The Standard Scenarios—this year including 70 scenarios—are a great tool for folks wanting to gain a conceptual idea of how the U.S. electricity sector could evolve. They include metrics at the annual temporal resolution and support higher-level analysis, like determining how much U.S. electricity sector emissions could reduce over the next decade because of the Inflation Reduction Act.

Cambium—first released in 2020—builds on the Standard Scenarios. Cambium offers a suite of metrics that are designed to be useful for plugging into analysis and decision-making workflows. Many of the Cambium metrics are at the hourly temporal resolution, which is helpful for understanding important daily and seasonal phenomena. Do you want to estimate the emissions consequences of an electric vehicle, heat pump, or energy-efficiency measure given the ongoing evolution of the grid? This is the type of question that Cambium data are designed to help answer.

Both Cambium and the Standard Scenarios are updated every year using NREL's publicly available Regional Energy Deployment System long-term capacity expansion model to keep up with the rapid pace of change in the power sector.

We have seen the Cambium data help answer a wide range of questions over the years—like, what are the emissions consequences of heat pumps versus natural gas over a building's lifetime? What are the projected electricity mixes and emissions that should be incorporated into a tech company's procurement strategy? And, if a company electrifies their vehicle fleet, what are the emissions consequences of charging at different times of the day?

Cambium data are also making their way into decision-making workflows, including a new Carbon Index put out by RESNET, a LEED pilot credit developed by GridOptimal, and guidance for making clean energy procurement decisions published recently by the Clean Energy Buyers Institute.

Developing Cambium and interacting with users has been the most rewarding work of my seven-plus years at NREL. Other organizations do similar work, but no other tool has the same scope across geography, time, and multiple possible futures that Cambium does—providing a direct, tangible impact for the people planning the grid and grid-connected systems.

Long-Run Marginal Emission Rates

One of the most-used metrics in Cambium is the long-run marginal emission rate, which is an estimate of the rate of emissions that would be either induced or avoided by a long-term (more than several years) change in electrical demand. For example, let's say you are considering buying an electric vehicle (EV) and you would like to know what emissions would be induced by the additional electrical load. The long-run marginal emission rate is designed to answer that question.

Historically, there was a widely accepted approach that you could just take short-run marginal emissions (i.e., the marginal emissions for a given, fixed grid) and add them up over the lifetime of whatever you were evaluating (such as an EV, heat pump, or energy-efficiency measure). The (generally unexamined) assumption was that this approach would give an accurate estimate of the total impact of that intervention. However, we learned the approach had a crucial omission—it did not capture how a change in electricity usage influences what we build.

For example, if we were to use a short-run marginal emission rate to estimate the consequences of widespread vehicle electrification, we would effectively be asking, "What would happen if we electrified vehicles but could only charge them from the grid as it exists at this moment in time?" Importantly, that approach neglects the fact that widespread vehicle electrification would likely result in building many new electrical generators—many of which will be non-emitting. By neglecting that important structural response, we would not have an accurate picture of the potential consequences of choosing to electrify.

Once we realized we were not thinking about emission rates right, we knew we needed a metric that accurately reflected the evolving nature of the grid. This prompted the creation of the long-run marginal emission rate, which incorporates both the operational and structural responses to an intervention into one single metric.

Since developing the long-run marginal emission rate, we have shown how the method outperforms traditional approaches to estimating emissions impacts—again providing a direct, tangible impact for the people planning the grid and grid-connected systems. We also offer a pair of workbooks to help you easily use Cambium's long-run marginal emission rate metrics.

How To Access Cambium

Many commercially available grid planning tools can be difficult to access. At NREL, we offer a suite of open-source data and tools to answer your questions about the future grid.

You can access the latest Cambium data sets by viewing or downloading them through NREL's interactive Scenario Viewer. If you are interested in the Cambium methodology and metrics for the latest data, you can dig into an NREL technical report. Again, we offer a pair of workbooks specifically for using Cambium's long-run marginal emission rate metrics. And, of course, you can contact me, Pieter.Gagnon@nrel.gov, if you have questions or need technical assistance with your particular use case.