Last week, I wrote an introduction to the hot new trend in energy: 24/7 carbon-free energy (CFE), i.e., matching a company or city’s power consumption with production of clean electricity throughout the day, every hour of every day. If you haven’t read it yet, you’ll want to check it out before reading this post.Today, I want to talk about a big debate around 24/7 CFE, regarding whether it’s the right goal for companies and cities to adopt at all. Exploring that debate will help us get our heads around what 24/7 CFE can and can’t accomplish.But first, a quick refresher. Here’s the idea: right now, in addition to generating electricity, renewable energy projects generate renewable energy certificates (RECs), one for each megawatt-hour. They can sell the RECs to any entity looking to buy renewable energy. For instance, a company or city that wants to go “100 percent renewable” can simply buy enough RECs to cover its yearly electricity consumption.At least two changes would be required to make 24/7 CFE possible. First, “renewable energy” would expand to “carbon-free energy.” Any generator putting out electrons without carbon emissions, including nuclear or natural gas with carbon capture and sequestration (CCS), would qualify. And second, RECs, rather than coming in month- or year-long chunks, would be issued in time-stamped increments of an hour, so that buyers could target procurement at the particular hours of the day when they need CFE. Eventually, each hourly REC would contain information about avoided carbon emissions, so buyers could tally up the carbon impact of their purchases. That’s the vision.In this post, I’m going to discuss an objection to 24/7 and some counter-arguments to the objection. Then, in my next post (yes, this is turning into 24/7 Month), I’ll look at some new modeling of the impact of 24/7 procurement and try to draw some conclusions. We’re going to have a good time.Measuring carbon is mostly doableAn intrinsic part of the 24/7 CFE vision is that each hourly REC will be tagged with a certain amount of avoided carbon. This will allow buyers to make procurement decisions that take emissions into account.There are some issues and controversies around calculating avoided carbon, though they’re not the ones I’m going to focus on today. Some carbon counters have proprietary formulas (like WattTime) and some are trying to develop open-source methods (like EnergyTag). The numbers they produce are not radically different, but they do differ. They vary in how they calculate the marginal (most expensive) energy source on the grid at a given moment — the marginal generator is the one that will spin down to make room when the CFE is produced. They differ in how to draw the geographic boundary of analysis, which can affect results. And other stuff like that. “To go from the generation data to the local carbon emissions data is not trivial,” says Toby Ferenczi, founder of EnergyTag, “because you're trying to model the flow of electrons. Until you can track a single electron through the system, there will always be different types of approximations.” There’s also the question of how distributed energy resources (DERs) are treated. Right now, grid operators tend to have little visibility into or control over DERs; energy generated locally, on a distribution grid, is viewed by grid operators as reduced demand on that grid. Bringing DERs more fully into the picture as deployable resources is an important long-term challenge.There are data issues too. If you look at electricityMap, which seeks to track the carbon intensity of every grid in the world, at every hour, you will see that there are still big holes, areas where utilities have not made the data public. New regulations and laws requiring grid operators to make these numbers available is another priority.Anyway, I’m not going to dig into these technical issues. I have faith that, if an hourly REC market gets going, these kinds of questions will be ironed out. The ge