NanoCharging: Cutting Your Charging Emissions with Weather Automation
We all know EV’s have zero tailpipe emissions, but what about the emissions needed to generate the electricity that powers the EV? If your local electric grid is mostly coal-powered, is your EV still better than driving an internal combustion engine?
The short answer is that because electric motors are so much more efficient than internal combustion engines, even a coal-powered electric car has about half the emissions compared to the average internal combustion car.
But a coal-powered grid is the worst-case scenario. Most grids are being powered by growing amounts of emissions-free renewable energy, and cars operating in these regions will be cleaner. An EV that charges on the California grid, for example, can drive more than 5x as many miles for the same amount of emissions as the average US gasoline car. [1]
That in itself should be reason to celebrate, but in this post we’ll show how drivers who charge overnight can decrease their carbon footprints even further with nothing more than some clever automated scheduling that maximizes the use of renewables on the grid. If you could cut your driving emissions footprint by another 30% without buying any new hardware and without changing your behavior beyond using a smart app, what is stopping you?
Beyond Smart Charging: NanoCharging
Many EV drivers who charge at home have heard about Smart Charging: switching to an electricity plan with peak and off-peak hours, then charging only at off-peak hours (typically at night after midnight). Fewer drivers have fiddled with their car or charger controls enough to configure it.
Smart Charging can save hundreds of dollars per year on electricity costs (more on that in an upcoming post), but it typically optimizes only electricity costs, not emissions. In other words, a simple timer like “turn on my charging at midnight” can never be emissions-smart because the times of cleanest energy change from day to day due to factors like grid demand and the weather.
While both classic “Smart Charging” and “NanoCharging” will leave you fully charged in the morning, a NanoCharging schedule can do it with significantly less CO2 emissions.
Some grids such as California’s are becoming cleaner because renewables like solar and wind have become the cheapest sources of energy so it now makes financial sense to build more solar and wind. Renewables, however, are intermittent. Despite complementary behavior like wind tending to be more prevalent at night when solar goes offline, you still need to be aware of what sources are generating at what times to be charging your car during the periods of cleanest energy. And because these periods depend on the weather, they change every night.
A simple Smart Charging schedule might set your car to start charging at 12am when your off-peak billing period starts and just go until full. An emissions-optimized Smart Charging schedule, on the other hand, would check the local grid’s nightly energy-weather forecast [2], find the periods of most wind, then charge from, say, 1:30am — 1:45am, pause, continue charging from 2:15 until 3:30am, continue from 3:45–4:00am, and so on until your battery is full before you leave for the day.
We call a schedule of many of these small emissions-optimized charging blocks “NanoCharging.”
While both a classic “Smart Charging” schedule and a “NanoCharging” schedule will leave you fully charged in the morning, a NanoCharging schedule can do it with significantly less CO2 emissions. At Swing Electric, we have built a NanoCharging app for California Tesla drivers that will automatically schedule charging during the blocks of time your local grid is cleanest. Let’s look at some real examples.
Looking at Emissions Data and Variability
Let’s now look at how much NanoCharging can lower the carbon footprint of EV drivers across two California cities: San Francisco / Bay Area and San Diego. The following chart shows average electric grid emissions in these cities by hour of day in August 2020.
The vertical lines show variability for each hour: how much emissions tend to wiggle above or below the average on a given day (for the data nerds, the vertical lines plot the standard deviation). We talked earlier about how the times of cleanest energy can vary from day to day depending on the grid’s weather — the vertical lines show us how much they typically tend to vary.
For example, both San Francisco and San Diego have 8 or 9am as the hours with the lowest average emissions. However, these hours have a wide range of variability compared to 3 or 4am, which have slightly higher average emissions but more consistent emissions.
If your EV has a simple Smart Charging timer and you need to pick a few constant hours to start charging every night, which do you choose? You can have the lowest average emissions by charging at 8 and 9am (assuming you’re a late commuter and don’t need your car before 10am), but there will be many days where you will have higher emissions than if you started charging earlier at night. Every night will be a bit different, so ideally your Smart Charging schedule can adjust according to the daily “energy weather.”
Let’s add the day of highest emissions (red) and day of lowest emissions (blue) on our emissions plots:
If you were charging in San Francisco on August 18th (red line), you would want to charge from 1am-3am. If it was August 27 (blue line), you would want to charge from 3am to 5am. Only by knowing the daily weather on the grid can you find the best times to charge.
By considering the grid’s weather, you are given the choice of how much emissions your driving will produce.
We can even go a step further and use this information to decide what day to charge. If your EV battery was down to 42% and you were considering charging overnight but the grid weather forecast told you emissions would be 30% higher tonight than tomorrow night, would you still charge? It would certainly be quite reasonable to do so if you were anticipating a long trip and needed the range, but how about on a night when you weren’t planning on anything out of the ordinary the next day and 42% would suffice?
By considering the grid’s weather, you are given the choice of how much emissions your driving will produce. If you have range flexibility, you can choose to wait a day or two and emit less. If you don’t (and don’t be ashamed, we all have busy schedules sometimes), you can still get a full charge while minimizing emissions by using a NanoCharging schedule that finds the cleanest blocks of time.
Introducing Swing Electric: Our Free NanoCharging App
EV drivers who charge overnight can use smarter scheduling to charge only when the grid is emitting the least [3]. Renewables on the grid are intermittent — they are constantly turning on and off, changing the emissions on the grid change every few minutes. Rather than fighting that fact, we can work with it by using real-time data and connectivity to develop “NanoCharging” schedules that charge only during small blocks of time that line up with the wind (at night) or the sun (during the day).
If your car needs only a few hours of charging and it is parked overnight, it doesn’t make a difference to you which hours the charger is turned on. But by being smart about charging hours (or using software that automates it all), EV drivers can make a huge difference in their emissions footprint.
At Nanogrid, we are building technology that makes our homes and vehicles greener by intelligently integrating with renewable energy resources. We used our smart energy integration platform to build Swing Electric, our free NanoCharging app for EV drivers who charge at home. By using Swing, EV drivers can charge during the cheapest, off-peak hours that also have the fewest emissions. Swing tells you both how much your electricity will cost and how much CO2 will be emitted for each charge session, giving you the tools needed to minimize your personal carbon footprint while you sleep.
We are happy to open our beta today to all California Tesla drivers, no special hardware required. Just create an account, connect your Tesla, and let us automate everything against your local energy weather.
We hope you give it a try by signing up at SwingElectric.com. Let us know how much you’re saving by using Swing!
Footnotes:
[1]: On the dirtiest US electric grids, an EV operates with emissions equivalent to a 40 miles-per-gallon (MPG) gasoline car. Meanwhile, the average gasoline fuel efficiency in the US is around 22 miles-per-gallon. In states with high levels of renewables like California, an EV operates with average emissions equivalent to a 120 MPG gasoline car.
[2]: Building a “Energy Weather Forecast”. In California, we have a few regional utilities. The big ones are Pacific Gas & Electric (PG&E) serving much of northern California, Southern California Edison (SCE), and San Diego Gas & Electric (SDGE). Some municipalities own their own electric utilities such as Los Angeles Dept. of Water and Power (LADWP) and Sacramento Municipal Utilities District (SMUD).
Because the grid is interconnected, all of these utilities need to carefully coordinate and balance their supply and demand. An organization called the California Independent System Operator (CAISO) exists to supervise this activity. There is much more to this story, but what is important to us right now is that CAISO monitors how much power is being generated from what sources at any given time anywhere in the state. This real-time information is publicly available online at http://www.caiso.com/TodaysOutlook/Pages/supply.html and can be used to build an ‘energy weather forecast’ of how clean different parts of the California grid are or will be up to a few days into the future.
[3] This post has covered only grid emissions. We’ll cover the complications of home solar and those green electricity rate plans in a future post!
