Beyond Net Zero, Part I
By Dan Bihn
NOTE: This week and next, Energy Currents is excited to feature a two-part series by one of Enerdynamics' long-time facilitators and Smart Energy specialist Dan Bihn. This content was originally posted in January 2019 by Solar Oregon. Our thanks to both Dan and Solar Oregon for allowing us to share this valuable insight with our readers!
Net metering was a great start. It helped launch the solar electric industry. Net Zero Energy is even better. It brings together onsite renewable power generation and energy efficiency. But neither one will help solve the next challenge our energy system faces — affordably accommodating large amounts of solar and wind energy.
Typical U.S. Net Metering Setup (photo by Dan Bihn)
To do that we’re going to have to get smart.
Back in the day, net metering of rooftop solar was a great idea. In the early 1980s, when net metering laws started showing up, solar panels were expensive. Selling energy back to the grid at full retail rates seemed like an appropriate reward for early adopters whose investment was often paid off more by environmental goodwill than financial returns. The logic was sound and the results have been delightful.
And net metering was easy. Fortuitously — but unintentionally — most legacy power meters spun backwards when power flowed back on the grid. So the meter did all the math in its little mechanical brain and the meter reader’s job didn’t change. Only the billing software needed to be upgraded a bit.
If your solar system is designed to produce as much as you consume over an entire year, you have a net-zero system. And you can say you make all of your own electricity. But that means you’re using the grid as your battery — charging it when the sun shines, then discharging it when you need electricity. And the grid is not just a dinky little day-to-day PowerWall sort of battery. It is a full-on seasonal battery that you can charge in the summer and discharge in the winter. It’s like having your own personal pumped hydro system.
But that battery is running out of capacity. In 2019, the world is different and the days of using the grid as our personal battery for our rooftop solar energy are coming to an end.
Today, our sunny neighbor to the south routinely puts close to 18 gigawatts of solar energy onto the grid. More than a third of that comes from net-metered rooftops. On mild, sunny California weekends, low demand and high solar production combine to exceed the grid’s ability to accommodate all of that carbon-free energy. When that happens, California’s grid operator (CAISO) is forced to temporarily stop large solar farms from producing energy from their expansive arrays. Electrons excited by sunlight are left to bounce around inside the solar cells, meaninglessly heating the panels.
In 2018, more than 1.5% of California’s solar energy that could have gone to market was left unharvested, rotting on the photovoltaic vine due to lack of demand. (That number is about half what it was in 2017, in part due to the Energy Imbalance Market.) Naturally, when the large solar farms are producing electricity, so are regional rooftop solar systems. On those hours, essentially every kilowatt exported from net metered roofs directly leads to an equal forced output reduction from those large solar farms. No net benefit.
Can we do better?
Many people think the next steps toward a low-carbon future are net zero energy homes and buildings (often abbreviated ZEH and ZEB, where the N in ‘net’ is not only silent, but invisible). While these programs can be a great way to achieve our individual decarbonization goals, they could be making it harder for the whole system to do the same.
2002 National Renewable Energy Lab (NREL) net zero energy home (photo by Dan Bihn)
Program details matter. Next week on Energy Currents we'll head to Japan to look at an example of what they're doing and provide some interesting insights into ZEH and ZEB.
Want to learn more about the future of the energy industry and/or how distrubuted energy resources are changing the energy landscape? Enerdynamics offers two great seminars: The Future of the Utility: Evolving Customers, Changing Technology, Revised Regulation, New Business Models, and Growing Opportunities and Distributed Energy Resources and Microgrids: Applications, Technologies, and Economics. Email firstname.lastname@example.org or call 866-765-5432 ext. 700 for more details.