Zero or net-zero?

By Meredith Angwin

It’s not as much fun as you might think to stand in front of an auditorium of young people, speaking about energy, and knowing that they simply do not believe you. No, it wasn’t that they didn’t believe me about nuclear safety—although that may also have been the case—it’s that they didn’t believe me about the role of renewables. Specifically, they didn’t understand the difference between a net-zero energy facility and a zero-use energy facility.

The background

About two weeks ago, I spoke at  an assembly at Putney School, an “alternative” private high-school attended both by boarding students and day students. The school is located in Putney, Vt., the hometown of the state’s governor, Peter Shumlin. Most of the faculty and students at the school oppose the relicensing of the Vermont Yankee nuclear power plant, so it was a tough crowd.

The crowd was made even tougher by the fact that the president of the Vermont Public Interest Research Group, an antinuclear organization, had spoken to the assembly the week before. He had refused to debate me in an assembly, as Howard Shaffer described in his  recent View from Vermont post on this blog.

My problem at Putney, however, wasn’t with what I said about nuclear power. Instead, the problem was about what I said about renewables.


Whenever I discuss renewables, I say that I am in favor of them (which is true), but that they have several major drawbacks.

Renewables take up a lot of space—I usually illustrate this with a picture of Vermont Yankee, which is located next to Vernon Dam. In my picture, both facilities are visible:

Vernon Dam, with the Vermont Yankee nuclear power plant in the background.

I point out that Vermont Yankee makes 620 megawatts of electricity for 90 percent of the time, and that Vernon Dam makes 34 MW for 50 percent of the time. To replace Vermont Yankee with hydro power, there would have to be  20 to 30 dams the size of Vernon Dam. This would be clearly impossible to do in Vermont. (Vernon Dam is the one of the largest local dams on the Connecticut River, which is the largest river in this area.)

I also point out that solar photovoltaic and wind energy are “non-dispatchable” renewables. That means that these technologies start when they want to start, and they quit when they want to quit. No human can command the sun and the wind. Germany and Denmark have invested heavily in renewables, but both countries have found that their electricity grids becomes destabilized if they try to put more than 20 percent of these non-dispatchable renewables on them. With this constraint, the question becomes: What do we want for the other 80 percent of our electricity needs? Fossil, big hydro, or nuclear?

Many of the students at Putney School seem to think that we can have 100-percent solar—after all, they have a solar-powered fieldhouse.

The Putney fieldhouse

Putney School is justifiably proud of its net-zero fieldhouse. This super-insulated facility, with a solar orchard outside, cost more than $5 million, according to the “fundraising” tab on the fieldhouse Web site.

Putney fieldhouse

The Putney students simply didn’t believe me when I spoke about the 20-percent non-dispatchable renewables. The students didn’t understand the net-zero concept. I think it is important for nuclear power that people understand net-metering and net-zero.

Net-zero and the ghost batteries of Putney School

The Putney fieldhouse makes more energy than it uses when the sun is shining brightly. It sells the excess energy to the grid. When the sun is not shining, it buys energy from the grid, but buys only the amount it has sold before. In its interactions with the grid, the fieldhouse is net-zero in electricity use. (Or, at least, designed to be net-zero.)

When I talked about the limits of renewables, however, I received the following questions:

Our field house is 100-percent solar! How can you say we can only use 20-percent solar?”

“There’s a village in Spain that is 100-percent solar!  I read about it. That 20 percent makes no sense at all.”

I felt truly uncomfortable  standing in front of a large auditorium explaining that their terrific fieldhouse (and the village in Spain) are net-zero, not zero electricity use. The grid, with its baseload and dispatchable power, is backing up the solar. That fieldhouse couldn’t operate day and night without the grid standing behind it.

As I spoke, I could feel a wave of hostility moving toward me, and there was little I could do against it, except to keep telling the truth.

Later, at lunch, the physics teacher thanked me for my explanation of net-zero during the assembly. He told me that many students at Putney think that there is a bank of batteries under the floor of the fieldhouse, even though in fact there is no such thing. Still, the person who gave us the fieldhouse tour told us that “now we are standing above the batteries in the basement.” If I didn’t know any better, I would have thought he was serious. The tour of the fieldhouse occurred, unfortunately, after I gave my talk.

How’s net-zero working?

I wanted to know how the fieldhouse was working, and it was not easy to find out. I didn’t blame the students for being confused about the whole business.

For example, if you take the virtual tour at the Putney Fieldhouse site, it shows a bank of readouts in the fieldhouse that show energy use:

In the actual fieldhouse,  however, those readouts are not working. There are two other ways to find out the information, but you have to look for it.

I logged into the Energy Use tab using “student” as username and password (as instructed). I saw a set of readouts, but the information on the site was not very clear to me. I had better luck visiting the Web site of Maclay Architects, designers of the Putney fieldhouse. I logged into Putney Fieldhouse information on the architect’s site—and once again signed in as “student-student” (link is near the bottom of the page). In this case, I reached a readout with clearer labeling. Two electricity usage readings are “Import from Grid at 75,000 kWh” and “Export to Grid at 55,000 kWh”. Net zero?

Conclusion: For energy choices, people must know the facts, and sometimes it is hard to find them. Solar facilities are usually connected to the grid. The grid itself cannot be 100-percent solar or intermittent power, although any facility can be net 100-percent solar, with luck. I wish the Putney students knew that there are no batteries in the basement, and that the grid is the backup.

If you think talking about nuclear is hard, try talking about solar!




Meredith Angwin is the founder of Carnot Communications, which helps firms to communicate technical matters. She specialized in mineral chemistry as a graduate student at the University of Chicago. Later, she became a project manager in the geothermal group at the Electric Power Research Institute (EPRI). Then she moved to nuclear energy, becoming a project manager in the EPRI nuclear division. She is an inventor on several patents. Angwin serves as a commissioner in the Hartford Energy Commission, Hartford, Vt.

Angwin is a long-time member of the American Nuclear Society and coordinator of the Energy Education Project. She is a frequent contributor to the ANS Nuclear Cafe.

9 thoughts on “Zero or net-zero?

  1. Meredith Angwin

    First of all, I would like to apologize for any insult to the students who asked questions. I felt a fair amount of hostility when I was questioned, but I didn’t mean to imply the students were actively rude. I am sorry if that is the impression I gave. I apologize most sincerely for giving that impression.

    I understand that Cuerdon and Anon think that most students understand net-zero. I am glad that the students understand it. I have to say I received a different impression when I was there. I don’t think the students are rude and I deeply apologize if I gave that impression. However, I also don’t think the students understand about net-zero, and that is what I said in my blog and what I meant to say.

    If the students do understand about net-zero, I hope they also understand that the fieldhouse facility is basically a solar plant (from the grid’s point of view) and the grid can only take up to 20% of intermittent power such as solar and wind. I didn’t think they understood the grid and intermittent, and it is a very important thing to understand.

    The electricity numbers I quoted for the fieldhouse were the numbers I found on the web. I am glad the numbers are actually better! I am also always glad to see a tight, well-insulated building with a lot of daylight!

    The Japanese disaster. Having lived in earthquake territory myself, the idea of a Richter 9 earthquake and a tsunami that kills 20,000 people is almost too much to imagine. I was in a 7.2 earthquake (Loma Prieta in northern California), and it was a searing experience. The Japanese situation was so much worse, and completely heart-rending and terrifying. The nuclear accident and subsequent evacuations are also very upsetting. My best to your Japanese students and to everyone in Japan.

    I agree that all energy choices must stand shoulder to shoulder, and not toe-to-toe!

  2. Anon

    I disagree with most of this article. I feel that most of the students did understand about the that the power grid is the back-up but are hopeful that we can work around it. I also do not like your rephrasing of the question asked in assembly because although I understand some rephrasing is necessary, the questions you give make us seem much ruder than we were.
    Re-reading this paragraph makes me sound exactly like what I was trying to avoid so I apologize,

  3. Don Cuerdon

    Hi, Meredith. Thanks for the reminder that I need to update the Field House website with some of the latest data. On our regular school website I’ve been posting updates on the building such as this one: on our first year of montoring. In our first full year, the Field House used 48,374 kWh of electricity while the sun-tracking photovoltaic cells that help power it have produced 51,371 kWh. So we’re a little better than net-zero energy. Because the Vermont State Legislature enacted some green energy incentives right about the time the building opened, we buy our kilowatts for about 13 cents each and sell our “green” kilowatts back for about 6 cents more than that. Our final electric bill (and the building is all electric—no other fuels are used to heat, light, etc.) was a credit for $3800, which was mostly a nice surprise. That wasn’t a design parameter.

    I’m not sure how much electricity other buildings of this size would use in a year, but I’ll bet ours is lower because of all the passive solar, daylighting, and insulation technology that went into it. Yeah, some of our kids think it runs on batteries. Some also believe we have Civil Defense tunnels between the buildings. Kids say the darnedest things sometimes, but ours don’t leave our “posh” school without knowing how to milk a cow, so I’m sure they’ll get the rest sorted out before it’s too late.

    Sorry about the hostile crowd. Some of our Japanese students had a rough time over March break, which then affected all of us. I’m sure none of them want to freeze in the dark. But they also want a safe energy future, so it’s important that we all remember that we’re on the same side, shoulder to shoulder, and not toe to toe. I’ll go gently remind them now.

  4. Paul Lindsey

    Not only is the grid the backup, but the value of the electricity is different depending on the time of day. I expect that when the PV panels are producing most of their output, the electricity value is low. In the late afternoon and early evening times, especially in the winter months, the wholesale & retail values are higher. So Putney (and every other PV installation where “net metering” is allowed) is getting their electicity at a subsidized rate.

  5. David

    Excellent, and this is the reason why most people are opposed to Nuclear. They do not see it as necessary because they truly believe, because they have been carefully taught, that Solar and Wind CAN do the job. So why risk dangerous nuclear when we can do the work with safe S&W? They have been taught this over and over by most media, teachers and authority figures (and cartoons – simpsons). Without time or motivation (i.e. the power goes out) to look deeper they don’t examine what they have been taught. So, as a result, people who challenge this are considered liars or at least as having a suspect motive.

    This fundamental error in their thinking will, I fear, only be reconsidered when the rolling blackouts come or the price of electricity goes beyond the pale and they hear people blaming “speculators.” Populism works through mis-direction and is nearly always a manipulation.

  6. Bill Eaton

    One of the sad but true facts associated with modern education is that early teaching of fundamentals is often bypassed in deference to topical education. Examples of prevalent gaps in education during late elementary and middle school experiences today include civics, American history, algebra in middle school, trigonometry, and English composition. Basic sciences are often translated into lab experiences instead of fundamental memory based rote, which is the precursor to later application and integration of scientific principals into other fields. Modern kids are conditioned to believe what they here the most of instead of what they have studied or experienced, and they are not confronted with with the challenge to establish independent positions based on principles and truth often enough. Sadly, a posh private school should be a source of deeper education. I’ll bet that’s how the administration justifies tuition. Great article!!!

  7. Meredith Angwin

    I think that the physics teacher works hard to share these concepts, and that some (many) students get them. However, many do not. The fact that you have to dig on the web to get information does not help the situation. Also, as Hargraves points out, the information on the web is unclear.

    However, the ultimate problem is that people think that the fieldhouse could just be duplicated as many times as necessary, and presto, we would be all solar! Anything about the role of the grid, or the issues of renewables on the grid, is missing from the conversation.

  8. Robert Hargraves

    The virtual “meters” are very confusing and inconsistent. kWh over what time period? All the same? I think only the power company knows for sure.

  9. donb

    Here is a simple question for those who don’t understand: If the fieldhouse uses no electricity, why is it tied to the grid at all?

    If anyone should answer “To sell excess electricity to the grid,” say “But the fieldhouse uses all the electricity it generates, and still needs more.”

    While this discussion may not get the point across, it might get some thinking.

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