Renewables at 90% only IF grid-level storage comes first

Renewables can't be a 90% unless we have grid-level storage

Renewable installations are growing fast, but we can't have huge percentages of wind and solar on the grid unless we first have grid-level storage.  With the exception of pumped storage, grid-level storage does not exist at this time.  (No, I don't count an occasional 2 MW project as "the answer.")

We can't grow wind and solar to a higher percentage on the grid than their capacity factor implies, unless we have storage. Moving to 50% wind on the grid is not possible, without utility level storage.  

The explanation follows, based on the New England grid.

A year on the New England grid (2008)
Shows the necessity of being able to dispatch electricity
Note rise in gas usage while nuclear plants refuel
Click to enlarge

Five million down and five million up (natural gas takes the lead)

In a guest post on January 7, Michael Twomey of Entergy used grid operator (ISO-NE) data to show that between 2014 (when Vermont Yankee was running) and 2015 (when Vermont Yankee was closed), nuclear kilowatt-hours decreased by about five million MWh and gas-fired generators increased their output by almost exactly the same amount.  Natural gas went from 46,200,000 MWh to nearly 51,900,000 MWh.  Nuclear kWh nuclear went down by almost the same amount of MWh.

Click to enlarge table

Wind and solar growing fast: Jeff Schmidt's comment

Looking at the table above, you can see that wind went from 1,892,000 MWh to 2,135,00 MWh, growing by approximately 243,00 MWh, and solar grew from 327,500 to 436,200 MWh, approximately 108,700 MWh.

This rapid rate of growth (though still only adding up to 2.4% of the power on the grid), prompted Jeff Schmidt to write this comment on the Twomey article:

"This article seems to dismiss the growth of wind and solar. While I am pro-nuclear, and think that nuclear needs to play a vital role in our future energy mix, I think the author of the article is neglecting something important - growth of wind and solar.

It's true that they are still small. But, if you look at the year-over-year growth rate, as shown by the statistics provided by the ISO and called out by Mr. Twomey, we see that Solar grew 33% in a year, and Wind grew 41%. Of course, one can't predict future growth rates based on one year, but IF wind and solar can keep up strong growth like that, they could conceivably become a very large proportion of the New England energy mix inside of 10 years.

It's true that it's likely an overly optimistic and simplistic projection, but just for the sake of argument, if they can keep up that growth rate, then 9 years from now, Wind could produce about 50% of the energy, and solar about 5%. If you projected it to 10 years instead of 9, that would account for more than 100% of current grid generation.

However, at the same time, it's very likely that at some point, Wind and Solar's growth must slow. Still, it's a valid point to concede that Wind and Solar, while currently small in absolute terms, are actually growing at a pretty fast rate."

Why renewables can't keep growing--unless we have storage

I wrote the following response to Schmidt.  I oversimplified, but I am also worried that "we can't grow wind and solar" arguments are often based on cost, or on complex technical issues that are hard to explain.  So, here's my oversimplification.  Basically correct, but oversimplified.

Basically, we can't grow wind and solar to a higher percentage on the grid than their capacity factor implies, unless we have storage. Moving to 50% wind on the grid is not possible, without utility level storage.



Jeff
I wrote about Vermont's plans to be 90% renewables in today's blog post. Of course, renewable growth from 1 to 3 to 5% is possible and looks great. However, it simply does not scale. Let's oversimplify a little, though not a lot.

Most of Vermont is one weather pattern, with some exceptions. Hot, dry and sunny...all over Vermont. Windy at night...all over Vermont. Cold and windless....all over Vermont. Now, obviously, the mountains are different from the river valleys and so forth, but the statement "weather is the same all over Vermont" is far closer to true than its opposite would be.

Okay. We cannot turn wind on and off. Let's say that wind has a 30% capacity factor. For wind to grow to 30% of the electricity supply overall, that means when wind is on the grid (the wind is blowing in Vermont)...the grid has to be 100% wind. Without this high percentage when wind is available, wind is not going to be able to be 30% of the electricity, overall. So we have to build a lot of wind to get wind to 30% of the electricity supply, and we have to turn everything else off if the wind is blowing.

Well, what if we build more wind? If we do that, when the wind is blowing....what then? We have to curtail some of the wind, because the grid can't take more than 100% of wind. So, without grid level storage, wind reaches a VERY hard stop at 30%.

Well, it is windier in the mountains, and the southern part of the state gets less wind and so forth and this is an oversimplification. And the grid requires more power in the day, and less in the night (when the wind usually blows). So it is quite complicated in reality. But the basics remain.

IF you can turn things on and off, you don't reach this sort of hard stop. 100% of the electricity from natural gas...this could work. No "hard stop" involved. 100% from nuclear...well, current nuclear doesn't follow load well, but there is no "hard stop" involved, where you have more nuclear than you can use on the grid. You don't need grid level storage for nuclear, just plants that follow load a little better. And so forth.

This is why I am so cynical about the Vermont energy plan. The plan is kind of "We don't just hope for miracles, we expect them."
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Jeff Schmidt has two guest posts at this blog:

The Nuclear Safety Paradox, which describes how experience (such as building new nuclear plants) increases safety.

Flawed Analogies, which describes the analogies nuclear opponents made in a debate against nuclear energy.

Illustration

The illustration showing the need for dispatchable power
From Sustainability presentation by David Lamont
Vermont Department of Public Service
October 18, 2010
Presentation is no longer on the web, but I had saved it to my computer.

Trojan Cows and Grid Facts: Op-Ed

Non-Trojan Cow

The Cow

On July 1, a group of people opposed to the continued operation of Vermont Yankee protested at the nuclear power plant’s gates. One prop they used to dramatize their belief that there are better energy options than nuclear power was a hollow “Trojan Cow” they pulled to the demonstration. Some protesters pulled mock solar panels out of the cow, while others held whirligigs representing wind turbines. The cow sculpture even included a representation of manure, representing “cow power” energy produced from farm methane. The theme was clear: Vermont Yankee will be replaced with renewables.

Well, that is simply not true, at least in the foreseeable future. Closing Vermont Yankee will not bring a burst of renewables to market to replace its power.

Grid Power

Closing Vermont Yankee would mean buying more power from the New England grid to make up for Vermont Yankee’s supply. Grid power is approximately 58 percent fossil fuel, 28 percent nuclear and 12 percent hydro plus renewables. Wind, solar and farm methane together account for less than 1 percent of the power generated in New England.

What would closing Vermont Yankee mean? More solar power on the grid? No. With or without Vermont Yankee, renewables are expensive, and they are not coming on line quickly.

On the other hand, fossil fuel plants are abundant suppliers to the New England grid, supplying the majority of grid power. Many fossil fuel plants operate only part-time. The part-time plants run when they are needed to satisfy the power requirements on hot summer days or cold winter evenings. They also operate when nuclear plants are down for refueling.

The New England Grid responds to nuclear refueling
From Vermont Dept Public Service  presentation

If Vermont Yankee closed, existing fossil fuel plants would compensate by running longer hours and making more power. If the Vermont Yankee protesters had wanted to stage a more accurate dramatization, they would have pulled a model of a gas or coal plant from their Trojan Cow’s belly, not a cardboard solar panel.

Renewables: Too Slow, and Too Expensive

Or perhaps the demonstrators were claiming that shutting down nuclear plants will bring more rapid development of renewable energy, even if we’re forced to use more fossil fuels for a “short while.”

Well, a “short while” is likely to be very long.

For example, the Vermont state energy plan calls for the state to meet 90 percent of its total energy needs from renewable sources by 2050. That’s an ambitious goal considering that Vermont does not meet its current renewable energy goals and has no prospects of meeting them in the near future. The Vermont energy plan established a goal of having the state use 20 percent of its electricity from renewable sources by 2017. Even using optimistic assumptions about project completion, the state will attain only the 16 percent mark in by that date. In 2009, the state had 13 percent of its electricity from renewables (mostly in-state hydro). A growth of 3 percentage points over eight years ( 13 to 16%, 2009 to 2017) is not very impressive.

Perhaps the rate of growth of renewables is accelerating? Not really. Last year, the Vermont Legislature voted against having an aggressive Renewable Portfolio Standard for Vermont. Such a standard might raise the percentage of renewables in Vermont, but it would also raise Vermont electricity rates to unacceptable levels. Renewable growth is slow in neighboring states for similar reasons. In short, closing Vermont Yankee would have the regional result of requiring more fossil fuel to supply the New England grid.

Vermont Is An Island?

Within Vermont, many anti-nuclear activists don’t seem to care much about the regional issue. They often say that the power from Vermont Yankee doesn’t matter to Vermont, because “Vermont is no longer using any Vermont Yankee power.”

Not true. In March of this year, the power contracts between Vermont utilities and Vermont Yankee ended. Vermont utilities no longer buy Vermont Yankee power. However people in Vermont are still using Vermont Yankee power.

That sounds weird, but realize that buying power and using power are different, because power from different sources blends together on the grid. The supply on the grid depends on the power plants, transmission lines and end-users. These don’t change when contracts change.

Buying and Paying

Who pays for the power is a different matter altogether: Payment depends on agreements made between plants and utilities and regulators. The day after Vermont Yankee stopped selling power to Vermont utilities, Vermont consumers used the same actual power mix as they had used the day before. However, on that day, Vermont consumers began paying for power in a different manner. Among other changes, Vermont consumers began paying for Seabrook power, according to a contract between Green Mountain Power and Seabrook. This did not mean that Seabrook power suddenly began streaming into local power lines.

Once again, we have to take into account the regional nature of the grid. Power contracts determine payment methods, but contracts don’t determine power routing and use — that is determined by plant availability and geography.

Power blends together on the grid. If a plant goes off-line, other plants take up the slack. When nuclear plants go off-line, fossil fuel plants step up and produce replacement power.

(Note: Howard Shaffer wrote an excellent description of the grid at his recent guest post: Where's the Magic Switch?)

Deception 

Protesters used a Trojan Cow to suggest that if Vermont Yankee closed, renewables would take its place. Perhaps the use of a Trojan animal was more apt than the demonstrators intended. After all, the original Trojan horse was designed to deceive. In this case, the people that the demonstrators are deceiving about the consequences of closing Vermont Yankee start with...themselves.

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This is a slightly edited version of an op-ed I wrote for my local paper, the Valley  News.  I wrote this op-ed about the July 1 "Trojan Cow" protest at Vermont Yankee. It appeared in the Valley News on Sunday, July 29, but the Valley News puts very little of its content on-line.   I felt this op-ed fit in well with Howard Shaffer's recent blog post about the grid: Where's the Magic Switch.

You can watch a three-minute video of the demonstration on YouTube.