Intermittent or variable: Are our wires crossed on renewables?

[kristopher]

Intermittent or variable: Are our wires crossed on renewables?

By Craig Morris on 29 January 2014

...

The use of “intermittent” certainly is well established for renewables; see this Wikipedia entry, for instance, which only mentions nuclear and coal in terms of reacting to intermittent energy – not as intermittent sources themselves. Likewise, “variable” sounds like the energy source is “capable of varying,” but wind and solar are not dispatchable. Taken literally, they are varying, but not variable.

But recently, someone finally took the time to explain to me why a clear distinction should nonetheless be made – with conventional plants being called intermittent and wind & solar called variable. The idea is that, while production of wind and solar power fluctuate (to use the German term), giant amounts of renewable generation capacity do not simultaneously go off-line.

Conventional plants can fail quickly. In a recent storm that hit Europe, the social media world was concerned about wind turbines being blown away, but I could not find any news of such a thing happening. We do know that the Ringhals nuclear plant, with a capacity of 878 MW, failed completely, however, as one of its blocks did again just a few weeks later.

In North America, the recent Arctic cold knocked out power plants across the country, with 39,500 MW going off-line in a single day within the PJM grid, 21 percent of PJM’s total generation capacity. Roughly 19,000 MW was coal plants, followed by 9,000 MW of natural gas turbines, 1,600 MW of nuclear (probably a single plant), and “nearly 1,500 MW of wind.” (One wonders whether it was the wind turbines themselves that failed or grid connections to the turbines.)

The PJM area was not alone, either. In Texas, 3,700 MW of conventional capacity had to be shut down during the polar vortex...

http://reneweconomy.com.au/2014/intermittent-variable-wires-crossed-renewables-27265

[quadrature]

1. misleading comments

second paragraph, last sentence contains.......
'do not simultaneously go off line'.
.........not exactly............

it is common for, solarPV and wind, to
..--> BE <--.. off line at the same time.

[kristopher]

2. Are they?

We can measure that, and it turns out your claim isn't correct.

Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time
Open Access Article

http://dx.doi.org/10.1016/j.jpowsour.2012.09.054

Abstract
We model many combinations of renewable electricity sources (inland wind, offshore wind, and photovoltaics) with electrochemical storage (batteries and fuel cells), incorporated into a large grid system (72 GW). The purpose is twofold: 1) although a single renewable generator at one site produces intermittent power, we seek combinations of diverse renewables at diverse sites, with storage, that are not intermittent and satisfy need a given fraction of hours. And 2) we seek minimal cost, calculating true cost of electricity without subsidies and with inclusion of external costs. Our model evaluated over 28 billion combinations of renewables and storage, each tested over 35,040 h (four years) of load and weather data. We find that the least cost solutions yield seemingly-excessive generation capacity—at times, almost three times the electricity needed to meet electrical load. This is because diverse re- newable generation and the excess capacity together meet electric load with less storage, lowering total system cost. At 2030 technology costs and with excess electricity displacing natural gas, we find that the electric system can be powered 90%–99.9% of hours entirely on renewable electricity, at costs comparable to today's—but only if we optimize the mix of generation and storage technologies.

http://www.sciencedirect.com/science/article/pii/S0378775312014759

[quadrature]

3. the storage, never shows up.

face reality.
wind and solarPV.
they want to sell electricity
when they feel like selling it.

and when they don't feel like (or can't)
supply electricity,
they want it to be someone-else's problem

[kristopher]

4. On the unexpectedly intermittent nature of nuclear power.

On the unexpectedly intermittent nature of nuclear power.

FirstEnergy works on Pennsylvania Beaver Valley reactor transformer
Sat Jan 25, 2014

Jan 24 (Reuters) - FirstEnergy Corp said on Friday it
is continuing work on the replacement of a transformer at the
892-megawatt Unit 1 at the Beaver Valley nuclear power plant in
Pennsylvania.

...

A First Energy spokeswoman could not say when the unit
would likely return to service but noted "the outage is expected
to be shorter than a typical refueling outage, which is normally
about 30 days."

"We are well into the replacement process. This is a large
component that requires some time to replace," said spokeswoman
Jennifer Young.

A spokesman at the U.S. Nuclear Regulatory Commission, Neil
Sheehan, said "Work is continuing on the installation and
testing of the new transformer ... While the work may be taking
slightly longer than anticipated, the delays would not be
considered significant."...

http://in.reuters.com/article/2014/01/24/utilities-operations-firstenergy-beaverv-idINL2N0KY1EC20140124

Well, that's Ok. It isn't like it happens a lot.

Calvert Cliffs Nuclear Power Plant units shut down Tuesday night
Triggered by tripped electrical breaker

By AMANDA SCOTT

Both units at Calvert Cliffs Nuclear Power Plant were automatically shut down Tuesday night due to electrical problems.

About 9:25 p.m. Tuesday, units 1 and 2 were shut down due to an electrical malfunction on the non-nuclear side of the plant, according to a Constellation Energy Nuclear Group press release. All safety systems responded as designed and the plant went offline as expected, the release said.

On Wednesday, CCNPP spokesman Kory Raftery said an electrical bus that is connected to components on both units was tripped, or went offline, resulting in the automatic shutdown. Raftery said the issue is similar to a breaker in a home getting tripped and the electricity in that room not working.

...“The preliminary cause of the loss of the electrical supply is snow and ice impacting a ventilation louver filter on the building housing the supply,” Sheehan wrote, “resulting in it coming into contact with the supply and thereby tripping the breaker.”...

http://www.somdnews.com/article/20140124/NEWS/140129488/1074/calvert-cliffs-nuclear-power-plant-units-shut-down-tuesday-night&template=southernMaryland

So, three nuclear reactors at two plants unexpectedly shut down for a not insignificant period of time, in the same region, during a major freeze event.

Anticipated variability vs unexpected intermittent - that's a distinction that the nuclear industry would rather people didn't appreciate.