Sunday, September 4, 2016

Aliso Canyon and Duck Curve Demand in SoCal

Subtitle:  California is very fortunate with a mild Summer thus far

An interesting article from 29 August, 2016 in the Ventura (CA) Star newspaper, on the issue of natural gas shortage and its impact on electricity production in California.  SLB has had several articles on this, links here.  

The journalist, Tom Elias, takes the position that the entire threat of blackouts was false, and states it was "a lie" and "a bunch of hooey."

The Star article is "Blackout threats exposed as power stays on"  see link 

Mr. Elias is wrong.  

I left a short comment on his article, shown below:

"Daily consumption of natural gas is not the proper metric. Peak demand for fuel to gas-fired power plants occurs on an hourly, and sometimes shorter basis. 

The important concern is the ability to rapidly ramp up the natural gas-fired plants in the late afternoon, typically between 5 and 7 pm. 

A case on point is from Saturday, September 3, 2016 when CAISO reports the total production, excluding wind and solar, increased almost 3,300 MW in the one-hour period 18:00 to 19:00 hours (6 to 7 pm).   [Update 5 Sept 2016:  yesterday, 4 Sept 2016, the duck curve ramping rate reached 3,700 MW in the same 6 to 7 pm hour.  graphics shown below. -- end update]

For those who want to understand more on this issue, search for "duck curve" and CAISO. Plenty has been written."   -- end of Sowell comment 

A bit more discussion is probably in order. 

There are at least two ways that a shortage of natural gas can occur in the region: sustained high demand for electricity such as in a heat wave that lasts for days, and a rapid increase in demand such as occurs daily when solar power production declines in the late afternoon. 

A combination of late afternoon, imported power curtailed for any reason, hydroelectric power not available (perhaps due to the ongoing drought), a high pressure system stalls over the state causing wind to decline or even stop, or an unplanned outage of high-efficiency combined-cycle gas turbine plants, will cause the hourly natural gas demand to surge. 

Thus far, September 4 of 2016, the state has had very good fortune in all those categories just mentioned.   No severe and prolonged heat waves happened.   We have a bit of water in the lakes so some hydropower is available.  

Nearby is a chart from CAISO, with my additions to illustrate the point. The green line, known as the "duck's belly and neck" is the total load less wind and solar power.  The portion circled in red shows the greatest change in that load, over a one-hour period.  To my knowledge, that 3.3 GW increase in one hour on 3 Sept 2016 is the highest to date on the CAISO grid.  

The rate of change in the late afternoon, or ramping rate, is one of the chief concerns of planners and state agencies.   As more and more solar power is added to the grid, that ramping rate will also increase.  

And for the nuclear cheerleaders, I note here that adding nuclear power to the grid will not alleviate this problem.  

So, Mr. Elias is wrong.  We do need natural gas storage, if not from Aliso Canyon then from other sources.  We have been very fortunate thus far in California.   The weather has been unusually cool and mild so far this summer.  However, September is the month that usually has the highest temperatures and we can expect at least one prolonged heat wave. 

Update 5 Sept 2016:  more recent duck curve ramping rates.   Sunday, 4 Sept 2016 shows 3,700 MW ramping rate from 18:00 to 19:00 hours.  See areas outlined in red below. -- end update

Roger E. Sowell, Esq.
Marina del Rey, California
copyright (c) 2016 by Roger Sowell - all rights reserved 

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