tbleakne
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Grid scale projects in California and net grid demand

Mon Mar 16, 2015 8:55 pm

When I first got my LEAF, and folks asked me about my carbon footprint, I told them that by charging after midnight in CA my car was often drawing surplus wind power. I could claim my carbon footprint for charging in my garage was near zero.

With the advent of the large new grid-scale solar projects in the desert the last few years, including the monster thermal tower project at Ivanpah near the NV border and Primm, the daily production curves are showing dramatic change. CAISO (California Independent System Opeator) is now talking about the Duck Curve, which plots the expected difference between total load and production from variable production sources, including solar and wind:

Image

The total production of grid-scale solar in CA is now over 5 GW for several hours near midday. Much of the grid-scale solar tracks the sun, so it has a nearly trapezoidal power distribution that ramps up rapidly in the morning and declines rapidly in the late afternoon. Our own individual residential solar adds another 1.2GW of capacity, plus about 1 GW of non-utility commercial solar installations, but CAISO sees these latter two only indirectly as reduced demand from its member utilities. These non-grid-scale installations are mostly non-tracking, so their power curves are more bell-shaped.

CA has well over 5 GW of installed wind power capacity, but because the winds are variable, production often peaks at less than 1.5 GW.

More grid-scale solar is planned for CA, but projected increases in wind power are much more modest. The reverse is true on the national scale, where wind power has jumped to an impressive 4% of total production in just a few years. Wind is over 25% of Iowa's production (but 60% is coal).

The above graph projects that conventional production, which is now largely natural gas, will often reach a minimum in the afternoon, not overnight. However, the example shown is for March, and total demand in the summer is higher, typically 45 GW, so the summer minimum may still occur at night.

My conclusion is that for at least part of the year the lowest-carbon time to charge our cars may move to late morning or afternoon. It will be interesting to see if and when incentives are tilted in that direction. EVs used for commuting will need a lot more charging available at work locations.

CAISO is worried that it will be difficult for the sources it controls to ramp up and down to match the Duck Curve. Eventually with deep solar supply we are going to need grid-scale storage, which I will discuss in another post.
LEAF Ocean Blue SL, "100 % Electric" decals, Delivered June 3, 2011
Sold June 2014 27K miles, 18% capacity loss, 1 bar, 5.0 mi/kWh.
Solar 4.6 KW DC with both string and micro-inverters.

smkettner
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Location: Orange County, CA

Re: Grid scale projects in California and net grid demand

Tue Mar 17, 2015 8:37 am

Need battery storage to move available solar from the belly to the head.
Really going to alter the TOU pricing with off-peak being closer to noon and shift on-peak to 7p to 11p. Could hurt home solar payback unless battery is included.

Issues with over generation and ramp up is probably overrated. JMHO.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV

tbleakne
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Re: Grid scale projects in California and net grid demand

Tue Mar 17, 2015 12:09 pm

Grid-scale Storage Summary

As discussed in my previous post, GW of grid-scale storage are needed to work with wind and solar generation.

As EV drivers, we think batteries first, but we know how expensive batteries are. They have high efficiency, fast response, but limited lifetimes. California currently has 50K+ BEVs and 40K PEVs. If we assume that each car could supply an average of 10kWh at 10kW, 1 hour, we would have just short of 1 GW. Realistically few owners would be willing to subject their cars to 10kWh of daily cycling, but when their batteries are retired from their vehicles, we might have .6 GW of available grid storage.

Nationally, just several years ago, 99% of grid-scale storage was pumped hydro, where you pump water uphill to store energy and run it downhill to release it. You need two reservoirs close together separated by substantial altitude difference. There had been no new pumped hydro projects initiated for 20 years.

The efficiency of pumped storage is typically 80%, but new proposals claim 90+% is achievable.

The simplest way to use hydro storage like a battery is to modulate the flow of water through a dam, higher flow when demand and the price is high, lower or no flow off-peak when the price is low. The efficiency of this strategy is 100% and the only cost is the impact of variable flow on downstream uses of the water, so this has been common practice at many dams for a century or more.

Pumped hydro projects have two versions: Open Loop, and Closed Loop. Open Loop operates in contact with an existing water source, such as a reservoir and dam. To add pumped storage you provide a lower reservoir, pump, and pipe back up to the original higher reservoir. The cost is low, water is available, and the additional evaporative loss can be minimal. Closed Loop operates without an associated water source. This means two reservoirs have to be built, water purchased, and evaporative loss is now an additional concern. The addition of open water to an area that did not have it can lead to ecological concerns.

With the dramatic growth of wind generation in the midwest, and growth of solar in California and other states, FERC has this Fall 2014 map of new pumped storage projects, including almost 10 GW for California:

Image

In addition, other technologies are now being considered for new grid-scale storage.

CAES, compressed air energy storage, uses large underground caverns such as abandoned mines. It has suffered from a relatively low efficiency, because the compression usually is isothermal, not adiabatic, so heat is lost between the compression and subsequent expansion. New technology promises to reduce this loss.

Image

A 20MW flywheel project became operational in 2014 in PA. It is used for short-term, fast-response frequency regulation:

Image

In the bottom image each blue dot is the top of a flywheel unit, .1MW each. They are installed below ground level for safety in case one explodes.
LEAF Ocean Blue SL, "100 % Electric" decals, Delivered June 3, 2011
Sold June 2014 27K miles, 18% capacity loss, 1 bar, 5.0 mi/kWh.
Solar 4.6 KW DC with both string and micro-inverters.

JasonA
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Location: Sylmar, CA

Re: Grid scale projects in California and net grid demand

Wed Mar 18, 2015 7:53 am

Way back in the mid to late 90's during the "boom" I was doing alot of these types of installs. One company that was popular at the time was ActivePower which was a flywheel based UPS company owned by Caterpillar then. http://www.activepower.com/flywheel-technology/

The size of these installs were massive (especially for California and seismic zones) but to see a 3 to 10 ton flywheel running at 5k rpm totally silent in a partial vacuum chamber is pretty cool.

I'm surprised that grid and power companies haven't started to use this idea sooner.
2012 10kw Dual LQ cooled Brusa powered Leaf "Astro"
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JeremyW
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Re: Grid scale projects in California and net grid demand

Thu Apr 02, 2015 4:01 pm

I discuss the duck curve in my presentation here:
http://youtu.be/3K8bQ6krsSE?t=17m30s
Former 2012 SL leasee 6/23/12 - 9/23/15
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2000 Honda Insight for long trips

tbleakne
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Re: Grid scale projects in California and net grid demand

Tue Apr 07, 2015 12:45 pm

JeremyW, it took me several days, but I watched all of your presentation to the BayLeafs? An amazing amount of good information, and it sounds like you had a good audience patient enough to sit through the full 2+ hours. Too bad the camera was not better oriented toward the screen.

You mentioned how the demand now favors solar on SW roofs over south roofs. I have observed a growth in installations even on east and/or west roofs. Although the production efficiency is lower, with the lower cost of panels, apparently the payback is still acceptable, and the utility should like the wider production window.

Perhaps not soon, but some day when solar becomes even more widespread, it might be economic to send power west one time zone first thing in the morning and east one time zone in the late afternoon in order to cover more of the demand in these time periods.
LEAF Ocean Blue SL, "100 % Electric" decals, Delivered June 3, 2011
Sold June 2014 27K miles, 18% capacity loss, 1 bar, 5.0 mi/kWh.
Solar 4.6 KW DC with both string and micro-inverters.

Reddy
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Re: Grid scale projects in California and net grid demand

Fri Apr 10, 2015 2:29 pm

Well the actual shape of the duck curve is slightly different than the one shown in the OP. Here is the current curve from CaISO. Notice that the mid-day net demand is very close to AT OR BELOW the night-time demand. I've been watching this periodically waiting for the day. So, instead of charging our EVs at night to get the cheapest rates, soon the grid folks may change TOU and offer cheaper rates between 10am and 2pm.

http://www.caiso.com/Pages/TodaysOutlook.aspx#Renewables
Image
Reddy
2011 SL; 10 bar, 48.82 AHr; 35,000 mi; rcv'd Aug 18, 2011
Long: http://www.mynissanleaf.com/viewtopic.p ... al#p226115"
Cold: http://www.mynissanleaf.com/viewtopic.p ... 60#p243033"

tbleakne
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Joined: Wed Jul 28, 2010 12:05 pm
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Re: Grid scale projects in California and net grid demand

Fri Apr 24, 2015 2:23 pm

+1. SCE picked the March time frame to display its "Duck Curve" because that is the time of year when the difference between mid-day load and mid-day solar generation is maximum, for the most dramatic effect. Later in the summer the mid-day load will go to 45 GW or more and the solar generation will be more, but proportionally less, so the curve will be smoother.

I agree at some point they should change the incentives to encourage daytime charging. Workplace charging could be offered a discount.
LEAF Ocean Blue SL, "100 % Electric" decals, Delivered June 3, 2011
Sold June 2014 27K miles, 18% capacity loss, 1 bar, 5.0 mi/kWh.
Solar 4.6 KW DC with both string and micro-inverters.

tbleakne
Gold Member
Posts: 914
Joined: Wed Jul 28, 2010 12:05 pm
Delivery Date: 03 Jun 2011
Leaf Number: 2400
Location: Claremont, CA

Re: Grid scale projects in California and net grid demand

Tue May 26, 2015 1:56 pm

I recently saw a comment that explains better for me why many utilities in other states dislike solar. While those of us with residential solar see ourselves as helping the utility when the grid is stressed during mid-day summers, the generation component of utilities likes the on-peak time, because that is when they can get maximum wholesale price for their generation.

If solar takes a big chunk out of the net demand at the highest-priced time of the day, the economics of their fossil fuel generation declines. Of course that is exactly what should happen to reduce carbon footprint, forcing fossil fuel plants to be retired. Even in TX some of the least efficient coal generation plants are being retired, but there is very modest amount of solar in TX, so the competition is coming more from wind and natural gas.
LEAF Ocean Blue SL, "100 % Electric" decals, Delivered June 3, 2011
Sold June 2014 27K miles, 18% capacity loss, 1 bar, 5.0 mi/kWh.
Solar 4.6 KW DC with both string and micro-inverters.

smkettner
Posts: 6962
Joined: Mon Aug 09, 2010 10:13 pm
Delivery Date: 26 Feb 2014
Location: Orange County, CA

Re: Grid scale projects in California and net grid demand

Tue May 26, 2015 10:14 pm

Reddy wrote:Well the actual shape of the duck curve is slightly different than the one shown in the OP. Here is the current curve from CaISO. Notice that the mid-day net demand is very close to AT OR BELOW the night-time demand. I've been watching this periodically waiting for the day. So, instead of charging our EVs at night to get the cheapest rates, soon the grid folks may change TOU and offer cheaper rates between 10am and 2pm.

http://www.caiso.com/Pages/TodaysOutlook.aspx#Renewables
Image


YES! very different. Typical doomsday prediction. 2014 and 2015 should have had the mid-day belly lower than the overnight low. Failed to happen.
If we continue on the path to 2018 it looks like the belly could actually match the overnight low. Far from being an 'over generation issue' anytime soon.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV

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