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THE Solar Cell Thread Pt. 4 (merged)

Discussions of conventional and alternative energy production technologies.

Re: What are the limitations of solar energy?

Unread postby Subjectivist » Fri 28 Apr 2017, 21:45:27

← Benefiting from Green Jobs
Is the Duck Sinking?
Posted on April 24, 2017 by Catherine Wolfram
This has been a spring of leaks. Most of you probably heard about the hole at the Oroville Dam. In my house, we’ve had leaks in both our skylight and our car. Yes, it’s great to be out of the drought, but like other Californians, we’re feeling a bit waterlogged.



All this water means that the hydro dams are cranking out lots of electricity. Reservoirs are at high levels, even before the major snow melt, so we’re letting a lot of the water run through the dams and producing cheap hydropower morning, noon and night.

If you believe the saying, ducks take to water well. But in the electricity world, the bountiful water is creating problems for the industry’s favorite waterfowl.

Long-time blog readers have heard several mentions of the “duck curve” – the aptly named graph that depicts energy demand net of wind and solar generation over the course of a day. I’ve reproduced one of the original versions below, which was created circa 2013 and shows projections out to 2020. Much of the focus has been on the duck’s neck – the rapid increase in non-renewable electricity demand as the sun sets on solar plants and people turn on lights.





As of last spring, the projections in the duck curve were materializing on schedule, as Meredith’s blog post described. During 2016, however, utility-scale solar PV capacity in the state grew by another 50%. As a result, net load in the middle of the day on a recent Sunday (April 9) bottomed out at 10,000 MW (see the green line in the graph below), instead of the 14,000 MW projected for 2017 in the forecast duck (the dark orange line labeled “2017” in the graph above).



Source: Daily Renewables Watch, CAISO (Thanks to the ISO for this and other great data sources.)

All the solar and hydropower have led to a new phenomenon – negative prices in the middle of the day. The blue line in the graph below depicts day-ahead prices for Sunday, April 9 in Southern California. For comparison purposes, the red line depicts day-ahead prices at the same location on the second Sunday in April 2012. Looks like another version of the duck, albeit drawn by a preschooler, and this time with price on the vertical axis.



Source: California ISO OASIS

Note that I picked April 9 as an example. Through yesterday, there were 19 days during March and April 2017 with negative midday prices in the day-ahead market in the South. They’re certainly more common on weekends, when people take breaks but the sun doesn’t. But, 7 of those 19 days were weekdays. Also, I’m focusing on the South, as that’s where most of the grid-scale solar is located. For the three days I checked, though, prices were also negative in the North.

Let’s first wrap our heads around what it means to have a negative price. On these days, if you were in southern California, the ISO was willing to pay you to consume electricity. Nearly all retail customers are on fixed tariffs that do not vary with wholesale prices, so they were still paying positive prices for electricity. But, if you were exposed to wholesale prices, you would have made more money the more electricity you consumed – just plug in your least efficient electric space heater and watch the dollars role in.

You may wonder why an electricity generator would be selling into the market when prices are negative. If you’re the owner of a large solar plant in the desert, for example, can’t you just turn off your connection to the grid, instead of having to pay to feed electricity into the market? Similarly, why would a gas or nuclear plant use costly fuel to sell into a market with negative prices?

There are a couple reasons generators might be willing to sell at negative prices:

The production tax credit. Some renewables owners (mainly wind) are eligible for a production tax credit, which essentially pays them, in the form of a tax credit, for every MWh they produce. So, not producing means that they have to forego this credit. In theory, producers will pay to sell into the wholesale market as long as they’re paying less than the tax credit.
The Renewable Portfolio Standard. Under California’s Renewable Portfolio Standard (RPS), utilities are on the hook to provide 33% of their electricity from renewable sources by 2020 and 50% by 2030. The utilities sign contacts with renewable providers and, while terms likely vary, the utilities want to meet their RPS targets. In the extreme, the utilities are on the hook to pay a penalty (which was $50/MWh early on) if they don’t. So, they generally want to encourage the renewable providers to produce. For example, under a very simple power purchase agreement, the utility would pay the renewable provider a pre-specified price per MWh irrespective of the wholesale market price, leaving them no incentive to shut down when prices are negative.
Operating constraints. For some power plants, varying the output level entails high costs, particularly starting and stopping the plant. I think of those as analogous to the extra fuel, plus wear and tear, planes expend taking off. So, if it costs a lot to restart a nuclear plant, for example, you’re willing to pay not to have to turn it off to avoid incurring those costs.
In the graph below, we can see that the state’s lone nuclear plant, and even some thermal (which is essentially analogous to fossil-fuel) plants were still operating on April 9 when the prices were negative.

Source: Daily Renewables Watch, CAISO

The cost of turning plants on is also reflected in the real-time prices from April 9. Just like the day-ahead prices, they were negative in the middle of the day. But, they really spiked during the morning and evening ramps (to $1000/MWh!) when plants needed to turn on to meet the additional demand.

What do the negative prices tell us? At a fundamental level, they tell us that we have too much of a good and suppliers need to pay people to take it off their hands. Right now, California has too much renewable electricity. Emphasizing this point, a recent briefing from the California Independent System Operator noted that renewable “curtailments” were at record levels in March 2017, amounting to over 80 GWh, which is more than a typical day’s worth of solar production that month.

Is there anything to do about the negative prices? Negative prices certainly highlight the value of storage, where the basic idea is to buy low and sell high. Buying when prices are negative is especially lucrative. Standalone storage is still expensive, but the costs are rapidly declining. Increased electrification of transportation may provide one type of storage or at least flexible demand.

Another solution is to expose more retail consumers to wholesale prices, or find other ways to encourage customers to respond to real-time prices. Economists have bemoaned the disconnect between wholesale and retail pricing for years—maybe the prospect of being paid to consume electricity will help more people see the value of this?!?

In addition, generators that historically operated through the belly of the duck, including nuclear, combined heating and power, and conventional natural gas plants might be encouraged to reduce their output. For example, while it may not be practical to cycle nuclear generation on a day-to-day basis, maybe refueling outages could be scheduled for the spring, when excess supply problems are generally the worst.

Proponents of western grid integration note that removing barriers to exporting electricity will help California share some of its renewable electricity, especially when in-state demand is low and hydro supplies are high. (This is not intended as a comprehensive list of the solutions – an ISO discussion includes more here.)

To round out the post with another duck-ism, the duck may look calm, but we need to pay attention to what’s going on below the water line – the zero price line in this case. The duck is paddling furiously, as operating an electricity system with a lot of renewables isn’t easy.


https://energyathaas.wordpress.com/2017 ... ment-15141
II Chronicles 7:14 if my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then I will hear from heaven, and I will forgive their sin and will heal their land.
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Re: What are the limitations of solar energy?

Unread postby ROCKMAN » Sat 29 Apr 2017, 09:26:29

baha - Interesting...thanks. Seems like the question should be split: commercial scale vs individual such as yourself. Rather different dynamics/economics between the two.
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Re: What are the limitations of solar energy?

Unread postby ROCKMAN » Sat 29 Apr 2017, 12:15:30

baha - Yep, small business installation may be just the right spot for major solar expansion. But with lower costs citywide solar is starting to take off in Texas because we still have abundant fossil fuel sources to back it up and thus aren't being delayed waiting on grid scaled batteries. But when Elon et al can finally deliver on the long promised AFFORDABLE grid scale batteries Texas could start moving towards large scale green faster then the other states since we will already have a fairly massive amount of wind and solar in place.

Who would have guessed just 10 years ago: the state producing more oil/NG then any other may be "more green" then any other state? Except possibly CA, of course.
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Re: What are the limitations of solar energy?

Unread postby Zarquon » Sun 30 Apr 2017, 01:21:48

Every time solar power is discusses, it's always about panels on roofs, as if that were the answer to our potential energy dilemma. People tend to forget that households consume perhaps just 1/3 of all electricity.
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Re: What are the limitations of solar energy?

Unread postby Tanada » Sun 30 Apr 2017, 07:46:37

baha wrote:PV scales well at this point. It depends on your demand. We are installing a 1.32 Mwatt installation for a not-so-small business. They will offset a significant portion of their demand. But unless Duke Power designs well it can cause fluctuations on the grid.

Batteries are not quite there yet in large scale, although Elon would disagree. When they can be put in a closet out back with the inverter it's going to be a done deal. Save the FF for the real energy hogs like smelting metals and making concrete.

Someone should analyze the economics of concrete...is it more efficient to use a little on each post of a ground mount PV system or a whole $hitload on a nuclear power plant?


Such comparisons are very difficult to make for two reasons, the size of the wind turbine and the size of the nuke plant are key variables. This allows pro wind folks to use the highest nuke numbers and lowest wind numbers to make themselves look good and vice-versa. Modern Gen IV nuke designs use half down to a quarter as much concrete as the old Gen I and Gen II designs that make up 99 percent of American nuke plants because we stopped building new ones right as Gen III was arriving on the market. Overseas designs have continued to progress and 20 or more Gen III design plants have been built, but that series adopted the 'make it as big as possible' philosophy to reduce labor costs by concentrating as much capacity as possible in each unit. Many if not all Gen IV designs follow the modular philosophy with capacities about a quarter or perhaps less of the biggest Gen III designs and use additional automation to make up for the labor cost difference.

Right now China has a very robust nuclear development and design process going on and they are building half a dozen Gen III reactors to get experience in building and using nukes. They currently have a new unit in start up and its twin is planned to start up six months later in first quarter 2018. China has a lot of very smart engineers, they understand that intermittent sources are great for 20 or maybe 25 percent of the grid, but not for baseload power 24/7/365. That leaves humanity with two choices if we want a high energy lifestyle, we can use fossil fuels for baseload, or we can use nukes.
Alfred Tennyson wrote:We are not now that strength which in old days
Moved earth and heaven, that which we are, we are;
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.
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Re: What are the limitations of solar energy?

Unread postby eugene » Sun 30 Apr 2017, 09:02:19

It's OK to be drowning and dreaming of salvation. Called faith based.
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Re: What are the limitations of solar energy?

Unread postby Tanada » Sun 30 Apr 2017, 14:13:41

baha wrote:You know, one cooling pond at Fukushima full of spent rods would probably heat a city. Why is it considered waste? Because we live in an energy extravaganza!! We need to re-think the way we do things.

WOW- I just looked it up..the half-life of Uranium 235 is 700 million years. U238 is 4.47 billion!!! Our problems were solved 50 years ago but were again restricted by TPTB. This doesn't give me a warm fuzzy about solar power.

WTF?


Heat output is inversely correlated with half-life, the shorter the half-life the higher the heat output. The reason spent nuclear fuel is hot is it holds a lot of short half-life materials, i.e. material with a half-life of 60 years or less. As each set of half lives expires the heat output drops. By the time the spent fuel has been in a pool for 3 years the heat output is low enough it can be safely moved to dry cask storage where it will cool in air without any danger of melting. For the USA most fuel in dry cask storage is 10-30 years old and very little is moved at less than 5 years because their is plenty of pool storage to hold all the fuel that is 5 years post use and less.

If you take spent fuel and separate out all that short half life material you can make a handy dandy thermoelectric generator, the kind NASA and other agencies use for deep space missions too far from the sun for practical solar PV. Because so many of the fission products last less than six months before decaying away the heat output drops like a rock in that first 5 years. The rule of thumb is after 10 half-life periods any isotope has effectively decayed to zero. The spent fuel rods go from orange hot when first pulled out, to red hot, to just hot in that 60 months/5 years right after they are pulled out of the reactor. To make water boil efficiently they have to be white hot while operating the reactor, but that temperature mostly comes from active fission and as soon as you stop the fission you start rapidly dropping the temperature.
Alfred Tennyson wrote:We are not now that strength which in old days
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Re: What are the limitations of solar energy?

Unread postby ROCKMAN » Mon 01 May 2017, 11:00:17

Z - And it looks like we're on the verge of proving the commerciallity of grid scale battery storage in Texas not only for wind but also solar. As you pointed out rooftop residential solar has a limited impact compared with commercial electricity consumption. If the intermittency problem with solar is in the process of being eliminated and solar continues to get cheaper we have the room to build hundreds of commercial scale solar fields on the hundreds of thousands of sun drenched and rather cheap scrub lands in south Texas. And with our $7 billion grid upgrade won't have a problem distributing power to commercial consumers across the state. Commercial consumers that useat least twice as much electricity as those in most states:

E.ON to build nearly 20 MW of battery storage at Texas wind farms

E.ON North America is installing two battery storage projects, totaling nearly 20 MW, at two of its wind farms in west Texas. The two Texas Waves energy storage projects, 9.9 MW each, will be sited at E.ON’s Pyron and Inadale wind farms. The lithium-ion battery arrays are slated to come online by the end of 2017.

Texas leads the nation in wind power, and it is now becoming a testing ground for energy storage ever since a Brattle Group report came out in 2014 that found up to 5 GW could be deployed on the state's grid. But deploying storage in Texas is difficult because the electricity market rules prevent using all the functions of a battery storage resource. However, that doesn't seem to deter some utilities. E.ON is adding two 9.9-MW storage facilities to its 249-MW Pyron wind farm in Hermliegh and its 197-MW Inadale wind farm near Roscoe. Both wind farms went online in 2009.

The Texas Waves projects are designed to provide ancillary services to the ERCOT market and to increase system reliability and efficiency by quickly responding to shifts in power demand.

{And others making advances: from a year ago} -

"North Carolina-based Duke Energy is converting a 36-megawatt battery system at its wind farm in West Texas from outdated lead-acid batteries to the more efficient lithium-ion variety, favored for electric vehicles.

Likewise, Virginia-based AES Corp. is teaming up with Texas transmission company Oncor to construct a 20-megawatt, lithium-ion battery project in Dallas to help maintain a steady flow of electricity as demand rises and falls. One megawatt can power about 200 typical Houston resi-dences during peak demand.

Battery storage is often called the "Holy Grail" for turning power grids green, because it could provide power during stretches when the wind isn't blowing or the sun isn't shining. "Storage is close in five years to being a potential game changer, but nobody (in Texas) was talking about it," said Don Clevenger, Oncor senior vice president for planning. "Storage really does address a lot of problems with one device. There's a real panacea of benefits."
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Re: What are the limitations of solar energy?

Unread postby ROCKMAN » Mon 01 May 2017, 12:41:27

baha - "No one else is allowed." And maybe that is the most important edge Texas has: a "deregulated" electricity system. IOW anyone can build an electricity generating infrastructure anywhere that makes economic sense and sell power to any consumer on the grid: every one has access. And having ERCOT structured as a "cooperative" of independent investors, public utility companies, transmission companies, local distribution companies and the state regulators makes for a somewhat seamless process.

Like the old line: If momma ain't happy then nobody is happy. And all the players have to keep ERCOT happy: piss it off and you can't stay in the Texas electricity playground. IOW ERCOT could tell your local Duke butt heads to go f*ck themselves. LOL.
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Re: What are the limitations of solar energy?

Unread postby ROCKMAN » Mon 01 May 2017, 17:34:21

"What are the limitations of solar energy? You can't drive it around." That's true. But you can run a lot of f*cking industry with alt energy. Such as the commercial electricity users in Texas that consume more electricity then the commercial AND residential consumers COMBINED in 47 other states. Also contributes to Texas having lower rates then 40 other states.
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