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ScienceNostalgia101

Nuclear energy vs. renewable energy

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So you are saying that because the Government considers it beneficial for the economy, people working, and off social assistance, it is right for them to keep subsidising fossil fuels ?
Then if some other Government gets elected, that considers climate change more important than the economy, they can subsidise green energies ?

Or is it only when you personally agree with the direction the Government takes with their favoritism ?

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Solar using mirrors work okay and can include thermal storage, usually molten salt -

Solar-farm-640x421.jpg

 

But I suspect the inclusion of storage has been premature and has not been good economically for these kinds of solar plants - in the absence of a price premium for that stored power. As the proportion of wind and solar grows the value of on demand power to fill the gaps will become more apparent. That will not be a market that suits nuclear; undercut on price during the day and forced to wring the bulk of revenues out of what remains - and that is a market for fast response, on demand power, not steady baseload; nuclear will have competition, including batteries and pumped hydro and even evolving flexible industrial practices. 

Meanwhile big PV is doing daytime electricity cheaper than these kinds of plants and big batteries are getting cheaper too - about 90% drop in price for Lithium Ion in the past decade and there are extraordinary R&D efforts underway to do batteries better. Tech device makers, cordless tool makers, vehicle makers, renewable energy makers plus government agencies all want better and are spending big to do it. Recent advances in relevant sciences is coming up with the deep understandings and clever tools to make big improvements not just possible but likely - and whoever cracks the next best possible battery will get rich beyond imagination.

 

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7 hours ago, Ken Fabian said:

whoever cracks the next best possible battery will get rich beyond imagination.

Toyota recently announced plans to release cars soon using a solid state battery to replace lithium ion. These types of advances surely help. 

https://asia.nikkei.com/Business/Technology/Toyota-s-game-changing-solid-state-battery-en-route-for-2021-debut

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Both nuclear and renewable energy sources need good storage solutions.
Nuclear cannot do variable power output ( too quickly ) so it cannot ramp up for 'peak' times.
While renewables cannot supply continuous power ( intermittent, depending on Sun, wind, tides … )

While lithium or solid state may be cost effective for smaller applications, laptops, cars, etc., I don't think they'll cut it for large scale power applications, such as power to a city.
I would think more in terms of pressurised, insulated vessels of superheated steam ( which would slowly lose temperature and pressure, and literally be potentially dangerous bombs ), or pumping water to higher gravitational potential, and retrieving the stored power through Hydroelectric.

Edited by MigL

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In comparing Nuclear and renewables there was the historical question of scale (how to generate large amounts of energy in small spaces).  At the time (60's-80's) the only good options for large generating capacity were hydro, fossil fuel and nuclear.  Nuclear was a good choice because good opportunities for hydro were dwindling and, while it has its own sets of problems, nuclear replaced coal-- a benefit in several ways:  reduced acid rain, reduced greenhouse gas emissions, and reduced coal tailings (random radioactivity and other localized pollution).  I worked for several years as a technology advisor in Switzerland on construction of the Leibstadt Nuclear Power Station.  When that project was getting underway the anti-nuclear people in Switzerland argued that the country should opt for hydro.  A proposal was actually put together for a hydro plant big enough to eliminate the need for Leibstadt.  The dam would have flooded such a large amount of precious wine and dairy land in Switzerland that the country opted for nuclear.

In a sense, Nuclear gave us a bridge to the days of efficient renewables.

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I think that the strongest benefit of modern renewables (solar and wind) is that these technologies are compatible with private entrepreneurship. This drives efficiencies and lowers prices.

Likewise, the biggest weakness of nuclear (fission) is that this technology is inherently under heavy government control (among else, due to possible plutonium production). For most countries this almost guarantees sluggish development, inefficiencies and high prices.

I personally would accept to have underground nuclear power stations so that the surface remains uncluttered with wind towers and solar panels. At the moment it is not at all bad, but erecting 10 or 20 times more wind towers is a worrying thought to me.

 

1 hour ago, OldChemE said:

In a sense, Nuclear gave us a bridge to the days of efficient renewables.

Can you be more specific on the Switzerland example. Is there enough wind power? Is there enough infertile land for solar power? I ask because Switzerland is not a very large country, yet it uses about 35MWh per capita (if I found correct data). Makes me wondering if Switzerland at all has a non-nuclear option if it would want to achieve energy independence?

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4 hours ago, MigL said:

Both nuclear and renewable energy sources need good storage solutions.
Nuclear cannot do variable power output ( too quickly ) so it cannot ramp up for 'peak' times.
While renewables cannot supply continuous power ( intermittent, depending on Sun, wind, tides … )

While lithium or solid state may be cost effective for smaller applications, laptops, cars, etc., I don't think they'll cut it for large scale power applications, such as power to a city.
I would think more in terms of pressurised, insulated vessels of superheated steam ( which would slowly lose temperature and pressure, and literally be potentially dangerous bombs ), or pumping water to higher gravitational potential, and retrieving the stored power through Hydroelectric.

Question: Why do you need continuous power anyway? Wouldn't just about any warm climate need more power during the day, if only to air-condition their homes? Don't the vast majority of people live in climates warm enough that severe heat is a greater threat to life safety than severe cold?

 

Though yeah, hydroelectric is good too. Probably best to build downstream from populated settlements in case the construction workers take shortcuts on safety, though.

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1 hour ago, ScienceNostalgia101 said:

Question: Why do you need continuous power anyway? Wouldn't just about any warm climate need more power during the day, if only to air-condition their homes? Don't the vast majority of people live in climates warm enough that severe heat is a greater threat to life safety than severe cold?

Because some devices are on, 24 hours a day. Not necessarily individual devices, but in aggregate, something is on, even at night. e.g. refrigerators. Wall clocks. Certain lights. Computers.

Demand varies over the course of a day, but it doesn’t drop to zero at night. Continuous is not the same as constant.

 

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1 hour ago, ScienceNostalgia101 said:

Question: Why do you need continuous power anyway? Wouldn't just about any warm climate need more power during the day, if only to air-condition their homes? Don't the vast majority of people live in climates warm enough that severe heat is a greater threat to life safety than severe cold?

https://earthobservatory.nasa.gov/biome/biodesert.php

"During the day, desert temperatures rise to an average of 38°C (a little over 100°F). At night, desert temperatures fall to an average of -3.9°C (about 25°F)."

 

Edited by Sensei

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4 hours ago, MigL said:

While lithium or solid state may be cost effective for smaller applications, laptops, cars, etc., I don't think they'll cut it for large scale power applications, such as power to a city.

Even 5 years ago I might have agreed but battery R&D has become a truly massive deal; the players in that game are serious and are seriously well funded. It may not be wise to put all hope in them succeeding spectacularly but assuming they must fail, with perhaps a decade before growth of solar and wind starts forcing the issue, seems especially pessimistic.

100% is overly optimistic  - and most larger grids are unlikely to ever be 100% any one thing - but nothing in this arena is staying the same long enough to base future projections on past performance. Batteries in the pipeline in Australia are reaching towards totals of GW of power and GWh of storage, already more than 10 times the electricity market operator's predictions made just 4 years ago - and causing plans for new gas plants to be deferred or shelved. It has been suggested that South Australia - admittedly especially good solar and wind - already has about 1/10th of the storage capacity to run at 100% RE. Some pumped hydro is coming along too.

I think if we can do cars with batteries then cities stop looking so difficult - each car will have more battery storage than most homes and many small businesses need to run overnight from rooftop solar. Perhaps better so for warmer, sunny climates than Canada's Winters, which may need other solutions in addition. It will be to the advantage of low emissions committed grid operators to have lots of EV's plugged in when not in use rather than fast charged and disconnected. This will be both to vary charging rates to smooth supply (and demand) variability and (under mutually agreed terms with day to day consumer choice) get access to a portion of that stored energy. Every office and street car parking space with an EV charge connection will be worth something to power companies, something more valuable than mere convenience to customers.

 

 

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I didn't mean to sound like I thought demand went to exactly zero at night, but rather that it should've dropped enough that the aforementioned wind, solar, and hydroelectric could've met it. I could be wrong, of course; my background's physics, not engineering.

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Here is the way I envision it working.

The nuclear power plant is sized to provide a median output, between the low draw periods ( like at night ), and the peak draw periods ( during the day ). The excess power generated during the low draw periods is used to charge a battery, heat steam, or pump water to a higher reservoir. When power isn't enough to supply the peak draw, it is topped-up from the battery, steam driven turbines, or water driven hydroelectric from the elevated reservoir ( dam ? )
The same can be done with renewables, but instead of high and low power draws, you have to consider high and low power generation.
You generate more when wind/sun/tides are favorable, store the excess, and draw from it when conditions are unfavorable.

As I said, I can see batteries for small scale applications, but to power a city they might not be feasible.

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4 minutes ago, MigL said:

I said, I can see batteries for small scale applications, but to power a city they might not be feasible.

The Musk team at Tesla designed a high capacity storage option called PowerWall for individual homes. The thinking was that significant decentralized energy storage at each house is more achievable and effective than one massive centralized bank of charged batteries trying to cover entire cities or towns. 

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I can see that replacing emergency generators, INow.
Electricity is already expensive enough for people on fixed incomes; the financial burden of buying a battery ( and replacing it every so often ) might be better tackled by the 'sharing' of expenses by a community; a large scale community battery ( or means of power storage ), instead of distributed, home batteries.
I know that sounds like Socialism, so you might not like it ( haha :D:lol: tables are turned ), but that is a way to even the load ( financial, not electrical ) between those who can afford a home battery, and those who can't, and may have to go without power.

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Lol. Expenses can be shared through subsidies and tax rebates even if the power storage itself isn’t centralized. 

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On 12/24/2020 at 11:59 AM, Danijel Gorupec said:

Can you be more specific on the Switzerland example. Is there enough wind power? Is there enough infertile land for solar power? I ask because Switzerland is not a very large country, yet it uses about 35MWh per capita (if I found correct data). Makes me wondering if Switzerland at all has a non-nuclear option if it would want to achieve energy independence?

Sorry I'm slow replying (away for awhile).  Fundamentally, Switzerland went with the nuclear option because they had not significant sources of fossil fuels in the country-- they were importing what they needed.  Nuclear gave them a degree of energy independence.  That, however, was almost 20 years ago, and I have not kept track of how things may have changed since I left the country to return to the United States.

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On 12/24/2020 at 12:14 PM, MigL said:

Nuclear cannot do variable power output ( too quickly ) so it cannot ramp up for 'peak' times.

How, then, does a nuclear powered aircraft carrier go from all stop to full speed ahead in a short period of time?

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24 minutes ago, npts2020 said:

How, then, does a nuclear powered aircraft carrier go from all stop to full speed ahead in a short period of time?

Oh, I don't know, maybe by just not delivering the reactor output to the propeller?

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2 minutes ago, Janus said:

Oh, I don't know, maybe by just not delivering the reactor output to the propeller?

Where does the power to turn the propeller for full speed ahead come from, then? The point is, the reactor I worked at aboard a carrier never seemed to have much problem with pretty wide power transitions in short periods of time.

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9 hours ago, Janus said:

Oh, I don't know, maybe by just not delivering the reactor output to the propeller?

Not a lot you can do with it, other than delivering it to loads. But in doing so you have to heat up water, which acts as a buffer for variations in demand. If you increase power demand, the first thing that happens is the temperature of the water drops. The reactor fission rate increases as a result, but there’s a lag in the output (it takes time for water to complete a loop through the system)

Naval reactors have some design differences compared with commercial ones. Commercial reactors are designed to run at near peak power, without much variation. The much smaller one on a sub is designed to respond the changes in load. (Carrier plants are bigger, so the size-related design constraints are lessened)

7 hours ago, Sensei said:

A nuclear reactor is typically used to produce electricity. Electricity drives the motors that move the carrier.

https://en.wikipedia.org/wiki/A1B_reactor

https://en.wikipedia.org/wiki/Nuclear_marine_propulsion

 

In some ships/boats. Not “typically” as such.

“The Russian, US and British navies rely on direct steam turbine propulsion, while French and Chinese ships use the turbine to generate electricity for propulsion”

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13 hours ago, npts2020 said:

How, then, does a nuclear powered aircraft carrier go from all stop to full speed ahead in a short period of time?

 

swansont said much of what I was going to say, but I think the question was a good one and deserves encouragement so +1.

 

Firstly no nuclear reaction produces or generates electricity.

So by themselves nuclear reactors (ie plant and equipment where controlled nuclear reactions take place) need further plant and machinery to generate the electricity.

Nuclear reactions generate heat (and fission products of course)  - lots of it.  So much of it that much is wasted.

However this released heat is used to heat coolants by a series of heat exchangers to drive turbines that drive the generators.

But the reactor is designed to run 'up slowly'. In theory it may be run down very quickly for emergency purposes by moderators.

The issue then becomes how to use the spare heat to meet a sudden increase in demand.

One way is to have standby generators that can be brought online very quickly.
These would be needed in any case for maintenance purposes.

Another way would be to divert more steam to driving turbines, but that would mean they were working at less than full capacity before.

Another way would be electricity or heat storage, neither being very practical in marine environments, though a buffer of either could help overcome a short term increase in demand.
Electricity storage would be better for this.

In any event the whole power plant comprises more than just the nuclear reactor.

 

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3 hours ago, studiot said:

Another way would be to divert more steam to driving turbines, but that would mean they were working at less than full capacity before.

That’s one practical way of having the capacity in place. You’d basically be running the system at lower efficiency by bypassing the turbines and condensing steam without extracting work from it. 

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We do have people who have served on nuclear subs.
At least Swansont claims to have one so.
( personally, I think he just watches 'The Hunt For Red October' over, and over; he's got a crush on Sean Connery :) )

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Ydoaps too

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