Why not use the kinetic energy of the tides for energy

[Mark R]

Originally posted by: inspire
I've never heard of pumped water storage - do you mind explaining it or giving a link?

Text

 

[Peter]

Global warming isn't much debated anymore. Historical temperature graphs from scientists all over the world pretty much match - and they all show a steep incline in temperature, starting in the past century, that has been unseen in Earth's history throughout - or at least as far back as drill cores and other findings let us look.

 

[BrownTown]

Originally posted by: Peter
Global warming isn't much debated anymore. Historical temperature graphs from scientists all over the world pretty much match - and they all show a steep incline in temperature, starting in the past century, that has been unseen in Earth's history throughout - or at least as far back as drill cores and other findings let us look.

Just becasue temperatures are rising lately doesnt mean that man is casuign it, or that man could do anything meaningfull to combat it.

Anyways, abotu pumped water storage, its a very simple idea. You build a big resovoir at a high elevation above a lake or river. IF you are producing more pwoe than you need that minute you use the excess power to pump water up to the upper resovoir. Then when you really need power later on you let the power run back down through generators. So, in the case of wind power, if the wind is going all out on some day when the pwoer demands are low you use that excess energy to pump the water. Then if the next day there isnt any wind you use the generators at the pumped water plant to produce the power. Modern implimintation are something like 75% efficient, but if you look at power prices they can vary 10x between the middle of the night and the midday peak, so its very economical to use them in a current system. It also provides a way to store power from widely variable systems like solar or wind, and provides a good amount of stability to the grid, since you can rapidly recover from the loss of another generating station. Also, its really the only way to store such large amounts of pwoer, and since you are using potential energy of water instead of energy stored in dangerous chemicals liek hydrogen or alkaline batteries its safer. Problem currently is the same as every other technology in the energy industryt which is that enviromentalists dont like it. Building man made lakes on top of mountains apparently pisses them off. OF coruse so does everything else do personally i don't care.

Heres some nice links about raccoon mountain which is a few miles from where i live.
http://www.tva.gov/sites/raccoonmt.htm
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

Cost about a billion dollars, 1600MW capacity, they pump it up each night and run it out each day.

 

[KF]

Originally posted by: BrownTown
Then if the next day there isnt any wind you use the generators at the pumped water plant to produce the power. Modern implimintation are something like 75% efficient, but if you look at power prices they can vary 10x between the middle of the night and the midday peak, so its very economical to use them in a current system.

I heard of this interesting method many long years ago, as being the only way to store truely immense quantities of power as might be used by a city, but the way I heard it, it was supposed to be too wasteful to actually result in any cost saving. Without any numbers, it is hard to judge. 70 to 85% recovery of the input electricity seems very good, if that is what the numbers really mean.

I've often wondered about, and been unable to find, any solid numbers on efficiencies of various things.

How much of the power do you get back from a storage battery, like an automobile battery? How efficient are those $5000 batteries they use in hybid automobiles? 5%?

How much of the chemical energy in gasoline winds up in kinetic energy at the drive shaft? I know they say "it depends", but that is not an answer. 10%?

I once heard that the steam turbines in electric power plants were among the most efficient engines in existence that use heat as the input, and approach 80%. More recently, I read that the efficiency does not come close to 50% So what is it really? I would think that the people that engineer these things have a very good idea.

They used to suggest hydrolysis of water as the source of hydrogen in a system that use hydrogen fuel to avoid the CO2 generation. Then I heard that hydrolysis was terribly inefficient. So what is the efficiency? (The electricity for hydrolysis would come from atomic power plants if you are wondering.)

Well designed electric motors, they say, easily reach 90% efficiency, and transformers are higher than that. Is this true, or are they using unrealistic ideal conditions?

How much of the electrical energy used by an ordinary light bulb winds up in visible light? 1%?

How much of the energy in sunlight that falls upon a plant winds up as chemical energy in sugar? 0.1%?

Can it possibly be true that ethanol produced from a crop such as corn could produce more energy than was used to produce the crop (not counting the sunlight)?

This idea of using kinetic energy in nature, such as tides, winds or water flowing downhill, which we get "for free", before it ultimatedly randomizes into heat and becomes useless for anything else, brings to mind a beautiful idea that was told to me by some one that normally had tons of crackpot ideas (like how magnets could make a perpetual motion machine) and seems too good to be true. Whenever we use energy to produce heat we waste part of its usefulness. It is one of those unavoidable facts of nature that no matter how we use energy, it winds up as heat anyway. But we could do something useful in between, and still get the heat. So instead of burning natural gas in a furnace, we could use it to run an engine, and that engine could generate electricity, for our own use perhaps, or sell it back to the electric company, or it could be the motive force for the compressor in the refrigerator, or turn the blower in the furnace. We could get that "for free", and still get the heat at the end. True, we would lose some heat in the exhaust that would have to be vented outside, but otherwise this does work.

 

[Peter]

It's been done ... here in Augsburg we have a handful of small power plants (gas burners) spread across the city, producing electrical power, and at the same time feeding heat to the surrounding households through pipes.

The soviets have been doing that on a much bigger scale, as some may recall from a recent, particularly cold winter, when it was reported that the system had failed and Moscow was freezing inside and out.

 

[racolvin]

Originally posted by: Peter
You'll eventually find (like Europe currently does) that the aftermath cost of nuclear power is HUGE. Sure, the US and Russia have many more remote deserts to carelessly dump the radioactive wastes into, but just looking at the obvious running cost is blatant disregard of the grand total.

Isn't there a nuclear reactor technology that dramatically reduces the amount of final waste that's produced? I think its called a "breeder" reactor that continutally consumes its own waste product to generate power. It was developed after the standard cold water reactor technology but too late to be incorporated into many of the existing nuclear plants.

Anyone more knowledgeable about that?

 

[bobsmith1492]

I think most (or a lot of) reactors in the US ARE breeder reactors (they take in uranium and put out plutonium, among other things), and other reactors simply run on plutonium leftovers.

 

[bobsmith1492]

Originally posted by: KF

Originally posted by: BrownTown
Then if the next day there isnt any wind you use the generators at the pumped water plant to produce the power. Modern implimintation are something like 75% efficient, but if you look at power prices they can vary 10x between the middle of the night and the midday peak, so its very economical to use them in a current system.

I heard of this interesting method many long years ago, as being the only way to store truely immense quantities of power as might be used by a city, but the way I heard it, it was supposed to be too wasteful to actually result in any cost saving. Without any numbers, it is hard to judge. 70 to 85% recovery of the input electricity seems very good, if that is what the numbers really mean.

I've often wondered about, and been unable to find, any solid numbers on efficiencies of various things.

How much of the power do you get back from a storage battery, like an automobile battery? How efficient are those $5000 batteries they use in hybid automobiles? 5%?

How much of the chemical energy in gasoline winds up in kinetic energy at the drive shaft? I know they say "it depends", but that is not an answer. 10%?

I once heard that the steam turbines in electric power plants were among the most efficient engines in existence that use heat as the input, and approach 80%. More recently, I read that the efficiency does not come close to 50% So what is it really? I would think that the people that engineer these things have a very good idea.

They used to suggest hydrolysis of water as the source of hydrogen in a system that use hydrogen fuel to avoid the CO2 generation. Then I heard that hydrolysis was terribly inefficient. So what is the efficiency? (The electricity for hydrolysis would come from atomic power plants if you are wondering.)

Well designed electric motors, they say, easily reach 90% efficiency, and transformers are higher than that. Is this true, or are they using unrealistic ideal conditions?

How much of the electrical energy used by an ordinary light bulb winds up in visible light? 1%?

How much of the energy in sunlight that falls upon a plant winds up as chemical energy in sugar? 0.1%?

Can it possibly be true that ethanol produced from a crop such as corn could produce more energy than was used to produce the crop (not counting the sunlight)?

This idea of using kinetic energy in nature, such as tides, winds or water flowing downhill, which we get "for free", before it ultimatedly randomizes into heat and becomes useless for anything else, brings to mind a beautiful idea that was told to me by some one that normally had tons of crackpot ideas (like how magnets could make a perpetual motion machine) and seems too good to be true. Whenever we use energy to produce heat we waste part of its usefulness. It is one of those unavoidable facts of nature that no matter how we use energy, it winds up as heat anyway. But we could do something useful in between, and still get the heat. So instead of burning natural gas in a furnace, we could use it to run an engine, and that engine could generate electricity, for our own use perhaps, or sell it back to the electric company, or it could be the motive force for the compressor in the refrigerator, or turn the blower in the furnace. We could get that "for free", and still get the heat at the end. True, we would lose some heat in the exhaust that would have to be vented outside, but otherwise this does work.

Steam turbine systems are about as efficient as it gets energy-wise; a large-scale system, such as a power plant, will use many stages of turbines to eek out as much power as possible from the input heat. However, due to simple basics of thermodynamics, it is impossible to achieve 100% efficiency; the actual efficiency is based on the Carnot cycle, which is itself extremely unpractical, but it provides the theoretical maximum thermal efficiency (converting heat to mechanical energy). Look it up!

For 100% thermal efficiency in a system, you have to absorb heat from a source that is at the same temperature as the thermal mass into which you discharge heat, which is obviously impossible.

 

[bobsmith1492]

Oh, one more thing: pumped-water storage plants are extremely practical. There's one nearby here, in Ludington, MI, that I've visited. It's just a huge bowl that they store water in. Power prices can fluctuate greatly from morning/midday peaks to midnight lows. Pumped-storage can help alleviate problems like the rolling blackouts and whatnot that occur during summer because of the high air-conditioning loads on the power grid since they effectively load-balance between high-demand and low-demand periods. They also can kick in extremely fast (just a matter of letting the water out).

Also, they can generate some power from any rain they collect (not much, but hey, it's something!).

 

[BrownTown]

Originally posted by: bobsmith1492
I think most (or a lot of) reactors in the US ARE breeder reactors (they take in uranium and put out plutonium, among other things), and other reactors simply run on plutonium leftovers.

There is not a single breeder reactor in the US. All nuclear reactors do produce a small amount of plutonium when they opperate, but breeder reactos are designed to produce more plutonium then they consume enriched uranium so that after an inital load of enriched uranium you can use natural uranium as fuel instead of enriched uranium. All reactors in the US are light water reactors that use enriched uranium as fuel.

 

[bobsmith1492]

Really.... whoops. Sorry 'bout that.

 

[BrownTown]

yeah, but evenutally breeder reactors will be needed since the current reactors wast 99% of the fuel. Fortunately this radioactive "waste" can be reused in breeder reactors. ITs kinda funny that everyone is trying to get rid of their nuclear waste, but with a different reactor it suddenly turns into valuable fuel. I'm sure like everything else in the world this will come around when it becomes economically feasible, when Uranium prices start going way up people might decide that it makes mroe sense to use all the Uranium and not jsut the very rare U235 isotope.

 

[bobsmith1492]

I suppose the first problem is to get the opportunity to actually build any new reactors; maybe after fifty years people will realize they're not really going to spontaneously explode and destroy an entire state?

 

[BrownTown]

Well, right now there are several big hurdles. First of all you have the fact that Yucca mountain still isnt there, and nobody really knows when it will be, so companies with nuclear reactors will have to store the waste on site which is not what they want to do. There is also the really bad PR nuclear energy gets, you can be assured if you try to build a new plant that you will be sued by tons of enviromental groups, and they will be hounding you day and night to try to find reasons to get the plant from being built. Third, there is the big issue of money, the last big nuclear construction period ended with many nuclear plants going WAY WAY overbudget, and many being canceled, so nobody really trusts the estimates about what a new nuclear unit will cost. And fourth there is the fact that if there IS another nuclear disaster, which like everything in life is really onyl a matter of time, that public opinion might force the governmetn to shut down alot of nuclear reactors and casue companies to have essentially wasted billions of dollars on plants that will never operate.

What needs to happen is for some enterprising utilities to decide that they will be the first to build a new nuclear plant, and then once people see that it can be done safely and on budget others will follow. There are already several groups looking into this, but its one thing to support nuclear power, and another thing to pony up the 3 Billion to build a new plant.

 

[racolvin]

That's sort of what I was looking for. I thought it was the Breeder Reactor that could use its own waste as even more fuel, in an almost perpetual cycle. I think the idea with the breeder was to end up producing like 1% of unusable material, meaning a massive reduction in waste storage/disposal issues.

 

[electrosoccertux]

Lots of engineering feats to be conquered before this will be viable. Far too much corrosion to make these feasible. We still have to build the parts out of materials manufactured using some amount of oil.

Pebble bed nuclear reactors are the way to go.

 

[Peter]

Germany had built a breeder reactor, but due to protests and the chernobyl disaster it never went online. We're shutting down ALL nuclear plants over the course of the next two decades - and we won't miss them. Power consumption figures are solidly heading downward, while energy generation from renewable sources is on the rise.

France and Japan had to take theirs offline after accidents, Russia keeps operating the one they have and plan another. The USA are on their sixth experimental one.

The technical problems and environmental risks are substantial: Plutonium is not only radioactive, but also incredibly poisonous. Breeders are natrium cooled, which acts highly corrosive to the innards of the reactor. Combined with the high pressure of the cooling agent due to the high core temperatures, leakages have proven to be the one big problem in breeders.

Incidentally, the German wiki article has a lot more substance to it than the English language one - including a table of all breeder plants that have been built.
http://en.wikipedia.org/wiki/Breeder_reactor
http://de.wikipedia.org/wiki/Schneller_Br%C3%BCter

 

[Mark R]

The idea of a breeder reactor is to end up with more fuel than you started with. Eg. you put 1 tonne of Plutonium into the reactor as fuel, run the reactor for 2 years, then unload the fuel and refine it again. You now have 1.1 tonne of plutonium.

There was a push for breeder reactors because it was thought that there would be a major shortage of Uranium - whereas breeder reactors would provide an exponentially increasing source of fuel.

Most breeder reactors have been frought with problems - but one of the oldest, France's Phenix reactor, is still in regular use and producing electricity for the French power grid. The performace of the Phenix reactor over its lifetime has been a 16% gain - i.e. for every tonne of plutonium that went in, it produced a net gain of 160 kilos.

There have been a number of issues which have limited the popularity of breeder reactors:
1) They are very expensive to build - several times the price of a more conventional PWR.
2) Extracting the plutonium from irradiated fuel is hugely expensive - and at today's rock-bottom uranium prices is not economically sensible
3) Plutonium extracted from breeder reactor irradiated fuel is suitable for weapons usage, whereas plutonium extracted from PWR irradiated fuel is (in general) not weapons suitable.
3b) For this reason, several countries including the USA, have banned research, development and operation of breeder reactors
4) Reliability at breeder reactors has not been good. In particular, in Japan, there was a major sodium fire at the plant (a piece of equipment removed from the reactor didn't have the sodium cleaned off before it was taken out of the protective atmosphere - when brought out into air the residual sodium promptly ignited).
5) There were issues with older alloys being corroded by the sodium coolant - but these are largely well controlled with modern materials.

France closed its big breeder power plant, Superphenix, for a variety of the above reasons. It's reliability had been dissapointing, and following a malfunction that required a long shutdown (contamination of the sodium - requiring the sodium to be meticulously filtered and rerefined) the government cancelled it's licence to operate. When several years later, the licence was reapproved and the plant was finally allowed to start operating the government finally killed it, stating high cost and too much down time (in fact, almost as much down time was due to licencing issues, rather than reliability issues).

Despite these limitations, proponents state a number of advantages of breeders:
1) Limitless supply of fuel, and because of incredible fuel efficiency even the lowest grade sources of uranium (e.g. seawater) can be efficiently utilised.
2) Potentially very safe. The sodium does not operate under pressure and has an enormous boiling point - high pressure explosions (like at chornobyl) or sudden boiling of the coolant are impossible - and pipe bursts are impossible because the reactor is not pressurised - if leaks do occur they tend to be very small. Sodium has excellent thermal conductivity hence no emergency cooling pumps are needed - the reactor is entirely capable of acting as its own heatsink.
3) Can consume plutonium (a waste product of conventional reactors) and 'minor actinides' (other plutonium like heavy metals which are minor waste products) as fuel. A big advantage for waste management as it is the plutonium and actinides that provide 99.9% of the long term radioactivity of the waste. (If you can deal with the plutonium and actinides - you turn nuclear waste from a 100,000 year problem into a 300 year problem).
[Breeder reactors can be configured not to 'breed' plutonium (produce less than they burn) or can be configured as plutonium neutral (produce exactly the same amount as they burn) depending on the requirements].

 

[BrownTown]

Breeder reactors do not produce more fuel then they consume, they simply can run on natural Uranium or Thorium instead of needing enriched uranium. Plutonium is created in the reactor be the transmutation of Uranium, so eventually that will run out.

 

[electrosoccertux]

Originally posted by: Peter
Germany had built a breeder reactor, but due to protests and the chernobyl disaster it never went online. We're shutting down ALL nuclear plants over the course of the next two decades - and we won't miss them. Power consumption figures are solidly heading downward, while energy generation from renewable sources is on the rise.

France and Japan had to take theirs offline after accidents, Russia keeps operating the one they have and plan another. The USA are on their sixth experimental one.

The technical problems and environmental risks are substantial: Plutonium is not only radioactive, but also incredibly poisonous. Breeders are natrium cooled, which acts highly corrosive to the innards of the reactor. Combined with the high pressure of the cooling agent due to the high core temperatures, leakages have proven to be the one big problem in breeders.

Incidentally, the German wiki article has a lot more substance to it than the English language one - including a table of all breeder plants that have been built.
http://en.wikipedia.org/wiki/Breeder_reactor
http://de.wikipedia.org/wiki/Schneller_Br%C3%BCter

No, they are NOT dangerous. Read: pebble bed. They have an inherent negative-feedback design that keeps them from melting down. They're 100% safe and produce much less radioactive waste than our coal plants spit into the air. Not to mention they don't produce CO2. But our country is full of uninformed people that [like yourself] think nuclear reactors are "unsafe".

 

[Mark R]

Originally posted by: BrownTown
Plutonium is created in the reactor be the transmutation of Uranium, so eventually that will run out.

However, if used in breeder reactors, the amount of uranium needed as primary source is very small.

In fact, the net energy gain is so vast that even extraordinary attempts to obtain uranium are reasonable.

Extraction of uranium from seawater (a process that has been demonstrated to work) would provide a truely renewable supply of uranium: the quantity of uranium dissolved in seawater is so vast that it could supply all energy needed by the human race for many millions of years. And, to top it off, natural erosion from rivers brings fresh uranium into the sea faster than we could ever use it.

 

[BrownTown]

Yeah, I know, its just as an engineer when someone says something produces more energy than it uses their views just get dismissed completely being as the laws of thermodynamics do not allow this. Obviously the power source is very large, and the fuel can last a long time, but it is finite.

 

[bobsmith1492]

Originally posted by: electrosoccertux

Originally posted by: Peter
Germany had built a breeder reactor, but due to protests and the chernobyl disaster it never went online. We're shutting down ALL nuclear plants over the course of the next two decades - and we won't miss them. Power consumption figures are solidly heading downward, while energy generation from renewable sources is on the rise.

France and Japan had to take theirs offline after accidents, Russia keeps operating the one they have and plan another. The USA are on their sixth experimental one.

The technical problems and environmental risks are substantial: Plutonium is not only radioactive, but also incredibly poisonous. Breeders are natrium cooled, which acts highly corrosive to the innards of the reactor. Combined with the high pressure of the cooling agent due to the high core temperatures, leakages have proven to be the one big problem in breeders.

Incidentally, the German wiki article has a lot more substance to it than the English language one - including a table of all breeder plants that have been built.
http://en.wikipedia.org/wiki/Breeder_reactor
http://de.wikipedia.org/wiki/Schneller_Br%C3%BCter

No, they are NOT dangerous. Read: pebble bed. They have an inherent negative-feedback design that keeps them from melting down. They're 100% safe and produce much less radioactive waste than our coal plants spit into the air. Not to mention they don't produce CO2. But our country is full of uninformed people that [like yourself] think nuclear reactors are "unsafe".

He was talking about a particular type of reactor, not nuclear power in general...

 

[Spinne]

I think Fusion Energy is the way of the future. As long as you can contain the initial radiation of the reaction (easy enough since it's primarily Gamma rays), you can get clowns to sell your by product!

 

[KF]

Originally posted by: electrosoccertux

No, they are NOT dangerous....
... they don't produce CO2. But our country is full of uninformed people that think nuclear reactors are "unsafe".

Unfortunately a lot of the people who do think, in their own opinion, they are well-informed also think (inaccurately) that "nukes" are unsafe, and they angrier, more vocal, more insistant, and more persistant. This has worked against nuclear energy.

Although I was never a strong opponent of nuclear reactors, or even particularely interested, I was once vaguely of the opinion that they were on balance not safe enough to have too near populated areas. I have changed mind. But is "safe" an opinion or a fact? What people need is a way to gauge safety. For example: I think we can solidly predict that death or injury due to nuclear reactors will never approach one thousandth of what they are due to electric power in the home, or natural gas cooking, or even sharp knives. To me that's reasonably safe. And this will remain true should we convert to 100% nuclear energy (from 20% now) and consume 1000 times the amount of energy per US person than we do now, because with experience our expertise will advance. I do look forward to the day when every person on the planet can afford to consume 1000 times the energy a person in the US does today. If sensible people prevail, it will happen.

Ever wonder what the function of bringing up the chemically poisonous nature of plutonium is? I've heard it quiet a bit. Is some one comtemplating eating plutonium? If people find this interesting, I am also told plutonium stinks. The man who got to name the new element said that part of the reason he chose the name was to have the abbreviation be Pu.

An interesting illustration of the nature of plutonium: The plutonium-based atom bomb was tested in the desert of the southwest US before they dropped its successor on Japan. (The other A-bomb dropped on Japan was uranium based.) The plutonium sphere that fueled the bomb was about the size of a grapefruit and plated to keep it from oxidizing in the air. It was carried to the site in a plain suitcase and was passed from hand to hand to the technicians without any radiation shielding.

Sound wreckless? Not really.There was a demo on TV. A chunk of plutonium about the size of the end of your finger was on a table. They put the Geiger counter next to it and the meter went full scale. Then they put a piece of paper between the detector and the plutonium, and the meter dropped to background level. Yes, that is the penetration level of the radiation emitted by plutonium. Not much. Sure, it needs to be treated with the appropriate knowledge of its effects, but the radiation that will make it through the layer of dead skin cells covering your body is practically nil. Handling a nice, clean ball of plated plutonium is not dangereous.

So what is this crap? : "Plutonium is the most toxic substance known to man." There is a video clip of Walter Cronkite, the "most trusted man in America" (back in the Viet Nam era) uttering this complete rubbish during a newscast as if he knew what he was taking about. I wonder if old Walt ever knew anything about what he was reading? He sure could deliver it convincingly though.

Some people convey the impression that the natural world is close to radioactivity free, but it isn't. I didn't know that uranium was disolved in sea water until I read this thread. But I did know that tritium, the radioactive isotope of hydrogen, was a significant component of ordinary water. Water is about 80% of our bodies. Carbon 14 is radioactive, and it is found in all living things. The portion of radioactive carbon left is how they date more recent fossils. There are other elements that our bodies contain which also have a measurable component of a radioactive isotope, because all natural sources of these elements contain them. Radioactive potassium is supposed to be the most significant. None of these are notable hazards of course. But that's the point. Radiation at this low level has no discernable effect. Certainly nothing on the level of getting burned in the kitchen or getting cut by a knife. The modes of handling in a nuclear power plant guarantee that no person outside the plant will ever get harmed by radiation in normal operation, and astronomically unlikely even in the case of a major system failure.

The inherently safe operation of nuclear power plants will never get any air play. It's boring. There is no one to accuse falsely. There is nothing to scream about. If cheerful, calm and serious people are not as insistant as the wackos, the wackos will prevail.