Renewables Get Some Tough Love From Google

[zapta]

Fear-mongering? Is that really your best argument, SgtRock?

That's exactly what you are doing for long time here to justify taking other people money to finance your pet cause.

[coppice]

You can skip the generation of electricity and use the burning wood to directly power a heat pump. At least one company currently makes natural gas powered heat pumps for domestic heating. You save a lot on gas, and the environment saves on CO2.

yes, a direct coupling between the steam turbines is great, saves you 10% on the transmission loss and 30% on the efficiency of the induction motor below 5 hp.
but you won't get better performance for anything less than a few thousand hp, which is about right on the level of say, a natural gas turbine driven heat pump for a shopping mall in miami.

A good performing heat pump can power itself, and output considerable surplus energy. A 4 times multiple between the energy to power the pump and the energy out of the pump is practical. That makes it a potential renewable energy source. The energy source doesn't suffer the same unpleasant swings as wind and direct solar (I would class heat pumping from the environment as indirect solar). Sure, a heat pump is less effective when extracting heat from a cool environment, but it still works. The biggest enemy of heat pump production is not the energy source, but humidity, as cold humid conditions require special measures to stop the equipment freezing over. If the pumps are sized to give enough output in cold weather, no storage system is needed. Most of the energy we use ends up as environmental heat, so the system would be cyclic.

Self powered heat pumps, using external energy only to get them started, existed in the late 19th century. I've seen them in museums. They couldn't achieve a 4 times multiple in those days, so they were less effective than a modern one would be, but they worked OK.

[SgtRock]

Greeting EEVBees:

--MC smells bullshit so often he must live next door Old Macdonald EIEIO. The quote from President Obama is a famous one, that of course anyone can look up, and nobody but a complete fool would attempt to mislead by using such a famous quote. All quotes are partial quotes, otherwise they would all be the entire speech or article, no? And yes it referred to Obama's infamous "Carbon Cap and Trade" swindle. The operative point being that "electricity rates would necessarily skyrocket" as they are doing everywhere the left gets its hands on energy policy. So MC has researched the quote and found out that is says exactly what I said it says with regard to carbon and government energy policy. He seems to be unwilling to admit that anyone can honestly disagree, and also thinks that everyone who does not agree is either selfish, or wanting to deliberately endanger everyone or is deliberately attempting to deceive by using dishonest bullshit quotes. In other words he seems to be unwilling to grant others the same respect they grant him. Over the months I have, upon more than on occassion had kind words for him. I even tried to calm the waters, when the moderators were about yea far from banning him, but he has gone right back to impugning the honesty, character and motives of everyone who disagrees.  Hence I will no longer respond to any of his postings.

--To everyone else, I thank you for your contributions be they yea or nay, all are welcome, and I am constantly learning from all of you. As usual I admit that I am frequently wrong, but never in doubt.

"If Mr. Einstein doesn't like the natural laws of the universe, let him go back to where he came from."
Robert Benchley 1889  -  1945
 
Best Regards
Clear Ether

[coppice]

Does anyone still argue for reintroducing suplhur  and lead pollution?

Of course they do. Haven't you noticed the number of people who pollute as if its a noble cause?

[Zero999]

Self powered heat pumps, using external energy only to get them started, existed in the late 19th century. I've seen them in museums. They couldn't achieve a 4 times multiple in those days, so they were less effective than a modern one would be, but they worked OK.

I call bullshit on self powered heat pumps.

It's true that a heat pump does output more heat than the energy required to power it but it is not self powered. It's not possible to build a self powered heat pump because it would violate the second law of thermodynamics and thus be a perpetual motion machine. You do need energy to power a heat pump and it is more efficient than just burning gas alone but it still needs power to work.

yes, a direct coupling between the steam turbines is great, saves you 10% on the transmission loss and 30% on the efficiency of the induction motor below 5 hp.
but you won't get better performance for anything less than a few thousand hp, which is about right on the level of say, a natural gas turbine driven heat pump for a shopping mall in miami.

That's not true. Most gas powered heat pumps I've researched use the absorption cycle, rather than mechanical vapour phase cycle and it's much more efficient than using electricity generated by a coal fired power station to heat your home because all the energy is converted to heat, plus another 40% extra pumped in from the environment.

EDIT:
Using a natural gas powered heat pump is still more efficient than an heat pump powered by electricity generated by natural gas power station. In a power station, the waste heat is just discharged into the environment but in a gas powered heat pump, all the heat used to do the work is used to heat your home.

Thermodynamically speaking, the maximum efficiency from gas to heat when a heat pump is powered by a gas power station is only 100% but a gas powered heat pump is better than that.

[coppice]

Self powered heat pumps, using external energy only to get them started, existed in the late 19th century. I've seen them in museums. They couldn't achieve a 4 times multiple in those days, so they were less effective than a modern one would be, but they worked OK.

I call bullshit on self powered heat pumps.

It's true that a heat pump does output more heat than the energy required to power it but it is not self powered. It's not possible to build a self powered heat pump because it would violate the second law of thermodynamics and thus be a perpetual motion machine. You do need energy to power a heat pump and it is more efficient than just burning gas alone but it still needs power to work.

I think you are missing the word "pump" in "heat pump". It sucks heat from the environment, and it sucks a lot more heat than it uses to suck that heat. It is in no sense a perpetual motion machine. There is nothing to stop you using the heat which the pump collects to power the pump.

[Zero999]

Self powered heat pumps, using external energy only to get them started, existed in the late 19th century. I've seen them in museums. They couldn't achieve a 4 times multiple in those days, so they were less effective than a modern one would be, but they worked OK.

I call bullshit on self powered heat pumps.

It's true that a heat pump does output more heat than the energy required to power it but it is not self powered. It's not possible to build a self powered heat pump because it would violate the second law of thermodynamics and thus be a perpetual motion machine. You do need energy to power a heat pump and it is more efficient than just burning gas alone but it still needs power to work.

I think you are missing the word "pump" in "heat pump". It sucks heat from the environment, and it sucks a lot more heat than it uses to suck that heat. It is in no sense a perpetual motion machine. There is nothing to stop you using the heat which the pump collects to power the pump.

No I didn't miss the word heat pump. I understand that a heat pump sucks in heat from the environment and moves it into your home.

You don't understand the second law of thermodynamics which indeed does say you can't use the heat collected by the pump to power the pump, in much the same way you can't use the electricity generated by a hydroelectric power plant to pump all the water which has gone through the turbine back to the top of the dam.

[mamalala]

You don't understand the second law of thermodynamics which indeed does say you can't use the heat collected by the pump to power the pump, in much the same way you can't use the electricity generated by a hydroelectric power plant to pump all the water which has gone through the turbine back to the top of the dam.

It seems you are confusing an open system with a closed system. Your example for the hydro plant is a closed system, there is no energy input from the outside, only losses in the system. However, a heatpump is a open system. You use some amount of energy (in the form of electricity) to pump out more energy (in the form of heat) from another source. What you claim is equal to saying, for example, that a coal fired power plant can not produce enough electricity to power the train that delivers the coal to said plant.

If one can convert the heat that heat pump extracts from the environment into electricity (or another form of energy that can drive the pump) at an efficient enough level, there should be no problem with the output of the pump powering said pump. After all, there is an external energy input into that system: the heat it extracts from the environment.

Greetings,

Chris

[coppice]

You don't understand the second law of thermodynamics which indeed does say you can't use the heat collected by the pump to power the pump, in much the same way you can't use the electricity generated by a hydroelectric power plant to pump all the water which has gone through the turbine back to the top of the dam.

A heat pump is nothing like your hydro example. There you have some energy, and if you try to use it to do the same amount of work as that energy you will fail due to losses. No arguments there.

A heat pump moves energy. Unless you do something weird, like insulate the side of the heat pump doing the collecting, the cooling of the environment near the collector causes more heat to keep flowing in from the environment further out. The maximum rate at which you can gather heat is determined by that replenishment rate. You know that more energy is gathered than is used by the pump. Does the energy for the pump have some special quality, that makes it unlike the collected energy? Of course not. Its not at a very high temperature, so there are challenges in using it effectively to drive the pump, but its not impossible.

Saying a heat pump powered by its collected energy is impossible is like saying a tanker truck can't gather more diesel than it consumes.

[magetoo]

If one can convert the heat that heat pump extracts from the environment into electricity

That's the rub - you can't.  If you want to generate electricity or any other useful work using a heat pump, you need a difference in temperature, not just heat.

On the other hand, if you have two temperature differentials, you can power a pump from one and maintain the other.  In practice I suppose that would mean something like concentrating solar heat for the hot end or cold water from the bottom of a lake for the cold end.

[mamalala]

That's the rub - you can't.  If you want to generate electricity or any other useful work using a heat pump, you need a difference in temperature, not just heat.

True, that's why i added "(or another form of energy that can drive the pump)" which for some reason you have omitted.

However, the "rub" in my post is not about how well one can convert heat into electricity, but to try and explain to Hero999 that there is a difference in open and closed systems, since she/he was banging on about thermodynamics. And from that perspective, going by just thermodynamics, there is nothing wrong with the energy output of a heat pump being able to drive that pump, no laws are broken with that, since it is an open system that has an external energy input.

Again, how feasible and/or possible it is to convert the heat output of the pump into something that can drive that pump, that is a completely different matter.

Greetings,

Chris

[Zero999]

It seems you are confusing an open system with a closed system. Your example for the hydro plant is a closed system, there is no energy input from the outside, only losses in the system. However, a heatpump is a open system. You use some amount of energy (in the form of electricity) to pump out more energy (in the form of heat) from another source. What you claim is equal to saying, for example, that a coal fired power plant can not produce enough electricity to power the train that delivers the coal to said plant.

Alright, perhaps that wasn't the best example because it refers to the first law of thermodynamics, rather than the second law.

And from that perspective, going by just thermodynamics, there is nothing wrong with the energy output of a heat pump being able to drive that pump, no laws are broken with that, since it is an open system that has an external energy input.

For all intents on purposes though, a heat pump powering itself is effectively a closed system. Unless there's an external energy source of sink, the entropy in the system will increase, until a thermodynamic equilibrium is reached and the pump slows to a halt.

If one can convert the heat that heat pump extracts from the environment into electricity (or another form of energy that can drive the pump) at an efficient enough level, there should be no problem with the output of the pump powering said pump. After all, there is an external energy input into that system: the heat it extracts from the environment.

No you can't do that because it isn't possible to make it efficient enough to power itself, as that would violate the second law of thermodynamics!

Does the energy for the pump have some special quality, that makes it unlike the collected energy? Of course it does. It's not at a very high temperature, which means that it's impossible to use it to drive the pump with enough efficiency to make it self sustaining - the lower the temperature differential, the poorer the efficiency!

Corrected.

Saying a heat pump powered by its collected energy is impossible is like saying a tanker truck can't gather more diesel than it consumes.

Of course a heat pump powered by its collected energy is impossible because it violates the second law of thermodynamics. A tanker gathering diesel does not because the diesel has the potential to do work.

That's the rub - you can't.  If you want to generate electricity or any other useful work using a heat pump, you need a difference in temperature, not just heat.

On the other hand, if you have two temperature differentials, you can power a pump from one and maintain the other.  In practice I suppose that would mean something like concentrating solar heat for the hot end or cold water from the bottom of a lake for the cold end.

Exactly. You need a temperature differential to do work.

A heat pump uses the temperature difference between the gas flame and your home to move heat from the lower temperature outside into your house. You can't use the heat moved by the pump to power it because it would involve cooling down your house again. To do work (whether it be to generate electricity, momentum or move heat) you need a temperature differential.  The higher the temperature differential, the more efficiently the heat can be used. Look at it in a similar manner as potential difference, there may be lots of electrons in a piece of metal but they won't do anything unless there's there's a potential difference.

[mamalala]

For all intents on purposes though, a heat pump powering itself is effectively a closed system. Unless there's an external energy source of sink, the entropy in the system will increase, until a thermodynamic equilibrium is reached and the pump slows to a halt.

No, it is not a closed system, because there is an external energy source that enters into the system: the heat that the pump moves. That heat is put into the system by things like the sun heating up the earth. The pump doesn't generate energy out of nothing, it simply moves it from one side to the other. At that other end you have more energy than what you used to operate that pump.

I'm surprised that this is so hard for you to understand. You would be right, of course, if we were talking about the pump using an initial fixed amount of energy in the form of heat, pumping that around "in circles", and have that drive itself. But that would then be a closed system, since there is no external source of heat entering into it anymore.

So, if one could use some (or all) of the heat energy that the pump moves out, to in turn power that pump, it would run until there is no more external heat coming in, like when the sun dies for example. But until then, it would just work.

Greetings,

Chris

[magetoo]

That's the rub - you can't.  If you want to generate electricity or any other useful work using a heat pump, you need a difference in temperature, not just heat.

True, that's why i added "(or another form of energy that can drive the pump)" which for some reason you have omitted.

Fine.  You can't convert the heat that the heat pump extracts from the environment into electricity or any other form of energy such that this energy can drive the pump.  Better?

However, the "rub" in my post is not about how well one can convert heat into electricity, but to try and explain to Hero999 that there is a difference in open and closed systems, since she/he was banging on about thermodynamics.

You're not doing a very good job of explaining, since your example looks exactly like a closed system - there's just heat in a box, and the box happens to be the size of the Earth.  What source of energy, outside of the box, does this heat pump use exactly?

If you say "heat from the sun", no problem.  But now the pump is no longer powered by heat from the environment, it is powered by a temperature difference between, say, concentrating solar heat (hot end) and the environment (cold end).

And from that perspective, going by just thermodynamics, there is nothing wrong with the energy output of a heat pump being able to drive that pump, no laws are broken with that, since it is an open system that has an external energy input.

How do you run a pump on just heat?  Every form of engine that "runs on heat" actually uses a temperature differential.  What temperature differential is the pump running off?

The one it creates itself?  In that case we are talking about a closed system (pump -> temp diff -> pump), not an open one.

[mamalala]

You're not doing a very good job of explaining, since your example looks exactly like a closed system - there's just heat in a box, and the box happens to be the size of the Earth.  What source of energy, outside of the box, does this heat pump use exactly?

If you say "heat from the sun", no problem.  But now the pump is no longer powered by heat from the environment, it is powered by a temperature difference between, say, concentrating solar heat (hot end) and the environment (cold end).

What do you think where the heat that the pump moves finally comes from? Pixie dust? Angels? No, things like the sun and the earth's core. I thought that that would go without saying, but it seems i had too high an expectation. Yes, i know that there must be a temperature differential. Another thing that should go without saying. And yes, once the universe dies the heat death, there is no differential to exploit anymore. Fact is still that a heat pump extracts more energy from the environment than what was put into the pump to operate it. Up until that source is depleted (i.e. cooled down enough), obviously.

Greetings,

Chris

[magetoo]

No, it is not a closed system, because there is an external energy source that enters into the system: the heat that the pump moves.

Maybe this is the central misunderstanding.  How does the pump move this heat around if the heat is also the external energy source?

Define what's inside and what's outside the black box.  Everything works as long as you have energy coming in from outside the black box, and heat sitting around inside the black box - you use the external source of energy to do useful work inside the box.  This is an open system, which we all agree works just fine.

I think we can also agree that if you just have heat sitting in a box, this is a closed system, and doing useful work is going to be impossible.


Perhaps you are not expressing it clearly, but it seems like the heat you talk about is simultaneously available to both the inside as just heat to be moved around and outside the box as a temperature differential.

[magetoo]

What do you think where the heat that the pump moves finally comes from? Pixie dust? Angels? No, things like the sun and the earth's core. I thought that that would go without saying, but it seems i had too high an expectation.

Well, adjust your expectations.  (Or even better, your explanations.)

Ok, so we run our pump off a second temperature differential then?  No problem with that.

Yes, i know that there must be a temperature differential. Another thing that should go without saying. And yes, once the universe dies the heat death, there is no differential to exploit anymore. Fact is still that a heat pump extracts more energy from the environment than what was put into the pump to operate it.

Sure.  There was never any disagreement that a heat pump can move more energy around than the amount that was put in to run it, just some confusion around whether there was an external energy source or not.

[Zero999]

What do you think where the heat that the pump moves finally comes from? Pixie dust? Angels? No, things like the sun and the earth's core. I thought that that would go without saying, but it seems i had too high an expectation. Yes, i know that there must be a temperature differential. Another thing that should go without saying. And yes, once the universe dies the heat death, there is no differential to exploit anymore. Fact is still that a heat pump extracts more energy from the environment than what was put into the pump to operate it. Up until that source is depleted (i.e. cooled down enough), obviously.

No one here has ever had a problem understanding that the heat sourced by the heat pump comes from the earth, sun, the earth's core etc.

The only misunderstanding has been that a heat pump can run from the heat in the ambient environment once it's been started by gas. Of course it can't. The heat pump will stop working, when the gas is cut off. It's not possible to create heat pump which is self sustaining.

[coppice]

What do you think where the heat that the pump moves finally comes from? Pixie dust? Angels? No, things like the sun and the earth's core. I thought that that would go without saying, but it seems i had too high an expectation. Yes, i know that there must be a temperature differential. Another thing that should go without saying. And yes, once the universe dies the heat death, there is no differential to exploit anymore. Fact is still that a heat pump extracts more energy from the environment than what was put into the pump to operate it. Up until that source is depleted (i.e. cooled down enough), obviously.

No one here has ever had a problem understanding that the heat sourced by the heat pump comes from the earth, sun, the earth's core etc.

The only misunderstanding has been that a heat pump can run from the heat in the ambient environment once it's been started by gas. Of course it can't. The heat pump will stop working, when the gas is cut off. It's not possible to create heat pump which is self sustaining.

Of course a heat pump can't be self-sustaining. We are talking about one that is sustained by the heat from the sun, in the form of environmental heat. Some of that heat ends up as available energy for useful work, and a portion goes back to operate the machinery. If you understand that for every kW you consume in a good heat pump you will get 3 to 4kW moved from the input side to the output side, I can't imagine why you are sure that this energy is inadequate to operate the machine. If every little open bit of the closed system of the universe individually obeyed the 2nd law of thermodynamics life wouldn't exist to be even considering this.

[Artlav]

If you understand that for every kW you consume in a good heat pump you will get 3 to 4kW moved from the input side to the output side, I can't imagine why you are sure that this energy is inadequate to operate the machine.

Heat energy is not the same as usable energy, unfortunately.
There is a fundamental limit on how much power you can extract from a given temperature difference, and unsurprisingly it is less than the power needed to maintain that difference.
The confusion probably comes from the use of KWh for both the heat moved and the electricity consumed.

Key words - Carnot's theorem.

[Zero999]

Of course a heat pump can't be self-sustaining. We are talking about one that is sustained by the heat from the sun, in the form of environmental heat. Some of that heat ends up as available energy for useful work, and a portion goes back to operate the machinery. If you understand that for every kW you consume in a good heat pump you will get 3 to 4kW moved from the input side to the output side, I can't imagine why you are sure that this energy is inadequate to operate the machine. If every little open bit of the closed system of the universe individually obeyed the 2nd law of thermodynamics life wouldn't exist to be even considering this.

But your said:

I think you are missing the word "pump" in "heat pump". (1) It sucks heat from the environment, and it sucks a lot more heat than it uses to suck that heat. (2) It is in no sense a perpetual motion machine. (3) There is nothing to stop you using the heat which the pump collects to power the pump.

No one has a problem with #1 & #2.

It's the last statement which is false:

There is nothing to stop you using the heat which the pump collects to power the pump.

There is something which stops you from using the heat collected by the pump to power the pump. It's known as the second law of thermodynamics. Do you see what we've been saying now?

[magetoo]

Of course a heat pump can't be self-sustaining. We are talking about one that is sustained by the heat from the sun, in the form of environmental heat.

Are we?  Let's define some terms.  I and Hero999 are talking about having a heat pump that moves this "environmental heat" around, and uses a separate source of energy to do that.

This separate source of energy can be something like electricity, gas, or a temperature difference.  It can not be simply "heat" - it needs to be a differential; just like you need a potential (or voltage) to do useful work using electricity you also need a temperature differential to do useful work in a heat engine.


So are you assuming that there is a "second pole" of the "heat battery" hooked up somewhere (i.e. a separate temperature difference) and I'm just too dumb to understand it?  This would certainly explain the disagreement.

Or are you saying that you can get useful work done by just having heat?  (by hooking up just one wire to the battery)

Or are you saying that you use the heat differential (electrical potential) of the heat source to power the pump that puts heat (electrons) back into the heat source (battery)?

To me, that last one looks a lot like a closed system, not an open one.

Or something else entirely?

(edit: formatting and clarification)

[coppice]

If you understand that for every kW you consume in a good heat pump you will get 3 to 4kW moved from the input side to the output side, I can't imagine why you are sure that this energy is inadequate to operate the machine.

Heat energy is not the same as usable energy, unfortunately.
There is a fundamental limit on how much power you can extract from a given temperature difference, and unsurprisingly it is less than the power needed to maintain that difference.
The confusion probably comes from the use of KWh for both the heat moved and the electricity consumed.

Key words - Carnot's theorem.

Carnot's theorem applies to heat flow between 2 reservoirs. That is, a closed system. When consumers are constantly drawing heat from one side, and the environment is constantly replacing heat on the other, it isn't a closed system any more, and the picture looks more interesting. kWh are kWh whether they are heat, electricity, water pushed uphill, or chemical energy in a battery. Some forms are just easier to use than others for a particular application. If the small temperature difference you have isn't enough to drive a conventional heat engine, maybe you can use the energy to grow bacteria that feed directly off heat, and burn the biomass to get a high temperature for a conventional heat engine.

[Artlav]

Carnot's theorem applies to heat flow between 2 reservoirs. That is, a closed system. When consumers are constantly drawing heat from one side, and the environment is constantly replacing heat on the other, it isn't a closed system any more, and the picture looks more interesting.

If you have a heat reservoir, like an underground lake - then sure, you can get power on the difference between the ambient and the lake, using the day-night cycle or weather variations.

But if you create the difference, then you can't get the same power back from it - it would take more energy to create it than can be extracted from it.

kWh are kWh whether they are heat, electricity, water pushed uphill, or chemical energy in a battery. Some forms are just easier to use than others for a particular application. If the small temperature difference you have isn't enough to drive a conventional heat engine, maybe you can use the energy to grow bacteria that feed directly off heat, and burn the biomass to get a high temperature for a conventional heat engine.

Read Carnot's theorem more carefully.
It does not matter whether it's a conventional engine, peltier, bacteria, or something else.

There is a fundamental limit on the fraction of energy that can be extracted from heat.
There might be KWh of heat pumped into the room, but only a fraction of it can be converted back into usable energy.

Key word - Entropy.

[Zero999]

Carnot's theorem applies to heat flow between 2 reservoirs. That is, a closed system. When consumers are constantly drawing heat from one side, and the environment is constantly replacing heat on the other, it isn't a closed system any more, and the picture looks more interesting.

That is true but it's only an open system when there's an external supply of energy. The external source of power will slowly be returned to the environment via lossy thermal insulation, unless it's somehow stored. As long as the heat pump has gas, electricity or even liquid nitrogen, yes it's possible to use something cold to heat your home, as long as it's significantly colder than the ambient, it doesn't matter, it'll work. The thing is, as soon as you cut of the supply of external power, the temperature inside the house will move towards the same as the environment. If there isn't enough energy from the sun or wind that can be harvest to heat/cool the house above/below the environment then it will return to the steady state, i.e. ambient temperate.

kWh are kWh whether they are heat, electricity, water pushed uphill, or chemical energy in a battery. Some forms are just easier to use than others for a particular application. If the small temperature difference you have isn't enough to drive a conventional heat engine, maybe you can use the energy to grow bacteria that feed directly off heat, and burn the biomass to get a high temperature for a conventional heat engine.

As the temperature difference gets smaller, it gets exponentially less efficient to extract more work from the system and  that wouldn't work, since bacteria don't convert heat to biomass, they have to obide by the laws of physics like everything else.