How Can Waste Heat from Power Plants be Used to Produce Hydrogen?

[Hawknc]

You're kidding right?

Would you prefer I pretended to know things I didn't know instead?

Right now, they'd indirectly use fossil fuels. That's a given I think everyone understands. But coal is most certainly a lesser of the two evils and eventually we will have to move from that as well. Of course, if you have any alternative fuels that don't require similar amounts of electricity and are viable on the same sort of scale, this would be the time to present them...

 

[Rach3]

Would you prefer I pretended to know things I didn't know instead?

I'm sorry, my mistake. I misunderstood your phrasing.

But coal is most certainly a lesser of the two evils...

I'd thought coal was the much greater evil, what with the sulfur and mercury content...

 

[Anttech]

Clean coal is way less polluting, and uses the same resource (ie coal).

New "clean coal" technologies are addressing this problem so that the world's enormous resources of coal can be utilised for future generations without contributing to global warming. Much of the challenge is in commercialising the technology so that coal use remains economically competitive despite the cost of achieving "zero emissions".

As many coal-fired power stations approach retirement, their replacement gives much scope for 'cleaner' electricity. Alongside nuclear power and harnessing renewable energy sources, one hope for this is via "clean coal" technologies, such as are now starting to receive substantial R&D funding.

http://www.uic.com.au/nip83.htm

 

[Rach3]

Clean coal is way less polluting, and uses the same resource (ie coal).

CO2 sequestration is completely untested and untried. The only thing even on the drawing board is a GWB plan to build a http://www.fossil.energy.gov/programs/powersystems/futuregen/. Imagine the fight they'll put up against carbon sequestration if it ever comes up!

Seriously: the prototype alone has a timetable on the scale of a decade. Even nuclear plants could be constructed faster (and that's saying something). I say this is just an effort to distract us from their current, egregious violations, the ones that can be fixed now and cheaply (see http://www.fossil.energy.gov/programs/powersystems/pollutioncontrols/). For the time being, coal is definitely the worst power source around.

 

[russ_watters]

A gallon of gasoline contains approximately 130 megajoules of chemical potential energy. Americans drove 2,923 billion miles in 2004 [1]. If the average car gets about 30 miles per gallon (which is heavily on the optomistic side), American motorists expended a total of about 3.5 x 10¹² kWh of energy in 2004.

By contrast, American consumption of electricity was only 1.4 x 10¹² kWh in 2001 [2].

In other words, Americans consumed roughly three times as much energy in their automobiles in the form of gasoline and diesel as they did energy from electricity.

I think you forgot to factor in the efficiency of the engine cycle? Americans didn't get 3.5x10¹² kWh of useable energy out of their cars, they only got perhaps a third of that, whereas the power you get from your electrical outlet is already usable.

That would fit what I've heard in the past - that our energy use is roughly evenly split between power and cars.

Still, your general point is valid: we would need a enormous increase in our electrical infrastructure to support the transition to battery powered cars.

 

[chroot]

Sure, and electric generators aren't 100% efficient either, and I left that out (I was just going for a rough proportion). The 1.41 trillion kWh of electric power used by the US was probably more like 3 trillion kWh at the generators, the balance lost in transmission and end-user appliance inefficiencies.

Give or take, however, the point I was trying to make is simply that we're no more ready for a nation-wide fleet of electric cars than we are for a nation-wide fleet of hydrogen fuel-cell powered cars.

- Warren

 

[Skyhunter]

we would need a enormous increase in our electrical infrastructure to support the transition to either battery powered cars.

Eventually, yes we would. However for the most part the cars would be recharged during off peak hours, when rates are low and there is plenty of capacity on the grid.

I don't think EV's are the future, but it I do believe that they could have substantially effected the air quality in California cities had the zero emission standard been enforced. As it is we had money earmarked in the Bay Area to fund free transit during "spare the air" days, days when the air quality index was forecast to exceed 100. These days occur in the summer. In the summer 2004 there were 2 such days, in 2005 there was one. There were monies allocated for 3 days in 2006 and the first 3 days of summer were spare the air days. The state allocated funds for 3 more. We have already had 7 this year.

Part of the quandary GM had with marketing an electric vehicle was that they would need to point out the advantages of an EV over an internal combustion engine. They were not willing to dis their main product line in order to meet the California law. The fact that the EV-1 was a technological success is why I believe they made sure that every single one was taken off the road. They really did not want the idea to catch on.

There will be electric cars, because the technology is already here. Smashing all the EV-1s did not kill the electric car, It just left GM without the means to compete effectively with Toyota. It would have also done wonders for their average MPG as well.

 

[Skyhunter]

Give or take, however, the point I was trying to make is simply that we're no more ready for a nation-wide fleet of electric cars than we are for a nation-wide fleet of hydrogen fuel-cell powered cars.

- Warren

Just like in Field of Dreams, if you build it they will come.

I agree, that we are not ready, however whatever we do will require more development. The majority of opposition to smart growth is not so much the traditional developers, but the anti development people who just can't grasp how more development done the right way actually addresses all their concerns that they raise when opposing traditional development.

We are in the community input phase of a TOD (Transit Oriented Development) for a light rail station. The opposition, aside from some of the more ludicrous claims of a conspiracy, is that more density means more traffic. It is a challenge, but slowly we are changing minds and bringing the community up to speed on the concept of mixed use TOD, where the people and retail stores are within walking/cycling distance, all located close to public mass transit.

 

[PRodQuanta]

http://www.evworld.com/library/abrooks_carb_nov2_05.pdf" seems to think that electric is the way to go (over hydrogen) for automobiles. It is more geared toward CO2 emissions.

I am interested in what you all think of this!

Paden Roder

WARNING: The site I have hyperlinked is a .pdf file. Just letting you know beforehand.

Edit: I found http://www.evworld.com/library/Tesla_21centuryEV.pdf" in the EV World library that argues EV over hydrogen and gasoline.

Also, WARNING: Both sites I have hyperlinked are .pdf files. Just letting you know beforehand.

 

[Hawknc]

Not that I argue against the articles, but as unbiased sites go, "EV World" probably ain't one of them. ;)

Actually, now that I read the first article, it makes a lot of bad assumptions (like assuming 33% renewable energy). It's got some reasonable points, but it's most definitely not an unbiased presentation.

 

[russ_watters]

http://www.evworld.com/library/abrooks_carb_nov2_05.pdf" seems to think that electric is the way to go (over hydrogen) for automobiles. It is more geared toward CO2 emissions.

I am interested in what you all think of this!

That's a pretty flawed report. I must admit that some of their fuzzy math escapes me, but they miss a couple of key points:

-It looks like they are attributing negative emissions to renewable energy based on the emissions that would have been produced by other sources. No. Zero is zero.
-Hydrogen can be generated for free with waste heat from existing power plants.
-They note that you need to increase generation capacity to handle either, but if you are adding energy capacity for that specific purpose, you can attribute all the usage to it. Ie, in either case, you end up with zero emissions. So the relevant factor is simply which can do more with a kW of energy. The answer is probably batteries, depending on how well steam reforming of methane works, but...
-They don't discuss the performance or economics of the vehicles. If batteries were good enough and cheap enough, we wouldn't need to have this conversation.

http://www.evworld.com/library/Tesla_21centuryEV.pdf" in the EV World library that argues EV over hydrogen and gasoline.

-They mention steam reforming but don't consider the retrofit of existing plants to capture free (currently wasted) energy for it.
-They don't mention economics - and why would they? That's literature for the Tesla Roadster.
-They mention that if future power plants are used for a study equal consideration should be given to electric and hydrogen (ie, either attribute all of it or whatever the fraction of power in the grid it comprises - either way, be consistent). However, again, you can get extra energy by capturing waste heat to make hydrogen.
-They don't mention range. I'm skeptical of their range claims.

 

[russ_watters]

Just like in Field of Dreams, if you build it they will come.

Big difference: Here, the players (consumers) aren't lined-up waiting for the field to be built. You have to convince them that they should want to play before they will come.

Eventually, yes we would. However for the most part the cars would be recharged during off peak hours, when rates are low and there is plenty of capacity on the grid.

True. That could reduce the generation overhead by 50%.

Part of the quandary GM had with marketing an electric vehicle was that they would need to point out the advantages of an EV over an internal combustion engine. They were not willing to dis their main product line in order to meet the California law. The fact that the EV-1 was a technological success is why I believe they made sure that every single one was taken off the road. They really did not want the idea to catch on.

That is a very reasonable, non-conspiracy-theory-ish point. Something that gets overlooked so much in these debates is that companies exist to make money and for them to act in that interest is not only the reasonable but correct thing to do. This is capitalism: market changes must be driven by the market (or, [gasp] perhaps even the government - just don't tell my boss I said that).

 

[PRodQuanta]

Thanks Russ! Great analysis!

The reason I was on EV World is because I'm going to a Youth Global Leader Summit in Omaha, Nebraska entitled http://www.aidemocracy.org/omaha.cfm" and one of the keynote speakers is going to be Bill Moore (Publisher and Editor of EV World).

Paden Roder

P.S.- I'll make sure to represent PF and mention some of the claims made in this thread (maybe)

 

[PRDan4th]

I don't know how they make H2 from waste heat from power plants! Waste heat is not "free" and it is of very low quality (only 10 to 15 deg. F above ambient). About 50 % of the heat input to coal/oil/gas power plants is condenser loss as waste heat. It would be nice to find a use for this energy source, but it is not easy or it would have been done.

H2 is made primarlly by the reforming of natural gas. This process takes heat and liberates CO2 in a form that could be sequestered or used in other processes because it is concentrated and not mixed with air or N2. The dissociation of water to produce H2 & O2 takes electricity that must be generated from other fuels and will discharge CO2 with large amounts of N2 making it very difficult to separate and sequester.

Methane is the best short term answer to low-CO2 fuel for power generation or transportation. The world is awash in it in sub-sea hydrate formations that are just waiting for technology solutions for safe production. CNG or LNG now with H2 from CH4 later.

 

[Hawknc]

Yeah, I've never heard of H2 generation from waste reactor heat either. Would you be able to elaborate on it a little? Is it viable on a large enough scale to take serious market share from petrol-driven cars?

 

[edward]

Here is a link to a new EV /hybrid that Subaru is working on,
http://www.worldcarfans.com/news.cfm/newsid/2050826.003/subaru/1.html

It sounds promising.

 

[russ_watters]

I don't know how they make H2 from waste heat from power plants! Waste heat is not "free" and it is of very low quality (only 10 to 15 deg. F above ambient). About 50 % of the heat input to coal/oil/gas power plants is condenser loss as waste heat. It would be nice to find a use for this energy source, but it is not easy or it would have been done.

I guess I'm not sure about the waste heat thing - it is something I've heard but not really read up much on. Are you sure about the 10-15F above ambient, though? My company recently did an HVAC design fora gas turbine plant and though we didn't get that temperature info from GE, we did have to supply enough air to the building so that the turbine enclosures could be cooled by ventilation alone. I can't imagine that the air being exhausted through the enclosure (much less the surface of the turbine itself) is only 15F above ambient. I do recognize, though, that once they do an aft-end boiler, there isn't much left to harness in another way. Perhaps, though, what I read about was just replacing the steam turbine with a steam reformer. Researching now, I found that the process takes place at pretty high temperature: 700-900C.

And another one I don't remember where I heard, nuclear plants are far less efficient thermodynamically than other power plants, and I thought there was more waste heat avalable to be captured there as well.

Nevertheless, an aft-end boiler is still a thermodynamic process with the inherrent limitations on efficiency. So even if you remove that to get the hydrogen, you likely still get more out of your BTU of input that way.