Debunking the hydrogen economy

[kmarinas86]

The only way a hydrogen economy would make sense is if it produced energy (e.g. via fusion).

Without getting energy from hydrogen, fuel cell vehicles and etc are basically overly complicated batteries.

 

[Ygggdrasil]

However, batteries currently are not very good at storing energy and electric vehicle cannot travel distances comparable to gas powered vehicles. Using hydrogen as an intermediary for energy storage could allow them to act as a better "battery" with a greater range than electric cars.

However, I do agree that a lot more work is needed on hydrogen in order to determine whether it will actually be feasible. As you correctly mentioned, an environmentally friendly hydrogen economy relies on the development of a renewable energy infrastructure as hydrogen only stores energy. Furthermore, its not necessarily clear that battery technology won't improve, and it may also be more advantageous to change our driving habits to support the use of electric vehicles.

 

[mgb_phys]

Without getting energy from hydrogen, fuel cell vehicles and etc are basically overly complicated batteries.

It makes sense for transferring large amounts of energy large distancess
If you have geothermal (iceland) or solar (n. africa) it is easier to make hydrogren and ship that to LA than run a power line or ship recharged nicad batteries.
The infrastructure is more easily modified, lots of natural gas and LPG technology.

It's not clear if hydrogen powered cars make more sense than electric. Power densities are similair and both need to improve if they are going to be more than around-town subcompacts. Hydrogen fits the gas-station fillup / oil company model but electric let's you recharge at home overnight.

 

[WarPhalange]

Also, even using oil or coal power plants to get electricity and store it in hydrogen is more efficient than using gasoline automobiles, because it's easier to stay efficient on a large-scale than to have every driver take necessary steps to make their car more efficient.

 

[russ_watters]

However, batteries currently are not very good at storing energy and electric vehicle cannot travel distances comparable to gas powered vehicles.

The way you worded it, it isn't true. Batteries store and recover energy at an efficiency of better than 90%. Fuel cells, depending on how the hydrogen is produced, only around 50%.

Using hydrogen as an intermediary for energy storage could allow them to act as a better "battery" with a greater range than electric cars.

Now the way that is worded, it could be true. Reglar batteries have some drawbacks, like weight, cost, nasty materials, and charging time. Fuel cells might be better in those respects.

 

[russ_watters]

Also, even using oil or coal power plants to get electricity and store it in hydrogen is more efficient than using gasoline automobiles, because it's easier to stay efficient on a large-scale than to have every driver take necessary steps to make their car more efficient.

That is true of battery-powered cars, but not true of fuel cell cars. Assuming probably too high estimates of 70% efficiency for both the electrolysis and the fuel cell, 60% efficiency for the power plant, and 90% for the motor, that gives you about 27% efficiency. A battery powered car loses about 7% in the power lines and the batteries, charger, and motors are all better than 90% efficiency. That gives a conservatively low estimate of 40% overall efficiency.

 

[Coin]

The point of hydrogen in the "hydrogen economy" is as a common medium for energy transport and storage. If you didn't understand this already then you don't understand the "hydrogen economy" enough to debunk it...

That is true of battery-powered cars, but not true of fuel cell cars. Assuming probably too high estimates of 70% efficiency for both the electrolysis and the fuel cell, 60% efficiency for the power plant, and 90% for the motor, that gives you about 27% efficiency. A battery powered car loses about 7% in the power lines and the batteries, charger, and motors are all better than 90% efficiency. That gives a conservatively low estimate of 40% overall efficiency.

That 7% sounds very optimistic, are you assuming the power was generated locally? What if the power was generated a long way away and was transported over long distance power lines, or was generated at some point in the past and stored? One assumes hydrogen, if it's treated like normal substance fuels, would be used this way, I don't know whether electricity can be transported and stored as easily or not...

 

[russ_watters]

That 7% sounds very optimistic, are you assuming the power was generated locally? What if the power was generated a long way away and was transported over long distance power lines, or was generated at some point in the past and stored? One assumes hydrogen, if it's treated like normal substance fuels, would be used this way, I don't know whether electricity can be transported and stored as easily or not...

I'm talking about the transmission lines themselves and it is about 7%:
http://en.wikipedia.org/wiki/Electric_power_transmission#Losses

And I factored that into the batteries but not the hydrogen because I assumed the hydrogen would be produced at the power plant. Electric cars will almost certainly be recharged at home.

 

[Topher925]

estimates of 70% efficiency for both the electrolysis and the fuel cell

Didn't MIT just have a "break through" by using a new catalyst and cathode to have electrolysis operate at efficiencies of around 90%? Current PEM fuel cells operate around 50% efficiency although I think Honda's (FCX) is approaching 60%. I can see this number being 70% in ten years. And although it isn't hear yet solar thermolysis shows promise of some extremely high efficiencies.

One overlooked aspect of batteries is their disposal. They don't last forever, and most high capacity batts don't last longer than 500 cycles. Also you have to consider that all batteries self discharge. BTW, if you compare the Honda FCX to the Tesla Roadster, they both have about the same max distance. But the FCX does cost a hell of a lot more.

 

[mheslep]

Didn't MIT just have a "break through" by using a new catalyst and cathode to have electrolysis operate at efficiencies of around 90%? ...

Yes. Uses common materials and is highly efficient. Should be, finally, a practical and economic way to use electrical means to store energy in chemical form (H2).
http://www.sciencemag.org/cgi/content/full/1162018/DC2
http://www.technologyreview.com/article/21179/page4/

 

[mheslep]

...and most high capacity batts don't last longer than 500 cycles. ...

That depends a great deal on the level of discharge, the top off charge, and temperature. If one mediates all these, which the Tesla roadster does and your laptop does not, the battery life will be greatly extended.

 

[Topher925]

...and your laptop does not...

My laptop has hardware designed to maximize battery fitness, doesn't yours.

Anyway, LiFe(P) has done a lot for battery durability but that comes at a pretty big hit of specific energy which in the long run kills efficiency. The lightest batts, Lipoly not Lion or LiFe(P), have very limited life spans even when properly used. I've never gotten more than 200 cycles out of my Lipos for my RC heli's while I could run NiMH for over a thousand.

 

[mheslep]

My laptop has hardware designed to maximize battery fitness, doesn't yours.

All the mfn's design to maximize operation time per single charge, as that's what is advertised and reviewed. Their first priority is to give you non-stop operation on that coast-to-coast air travel, lifecycle is an afterthought. Obviously laptops have no temperature stabilization on the battery. The Chevy Volt for instance will hold in reserve some percentage (10%?) of the battery charge, and they never top off the charge either, neither of which is provided by your laptop. Generally laptop charge circuitry is only tasked with limiting charge rates and Li ion safety issues.

 

[mheslep]

Of the several problems with an H2 economy by far the most intractable to my mind is the transportation and/or storage of H2 as a fuel. With some of the more recent developments I 've been musing that perhaps a solar/wind/grid based local roadside H2 station might start to make sense. Details below. First the problems w/ H2 up until now.

This chart lays it out nicely:
http://www.physorg.com/news85074285.html
To run an H2/fuel cell car, starting with 100kWh electric power one ends up w/ only 23kWh of tractive power delivered by the vehicle:
AC-DC: 95%
Electrolysis: 75%
Compression: 90%
Transport/transfer: 80%
Fuel Cell: 50%
Electric drive train: 90%

So far the logistics of providing roadside fueling of an H2 car has meant:
stage 1: a large electrolysis center somewhere w/ with a massive megawatt connection to the grid to make the H2 (or reforming from natural gas but let's drop the fossile source for this line). Then compression, storage, and transport to local road side stations. Note that it takes 15-20 tankers of compressed 3000 to 5000 psi H2 to deliver the energy equivalent of one gasoline tanker, and existing pipelines won't handle H2 at all.
stage 2: road side H2 station, storage again until delivered to the vehicle.

Now some musing on how this might be done differently, given recent developments:
-Nocera's efficient and cheap electrolysis breakthrough (linked above)
-Improving solar PV efficiency and technology, especially concentrated PV
-Electric transmission becoming more expensive and difficult.
These three lead me to the concept of a completely local, self sufficient H2 roadside station. Given: the average existing US gas station pumps 2000 gal/day. At 136Mjoule/gal-gasoline, that's 272000 Mjoule/day, or 76000 kW-hrs/day. Assuming the new H2/fuel cell cars are 3X more efficient than existing ICE cars, we need only a third, or 25300 kW-hrs/day of equivalent electrical energy.

Now, efficiencies. We need no AC/DC conversion. After 90% efficient Nocera on-site electrolysis and 90% efficient on-site compression we need 31234 kW-hrs/day. To get that from the grid means a 1.3MW average electric service at all 200,000 US filling stations, hard for both the local filling stations and the grid at large to accommodate, so let's try onsite generation.

Solar is a good fit here in a sunny climate because we're along side the highway, and because we don't care about variability. One just buffers enough H2 to stay ahead of demand. At a year round average of http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/" , have that kind of land to spare.

Cost? Solarbuzz says http://www.solarbuzz.com/statsCosts.htm" claims they'll be doing 7 cents/kWh in a couple years. :uhh:

 

[Ygggdrasil]

Today's New York Times (http://www.nytimes.com/2008/08/27/business/27grid.html) had an interesting article about wind power that goes along the lines of mheslep's comment. Many wind farms have to shut down when the wind is too strong because they're generating too much energy for the power grid. This highlights a major problem with two of the primary sources of renewable energy (wind and solar): their outputs are highly variable and may not match peak times for energy demand. This is where hydrogen, as a means to store this energy that would otherwise go unharvested, comes in. This hydrogen could either be used as a buffer for days where the solar/wind generators can't meet demand and/or could be transported away for use as fuel.

Of course, there are still problems with transport and storage, but it seems like generating hydrogen may not be so much of an issue now. Personally, I think storing hydrogen in the solid state (e.g. as metal hydrides or adsorbed in nanomaterials) shows the most promise, but these solutions are still in the R&D stage.

 

[mheslep]

Yes efficient production of H2 would help the variability of renewable power like solar and wind in many applications but it doesn't by itself enable a nationwide solution. As that NYT piece shows, the power has to be eventually shipped over transmission lines from the wind belt or the solar belt to the demand areas - except for onsite bufferable problems like a fueling station.

 

[vanesch]

Given: the average existing US gas station pumps 2000 gal/day.

You mean your average highway station only has about 100-200 customers a day ?

 

[Topher925]

Non-baseload power generation is the biggest flaw with alternative power sources. I believe it was once estimated that wind power could never account for more than 7% of total power on the grid because of variability. The current bandaid for this is the use of flywheels, for example Beacon Power's flywheels: http://www.reuters.com/article/pressRelease/idUS174731+19-May-2008+BW20080519

I believe the only answer in the end will by an H2 economy.

mheslep, that article makes a strong argument but it includes a lot of unnecessary processes. H2 would obviously be created directly at the plant and then shipped, in which case the fast majority of the losses would be just to do to the transportation vehicle itself which given a few years of R&D will become pretty close to current electric vehicle efficiencies.

 

[mheslep]

You mean your average highway station only has about 100-200 customers a day ?

That sound reasonable, I actually pumped gas as a kid, but I don't know. I used US daily 390 million gallons of gasoline / 200000 US gas stations.
www.eia.doe.gov/basics/quickoil.html

 

[mheslep]

Non-baseload power generation is the biggest flaw with alternative power sources. I believe it was once estimated that wind power could never account for more than 7% of total power on the grid because of variability. The current bandaid for this is the use of flywheels, for example Beacon Power's flywheels: http://www.reuters.com/article/pressRelease/idUS174731+19-May-2008+BW20080519

20%.
www.20percentwind.org

No doubt there are many storage methods possible. Pump storage and hydro has been the traditional load levelling go-to for the industry, geography/terrain permitting. At the moment Compressed Air seems to be the darling of DoE (one plant in operation), perhaps electrolysis-H2-gas turbine at NREL (prototype).
http://www.eere.energy.gov/de/compressed_air.html"

 

[vanesch]

That sound reasonable, I actually pumped gas as a kid, but I don't know. I used US daily 390 million gallons of gasoline / 200000 US gas stations.
www.eia.doe.gov/basics/quickoil.html

It's funny. When I get to a highway station, I'm usually waiting in line with say, 1 or 2 customers before me, there are usually 6 - 10 lines, and it takes me about 5-10 min waiting time before it's my turn, so I'd say that we get a customer flow of about 5-10 customers/ 5 minutes, or 60-120 customer *an hour*. Now, I realize that this is not the same at 18 hr than at 2 am, but nevertheless...

 

[vanesch]

At the moment Compressed Air seems to be the darling of DoE (one plant in operation),

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

 

[Topher925]

As far as I know, they just pump air into caves which can behave as a huge heat sink. Yes it is a stupid inefficient way of storing power but you can store a LOT of it on the cheap. Its very unpractical to store, let's say, 20MWhs with some batteries.

 

[Ygggdrasil]

One idea that's been floated is around (vehicle-to-grid technology) is to use batteries in plug-in hybrids and other electric vehicles to act as a buffer by storing energy when demand is low and providing energy during peak demands. Of course, this won't work until electric cars become widespread, but it's an interesting idea.

http://www.sciencedaily.com/releases/2007/12/071203133532.htm

 

[mheslep]

It's funny. When I get to a highway station, I'm usually waiting in line with say, 1 or 2 customers before me, there are usually 6 - 10 lines, and it takes me about 5-10 min waiting time before it's my turn, so I'd say that we get a customer flow of about 5-10 customers/ 5 minutes, or 60-120 customer *an hour*. Now, I realize that this is not the same at 18 hr than at 2 am, but nevertheless...

Wow. Where, France? I've rarely (70's embargo maybe) seen that kind of load anywhere in the US. I suppose the 2000g/day average is quite light for those interstate highway ten pump stations and heavy for the mom/pop two pump stations.

 

[mheslep]

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

Yes that's the criticism. I wouldn't know the amount heat transfer to the surrounding rock over the time span - for wind it would be hours to a couple of days. I suppose the geology must be chosen carefully. The couple of existing plants use natural formations, perhaps modified.

 

[mheslep]

One idea that's been floated is around (vehicle-to-grid technology) is to use batteries in plug-in hybrids and other electric vehicles to act as a buffer by storing energy when demand is low and providing energy during peak demands. Of course, this won't work until electric cars become widespread, but it's an interesting idea.

http://www.sciencedaily.com/releases/2007/12/071203133532.htm

Some good work done on V2G by NREL as part of their wind program.
Poster:
www.nrel.gov/analysis/winds/pdfs/wind_phev_poster.pdf[/URL]
Paper:
[PLAIN]http://www.eere.energy.gov/afdc/pdfs/39729.pdf"
The authors show that with a large US fleet of PHEVs by 2020, the reserve capacity could ramp up to 250GW (25% of todays total grid capacity). That makes assumptions of 50% plug-in time, very capable PHEVs (60's), etc. (Figure 5).

http://spectrum.ieee.org/oct07/5630"

 

[russ_watters]

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

I don't see it as being any worse than pumped-water storage. The point isn't in the efficiency, it is in finding a way to store a vast quantity of energy. Since at night you have a vast quantity of wasted capacity, you may as well use some of it to do some sort of storage.

France is all nuclear - what do they do at night?

 

[mheslep]

I think Vanesch was pointing out that possibility of energy loss in compressed storage. The compressed, necessarily hot, air could cool in fixed volume storage to the point where significant energy is lost (PV=NRT). The worse that could happen w/ pumped storage is evaporation?

 

[mheslep]

FYI
http://news.cnet.com/8301-11128_3-10026958-54.html?tag=mncol;title"

A New Jersey company said on Tuesday it will invest $20 million over three years to develop an underground compressed-air storage system for wind turbines and other power sources, a sign of growing confidence in the technology.

Energy Storage and Power is a joint ventured formed by energy developer PSEG Global and Michael Nakhamkin, who designed the only compressed air-storage facility in the U.S.

With Compressed Air Energy Storage (CAES), air is pumped into underground formations, such as depleted natural gas wells or salt caverns, using a natural gas-powered machine. The pressured air is released later to drive a turbine to make electricity...

Battery makers also want to play at the grid MW level. A123 reportedly is the battery vendor for Chevy's PHEV.
http://news.cnet.com/8301-11128_3-9976421-54.html"

...Fulop said that batteries can meet utility needs for grid stabilization, where a large amount of electricity is needed for a short amount of time.

"The technology can do it. Now it's a question of building the systems," he said. "Megawatt-level systems are all about systems integration."

In addition to batteries, utility-ready energy storage systems require electronics and thermal management systems, he said.

though at $500-1000 / kWh of Li ion I don't see how batteries compete. Perhaps they're cheaper at that scale and when mass is not important.

 

[russ_watters]

I think Vanesch was pointing out that possibility of energy loss in compressed storage. The compressed, necessarily hot, air could cool in fixed volume storage to the point where significant energy is lost (PV=NRT). The worse that could happen w/ pumped storage is evaporation?

No, the worst that happens with pumped-storage is the efficiency of the pump is only 60%, which is about the same as the efficiency of a good compressor.

Compressor efficiency ratings are almost always at room temperature output, meaning they take into account the heat generated in the compression and lost in the storage.

Heck, what do you think happens to water when you run it through a pump...?

 

[mheslep]

No, the worst that happens with pumped-storage is the efficiency of the pump is only 60%, which is about the same as the efficiency of a good compressor.

Compressor efficiency ratings are almost always at room temperature output, meaning they take into account the heat generated in the compression and lost in the storage.

Heck, what do you think happens to water when you run it through a pump...?

Yes I understand there are necessarily losses in the act of storage and again on the recovery. I meant that while the storage system is loaded but idle, the compressed air system is still bleeding off energy as the cavern cools. Not so with elevated water.

 

[vanesch]

France is all nuclear - what do they do at night?

Well, you might be surprised, but most french nuclear power stations can follow load, they are not only working in baseload. They can ramp at 5% of nominal power per minute, as long as they stay between 30% and 100% of nominal capacity (below 30%, there are problems with Xe poisoning). They can even handle up to 10% "immediate" load change from their working point.

 

[russ_watters]

Yes I understand there are necessarily losses in the act of storage and again on the recovery. I meant that while the storage system is loaded but idle, the compressed air system is still bleeding off energy as the cavern cools. Not so with elevated water.

We're talking past each other. What I'm saying is that it is generally assumed that that heat is lost in a compressed-air system. If the stored air is "still bleeding off energy as the cavern cools" then that means it hasn't lost all that heat - that's a bonus, not a penalty.

 

[mheslep]

We're talking past each other. What I'm saying is that it is generally assumed that that heat is lost in a compressed-air system. If the stored air is "still bleeding off energy as the cavern cools" then that means it hasn't lost all that heat - that's a bonus, not a penalty.

Ah, thanks, I see your point.