This is where renewables and hydrogen fit in

[Shannow]

Wrote a discussion document a few years ago on using off peak electricity to make hydrogen, to augment natural gas, which could be used "later", like a pumped storage hydro, and received a certain amount of ridicule...

http://www.iea-coal.org.uk/site/2010/new...-for-first-time

This makes sense...you can use NG with up to 10% hydrogen without mods. Excess electricity, stored in the "capacitor" of thousands of kilometers of gas mains.

 

[JHZR2]

Yes but you still have the inefficiency of producing hydrogen. High temperature SOFC electrolysis may be a beneficial approach, with the SOFC using heat from the electric generation and then somehow recuperating it (oxygen enhancement to the fired plant?).

Regenerable fuel cells are a decent system if you can deal with the H2.

 

[A_Harman]

How efficient is the overall process? Water is a highly stable molecule, and takes a lot of energy to break down into H and O. When the Hydrogen is burned, what percentage of the energy is recovered?

 

[CourierDriver]

Hydrogen is very power-full. Had a chemistry mishap with the stuff in class once,,it will blow u into the next world, lol.

 

[Shannow]

Hydrogen generation efficiency is woeful (I've posted that many times)...but if you are getting something "free", somewhere where it "isn't useful" in the typical sense, then it may be useful in the overall system.

The coal that you burn was made from solar energy at some pitiful overall thermal efficiency...to give it any decimals of percent ranking would be generous.

 

[kschachn]

This. I was just going to mention the stability of the water molecule. A very high bond energy. Too bad we can't just run a pipe to the Sun...

Originally Posted By: A_Harman
How efficient is the overall process? Water is a highly stable molecule, and takes a lot of energy to break down into H and O. When the Hydrogen is burned, what percentage of the energy is recovered?

 

[SteveSRT8]

Originally Posted By: Shannow
Hydrogen generation efficiency is woeful (I've posted that many times)...but if you are getting something "free", somewhere where it "isn't useful" in the typical sense, then it may be useful in the overall system.

The coal that you burn was made from solar energy at some pitiful overall thermal efficiency...to give it any decimals of percent ranking would be generous.


haha, excellent point about fossil fuel.

I like H2, once we overcome the storage limitations and the generation of it without excessive power we are home free. Personally I think it makes great sense to use the excess generation capacity when we are off peak to do anything, rather than not using it at all...

 

[NateDN10]

Quote:
The P2G unit receives its power from a nearby wind farm... Once operational, it will use surplus renewable-source electricity to produce about 360 cubic meters of hydrogen per hour. It will therefore harness renewable-source electricity that otherwise could not be fed into the grid. The region’s wind farms already frequently produce more electricity than the local grid can handle.

Sounds smart.

 

[440Magnum]

Originally Posted By: SteveSRT8
Originally Posted By: Shannow
Hydrogen generation efficiency is woeful (I've posted that many times)...but if you are getting something "free", somewhere where it "isn't useful" in the typical sense, then it may be useful in the overall system.

The coal that you burn was made from solar energy at some pitiful overall thermal efficiency...to give it any decimals of percent ranking would be generous.


haha, excellent point about fossil fuel.

I like H2, once we overcome the storage limitations and the generation of it without excessive power we are home free. Personally I think it makes great sense to use the excess generation capacity when we are off peak to do anything, rather than not using it at all...



Depends on WHAT KIND of excess it is. If you have excess wind or solar off-peak, then DANG sure use it. If you have excess steam plant (coal, nuclear, wood-pulp, or natural gas) power off-peak, then under some circumstances it *might* make more sense to let it run through the off-peak hours and incur the inefficiency of storage rather than the inefficiencies of throttling or shut down/bring up of a steam plant. But if you have a gas-turbine peaking plant... SHUT IT DOWN! It costs almost nothing to cold-start gas turbine plants since they can come online in a handful of minutes and throttle well. Same for hydroelectric, there's no sense in generating anything excess over demand with hydro other than off-peak pumped storage (the way Grand Coulee Dam is set up to use its excess generation to lift water into Banks Lake, for example.)

 

[A_Harman]

If you're trying to store the excess energy from a wind farm, would other storage schemes be more efficient?

other ways to store wind-generated electricity:
1. charge banks of large batteries
2. pump water to store at a higher elevation, then use it to drive turbogenerators to recover the energy
3. spin up a building full of flywheel motor-generators
4. compress air into cylinders, then release it to run air motor-driven generators.

I like the water storage method. Gravity is the only truly conservative force.

 

[440Magnum]

Originally Posted By: A_Harman
If you're trying to store the excess energy from a wind farm, would other storage schemes be more efficient?

other ways to store wind-generated electricity:
1. charge banks of large batteries
2. pump water to store at a higher elevation, then use it to drive turbogenerators to recover the energy
3. spin up a building full of flywheel motor-generators
4. compress air into cylinders, then release it to run air motor-driven generators.

I like the water storage method. Gravity is the only truly conservative force.



#4 sucks, unless you can store the compressed air in vacuum insulated dewars so that it doesn't cool. If you compress a fluid, 50% of the energy goes to heating the fluid.If the fluid cools off, the pressure drops as it cools according (more or less) to the ideal gas law, so when you re-expand it half the energy you put in is already gone even before you account for the inefficiency of your air-driven generator.

Not sure what the efficiency of pumping water up and then using it to generate is, but since its (nearly) incompressible its at least much more efficient than compressing air.

Batteries and flywheels have potential to work really well. Flywheels have frictional losses and despite a whole lotta work over the years, there still aren't many long-term flywheel energy storage applications out there, which says something in itself. There ARE commercial uses- like flywheel building uninturrptible power supplies that can carry the electrical load of a building until the diesel or natural gas generator can start and come on line (Typically less than a minute of storage in the flywheel itself).

 

[JHZR2]

Originally Posted By: A_Harman
If you're trying to store the excess energy from a wind farm, would other storage schemes be more efficient?

other ways to store wind-generated electricity:
1. charge banks of large batteries
2. pump water to store at a higher elevation, then use it to drive turbogenerators to recover the energy
3. spin up a building full of flywheel motor-generators
4. compress air into cylinders, then release it to run air motor-driven generators.

I like the water storage method. Gravity is the only truly conservative force.


1) cycle life, safety, cost
2) yes but need lots of space
3) safety, cost, parasitics
4) yes but safety is more than #2, as likely is acquisition cost.

 

[Shannow]

Originally Posted By: 440Magnum
Depends on WHAT KIND of excess it is. If you have excess wind or solar off-peak, then DANG sure use it. If you have excess steam plant (coal, nuclear, wood-pulp, or natural gas) power off-peak, then under some circumstances it *might* make more sense to let it run through the off-peak hours and incur the inefficiency of storage rather than the inefficiencies of throttling or shut down/bring up of a steam plant. But if you have a gas-turbine peaking plant... SHUT IT DOWN! It costs almost nothing to cold-start gas turbine plants since they can come online in a handful of minutes and throttle well. Same for hydroelectric, there's no sense in generating anything excess over demand with hydro other than off-peak pumped storage (the way Grand Coulee Dam is set up to use its excess generation to lift water into Banks Lake, for example.)


It takes about 100,000 litres of diesel to get a coal plant back running after it's been shut down.

Coal fired operators have to weigh up the money that they lose overnight with the money (and thermal fatigue) to restart them in the morning...overnight in Oz, the wholesale price can reach NEGATIVE $100/kWhr, when the generators typically get 4.5c/kWHr during the day.

economics aren't necessarily efficient.

As an engineer, I'd prefer an efficient grid,but economists chopped nearly 2% off my state efficiency with their "economic" efficiencies.

 

[Tempest]

Quote:
overnight in Oz, the wholesale price can reach NEGATIVE $100/kWhr, when the generators typically get 4.5c/kWHr during the day.

I take it that the wind farms get first dibs at supplying the power?

 

[Shannow]

Originally Posted By: Tempest
Quote:
overnight in Oz, the wholesale price can reach NEGATIVE $100/kWhr, when the generators typically get 4.5c/kWHr during the day.

I take it that the wind farms get first dibs at supplying the power?


No tempest, we've been through this before...coal fired thermal efficiency dropped with competition, when scheduling was no longer made on efficiency grounds.

 

[Tempest]

Originally Posted By: Shannow

No tempest, we've been through this before...coal fired thermal efficiency dropped with competition, when scheduling was no longer made on efficiency grounds.


Seems that wind power is lowering costs and causing more negative price conditions:
https://theconversation.com/power-of-the-wind-how-renewables-are-lowering-sa-electricity-bills-9945

 

[Shannow]

You could also say that a 12% reduction in the peak load since 2008 might have something to do with lower prices, but that wouldn't suit your agenda.

 

[JHZR2]

Originally Posted By: Shannow
Originally Posted By: 440Magnum
Depends on WHAT KIND of excess it is. If you have excess wind or solar off-peak, then DANG sure use it. If you have excess steam plant (coal, nuclear, wood-pulp, or natural gas) power off-peak, then under some circumstances it *might* make more sense to let it run through the off-peak hours and incur the inefficiency of storage rather than the inefficiencies of throttling or shut down/bring up of a steam plant. But if you have a gas-turbine peaking plant... SHUT IT DOWN! It costs almost nothing to cold-start gas turbine plants since they can come online in a handful of minutes and throttle well. Same for hydroelectric, there's no sense in generating anything excess over demand with hydro other than off-peak pumped storage (the way Grand Coulee Dam is set up to use its excess generation to lift water into Banks Lake, for example.)


It takes about 100,000 litres of diesel to get a coal plant back running after it's been shut down.

Coal fired operators have to weigh up the money that they lose overnight with the money (and thermal fatigue) to restart them in the morning...overnight in Oz, the wholesale price can reach NEGATIVE $100/kWhr, when the generators typically get 4.5c/kWHr during the day.

economics aren't necessarily efficient.

As an engineer, I'd prefer an efficient grid,but economists chopped nearly 2% off my state efficiency with their "economic" efficiencies.


Glad you provide the technical basis. There's way too many armchair operators that don't understand the realities of operating plants, and would prefer to spout some party line arguments created by screenwriters and lawyers rather than engineers.

 

[grampi]

Why not use only renewable energy sources like wind and solar to produce hydrogen?

 

[PandaBear]

I am not sure about all this. It just make so much more sense and much easier to push the consumption stable and have the application side deal with it.

Making ice at off peak for peak hour cooling system is more efficient, and much cheaper, than hydrogen conversion, battery, or restarting a fire plant.

Pumping water back up the reservoir is also much more efficient.

Having different prices so food processing plant only flash freeze at night is also more efficient.

And we haven't include other chemical processing plants that can run automated at night shift (refining aluminum, etc).

Beside, anything is better than producing hydrogen via electricity. It just leaks so easily that makes it not much of a worthy energy storage, unless you can use it right away in a refinery next door to crack stuff.