Cheap thermodynamic energy storage

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#7

There are examples in Scotland of using wind (generating electricity) to pump water to a high elevation and then using the water for generation of electricity at future points in time as it is released down the hill.

JimA

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Those systems have been around for decades. Original they were powered by excess hydro but now solar and wind are also used.

Helms Pumped Storage is a 1,212 MW hydro power project. It is located on Kings river/basin in California, the US. The project is currently active. It has been developed in single phase. The project construction commenced in 1977 and subsequently entered into commercial operation in 1984.

The power plant operates by moving water between an upper and lower reservoir. When energy demand is high, water is released from the upper reservoir to the generating plant and the water is discharged into the lower reservoir. When demand is low (such as at night), water is pumped into the upper reservoir to be used as stored energy at a later time. This is accomplished by pump-generators which serve a dual role: the pumps can reverse for use as generators. The plant can go from a stand still to operational in eight minutes which allows it to meet peak energy demand. It consumes more electricity pumping than generating electricity but pumping occurs during periods of low demand with unused surplus energy available at lower costs from the electric grid.

https://en.wikipedia.org/wiki/Helms_Pumped_Storage_Plant

Jaak

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#8

If I understand this correctly, it’s similar to a conventional cooling system except that it uses renewable energy as a heat source and nontoxic pressurized liquid carbon dioxide instead of a fluorocarbon, ammonia or other toxic heat exchange fluid. That’s very appealing. I hope they can scale it up.

Wendy

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It is somewhat different than a conventional cooling system which runs constantly (or not at all) and does not store energy for later use. Here is my explanation of how the system works.

The system uses electricity from renewable energy to drive the compressors to pressurize the gaseous CO2 while water is cooling the CO2. The pressurized and cooled CO2 reaches liquid form is stored. The cooling water has become heated water and is stored.

When electricity is needed, the stored heated water is used to heat and vaporize the liquid CO2 and pass the gaseous CO2 through a turbine generator to produce electricity. The turbine generator exhaust is CO2 gas back into its initial conditions in the dome.

The CO2 ready to go through the cycle again.

Jaak

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#9

I am sure that I missed something but it sounded like a perpetual motion machine.

I’m sure it’s not a perpetual motion machine. The quick description glossed over the storing heat energy part of the process. I suspect that is where the majority of the energy losses are. And the compression and evaporation of the heat transfer medium (CO2 in this case) are giong to have losses as well.

The point is that it is a way to use excess electricity to store energy, which can be released at a later time when there is a deficit of electric production. Smoothing out solar and wind generation would be a good use for this technology.

Of course, it remains to be seen how big the losses are, and if the process can scale up to utility size. Costs would be an issue as well - both initial construction and ongoing maintenance. With a pressurized gas flowing around a system that is at least partially mechanical, it will require maintenance, and there will be down times. But that’s the same as any electric production methods.

The typical solution to these issues is almost certainly going to be redundancy. You don’t want just a couple of exceedingly large storage units. You want multiple moderate sized units with sufficient overcapacity in total that a unit can go off line periodically for maintenance and repair without impacting the entire grid.

–Peter

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#10

The first word in the title of this thread is Cheap. Where is the proof of this? I don’t see it.

The following article says this Energy Dome technology has a round-trip efficiency of 75%.

https://www.canarymedia.com/articles/long-duration-energy-st…

This is a little worse than other storage technologies. The Energy Information Administration says battery storage is about 82% efficient, and pumped (hydro) storage is 79%.

https://www.eia.gov/todayinenergy/detail.php?id=46756

In other words, for this Energy Dome system, if you use 100 kilowatt-hours of electricity to compress the CO2, you only get 75 kilowatt-hours out when the system is producing power.

  • Pete
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#11

The first word in the title of this thread is Cheap. Where is the proof of this? I don’t see it.

The following article says this Energy Dome technology has a round-trip efficiency of 75%.

This is a little worse than other storage technologies. The Energy Information Administration says battery storage is about 82% efficient, and pumped (hydro) storage is 79%.

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The Dome has not been verified as being cheap and 75% efficiency because it has never been built. The first Dome is now being built and that will document cost and efficiency.

The Dome should be cheap compare to other energy storage systems because it does not need exotic metals, materials or equipment. The Dome can provide long duration electricity 4-24 hours. Batteries currently are not capable of long duration discharge. Pumped hydro is more expensive to build because of the need for a large head (height between upper and lower reservoirs). Other long term energy storage systems have efficiencies of 40-50%.

My engineering opinion is that Dome will turn out to be cheaper and more efficient than batteries, pumped hydro storage and other currently known energy storage systems.

Jaak

1 Like
#12

Of course, it remains to be seen how big the losses are, and if the process can scale up to utility size. Costs would be an issue as well - both initial construction and ongoing maintenance. With a pressurized gas flowing around a system that is at least partially mechanical, it will require maintenance, and there will be down times. But that’s the same as any electric production methods.

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I do not see construction as being much of an issue. The Dome does not use any exotic materials or equipment. The Dome does not need to worry about explosions or fires because CO2 is an inert gas.

There is minimal high pressure or high temperature safety issues because CO2 can be liquified at easily reached pressures and temperatures as shown in the CO2 phase diagram in the following link:

https://www.esru.strath.ac.uk//EandE/Web_sites/10-11/ASHP_CO…

Here is some more information on the Dome system.

https://www.canarymedia.com/articles/long-duration-energy-st…

Jaak

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#13

I do not see construction as being much of an issue.

I’m not talking about difficulty of construction, but cost. The cost will need to be less than a comparable size generation facility that could accomplish the same task - namely making electricity available when the intermittent facility is not producing. If the cost were higher, it would make more sense to build a generation facility instead of a storage facility. And the cost is not just construction, but operation.

There is minimal high pressure or high temperature safety issues because CO2 can be liquified at easily reached pressures and temperatures

That would be 1000 PSI at room temperature, or about 300 PSI at 0 degrees F.

I don’t know about you, but 1000 PSI in large tanks strikes me as high pressure. High pressures are always safety issues. Probably well understood safety issues, but issues nonetheless.

Dome does not need to worry about explosions or fires because CO2 is an inert gas.

Remind me not to put you in charge of safety programs.

1000 PSI tanks are always an explosion hazard. They need regular inspections to check for corrosion or cracking, as do the high pressure lines connected to the tanks.

Even the 300 PSI of cold storage is an explosion hazard. Plus it needs constant temperature and pressure monitoring, because if the temperature rises the pressure will also rise and could explode any components in the system not designed to handle the higher pressures of warmer CO2.

As to being an inert gas, I have to concede that based on the typical definition of inert. But inert does not mean without hazards. You might check that out with the guys in the room with a leaking CO2 line. Wait, you can’t do that because they are dead from CO2 inhalation.

—Peter

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#14

Interesting idea.

My personal favorite “new” energy storage solution is the “energy vault”

https://www.energyvault.com/

Basically, picture a parking garage with 30 ton bricks. When solar/wind power is high, a series of elevators loads the bricks onto the top floors. When more power is needed, the bricks drive mechanical generators as they return to the lower floors.

I don’t know the efficiency, but conceptually I like the simplicity of it. It can be built anywhere. It doesn’t need water or gas. I don’t think it needs exotic materials or particularly expensive machines…

Like the CO2 storage, time will tell what the economics really are. I suspect we need to get many years down the road before we will really know what works and what doesn’t.

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#15

1000 PSI tanks are always an explosion hazard. They need regular inspections to check for corrosion or cracking, as do the high pressure lines connected to the tanks.

Even the 300 PSI of cold storage is an explosion hazard. Plus it needs constant temperature and pressure monitoring, because if the temperature rises the pressure will also rise and could explode any components in the system not designed to handle the higher pressures of warmer CO2.

1000 PSI is high, but it is not crazy high. Lots of routine industrial processes use higher pressures than that.

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#16

1000 PSI is high, but it is not crazy high. Lots of routine industrial processes use higher pressures than that.

Of course. I didn’t mean to imply that these were super high pressures. But neither are they a home air compressor.

I was attempting to refute the claim that there is no explosion hazard because CO2 itself is not explosive.

And, while I don’t know the exact details, we’re also not talking about just a couple of 10 or even 100 gallon tanks of highly pressurized CO2. At industrial scale, there need to be a lot of fairly large tanks held under constant pressure. Those tanks need regular inspections and maintenance. This isn’t a solar farm where the panels just sit there posing little risk.

Of course, all of these risks can be mitigated. There’s nothing terribly new to invent on that front. But the mitigation measures add to the costs of the storage plant. And it is the costs that will eventually decide if this particular storage method is economically viable.

–Peter

#17

Remind me not to put you in charge of safety programs.

1000 PSI tanks are always an explosion hazard. They need regular inspections to check for corrosion or cracking, as do the high pressure lines connected to the tanks.

Even the 300 PSI of cold storage is an explosion hazard. Plus it needs constant temperature and pressure monitoring, because if the temperature rises the pressure will also rise and could explode any components in the system not designed to handle the higher pressures of warmer CO2.

As to being an inert gas, I have to concede that based on the typical definition of inert. But inert does not mean without hazards. You might check that out with the guys in the room with a leaking CO2 line. Wait, you can’t do that because they are dead from CO2 inhalation.

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Your rant shows that you are not a mechanical engineer and, therefore, lack knowledge about industrial facilities using high pressure systems and the associated safety protocol. And by the way, engineers are by definition safety engineers. Every aspect of my engineering of systems and components had to consider safety.

Now to the design of Energy Dome which is needs to meet all industrial safety regulations with pressure vessel, piping, valves, compressors, heat exchangers and other equipment meeting ASME codes and standards. ASME Pressure Vessel Code Section VIII Div. 1 is for 15 psi to 3000 psi designs, Div. 2 is for 3000 psi to 10,000 psi designs and Div. 3 is for greater than 10,000 psi designs. Following ASME codes and standards will prevent explosions.

In your rant, I think you are mixing up industrial facilities with residential facilities. The Energy Dome with probably operate around 500 psia. We have industrial facilities all over the country that regularly use pressure vessels. piping and equipment with pressures of 100 to 10,000 psi and higher. Think about refineries, chemical plants, power plants, natural gas pipelines, aerospace and some many other industrial facilities and commercial facilities.

Many of these facilities use fluids and gases much more hazardous than CO2. CO2 is not corrosive so corrosion is greatly reduced. Thus CO2 is a much easier gas/fluid to design pressure vessels, piping and associated equipment.

Jaak

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#18

you are not a mechanical engineer

Correct. I am an accountant.

Now to the design of Energy Dome which is needs to meet all industrial safety regulations with pressure vessel, piping, valves, compressors, heat exchangers and other equipment meeting ASME codes and standards. ASME Pressure Vessel Code Section VIII Div. 1 is for 15 psi to 3000 psi designs, Div. 2 is for 3000 psi to 10,000 psi designs and Div. 3 is for greater than 10,000 psi designs. Following ASME codes and standards will prevent explosions.

Exactly. I’m not saying anything else.

But I am going to get slightly picky. You said that explosions weren’t a hazard because CO2 is inert. I merely pointed out that explosions ARE a hazard because of the pressures involved, not because this particular gas itself is explosive. And I believe I noted that these aren’t unique issues. Plenty of people know how to deal with high pressures.

I’ll also get slightly picky on that last statement in the quote above. Following codes and standards greatly reduces the chance of an explosion. It doesn’t completely remove the possibility. There’s always a chance that something was overlooked in the creation of codes and standards. And humans are going to be the ones doing the maintenance and repair. Humans make mistakes. So complete safety can never be guaranteed.

Putting my accountant hat on, I see lots of costs here. Like I said in the parts you didn’t quote, none of these are unknown or strange issues. These are mostly problems that have already been solved. (I have enough respect for engineers to know that there are always some problems that need to be solved at any specific site or installation.)

My point is that there are safety issues to be addressed, and that safety costs money. While safety also comes up in proof of concept work, that safety is generally underwritten as a cost of the research. And the visionaries who come up with these ideas often overlook costs that aren’t a direct part of their innovation.

This whole idea is quite interesting, but I started my participation in the thread by wondering how well this will scale up, and if the design will be cost effective at the necessary scale. Somehow that thought got completely side tracked.

–Peter

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#19

But I am going to get slightly picky. You said that explosions weren’t a hazard because CO2 is inert. I merely pointed out that explosions ARE a hazard because of the pressures involved, not because this particular gas itself is explosive. And I believe I noted that these aren’t unique issues. Plenty of people know how to deal with high pressures.

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Your point is silly nitpicking.

Over the last 150 years mechanical engineers have developed codes and standards to prevent high pressure failure of pressure vessels. High pressures in a CO2 pressure vessel would not necessarily result in an explosive. Pressure vessels are normally required to have pressure relief valves set at ensure safety. For example a water heater has a pressure relief valve. How many water heaters have you seen or heard about exploding in your lifetime?

For a pressure vessel to explode, the contents are usually flammable gases/liquids like natural gas, petroleum, hydrogen or any another flammable substance. Some steam boilers can explode if their pressure relief valves are not properly installed or maintained.

Jaak

#20

I’ll also get slightly picky on that last statement in the quote above. Following codes and standards greatly reduces the chance of an explosion. It doesn’t completely remove the possibility. There’s always a chance that something was overlooked in the creation of codes and standards. And humans are going to be the ones doing the maintenance and repair. Humans make mistakes. So complete safety can never be guaranteed.

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Codes and standards have been verified by testing and safety margins are added to the design. If something goes wrong, then it is due to poor operations, maintenance and inspection.

Yes humans make mistakes. We live in a world where we trust engineers to make airplanes, cars, elevators, buildings, power plants, bridges, tunnels, ships, and much more SAFE. I do not understand why do you pick on a non-dangerous facility like Energy Dome as a problem? There are much more thousands of more dangerous facilities that deserve your attention.

For example,

TEPCO engineers designed Fukushima nuclear reactors with diesel generators in the basement and inadequate flood protection from a credible tsunami. Profits over safety was the root cause.

Boeing engineers made design and software mistakes with 737 MAX. Profits over safety was the root cause.

Refinery engineers and operators are responsible for refinery fires and explosions because they run their facilities with corroded piping and equipment that does not meet codes and standards. Profits over safety was the root cause.

Engineers and operators of natural gas and oil pipelines are responsible for explosions and fires due to corrosion and overpressure situations that do not meet codes and standards. Profits over safety was the root cause.

Jaak

#21

My point is that there are safety issues to be addressed, and that safety costs money. While safety also comes up in proof of concept work, that safety is generally underwritten as a cost of the research. And the visionaries who come up with these ideas often overlook costs that aren’t a direct part of their innovation.

This whole idea is quite interesting, but I started my participation in the thread by wondering how well this will scale up, and if the design will be cost effective at the necessary scale. Somehow that thought got completely side tracked.

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I think you missed the fact the Energy Dome is building a demonstration facility which will flush out design, safety, cost sand schedule issues. That is normal practice for most honest engineering and construction projects.

The visionaries of Energy Dome are the ones involved with the design and construction of the demonstration facility. Engineers do know how to estimate the design, safety, cost and schedule of the Energy Dome at larger scales.

Jaak

#22

Codes and standards have been verified by testing and safety margins are added to the design. If something goes wrong, then it is due to poor operations, maintenance and inspection.

Once again, that’s pretty much what I said. Why do you keep at this?

My point is, and remains, we need to know the costs of this project before I can get too excited. And before that, we need to know if it’s actually feasible - that it actually works - at utility scale rather than a desktop model. Until we know the costs, we don’t know that it’s cheap, as claimed in the thread title.

–Peter

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#23

My point is, and remains, we need to know the costs of this project before I can get too excited. And before that, we need to know if it’s actually feasible - that it actually works - at utility scale rather than a desktop model. Until we know the costs, we don’t know that it’s cheap, as claimed in the thread title.

–Peter

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I already responded to the costs of the project and why I think it will be cheap? Why do you keep asking the same questions?

Jaak

#24

I already responded to the costs of the project and why I think it will be cheap?

I see it.

The post where you said it has not been verified to be cheap, that testing is under way, and that being cheap is just your opinion.

OK, then.

My opinion is that it will turn out not to be cheap, or even cheaper than other storage methods already in use.

Let’s check back in ten years.

–Peter

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#25

My opinion is that it will turn out not to be cheap, or even cheaper than other storage methods already in use.

Let’s check back in ten years.

–Peter

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My engineering based estimate is 100 times more accurate than your accountant based estimate.

I really do not understand why an accountant would argue about mechanical engineering projects with a mechanical engineering manager who has over 30 years of experience in the design, licensing, safety analysis, cost estimates, procurement, construction and operation of many projects at Bechtel.

You are way out of your area of expertise.

Jaak

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#26

You are way out of your area of expertise.

You do know that costs are exactly what accountants deal with every day.

—Peter

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