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Old 06-05-2019, 10:24 AM
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Solving the flaws with wind and solar, i.e. energy storage systems. Why not hydrogen?


So, been doing a lot of thinking about green energy systems, especially as they have been discussed in multiple threads I've participated in lately. The obvious solution, to me, is nuclear to basically fill in the gaps in wind and solar, since we are pretty much tapped out on hydro and geothermal, at least in the US. This doesn't seem likely though, so need to look at alternatives. Batteries have been proposed, and there are several scaled up test beds for this concept being tried out. Batteries, however, have some issues and gaps of their own, one of which is that they are expensive, but another is that they aren't particularly good at longer term storage. Pumped hydro has also been proposed, but not going to get into that one here. Regardless, what we need is something that can give the grid a good baseline AND can ramp up when the sun isn't out or the winds aren't productive. Currently, we overproduce solar in some states at certain times, meaning that if neighboring states don't buy the energy it's basically dumped. It can't be stored. So, that's actually idea for an energy storage concept...we NEED to overproduce energy at the time when it's optimal so we can store it for when it's not.

Well, why not use that to produce hydrogen? We know how to use energy to produce the stuff, after all. There are actually several different ways to do this, in fact. Storage can be a bitch, but it's do-able...we do it already, after all. I'm fairly sure we could figure out large scale storage and containment systems that would cost a fraction of what batteries would cost...in fact, the production and storage would cost a fraction of what a battery system would cost and give us a ton more utility, as from an energy density perspective hydrogen is much better. We could use the existing pipeline systems that move around natural gas or fossil fuels underground to ship it hither and yon as well (might take some retrofitting of pipe sleeves or such, but that's do-able). And we could, I think, use existing power plants to use the stuff, at least I THINK we could...it's a similar principle after all. Or, I suppose, we could use fuel cell technology, though I think that would increase the costs.

This seems an ideal solution...so, what am I missing? I have seen some projects looking into this, but to me this is something we could do fairly quickly. And I don't just mean the US...someone could be doing this right now, today. Overproduction of solar isn't just something happening in California, and no one has a large scale energy storage system able to fill the gaps on a large scale at this time...yet, if we are really going to push solar this is an absolute need, since if you are REALLY going to do away with fossil fuel power you have to have something that works when your green energy systems aren't. Plus, you are going to need to account for if there are extended periods where your green energy system isn't producing what you need (or anything at all) and can maintain the grid during those times.
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Old 06-05-2019, 11:06 AM
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Hydrogen is fairly bulky unless it is liquid, and it needs to be super-cooled in order to liquefy it. So perhaps putting a new pipeline in is not as cheap or straightforward as you might think. It is also explosive, much more than oil.

I don't know if the same people who panic over Three Mile Island are also going to panic if the Hindenberg is recreated in their neighborhood.

Yes, it's an option, but I would need to see a working prototype before I hail it as the solution to all our problems.

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Last edited by Shodan; 06-05-2019 at 11:06 AM.
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Old 06-05-2019, 11:11 AM
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I don't know if the same people who panic over Three Mile Island are also going to panic if the Hindenberg is recreated in their neighborhood.
Speaking just for myself as a single data point. I'm all for a hydrogen storage facility over a nuclear facility. Either one can get kind of explodey if things are grossly mishandled but at least the hydrogen cleanup is easier.
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Old 06-05-2019, 11:23 AM
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Do you know why battery powered electric cars are what is surging and not fuel cell cars?

Yes, the lack of filling stations vs. the pre-existence of our electrical grid is part of it, but another is that hydrogen as energy storage just isn't a miracle solution.

The biggest problem, compared to batteries, is the necessary compression or refrigeration, which represents a significant energy loss.
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Old 06-05-2019, 11:34 AM
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good topic

How much new infrastructure would be required? Can the hydrogen generated via wind/solar really be sent through existing natural gas or oil pipelines, or would new pipelines be needed? Or would it make more sense to transport in trucks?
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Old 06-05-2019, 11:54 AM
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For what it's worth, nuclear can't really "fill in the gaps" in wind and solar. It takes hours to ramp a nuclear plant up or down, and wind and solar both vary on much shorter timescales than that (coal, incidentally, has the same problem). One big advantage to natural gas turbines is that they can respond very quickly, and hence take care of most of the response.

As to hydrogen, in addition to all of the other problems, it just isn't very efficient. Electrolysis of water is only about 75% efficient, and then you're going to have more losses when you burn the hydrogen. If cheap power were unlimited, that might still be good enough, but it's not.
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Old 06-05-2019, 12:02 PM
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Do you know why battery powered electric cars are what is surging and not fuel cell cars?

Yes, the lack of filling stations vs. the pre-existence of our electrical grid is part of it, but another is that hydrogen as energy storage just isn't a miracle solution.

The biggest problem, compared to batteries, is the necessary compression or refrigeration, which represents a significant energy loss.
Not to mention, the conversion of hydrogen back into electrical or mechanical energy has pretty significant losses as well (I think ~40-50% losses for fuel cells in practice, and even higher for combustion engines).

Basically, you'll lose 20-30% of the input energy during the production of your hydrogen (assuming you are doing electrolysis of water), then use a fair amount of energy for compressing it for storage or transportation, then lose another 40-50%+ of what's left when using it. So at best you might come out with nearly half of your input energy, and more likely you're only getting like 25% of your input energy by the time you've converted that hydrogen back to electricity. Low efficiency wouldn't necessarily be a killer if all of these steps were dirt cheap, but they aren't.

Hydrogen is also more difficult and expensive to store and transmit than, say, natural gas due to hydrogen making metals brittle. Liquid hydrogen also isn't as energy dense as gasoline or diesel.

As mediocre as battery storage is currently, I think it still compares favourably compared to most other options on a cost and efficiency basis. At the end of the day, if hydrogen had substantially lower life-cycle costs than batteries, you'd see a lot more development on it.
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Old 06-05-2019, 01:11 PM
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Can some hydrogen safely be mixed with natural gas in small percentages or even dissolved in gasoline or oil? That would allow use of existing pipelines. Perhaps a gas turbine plant can be tuned to run on either fuel or a mix of the 2, burning extra hydrogen produced from times when excess power is produced.
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Old 06-05-2019, 01:20 PM
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XT, why is pumped hydro being left out of the discussion? Any type of energy storage will involve losses, but pumped hydro should be much safer and cost less than other methods to implement.

Last edited by TriPolar; 06-05-2019 at 01:20 PM.
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Old 06-05-2019, 01:40 PM
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XT, why is pumped hydro being left out of the discussion? Any type of energy storage will involve losses, but pumped hydro should be much safer and cost less than other methods to implement.
I think it deserves a thread just like this one to discuss and I didn't want to overly complicate this one. I wanted folks thoughts on hydrogen as an alternative, and didn't want a ton of digression. I debated even bringing up batteries for that matter, but I needed something to contrast and give some context to what I was asking. Large scale batteries also deserve their own thread like this one, IMHO.
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Old 06-05-2019, 01:42 PM
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XT, why is pumped hydro being left out of the discussion? Any type of energy storage will involve losses, but pumped hydro should be much safer and cost less than other methods to implement.
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The main problem with gravitational storage is that it is incredibly weak compared to chemical, compressed air, or flywheel techniques (see the post on home energy storage options). For example, to get the amount of energy stored in a single AA battery, we would have to lift 100 kg (220 lb) 10 m (33 ft) to match it. To match the energy contained in a gallon of gasoline, we would have to lift 13 tons of water (3500 gallons) one kilometer high (3,280 feet). It is clear that the energy density of gravitational storage is severely disadvantaged.
Cite. So you need a really big - really, really big - reservoir.

Again, not out of the question, but not a magic bullet either.

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Old 06-05-2019, 01:54 PM
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Cite. So you need a really big - really, really big - reservoir.

Again, not out of the question, but not a magic bullet either.

Regards,
Shodan
I'm not seeing the hydrogen looks much better. Why aren't we trying to solve the flaws with pumped-hydro instead of hydrogen? Is there really a hydrogen solution that is more likely, or is it wishful thinking like waiting for fusion to solve the problem?

I don't want to side track the discussion to pumped-hydro, I'm just not seeing great reasons to favor hydrogen over other alternatives as well.

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Old 06-05-2019, 02:15 PM
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I'm not seeing the hydrogen looks much better. Why aren't we trying to solve the flaws with pumped-hydro instead of hydrogen? Is there really a hydrogen solution that is more likely, or is it wishful thinking like waiting for fusion to solve the problem?

I don't want to side track the discussion to pumped-hydro, I'm just not seeing great reasons to favor hydrogen over other alternatives as well.
You guys are free to discuss what you like, but for this thread my preference was to try and focus on hydrogen. Overall, the thrust here, at least from my perspective, is that ALL of these energy storage solutions have issues and lots of engineering that would need to be solved. They each have gaps as well. And none of them really scale that great, though I think hydrogen COULD scale fairly well if the engineering issues could be overcome. I can do threads on specifically batteries and pumped hydro, as well as compressed gas which is another similar possibility for energy storage. If we ever get wide scale energy storage to fill in the gaps with wind and solar, my WAG is it won't be one silver bullet, but a mix of things, at least in a country the size of the US. Some smaller countries with specific advantages to one type of storage or another, just like advantages for one type of green energy verse others can happen, but not in a country the size of the US...at least not that I'm seeing.
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Old 06-05-2019, 02:34 PM
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As to using batteries:
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Just getting to 80 percent of demand reliably with only wind and solar would require either a US-wide high-speed transmission system or 12 hours of electricity storage. A storage system of that size across the US would cost more than $2.5 trillion for a battery system.
https://www.technologyreview.com/s/6...ng-the-energy/

But we want to handle all energy needs not just 80% of demand of the electrical system. And we want to handle seasonal energy needs (remember the polar vortex?)--so instead of 12 hours we need a few weeks.

OP: both the European Union and Asians countries (like Japan and South Korea) are strongly interested in hydrogen--but there seems little interest in the U.S.

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Old 06-05-2019, 02:46 PM
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We need to handle all energy needs, but we don't need to handle it all with wind and solar. Hydro is already a large chunk of our electrical generation, and there's no reason it can't remain so. And even if we end up having to use a small amount of fossil fuels, well, a small amount is better than a large amount.
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Old 06-05-2019, 02:56 PM
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We need to handle all energy needs, but we don't need to handle it all with wind and solar. Hydro is already a large chunk of our electrical generation, and there's no reason it can't remain so. And even if we end up having to use a small amount of fossil fuels, well, a small amount is better than a large amount.
The problem is that nuclear is shrinking, and nuclear is best to maintain a steady base load. I wasn't proposing nuclear to ramp up for short term needs, by the way. Anyway, as nuclear shrinks, something has to fill that gap. Wind and solar are expanding, but their gaps haven't been addressed, so something needs to be there so that when it's not windy or sunny we have the ability to continue to provide energy to people. Also, a lot of solar, specially, is being wasted today, as there is often more energy available in a specific grid at specific times and dates (i.e. a cloudless day in the summer, say) than is needed, while when people really need that energy (say, after 5pm when the sun is lower in the sky and solar is performing less optimally through the night time hours when they are home and using energy more). Hydro is pretty much tapped out...IIRC, it's less than 10% of our total energy generation in the US, and that's basically it...it will never be more than that. It also can vary of course, depending on drought status (or flood for that matter) in some places. So, nuclear is declining, hydro is static, that pretty much means that the 'small amount of fossil fuels' is going to have a bottom limit. 30%? Maybe. Without some sort of energy storage system, that's about as good as it will gets.

To me, if we are going to really make wind and solar work (without replacing our entire grid in the short term) we need some sort of energy storage system. And we probably need it sooner rather than later, as nuclear is going away. In California, for instance, I believe they are in the process of shutting down their last nuclear power plant. That's a huge amount of base load that will be gone, and nothing to replace it 24/7/365 except fossil fuels (either in California, or, more likely, buying it from neighboring states).
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Old 06-05-2019, 03:02 PM
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1. Producing hydrogen from electricity is inefficient - around 70-82%.

2. Storing hydrogen is more difficult than other fuels because of the low density, small molecular size (which means it leaks more easily) and low boiling point (difficult to liquify for transport, unlike propane).

3. Producing electricity from hydrogen is not very efficient either - theoretical maximum of 83%.

That means after you solve the engineering problem of storing and/or transporting hydrogen, and get the most efficient generator and fuel cell possible, you still only get back <68% of what you put in. Compared to >80% for lithium-ion batteries.

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Old 06-05-2019, 03:10 PM
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1. Producing hydrogen from electricity is inefficient - around 70-82%.

2. Storing hydrogen is more difficult than other fuels because of the low density, small molecular size and low boiling point.

3. Producing electricity from hydrogen is not very efficient either - theoretical maximum of 83%.

That means after you solve the engineering problem of storing and/or transporting hydrogen, and get the most efficient generator and fuel cell possible, you still only get back <68% of what you put in. Compared to >80% for lithium-ion batteries.
Yep, definitely. Of course, on the other side, hydrogen can be stored for much longer periods, while lithium-ion batteries don't store energy well. Also, they degrade over time and are very expensive in the scales we are talking about. It's not all about energy efficiency when you are talking about engineering solutions. On the flip side, hydrogen storage and transport is expensive as it's corrosive and needs to be cooled, compressed and liquefied for transport either via pipeline or truck/train.

What we need is a system that can ramp up fairly quickly to fill in the gaps in the spiking parts of our energy requirements and can do this for potentially days or even weeks if needed. If there is a nasty storm, say, or a hurricane or something else that is disrupting sunlight or wind but when things are optimal can basically take in all the excess and currently dumped energy and store it. Every one of the solutions I've seen for this has issues. I don't think energy efficiency is really all that critical considering we are currently just dumping that excess energy that isn't being used, and I think the fact that it can (in theory, if the engineering challenges can be overcome) be used for much longer term and scaled storage seems to mean it has potential, to me at least.
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Old 06-05-2019, 03:11 PM
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P.s. just to reiterate on the storage problem - the Honda Clarity FCX hydrogen powered car has 5000 psi fuel tanks, and the tanks still take up half of the trunk. And the above efficiency calculation doesn't include the extra energy needed to compress the hydrogen up to 5000 psi.
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Old 06-05-2019, 03:16 PM
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P.s. just to reiterate on the storage problem - the Honda Clarity FCX hydrogen powered car has 5000 psi fuel tanks, and the tanks still take up half of the trunk. And the above efficiency calculation doesn't include the extra energy needed to compress the hydrogen up to 5000 psi.
I don't think comparing large scale energy storage systems to those in cars is really that applicable, though several have made this comparison in this thread. The needs, requirements and usages for storage systems in vehicles, IMHO, are very different than the types of loads and requirements for what we are talking about in this thread. In a car, perhaps, those sorts of engineering challenges mean that hydrogen has or will lose the market, but then steam power lost the race wrt cars as well, yet we pretty much ubiquitously use it for power generation in our grid. Making very large storage vaults for hydrogen that can take the caustic effects as well as those levels of pressure aren't nothing, but they aren't exactly cutting edge either wrt what we can do. For a car, yeah...for a power plant or a city? Naw. It could be done. Whether it can be done economically or it's the best solution, well, that's what the thread is discussing.
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Old 06-05-2019, 03:22 PM
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Yep, definitely. Of course, on the other side, hydrogen can be stored for much longer periods, while lithium-ion batteries don't store energy well.
Lithium-ion batteries are actually very good for long term storage, only 2-3% loss per month. But that's irrelevant for this thread, isn't it? Aren't we talking about "demand response" (responding to rapid changes in electricity usage)?

Quote:
Also, they degrade over time and are very expensive in the scales we are talking about.
Fuel cells also degrade over time.

Quote:
It's not all about energy efficiency when you are talking about engineering solutions. On the flip side, hydrogen storage and transport is expensive as it's corrosive and needs to be cooled, compressed and liquefied for transport either via pipeline or truck/train.
Well, if it's a pipeline, it probably doesn't need to be liquefied or even compressed. But it would need to be sealed much better than a natural gas pipeline.

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What we need is a system that can ramp up fairly quickly to fill in the gaps in the spiking parts of our energy requirements and can do this for potentially days or even weeks if needed. If there is a nasty storm, say, or a hurricane or something else that is disrupting sunlight or wind but when things are optimal can basically take in all the excess and currently dumped energy and store it. Every one of the solutions I've seen for this has issues. I don't think energy efficiency is really all that critical considering we are currently just dumping that excess energy that isn't being used, and I think the fact that it can (in theory, if the engineering challenges can be overcome) be used for much longer term and scaled storage seems to mean it has potential, to me at least.
Why would this need a "long term" storage? Those "gaps in the spiking parts of our energy requirements" are on the timescale of seconds to hours, not weeks or months.
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Old 06-05-2019, 03:32 PM
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The needs, requirements and usages for storage systems in vehicles, IMHO, are very different than the types of loads and requirements for what we are talking about in this thread.
OK, then how do you suggest we store the hydrogen, if not in compressed tanks? Cryogenic liquid hydrogen tanks? Uncompressed rubber balloons?

The Tesla battery farm in Australia stores 129 MWh of energy. Hydrogen gas at STP has an energy density of 3.3 Wh/L, so assuming a 70% efficient fuel cell, an equivalent hydrogen energy storage station would need to store 190 million liters of hydrogen at 1 atmosphere.

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Old 06-05-2019, 03:32 PM
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Lithium-ion batteries are actually very good for long term storage, only 2-3% loss per month. But that's irrelevant for this thread, isn't it? Aren't we talking about "demand response" (responding to rapid changes in electricity usage)?
Do you have a cite for that because it's contrary to what I've heard and read. It's not irrelevant to the thread since we are talking about an actual solution here. 'demand response' is only part of the gap and the requirement. Consider...if you actually get rid of all or most of the fossil fuel generation and nuclear finally shuffles off, what do you do if you get a week of rain? Or snow? Or a hurricane? Just tell the folks who need power to suck it up and wait for the sun and wind to come back? We definitely need something that can ramp up, but we also need something that can store at least a weeks worth of energy as well.

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Fuel cells also degrade over time.
Do they? Regardless, I wasn't talking about fuel cells. I was mainly thinking about using hydrogen in power plants in similar ways to how we use natural gas. In fact, I was thinking we might be able to modify those natural gas plants to run on hydrogen instead.

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Well, if it's a pipeline, it probably doesn't need to be liquefied or even compressed. But it would need to be sealed much better than a natural gas pipeline.
I think it would. It would certainly need to be re-sleeved for sure, as hydrogen is more caustic than natural gas. It's definitely one of the challenges. My thought was some sort of large vaults, maybe old salt mines or the like depending on where this would be put in, to store large amounts of hydrogen, as well as shorter term (couple days worth, say) stored at the power plants that would operate at a lower base load continually (much as natural gas does) but could be ramped up for your 'demand response' if needed. If we run into that week or two of bad weather or lower solar or wind production that can't be shifted from another state then you use your large storage vault to ship in more hydrogen as needed. Not simple or particularly cheap, but I think it could work.

Quote:
Why would this need a "long term" storage? Those "gaps in the spiking parts of our energy requirements" are on the timescale of seconds to hours, not weeks or months.
Because shit happens, basically. You DO need days if not weeks in reserve just in case. California is definitely mainly sunny, for instance, but they do get cloudy days, and storms that could vastly reduce solar production, and more wind won't necessarily make up for that. Even today they have issues with this, and they aren't close to a the percentages of wind and solar we are talking about needing, so that needs to be part of the requirements if you are actually going to shut down a large percentage of fossil fuel generation at the same time you are taking out nuclear completely, which California is doing.
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Old 06-05-2019, 03:40 PM
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OK, then how do you suggest we store the hydrogen, if not in compressed tanks? Cryogenic liquid hydrogen tanks? Uncompressed rubber balloons?

The Tesla battery farm in Australia stores 129 MWh of energy. Hydrogen gas at STP has an energy density of 3.3 Wh/L, so assuming a 70% efficient fuel cell, an equivalent hydrogen energy storage station would need to store 190 million liters of hydrogen.
We have a lot larger natural gas storage facilities than 190 million liters. Assuming I'm reading it right, we currently store (in facilities across the US) 2 orders of magnitude more natural gas than that, in fact, and can send more than that through the various pipelines we have for this purpose. Could we do this with Hydrogen? I'm not sure. This is outside of my own expertise, and kind of why I was asking the question I did in the OP. Maybe we can't. I know storing hydrogen is different than natural gas. I know we DO store the stuff though, and use it, so it's technically possible to store it. I know that natural gas can be used to do the job as well, since it is in fact doing it. That 129 MWh of energy from the Tesla plant is impressive...for a battery system. It's nothing to a natural gas plant. Or a nuclear plant. Can hydrogen fill in for those if we produced it with the excess energy we aren't using every good green energy production day? I don't know...it's why I was asking.
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Old 06-05-2019, 03:59 PM
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You guys are free to discuss what you like, but for this thread my preference was to try and focus on hydrogen. Overall, the thrust here, at least from my perspective, is that ALL of these energy storage solutions have issues and lots of engineering that would need to be solved. They each have gaps as well. And none of them really scale that great, though I think hydrogen COULD scale fairly well if the engineering issues could be overcome. I can do threads on specifically batteries and pumped hydro, as well as compressed gas which is another similar possibility for energy storage. If we ever get wide scale energy storage to fill in the gaps with wind and solar, my WAG is it won't be one silver bullet, but a mix of things, at least in a country the size of the US. Some smaller countries with specific advantages to one type of storage or another, just like advantages for one type of green energy verse others can happen, but not in a country the size of the US...at least not that I'm seeing.
I'm just try to compare hydrogen to alternatives. In every case there are problems. The problems with hydrogen may be insurmountable saving an unpredicted technological breakthrough. Storage is problematic for a variety of reasons, and so far improving storage density just increases costs and problems associated with compression and liquification, all additional costs to the parasitic cost of producing the hydrogen.

There are some advantages, production of oxygen, clean burning or chemical conversion, not particularly more dangerous than LNG which it could replace for direct use in aircraft or to produce heat.

Perhaps storage is not that great a problem. If hydrogen can be reasonably transported through existing gas pipelines then it could be used at existing power plants driving turbine generators. For filling in the gaps the pipelines themselves can hold a large volume of gas with power plants and hydrogen production plants buffering the load with smaller lower pressure storage.

All in all I don't see hydrogen being highly rated on the practicality of implementation scale, save for some minor applications.

Last edited by TriPolar; 06-05-2019 at 04:01 PM.
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Old 06-05-2019, 04:14 PM
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I think you're on the right track. But the issue is that today we don't have even remotely enough renewable electricity (solar and wind) yet.

EVENTUALLY, in order to get enough GENERATION from solar and wind, we will need to build a large excess CAPACITY of solar and wind. As we all know, solar and wind generation is only a somewhat small fraction of their capacity, AND every once in a while they will have a large gap.

Nobody is even close to excess generation today. The best countries have maybe mid-double-digit renewable generation today, for small areas (Denmark, South Australia) and short spans of time, but none has significant excess capacity at sufficiently large scale.

There is also the issue that making hydrogen from natural gas is "much cheaper".

We still need to get rid of the whole attitude where fossil fuel is "cheap". Of course the earth holds enormous amounts of Gigawatt-hours of energy just sitting there in the ground just for the taking. So it is "understandable" that some people still believe fossil fuels are "cheap". That must change. More than high carbon taxes, we must get to a point where fossil fuels are simply out of the equation.

I can find studies about the cost of making hydrogen from wind energy but they typically assume dedicating a wind park to a hydrogen making facility. Needless to say, nobody today will build a large wind farm and use it only for hydrogen. And the calculations still show that it's not economic today (still more expensive than fossil).

The Wiki on Hydrogen production has somewhat detailed info and references, especially reading between the lines, you see that hydrogen production by electrolysis is still an experimental small scale affair whereas steam reforming is a mature, widespread and easy to procure tech. DOE and other research has been done for decades, here is one relatively recent roadmap: Hydrogen Production Tech Team Roadmap (PDF)

My own opinion:

Hydrogen is only one form of storing excess renewable energy. You can broaden the topic to other PTL (Power-to-Liquid) solutions, e.g. methanol or methane, or storage forms other than chemical, e.g. storing excess electricity as heat. Living in a cold climate, I used to worry about district heating for example. But once we get around to building that large excess of wind energy, then it will make eminent sense to store it (very inefficiently) as heat and run a small steam-turbine-cum-district-heating setup from it.

Again you can see we're not remotely there yet. Before any of this is practical, we have to build a large excess capacity of solar panels and wind turbines.

Can't happen quickly enough.

If that small country in the north of Europe could spend the same amount on wind as they spend on their new nuclear plants, they could get TWENTY TIMES more wind than they have now, and a capacity of twice the maximum demand. THEN we'd be talking.

Last edited by Frankenstein Monster; 06-05-2019 at 04:17 PM.
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Old 06-05-2019, 04:34 PM
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What this thread needs, for ignorati like me, is a brief list of storage methods other than battery with efficiency figures. (Sure, speak of a Manhattan Project for best battery, but let's review other approaches.)

Pumping water upward near hydro-electric power stations? What is the efficiency there as a percent?

How does net efficiency of hydrogen compare with batteries? What if the hydrogen need not be transported or compressed? What other local energy storage methods make sense?

How do big power systems store energy at present, or do they?

Last edited by septimus; 06-05-2019 at 04:35 PM.
  #28  
Old 06-05-2019, 05:56 PM
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Well if you believe the hype of the renewable hydrogen proponents:

Renewable hydrogen getting cheaper, Australia could lead global market

Quote:
Some of Australia’s leading energy experts say that renewable hydrogen is beginning to reach cost parity with some fossil fuel equivalents, and can emerge as a high potential export industry for Australia – with tens of billions of dollars – as technology costs continue to tumble.
Realistically they're talking about expressly building a large excess solar and wind capacity in order to make hydrogen from.

That may happen yet. We're only factors away from that being profitable.

We're orders of magnitude away from using today's "wasted" or curtailed electricity for making hydrogen.
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Old 06-05-2019, 06:20 PM
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Any given location can get a week of rain, but an entire continent can't. When one place gets rain, they draw the power from other places that are sunny. This is already done to some extent, and could be done more, and more efficiently, with upgrades to the grid.

And a car using a gaseous fuel needs a high-pressure tank, because the volume of the tank needs to fit into the car. But a power plant built where land is cheap (which is where most of them are) could just use a really big tank, at more manageable pressures. Nor need the energy used to pressurize the gas be entirely wasted: Much of that, you could harness when you release the gas. In fact, there are some energy-storage facilities that are based on just this, using ordinary air as their working gas.
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Old 06-05-2019, 06:35 PM
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I assume we're talking about hydrogen from water-splitting, right? So, one big constraint is water flow. This limits the location to a reasonable pipeline range to the ocean or a big river.

Someone already mentioned that electrolysis in itself is like 75% efficient. So there's 25% of the energy gone on top of that. For the hydrogen to be usable at all, it has to be compressed and liquified, which (WAG) is another big haircut off the efficiency. Factor in the energy needed to transport it, and I doubt it's worth it.

And count me on the bandwagon of people who want to know why you're dismissing hydro-pumping. . I'm aware of some reasons but I'm always up for new ones.
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Old 06-05-2019, 06:38 PM
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It seems to me like the best use of excess wind and solar is carbon capture & sequestration. If we're serious about solving atmospheric carbon, we'll need to be doing CCS anyway, and the 2 main constraints there are storage and energy. So why not locate the CCS plants where the excess energy production is?
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Old 06-05-2019, 06:39 PM
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I assume we're talking about hydrogen from water-splitting, right? So, one big constraint is water flow. This limits the location to a reasonable pipeline range to the ocean or a big river.

Someone already mentioned that electrolysis in itself is like 75% efficient. So there's 25% of the energy gone on top of that. For the hydrogen to be usable at all, it has to be compressed and liquified, which (WAG) is another big haircut off the efficiency. Factor in the energy needed to transport it, and I doubt it's worth it.

And count me on the bandwagon of people who want to know why you're dismissing hydro-pumping. . I'm aware of some reasons but I'm always up for new ones.
If the goal is for the hydrogen to be used as a storage battery to be expended at need into the same system that charges it, why does it need to be transported at all? Or liquified? Why not just get a really, really big tank, store the hydrogen on site, and put up no-smoking signs?

Last edited by begbert2; 06-05-2019 at 06:40 PM. Reason: typos
  #33  
Old 06-05-2019, 06:40 PM
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Nobody is even close to excess generation today.
Curtailment of excess renewable energy generation is quite common.
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Old 06-05-2019, 06:43 PM
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Why aren't we trying to solve the flaws with pumped-hydro instead of hydrogen? Is there really a hydrogen solution that is more likely, or is it wishful thinking like waiting for fusion to solve the problem?
There aren't really any major flaws to solve with pumped hydro. I suggest you meditate on geology and opportunities for pumped hydro in places like Kansas and you'll find the answer to your question.
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Old 06-05-2019, 06:44 PM
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As to using batteries:

https://www.technologyreview.com/s/6...ng-the-energy/

But we want to handle all energy needs not just 80% of demand of the electrical system. And we want to handle seasonal energy needs (remember the polar vortex?)--so instead of 12 hours we need a few weeks.

OP: both the European Union and Asians countries (like Japan and South Korea) are strongly interested in hydrogen--but there seems little interest in the U.S.
Busy now, but I have to point out that in another thread the guy from Real Engineering had a video cited before in the past discussion that claimed that to make it work, the costs for California alone for using batteries would be about 3.67 Trillion, but here the MIT group mentions 2.5 Trillion for a battery system for the whole of the USA.

Point being that, at least for the Real Engineering guy, I will have to blame that exagerated skepticism on an engineer that has not published his research to be evaluated with peer review.

Of course I have seen papers and reports that point out that not doing an effort will be more expensive than taking care of the issue, and IMHO solar, wind, and batteries will not be the only solutions. Even Nuclear should be part of the efforts that are needed to mitigate the issue.

Last edited by GIGObuster; 06-05-2019 at 06:47 PM.
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Old 06-05-2019, 06:56 PM
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There aren't really any major flaws to solve with pumped hydro. I suggest you meditate on geology and opportunities for pumped hydro in places like Kansas and you'll find the answer to your question.
Hydroelectric power is pretty well established so there's nothing that has to be done to start using it. However it may require some big ass reservoir that can have it's own issues. It can't be big enough to cause flooding from a breach, or get destroyed if it gets flooded. You can gain the drop with a hole in the ground though, geology isn't very limiting in that regard. You'll want it to operate with the least drop practical because it's costing you energy the higher you pump it.

Last edited by TriPolar; 06-05-2019 at 06:59 PM.
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Old 06-05-2019, 08:59 PM
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If the goal is for the hydrogen to be used as a storage battery to be expended at need into the same system that charges it, why does it need to be transported at all? Or liquified? Why not just get a really, really big tank, store the hydrogen on site, and put up no-smoking signs?
There's no realistic way of storing any usable amount of uncompressed hydrogen. So if we store it, we've got to liquefy it, which costs energy.

Quick calculation - 2 megawatts excess power generation. 16 megajoules to split a liter of water. We need to split a liter of water every 8 seconds, 10,800 liters a day. Seems manageable. We get 26,860,400 liters of hydrogen per day, which should compress down to 107000 liters. Less than a swimming pool, still manageable.

I'm too tired and also not smart enough to work out the energy loss in that compression process, or what would be lost in burning it to generate the energy, but if it's not too bad, then this actually seems doable. Set up a hydrogen-burning power plant next to the solar plant. Collect hydrogen in daytime, burn it at night, put it back on the grid. Just at a broad glance, this really does seem doable.
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Old 06-05-2019, 09:20 PM
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Quote:
Quoth TriPolar:

You'll want it to operate with the least drop practical because it's costing you energy the higher you pump it.
You're missing the point. That's not energy it's costing you; that's the energy you're storing. Which is the whole point of the exercise.
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Old 06-05-2019, 09:34 PM
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You're missing the point. That's not energy it's costing you; that's the energy you're storing. Which is the whole point of the exercise.
Yes, but the storage process has limited efficiency. There's a balance in their somewhere for maximum efficiency.
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Old 06-06-2019, 04:14 AM
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Curtailment of excess renewable energy generation is quite common.
Of course! What I meant was:

- Renewable is a small % of total generation (e.g. 10% wind in California)
- Curtailment is a small % of total renewable generation
- Curtailment happens on a small % of days

Hydrogen making equipment is very expensive. It makes no sense at all to buy that expensive equipment only to use it on a small fraction of the needed energy on a few days of the year.

Dedicated renewable hydrogen (see my earlier link) may make sense in a decade.

Last edited by Frankenstein Monster; 06-06-2019 at 04:15 AM.
  #41  
Old 06-06-2019, 07:12 AM
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Hydroelectric power is pretty well established so there's nothing that has to be done to start using it. However it may require some big ass reservoir that can have it's own issues. It can't be big enough to cause flooding from a breach, or get destroyed if it gets flooded. You can gain the drop with a hole in the ground though, geology isn't very limiting in that regard. You'll want it to operate with the least drop practical because it's costing you energy the higher you pump it.
I suggest you, at a minimum, read the Wikipedia article on this topic prior to commenting further. Least drop practical?
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Old 06-06-2019, 07:17 AM
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I suggest you, at a minimum, read the Wikipedia article on this topic prior to commenting further. Least drop practical?
Maybe I'm off base here, I should brush up on this instead of relying on a poor memory.
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Old 06-06-2019, 07:35 AM
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I suggest you, at a minimum, read the Wikipedia article on this topic prior to commenting further. Least drop practical?
Well right off the bat the Pumped-storage Hydroelectricity page says:

Quote:
The relatively low energy density of pumped storage systems requires either large flows and/or large differences in height between reservoirs.
So I misinterpreted something sometime in the past. There is a cost to pumping water to higher elevations but overall it must be outweighed by the greater efficiency of the difference in height.

But I am surprised to see the efficiency is so great:

Quote:
Taking into account evaporation losses from the exposed water surface and conversion losses, energy recovery of 70-80% or more can be achieved.
In addition it's use is already greater than I expected:

Quote:
Pumped storage is the largest-capacity form of grid energy storage available, and, as of 2017, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for over 95% of all active tracked storage installations worldwide, with a total installed nameplate capacity of over 184 GW, of which about 25 GW are in the United States.
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Old 06-06-2019, 09:32 AM
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We have a lot larger natural gas storage facilities than 190 million liters. ... That 129 MWh of energy from the Tesla plant is impressive...for a battery system. It's nothing to a natural gas plant. ...
That's exactly my point. To match even that small Tesla battery farm, you need to store 190 million liters of hydrogen. Because hydrogen has so little energy density - only 1/3 that of natural gas.

And actually I did the math wrong there. At 3.3 WH/liter, you need 600 million liters, not 190 million.
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Old 06-06-2019, 12:54 PM
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Would it be practical to store excess energy as thermal energy? Say, during the day, the electricity could be used to heat up something inert (salt?) then at night the hot material could be used to boil water to drive a turbine?
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Old 06-06-2019, 01:31 PM
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Would it be practical to store excess energy as thermal energy? Say, during the day, the electricity could be used to heat up something inert (salt?) then at night the hot material could be used to boil water to drive a turbine?
Absolutely. Many, many forms of this are being tried. Here are two I like.

From Wiki: Heat storage in hot rocks, concrete, pebbles etc

Quote:
This could, in principle, be used to store surplus wind or PV heat due to the ability of electrical heating to reach high temperatures. At the neighborhood level, the Wiggenhausen-Süd solar development at Friedrichshafen has received international attention. This features a 12,000 m3 (420,000 cu ft) reinforced concrete thermal store linked to 4,300 m² (46,000 sq ft) of solar collectors, which will supply the 570 houses with around 50% of their heating and hot water. Siemens builds a 36 MWh thermal storage near Hamburg with 600 °C basalt and 1.5 MW electric output.[23] A similar system is scheduled for Sorø, Denmark, with 41-58% of the stored 18 MWh heat returned for the town's district heating, and 30-41% returned as electricity.[24]
Many more methods described on that page.
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Old 06-06-2019, 02:30 PM
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And a car using a gaseous fuel needs a high-pressure tank, because the volume of the tank needs to fit into the car. But a power plant built where land is cheap (which is where most of them are) could just use a really big tank, at more manageable pressures. Nor need the energy used to pressurize the gas be entirely wasted: ....
1. Nuclear Energy is not Carbon free : https://theecologist.org/2015/feb/05...not-low-carbon
“...,the Climate Change Committee believes, the true figure is probably well above 50 grams - breaching the CCC's recommended limit for new sources of power generation beyond 2030.”

2. Hydrogen is the worst gas to compress : Whether you use an adiabatic process (reciprocating compressors) or a polytropic process (centrifugal compressor), much of the energy used for the compressor ends up heating the hydrogen than compressing it. This is from basic thermodynamics (gamma). Also Hydrogen compressors are hard to make and operate because Hydrogen is nature’s Houdini and escapes from everywhere.

3. Hydrogen is the worst gas for gas turbines or boilers : Hydrogen burns at a high temperature (so you need excess air) and the combustion products are low molecular weight. Since gas turbines convert momentum to energy, hydrogen gives the least efficiency in a gas turbine. Combustion of hydrogen almost always produces NOx since it burns at such high temperatures - so that in itself is a problem.
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Old 06-06-2019, 02:39 PM
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Was that first point meant to be a reply to me? The post you quoted didn't say anything about nuclear.

And yeah, you'll have losses in compressing and then releasing a gas. I said that the compression energy wouldn't be completely wasted, and that you could get back some of that energy.

TriPolar, I think you still don't get it. The energy cost of pumping to greater heights is balanced out by... the energy cost of pumping to greater heights.
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Old 06-06-2019, 04:16 PM
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Hydroelectric power is pretty well established so there's nothing that has to be done to start using it. However it may require some big ass reservoir that can have it's own issues. It can't be big enough to cause flooding from a breach, or get destroyed if it gets flooded. You can gain the drop with a hole in the ground though, geology isn't very limiting in that regard. You'll want it to operate with the least drop practical because it's costing you energy the higher you pump it.
And how exactly is water going to leave this hole in the ground? The rate of power that you can generate from this system depends on how quickly you can drain your reservoir. Having a system that drains at the rate that you need is absolutely a function of geology. You can't just dig a hole and expect water to drain out of it fast enough to be able to generate any meaningful power from your system - it would have to connect to a lower elevation open area or reservoir.

The reality is that hydro is really only realistically feasible when the geology enables formation of natural above-grade reservoirs - or if you want to frame it differently, the only thing holding you back from building pumped-hydro storage anywhere is cost. You could theoretically build an entirely above-grade dam structure in Kansas to do your hydro storage (assuming there is enough construction material available to build such a dam), but it would be astronomically expensive. There's a reason that hydro facilities are generally built in river or mountain valleys.
  #50  
Old 06-07-2019, 09:51 AM
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In undergraduate school, a guy who worked at North Little Rock Electric told me they used the water that collected behind the dam overnight to generate power for morning toast, coffee and shaving water. It was all gone by the end of the morning.
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