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Re:Why did renewables become so cheap so fast? by jes5199 on Wednesday December 02, 2020 @04:37PM (#25281982)
in the past they were cheaper. Now renewables are cheaper.

Right now, intermittent renewables actually drives up the cost of fossil fuels! Renewables do wacky things to the spot price of power - sometimes electricity is free or even has negative value, sometimes it's expensive. Ideally fossil fuel plants would only spin up when they could sell power at a profit, but they can't dispatch so quickly, so they end up selling power at a loss for minutes or hours after the solar panels or wind turbines kick back on.

This is producing market conditions that are favorable to batteries and super-capacitors, because they can dispatch in seconds, or milliseconds. Arbitraging between times of cheap power to times of expensive power can already be competitive with fossil fuels some of the time. And batteries are getting cheaper, too.

There's some question about what the ideal mix of generation vs storage will end up being. While storage is expensive, we'll tend to over-provision wind and solar, and end up throwing power away... unless we can come up for some use for it when we have moments of surplus. There's some talk of using it for things like ocean water desalination, but most of our machinery has such a high investment cost right now that the cost of electricity is not the biggest expense, so we don't actually have many machines that we idle until power gets cheap. Maybe that'll change eventually.

Re:Why did renewables become so cheap so fast? by eldaisfish on Wednesday December 02, 2020 @06:33PM (#25283281)
>Now renewables are cheaper.

Yes, provided you ignore the cost of balancing an increasingly volatile grid, a volatility that is created by renewables. Also provided you ignore the cost to provide energy when said renewables aren't generating any.

Claims to back up your statment, such as from Lazard, are horribly flawed because they use the metric of LCOE - levelised cost of energy - to claim that renewable energy is cheaper. It is, provided you ignore the slew of costs that are not borne by renewable generators but which ARE borne by consumers.

Yes, batteries are getting cheaper but not at the scale required for the grid. Before you quote the Australian Tesla battery, remember that it can only provide energy for minutes - yes, minutes.

What is needed today for a low-carbon future is nuclear and hydro. Renewables will get there one day but that day is not tomorrow or next year.

Re:Why did renewables become so cheap so fast? by blake1 on Wednesday December 02, 2020 @07:19PM (#25283667)
That volatility can be dealt with by distributing the renewables geographically. It’ll be sunny or windy somewhere. This requires overbuilding, which is currently cheaper that storage, and the average generation is highly predictable for day-ahead or hour-ahead trading. My rule of thumb is you can supply 70% of demand economically today without long distance transmission.

Search for “overbuilding renewables,” e.g. https://energycentral.com/c/em/overbuilding-curtailing-renew...

This still leaves room for hydro and nuclear.

The negative costs are borne by the owners of generating units that generate excess power when net demand falls. Solar can ramp down in milliseconds, windmills in minutes, CCGT can take hours, and nuclear takes days.

But what if we did add long distance transmission? Look at the US west of the Mississippi. I once estimated the capital cost of powering today’s demand using 100% renewables without storage.

That’s approximately $200bn in generation + $100bn for overcapacity.

The transmission system was mainly built to serve the legacy coal generators, but that’s often not where the best renewable resources are located. I estimated $40-80 billion for transmission.

That sounds like a lot, but 25% of the generation has already been spent. The cost of fuel for the gas generators, which is part of the LCOE, is on par with those numbers.

My biggest criticism of the Lazard study you mention is that it understates the cost of hedging fuel volatility costs.

Re:Why did renewables become so cheap so fast? by hcurtiss on Wednesday December 02, 2020 @08:48PM (#25284285)
As a guy who's staffed permitting efforts for major linear corridors, I'm here to tell you that building out that kind of transmission infrastructure is a pipe dream. At least in the western US, the NIMBYs and enviros are too powerful.
Re:Why did renewables become so cheap so fast? by flukus on Wednesday December 02, 2020 @07:31PM (#25283750)
> This requires overbuilding, which is currently cheaper that storage, and the average generation is highly predictable for day-ahead or hour-ahead trading.

We should also keep in mind that this isn't unique to renewables, all power sources have to overbuild because systems get taken offline for repair and maintenance regularly. Sometimes it's even weather dependent as well, in a recent heatwave France had to shutdown nuclear power stations because the river for cooling water was becoming too warm.

Re:Why did renewables become so cheap so fast? by manfredo on Wednesday December 02, 2020 @06:58PM (#25283498)
It's sad to see people downvote correct information.

For context, the US consumes ~12TWh of electricity daily, so 500 GWh per hour. Global lithium ion battery production is around 300 GWh per year. While it's true this is projected to rise exponentially, the amount dedicated to storage is minuscule compared to the scale required to fulfill even one hour of energy storage [1]. This has prompted people to propose more exotic forms of storage like hydrogen, methane produced through the Sabatier process, or thermal storage. But none of those have been deployed at any significant scale, and their feasibility remains unproven.

Nobody generates more than 20% of their electricity from solar. Denmark is the only country that generates over 30% of its power from wind, and Germany is the 3rd highest at 24.7% [2]. By comparison plenty of countries generate more than 30% of their electricity from nuclear power: Sweden, Finland, Czech Republic, Slovenia, Bulgaria, Belgium, Hungary, Ukraine, Slovakia, and France. And the last 3 all produce the majority of their electricity from nuclear. [3]

Fossil fuels didn't kick off the industrial revolution, it was the heat engine. The ability to translate thermal energy into mechanical energy. Heating a fluid, turning a turbine, which turns a dynamo is something we cannot easily replace. Replacing the source of heat with a carbon-free source represents a much more modest refactor as compared to trying to migrate modern societies off the the heat engine. Renewables make sense as mitigation: just slap down some solar or wind, don't bother with storage, and shave off daytime carbon emissions when it is producing. But not as the backbone of a carbon-free energy sector.

1. https://energycentral.com/c/ec/world-battery-production

2. https://en.wikipedia.org/wiki/List_of_countries_by_renewable...

3. https://en.wikipedia.org/wiki/Nuclear_power_by_country

Re:Why did renewables become so cheap so fast? by nl on Wednesday December 02, 2020 @10:11PM (#25284883)
> Nobody generates more than 20% of their electricity from solar. Denmark is the only country that generates over 30% of its power from wind, and Germany is the 3rd highest at 24.7% [2]. By comparison plenty of countries generate more than 30% of their electricity from nuclear power

This is an extremely odd comparison. No one is proposing a completely solar generation strategy - it's renewables vs whatever.

Plenty of countries generate more than 30% of their electricity from renewables.

Re:Why did renewables become so cheap so fast? by integer42 on Wednesday December 02, 2020 @08:09PM (#25284015)
Nuclears not some secret unexplored concept at this point. If it were competitive it would be competing. Its costs are too high, not due to regulations due to the sheer amount of resources involved in mining, refining, and operating. Not to mention initial construction.
Re:Why did renewables become so cheap so fast? by manfredo on Wednesday December 02, 2020 @08:32PM (#25284180)
It's doing much better in terms of actually being used as a large portion of countries electricity generation, as I demonstrated above. But more importantly, the reality is that nuclear isn't competing against renewables it's competing against a fossil fuel grid that's supplemented by renewables. Germany, the poster child for renewables, still emits 10x the carbon dioxide per watt of electricity as France.

Let me put it more bluntly. Renewables are indeed cheaper on a per-watt hour basis. But that's more than offset by the need to deal with intermittency. Batteries are great for cars, but they exist at nowhere near the scale required to decarbonize with a wind and solar generation base. More exotic proposals like thermal storage, hydrogen, or the Sabatier process remain in prototyping and academic stage. The cost of storage is a non-answer, because there's no real plan to build this storage.

Renewables make in a stopgap mitigation plan but we have no feasible way of building a grid that's powered completely or even mostly by renewables. If our plan is to decarbonize the energy sector, renewables do not offer a solution. Hydroelectricity, and geothermal power do, but those are geographically limited. Nuclear energy is the only source that can feasibly replace fossil fuels as a consistent, geographically independence, and carbon-free energy source.

TL;DR:

* Industrialization happened because we figured out we could heat water and push a piston (and later, spin a turbine). Modern society is built off the ability to produce mechanical and electrical energy from thermal energy.

* It's a lot easier to heat water and spin a turbine with a carbon-free source of heat, than to try and capture energy from sun and wind and store massive amounts of energy to overcome intermittency.

Re:Why did renewables become so cheap so fast? by wp381640 on Wednesday December 02, 2020 @09:49PM (#25284702)
Battery was and is never supposed to take up the entire storage load of a network - nobody is designing or forecasting future networks in that way.

Batteries provide fast response

Pumped hydro is what is being used on a lot of networks and in future network planning. Ironically old open cut mines are often perfect locations for them.

This paper discusses an algorithm used to find pumped hydro sites - there is _a lot_ of capacity out there waiting to be tapped

https://www.sciencedirect.com/science/article/pii/S030626191...

There are already numerous draft or under constructions plants that are "triple" projects with a combination of solar/wind + battery + pumped hydro

Re:Why did renewables become so cheap so fast? by nl on Wednesday December 02, 2020 @10:31PM (#25285024)
To add to this, there are numerous very large scale project already underway to use existing hydro capacity as pumped hydro storage.

Eg, Bath County Pump Storage is a 3GW plant[1] although ironically it is often filled using nuclear power because the hydro station can adapt better to rapid changes in demand.

In the US there is 22GW total pump hydro storage already (compared to say 98GW total nuclear power capacity).

[1] https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta...

Re:Why did renewables become so cheap so fast? by wp381640 on Thursday December 03, 2020 @12:34AM (#25285752)
add Snowy 2.0 in Australia - 2GW:

https://www.snowyhydro.com.au/snowy-20/about/

Re:Why did renewables become so cheap so fast? by manfredo on Thursday December 03, 2020 @01:40AM (#25286166)
Pumped hydroelectricity is geographically dependent - you need a valley or mountain that you can dam up to build pumped hydro. While it may be great for South Australia, the region examined in your linked paper, it's wrong to assume that this availability is uniform.
Re:Why did renewables become so cheap so fast? by nl on Friday December 04, 2020 @01:26AM (#25299618)
The available isn't uniform, but it sure is widespread!

"The perception has been there are limited sites for pumped hydro around the world, but we have found hundreds of thousands."

https://www.anu.edu.au/news/all-news/anu-finds-530000-potent...

Re:Why did renewables become so cheap so fast? by manfredo on Friday December 04, 2020 @03:19PM (#25307253)
This paper just ran an algorithm over a heightmap, and pinpointed potential reservoirs. This is a far cry from actually identifying feasible sites. The massive density of hydroelectric storage in the Himalayas, for instance, is far too remote to be developed at anything approaching reasonable cost. Not to mention, it still leaves swathes of places like Central north America, and much of Northern Europe without access to hydroelectric storage.
Re:Why did renewables become so cheap so fast? by nl on Saturday December 05, 2020 @12:00AM (#25311909)
The European electricity market is already very interconnected, so I doubt that would be a problem there at least.
Re:Why did renewables become so cheap so fast? by ncmncm on Thursday December 03, 2020 @04:35AM (#25287228)
Batteries are only the most expensive of a wide array of storage choices that today vie for which will end up cheapest, overall. Pumped hydro is mature, but underground and underwater compressed air are being proven; mine-shaft gravitic similarly; low-pressure LH2 is newly practical with aerogel insulation; carbon-captured LCH4, likewise; catalytic ammonia; and even powdered iron. None of these require any theoretical breakthroughs, just workaday engineering. In some cases combining them makes sense, such as mineshaft gravitics and compressed air in the same mineshaft. In other cases the storage medium is itself directly useful, as for example LH2 as aircraft fuel, and ammonia as both fertilizer and fuel.

Some depend on geography, particularly pumped hydro and mineshaft gravitic, and to a lesser degree compressed air. Catalytic improvements will bring rapid cost decline in LH2 and ammonia production. And, finally, battery technology, still the most immediately practical for home systems, is still improving fast. Any breakthroughs not anticipated only improve the picture.

The cost for utility-scale solar is many times less than roof-mounted, battery-backed home systems, but in places where distribution is expensive (rural) or unreliable (3rd world and California) it has strong appeal.

Re:Why did renewables become so cheap so fast? by integer42 on Thursday December 03, 2020 @09:28AM (#25289115)
Its a nice appeal to simplicity to say nuclear is just 'heating water and spinning a turbine', I could also say the sun is a very large carbon-free maintenance-free opex-free reactor in the sky and we just need to design a secondary stage of the power plant to transform the energy to electricity. And instead of pistons OR turbines, we can use a new type of machine specifically built for this purpose aka renewable energy technologies.

The reality is it doesn't matter how you word it or what you think should be simpler. Its what the economy can actually build, and including risk, buying solar panels which have no moving parts and last for decades are currently the more efficient way to add a watt to the grid.

Your "blunt" assertion where you predict the capacity of the grid to accomodate renewables and the quantity of battery storage and the feasibility of every potential upcoming storage technology probably requires a few sources to be taken seriously as well.

Re:Why did renewables become so cheap so fast? by manfredo on Saturday December 05, 2020 @09:53PM (#25320607)
Correct, the sun is a great source of energy. But we use most of our energy when the sun is blocked by the earth. The sun is opex and capex free, but the storage necessary to make it feasible requires massive capital expenditure and massive operational expenditure.

The point is, just adding watts to the grid is not a solution. You needed watt when they're needed and where they're needed. And doing that with renewables is a lot harder, hence why we're really just supplementing fossil fuels with wind and solar not really working towards full decarbonization.

My assertions about the capacity of battery production were indeed backed by sources of predicted growth of battery production. In case you missed it: https://news.ycombinator.com/item?id=25283498

Re:Why did renewables become so cheap so fast? by dieortin on Wednesday December 02, 2020 @07:34PM (#25283771)
> It's sad to see people downvote correct information.

I'm confused, there's no downvote button in HN.

Re:Why did renewables become so cheap so fast? by manfredo on Wednesday December 02, 2020 @07:38PM (#25283796)
There is you need a certain amount (200?) of karma to use it. Posts with negative votes have more lightly colored text. The above post no longer has negative votes so it's normal colored now.
Re:Why did renewables become so cheap so fast? by DoingIsLearning on Thursday December 03, 2020 @02:36AM (#25286536)
For completion, am not sure if it was 200 before but it's 1000 now.
Re:Why did renewables become so cheap so fast? by nicoburns on Wednesday December 02, 2020 @09:21PM (#25284507)
> Yes, provided you ignore the cost of balancing an increasingly volatile grid, a volatility that is created by renewables. Also provided you ignore the cost to provide energy when said renewables aren't generating any.

If we're taking into account those kind of costs, shouldn't we also account for the cost emitting CO2?

Re:Why did renewables become so cheap so fast? by Reason077 on Thursday December 03, 2020 @05:41AM (#25287621)
> "What is needed today for a low-carbon future is nuclear and hydro."

Hydro is great if you have the terrain for it, but much of the world is not geographically suited for extensive hydro. Nuclear is extraordinarily expensive and often takes decades to plan and build.

Renewables can be built far cheaper and far more quickly. On grids that still have gas & coal fired power stations, every GWh of electricity produced from renewables displaces a GWh that would otherwise be produced from fossil fuels.

Or, to put it another way, every dollar spent on renewables will result in a significantly larger and faster reduction of carbon emissions than if that same dollar were spent on nuclear.

Re:Why did renewables become so cheap so fast? by eldaisfish on Thursday December 03, 2020 @11:15AM (#25290364)
>Nuclear is extraordinarily expensive and often takes decades to plan and build.

That's not necessarily true as countries like China are building new nuclear reactors in 4-5 years. Remember that nuclear is one of the few industries that designs for the worst case scenario which is part of the high cost. The other component of the high cost is often policy and overzealous bureaucracy.

>On grids that still have gas & coal fired power stations, every GWh of electricity produced from renewables displaces a GWh that would otherwise be produced from fossil fuels.

This is not true. A kWh from a wind turbine is absolutely not equal to a kWh from a coal/gas/nuclear/hydro plant due to the fact that the capacity factor for a typical wind turbine is around 20-30%. A hydro plant often runs at > 80% capacity factor.

Re:Why did renewables become so cheap so fast? by Reason077 on Thursday December 03, 2020 @12:20PM (#25291450)
> "A kWh from a wind turbine is absolutely not equal to a kWh from a coal/gas/nuclear/hydro plant due to the fact that the capacity factor for a typical wind turbine is around 20-30%."

No, a kWh of energy produced by a wind turbine absolutely is equal to a kWh produced by any other means.

You'd be correct to say that a kW of capacity is not equal. (ie: a 1 GW wind farm may not produce as much energy as a 1 GW nuclear plant, but 1 GWh of energy is 1 GWh of energy, no matter what source produces it).

For what it's worth, UK off-shore wind farms currently have load factors of between 39 and 47%, and these are predicted to exceed 50% by 2035. Source: https://renews.biz/55349/uk-offshore-wind-load-factors-to-ex...

Re:Why did renewables become so cheap so fast? by eldaisfish on Thursday December 03, 2020 @03:37PM (#25294445)
yes, that's correct. i used the wrong idea there.
Re:Why did renewables become so cheap so fast? by jes5199 on Wednesday December 02, 2020 @11:55PM (#25285542)
if you wanna talk externalities, let’s price in the damage done by climate change into fossil fuel costs, and see which one is cheaper
Re:Why did renewables become so cheap so fast? by Ma8ee on Wednesday December 02, 2020 @05:34PM (#25282661)
I think we’ll start using more ways to store the energy. In the scenarios you describe, when the energy price fluctuate so wildly, the processes don’t have to be efficient. There’s not really a problem if 70% is lost in the process if the energy we started with is free. Pumping water to higher elevation or hydrogen production is suddenly reasonable.
Re:Why did renewables become so cheap so fast? by xyzzyz on Wednesday December 02, 2020 @06:55PM (#25283473)
Pumped storage is great, but it's simply not viable at a large scale. There are very few places where natural landscape allows it, and making more artificial ones would require flooding vast areas. Considering how difficult it often is to build solar plants on deserts (e.g. consider Ivanpah solar plant, which almost did not get build due to its impact on habitat of desert tortoises, which ended up getting relocated at a cost of $300k each), I don't expect the green interest groups to accept such wholesale destruction of environments.
Re:Why did renewables become so cheap so fast? by robocat on Wednesday December 02, 2020 @07:28PM (#25283733)
Existing hydro lakes can act as storage (within the constraints of how much inflow there is and minimum outflow rates).

Decrease lake outflow when solar and wind are producing power. Increase lake outflow when they are not.

https://www.hydro.org/waterpower/why-hydro/available/

Re:Why did renewables become so cheap so fast? by xyzzyz on Wednesday December 02, 2020 @08:01PM (#25283961)
Your link says that at best we could double our current hydro generation capacity, which supports my point: it's simply too little for our storage needs, and if we electrify more of our economy (i.e. use it to replace heat and transport for which we use a lot of fossils now), it will be even less. It might still be worth doing, but is far from solving the storage problem: it just has significant limits on its potential scale.
Re:Why did renewables become so cheap so fast? by nl on Wednesday December 02, 2020 @10:38PM (#25285072)
> Your link says that at best we could double our current hydro generation capacity

No, it says "that without building a single new dam" [hydro could roughly double its existing capacity in the US].

I'll assume you just misread that, but in any case that's pretty different to building new dams, or utilising tech like mines, or at-sea pumped storage.

Re:Why did renewables become so cheap so fast? by xyzzyz on Wednesday December 02, 2020 @11:19PM (#25285332)
> No, it says "that without building a single new dam" [hydro could roughly double its existing capacity in the US].

No, that's not what it says. It says:

> The report estimates that without building a single new dam, these available hydropower resources, if fully developed, could provide an electrical generating capacity of more than 12 gigawatts (GW), equivalent to roughly 15 percent of current U.S. hydropower capacity.

Without constructing any new dams, you only increase it by 15%, not double it. Also, consider that 12 GW is 105 TWh per year. US consumes 4100 TWh of electricity per year. It would sure be nice to increase non-fossil electricity production by 2.5%, but that's clearly not very much. If the plan is to use hydro to cover the shortfall when the renewables are not producing enough, you need much more generating capacity than 12 GW, and more than 65 GW your link suggests could be potentially built. Finally, 2.5% is on the order of our annual growth in electricity consumption, which will in fact accelerate as we move off fossils. Thus, building out all possible hydro will only buy one year of growth in consumption.

Re:Why did renewables become so cheap so fast? by nl on Thursday December 03, 2020 @12:24AM (#25285703)
Yes, sorry you are right!

My error was confusing the "7% total capacity" and "15% existing capacity" not being off the same baseline.

Re:Why did renewables become so cheap so fast? by RcouF1uZ4gsC on Wednesday December 02, 2020 @07:05PM (#25283543)
> I don't expect the green interest groups to accept such wholesale destruction of environments.

In the grand scheme of things, this is like refusing chemotherapy for cancer because it makes your hair fall out.

Climate change is a huge issue. You have to be willing to sacrifice what would normally be valid environmental concerns to address it. You either believe it is an emergency or not.

Re:Why did renewables become so cheap so fast? by Ma8ee on Thursday December 03, 2020 @05:27AM (#25287553)
There are probably not one general solution that will work everywhere. But for example in Sweden where about half of the electricity already is from hydropower, it will work well to even out seasonal variations, from for example getting very little sun in the winter. But say for California, where there’s enough sun most days of the year, generating hydrogen might work better to even out the electricity generation between night and day.
Re:Why did renewables become so cheap so fast? by Ma8ee on Thursday December 03, 2020 @05:34AM (#25287581)
And considering solar power, there’s no shortage of available space. There’s plenty of roofs to cover with panels. Or line the sides of, say, Interstate 5 with a wall of vertical panels that also helps keep wild animals from the road and reduce noise pollution.
Re:Why did renewables become so cheap so fast? by cbmuser on Wednesday December 02, 2020 @07:08PM (#25283569)
There is no reasonable and economic way to store Terawatthours of electricity.

Even huge hydrostorage plants have only a few GWh.

Re:Why did renewables become so cheap so fast? by Reason077 on Wednesday December 02, 2020 @07:29PM (#25283738)
Huh? Norway alone has 85 TWh of hydrologic storage.

New Zealand has about 4 TWh, but they are considering adding an additional 5-12 TWh with one single storage project:

https://www.odt.co.nz/regions/central-otago/scientific-thoug...

Re:Why did renewables become so cheap so fast? by adrianmonk on Wednesday December 02, 2020 @07:05PM (#25283539)
> Ideally fossil fuel plants would only spin up when they could sell power at a profit

Another effect is it makes these plants sit idle for periods of time.

It costs a lot of money to build a power plant. Every hour it sits idle is an hour you're not getting any benefit out of the investment you made. So it takes longer to break even on your investment. (Possibly, as a consolation, the plant lasts longer or has lower yearly maintenance costs.)

Re:Why did renewables become so cheap so fast? by lotsofpulp on Wednesday December 02, 2020 @07:36PM (#25283783)
In my experience, machinery experiences more wear and tear if you repeatedly turn it off and on than just letting it run constantly.

I’d expect a power plant to be the same with all the heat and whatnot.

Re:Why did renewables become so cheap so fast? by robocat on Wednesday December 02, 2020 @07:30PM (#25283747)
Peaker plants can get paid fees to be ready to deliver power, even without actually running. I think there are plants that get built, paid for as a pure peaker plant, and never run because the peaker is not required.
Re:Why did renewables become so cheap so fast? by xupybd on Wednesday December 02, 2020 @05:52PM (#25282845)
>While storage is expensive, we'll tend to over-provision wind and solar, and end up throwing power away... unless we can come up for some use for it when we have moments of surplus

Maybe Carbon sequestration?

Re:Why did renewables become so cheap so fast? by jes5199 on Wednesday December 02, 2020 @05:57PM (#25282902)
I sure hope so.
Re:Why did renewables become so cheap so fast? by alliao on Wednesday December 02, 2020 @05:42PM (#25282744)
isn't that the game plan for hydrogen powered vehicles? so they can build a plan to absorb all these excess from over provisioning at a lower rate to produce hydrogen for their fleet
Re:Why did renewables become so cheap so fast? by ncmncm on Thursday December 03, 2020 @04:49AM (#25287339)
This is especially attractive for aircraft, but it will take awhile to happen. We probably need new aircraft.

Hopefully civilization will not collapse first, from refugees driving fascist governments into power, and former democracies self-surveilling themselves into locked-in dictatorships.

On the upside, collapsed civilization will have lower energy demands, and will find carbon extraction and transport harder to organize.

Re:Why did renewables become so cheap so fast? by bregma on Thursday December 03, 2020 @08:10AM (#25288452)
Sure. Find some way to break up CO2 from the atmosphere and bond hydrogen to the carbons. It creates a relatively safe, easy-to-use hydrogen storage medium and it reduces greenhouse gases at the same time. The cars would just need to break the carbon-hydrogen bonds to release the energy once again, and the process is GHG-neutral.