Could 'unburning' CO2 be 'the next big thing' in energy?

[sengsational]

The team used a catalyst made of carbon, copper and nitrogen and applied voltage to trigger a complicated chemical reaction that essentially reverses the combustion process.

https://www.ornl.gov/news/nano-spike-catalysts-convert-carbon-dioxide-directly-ethanol

 

[NW-Bound]

I like it. Could be more economically feasible than huge banks of Li-ion batteries. Still in its infancy, so we have to wait to see how it pans out.

 

[GrayHare]

All methods of CO2 removal require energy. Presumably that energy would be of the renewable kind, but each watt of it consumed for CO2 removal is a watt that becomes unavailable to replace energy sources that create CO2.

 

[NW-Bound]

Hence, the use of excess solar energy during the day to "charge" the ethanol plant. Then, the ethanol is used at night.

The big problem with solar energy right now is storage for night use. Li-ion battery technology is well known, but too expensive.

 

[samclem]

Pretty interesting. And co-locating the solar array and CO2->ethanol converter near existing CO2-producing power plants also allows the same power-line infrastructure, etc to be used. These NG or coal plants tend to have quite a bit of clear space around them for other reasons anyway, so there will likely be places to put the ethanol storage tanks and maybe even the solar panels themselves. It could make for some very efficient packaging.

But will this process be cheaper and otherwise more practical than just using sunlight and the CO2 in bioreactors to grow algae for fuel? It does sound simpler. It would be interesting to know what non-ethanol chemicals being produced as well. Hopefully something useful and non-hazardous. Water?

 

[ERD50]

Approaches like this do seem to make sense. Hopefully, something along these lines can actually make it into production, that's almost always a long shot.

But it's encouraging to see ideas like this, instead of the inane scams like, dare I say it... 'solar roadways'?

-ERD50

 

[meierlde]

Hence, the use of excess solar energy during the day to "charge" the ethanol plant. Then, the ethanol is used at night.

The big problem with solar energy right now is storage for night use. Li-ion battery technology is well known, but too expensive.

Actually there is a process where you split water with electricity and then add co2 to get methane and water out. (this is discussed in the various books on building mars colonies). Rather than invent new infrastructure just put the methane into the existing natural gas pipeline network. It is just an inorganice version of biofuel. Then run the natural gas thru combined cycle plants when the renewables are not providing energy. (note that wind and solar somewhat complement each other as each peaks a different times, the solar in the afternoon and the wind about midnight)

 

[Walt34]

But it's encouraging to see ideas like this, instead of the inane scams like, dare I say it... 'solar roadways'?

-ERD50

What? You haven't heard about these:

Perpetual Motion Machines.

 

[ERD50]

Hence, the use of excess solar energy during the day to "charge" the ethanol plant. Then, the ethanol is used at night.

The big problem with solar energy right now is storage for night use. Li-ion battery technology is well known, but too expensive.

Yes, but it will be a while before we have enough excess solar to make it worthwhile to try to harvest it. If it only happens occasionally, it just isn't worth the capital costs.

In the US, we get about 1.25% of our electricity from solar (from wiki - that's actually higher than I thought, as it is including an estimate of the output of home solar, as those numbers aren't recorded anywhere).

But when you start to get larger average numbers from solar PV, you hit the need for storage (or decide to waste it) pretty quickly. Some rough simplified numbers to illustrate:

Figure that most of the solar energy occurs in the mid 6 hours of the day, just 1/4 of the day. So the energy during those 4 hours has to 4x the average output number. So to hit a 25% average on the grid, it has to produce 100% of the grid energy during those 6 hours.

And of course it gets worse than that, with seasonal variations, and days of snow/cloud cover.

That's offset some by the fact that demand is higher during the day. Charts I've seen put daytime demand at ~ 2x nighttime demand, so daytime would be ~ 1.33 x average, and nighttime ~ 0.67 x average.

So the peaks/excess will be intermittent, seasonal, and last only a few hours on the days they occur. That's a tough situation to make back your capital investment in any kind of storage system.

It might make sense to forget about storage, and use the solar to make fuel for cars. High energy dense fuel like methanol or ethanol is a very high value product with few alternatives.

-ERD50

 

[NW-Bound]

Actually there is a process where you split water with electricity and then add co2 to get methane and water out. (this is discussed in the various books on building mars colonies). Rather than invent new infrastructure just put the methane into the existing natural gas pipeline network. It is just an inorganice version of biofuel. Then run the natural gas thru combined cycle plants when the renewables are not providing energy. (note that wind and solar somewhat complement each other as each peaks a different times, the solar in the afternoon and the wind about midnight)

I am no expert on energy. Obviously, this new ethanol production scheme will have to compete with other known methods for economic feasibility.

Yes, but it will be a while before we have enough excess solar to make it worthwhile to try to harvest it. If it only happens occasionally, it just isn't worth the capital costs...

With the price of solar panel dropping, and being surrounded by so much sunlight here in the SW, I could not help thinking that the reason we do not have more huge installations out in the desert is because we lack economical storage methods.

It might make sense to forget about storage, and use the solar to make fuel for cars. High energy dense fuel like methanol or ethanol is a very high value product with few alternatives.

Sure. It's still energy storage, but for another application. Once we get it, the ethanol, we can use it for anything.

Maybe it will pan out, but we have struck out so many times before. But people have to keep on trying, right?

 

[NW-Bound]

Quite often, a very promising method or machine fails to reach widespread use because of practical limitations that are not known until we turn it into something for everyday use.

A couple of years ago, I found very interesting an RV that carried no propane (for cooking and heating), and did not need a generator. It used Li-ion batteries and an inverter to run induction burners for cooking, AC, heater, refrigerator, etc... To recharge the batteries it had a powerful alternator mounted on the main engine, solar panels, and a fuel cell. Yes, a fuel cell. The fuel cell is only 100W, but it runs silently 24 hours using methanol as fuel. How cool is that? I forgot how much that fuel cell cost. The power is low, but could one have two for more power?

They do not offer the fuel cell option anymore. These small fuel cells typically cost $5K-10K. And I don't know how long their membrane lasts.

 

[Mdlerth]

Burn Sadi Carnot books for energy!

All methods of CO2 removal require energy. Presumably that energy would be of the renewable kind, but each watt of it consumed for CO2 removal is a watt that becomes unavailable to replace energy sources that create CO2.

Too bad that energy conversions can't be done in both directions with equal efficiency. Maybe we should petition Congress to repeal the second law of thermodynamics.

 

[GrayHare]

There used to be Anti-Entropy lobbyists but over time the group just gradually fell apart.

Yes, but it will be a while before we have enough excess solar to make it worthwhile to try to harvest it. If it only happens occasionally, it just isn't worth the capital costs.

That's what I was thinking. As reflected by a price higher than other energy sources, there isn't an excess of solar power, at least not yet.

 

[NW-Bound]

Solar panels are getting so cheap, it surprised me when I last looked.

At a local retail store, I can get a 305W panel for $270. And at my SW location, this panel will produce about 670kWh annually. At a price of 10c/kWh, that's $67/year, which is pretty darn good. The panel pays for itself in 4 years.

Of course, one needs to add other hardware costs to that of the panel, but you can see the number starts to make sense.

 

[ERD50]

Solar panels are getting so cheap, it surprised me when I last looked.

At a local retail store, I can get a 305W panel for $270. And at my SW location, this panel will produce about 670kWh annually. At a price of 10c/kWh, that's $67/year, which is pretty darn good. The panel pays for itself in 4 years.

Of course, one needs to add other hardware costs to that of the panel, but you can see the number starts to make sense.

And that's a big problem for solar. The 'green' sites keep talking about how panel prices have dropped, but they've already dropped to the point that they only represent about ~ 1/3 of the total installed price (not even counting any added costs over the life of the installation - replacing inverters, cleaning, remove/replace for roof repairs, etc). Inverters and labor and metal frames and wiring aren't going to come down, and may go up.

Further drops in solar panels won't have much effect on lowering the overall cost of solar. I'm not even sure the future drops, which are likely flattening, can outpace rises in costs of the other elements.

-ERD50

 

[NW-Bound]

For small-scale home installations, the total solar system cost may not go down further. But large commercial installations have better economy of scale, and that is what I was thinking about. And they would get panels at even a lower price than the $270 that retail customers get.

Also, schemes like the ethanol production talked about in this thread do not lend themselves to small systems in people's garages. Else, I would consider a small nuclear reactor in my backyard.

 

[travelover]

I've got a device in my back yard that converts CO2 to oxygen using solar power. In fact, I raked up some of the fallen solar collectors this afternoon. Amazingly it provides shade for my house, too, and a home for several squirrels and birds.

 

[NW-Bound]

You've got to find a way to sequester all the carbon that your device captured off the air, and that you are raking now.

Else, it gets back to the atmosphere, and all your effort is for naught.

 

[travelover]

You've got to find a way to sequester all the carbon that your device captured off the air, and that you are raking now.

Else, it gets back to the atmosphere, and all your effort is for naught.

Oh, it is sequestered for now, right in the trunk and branches. This process has been going on for quite a few years. It's a surprisingly well thought out device.

 

[NW-Bound]

It is not without limitation. In places where the supply of H2O is limited, these devices can do more harm than good.

 

[ERD50]

For small-scale home installations, the total solar system cost may not go down further. But large commercial installations have better economy of scale, and that is what I was thinking about. And they would get panels at even a lower price than the $270 that retail customers get. ...

Sure, but it's all relative to the prices the large installations have. They get the panels cheaper, and have economy of scale on installation, but my point still holds. The panel cost is becoming a smaller part of the overall cost. So dropping panel prices have diminishing returns on total cost of ownership.

-ERD50

 

[samclem]

So, let's put the "solar storage" aspect to the side. The process described takes electricity and CO2 as inputs and yields ethanol (as well as some other stuff they don't describe). So, after we've put the energy in, how much chemical potential energy is in the ethanol (to be released when it burns)? And, after we burn it, how much CO2 is released to the atmosphere?

Without knowing the energy balance, one might think we could take the CO2 from a natural gas electric plant, add some electricity produced by the plant, and get some ethanol that could be burned to make more electricity. But I think this process would:
1) Run into some problems with the second law
2) Be putting as much CO2 into the atmosphere as the NG plant was making, without all this complexity.

 

[meierlde]

So, let's put the "solar storage" aspect to the side. The process described takes electricity and CO2 as inputs and yields ethanol (as well as some other stuff they don't describe). So, after we've put the energy in, how much chemical potential energy is in the ethanol (to be released when it burns)? And, after we burn it, how much CO2 is released to the atmosphere?

Without knowing the energy balance, one might think we could take the CO2 from a natural gas electric plant, add some electricity produced by the plant, and get some ethanol that could be burned to make more electricity. But I think this process would:
1) Run into some problems with the second law
2) Be putting as much CO2 into the atmosphere as the NG plant was making, without all this complexity.

With the methane example using the Sabatier Process the energy needed is for the electrolysis of water. which Wikipedia says is between 50 and 60 % efficient. Then mixing the hydrogen with CO2 is actually exothermic so some energy is returned as the methane is made. This process is actually used on the space station to get rid of the CO2 there and it dumps the methane into space.
Anothe nice thing is that you need dc to make it work so if using photovoltaics no inverter is needed.
Further this is a way to put solar in deserts far from demand for power, generate the methane and then ship it. (For example for Europe from the Sahara, Note that Saudi Arabia might well become a big player here due to its abundant sunshine. Might also work for Chile as well. The nice thing about methane is that infrastructure is well developed for its usage.

 

[gerntz]

but each watt of it consumed for CO2 removal is a watt that becomes unavailable to replace energy sources that create CO2.

I don't see how solar energy becomes anymore unavailable because of this till the surface of earth is completely covered in solar panels. And by then solar energy collectors may be in space.

 

[meierlde]

All methods of CO2 removal require energy. Presumably that energy would be of the renewable kind, but each watt of it consumed for CO2 removal is a watt that becomes unavailable to replace energy sources that create CO2.

The issue is this is a way to put solar in fairly remote areas far from major electric grid elements. For example the northern part of Western Australia, the empty quarter of Saudi Arabia, parts of the Sahara the Gobi, or the Chilean desert where it never rains, etc. You put the plant there and instead of having to move electricty long distances you move the ethanol or methane or other hydrocarbon by well understood means to where it will be used for electric generation. While this does not apply so much to the continental us because no area is really that remote (outside national parks), it could for example be used in some of the offshore islands of S calif to put solar on them (and perhaps in conjunction with offshore wind here. Possibly also the lee side of the Canary Islands.

It turns out that moving electricty long distances is hard you either have to go to HVDC or with AC really hard to keep the grid stable and with fairly large losses in transmission.
Examples of places in the continental us might include parts of western utah where there is currently a very small population and as a result little electric infrastructure, as well as Nevada along parts of the lonliest highway, or eastern or such as the Alvord desert (east of steens mountain)