Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

news.ycombinator.com

Post reply on HN
Print view View original

491–500 of 589 posts

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#491

Post by pfdietz »

CHsurfer wrote: post #437
maxxxxx wrote: post #411

Earlier quoted context omitted.

It’s kind of ironic that cars and power plants work hard on getting rid of that energy.

Modern power plants work hard at getting every last bit of that energy before it escapes. Current Combined Cycle plants, that generate steam from the exhaust of a gas turbine, are currently getting over 60% efficiency.

One must be a bit careful there. 60% efficiency based on the LOWER heating value of natural gas. That ignores the heat available from condensing the water of combustion. Coal plants typically use the higher heating value when computing efficiency, which does reflect the latent heat of vaporization of that water.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#492

Post by danieltillett »

mrob wrote: post #390
danieltillett wrote: post #385

This can’t work because of Jevon’s paradox [0]. Every barrel of gasoline created by this process just displaces a barrel of fossil gasoline, pushing down the price of gasoline at the margins resulting in increased consumption. CO2 neutral gasoline can only work if you can get the cost below the marginal cost of production of fossil gasoline such that the oil stays in the ground. This is a massive ask on thermodynamic…

Jevon's paradox only applies because governments subsidize fossil fuels by failing to correct the market failure of their externalities. If they were taxed appropriately to compensate for the damage they do then synthetic hydrocarbon fuels would probably be viable in the cases where batteries are unsuitable because of insufficient energy density (e.g. long-distance aviation).

No. I think you really need to understand Jevon's paradox. I highly encourage you to do so - once I learned about it so much of the world became clearer.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#493

Post by pfdietz »

acidburnNSA wrote: post #442
rmcginnis wrote: post #337

Earlier quoted context omitted.

It's true that running part of the time is not as good as running continuously, but if the capital is low enough, it's ok to start out running intermittently until we get to the point where we have low cost dedicated power and can have a higher uptime. We will have to shed heat from the system to the environment, but that can be done passively. Current densities are likely going to be substantially lower, but our cap…

Hook to nuclear and hydro electricity and you can get your uptime much higher while remaining carbon free. That should give you a good 2x boost on capex at least.

Building nuclear plants to save on electrolyzer capital cost is not a good idea at all. Penny wise, pound foolish.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#494

Post by Already__Taken »

KaiserPro wrote: post #475
worldsayshi wrote: post #448

Earlier quoted context omitted.

The co2 could be stored underground? I guess that could deal with the timing issue at least?

You'd have to separate pump and store it, when electricity is expensive. I suspect the advantage of this system is that is doesn't need pure co2 to work

And if you were storing CO2 I suspect the first question is how do we liquify it. So the advantage fades away.

edit: You'd probably want to store the electricity on-site instead for this. At least if there's no CO2 to consume you can be in the electricity storage business.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#495

Post by pfdietz »

seppel wrote: post #383
lutorm wrote: post #359

Earlier quoted context omitted.

* producing solar panels and such also requires energy input, and these do have limited lifetime. What is the real full-cycle energy conversion ratio is? I wonder what this is, too, but a typical 300W panel with 20 year lifespan will generate something like 20MWh over its lifetime. You can't possibly use anywhere near that much energy to manufacture it.

My personal pet theory is that the energy consumption is more or less equivalent to the price. So as long as the solar panel is not economically viable, it does not provide an energy surplus. 20MWh is not much, it's $500-$3000 worth of energy, depending on taxes and stuff. Can you buy, install, connect, maintain, clean a 300W solar panel for 20 years for this price? Edit: Also, 20MWh is quite high. That's 9h of perfe…

"My personal pet theory is that the energy consumption is more or less equivalent to the price."

This implies that energy is the only input to making PV, which is clearly wrong.

Or maybe you're saying that if we trace back costs into the economy, from the workers, to the grocery stores where they buy their food, to the farmers, etc. etc., it all eventually comes back to energy. In that case the energy return on investment is going to be 1:1 in steady state, which indicates that's not a useful metric either.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#496

Post by danw1979 »

solarkraft wrote: post #51
Damorian wrote: post #34

Earlier quoted context omitted.

What? They compete today with significantly lower fuel cost. You see 100+ mpge on every electric car I know of today, you're looking at half-1/3 the per mile cost in an electric car. That more than makes up for the higher upfront cost over the lifetime of the vehicle, with cars you can go buy right now, today.

And that doesn't even take into account the superior UX.

I don't know why you got down voted on this. My experience of EV vs ICE (sometimes in the same vehicle - daily driving in a Prius plug-in) agrees entirely with your comment: the lovely EV experience of linear, quiet acceleration is so pleasant compared to driving a petrol car, even an automatic. And my Prius in EV mode isn't even a that great an electric experience compared to that of an i3 or 2018 Leaf.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#497

Post by hef19898 »

beefman wrote: post #409
seppel wrote: post #383

Earlier quoted context omitted.

My personal pet theory is that the energy consumption is more or less equivalent to the price. So as long as the solar panel is not economically viable, it does not provide an energy surplus. 20MWh is not much, it's $500-$3000 worth of energy, depending on taxes and stuff. Can you buy, install, connect, maintain, clean a 300W solar panel for 20 years for this price? Edit: Also, 20MWh is quite high. That's 9h of perfe…

Well-placed solar plants have capacity factors of about 20%, so 10MWh. That's worth about $1200 at the retail end of the grid (or $2600 if your local utility has gone bankrupt). At the production end, it costs anywhere from $100 for fully depreciated hydro[1] to $1400 for solar PPAs made by bankrupt utilities[2] to $600 for new solar when you assume an unrealistic cap factor and ignore Chinese subsidies[3] to $240 if…

Last time I checked retail prices were around 0.30 to 0.32 $ per Wp for large customers. So your high efficiency, last tech 300 Wp module would be around 100$ including shipping for large orders. Could go up to around 120 to 150 for smaller volumes. Of course, market prices may vary depending on demand and availability.

Re: Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline

#500

Post by salv0 »

brilee wrote: post #428

A few questions from a chemistry major 1. why extract from the air when you can just put a device on the smokestack of an existing coal or natural gas plant? The higher CO2 density of the effluent will make things more efficient. 2. Your key innovation isn't the part where you pull CO2 out of the air; it's the nanotube-based reverse osmosis process for separating ethanol from water. This process could just as easily…

But then, why to use solar energy to convert CO2 into fuel when you can convert the solar energy into electricity directly and remove the need for the fossil fuel based power plants?
Post reply on HN