Thanks for the reference, it’ll make interesting reading, also the keyword ‘hydrogen economy’ it lead me to the Wikipedia page that discusses the costs directly.
I can definitely see that using hydrogen for energy storage is not an obvious choice, but extracting oil from the Canadian tar sands sounded unrealistic 10-20 years ago. IMHO it is an ideal choice for storing energy generated by renewable sources in inhospitable locations, which is often where the energy is most concentrated.
The wiki page mentions the costs of generating the equivalent of 1 gallon of oil for various renewable sources, it appears as if some (biomass, wind) could be efficient today.
Sure - it was market forces that made Canadian oil sands feasible. I am hoping you are saying that market forces will make hydrogen economy feasible - right ?
It is very counter intuitive but this is not true. Just take Natural Gas for example - it is much more abundant today than Hydrogen can be even in 30 years - yet gathering, transporting and distributing Natural gas has been a big infrastructure challenge with LNG and CNG. And natural gas can be liquefied at around -150F but you need to go lot lot cooler for hydrogen.
That is very very misleading. Consider this - you pay around 6 times for the price of gasoline compared to the natural gas coming to your house (for a unit of heat).
Several biomass to power and biomass to liquids companies have gone bankrupt or closed doors in the recent past. Here is one for example.
People just don’t want energy - they want it in an easy usable form and at their beck and call. Wind doesn’t give much energy during the days. Biomass gasification plants have 60-70% availability at the best and pollute the water system with tars.
Its like if I give you a solar charger for free for your cell phone and tell you that you will never ever be allowed to charge your phone from a regular power outlet - will you take this deal ?
The production of urea from coal (via ammonia) is not and will never be a method of sequestering carbon dioxide. You produce significantly more CO2 as products of the gasification and water shift reactions then you can consume in the final Bosch Meiser synthesis.
But it does mean that if you’re advocating for carbon capture (as you are in post 14, where you say there are no limits preventing 100% capture), then you need some other way to do it.
I think I’m probably not being very clear. I don’t think anyone would ever think that hydrogen derived from renewable energy would eventually replace fossil fuels, but a potentially pollution free way to supplement our current energy production I think we should at least look into it.
Even if we were to use CO2 emitting sources to generate the hydrogen and use the hydrogen for either charging car batteries, or to run cars directly we are moving our pollution sources to a centralized location which makes mitigating the effects a more tractable problem.
Sorry, if I was not clear. I am not advocating or not advocating for carbon capture. I am saying it can be done.
There are many metrics for carbon capture. One common one for power plants is % of Carbon captured as percent of carbon used for fuel.
So for 30% carbon capture for a gas fired coal plant, you will need to install a post combustion carbon capture unit that will not only capture the 30% carbon from the plant but also 30% of the carbon needed to run it (circulate the absorbent, regenerate it, compress the produced CO2).
For an existing gas fired power plant - this usually means a derate of its capacity. So say a power plant produced 100 MW and vented 100 units of CO2, will now generate 80MW but will vent 70 units of CO2 (consuming the same amount of Coal).
Making urea on the same lines reduces part of the CO2 that may have been released to air
If your question is about how one can have 100% carbon capture from coal, then the most feasible option is IGCC with carbon capture. In this process, coal is gasified, then shift converted to H2 and CO2 - the CO2 is captured (at high pressure using solvents like selexol or rectisol or amines) and the Hydrogen is burnt in the gas turbine to make power.
The efficiency of this system also decreases as the levels (% ages) of carbon capture goes up and costs keep rising up. There are existing plants with upto 50% carbon capture - for example -read this
You will still have to find a home for the captured CO2. For semantics - CO2 capture in the scientific literature means the separation of CO2 from exhaust into a pure high pressure gas. Storage or sequestration is the word for keeping CO2 in the earth (not the atmosphere) for long terms.
I think you are being very clear. I have 2 good friends and several acquaintances who got their PhDs and then build a career looking into this, all the while knowing that they needed big throughs to make the technology commercial. Here are some of the things that does not work for hydrogen :
1> Fuel cells work great on hydrogen - but they need hydrogen that has to be ultrapure (increases cost of production and efficiency) and they dont have that great life. The result is that some mining companies have fuel cell powered equipment in deep mines (due to safety) and thats pretty much it.
2> Gas turbines do not do great on H2 - since the density is so low. They have to get derated and spend a lot on NOx control since hydrogen burns at high temperatures and produces more NOx
3> Transporting hydrogen is very capital and operating cost intensive. Again - this is primarily due to the low density and energy density of hydrogen.
Urea route certainly does not captures 100% CO2. I was showing in the equations that CO2 capture by urea was possible and has been done before but it is partial CO2 capture.
Urea has a standard heat of combustion of 630 kJ/mol (CO(NH2)2) , Carbon is around 400 kJ/mol. So you’ll be breaking thermodynamic laws if you could convert 100% carbon to urea without putting in external energy
Thanks for the useful info. I can see why it’s probably not the best avenue of exploration right now. I suppose it’s easy to dream of pollution-free cars without thinking of the logistics.
According to Market Place, it’s not a 30 percent CO2 reduction from today’s levels. It’s 30 percent from where the U.S. was in 2005— when emissions were a lot higher. In fact, they’ve dropped 15 percent since then.