Hydrogen as a possible energy carrier 1

[chalkie]

Hi,

My name is Chalkie from Evansville, In. I sell class 8 truck parts for a living but I am interested in renewable energy and have been since the oil embargo in the early seventies. My son is a ME major so I enjoy talking with him.

I think the hydrogen debate needs to be approached from two positions. One from the hard energy side (fossil) and one from the soft energy side (renewables). When considering the hard side, it seems useless to involve oil and gas since their future is short. The price flunctuation that accompanies every supply glitch illustrates how close the supply is running to the demand. We are on the peak of oil and gas production heading down. Coal however is another story. We have a lot in the states and it is sure to play a roll in our energy future. But converting it to hydrogen at conversion efficiencies of 60 percent (includes geological sequestering) and then converting the hydrogen to electricity in a fuel cell at 60 percent doesnt make sense. This means we disrupt a lot of land to mine coal only to use one third of it. It just doesnt seem very ecologically sound to me. I keep in mind that sequestering is still somewhat experimental and it adds to my doubt.

The soft side of hydrogen doesnt hold much promise to me either. Using solar thermal or photovoltaic energy to convert sunlight at 10 to 15 percent efficiency and then convert that to hydrogen at 70 percent efficiency (electrolysis) and finally convert hydrogen in a fuel cell at 60 percent efficiency is a loss leader. All that conversion to end up with a product that uses more energy to produce than it generates. The more direct soft energy conversions are the only ones that make any sense to convert (wind or hydro) since thier conversion rates are higher.

We here in southern Indiana have no appreciable sunlight, no wind (less than 100 w/s/m), and most of our hydro is developed. Solar power from the Southwest would requere DC transmission to reach Indiana. So would the wind from the Northeast. It seems we have few choices and those choices are even worse when converted to hydrogen. Wood heat is popular here but the conversion factor for photosynthesis
rules out any serious condideration of plants providing energy for the masses.

It seems we are stuck with coal and IGCC for our electrical needs and maybe our transportation needs too. Maybe the battery car that the government tried to push the auto indusrty into will be our salvation.

 

[HydroScope]

whilste everybody seems to think that converting coal to hydrogen is a waste of time, it is not. currently coal is burnt to heat steam to turn a turbine this process is about 40-45% efficient. when you meantion carbon sequestion I feel it will never happen way to expensive and renewable options really look economical when considering it, none the less the cheapest form of carbon sequestion will come from a system that has the flue gas (exhast of power station) at high pressure for easy seperation from other pollutants and eventual pushing under ground of CO2. This actually falls in line with the production of hydrogen from coal, i.e. gasification of coal, where the coal is burnt in a oxygen starved atmosphere with introduced water and CO and H2 is produced, the CO is then introduced to water again in the presents of a catalyst, CO2 and more H2 is produced. The process is already used and is 60-65% efficent of a HHV basis(this would not include geo sequestion which efficiency could be as low as 25%).

gasification of coal gives the oportunity to collect sulfur and use particulate removals now the gas is at high pressure. . . .which is a MAJOR improvement over what we do now. the same goes for oil.

While you are right to seperate the discussion into hydrogen from fossil-fuels and hydrogen from renewable energy. the "HYDROGEN" debate is much more complex, and you may like to look at 1) production 2) distribution 3) storage 4) final use.

for your state/country, your renewable energy, have you considered geothermal activity? such as "hot rock" generation of steam, check this out . . .

http://www.geodynamics.com.au

also you may like to consider the gasification of bio-mass, the same process of gasifying coal except you are growing crops to put in the gasifier. Once again narsty particulates can be taken out and CO2 really doesn't need to be sequested as the CO2 was first taken out of the atmosphere by the crop when it was being grown.

a lot of people seem to get stuck on the idea that the low efficencyof hydrogen production to final use makes it a bad energy carrier. well we don't all drive petrol powered cars because they are the most efficent do we!! if we wanted the most efficent we would go and buy a diesel imediately. . . or better still build a steam powered car. . . so it is obvious there are other factors at play(too many to mention here). . . one of the major one is cost. . . we drive petrol cars even as prices hike up because they are the cheapest available option. . . what if oil and gas kept rising and renwables like wind energy costs kept dropping well bellow the cost of electricty from coal? all the sudden everyone would want to make use of the that cheap renwable energy if only we could distribute it, store it, and use it, where ever when ever. . . . . Hydrogen is just one method of doing this. . . . while there are many techniqical barriers to step over, the biggest is hydrogen storage!! . . .the benifits are huge and it will continue to be tackled.

on the subject of efficiency hydrogen can be used to generate water, heat and electricity, for the sake of arguement here in australia water is precious with the whole of sydney and other major towns and city on water restrictions, thus using the water from the fuel cell for irragation and the heat for hot water in any commerical or residential dewling will put the efficency of hydrogen use well about the 60% you quoted, in fact I know of some projects that have quoted 83% when considering the energy used to heat the water for the commerical building. ;o)

 

[liberty]

I used to think converting coal to hydrogen was a good idea. Carbon sequestration can be much cheaper if you consider cultivating trees for more building materials or simple burial, both trap CO2 in the terrestrial biosphere for at least several decades. Keep that up for 100 years and we would drop the CO2 ppm count for sure. In their carbon accounting, Kyoto-participating countries could easily encourage domestic hardwood production, and use it as credit against their emissions.

Among the many unsolved problems with using H2 as an energy carrier, add the increased nitrous oxide emissions that come from H2 combustion and proton exchange in air. If you think CO2 is a greenhouse gas, wait until nitrous oxide, with 300 times the global warming potential, is released from cars on a global scale. And how well is nature geared up for re-absorbing nitrous oxides? Far less efficiently than she can handle CO2. And remember that burning hydrogen from coal means you are making new water with fossilized hydrogen and the oxygen we breathe, then dumping it into the atmosphere. Water vapor is the most prominent greenhouse gas. Given, more water vapor means more white cloads that reflect solar radiation, but we don't entirely understand the positive feedback loop that exists with the hydrologic cycle. Maybe temperature is balanced while new water vapor is just converted to ocean water, but wasn't rising ocean levels an initial concern with CO2 emissions?

Petroleum will be the economic fuel of choice for decades to come, and geopolitical forces may necessitate we soon pay for better ways to use coal-generated power, and cleaner ways to burn our coal (Gasification is good). In the meantime battery and supercapacitor technology will advance so that by the time petroleum runs out or is made obsolete, the hydrogen economy will have to wait for yet another fossil fuel to deplete, which will take hundreds of years. Better encouragement of carbon sequestration is key, and if you can plant a tree you can sequester carbon.

 

[HydroScope]

NO3 is 300 times CO2 in trapping heat and is not caused by the combustion of fuel by a internal combustion engine N02 is. these are easily controlled by a catalitic converter, because of other fuels in ability to lean burn, they will produce tonnes of NOx before the catalyst is warm and continue as car is driven, hydrogen can lean burn producing zero NOx until catalyst effective cutting NOx emission by a MASSIVE amount,

what is proton exchange in air?

of course if we are useing FC's for transport and stationary then NOx is not produced at all. not even in SOFC the highest temp fuel cells, the production of NOx is Temp dependant and happens above 1900oC SOFC operate at 800oC.

trees and other natural phenomenon already produce NO3 NO

while battery and super capacitors have the ability to compete with hydrogen, battery technology already lacks behind the early prototypes of FC powered cars. super capacitors lack behind the best lithum Ion batteries by 1000 fold when considering energy density. you don't need to recharge a fuel cell or ICE overnight otherwise electric vehicles would already have made an impact, they are too heavey with small range and take a long time to recharge. at least current FC vehicle don't take a long to recharge one step forward, plus FC's of future hold a lot more potential, batteries are pretty much at their end of development.

 

[chalkie]

I thought sequestering CO2 took just 3 percent more of the input energy of coal than gasification. Am I wrong?

What is the experiance of the efficiency in the past?

In Indiana, the only soft energy we have available is wind from the east coast. We have tried geologic heat with poor results. (Not enough heat for large scale generation)
It seems the only local choice is coal in one form or another. This will undoubtedly mean gasification but to what? Maybe methanol or hydrogen. If we used a carbon liquid for transportation, the GHG would be acceptable providing we sequester the stationary sources. THis would fit the existing infrastructure for fuel distribution.
Maybe using the hydrogen from gasification and converting it to ammonia would provide a carrier for hydrogen. Its easy to crack on board and works well in a alkaline FC.