Robert,
We see so much claims of numbers in producing hydrogen, so we do not know what to believe. It is good, because it might be a chance here. My point is really not the exact numbers, this will be disclosed and more exact soon. It is the stage of the technology. How I turn this issue, I can not get it to be a "ready for use" technology. That means that it is at least 40-50 years to common use. HEV and EV will be ahead of that and probably fuels cells for ethanol or other fuels. But before this vehicle types are commonly in use, it is at least 30 years. Common use of biofuel could be as soon as 10 to 20 years. I am not taking very strong position on the final suitability of different fuels, it is difficult to predict. I am applying the criteria "ready for use" and then the timing questions. This is because my feeling of urgency to get renewable alternatives in place. Almost every day now, we get energy use estimates and it starts to be an uncomfortable and large difference between the demand projections and the projections of what is possible to produce. The difference must at the end be consolidated and the question is how? My point is that we cannot wait, we must start to play on the strings that we have and we better make good music otherwise the public will kill us. Hakan At 02:48 PM 1/5/2003 -0800, you wrote: >Hakan Falk wrote: > > > Hi MM, > > > > The number they give for hydrogen is 10%, you get 100 and put in > > 90 in the electrolyses. This is a single step process and if you > > define efficiency as "from well to wheel" and use hydrogen as energy > > source for process, you get 0.25% assuming fuel cells with 50% > > efficiency. (Only need to know how to multiply -:) ) > > I think your figures are "deflated". Hydrogen isn't ideal as an energy >carrier, but it isn't THAT bad! A kilogram of H2 (roughly equal to a >gallon of >gasoline, in terms of energy content) electrolyzed at 100% efficiency would >require 31.6 kWh of electricity to produce. The commercial units produced by >Stuart Energy, for instance, claim roughly 59 kWh (this includes >compression and >all auxiliary equipment) per kilogram. Doing the math, this works out to an >overall generating efficiency of 54% for H2 @ 100 atmosphere pressure. > > see: http://www.stuartenergy.com/main_trans.html > > and > > http://www.stuartenergy.com/main_tech.html > > > Now, let's burn this H2 in an internal combustion engine. We will > get about >20% efficiency, assuming the engine hasn't been optimized for hydrogen, >meaning >that from the electrical current required to generate the hydrogen >initially to >the force propelling wheels down the road, the efficiency is about >11%. Lead acid >batteries beat this by a whopping margin. > > But, if we were to burn this H2 in a fuel cell, the situation differs >radically. Since the gas is already compressed, and there is no energy >penalty >for reforming, a typical PEM fuel cell can deliver 80% efficiency. All of a >sudden, we're at 43% efficiency at regenerating current, with probably a >15% loss >for motor and wiring, leaving us with 28% overall efficiency--which is >much better >than most gasoline engines can deliver, but still less than the "average" >diesel >can do. (Though a dedicated, constant speed, direct injection H2 engine might >come dangerously close to this as well!) > > That's why the media and H2 enthusiasts are hyped up about hydrogen. The >trouble is, however, from whence will the hydrogen come? Even with a fuel >cell, >I'd be much better off storing the original electrical energy in lead acid >batteries, so I'd only have to generate HALF the current necessary to >propel my >vehicle down the road. > > The serious hydrogen proponents, people with an even greater belief > in the >viability of hydrogen as an energy carrier than I possess, argue that mass >produced solar thermal gen sets can generate electricity in excess of what is >required for current grid needs. This excess can be shunted to mass produced >electrolyzers that will split water, producing hydrogen for "fuel" and >oxygen for >industrial or medical use. Further, using thermal processes involving >transition >metals, where electrical current is used only for breaking the oxidant >layer on >the tip of the anode, hydrogen can be generated at higher thermodynamic >efficiencies than is possible with classical electrolysis. The high >temperatures >(something like 900 Celsius) would be created using concentrated sunlight. > > Such technology already exists, but it's expensive. This is where mass >production is required to bring the price of the gen sets and >electrolyzers down >to an affordable level. I've read one analysis (this must be fifteen >years ago >already!) that suggested an investment of something like $40 billion would >enable >to U.S. to become a net energy exporter! If we had leadership in this >area, such >an investment, although considerable, is well within reasonable for the >American >economy over a ten year period of time. (Don't we already spend that much >parking >aircraft carriers off of other nations' coastlines and dropping bombs on >people?) > > The trouble with hydrogen from the auto maker's perspective, is that > they're >EXPECTING the hydrogen to be made from reformed hydrocarbons--a difficult >task to >do "on the fly". Further, even PEM fuel cells running on pure H2 can >"choke" on >their waste. There's a very delicate balance that needs to be maintained with >respect to humidity on the PEM surface. If it's too dry, the reaction won't >work. If it's too wet, the reaction STOPS working. I learned somewhere that >Ballard "solved" this problem by blowing compressed air over the membrane and >using some of the methanol reformer heat to keep the PEM at optimal >temperature >and humidity. All of that processing reduces efficiency, creates >complexity, and >increases cost. > > Personally, I don't expect fuel cells for transportation applications to >become affordable in my lifetime. We can come very close to fuel cell >efficiency >running a hydrogen fueled internal combustion engine with direct injection at >constant speed, driving a generator. That's the only way I can foresee >hydrogen >making inroads as a transportation energy carrier. > >robert luis rabello >"The Edge of Justice" >Adventure for Your Mind >http://www.1stbooks.com/bookview/9782 Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
