evnow said:
So, what is the new graph instead of Bossel's oft-quoted one from above ? Has it gone up from 23 kWh to 30 kWh or to 70 kWh ?
That's what I want, so I tried to dig out numbers myself. I began with web searches restricted to MNL since it was suggested all the post-2006 numbers have been discussed here. I searched for each of the terms used in Bossel's calculations, with several plausible variations e.g. "transport" and also "distribution." Maybe they are here somewhere but I couldn't find them. Indeed the few numbers I did find were somewhat less optimistic than those used by Bossel.
So I widened my web search, and tried to favor sources that seemed more authoritative, e.g. US EPA instead of someone's blog. Data sources are listed below. Taking the most optimistic values I recalculated Bossel's numbers.
AC-DC conversion: Was 95%, now 98%
Electrolysis: Was 75%, now 80%
For compressed H2...
Compression: 90%
Transport: 80%
Fuel Cell: Was 50%, now 70%
Vehicle: 90%
For liquid H2...
Liquefaction: Was 65%, now 69%
Transport: Was 90%, now 98%
Fuel Cell: Was 50%, now 70%
Vehicle: 90%
Result. Compressed H2 FCEV efficiency was 23%, now 36%. Liquid H2 FCEV efficiency was 19%, now 33%. Impressive improvements if all the technologies cited are commercially viable, but still well short of 69% efficiency for a BEV.
AndyH said:
the esteemed expert starts with renewable AC, though PV outputs direct current. Maybe he's storing wind.
The first point we've evolved is compression. We now have electrolyzers that 'electrochmically' compress H2 to just over 400 bar at the PEM - no pumps needed. Local production eliminates transport/transfer.
I think that Andy's key point is that H2 generation will be distributed. If we have home H2 generation serving a single car from solar panels then it doesn't have to be grid tied so it doesn't have to be AC, we don't need to store large amounts of H2 for a long time, and we don't need to transport it. So calculate with no losses from AC-DC conversion and transport. Also assume his solar panels produce the H2 already compressed to the pressure needed for FCEV storage and assume zero compression losses. Then the bottom line efficiency is 47%.
H2 stations like gas stations would need storage to serve varying possibly large numbers of customers, and would need off-site production and transportation. So driving FCEV's in the future could be somewhat like driving BEV's today. Our first miles of the day are with cheap overnight electricity (H2) in our garage, after which additional miles are driven with expensive QC electricity (H2) from public stations.
So the next interesting discussion could be the commercial viability of small scale distributed H2 generation as Andy outlines. Then it's a tradeoff among vehicle price, home charging/filling station cost, reliability, operating cost, range, public refill cost and availability and convenience.
AndyH said:
At the bottom the BEV gets to use regen but the FCEV doesn't?
Bossel took 90% vehicle efficiency for both FCEV's and for the BEV so he was clearly including regenerative braking for all vehicles even though he neglected to repeat it in the captions.
I still have questions about the fuel cell efficiency. Joseph Romm points out that the fuel cells which are most efficient are those least suitable for use in a vehicle due to weight and high temperature operation. But then he wrote in 2004. Perhaps Andy will tell me it has all been answered somewhere in the 600 page MNL hydrogen thread. Or in a web search I'll find a dozen conflicting statements from people of varying degrees of authority.
Most likely if there are highly efficient automotive fuel cells they're not written about but kept under tight wraps at Toyota and Honda. When they start selling a few compliance FCEV's and independent engineers get close looks at the vehicles then we'll find out whether their secrets were their advanced fuel cells, or their advanced marketing spin to ward off clean air regulators.
Web searches for efficiency data post-2006.
===== AC-DC conversion
MNL: hundreds of matches, none evidently addressing conversion efficiency
http://www.power-mag.com/pdf/feature_pdf/1310569074_Teslaco_Feature_Layout_1.pdf" onclick="window.open(this.href);return false;
Date: 2011
Author: Slobodan Cuk, President TESLAco
98%
===== Electrolysis
MNL: none
http://www.greencarcongress.com/2013/07/itmpower-20130722.html" onclick="window.open(this.href);return false;
Date: 2013
Author: uncredited, Reporting on ITM Power
Each stack is now able to generate up to 27.9 kg/day at full load at an efficiency of greater than 77%.
http://www.greenoptimistic.com/2010/05/19/gridshift-electrolysis-catalyst/#.U3au04G7mAk" onclick="window.open(this.href);return false;
Date: 2010
Author: Ovidiu Sandru, reporting on GridShift Inc., funded by Khosla Ventures
The result is an electrolyzer running as a full cell at 1000 milliamp per cm2 at 80% energy efficiency
===== compression
http://www.mynissanleaf.com/viewtopic.php?p=333585#p333585" onclick="window.open(this.href);return false;
Poster: GRA
Source: none
IIRR it's something like 10-15% of the energy in the H2, and around 15-20% for 10,000 PSI
===== compressed H2 transport
MNL: none
===== fuel cell
http://www.mynissanleaf.com/viewtopic.php?f=13&t=16509" onclick="window.open(this.href);return false;
a good fuel cell can achieve 55% thermal efficiency
Poster: donald
Source: none
http://www.epa.gov/otaq/fuelcell/basicinfo.htm" onclick="window.open(this.href);return false;
Fuel cells can achieve 40 to 70 percent efficiency
Source: US EPA
Date: 2012
http://www.c2es.org/technology/factsheet/HydrogenFuelCellVehicles" onclick="window.open(this.href);return false;
High energy efficiency of fuel cell drivetrains, which use 40 to 60 percent of the energy available
Source: Center for Climate and Energy Solutions
Date: 2014
===== liquefaction
MNL: none
http://ntnu.diva-portal.org/smash/record.jsf?pid=diva2:611686" onclick="window.open(this.href);return false;
Date: 2013
Author: Krasae-in, Songwut, Norwegian University of Science and Technology
The problem is that today every H2 liquefaction plant has low exergy efficiency of just between 20–30%. ... The efficiency of the proposed system is around 45% or more
http://www.ika.rwth-aachen.de/r2h/index.php/Date" onclick="window.open(this.href);return false;: 2008
Source: Aachen University
Liquid_Hydrogen_Transport_by_Truck
liquefaction consumes more than 30% of the energy content of the hydrogen
[So let's assume it consumes 31%, for efficiency of 69%]
===== liquid H2 transport
http://www.ika.rwth-aachen.de/r2h/index.php/Liquid_Hydrogen_Transport_by_Truck" onclick="window.open(this.href);return false;
Date: 2008
Source: Aachen University
a liquid tanker being able to carry up to ten times the volume of an equivalent gaseous tube trailer (up to 4000kg for liquid, compared with 400 kg for gaseous)
[So let's assume that if transport of compressed hydrogen costs 20% of its energy then transport of liquid hydrogen costs only 2% of its energy]
