When it comes to using hydrogen as a fuel, one of the big issues is on-board storage. Most companies working on hydrogen application for cars are using compressed hydrogen gas because they don't have to deal with the issue of keeping the gas at cold temperatures to prevent boil-off. Liquid hydrogen has three time the density of compressed gas, but it must be kept below -252C. Until now, the insulated liquid hydrogen tanks have not been designed to contain the pressure of compressed gas and have had to vent off the gas as the hydrogen warms.

A team at Lawrence Livermore lab has now developed a carbon-fiber wrapped and better-insulated tank that can take either gaseous or liquefied hydrogen. The new tank design has passed safety tests including impact and flame tests. When installed in a Toyota Prius modified to run on hydrogen, compressed gas gives it a range of 80 miles. If it's filled with liquid hydrogen the range goes to 200 miles. The thermal performance has improved from venting fuel vapor after 3-4 days to going at least 6 days and perhaps as much as 15 days. Unfortunately, even 15 days really isn't particularly good. While the extra density of liquid hydrogen is desirable, it simply doesn't seem like a very viable option.

[Source: Lawrence Livermore Laboratory, via EcoGeek]

In the race to bring hydrogen-fueled cars to market, virtually every manufacturer has settled on the compressed gaseous form with one notable exception. BMW has been the lone holdout for the use of liquid hydrogen. BMW's rationale is that liquid hydrogen is more dense than hydrogen gas, even when compressed to 10,000psi. Unfortunately getting hydrogen into liquid form, requires chilling it down to -282.57C -252.87C. Keeping it at that temperature requires a lot of insulation and hence a very bulky storage tank. Nonetheless, insulation is not perfect and the liquid hydrogen still warms up over time and boils. The vapor hydrogen then has to be vented to atmosphere. A BMW Hydrogen 7 left sitting for a week will end up with an empty hydrogen tank.

BMW has been working with a consortium of 34 automakers, aerospace, fuel companies, and universities for the past four and a half years to develop a new storage system for liquid hydrogen. The current cylindrical steel tanks are both heavy and challenging to package in a car and end up absorbing most of the trunk space. BMW's research and development arm Forschung und Technik, along with the consortium, has developed a new composite modular design that can be formed into different shapes allowing greater packaging flexibility. The new tank is claimed to be one third of the weight of the current tank design. It's not known if the new tank does anything to address the issue of fluid boiling. BMW will display the new tank at the StorHy conference in Poissy, France this week.

[Source: BMW]

Earlier Jeremy wrote a post referencing a Detroit News article about a panel discussion on Policies and Issues Affecting Consumer Choices of Vehicles and Fuels at the SAE World Congress in Detroit. I attended that discussion along with several others and wanted to share my own thoughts on it. One consistent theme amongst most of the car-maker representatives on the various panels was that there is no silver bullet that will solve the problems we face. Our future will include a diverse array of fuels and energy sources and drive systems, although the consensus seemed to be that the drive systems will migrate toward electrification.

The notable exception to this seemed to be BMW. In spite of their involvement in both the two-mode and mild hybrid systems with DaimlerChrysler and GM, they seemed to be lukewarm to hybrids. Given the actual real world benefits of parallel hybrids, this may not actually be such a bad position. Instead, short term, they seem more interested in start-stop systems and electrification of accessory drives combined with some limited regen braking capability. These systems are being introduced this year on the 1, 3 and 5 series models. The full hybrid systems won't be coming for another 2-3 years at the earliest.

Continue reading after the jump.