With the goal of affordable hydrogen fuel for vehicles, our Washington State University team is developing a completely new refueling system. Instead of compressing hydrogen directly, as is common and expensive, we cool it to liquefaction. When this boils, it reaches a pressure suitable for refueling vehicles. This allows for the use of a much smaller compressor.
The crux of our station is our patent pending cooling system. Hydrogen gas is produced via electrolysis, steam methane reformer, or biomass extract. Then, instead of 10,000 psi, our compressor uses only 200 psi to force the gas through a nitrogen bath until it reaches 77K (-321°F). Vortex tubes and catalysts liquefy hydrogen for storage. There, it will naturally boil off to a pressure of over 700 bar (10,000 psi), ready for dispensing. Simple modifications would even allow for liquid hydrogen dispensing.
Our WSU H2 Refuel team makes use of a recycled shipping container to house all components, making the device easily movable and modular. To make high purity (>99.995%) hydrogen on site, our system only needs electricity along with water, methane, or biogas.
Our designs for a hydrogen liquefaction system revolve around two main components: our patent pending vortex tube technology and our patent pending cryogenic thermal compression dispensing; reducing the number of moving parts necessary for operation. The process starts with ultra high purity hydrogen (>99.995% hydrogen) created via hydrogen generator or steam methane reformer with a pressure output of about 200 psi. This hydrogen flows through a liquid nitrogen bath for pre-cooling to 77 K before entering the vortex tube where the cold end supplies hydrogen close to liquefaction temperature and the hot end is recirculated into the main system. The cold hydrogen flows through a catalyst bed heat exchanger, expands through a J-T Valve, and is stored as liquid in the designated storage tank. Once stored, the liquid hydrogen is allowed to boil, achieving the necessary pressure of 700 bar (10000 psi) for dispensing.This design eliminates the need to compress fuel to the dispensing pressure, as it occurs naturally during hydrogen boil off.
WSU H2 Refuel is utilizing patent protected vortex tube technology to produce super cooled hydrogen at record setting efficiencies. The following lists a few ways in which our system is superior over those already in progress:
- Hydrogen catalysing vortex tube
- First useage of a catalyst lined vortex tube use in hydrogen liquefaction
- Catalyst converts between two hydrogen energy states to improve overall liquefaction efficiency
- Movable dispensing unit
- Entire liquefaction process will be housed inside a shipping container for easy movement if necessary
- Modular unit for easy upgrades and repairs
- Biomass source
- Can extract hydrogen from excess biomass
- Carbon negative process
- On site production
- Dispensing unit attached to production system
- Reduced compressor requirements
- Most station compressors must operate at 10,000 psi, ours only needs 200 psi
- Smaller, simpler system reduces maintenance
We are participating in the 2016 H2-Refuel competition to create a hydrogen refueling station. The key competition requirements are as follows:
- Station must operate at 700 bar or higher
- Must dispense (fill up a tank) 50 times a day in 3 minutes or less per refuel
- Operate effectively 98% of the time
- Cost $5/kg or less to produce
- Cost the user no more than $8 per kg
In order for our system to be viable it must fit inside a 606 cubic foot shipping container that has the ability to be transported to any location. Inputted to our system will be natural gas, water or syngas. The basics of our system are as follows:
- Hydrogen from a source (either excess biomass or water) will be sent through a purification process to get it to an SAE appropriate 99.99% pure hydrogen.
- Next it will be sent through a series of heat exchangers and compressors to lower the temperature and raise the pressure.
- Once the hydrogen has been adequately cooled it will be sent through a liquid nitrogen chiller and a series of vortex tubes.
- The vortex tube is a complex system which separates hydrogen into low and high energy components. The high energy hydrogen will be re-chilled until it is at the low energy state.
- Once the low energy hydrogen leaves the vortex tube in a very cold gaseous state, it will go through another heat exchange process and an expansion valve to produce liquid hydrogen.
- Finally the liquid hydrogen will then be stored in a cryogenic tank, transferred to a dispensing tank and boiled to increase its pressure to 10,000psi before dispensing.
In order for hydrogen to be a viable fuel alternative, a re-fueling infrastructure will need to be implemented. The refueling system that Washington State University is working on can help fill that void in an economical and environmentally friendly way.
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