Episode 3
HYDROGEN
UTILIZATION
Green Hydrogen (H2) has many uses, including as a feedstock for chemical processes or in steel production and to generate heat in place of fossil fuels such as natural gas. But of course green H2 can also be used to produce electricity via fuel cells, H2 turbines or in H2 combustion engines.
This episode focuses on the use of green H2 in fuel cell systems.
The hydrogen infrastructure consists also hydrogen-equipped filling stations. Hydrogen refueling stations (HRSs) are key infrastructures rapidly spreading out to support the deployment of fuel cell electric vehicles for several mobility purposes.
HOW A FUEL CELL WORKS
Fuel cell technology is almost 200 years old and its main inventor, Sir William Grove, originally called it a “gas battery”.
Compared to conventional combustion engines a fuel cell can reach higher efficiency when producing electricity. It works by converting chemically bound energy into electricity directly in one step, whereas today’s conventional energy systems are based on a three step process. H2 and O2 create the electric current in the fuel cell and are separated by an electrolyte to avoid an oxyhydrogen explosion.
The reaction takes place at a lower temperature without a flame or a bang. Like electrolyzers, fuel cells are designed as stacks consisting of many single fuel cells to achieve the required power. Fuel cells require a balance of plant system to support stable and efficient operation.
Electric Current
Fuel IN
Air IN
Excess
Fuel OUT
Unused
air, water,
and heat
e -
e -
e -
e -
O2
H2O
H +
H +
H2
Electrolyte
Cathode
Anode
TYPES OF FUEL CELLS
There are several types of fuel cells available in the market using different materials, temperatures and related applications.
The PEM is the most widely used fuel cell type and is likely to remain as the main technology in the near future.
Source: hydrogenandfuelcells.energy.gov
FOCAL-POINT: OPTIMIZED HEAT EXCHANGE IN THE AIR SUPPLY
SYSTEM FOR PEM FUEL CELL SYSTEMS
Fuel cells can be used to generate electricity cleanly from green hydrogen and air, with water and residual heat as by-products. Achieving a stable and efficient operation depends on a balance of plant system, including heat exchangers.
To ensure a high efficiency in fuel cell systems, keeping the energy consumption at a low level is crucial. One of the main energy consumers in a fuel cell system is the blower or compressor, which supplies fresh ambient air and thus the O2 needed for the process.
READ MORE and DOWNLOAD OUR TECH-PAPER
APPLICATIONS OF FUEL CELLS
Fuel Cells are suitable for portable, transportation and stationary applications.
Portable units mainly have lower capacities of several kilowatts and are generally used in camping equipment and for traffic or defense applications.
In transportation, fuel cells can be used in cars, trucks and buses. Fuel cell systems could also replace conventional technology in planes and on board ships.
Because stationary fuel cell systems have a higher capacity they are suited to back-up and off-grid systems and in residential areas for electricity and heat supply.
In future bigger stationary systems of several 100 kW and up to several megawatts could be a substitute for combined cycle power plants based on reciprocating engines, for example, in hospitals, industrial areas and data centers.
HEAT EXCHANGERS FOR FUEL CELL SYSTEMS
While a fuel cell transfers the chemical energy into electricity in just one step, there are efficiency losses, nevertheless. Electrical efficiencies of approx. 40 - 60 % are usual and achievable. Remaining energy is converted into heat which must be extracted from the process to ensure the fuel cell system operates at the required temperature. Kelvion Heat Exchangers offer manifold product types to achieve this.
Charge Air Coolers
and Condensers
Brazed Plate
Heat Exchanger
Dry Coolers
Gasketed Plate
Heat Exchanger
HYDROGEN COOLER FOR
REFUELING STATIONS
Passenger cars that are running on hydrogen typically fill up their tanks to 700 bar. Compressors in the hydrogen refueling stations bring gaseous hydrogen to an intermediate storage of around 900 bars. When an empty car arrives at the station it is filled into the empty car tank which initially has almost no hydrogen pressure and fills until it reaches 700 bars. Hydrogen has a very strange behavior compared to most gases: when you release it in pressure it will heat up. To avoid that the tank in the car gets too hot, the hydrogen is precooled just before it is dispensed into the car. In most commercial stations the precooling is done to a temperature between -33°C and -40°C in accordance with the T40 protocol in SAE J2601 standard.
The K°BOND diffusion bonded heat exchanger is a perfect solution for this service. It can fulfill the high design pressure of 1050 Barg and can withstand the cyclic behavior. Furthermore, it is so compact that it can easily fit inside the dispenser unit in the refueling stations. Kelvon developed two standard models The HHX-1000 for passenger cars with nominal filling velocity of 60 gram per second and the HHX-2000 for heavy duty vehicles with a nominal filling rate of 120 gram per second and peak rates of 180 gram per second.
Compressor
Booster
High Pressure
Buffer Storage
up to 950 bar
Chiller
K°Bond HHX-2000
Hydrogen Cooler
Truck Onboard Tank
Hydrogen
Supply
Source
Compressor
Compressor
Mid Pressure
Buffer Storage
up to 500 bar
Dispenser
Car Onboard Tank
