Presentation on theme: "Fuel Cells Presentation by David Jacobson National Institute of Standards and Technology Technology Administration U.S. Department of Commerce."— Presentation transcript:
Fuel Cells Presentation by David Jacobson National Institute of Standards and Technology Technology Administration U.S. Department of Commerce
Who am I? David Jacobson Physicist Ph.D. 1996 University of Missouri National Institute of Standards and Technology I work at a research reactor in Gaithersburg that uses neutrons to study new materials or parts for scientific and consumer applications. Today I am going to talk about fuel cells. Fuel cells are an example of a system we can study scientifically and provide important information back to industry as to how to better engineer the system.
Overview GM Highwire BBC episode (6 min) www.youtube.com/v/ry6w3mRm-FM www.youtube.com/v/ry6w3mRm-FM Where does energy come from Why hydrogen What is a hydrogen economy What is a fuel cell
Why use hydrogen? Reduce or eliminate emissions of CO 2 a gas produced by burning hydrocarbons that is widely believed to be artificially accelerating global warming. Hydrogen can be produced using energy sources inside the United States allowing us to reduce or eliminate our dependence on importing oil from other countries. Oil based energy sources will eventually run out. Hydrogen is used to produce ammonia used as a nitrogen fertilizer.
Sources for hydrogen Currently made from natural gas (non renewable). Could be made in large quantities from next generation nuclear reactors (non renewable). Could be made by electrolysis of water using wind or solar energy (renewable). Hydrogen is used to store energy for when the sun goes down or the wind stops blowing. SOLARWIND HYDRO-ELECTRIC NUCLEAR REFINED NATURAL GAS
Hydrogen filling station Opened November 2004 A Washington DC Shell gas station on Benning Road sells mostly gasoline but also has one hydrogen pump
Electro-Chemistry 2H +1 O -2 +H2OH2OEnergy+ In a rocket we convert all the energy to heat energy But the fundamental chemical process is electrical, so we could convert the energy into 1.2 volts of electrical energy 2H +1 O -2 +H2OH2O1.2 volts of electrical energy+
What is a fuel cell It is really just a battery We can refill with fuel and that is why it is called a fuel cell. We can recharge it like a battery as well. One cell is like a 1 Volt battery BUT we can easily produce 500 to 1,000 amps of electricity!!! To power a car we need about 100 Volts…What do we do? + - + - Hydrogen Air =
Electricity The flow of electricity is like the flow of water. At high pressure water can cut through steel and concrete. That same water you could drink if you poured it from a cup, but at high pressure it can kill you. The pressure behind the water is proportional to the force carrying the water (current) out. In a battery the force on the electrons is proportional to the voltage and the current (water) is the carrier. High voltage and current are necessary to give us a lot of power. An abrasive water jet tool cuts a 0.25-inch-thick stainless steel plate in a single pass.
Volts will add by stacking the batteries 1 Volt is now 100 Volts! 100 Volts at 500 amps = 50,000 Watts of electricity! Now we can power a car
What a real stack looks like Shown here is a Honda fuel cell stack for a vehicle These types of cells are 50,000 to 100,000 Watts! Shockingly powerful!!!!
Regenerative braking Instead of wasting the energy of motion the motor can be switched to the car battery to recharge the batteries. Check out the demonstration motor.
The electric motor A car will use a stack of fuel cells to provide electricity. This stack powers an electric motor that directly drives the wheels. Electric motors have high torque at the front end, unlike mechanical internal combustion engines and so a gear box isn’t required. FC_System.mpg
Fuel Cell Applications Cell phone batteries can be instantly recharged with plug in fuel (Methanol). Household electricity can be generated in your basement or at a remote ski chalet eliminating the need for electrical power lines and avoiding loss of electricity during periods of inclement weather. Electric automobiles can use fuel cells to generate electricity to drive the electric motors that drive the wheels. Fuel cells from your car could easily power a block of houses.
HYDROGEN3 – Opel Zafira – driven in Washington DC, Germany, and Japan
What is the Hydrogen Economy ? Hydrogen produced using renewable processes. Hydrogen produced centrally and piped like natural gas or shipped by truck. Hydrogen can be locally combined with oxygen to produce electricity. Houses are heated and cooled with electricity. Vehicles are electric and powered by hydrogen fuel cells
Fuels Hydrogen Methanol (alcohol that is toxic if consumed). This is only considered for small portable applications like laptops and cell phones.
Forming the Water Molecule Electrons and protons have moved around as we go from 2 separate molecules to one molecule. This process proceeds because it is energetically favorable. 1.2 Volts of energy is liberated. If we are clever we can redirect the motion of the electrons as they are redistributed off into a circuit to power our light bulbs or our cars. Nearly all of the energy we can use up running our electrical equipment instead of loosing the energy to heat like in a rocket engine. Energy H 2, O 2 E=1.2 Volts H2OH2O Energy barrier
Single Cell Assembly Flow Fields Current Collectors Compression Plates Locating Pins Gaskets - GDM - MEA
PEM Fuel Cell Operation Platinum in catalyst is very expensive Membrane conducts protons when wet, but not electrons
Automotive Fuel Leak Simulation Michael Swain University of Miami (available online). Hydrogen flame visible due to special photography.
Components Membrane Nafion proton conductor Catalyst/electrode electron conductor and molecule separators Gas diffusion layer (porous for air flow but conducts electrons) Flow fields allow gases to be distributed over the active area and conducts electrons
Reasons for a Hydrogen Economy Reduce or eliminate emissions of CO 2 a gas produced by burning hydrocarbons that is widely believed to be artificially accelerating global warming. Hydrogen can be produced using energy sources inside the United States allowing us to reduce or eliminate our dependence on importing oil from other countries. Oil based energy sources will eventually run out. Hydrogen is used to produce ammonia used as a nitrogen fertilizer.
Hydrogen is not an energy source It is an energy carrier Electricity is also an energy carrier
Common Misconceptions about Dangers of Using Hydrogen Hydrogen Bomb. I could spontaneously blow myself up and my entire city if I carry around a tank of hydrogen. Hindenburg disaster famous disaster believed by many to be due to a hydrogen fire. Obviously hydrogen is much too dangerous. Apollo 13 was due to a hydrogen fire since this was the volatile rocket fuel that it used.
Reality Hydrogen bombs require an initial temperature found only at the sun or in a thermo-nuclear bomb. Also these weapons use heavier forms of hydrogen, not the protonic form found mostly in nature. These are energies 1 million times that release when hydrogen and oxygen combine. The exact cause of the Hindenburg disaster is still debated. In fact blimps used hydrogen for years without any safety incidents. A starting point for more detailed discussions and links on the Hindenburg disaster scenarios can be found at Wikipedia. The Apollo 13 disaster was due to an oxygen fire. E=mc 2
Space shuttle Aluminum powered solid rocket boosters very visible Note the lack of a visible flame from the hydrogen powered main engines
Properties of Hydrogen Odorless Flame is invisible to the human eye (light emitted in the ultra violet range) Wide flammable range from 4% to 77% mixtures with air. 10 times easier to ignite than natural gas (methane). A 28% mixture is 24 times (by mass) more energetic than TNT if detonated. Extremely buoyant and when released goes up at a velocity of 2-10 meters per second. Lower flammability limit Upper flammability limit
Vehicle propulsion Electric motors Fuel cells Batteries
Current Scientific/Engineering Challenges Lifetime (5,000 to 10,000 hours). One full year is 8760 hours, but a car does not run constantly for a year. Turning the fuel cell engine on and off during those 10,000 hours can reduce efficiency by 50% How do you efficiently store hydrogen on a vehicle Storage tanks must allow one to quickly refill Most cars go 450 km (300 miles) per fill of their gas tank, but this is difficult to do with compressed hydrogen Compressing hydrogen is currently used, but this lowers the overall efficiency making it as good or worse than a gasoline powered vehicle. Platinum is expensive and it is key to making the vehicle work.
Factoid Apollo Saturn V rockets first stage used kerosene-liquid oxygen, only the upper stages used hydrogen and oxygen, therefore the engines burn brightly.