Moving towards the Hydrogen Economy of Transportation:

But first to finish up with electric vehicles:

Credit: Michael Goodman KEY COMPONENTS of an electric vehicle are energy storage cells, a power controller and motors. Transmission of energy in electrical form eliminates the need for a mechanical drivetrain. Regenerative braking (inset) uses the motor as a generator, feeding energy back to the storage system each time the brakes are used.

The Key of course is marketing people have to buy the product

• Performance people need to change their driving habits

  heat and airconditioning use are also considerations!

• Range not a problem for in town use. City ordinance to make city limits and internal combustion free zone would clearly help

• Price Probably needs to come down to 10K before people would seriously consider this "glorified golf cart"

• Safety Lightweight materials carbon fiber. High tensile strength but not a Farady Cage (thunderstorm problem!). Also braking is a concern.

• Small mass EV's are a safety concern if everyone else is driving Urban Assault Vechicles.

California Mandate:

• 1998: 2% of all vehicles offered for sale must be zero emission vehicles (meaning electric cars)
• 2003: 10% must be zero emission
• As of Fall 1995 the Mandate has been rolled back

  Some Prototypes:

• Ford Ecostar two-passenger electric mini-van used by Post-Office and UPS sodium-sulfur batteries
• Chrysler TEVan nickel-iron batteries
• $500,000 given to Yosemite to replace diesel buses with electric buses
• $500,000 given to General Motors to loan 50 vehicles to 1000 people nationwide for test drive results

Some Internet Resources:

• NiMH Battery Breakthrough
• Components of Government Program

Energy Density Comparison (KHW/kg)

 Hydrogen ------------------------- 38
 Gasoline  ------------------------ 14
 Lead Acid Batteries -------------- 0.04

At the turn of the century electric vehicles were commonplace (using basically lead-acid batteries). Since gasoline has much higher energy density it quickly dominated the way vehicles were propelled.

In fact, gasoline has one of the highest energy density storage capacities known. This makes it very difficult to duplicate the convenience that gasoline has traditionally provided (e.g. 350 kg of batteries is equivalent to 1 kg of gasoline !).

Clearly, in principle, the stored energy density in Hydrogen represents the most viable solution to gasoline powered transport.

Biggest simple problem Hydrogen is not naturally occuring on the Earth; we have to expend energy to extract it this demands clever schemes.

The question is, are we clever?

Hydrogen as a Secondary Fuel:

While hydrogen is the most abundant element in the Universe on the Earth its mostly found as water.

Hydrogen can be easily separated from Oxygen in water via Electrolysis. This process is about 67% efficient

Burning hydrogen combines with oxygen to form water --> no other combustion products (except for small amounts of nitrogen oxides formed around high temperature combustion zone)

For use as a secondary fuel, Hydrogen needs to be stored as a liquid. (20 K; -253 C).

As a liquid its energy density per unit volume is 1000 times higher.

For a given stored energy requirment, a cryogenic hydrogen facility is much less expensive than a pumped hydro facility

But overall efficiency is 25% cryogenic storage is energy intensive

But, one can make a hydgrogen-oxygen fuel cell Using a catalyst, hydrogen combines with oxygen to make water plus electricity. In the lab, such cells can acheive 85% efficiency but large scale value is unknown and untested although there have been some recent breakthroughs:

Hydrogen Fuel Cells

This animation shows the process that goes on inside an individual fuel cell. The red Hs represent hydrogen molecules (H2) from a hydrogen storage tank. The orange H+ represents a hydrogen ion after it's electron is removed. The yellow e- represents an electron moving through a circut to do work (like lighting a light bulb or powering a car). The green Os represent an oxygen molecule (O2) from the air, and the blue drops at the end are for pure water--the only byproduct of hydrogen power.

Notes:

• To produce power in large amounts, many of these cells are combined into a fuel cell stack.

• there will be some electron loss depending on the work done so the process is not 100% efficient as the animation shows.

• Until recently, a fuel cell stack was difficult and expensive to build.

Advantages of Hydrogen technology and fuel cells

Fuel Cells R our Future

Good overview of different kinds of Fuel Cells

Basic Chemisty of a Fuel Cell:

Anode: 2H₂ --> 4H⁺ + 4e^-
Cathode: 4e^- + 4H⁺ + O₂ --> 2H₂O

---

Overall: 2H₂ + O₂ --> 2H₂O

What about fuel cell yield? This information is hard to find, but GM announced in October 2001 the following specifications:

• Rated Output: 1.75 KWH per Liter of Hydrogen (note this would cost about 25 cents at current KWH prices)

• Fuel Cell Stack weighs 180 pounds and gives continuous output of 100 KW to scale things, your home requires about 2KW of power or therefore 4.5 pounds of Hydrogen full cell stack.

  
  
  
  

  Production of Hydrogen

  Hydrogen is already produced mainly to form ammonia to be used in fertilizer. Hydrogen is extracted from methane and steam to make Carbon Dioxide.

  • Ammonia = NH3
  • Methane = CH4
  • Carbon Dioxide = CO2
  • Water = H20

  Problems with the use of Hydrogen:

• If Hydrogen power provided 10% of our national energy budget, 400 1000 Megawatt power plants operating at 24 hours per day would be required to produce hydrogen via electrolysis and this is larger than 10% of our national energy budget!
  • Electricity consumption in the US grew by a factor of 2.5 from 1970 - 1999. To meet the projected demand, by 2020 would also require about 400 new 1000 Megawatt plants to be built.

• The solution to this dilemma is dedicated hydrogen production in remote locations (see more below).

• Hydrogen is very explosive when mixed with oxygen. In its pure state, it poses no explosive threat so is perfectly safe to ship in pipelines. Can explode when mixed with air at concentrations of 4-75%. The ignition energy for this mixture is also very small and easily generated from a spark of static electricty (Hindenburg Disaster).

  Transport of Hydrogen Gas:

  • use existing natural gas pipelines
  • for a given energy requirement, 3 times as much hydrogen is needed as natural gas
  • but hydrogen has lower density and can be pumped at 3 times the flow rate of natural gas.
  • pipeline systems are very efficient compared to transmission losses over long electrical grids

  Costs/Problems:

  Because of the inefficiency in producing it, hydrogen will always be more expensive than the electricity that produced it, if you do the price comparison at the production site

  But, for situations where customers are 1000 miles away from the production site - it is cheaper to deliver hydrogen through a pipeline system than electricity through the power grid.

  A possible strategy is to build large, sturdy windmills in the Aleutian Island Chain (one of the windiest places on the Earth), for the purposes of producing electricity to make hydrogen from Sea Water. The hydrogen would then be shipped over the pipeline network to customers thousands of miles away.

  A more local possibility is Western North Dakota, where there is no real infrastructure to get grid connected energy out from wind power and this is the windiest place in the continental US.

  In addition, dams on the columbia river often produce extra electricity (which of course is sold on the energy spot market) in principle this extra electricity could be use to make Hydrogen.

  The use of liquid hydrogen as a fuel source has potential (particularly on jet airplanes) but technical problems associated with storage and delivery have not yet been overcome

  Best hope Hydrogen fuel cell technology will continue to improve and soon (3-5 years) individual vehicles will use this as a main fuel source. The Aleutian Island scheme could generate sufficient hydrogen for fuel cells for 50-100 million vehicles.

  However, it is quite unlikely that we will ever see electric production from hydrogen as the economics of the efficiency cycle is against this.