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Student's Guide to Alternative Fuel Vehicles



Fuel Cell Vehicles - the ZEVs of the future?

Another type of Zero-Emission Vehicle is the fuel cell powered vehicle. When the fuel cells are fueled with pure hydrogen, they are considered to be zero emission vehicles. Fuel cells have been used on spacecraft for many years to power electric equipment. These are fueled with liquid hydrogen from the spacecraft's rocket fuel tanks.

Fuel cell vehicles turn hydrogen fuel and oxygen into electricity. The electricity then powers an electric motor, just like electricity from batteries powers the motor of an electric vehicle. Fuel cells combine oxygen from the air with hydrogen from the vehicle's fuel tank to produce electricity. When oxygen and hydrogen are combined they give off energy and water (H2O). In fuel cells this is done without any burning (combustion). A graphic showing how a typical fuel cell works is shown below.


When we think of vehicles that are fueled with hydrogen, we may think of rocket-powered spacecraft, like the space shuttle. The space shuttle is fueled with liquid oxygen and liquid hydrogen. To fly, the oxygen and hydrogen are mixed together and ignited to make a very hot fire. The expanding gases from that fire are what propel the spacecraft. The exhaust from spacecraft rocket motors (and hydrogen-fueled fuel cells) is mostly water. That is why hydrogen-fueled fuel cell vehicles are also ZEVs. Very little is in the exhaust except water. Fuel cells do get hot though, so the water comes out of the fuel cells as water vapor, or steam.

There are a number of ways that hydrogen can be provided to the fuel cell. One way is simply to put hydrogen gas into the fuel cell, along with air. Hydrogen gas can come from gaseous or liquid hydrogen stored on the vehicle.

To carry gaseous hydrogen on a vehicle, it must be compressed. When compressed (usually to a pressure of about 3000 pounds per square inch), it must be stored in special high-pressure containers. This is similar to the way compressed natural gas is stored on natural gas-fueled vehicles.

The other way to provide hydrogen gas to the fuel cell is to store it on the vehicle in liquid form. To make hydrogen liquid, it is chilled and compressed. Liquid hydrogen is very, very cold--more than 423.2 degrees Fairenheit below zero! This super-cold liquid hydrogen is the kind used in space rockets. The containers are able to hold pressure, but they are also insulated to keep the liquid hydrogen from warming up. Warming the liquid, or lowering the pressure, releases gas (like boiling water), and the gas can go to the fuel cell.

Another way to get hydrogen to the fuel cell is to use a "reformer". A reformer is a device that removes the hydrogen from hydrocarbon fuels, like methanol or gasoline. When a fuel other than hydrogen is used, the fuel cell is no longer zero-emission, but it still may be very low emitting.

There is also a type of fuel cell that can be fueled with methanol directly. This is called a direct-methanol fuel cell. This type of fuel cell does not need a reformer to separate the hydrogen from the methanol. The fuel cell removes the hydrogen from the liquid methanol inside the fuel cell.

Many people in the vehicle manufacturing business think that fuel cell vehicles may be the technology of the future. However, a lot of work will have to be done to make fuel cell vehicles perform well enough to replace the internal combustion engine in the vehicles we use today. They also will need to be made much less expensive.

At present, fuel cell vehicles have only been developed to what might be called the pre-prototype stage. That means there are very few fuel cell vehicles in existence, and all of them are actually used for testing. Most car manufacturers have or are working on demonstration models, some of which can reach a speed of 90 mph and can travel up to about 280 miles before they need refueling. DaimlerChrysler has developed the NECAR 4 (pictured above) and Ford calls its demonstration model the P2000 Sedan. Some manufacturers claim they will have fuel cell cars available for the public in the next ten years.

Find out more about fuel cell vehicles by going to the California Fuel Cell Partnership web site called Driving the Future.

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Introduction

Energy is one of the most fundamental parts of our universe.
We use energy to do work. Energy lights our cities. Energy powers our vehicles, trains, planes and rockets. Energy warms our homes, cooks our food, plays our music, gives us pictures on television. Energy powers machinery in factories and tractors on a farm.

Energy from the sun gives us light during the day. It dries our clothes when they're hanging outside on a clothes line. It helps plants grow. Energy stored in plants is eaten by animals, giving them energy. And predator animals eat their prey, which gives the predator animal energy.

Everything we do is connected to energy in one form or another.

Energy is defined as:


"the ability to do work."

When we eat, our bodies transform the energy stored in the food into energy to do work. When we run or walk, we "burn" food energy in our bodies. When we think or read or write, we are also doing work. Many times it's really hard work!

Cars, planes, light bulbs, boats and machinery also transform energy into work.

Work means moving something, lifting something, warming something, lighting something. All these are a few of the various types of work. But where does energy come from?

There are many sources of energy. In The Energy Story, we will look at the energy that makes our world work. Energy is an important part of our daily lives.

The forms of energy we will look at include:


Electricity
Biomass Energy - energy from plants
Geothermal Energy
Fossil Fuels - Coal, Oil and Natural Gas
Hydro Power and Ocean Energy
Nuclear Energy
Solar Energy
Wind Energy
Transportation Energy

We will also look at turbines and generators, at what electricity is, how energy is sent to users, and how we can decrease or conserve the energy we use. Finally, we'll look at the "newer" forms of energy...and take a look at energy in the future.
You can start with Chapter 1: Energy - What Is It? by clicking the link below. Or you can go to any of the other chapters.


The Energy Story - Table of Contents
Introduction
Chapter 1: Energy - What Is It?
Chapter 2: Electricity
Chapter 3: Static Electricity & Resistance
Chapter 4: Electrical Circuits
Chapter 5: Stored Energy & Batteries
Chapter 6: Generators, Turbines and Power Plants
Chapter 7: Electricity Transmission System
Chapter 8: Fossil Fuels - Coal, Oil and Natural Gas
Chapter 9: Natural Gas Distribution System
Chapter 10: Biomass Energy
Chapter 11: Geothermal Energy
Chapter 12: Hydro Power
Chapter 13: Nuclear Energy - Fission and Fusion
Chapter 14: Ocean Energy
Chapter 15: Solar Energy
Chapter 16: Wind Energy
Chapter 17: Renewable vs. Nonrenewable - Environment & Air Quality
Chapter 18: Energy for Transportation
Chapter 19: Saving Energy and Energy Efficiency
Chapter 20: Hydrogen and Energy In Our Future
Conclusion