Fuel Cells
Fuel Cells
Introduction to Fuel Cell technology and its benefits and disadvantages
transport | electronicsA
fuel cell is a device which converts hydrogen gas and oxygen into water via a process which
generates electricity. This electricity can then be used to power a car more efficiently than existing battery technology, or to power other motors, lighting, and so on - in fact anything that can use direct current (DC) voltage. Most fuel cells produce 0.7-1.2 volts of electricity, and so a
stack of fuel cells must always be assembled to increase the voltage up to a more useful level.
The most promising
fuel cell technology for powering vehicles are
Proton Exchange Membrane Fuel Cells or (PEMFC). The proton exchange membrane separates the cathode (negative) from the anode (positive) only conducting positvely charged ions, and blocking electrons. A rough platinum coated catalyst faces the proton exchange membrane. Pressurised hydrogren gas is pumped into the anode side of the fuel cell where it passes through the catalyst. The hydrogen molecules split into two positive hydrogen ions and two electrons. At the same time oxygen gas (within air) is pumped through the catalyst where it two splits into two positive ions. These are very attractive to the hydrogen ions which then pass through the proton exchange membrane and unite with oxygen ions to form water - one water molecule from two hydrogen ions and one oxygen ion. The electons from the hydrogen now go out through the anode to an external circuit (e.g. the motor of an electric car) doing work and then returning to the cathode of the fuel cell. This reaction generates around 0.7 volts of electricity.
Typically the hydrogen is obtained from a hydrogen filling station in liquid form, and the oxygen is obtained from the air which is pumped into the cathode. Sadly the hydrogen is usually formed by converting a hydrocarbon (fossil) fuel or alcohol. Hydrogen is very difficult to distribute and store, and it is also difficult to carry it in a car. Therefore an alternative is to fill a tank in the car with methanol and then use a so called
reformer to convert it into hydrogen (plus waste products) as and when it is required. Only around 30% of the energy contained by the methanol is actually used to power the vehicle, and there are mechanical losses too resulting in an overall efficiency of a methanol powered fuel cell car to only 25%.
The overall reaction for a
direct methanol fuel cell is:
2 CH3OH + 3 O2
--> 2 CO2 + 4 H2O
As you can see, this reaction releases water (good) and waste heat, and carbon dioxide (bad). However as methanol is a great hydrogen carrier, it is seen as the best hope for fuel cell powered vehicles. Also, miniature versions of methanol fuel cells are not being introduced to power mobile phones, laptops, and other battery hungry electronic devices.
Article Last Modified: 12:20, 21st Apr 2006Comment on this Article
If you have any comments on this article, please email them to
neil@reuk.co.uk.
Recommended Related Articles
People who read this article also enjoyed the following articles:
What Are UltracapacitorsFind out about ultracapacitors - how they work and what they are used for.
Article Last Modified: 16:38, 15th Dec 2008storage | electronicsLow E Double GlazingFind out more about the benefits of low-emissivity (low-E) glass
Article Last Modified: 15:55, 24th Nov 2009energy efficiency | carbon | generalMR11 and MR16 12v Spotlight ConnectorsWiring for 12 volt LED spotlights
Article Last Modified: 11:40, 31st Mar 2007lightingUK Renewable Energy Degree CoursesStudy renewable energy at university in the UK
Article Last Modified: 11:18, 29th Oct 2009education | generalHonda FCX Fuel Cell Concept CarThe latest information about Honda's FCX hydrogen fuel cell powered car
Article Last Modified: 10:21, 2nd Feb 2007transportRainwater Toilet Flush SystemFind out how to put together a complete rainwater fed toilet flushing system
Article Last Modified: 15:16, 19th Aug 2008water | general | electronicsLED SpotlightsFind out about Energy Efficient LED spotlights
Article Last Modified: 14:31, 29th Jul 2008lightingDrying Clothes IndoorsTips on drying clothes indoors without a tumble drier
Article Last Modified: 15:57, 29th Oct 2009energy efficiency | generalBattery System MonitorFind out how to monitor your renewable energy system battery bank
Article Last Modified: 20:28, 30th Mar 2006electronics | storageBasic Ammeters and VoltmetersFind out how to monitor the health of your RE system's generator and batteries
Article Last Modified: 18:17, 26th Feb 2007electronics | storage | wind | solar
|
|
|
