Hydrogen Fuel Cell & Photovoltaics. Photovoltaics.

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  • Hydrogen Fuel Cell& Photovoltaics

    Heliocentris: Science education through fuel cells *

  • Photovoltaics

    Heliocentris: Science education through fuel cells *

  • Heliocentris: Science education through fuel cells *

  • PV Cell

    Heliocentris: Science education through fuel cells *

  • Heliocentris: Science education through fuel cells *

  • Conversion Efficiency

    Heliocentris: Science education through fuel cells *

  • PV Array Components

    PV CellsModulesArrays

    Heliocentris: Science education through fuel cells *

  • PV System Components

    Heliocentris: Science education through fuel cells *

  • Net Metering

    Heliocentris: Science education through fuel cells *

  • Net Metering Participation

    Heliocentris: Science education through fuel cells *

  • PV Array Fields

    Heliocentris: Science education through fuel cells *

  • Heliocentris: Science education through fuel cells *

  • Source: Solarbuzz, a part of The NPD Group

    Heliocentris: Science education through fuel cells *







    Photovoltaic Market in 2009, Total 7.3 GW

    Photovoltaic Market in 2009Total 7.3 GW


    Photovoltaic Market in 2009, Total 7.3 GW

    Germany, Italy, Czech Republic68%

    Other Europe9%

    United States7%


    Rest of World10%

    To resize chart data range, drag lower right corner of range.

  • CleanSustainableFreeProvide electricity to remote placesAdvantages of Solar Energy

    Heliocentris: Science education through fuel cells *

  • Disadvantages of Solar EnergyLess efficient and costly equipmentPart TimeReliability Depends On LocationEnvironmental Impact of PV Cell Production

    Heliocentris: Science education through fuel cells *

  • Hydrogen Fuel CellsThe NEED Project: 30 Years of Energy Education

    Heliocentris: Science education through fuel cells *

  • Trends in the Use of Fuel

  • A varied range of organizations, from energy companies to automobile manufacturers, are working to develop fuel cells and the accompanying infrastructure. A trend in the production of power is clearly visible:

  • The History of Fuel CellsElectrolyserGroves Gas Battery(first fuel cell, 1839)(after Larminie and Dicks, 2000)

  • Bacons laboratory in 1955Photo courtesy of University of Cambridge

  • NASA Space Shuttle fuel cellPhoto courtesy of NASA

  • Applications for Fuel Cells Transportation vehicles Photo courtesy of DaimlerChryslerNECAR 5

  • Distributed power stationsPhoto courtesy of Ballard Power Systems250 kW distributed cogeneration power plantApplications for Fuel Cells

  • Home powerPhoto courtesy of Plug Power7 kW home cogeneration power plantApplications for Fuel Cells

  • Portable power50 W portable fuel cell with metal hydride storageApplications for Fuel Cells

  • The Science of Fuel CellsPhosphoric Acid (PAFC)Alkaline (AFC)Polymer Electrolyte Membrane(PEMFC)Direct Methanol(DMFC)Solid Oxide(SOFC)Molten Carbonate (MCFC)Types of Fuel CellsPolymer Electrolyte Membrane (PEMFC)Direct Methanol (DMFC)Solid Oxide (SOFC)

  • PEM Fuel Cell Electrochemical Reactions

    Anode:H22H+ + 2e- (oxidation)Cathode: 1/2 O2 + 2e- + 2H+ H2O (l) (reduction)Overall Reaction:H2 + 1/2 02 H2O (l) H = - 285.8 kJ/mole

  • Hydrogen + Oxygen Electricity + Water WaterA Simple PEM Fuel Cell

  • Membrane Electrode Assembly (MEA)O22H2O4H+Nafion4e-2KH2O2H2O2H24H+Nafion4e-O22H2O4H+Nafion4e-NafionH+CatalysisTransportResistanceAnodeCathodePolymerelectrolyte(i.e. Nafion)Carbon clothCarbon clothPlatinum-catalystPlatinum-catalystOxidationReduction

  • Polymer Electrolyte Membrane(after Larminie and Dicks, 2000)Polytetrafluoroethylene (PTFE) chainsSulphonic Acid50-175 microns(2-7 sheets of paper)Water collects around the clusters of hydrophylic sulphonate side chains

  • Hydrogen Storage56 L14 L9.9 LLiters to store 1 kg hydrogenCompressed gas (200 bar)Liquid hydrogenMgH2 metal hydride

  • Hydrogen: Energy Forever

  • Renewable Energy SourcesAs long as the sun shines, the wind blows, or the rivers flow, there can be clean, safe, and sustainable electrical power, where and when required, with a solar hydrogen energy system

  • Benefits of Fuel CellsModularCleanQuietSustainableEfficientSafeThe Benefits of Fuel Cells

  • Heliocentris: Science education through fuel cells *Our Fragile Planet.We have the responsibility to mind the planet so that the extraordinary natural beauty of the Earth is preserved for generations to come.Photo courtesy of NASA

    Heliocentris: Science education through fuel cells *

    *Photovoltaic systems convert sunlight directly into electricity, and are potentially one of the most useful of the renewable energy technologies.

    Also known as solar cells, PV systems are already an important part of our lives. The simplest systems power many of the small calculators and wrist watches we use everyday.*Elements are arranged in the periodic table such that groups columns of elements have the same numbers of valence (outer) electrons. The valence electrons dictate the chemical behavior of the element.

    Silicon is the most common semiconductor, but germanium is also used. A semiconductor will only conduct electricity under certain conditions, so its more easily controlled than something like copper or silver. Silicon has four valence electrons.

    Boron, like all elements in its group, has only three valence electrons, which means it can easily accept electrons. Phosphorous, like all elements in its group, has five valence electrons, and can easily lose an electron. These two elements make suitable doping materials in photovoltaic cells because of their ability to give up or accept electrons. Doping materials are substances added in small quantities to a semiconductor to create an imbalance, of sorts, in electron distribution.*The photovoltaic cell is the basic building block of a PV system. Individual cells can vary in sizes from about 1cm to about 10 cm across. Most cells are made with silicon today. Silicon must be purified this is one of the biggest expenses in the production of solar cells.

    A slab (or wafer) of pure silicon is used to make a PV cell. The top of the slab is very thinly diffused with an n dopant, such as phosphorous. On the base of the slab, a small amount of a p dopant, typically boron, is diffused. The boron side of the slab is 1,000 times thicker than the phosphorous side. Dopants are similar in atomic structure to the primary material. The phosphorous has one more electron in its outer shell than silicon, and the boron has one less. These dopants help create the electric field that motivates the energetic electrons out of the cell created when light strikes the PV cell.

    The phosphorous gives the wafer of silicon an excess of free electrons; it has a negative character. This is called the n-type silicon (n = negative). The n-type silicon is not chargedit has an equal number of protons and electronsbut some of the electrons are not held tightly to the atoms. They are free to move to different locations within the layer.

    The boron gives the wafer of the silicon a positive character, which will cause electrons to flow toward it. The base of the silicon is called p-type silicon (p = positive). The p-type silicon has an equal number of protons and electrons; it has a positive character, but not a positive charge.

    Where the n-type silicon and p-type silicon meet, free electrons from the n-type flow into the p-type for a split second, then form a barrier to prevent more electrons from moving between the two sides. This point of contact and barrier is called the p-n junction.

    When both sides of the silicon slab are doped, there is a negative charge in the p-type section of the junction and a positive charge in the n-type section of the junction due to movement of the electrons and holes at the junction of the two types of materials. This imbalance in electrical charge at the p-n junction produces an electric field between the p-type and n-type.

    If the PV cell is placed in the sun, photons of light strike the electrons in the p-n junction and energize them, knocking them free of their atoms. These electrons are attracted to the positive charge in the n-type silicon and repelled by the negative charge in the p-type silicon. Most photon-electron collisions actually occur in the silicon base.


    A conducting wire connects the p-type silicon to an external load such as a light or battery, and then back to the n-type silicon, forming a complete circuit. As the free electrons are pushed into the n-type silicon they repel each other because they are of like charge. The wire provides a path for the electrons to move away from each other. This flow of electrons is an electric current that can power a load, such as a calculator or other device, as it travels through the circuit from the n-type to the p-type.

    In addition to the semi-conducting materials, solar cells consist of a top metallic grid or other electrical contact to collect electrons from the semi-conductor and transfer them to the external load, and a back contact layer to complete the electrical circuit.

    It is this flow of electrons that produces electrical current.*The conversion efficiency of a PV cell is the proportion of sunlight energy that the cell converts into electrical energy.

    This is very important because improving this efficiency is vital to making PV energy competitive with more traditional sources of energy, such as fossil fuels.

    The first PV cells were converting light to electricity at 1 to 2 percent efficiency.

    Todays PV devices convert up to 17 percent of the radiant energy that strikes them into electric energy. (40% NREL)*One PV cell only produces 1 or 2 watts of electricity, which isn't enough power for most applications.

    To increase power, groups of solar cells are electrically connected and packaged into weather-tight modules and arrays to provide useful output voltages and currents for a specific power output.

    A PV System typically consists of 3 basic components.

    PV cells - Electricity is generated by PV cells, the smallest unit of a PV system

    Modules - PV cells are wired together to form modules which are usually a sealed, or encapsulated, unit of convenient size for handling.

    Arrays Groups of panels make up an array.

    *Solar PV SystemSolar cells produce direct current (DC), therefore they are only directly used for DC equipment. If alternating current (AC) is needed for AC equipment or backup energy is needed, solar photovoltaic systems require other components in addition to solar modules. These components are specially designed to integrate into solar PV systems. The components of a solar photovoltaic system are:

    Solar Module -- the essential component of any solar PV system that converts sunlight directly into DC electricity.2. Solar Charge Controller -- regulates voltage and current from solar arrays, charges the battery, prevents battery from overcharging and also performs controlled over discharges.

    3.Battery -- stores current electricity produced from solar arrays for use when sunlight is not available.4. Inverter -- a critical component of any solar PV system that converts DC power into AC power.5. Lightning protection -- prevents electrical equipment from damage caused by lightning or induction of high voltage surge. It is required for the large size and critical solar PV systems, which include grounding.

    *A PV system produces DC-current.

    The DC current goes into an Inverter where it becomes AC current.

    An inverter is connected to your homes or buildings electric system, and to your meter.

    You use all electricity needed, while all excess electricity goes into the grid.

    Electricity that goes into the grid is purchased from you by your utility company through Net Metering, usually at retail price.

    While this option is not offered by many utility companies, the number is growing. In 2002, there 4,472 customers who participated in net metering programs. In 2007, there were 48,820 customers using the net metering program.*Source: U.S. Energy Information Administration, Electric Power Annual. Note: The chart counts the number of net-metering customers and does not indicate the generator size or amount of generation. Non-residential includes the commercial and industrial sectors; net-metered generators in these sectors are typically larger than residential generators.

    *In order to generate large amounts of electricity which can be fed into the electric grid, large number of arrays can be wired together to form an Array Field.

    Some utility companies in the U.S. are turning to large PV systems to help meet peak power demand and reduce the need for building new power plants.

    **Photovoltaic systems are ideal for remote applications where other power sources are impractical or unavailable, such as in the Swiss Alps or on navigational buoys. It is not practical to connect these applications to an electric grid. They are also used to power small, independently placed objects, such as billboards and road signs.*Solar energy produces no air pollution, thermal pollution, or water pollution, nor does acquiring solar energy disrupt a natural environment. The sun simply shines whether we use the energy or not. Solar energy is a completely sustainable energy source. Yes, one day the sun will stop producing energy, but if that happens we will have more problems to worry about than how well charge our cell phones! Solar energy is one of the last free resources available to us, and it is available to us in such vast quantities we could never use all of it at any given time. Because the sun shines everywhere, and not just where people are, it can be used in places where electricity may not be otherwise available or practical. *Most photovoltaics are only 17-20% efficient. There are some experimental and developmental technologies being used in laboratories and by the space industry that are more efficient, but even those maximize at 43%. However, no energy is output in delivering the energy source to the PV panel; it is already right there to use, and does not require any initial energy or materials to get it to the site of use.

    Because the sun is not shining constantly all the time in any given location, it cannot be counted on for continuous energy. The amount of solar energy available to an entity depends completely on the latitude, climate, time of day, and amount of air pollution present. Clouds or particulate matter in the air will lessen the amount of solar energy available to use in a PV cell. Higher latitudes do not receive as intense of sunlight as more tropical areas, and therefore will not be able to produce as much power through photovoltaics. All of these limit the degree to which photovoltaics can be used.

    Another negative aspect to using photovoltaics is in the production of the materials in a PV cell. The entire production process does have a negative environmental impact, primarily from the energy required to produce the PV cell. There is a very small amount of heavy metals, such as lead and cobalt, produced in the purification of the materials being used, but that is far outshadowed by the amount of carbon dioxide and other air pollutants produced when the electricity necessary for production is generated. Replacing conventional, fossil fuel based electrical power generation will significantly reduce this impact. Furthermore, because the site of heavy metal toxicity is kept isolated at just production facilities, it can be more closely monitored and regulated than if the materials were more wide-spread.***It is interesting to note that as fuel use has developed through time, the percentage of hydrogen content in the fuels has increased. It seems a natural progression that the fuel of the future will be hydrogen.

    The two principal reactions in the burning of a hydrocarbon fuel are the formation of water and the formation of carbon dioxide. As hydrogen content in a fuel increases, the formation of water becomes more significant, resulting in proportionally lower emissions of carbon dioxide.*A varied range of organizations, from energy companies to automobile manufacturers, are working to develop fuel cells and the accompanying infrastructure. A trend in the production of power is clearly visible:The 19th century was the century of the steam engine,The 20th century was the century of the internal combustion engine, The 21st century will be the century of the fuel cell.

    *The first fuel cell was developed in 1839 by Sir William Grove, a British scientist and lawyer. The principle was discovered by accident. He was performing an electrolysis experiment. When he disconnected the battery from the electrolyser and connected the two electrodes together he noticed that a current flowed in the opposite direction, consuming the gases of hydrogen and oxygen. He called this device a gas battery. His gas battery consisted of platinum electrodes placed in test tubes of hydrogen and oxygen, immersed in a bath of dilute sulphuric acid. It generated a voltage of about one volt.

    However Groves fuel cell was not practical, due to problems of corrosion and instability of the materials. As a result there was little research and development into fuel cells for many years to follow. *Significant development work on fuel cells began again in the 1930s, by Francis Bacon, a chemical engineer at Cambridge University. In the 1950s Bacon successfully produced the first practical fuel cell, an alkaline fuel cell. It used an alkaline electrolyte instead of dilute sulphuric acid. The electrodes were constructed of porous sintered nickel powder so that the gases could diffuse through the electrodes to be in contact with the aqueous electrolyte on the other side. This greatly increased the contact area contact between the electrodes, the gases, and the electrolyte, thus increasing the power density of the fuel cell. In addition, the use of nickel was much less expensive than that of platinum.

    An assistant can be seen in this photograph mounting a plate onto the side of Bacons fuel cell stack. Alkaline fuel cell reactions:Anode reaction: 2 H2 + 4 OH-4 H2O+ 4 e- Cathode reaction:O2 + 4 e- + 2 H2O 4 OH- Overall reaction: 2 H2 + O22 H2O

    *The Bacon fuel cell was modified by NASA in the 1960s as a method to supply on-board drinking water as well as electricity for the astronauts aboard the Apollo space missions. An alkaline fuel cell is still used today in the present day Space Shuttle Orbiter. The Space Shuttle Orbiter fuel cell has been produced since the 1970s by International Fuel Cell, USA. It produces 12 kW electricity, weighs 202 lbs (98 kg), and occupies a space of 4.6ft3 (154 litres). Photo courtesy of NASA

    Alkaline fuel cells offer the advantages of high voltage output per cell (each cell in the Space Shuttle has an operating voltage of about 0.875 volts) and that non-precious materials can be used as electrodes. The primary disadvantage of alkaline fuel cells for terrestrial applications is that of carbon dioxide poisoning the electrolyte. Carbon dioxide, present in both the atmosphere as well as in reformate (the hydrogen-rich gas produced from the reformation of hydrocarbon fuels) reacts with the hydroxide ion in the electrolyte to form a carbonate, thus reducing the hydroxide ion concentration in the electrolyte. This reduction in hydroxide ion concentration inhibits the ability of the fuel cell to generate current.

    Because of the complexity of isolating carbon dioxide from the alkaline electrolyte for terrestrial applications, most fuel cell developers today have focused their attention on developing new types of fuel cells using electrolytes other than that of alkaline.

    Carbon dioxide reacting with potassium hydroxide electrolyte forming a carbonate:2 KOH + CO2K2CO3 + H2O*In the mid-1980s Ballard Power, based in Vancouver BC and working on a contract from the Canadian Department of National Defense, made significant breakthroughs in fuel cells. Working with Johnson Matthey in the UK, they developed PEM fuel cells which had a significant increase in power density. From these breakthroughs it was recognized that fuel cells could be made small, powerful, and inexpensive enough to replace conventional power technologies.

    The California Low Emission Vehicle Program, a program of the California Air Resources Board (CARB) has been a large incentive for automakers to develop fuel cell automobiles. This program requires that beginning in 2003, ten percent of passenger cars delivered for sale in California must be Zero Emission Vehicles, called ZEVs. Automobiles powered by fuel cells meet these requirements. To date seven of the worlds ten leading auto manufacturers plan to introduce fuel cell automobiles beginning in the 2003 2005 timeframe.

    The NECAR 5 shown here is a prototype automobile by DaimlerChrysler. This automobile is fuelled with liquid methanol and has a top speed of over 90 miles per hour (150 km/h). In forthcoming years there are plans for buses, trucks, and trains all powered with fuel cell engines. Thirty buses will be commercially introduced in ten European cities beginning in 2002.

    *Electrical energy demands throughout the world are continuing to increase. In Canada the electrical energy demand is growing at an annual rate of approximately 2.6%. In America the electrical energy demand is growing at an annual rate of about 2.4% (IEA 1997). In developing countries, electrical demand is growing at an annual rate of almost 6% (Khatib 1998). How can these demands be met responsibly and safely?

    There are many problems associated with the building of new power plants, both financial and environmental. Fuel cell distributed power stations provide a solution. Fuel cell distributed power plants can provide high quality, reliable power. Depending on the type of fuel used fuel cell power plants produce little or no emissions.

    Shown here is a prototype fuel cell distributed power plant, recently developed by Ballard Power. This particular unit was commissioned for the BC Hydro grid. It provides 250 kilowatts of electricity and about the same amount of heat, fuelled from natural gas. This is enough power to provide heat and electricity to a community of about 50 homes for example, or to a hospital or to a remote location school. Ballard plans to introduce its first commercial fuel cell distributed power plant as a backup power supply in 2003. *Fuel cell power plants are also being developed by several manufacturers to provide electricity and heat to a single-family home. Fueled by either natural gas or propane these fuel cell power plants will be able to power a home independent of the grid.

    Plug Power, based in Latham New York has developed a new fuel cell power plant that supplies 7 kilowatts of electricity and heat, using either natural gas or propane as the fuel. That is enough power to supply the electrical demand of a modern energy efficient home. Initially these fuel cell power plants will be grid parallel. Eventually they will be grid independent. Plug Power plans to commercially introduce this home power plant, distributed through General Electric, in 2002.

    *Several manufacturers are currently developing portable fuel cell power supplies. These power supplies can provide anything from a few watts up to several kilowatts of electricity. Portable fuel cell power supplies will be an alternative to conventional batteries for many applications. Applications include laptops, mobile phones, remote road signs, and lighting. Portable fuel cell power supplies have several advantages over conventional batteries. The primary advantage is that of energy density. Fuel cells can provide a higher energy density by both volume and weight. Thus fuel cell portable power packs can be lighter and can supply power for a longer period of time than that of conventional batteries. In addition the storage losses for hydrogen fuel cells are practically non-existent. Whereas conventional batteries slowly discharge their power over time, fuel cells powered by hydrogen can maintain their charge almost indefinitely. The third advantage is that the storage capacity of rechargeable batteries decreases as a function of the number of cycles of charge and discharge, such that they will eventually have to be replaced. Fuel cells will maintain their power output almost indefinitely. This particular fuel cell is a prototype 40 watt PEM fuel cell by Heliocentris, powering a remote blinking lamp. The fuel cell is contained in the upper part of the unit. The lower part of the unit contains a metal hydride storage cylinder, containing the hydrogen. Motorola Labs and the Los Alamos National Laboratory are co-developing portable fuel cell technology using direct methanol fuel cells. Company officials say these fuel cells, including a canister of methanol, will supply ten times the energy of a rechargeable battery of equivalent size. Thus mobile phones, for example, will apparently be able to remain on standby for a period of over a month. When the methanol in the canister is consumed, a new canister can easily be inserted. With the advent of this process, recharging batteries will no longer be necessary. Motorola expects these fuel cells to be commercially available in three to five years.

    *Fuel cells are classified by the type of electrolyte they use (Table 1). The different electrolytes operate at different temperatures. Low-temperature fuel cells include the alkaline fuel cell (AFC), the proton exchange membrane fuel cell (PEMFC), and the phosphoric-acid fuel cell (PAFC). All of these fuel cells use hydrogen as a fuel. This hydrogen can be extracted from natural gas, biogas, methanol, or propane by the process of reformation. The hydrogen can also be created through the electrolysis of water. High-temperature fuel cells include the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC). These fuel cells offer the advantage that they can use either natural gas or untreated coal gas as a fuel directly without the use of a reformer through a process called "Direct Internal Reforming".

    The sixth type of fuel cell is the direct methanol fuel cell (DMFC). It is also a low temperature fuel cell, but it can use methanol as a fuel directly without the need of reforming. The primary limitation to the direct methanol fuel cell is that the rate of reaction on the anode is very slow. This results in a very low operating voltage output. For certain applications (e.g., portable power), the direct methanol fuel cell may be ideal.*A fuel cell is a device that through an electrochemical process converts hydrogen and oxygen directly into water. In this process energy is released in the form of electricity and heat. The chemical process is electrolysis in reverse.

    In the PEM fuel cell, hydrogen molecules are oxidised at the anode to positively charged hydrogen ions, protons, releasing electrons to the cathode via an external electric load. The protons diffuse through an ion-conducting membrane to the cathode. At the cathode, oxygen combines with the electrons and the protons to form water. The overall reaction is hydrogen plus oxygen producing water.

    The enthalpy of this exothermic reaction is 285.8 kilojoules per mole*In this diagram we can see the various components of a simple fuel cell.

    A single cell consists of two gas field flow plates, one for hydrogen and one for oxygen, separated by a membrane electrode assembly, abbreviated MEA. The field flow plates contain channels to ensure that the gases are in contact with as much of the MEA as possible.

    As can be seen in the diagram, hydrogen molecules enter on the anode side of the cell, while oxygen enters on the cathode side. In a reduction reaction, the hydrogen molecule releases its electrons, which flow from the anode electrode through the external electric load to the cathode electrode. It is this flow of electrons which we observe as electricity. The hydrogen protons flow through the ion-conducting membrane to the cathode. At the cathode they combine with the oxygen molecules and the free electrons to form water. The fuel cell has electrochemically converted hydrogen and oxygen gases into electricity and water.

    *The MEA consists of two porous carbon-cloth electrodes bonded to each side of a polymer electrolyte membrane. This material, the electrolyte, allows the conduction of hydrogen protons from one side of the membrane through to the other. At the same time it prevents oxygen molecules from flowing in the reverse direction.

    On the electrodes are nano-sized particles of platinum. The platinum acts as a catalyst for the redox reaction to take place. Initially the hydrogen molecules are chemically adsorbed onto the platinum surface, forming hydrogen-platinum bonds. Platinum is unique in that it has the ideal bonding strength to both break the hydrogen molecule bond, to form the hydrogen-platinum bonds, while being able to release the hydrogen, allowing the redox reaction to proceed.

    A fuel cell therefore supplies a current, much the same way as a battery. However, unlike a battery, a fuel cell can provide electrical power indefinitely as long as hydrogen and oxygen are supplied. *The membrane of a fuel cell is between 50 and 175 microns thick; thats about the thickness of 2 to 7 sheets of paper. It is produced in sheets which can be cut to the required size.

    The electrolyte membrane consists of Polytetrafluoroethylene (PTFE) chains, commonly called Teflon. On the Teflon chains are side chains ending with sulphonic acid, HSO3. A close-up view of the membrane material shows spaghetti-like long chain molecules with clusters of sulphonate side chains. An interesting feature of this material is that whereas the long chain molecules are hydrophobic (repel water), the sulphonate side chains are highly hydrophylic (attract water).

    The hydrophylic regions absorb large quantities of water. Within these hydrated regions the H+ ions of the sulphonic acid are able to move, creating the ability for this material to transfer H+ ions from one side of the membrane to the other. For this reason the hydrated regions must be as large as possible. *It is interesting to compare the various methods available to date for the storage of hydrogen. We see that to store one kilogram of hydrogen in compressed gas cylinders requires 56 liters, as liquid hydrogen, not including the necessary equipment requires 14 liters. Hydrogen stored in a magnesium metal hydride container requires 9.9 liters.

    *Reformers convert a hydrogen rich fuel such as natural gas, methanol, or even gasoline into pure hydrogen plus the emission of carbon dioxide. They work via a catalytic process combining the fuel with water vapor at a high temperature. The result is fuel cell automobiles are able to carry liquid fuels and fuel cell stationary power plants can use natural gas or propane. For the immediate future, as long as fossil fuels are available, the use of reformers is the most cost-efficient method of producing hydrogen.

    Hydrogen can be produced sustainably from a solar hydrogen system, that is, a system using a device that transforms the radiant energy of sunlight into electricity (such as a wind turbine, solar panel, or hydro-electric turbine) for use by an electrolyser. When the sun shines, the wind blows, or the water flows, the electrolyser can produce hydrogen. Solar hydrogen systems are truly sustainable, for as long as there is sunlight, there can be hydrogen.

    There is also research and development taking place in the production of hydrogen from biological methods. For example Dr. Melis at University of California has discovered a green algae (Chlamydomonas reinhardtii) that electrolyses water producing hydrogen gas when sulphur is depleted from the water source. Biological mechanisms may one day provide the world with an additional source of hydrogen.

    *As long as the sun shines, the wind blows, or the rivers flow, there can be clean, safe and sustainable electrical power, where and when required, with a solar hydrogen energy system

    *Fuel cells are efficient. As fuel cells convert hydrogen and oxygen directly into electricity and water, there is no combustion in the process. As a result the efficiency is high, between 50 and 60%, about double that of an internal combustion engine. Fuel cells are clean. If hydrogen is the fuel, there are no pollutant emissions from a fuel cell, only the production of pure water. In contrast to an internal combustion engine, a fuel cell produces no emissions of sulfur dioxide which can lead to acid rain, oxides of nitrogen which produces smog, or particulates grit and dust. If methanol or natural gas is the fuel, there is an emission of carbon dioxide. However as the efficiency of a fuel cell is higher than that of an internal combustion engine, the emission of carbon dioxide is proportionally lower.

    Fuel cells are quiet. A fuel cell itself has no moving parts; however, a fuel cell system may have a few moving parts, including pumps and fans. As a result a fuel cell produces electrical power virtually silently. Many hotels and resorts in quiet locations, for example, would like to replace diesel engine generators with fuel cells, for both main power supply or for backup power in the event of power outages.

    Fuel cells are modular. That is, fuel cell stacks of varying sizes can be theoretically combined together to meet a required power demand.

    Fuel cells are environmentally safe. They produce no hazardous waste products, only the production of water.

    Fuel cells provide the opportunity to produce a sustainable source of electrical power. If fuel cells get their hydrogen from renewable energy sources, such as solar, wind, hydro, or biological methods, they can provide a sustainable source of electrical power. *