Hydrogen

Background on Hydrogen Fuel

 

Hydrogen as a Fuel Hydrogen is the simplest and most abundant of chemical elements. Hydrogen in its pure form is a gas at room temperature. Hydrogen gas can be used as a fuel and as an industrial chemical. As a fuel it can be used directly in specially designed internal combustion engines or in fuel cells to produce electricity and heat. How is it made? Hydrogen gas typically does not exist in nature in a form that would allow us to directly capture and use it. Because it is so light, any free hydrogen gas tends to drift up and away from the Earth. Hydrogen gas, however, can be produced from a number of different chemical compounds containing hydrogen. Water (H2O) is the most well known and abundant source of hydrogen. One way to produce hydrogen is to use electrolysis, which uses electricity to split water molecules into component hydrogen and oxygen molecules. The hydrogen is then collected and stored for future use. Hydrogen can also be derived from natural gas, which is primarily methane (CH4). The methane can be reformed to split away hydrogen molecules using a variety of commercial processes. Again, the hydrogen is collected and stored for use. Other sources of hydrogen include the various hydrocarbons (e.g. gasoline) and alcohols (e.g. ethanol, methanol). How would it be used? Hydrogen could be either produced at centralized manufacturing plants and then distributed to end users by tanker or pipeline, much like the existing use of propane or natural gas, or it could be produced on-site at the point of use. In the case of motor vehicles it also possible to produce the hydrogen on-board. For movement and transfer, hydrogen can be either a gas or liquid. As a gas hydrogen needs to be stored in a tank similar to propane but at significantly higher pressures due to the lower energy density. Hydrogen can also be stored as a gas in a tank containing metal hydride. As a liquid, hydrogen needs to be stored in a super-insulated tank at very low temperatures. Liquid hydrogen has a much higher energy density than gas, however, the process of liquefying hydrogen requires significant energy. Each of these storage methods has its advantages and disadvantages and the constraints of current storage technology remains a limitation.

Other Fuel Cells Stationary fuel cells can range in size from supplying a few kilowatts of electricity and heat for a home to providing hundreds of kilowatts of electricity for an office centre. While demonstrations are ongoing these fuel cells are now being installed commercially for various niche applications that require large amounts of reliable and high quality power (e.g. credit card processing and computer service centres). Demonstrations of fuel cells that provide almost all of the electricity and heating needs of homes are underway. The different stationary fuel cells include solid oxide fuel cells (SOFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC) and proton exchange membrane fuel cells (PEFC). Portable Fuel Cells These fuel cells can range in size from providing a few watts of electricity for a cell phone or lap-top computer to several kilowatts of power as a portable generator. Demonstrations are underway of various products that would replace cell phone batteries and lap top batteries.

Currently the lack of hydrogen manufacturing and distribution infrastructure is a major roadblock to moving beyond demonstration projects to a wider use of hydrogen by the public and other users. It is possible that a nearer term solution will involve producing hydrogen from other fuels such as alcohol or gasoline that are processed using a reformer. The reformer releases the hydrogen from the fuel to supply the fuel cell. Given the ease with which these hydrogen carriers can be distributed and stored using existing infrastructure this may be a short to medium term solution to supplying hydrogen.

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Why Hydrogen?

Energy Security

Since hydrogen can be produced from renewable sources there is the potential for many countries to meet a good portion of their energy needs without resorting to imports or worrying about depleting fossil fuel reserves. In addition, even if fuel cells use a fossil fuel as a hydrogen source the inherently higher efficiencies of fuel cells would decrease the overall demand for fossil fuels. In either case, increased security of supply and reduced expenditures on imports could result.

Environmental

The environmental benefits of using hydrogen in a fuel cell vehicle could be significant, but this greatly depends on the source of the hydrogen. For example, if the hydrogen is produced by electrolysis from water using electrical energy from a clean, renewable source (e.g. utility supplied hydro-electricity or wind-electricity), then there are no greenhouse gas emissions. If instead fossil fuel generation provides the input electricity, then the greenhouse gas emissions would be still high.

Another important benefit of using hydrogen is reduced smog in cities, which results from reduced air pollutants from vehicles, notably nitrogen oxides. Again, the extent of this benefit depends on the source of hydrogen. Using hydrogen derived from clean energy sources would eliminate smog pollutants.

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Focus on Hydrogen Fuelled Vehicles

Hydrogen can be used a fuel in vehicles powered by fuel cells or internal combustion engines. There are a number of advantages and disadvantages to each.

What is a fuel cell?

Fuel cells are devices that generate electricity from hydrogen and oxygen. There is not one single fuel cell, but rather at least seven different types, all with different performance characteristics and advantages. These include:

• Akaline fuel cells (AFC), an older type of fuel cell that is not commonly considered anymore.
• Phosphoric acid fuel cells (PAFC).
• Proton exchange membrane (PEM) fuel cells, also know as polymer electrolyte fuel cells (PEFC).
• Solid oxide fuel cells (SOFC).
• Molten carbonate fuel cells (MCFC).
• Direct methanol fuel cells (DMFC), also known as direct alcohol fuel cells (DAFC).
• Regenerative fuel cells.
• Hybrid combinations.

In most fuel cells oxygen is supplied from air while the hydrogen is supplied to the fuel cell as a gas, either stored as hydrogen or derived from hydrogen that is produced from methane, methanol, ethanol or other hydrocarbons.

What are their advantages?

Potentially low greenhouse gas emissions. Depending on the source of the hydrogen gas the greenhouse gas emissions will be lower than a current internal combustion engine. If renewable energy is used to generate the hydrogen greenhouse gas emissions may approach zero.

• Zero pollutant emissions from fuel cells using hydrogen gas directly.
• High efficiencies when compared to internal combustion engines.
• Low noise.
• Low vibration.
• High quality electricity.

What are their disadvantages?

• Very expensive. Large-scale production will likely reduce these costs.
• Range is limited with current fuel storage options.
• Lack of current distribution network.
• Technological development is ongoing and improvements are expected as this technology matures.

When can I buy one?

Fuel cell cars are being developed by all automobile manufacturers. Improvements to reduce costs are continuing, with more and larger vehicle demonstrations occurring. Fleet users are the first target for commercialization, likely beginning in about four to eight years. Transit buses are an important early niche.

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Internal Combustion Engines

What is an internal combustion engine?

This engine transforms chemical energy contained in a fuel into mechanical energy through combustion in a piston or rotary engine. All cars and trucks today except for pure electric cars use a form of this type of engine. Modified internal combustion engines can utilize hydrogen in place of gasoline.

What are their advantages?

• Relatively mature technology.
• Relatively low cost when compared to a fuel cell.
• Potentially low greenhouse gas emissions. Depending on the source of the hydrogen gas the greenhouse gas emissions will be lower than gasoline and if renewable energy is used to generate the hydrogen they may approach zero.

What are their disadvantages?

• Lower efficiency than a fuel cell.
• Some pollutant emissions from the engine remain (e.g. Nitrogen oxides).

When can I buy one?

A variety of hydrogen vehicles, using internal combustion engines, have been developed. These include passenger cars, shuttle bus vans, and transit buses, such as the recently demonstrated hydrogen hybrid internal combustion engine (HHICE) bus.

Contact Information:

Robert Parsons, MBA, P.Eng.
Hydrogen Specialist
Manitoba Energy, Science & Technology
Energy Development Initiative
12th Floor - 155 Carlton Street
Winnipeg, Manitoba R3C 3H8

Phone: (204) 945-6077
Fax: (204) 943-0031
Email: robert.parsons@gov.mb.ca

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