Environmental and Safety Issues

The environmental and safety issues of Hydrogen are appointed in a variety of areas as follows:

· Electrolysis
· Storage
· Chemical and Biological Hazards
· Handling and Disposal
· Effects of Hydrogen on Humans
· Social Impact

Electrolysis:

Problems occuring with electrolysis are related to the water supply mainly. In order to get Hydrogen from electrolysis, clean water in needed and sometimes difficulties arise on this matter. Also, several countries face shortage on water and that may cause drawbacks on applying Hydrogen Technology on these countries. Assuming that electricity is produced from renewable energy sources, the impact is small but when different sources are needed for electrolysis, the impact on the environment has to be considered.

Storage:

To minimise the environmental impact the Hydrogen filling station can cause, the storage tanks are placed underground. However, several key points have to be addressed in order to avoid unexpected problems. Cylinder storage location should be well protected, well ventilated, dry and separated from combustible materials as well as they should not come in contact with sharp edges to avoid cracks and possible leaks in the filling station.

Chemical and Biological Hazards:

Hydrogen as a chemical element is relatively inert under standard conditions of temperature and pressure and becomes highly reactive under excessive conditions. It is a non-corrosive chemical element and can be contained in ambient temperatures by most common metals used in installations but they have to be designed especially to have sufficient strength for high pressures such hydrogen needs to be stored. Special attention must be taken in the concentrations of air and hydrogen where at atmospheric pressure; hydrogen is combustible at concentrations from 4% to 74.2% by volume. One of hydrogen's chemical properties is that when it expands, its temperature increases. Therefore, it must not expand rapidly from high pressure because there is a chance of self-ignition as hydrogen has the highest burning velocity of any gas and very low ignition energy.

Handling and Disposal:

Purging of hydrogen systems should be performed with an inert gas such as nitrogen. Also the use of a "first in - first out" inventory system to prevent full cylinders from being stored for excessive periods of time must be installed. When hydrogen burns, it creates a non-luminous flame, which can be invisible under bright light. Therefore, special flame detectors have to be installed in order to detect the flame in such occasions. Because hydrogen cannot be handled like any other fuel, gas suppliers and hydrogen experts should only deal with large amounts of hydrogen.

Effects of Hydrogen on Humans:

Hydrogen is not dangerous for human health but addressing a few points is essential. First of all, in case hydrogen comes in contact with the skin or the eyes, no harm is expected. In case of inhalation the effects are due to lack of oxygen and can cause headaches, drowsiness, dizziness and unconsciousness. An unlikely route of exposure is swallowing hydrogen but again no harm is expected because hydrogen is a gas at normal temperature and pressure.

Social Impact:

Currently the average person would not think twice about refuelling a car, as it is still relatively inexpensive and simple to do so. However over the next few decades the fossil fuel stocks will diminish, raising the costs of fuelling a vehicle dramatically until none is left. This will have to mark a major shift in societies perception of when and how often they can use the car. This should have a marked effect on the number of cars owned in the UK, as they simply will be too expensive to run. By switching to a hydrogen driven economy, a restriction on the number of vehicles will be necessary to be established as the energy required to fuel current or future increases in vehicle numbers is unachievable.
Their would also be a dramatic economic change on a global scale, as countries rich in renewable power will slowly replace those countries that are rich in fossil fuels. This could see countries such as Iceland with its geothermal and other renewable fuels exporting hydrogen in large quantities.

CO₂ Emissions:

To show that a hydrogen filling station reduces the amount of CO₂ emissions a simple example is shown. Assume that the hydrogen filling station and a conventional station refuel one hundred cars every day. A conventional car has an autonomy of 700 km and produces 145 gr/km CO₂ when the burning fuel is gasoline. Therefore, the amount of CO₂ for one year is:

365 * 100 * 700 * 0.145 = 3704750 kg CO₂ = 3704 tons CO₂

When hydrogen is the burning fuel, it only produces water, which can be collected and produce hydrogen again following the electrolysis method.

The chart below shows clearly the difference in environmental impact when gasoline and hydrogen fuel are compared in cars.

Amount of CO₂ emissions produced by gasoline and hydrogen as a burning fuel in cars