Hydrogen

Question 1

Briefly explain why hydrogen is being promoted as an alternative energy-carrier

Answer 1

• The hydrogen economy is proposed as being a part of the future low-carbon economy.
• As an energy carrier it can store and deliver energy in widely useable forms.
• it can increase energy security and sustainability of the energy supply chain and to reduce greenhouse gas emissions
• can be used as storage for wind or solar farms
• could be injected into main gas network and blended with natural gas

Question 2

-Describe the THREE principal techniques by which hydrogen can be stored on a hydrogen-powered vehicle. List the main advantages and disadvantages of each technique.

Answer 2

-Carbon fibre reinforced: reduce amount of metal so high-density polymer with carbon fibre reinforcement and inside has a metal coating to stop hydrogen diffusing into polymer.
Ad – well established technology
Dis – low to moderate compression; delivers hydrogen at high pressure; as safe as petrol
-Cryogenic storage: storage hydrogen at liquid form, tanks are smaller than in carbon fibre reinforced
Ad - good compression, low pressure
Dis – 30% energy loss; boil-off in days; bulky insulation
-Metal Hydrides
Ad – can make very small fuel tanks
Dis – too heavy for mobile applications, could be used in boats and ships?

Question 3

Identify and discuss the key challenges facing the introduction of a “Hydrogen Energy Economy”

Answer 3

• Refuelling station networks
• Large-scale, low-cost, low-carbon production
• cost of vehicles
• on board storage is still too bulky
• Public perception on hydrogen

Question 4

-Briefly discuss the different options available for distributing hydrogen to a national network of hydrogen fuelling stations.

Answer 4

• Hydrogen is conventionally distributed in: gases form cylinders; liquified form by tanked; liquified form by pipeline however do you produce more in centralised locations at higher efficiency or in more locations
• Large scale hydrogen pipeline distribution is feasible but likely to be expensive
• Existing natural gas pipeline network could be used; dilute hydrogen; technical problems likely to prevent higher concentrations; logistic problems of changeover

Question 5

Briefly describe how a PEM fuel cell operates.

Answer 5

• hydrogen produces energy and water. Allows energy generation with no local greenhouse gas emissions (from cars)
• fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough temperature to make them suitable for homes and cars. But their fuels must be purified, and a platinum catalyst is used on both sides of the membrane, raising costs.

Question 6

Explain why a number of international car companies have started to produce hydrogen fuel cell electric vehicles (FCEV), in addition to battery electric vehicles (BEV).

Answer 6

• Lithium ion battery are 830 kg to take you same distance hydrogen can do it for 125 kg
• Switched to hybrids for legal reasons on diesel cars
• interest in electric and other alternative fuel vehicles has increased due to growing concern over the problems associated with hydrocarbon-fuelled vehicles, including damage to the environment caused by their emissions, and the sustainability of the current hydrocarbon-based transportation infrastructure as well as improvements in electric vehicle technology