Briefly explain why hydrogen is being promoted as an alternative energy-carrier
- 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
-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.
-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?
Identify and discuss the key challenges facing the introduction of a “Hydrogen Energy Economy”
- Refuelling station networks
- Large-scale, low-cost, low-carbon production
- cost of vehicles
- on board storage is still too bulky
- Public perception on hydrogen
-Briefly discuss the different options available for distributing hydrogen to a national network of hydrogen fuelling stations.
- 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
Briefly describe how a PEM fuel cell operates.
- 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.
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).
- 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
