May 2015

1. Define the term “shale gas” and explain the process of hydraulic fracturing (fracking) to extract shale gas. (6 marks)

Shale gas is an unconventional form of gas that cannot be exploited using conventional methods by drilling a vertical gas well into a reserve as the gas is instead trapped in unconnected pores within shale sedimentary rocks. To allow the gas to flow these pores must be connected by producing cracks or fractures. Hydraulic fracturing works by drilling horizontally in the shale rock and pumping a mixture of water, propping agent e.g. sand and lubricants into the rock under high pressure in order to fracture it. The drilling equipment can then be withdrawn back and the gas will be able to flow up to the surface. 

List four main environmental impacts associated with fracking. (4 marks) 

Microseismicity can be induced by the injection of water causing fracturing

Groundwater can be contaminated by the chemicals within the fracturing fluid

Unmeasured fugitive emissions of methane can escape that will contribute to global climate change if leaks occur

Combusting unconventional forms of fossil fuels perpetuates fossil fuel lock in and contributes further to anthropogenic climate change.

2. The term “hydrogen economy” is used to describe a major shift to using hydrogen as a fuel. Where will the hydrogen come from and how will the hydrogen be used? (6 marks)

Hydrogen can be produced via at least 5 processes including gasification of solid fuels e.g. coal/biomass, steam reformation of methane, thermal dissociation of water, electrolysis of water and artificial photosynthesis. Electrolysis is the most widely used method and involves connecting a DC power source to a mixtue of water and electrolytes (so that electrons can move freely) which causes hydrogen ions to be attracted to the negative anode and oxygen ions to be attracted the the cathode. Hydrogen can be produced using this method when electricity is at a surplus, act as a vector so that when demand for energy is high it can be burned to make energy available in power stations or used in fuel cells for transport.

Explain why the hydrogen economy could be considered as an integral component of a more widespread development of renewable technologies. (4 marks) 

Athough renewable technologies have many benefits such as being sustainable, one of the biggest limitations is their intermittency with only geothermal being a reliable supply. Therefore if renewable energies are to make up a larger proportion of the global energy mix, storage solutions are required so that energy can be stored when there is a surplus e.g on a bright sunny or windy day for use later when demand is high or energy availability is low e.g at night. Hydrogen could be used as a vector for this energy and help balance the intermittency. A hydrogen economy would be the best way of doing this in order to make maximum use of the hydrogen produced as it would have many uses from powering domestic transport and acting as an aviation fuel to…