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Chapter 2 - Background
Background to the Technology, Role and Economics of Hydrogen and Fuel Cells
16. To fulfil the visions described in chapter 1 rapid development of fledgling fuel cells and hydrogen infrastructure is an absolute requirement. This chapter describes the technologies involved and their current status worldwide.
The Role of Hydrogen
17. When hydrogen is burned, the product of combustion is water creating the impression of a clean, pollution-free fuel. However, hydrogen, like electricity, is not an energy source in its own right, and it can only be as environmentally friendly as the primary energy used to produce it.
18. If renewable electricity is used to produce hydrogen by electrolysis then this provides a virtuous circle and a totally green application. The most likely renewable sources would be wind and marine systems that have spare capacity at times of low demand. Biomass is unlikely to be a suitable renewable source as any excess fuel would preferably be converted into liquid biofuels.
19. The utilisation of hydrogen can be achieved in three principal ways - standard combustion (i.e. in conventional internal combustion engines), gas turbine and fuel cell. Of these methods, fuel cells are the most attractive for renewable energy applications due to the high efficiency (potentially 90%) that is possible over a wide range of application scales as well as the avoidance of pollutants such as Nitrogen Oxide(NOx). Another possibility is to provide public gas supplies based on mixtures of hydrogen, methane and carbon monoxide, largely from renewable resources. Such a product could be used in current equipment for homes and industry.
20. At present, production of hydrogen from renewables is up to three times as costly as from fossil fuel and so sustainably produced hydrogen is not economic. HEG believe that public funds should be used to support demonstrations of systems using renewably produced hydrogen as explained later in this report. This will provide the basis for economic investments by the private sector as changing fuel economics close the current cost disparity gap.
21. To illustrate this latter point, current economics of fossil fuelled hydrogen production are escalating due to rising energy prices but little attention is paid to associated carbon dioxide emissions. Suggestions are now being made to combine such large-scale production processes with sequestration of the carbon dioxide produced. This will demand centralisation near suitable sequestration sites; it will increase cost and the extensive associated hydrogen distribution system would lead to significant energy losses. Under such circumstances the renewably produced hydrogen alternatives would look more attractive.
22. Scotland already has experience and skills associated with large-scale hydrogen production at the Mossmorran and Grangemouth facilities, which are linked with major companies like Shell and BP. In addition, Scottish and Southern Energy has joined with BP, Shell and others to evaluate the world's first full-scale hydrogen production - gas-fired generation - carbon sequestration project at Peterhead in Scotland.
23. These existing and future large-scale hydrogen facilities offer Scotland a building block on which to develop the infrastructure to produce hydrogen from renewable/zero emission sources for onward distribution and utilisation by, for example, urban consumers located at a distance from the initial source of energy production (such as a wind farm in, say, the Solway Firth or a marine power station in the Pentland Firth). These urban consumers are likely, initially, to be within Scotland, such as the conurbations of the Central Belt. In the longer term there may well be export opportunities of the hydrogen to other parts of the UK and beyond.
24. In the transport sector, liquefied or compressed hydrogen is inferior to oil and petrol in terms of stored energy density. However, the redeeming feature of renewably produced hydrogen for transport applications is its pollution-free conversion.
25. The benefits of hydrogen storage and use are discussed in detail in IPA's report entitled "Hydrogen Technology Systems". This demonstrates the economics associated with hydrogen use to provide peak power management and intermittency smoothing for networks with a high proportion of renewable generation. The following diagram illustrates how the EU thinking currently projects the development of sources for hydrogen production.
Figure 1: Maturation of hydrogen production pathways from HyNet Roadmap Executive Report 3
The Role of Fuel Cells
26. Fuel cells are in essence batteries with an external source of fuel; they have one very important characteristic, they offer very high chemical to electrical conversion efficiencies over a wide range of system sizes. This arises from the absence of mechanical work in fuel cell conversion, and means that only the most advanced and largest thermal power stations come close to the efficiency that can be expected from a fuel cell system of much smaller scale. Hydrogen is an ideal fuel for fuel cells although other fuels such as natural gas, biofuels and biogases are also attractive and Scotland has specialist skills in the utilisation of such fuels in fuel cells.
27. Stationary fuel cell systems can be either connected to the power grid or stand-alone. Such systems are likely to be fuelled by natural gas or liquefiable hydrocarbon fuels in the first applications with biofuels and hydrogen becoming more important as the technology matures. The expected stationary fuel cell technology development track is for decentralised power applications with a gradual transition from fossil fuels to CO 2 neutral fuels; however much early deployment will be in premium power applications particularly in the defence sector where fuel cells can achieve early competitiveness.
28. As time progresses, the load centres of the power network will become largely self-contained consisting of renewables supported by decentralised fuel cell systems. The advantages of a decentralised system arise from lower transmission losses, higher total energy efficiency and improved energy security. A high value national transmission network, powered by advanced thermal or nuclear generation, hydropower, buffered wind power and large-scale fuel cell systems will support these load centres and provide back-up and balancing power.
29. Stationary deployment is expected to involve both high- and low-temperature fuel cells.
High-temperature fuel cells will be applied where carbon-containing fuels, including less pure hydrogen, is available and for large-scale systems, particularly when high value heat is demanded. Low-temperature fuel cells will be applied where clean hydrogen is available and where early application is facilitated by technologies developed primarily for transport applications. There are major programmes of investment in fuel cells for transport applications in many countries, and this is being combined with development of new pilot infrastructures for hydrogen in California, Canada and Germany.
30. Fuel cells and hydrogen can enable the introduction of renewables on a much larger scale, especially through the increased availability and reliability of decentralised generation. They will play an essential role in the conversion of biofuels to electricity at a high efficiency and low emissions. There are many different kinds of gaseous and liquid biofuels. These can be produced from waste or through agricultural production. Biofuels can be used directly in
high-temperature fuel cells at a high efficiency and benefiting from the fuel flexibility of these systems.
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