Hydrogen fuel switch: road, sea and pipe - the Scottish energy transition

Abstract

The world is on fire! The problem of anthropogenic climate change is getting worse. There is scientific consensus that the net emissions of greenhouse gases must reduce to zero. Target dates have been agreed internationally up to 2060. Scotland has adopted 2045; the rest of the UK, 2050. There is a common view that universal electrification is the net zero solution to our energy needs. It already exists and is familiar to consumers. Importantly, the electricity network already exists, making it easy to introduce solutions - at a small scale. This scaling matters: to replace all the energy currently provided by liquid vehicle fuels and natural gas would require a very large, and expensive, increase in the electrical network.

Electricity, however, is far from the only option. There are sectors where it is impractical or even impossible due to the size, weight and cost of batteries, the need for higher process temperatures than electricity can sustain, the time required for battery charging, or the off-grid location remoteness. Hydrogen, or its derivatives, appears to be the most viable alternative solution which addresses these issues. Advantages of hydrogen include relative ease of storage & transportation and much lower infrastructure costs. In transport, hydrogen offers faster refuelling, less system weight, and less raw material requirement in comparison to battery stored electricity. Disadvantages include the need for very large storage tanks due to the low density of hydrogen, and little existing infrastructure leading to higher barriers to entry than for electricity.

This thesis examines the hypothesis that in significant applications hydrogen will be more suitable than electricity; the most efficient future energy system will include both electricity and hydrogen. This will be addressed by exploring some of the requirements by which hydrogen can be used as an source or vector for net-zero energy, in comparison with electricity or other fuels. Analysis is in the context of Scotland, with its abundant raw renewable natural energy resources and an ambitious interim target set by the government of a 75% reduction in net emissions by 2030. Adjusting for local factors, most of the methods used and principles of the findings can be applied to other parts of the UK, Europe and the rest of the world.

First, the need for infrastructure to support hydrogen road vehicles is investigated, through a model built in Excel. The base scenario explored is that the fuel demand from large vehicles – buses and HGVs - is most likely to be met by hydrogen in the long run, while it is less certain for smaller vehicles. A plan is developed for an initial investment programme of hydrogen refuelling stations at a cost of c.£140 million. At the pace required to meet government targets, if only large vehicles are replaced with hydrogen ones, that network will meet about 7-8 years’ demand. If all diesel vehicles are so replaced, it would be adequate for 5 years. This is substantially cheaper than widespread electric charging for a similar provision (over £1 billion). Hydrogen provision is given context with a case study considering the planning of a real application of hydrogen refuelling, along with hydrogen as a natural gas replacement.

The cost of the additional road wear due to the greater weight of zero emission vehicles is examined. With battery HGVs and buses, an additional 30%, some £160 million/yr, would be needed for road maintenance in Scotland, or ~£1.8bn more across the UK. The equivalent as hydrogen would lead to an additional 6%. The difference is ~£2,500/vehicle/yr. The impact of cars and vans is negligible in both cases.

The proposal that shipping fuels can be replaced with hydrogen rather than electricity is tested. It is found that battery electricity is prohibitive due to cost and system size except over very short distances. Costs and emissions of hydrogen compare favourably to alternative low or zero carbon fuels in the longer run, though ammonia, derived from hydrogen, appears to be more likely to have the optimum cost & emissions balance in the short term. The choice of drivetrain could be enough to make a material difference either way.

Lastly, there is an expectation that the gas network will be able to deliver hydrogen instead of natural gas. Does the existing network have enough capacity to deliver the energy required? Based on a purpose-built Python model, the network does function though with some localised intervention. An approach is proposed to identify the intervention needs.

Taking an overview, it is clear that electricity does not fit all situations. There are areas where hydrogen could be readily implemented as a fuel, bringing clear environmental, economic and customer choice advantages.