Hydrogen Use for Transportation

Introduction

Utilising a hydrogen buffering system in combination with a renewable energy scheme such as the wind farms proposed in this research project presents the possibility for selling any surplus hydrogen generated for additional revenue. In order to prevent the hydrogen storage tanks reaching a maximum state of charge (and thus reducing overall system efficiency), the levels could be managed by siphoning off excess hydrogen to a transportation filling station.

Hydrogen has been used for various industrial processes for over 100 years now. At present, the world roughly produces 42 billion kilograms of hydrogen per year where the majority of it is consumed by the petrochemical industry in processes such as ‘hydro-cracking’ of fossil fuels [1]. However, back in the nineteenth century, hydrogen was being used as a gaseous fuel in some of the earliest internal combustion engines developed by Reverend. W. Cecil and later by N. A. Otto. The annual production of hydrogen is actually enough to supply 130 million fuel cell vehicles per year [2]. In the twentieth and twenty-first centuries, hydrogen use as a vehicular fuel has been limited to experimental projects in cars but has been extensively used in liquid form for the space programs due to it providing the highest energy to weight ratio of any fuel (e.g. 1kg hydrogen has the same energy content as 2.8kg of petrol) [3].

The major considerations that would be involved in implementing hydrogen as a global transportation fuel include; the large costs and technical feasibility of a hydrogen infrastructure, costs of converting existing internal combustion engines to run on hydrogen as well as introducing new and relatively immature fuel cell technology for vehicles, technical and safety aspects associated with the onboard hydrogen fuel storage due to the element’s low volumetric density (i.e. liquid hydrogen storage is very energy intensive requiring a temperature of -253 degrees Celsius and H2 gas requires a large volumetric capacity) .

In the case of this research project, two case study locations for a hydrogen buffering system are being investigated with the potential for excess hydrogen to be used to fuel a small number of hydrogen-powered buses in the Stornoway example. Many of the problems associated with implementing a global hydrogen infrastructure/economy will not affect a smaller scale project like the one we propose for Stornoway to the same extent. Due to the small population of the Stornoway case study being investigated, only one filling station would be required located nearby the buffering scheme thus negating much of the costs involved in developing a hydrogen infrastructure. One or two hydrogen fuelled buses could be operated from this filling station to take over some of the routes travelled by conventional diesel powered buses. This would lead to a reduction/elimination of harmful emissions when compared to diesel powered buses depending on whether a fuel cell or hydrogen internal combustion engine is used.

The buses used in the proposal could operate either by electric motors (hydrogen used to power an electricity producing fuel cell) or directly consuming the hydrogen in an internal combustion engine. The European Commission has provided subsidies in the past for hydrogen powered transportation in major cities around Europe to help cover the costs of purchasing and maintaining the buses themselves. In these past projects, the focus was always on environmental and sustainable development of European public transport. However, the majority of hydrogen used in these projects was not produced from renewable sources as is proposed in this wind hydrogen buffering research project. This would be of an advantage when attempting to attract Government or European Commission interest in a hydrogen bus project on Lewis.

References:

[1] - www.hydrogenassociation.org/general/faqs.asp

[2] - http://www.greencarcongress.com/2008/06/air-products-pi.html

[3] - Requirements and State-of-the-art for Automotive Pressure and Solid Hydrogen
Storage, Author: Dr. J. Zeiger of Daimler Chrysler Group