ORKNEY'S ENERGY FUTURE
HYDROGEN BUSES
INTRODUCTION
The electricity demand for decarbonising domestic heating, cars and 12 ferries does not entirely fulfil the surplus electricity produced from onshore wind generation. To prevent wasted electricity in Scenarios 2a and 2b, the use of hydrogen for energy storage was considered. One sector in which the hydrogen could be used is public buses.
The bus links in Orkney are limited to ten routes on the Mainland. The school bus has also been accounted for in the demand calculations. This is only operational during the school term. The contribution to the transport network is small, at 0.6% of the road use. Decarbonising the use of public buses, however, will contribute to Orkney’s goal of eliminating fossil fuels by the end of 2030 as they are currently diesel fuelled. The fleet of buses for the Aberdeen HyTransit project, were used as the basis for the model to calculate hydrogen demand which uses Ballard fuel cell buses (Figure 2).
Figure 1: Bus routes on the mainland [1].
Figure 2: Ballard bus schematic [2].
All bus routes in Orkney operate from Kirkwall Bus Station. It is therefore recommended that the hydrogen refuelling station be situated in the Bus Station. The bus schedule for the most part stays the same although there are seasonal and school term variations [3]. More bus routes are operational during the months of May to August as well as during school holidays. At the weekends, mainly Sundays, there is a reduced schedule.
HYDROGEN CONSUMPTION
Calculations were carried out to determine the hydrogen consumption for the public bus sector if the buses were powered by Ballard hydrogen fuel cells. The hydrogen consumption was calculated using Equation 1:
The distance travelled by each bus was measured on Google Maps using the Orkney bus schedule [3]. A Ballard fuel cell bus has a fuel consumption of 8 kgH₂/100 km and has a tank capacity between 30 and 50 kg [4]. To fuel all ten buses and the school bus for one year would require 88,632 kg of hydrogen based on current timetables.
During school holidays when there are more bus routes in operation, the hydrogen consumption is greater (Figure 3). The X1 bus service from Stromness to St Margaret’s Hope only operates on a Sunday from May to August, so during these months, the hydrogen consumption on a Sunday is increased.
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Figure 3: Daily hydrogen consumption for public buses on the Mainland for one year.
There is also variability in the hydrogen consumption between weekdays and weekends. On weekends, specifically Sundays, there are fewer bus services than during the week resulting in a 200 kg difference in hydrogen consumption (Figure 4).
Figure 4: Daily hydrogen consumption for public buses on the Mainland for school holidays and school term days.
ELECTRICITY DEMAND
The electricity demand to produce the hydrogen required for the bus fleet was calculated to determine if the magnitude of the surplus electricity would be enough to support the hydrogen buses. Equation 2 was used to calculate the annual electricity demand to produce the required hydrogen based on the infrastructure already in place in Orkney:
Where the electricity requirement is 66 kWh/kgH₂ [5] and the annual hydrogen consumption is 88,632 kg (~88.6 tonnes). The annual electricity demand to provide the hydrogen required to fuel the public buses is therefore 5.85 GWh. The BIG HIT project currently uses two electrolysers, in Eday and Shapinsay, which can annually produce about 50 tonnes of hydrogen [6]. To produce the calculated hydrogen required for the public buses, the production infrastructure would need to be upgraded.
The calculated hydrogen consumption was compared to the potential hydrogen that could be generated using wasted electricity in Scenarios 2a and 2b. The results are presented here.
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COSTS
To support converting the public buses to hydrogen fuel cell vehicles, an upgrade and renewal of infrastructure would be required. Several factors were considered to quantify the investment that could be required. The capital cost of implementation includes the cost of the buses and a new refuelling station. There is currently a refuelling station in Kirkwall for five council vans. However, this would not be sufficient to fulfil the hydrogen demand of the buses. Larger capacity electrolysers would be beneficial to supply the hydrogen demand.
The cost of one Ballard fuel cell bus is estimated to be £350,000 [7] and a fuelling station is estimated to cost £3,600,000 [8]. An implementation timeline has been proposed which has the first bus and fuelling station introduced in 2022. One bus would be added to the fleet each year until 2028, each replacing an existing diesel bus. Two buses would be added each year in 2029 and 2030 (Figure 5). The total cost for the implementation of eleven hydrogen fuel cell buses and a refuelling station is estimated to be £7,450,000. The initial “set-up” holds the largest cost, due to the high capital cost of the hydrogen refuelling station.
Figure 5: Cost of implementation of hydrogen buses for each year to 2030.
The Aberdeen HyTransit project saw the release of ten buses which, in total, cost £19,000,000 [9]. Over the last five years, the cost of hydrogen buses has halved [7]. Although the capital cost of implementing hydrogen buses in Orkney is an estimate, it is likely that the cost will decrease in future years, resulting in a reduced overall cost for the switch to hydrogen buses. Due to the evolving nature of hydrogen production in Orkney, the cost of buying electrolysers has not been included. To provide the hydrogen fuel for the entire bus fleet, one or more electrolysers may be required (dependent on size), however, if there are other hydrogen requirements in Orkney, there could be synergies with other projects.
AVAILABLE DOWNLOADS
The spreadsheet with the hydrogen demand calculations is available here.
REFERENCES
[1] Orkney Islands Council, "Orkney Bus Route Map," [Online]. Available: https://www.whatdotheyknow.com/request/486087/response/1164589/attach/2/Bus%20route%20maps.pdf?cookie_passthrough=1. [Accessed 15 April 2021].
[2] Ballard, "Fuel Cell Zero-Emission Buses for Aberdeen, Scotland," 2019. [Online]. Available: https://www.ballard.com/docs/default-source/motive-modules-documents/aberbeen-bus-case-study-website.pdf?sfvrsn=6151c280_2. [Accessed 18 April 2021].
[3] Orkney Islands Council, "Bus Timetables," 2021. [Online]. Available: https://www.orkney.gov.uk/Service-Directory/B/bus-timetables.htm. [Accessed 15 April 2021].
[4] Ballard, "Fuel Cell Electric Buses," January 2021. [Online]. Available: https://info.ballard.com/hubfs. [Accessed 22 April 2021].
[5] European Marine Energy Centre (EMEC), "Hydrogen Production Plant," EMEC, 2021. [Online]. Available: http://www.emec.org.uk/facilities/hydrogen/. [Accessed 10 April 2021].
[6] BIG HIT, "About the project," 2020. [Online]. Available: https://www.bighit.eu/about. [Accessed 22 April 2021].
[7] London Reconnections, "The Second Coming of Hydrogen? London's Hydrogen Buses," 2021. [Online]. Available: https://www.londonreconnections.com/2021/the-second-coming-of-hydrogen-londons-hydrogen-buses. [Accessed 21 April 2021].
[8] Hydrogen Station Maps, "Costs and Financing," California Fuel Cell Partnership, 2021. [Online]. Available: https://h2stationmaps.com/costs-and-financing. [Accessed 21 April 2021].
[9] A. Mehta, "Creating a hydrogen economy in Aberdeen," Reuters Events - Sustainable Business, 22 August 2018. [Online]. Available: https://www.reutersevents.com/sustainability/creating-hydrogen-economy-aberdeen#:~:text=Already%20the%20price%20of%20buses,by%20Northern%20Ireland%2Dbased%20Wrightbus. [Accessed 22 April 2021].