Environmental Impact Study of BIG HIT

The BIG HIT project is creating a replicable hydrogen territory in Orkney (Northern part of Scotland) by implementing a fully integrated model of hydrogen production, storage, transportation and utilised for heat, power and mobility purposes. BIG HIT will absorb curtailed electricity from one wind turbine on the site of Shapinsay and one wind turbine and up to seven tidal test sites on the site of Eday, and use 1.5 MW of Polymer Electrolyte Membrane (PEM) electrolysis to convert water into ~50 t pa of hydrogen.

There are three applications of hydrogen: heat, electricity, and mobility. The hydrogen will be used to provide heat to one or two local primary schools. It will be transported by ferry in hydrogen tube trailers to the largest island, Mainland, and the capital city, Kirkwall, where it will be used to fuel a 75 kW cogeneration fuel cell stack, which will provide heat and power to the harbour buildings and 2 ferries when docked.

Finally, it will be used at a hydrogen refuelling station to fuel a fleet of 5 fuel cell vans. The objective is to assess the potential environmental impact of hydrogen production, distribution and energy application in the Orkney Islands. A life cycle assessment (LCA) analysis is conducted on the hydrogen system concept of the BIG HIT project, according to ISO 14040 and ISO 14044.

The impact assessment is carried out using 1 kg hydrogen produced and consumed as the functional unit. The life cycle stage of BIG HIT project includes hydrogen production, hydrogen distribution, hydrogen application, and the replaced energy. The system boundary is built based on BIG HIT mass flow, considering the system expansion with ‘no BIG HIT’ as the substituted energy supply in the analysis.

Fourteen impact categories are assessed including climate change. The impact method is ILCD 2011 midpoint, where ILCD is the International Reference Life Cycle Data System. The software used is SimaPro. For the Orkney Islands, the analysis show that the hydrogen applications will contribute to avoid emissions from electricity not coming from RES, oil and diesel.

The total impact on climate change for electricity production from hydrogen is estimated to be 1.62 kg CO2 eq per kg hydrogen consumed. It can replace the climate change impact of 3.82 kg CO2 eq from UK average low voltage electricity. The system of hydrogen for heat includes electrolysis unit, hydrogen boiler and transport (road transport).

The substituted energy is oil, which is currently being used for heating supply. The total climate change impact for the hydrogen for heat is estimated to be 1.61 kg CO2 eq per kg hydrogen consumed, which can replace 9.45 kg CO2 eq of carbon emissions from burning oil. The system of hydrogen for mobility includes electrolysis unit, hybrid vehicle manufacture (vehicle manufacture, fuel cell battery, electric battery), transport (both road and ferry transport).

The substituted energy in the transport application is diesel. Compared to diesel vehicles, the impacts from hydrogen application of hybrid vehicle is negative regarding climate change, acidification and water resource depletion. The total climate change for mobility is 4.36 kg CO2 eq per kg hydrogen consumed, which can replace 8.39 kg CO2 eq from carbon emissions from using fossil fuels.

The quantitative assessment of other impact categories, according to the ILCD method, suggests that no significant trade-offs with other impact categories can be found. Climate change represent a good indicator for other impacts as well. The impact results show that most emissions occur at the hydrogen production stage.

The contribution to climate change stemming from the hydrogen production corresponds to more than 80% of the total impacts with regards to the electricity application, 98% with regards to the heat application and 38% regarding the mobility application. The detail life cycle assessment of the hydrogen production has shown that the largest environmental impact can be attributed to the manufacturing of the PEM electrolyser system.

Therefore, a detailed life cycle assessment of the 1 MW of electrolyser system has been conducted separately to elaborate on the environmental impacts. The results show that the electrolysis stacks are responsible for the largest part of the environmental impact due to the material input of platinum, stainless steel, etc.

However, the amount of metals used as catalysts is only roughly estimated. For the current study a mix of recycled and virgin materials have been modelled; this is based on the current norms for the materials modelled, for example, steel, a percentage of recycled materials has been included, based on the global average of recycled crap steel.

Any recycling of catalyst materials has not been included in the study due to lack of information regarding the recycling process. Based on the current assessment of hydrogen production and energy applications, it is concluded that the system demonstrated in the BIG HIT project will represent a significant reduction of Green House Gas emissions compared to the current energy system.

Overall, hydrogen used for electricity generation has the potential to reduce the climate change impact (CO2 eq) by 58% compared to the conventional energy solution. Likewise, hydrogen used for heat supply reduces the climate change impact by 83%, and hydrogen used for mobility purpose reduces the climate change impact by 48%.