Learnings

Outcomes

• In selecting the right LOHC compound, benzyltoluene-based LOHC-system (BT-system) was selected as the preferred choice, this was due to the BT-system’s technical manageability, low viscosity, excellent cycle stability, and compatibility with existing petrochemical infrastructure. A comparative analysis was conducted between two BT-systems, Benzyltoluene (BT) and Di-Benzyltoluene (DBT), to identify the more suitable system. Although one mole of DBT stored more hydrogen than BT, the BT reactors had several advantages. These included the requirement of less catalyst, less degradation, higher cyclic stability, lower viscosity at low temperatures, and importantly, lower production costs. The production cost for a certain mass of BT was $1.265/kg, which is lower than for DBT at $1.402/kg. In conclusion, when compared with the DBT, BT offers similar hydrogen storage capacity, dehydrogenation heat demand, toxicity classification, and hazard classification. However, the BT-system stands out due to its higher productivity, cyclic stability, lower production cost, and better technical handling. Consequently, the LOHC technology provider, Hydrogenious LOHC Technologies, opted for the BT-system over the DBT-system for their projects.

• Analysis was carried out on the reactor suitability, where the OneReactor concept was compared against using multiple reactors. The OneReactor concept was observed to have lower investment and operational costs, is more dynamic and shows a longer catalyst lifetime. Carbon monoxide tolerance and patents still need further clarification, but there were no strong arguments against, subsequently, the recommendation was to use the OneReactor concept.

• A roadmap for the project consent was developed, assessing the health and safety, planning, and operational regulations and permits in Scotland. The key UK safety regulations for the site where identified, the review identified that the LOHC demonstrator could potentially surpass the lower tier COMAH threshold and a HSE application will be required to evaluate the hazards and risks that the hazardous substance may pose to people in the surrounding area. Operations of the HyScale plant are unlikely to be subject to PPC permitting. However, considering the novelty of the proposed processes involved, it is suggested that engagement with SEPA is undertaken to confirm the potential applicability of the following activities: Schedule 1, Section 4.1 and 4.2 during dehydrogenation of the LOHC, which could be defined as production on an industrial scale. It could also fall under schedule 2, Part 1: as the release of solvents, including volatile organic compounds (VOCs) into the environment on a scale that would incur a permit for operations to commence.

• The detailed engineering design and process instrumentation outputs were useful in providing a strong project definition. This definition which was sufficient to provide a class 3 cost estimate with an expected accuracy range of −20% to +30% using AACE standards. 

• The project used a computational optimisation model to assess the cost implications of using LOHC systems to store and release hydrogen when co-located with a hydrogen production facility. The scenarios considered include 100,000 homes (representing an Aberdeen-sized region) and another with a 1,000-home network (typical of a statutory independent undertaking). In the 100,000-home scenario, a system without LOHC storage incurred a 17% higher levelized cost of hydrogen (LCOH) and 21% greater capital expenditure (CAPEX). However, at the 1,000-home scale, the LOHC storage system yielded a 9% reduction in LCOH. This decrease was primarily due to the LOHC system capitalizing on energy price arbitrage. Although the LOHC plant incurred additional costs (£1.29/kg H2), the overall savings in energy and electrolyser CAPEX amounted to £2/kg H2.

• The optimal production plant sizing involved a 1.41 oversizing factor for the 100,000-home scenario (using autothermal reforming) and a 1.59 oversizing factor for the 1,000-home scenario (employing electrolysis). LOHC storage served dual purposes: supplementing hydrogen production during peak demand and storing excess hydrogen generated when fuel prices were low, releasing it when prices were high to maximize cost benefits.

• The levelized CAPEX of LOHC storage and dehydrogenation plants was competitive with that of geological storage, the actual commercial advantage depends on operating models and access to geological storage. Applying a Monte Carlo simulation, the total installed costs for the two scenarios were £17.3 million and £338 million for the 1,000 and 100,000 home sizing cases, respectively.

•  The study found that there have been recent announcements highlighting the potential of Liquid Organic Hydrogen Carriers (LOHCs) in large-scale distribution projects. While these developments are promising, most of these projects are still in their early demonstration stages. The technologies for hydrogenation and dehydrogenation are yet to be validated on a scale comparable to what has been proposed in these announcements, indicating a lower TRL. Additionally, the ammonia value chain as a hydrogen carrier and geological storage projects are making significant advancements. Recent developments in cracking technology have improved the TRL for ammonia as a hydrogen carrier. Meanwhile, geological storage projects continue to progress, with salt caverns and lined rock caverns leading the way, despite financial and time constraints.

Lessons Learnt

Project schedule 

Initial contracting was a challenge due to the multiple partner collaboration and IP agreements at the time of project initiation. This took time to work through, delaying the start of the project. Lessons learned have been taken forward from this for other projects.

Stakeholder Engagement

The project brought together an international collaboration of partners and experts to feed into the work packages and key to the delivery of the project was effective stakeholder engagement with individuals involved in the design and economic assessment of the LOHC technology.