Designing, sizing and economic feasibility of a green hydrogen supply chain for maritime transportation

Highlights

• A green hydrogen supply chain for maritime applications is proposed.

• A solar-driven electrolysis unit produces hydrogen for fuel cell-based ship.

• The sizing methodology is based on a properly developed numerical algorithm.

• The economic indicators have been calculated by the Life Cycle Cost analysis.

• The calculated levelized cost of green hydrogen is 5.61 €/kg (165 €/MWh).

Abstract

Green hydrogen plays a strategic role in the decarbonization of the maritime transportation. A step useful to favor the use and the exploitation of the hydrogen is the development of hydrogen supply chains that, by including both the infrastructures and the end users, can simplify the economic issues and the authorization processes. This paper is focused on the designing, sizing and economic feasibility of a sustainable supply chain that consists of a solar-driven electrolysis system that generates hydrogen for powering a fuel cell-based propulsion system installed on board a small passenger ferry boat travelling on a short route. The sizing procedure is based on a numerical procedure that aims to find the optimal supply chain configuration, in terms of components’ sizes, able to satisfy the hydrogen demand and to sustain the electrical energy requirements by only using the renewable source. Results of this study highlight that a hydrogen production of 128.7 tons/year is produced by using an alkaline electrolysis unit of 1780 kW integrated with a 8.15 MW_p photovoltaic power plant. The produced hydrogen allows to satisfy the specific requirements of the ferry boat with a total number of 314 roundtrips per year. From the economic point of view, by valorizing the electricity surplus and the by-product oxygen from the electrolysis process, the estimated profitability index and the discounted payback period are 2.03 and 9 years, respectively, making the investment attractive. The calculated levelized cost of the produced green hydrogen is equal to 5.61 €/kg. These results demonstrate the techno-economic feasibility of the proposed supply chain based on hydrogen technologies that, being already available on the market, can be effectively implemented to support the decarbonization of the maritime sector.

Introduction

The International Maritime Organization (IMO) has estimated that the shipping sector is responsible for 2.8 % of greenhouse gas (GHG) emissions equivalent to about 1036 Mton of CO₂ per year [1]. In this purpose, the IMO together with the International Convention for the Prevention of Pollution from Ships set regulations addressed to reduce global GHG emissions from international shipping by more than 50 % by 2050 [2]. In order to comply these goals, several approaches for shipping decarbonization can be applied such as the speed reduction (it can potentially save up to 34 % of energy), the installation of energy saving technologies (i.e the air cavity lubrication system and the flex tunnel and hull vane can allow an energy saving in the range 10–15 %) [3], the on board installation of Carbon Capture and Storage (CCS) system (for instance, Nordica is the first vessel operated with on board CCS [4]), the transition to low/zero carbon fuels and the replacement of novel technologies for the shipping propulsion.

In the short-term, the maritime industry is mainly devoted to operate vessels with low carbon or renewable fuels like liquified natural gas (LNG), methanol and biofuels; in fact, these fuels can burn in conventional internal combustion engines (ICEs) with good efficiency (40 %) and with minor retrofits [3]. With respect to a long-term vision, great attention is paid to the introduction of the fuel cell technology for replacing the main engine and/or the auxiliary engines.

The most mature and commercialized fuel cell type is the Proton Exchange Membrane Fuel Cell (PEMFC) which requires to be supplied with high purity hydrogen. Solid Oxide Fuel Cells (SOFCs) as well as the Molten Carbonate Fuel Cells (MCFCs) have a huge advantage, since they can be also fed directly with fuels like ammonia, biofuels, and synthetic renewable carbonaceous fuels. However, they have a lower Technology Readiness Level (TRL) than PEMFCs [5] and are characterized by slower start up time, higher weight, and costs [6]. In this scenario, the PEMFC technology and the hydrogen fuel are the key elements for favoring the decarbonization of the maritime sector. To assure an effective zero carbon footprint, it is important to produce hydrogen from Renewable Sources (RESs) as well as to reduce the distance between the production and the distribution sites for minimizing the emissions due to its transportation (gaseous hydrogen is commonly most delivered by trucks). Moreover, the use and the exploitation of hydrogen technologies require a comprehensive approach and a strategic planning of the systems through the designing of optimized Hydrogen Supply Chains (HSCs) that must include all phases, ranging from the production to the distribution and utilization [7]. Thus, the development of HSCs is a crucial issue and needs a detailed characterization and sizing of the key components that differ according to the on-site or off-site configurations. The on-site configuration, in which hydrogen is produced, stored and delivered directly to the end user, represents a good solution for favoring the installation of small-medium scale supply chains.

The choice of the optimal size of each subsystem of the HSC is very important to minimize the cost of the hydrogen, above all if it is produced by exploiting renewable sources. This optimization is a techno-economic problem because the selections of the primary energy source, the hydrogen production technology and the capacities of all facilities, have a great impact on the HSC total cost [8]. The economic feasibility of an HSC, based on renewables, also depends on geographical locations, so that the Levelized Cost of Hydrogen (LCOH) is quite variable, ranging from 3.5 €/kg [9] to 8.0 €/kg [10].

In this context, the present study aims to design and size, through the development of a numerical algorithm, a Green Hydrogen Supply Chain (GHSC) that can assure the required hydrogen production from RESs. The GHSC is designed selecting a passenger ferry boat as end user in which the conventional propulsion system (diesel engine) is replaced with one based on hydrogen technologies. Thus, the further goal of this work is to support, by means of the proposed GHSC, the hydrogen utilization in the maritime sector by contributing to its decarbonization with feasible solutions from technical and economical points of view.

The attention on the hydrogen application in the maritime sector is high as demonstrated by technical papers recently published in the scientific literature on the hydrogen production and its on board vessels utilization as well as by research projects funded on this topic in the last years.

Temiz et al. [11] evaluated, from a techno-economic perspective, the development of carbon–neutral marine fuel production, storage and refueling plant for short-distance ferries. Three ferries with a capacity of 100 passengers were analyzed. The proposed plant consisted of a floating photovoltaic system, a proton exchange membrane electrolyzer and a hydrogen storage system. The proposed system's overall energy efficiency resulted equal to 15.35 %, considering the grid-connected operation mode. The authors estimated the cost of hydrogen equal to 4.64 €/kg in the case of 26.7 ton/year of production capacity. Bonacina et al. [12] conducted the techno-economic pre-feasibility study of an off-shore liquid green hydrogen production plant for ship refueling in the Mediterranean Sea. Their study was conducted considering long-distance ships cruising between Sicily and Tunis. A wind farm, an electrolyzer, a water treatment unit and a hydrogen liquefaction plant for hydrogen storage and distribution to ships were considered. The authors estimated a LCOH of 4.0 €/kg. Pietra et al. [13] studied the behavior and performances of a new powertrain for the marine propulsion consisting of a 100 kW PEMFC module integrated with a supercapacitors energy storage system and a power inverter. The authors estimated, by means of an experimental characterization of the proposed powertrain, fuel cell and system efficiencies of 48 % and 45 %, respectively. Cavo et al. [14] presented a study on a PEMFC-based powertrain (144 kW) installed on board a zero-emissions ship - ZEUS (project financed by Fincantieri-Isotta Fraschini S.p.A). The author selected, as hydrogen storage system, the metal hydrides technology (50 kg of stored hydrogen). The analysis was focused on the powertrain performances and on the thermal coupling of the fuel cell and the hydrogen storage system by applying model-based approach devoted to ensuring the system's feasibility at different loads. Gaddaucci et al. [15] carried out experimental activities on the HI-SEA system that is a 240 kW real-scale test rig consisting of 8 fuel cell stacks installed on two parallel branches, able to work both independently or in parallel mode. The system was tested in steady-state and dynamic conditions as well as following a specific maritime operative profile. Results of this study highlighted that the developed system was able to successfully respond in all tested conditions.

A study based on the life cycle assessment (LCA) approach, for evaluating the optimal conditions related to the installation of a PEMFC system on board a ship, was performed by Fernández-Ríos et al. [16]. Results underlined the environmental benefits that can be reached by using the hydrogen-based propulsion systems as alternative technologies to the conventional ones based on diesel engines.

In the last years several projects on the development of hydrogen-based powertrains for shipping have been funded, like E4SHIPS, MARANDA, e-SHyIPS and HyShip.

One of the first funded projects (2009) was the E4SHIPS project [17] that was aimed to demonstrate new technical solutions to reduce ship emissions by using the fuel cell technology. The proposed system, to be installed on board, was a trigeneration unit for satisfying the heat, power and cooling demands. Project’s results showed the great potential of fuel cells instead of conventional engines in terms of noise levels reduction and lower exhaust emissions. In 2017, the European Union (EU) funded MARANDA project [18], in which a 165 kW PEMFC-based hybrid propulsion system (hybridized with a battery) for marine applications was developed. Moreover, in this project, a mobile hydrogen storage container, which can be refilled at any 350 bar hydrogen refueling station, was designed. The e-SHyIPS project [19], stated in 2021, is focused on the definition of new guidelines for introducing hydrogen in maritime passenger transport sector with the aim to boost its adoption within the EU strategy focused on a clean and sustainable environment, towards the accomplishment of a zero-emission navigation scenario. In this project a lean-agile methodological approach is applied to identify and ensure the correct management of risks in all aspects related to design and operation of passenger ships, in which hydrogen technologies are used instead of conventional fossil-fuel systems. The HyShip project also kicked off in 2021, aimed to lower the development and operational costs of a wider move to liquid green hydrogen (LH2) for ship propulsion throughout Europe. The project is focused on the design, development and construction of a Ro-Ro demonstration vessel running on LH2, as well as the establishment of a viable LH2 supply chain and bunkering platform [20].

The great interest in the introduction of hydrogen in the maritime sector opens some technical issues involving both the design of the hydrogen supply chains and the development of novel hydrogen-based powertrains. In this context, the present study aims to design and size, through a numerical optimization approach, a novel and sustainable supply chain for introducing hydrogen-based powertrains in shipping applications and to demonstrate its techno-economic feasibility.

Thus, the novelty and the strength of this study are: (i) to develop a sizing procedure based on an optimization algorithm that allows to find the optimal GHSC configuration by using only renewable sources, (ii) to demonstrate the feasibility of a novel maritime mobility model based on hydrogen technologies that are already available on the market and that can be effectively implemented with advantages in terms of low noise, zero pollutant emissions and CO₂ avoided in comparison with fossil fuel-based solutions, (iii) to promote the maritime sector decarbonization by introducing not only the hydrogen as a clean fuel for ship propulsion but also considering its entire supply chain, from its production and storage in port to its on board refueling.