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It is widely known that one of the major EU targets in relation to climate change is the decarbonization of the transport sector (partial till 2025 and total by 2050) [1]. Green transport is mainly based on electromobility and the relevant state-of-art holds that for specific vehicle types (passenger cars with large autonomy and short charging times, trucks, buses, trains, etc) a technology of choice is the use of hydrogen as a zero emission fuel [2]. The pertinent EU directive for the development of infrastructure for the alternative fuels (electricity, hydrogen and biofuels) [3] has been incorporated in the member states legislation and there are already more than 120 Hydrogen Refueling Stations (HRS) currently operating or under construction in Europe. Moreover, most member states have declared in a binding manner that at least 750 new HRS will be developed until 2025 while there are intentions for more than 1300 stations operating by 2030 [2]. The FCEVs (powered by H2) as well as the HRS store hydrogen at high pressures (350 bar for heavy vehicles and 700 bar for common cars) so that the fuel tank may contain the necessary mass of hydrogen for an autonomy of about 600 km. As a result, efficient hydrogen compression becomes a necessity for the operation of both H2 vehicles and refueling stations. The conventional, mechanical gas compressors consume large amounts of electricity, are particularly noisy and require frequent maintenance due to their moving parts. In that respect, there is a pressing need for the development of alternative hydrogen compression technologies (see, e.g. the European H2020 research program Calls) [4].

Based on the above, the ATLAS-MHC main technical objective was to develop, up-scale and demonstrate an innovative H2 compressor (without moving parts, hence noiseless) characterized by very low electricity demand. Its operation is based on the use of specially developed metal hydrides (without particular needs for CRMs) and on the availability of relatively cheap solar thermal energy (at a temperature range of 15-85 οC) and / or industrial waste heat. The figure below delineates the ambition of the ATLAS MHC: it aims for the largest pressure difference (hydrogen compression ratio) achieved below 80 οC !!

(Figure 1)

Building upon a laboratory prototype metal-hydride compressor (MHC), the new pilot scale, precompetitive MHC was tested and integrated in a complete renewable energy storage system. A significant objective of the project is also the assessment of the current market for metal-hydride compressors especially in storing energy from Renewable Sources (RES) in the form of hydrogen. Market penetration activities & concrete business cases have been studied in that respect.
The specific ATLAS-MHC metal-hydride compressor is a device that works by absorbing hydrogen at low pressure (<10 bar) and temperature (≤20 ˚C) and desorbing it at a higher pressure in subsequent steps (stages) by raising the temperature (at about 80 ˚C) with an external heat source. Metal hydrides are special alloys who can physically store hydrogen in their “spongy” matrices. This operating principle offers an innovative economic alternative to traditional mechanical hydrogen compressors. By employing successively higher pressure hydride alloys in stages in series, high pressure ratios can be generated. Indeed, using 80˚C hot water as the energy source, the ATLAS-MHC multi-stage hydride compressor manages to compress a 10 bar inlet H2 to a resulting final pressure of over 300 bar at a rate exceeding the level of 0.5-1 Nm3 of H2 per hour. In order to design and develop the Metal Hydride Compressor (MHC), it was important to select appropriate Metal Hydrides (MH) and gather sufficient information about these qualified materials. Α set of MH alloys have been investigated within the project in order to decide about which of them would be finally incorporated in the MHC. Following this characterization and selection process, we moved to larger scales and acquired / tested successfully several kg of the selected alloys.

(Figure 2)

A detailed literature investigation on the technology of the metal hydride hydrogen compression was carried out as well as the coupling of this technology to solar electrolysis process, covering a wide range of activities, namely the assessment of the technology from a thermodynamic as well as from a techno-economic point of view. This includes the design of the overall system (solar PV electrolysis for hydrogen production coupled to the MHC compressor) and the simulation of the multi-stage compression process. Furthermore, an economic evaluation of the overall system has been carried out by calculating CAPEX (Capital Expenses) and OPEX (Operational Expenses) along with an assessment of the environmental impacts associated with the overall process.

Moreover, a detailed literature survey on solar RES (CSP and PV) technologies market combined with hydrogen production was undertaken. The first part of the market analysis covered the evolution of “solar electricity market” - i.e. electricity produced via “solar” renewable energy sources (RES) - Concentrated Solar Power (CSP) and Photovoltaics (PV) - in countries of Southern Europe. Emphasis is placed on identifying and analysing the RES policies adopted in the different countries.
The second part involves the entire supply chain of “solar hydrogen”, i.e. production, storage, distribution and use. “Benchmark” (i.e. solar-aided electrolysis for production or high-pressure gas tanks for storage) as well as “niche” technologies (e.g. MHC) are identified, together with end-users of such “solar” hydrogen in the chemical industry and transport sectors. The findings are included in a report seeking to investigate possible growth and investment opportunities in the field of solar energy in Southern Europe and the effectiveness of support schemes.

On the training (secondments) and dissemination side, the plan approved by the EC Project Officer was carried out successfully following a restructuring of the initial scheme to reflect the actual project needs and characteristics. The main findings of the project were published in scientific journals and presented in several international conferences. Numerous contacts and discussions with interested stakeholders took also place in the course of the project with a view to exemplifying and widely disseminating the merits of the new MHC in the industrial and academic communities.

Overall, based on the smooth and timely execution of the main tasks by the partners, the project achieved all its major technical and training aims delivering the foreseen results and satisfying all targets set in the contract. An innovative device for the compression of hydrogen has been demonstrated with clear advantages over the competition and market deployment prospects. Relevant business cases were identified and studied from a techno-economic viewpoint. The novel characteristics of the project outcome have attracted the interest of venture capital investors for further development and commercialization.

[1] International Energy Agency (2017)
[3] Directive 2014/94/EU of the European Parliament and of the Council of 22 October 2014 on the deployment of alternative fuels infrastructure (AFI)

Project website address:
Contact details: Dr. Athanasios Stubos - ATLAS-MHC Coordinator
Phone: +30 210 6503754
Fax: +30 210 6525004