Alexander Tremel

Chemical and Biological Synthesis—Basis for Gaseous and Liquid Fuels

Hydrogen production via electrolysis is followed by chemical or biological synthesis to produce a gaseous or liquid fuel that can be easily transported and applied in the existing fuel infrastructure. Today, chemical synthesis plants are operated on very large scale and under steady-state conditions. The utilization of renewable electricity sources in Power-to-Fuel plants requires smaller and more flexible synthesis concepts. Considering the technical and economical feasibility, the potential fit of the target molecule to today’s fuel infrastructure and the expected societal acceptance, methanol production seems to be the preferred process route.

Power-to-Fuel Plants—Conceptual Design and Applications

The plant design and operation strategy of a Power-to-Fuel plant depends on the electricity source and further local boundary conditions. It is possible to operate the plant within an integrated regional energy system, i.e. to benefit from low electricity prices at times with a high feed-in from renewable sources and to provide ancillary services to the electricity grid. It is also possible to utilize sunny and windy locations worldwide for the dedicated generation of electricity and the direct downstream production of electricity-based fuels. A Power-to-Fuel plant model and technology and cost outlooks for key components are used to optimize plant layout and operation regarding capital and operational expenditures. This is used to predict production costs of electricity-based fuels at different locations worldwide.

Evaluation and Discussion

The lowest production costs are enabled by directly connecting the Power-to-Fuel plant to onshore wind, solar photovoltaics and hydropower generation. Generally, the differences between onshore wind in Morocco, hydropower in Scandinavia, solar photovoltaics in Dubai, and a mix of onshore wind and photovoltaics in South Australia are small for optimized Power-to-Fuel plants. These plants enable fuel production costs between 104 and 128 EUR/MWh. The capacity factors of main components significantly vary for different Power-to-Fuel plants and are not directly correlated to fuel production costs. Operational flexibility (e.g. ramp rate, part load operation) is identified as important techno-economic parameter. After adding transportation costs and margins electricity-based fuels will likely compete with biofuels on a price basis in the next decade, but could result in lower greenhouse gas avoidance costs. Electricity-based fuels could be the most cost-efficient pathway for the defossilization of liquid transportation fuels.

Electrolysis—Fundamental Technologies, Requirements and Current Status

The first and most important conversion step for the production of electricity-based fuels is the electrolysis of water to produce hydrogen. Alkaline electrolyzers have dominated the market and account for almost all installed electrolysis capacity worldwide. However, Proton-Exchange-Membrane (PEM) and solid oxide electrolyzers have a much higher potential for future cost reduction and efficiency improvements. PEM electrolyzers are particularly interesting as they enable the highest operational range to directly follow renewable power generation profiles.

Outlook: Risks and Opportunities

The defossilization of the transportation sector requires political support since total cost calculations clearly show that alternative technologies have high cost during the market introduction phase. Market penetration has to be stimulated by suitable regulations and funding programs. Front running countries are required that financially support these new technologies—not only via pure research and development programs, but also via subsidies and blending quotas that influence market conditions. After their successful implementation electricity-based fuels can not only be a link between the electricity sector and the transportation sector, but also a link between industrialized and developing countries. Very good solar and wind conditions are a clear advantage that is not found in most of the developed world. Electricity-based fuels can be an energy carrier which enables local added value in developing countries, the export of renewable energy and finally an innovative form of international development assistance.

Green hydrogen and downstream synthesis products – electricity-based fuels for the transportation sector

Electricity-based fuels are a missing link in an energy system between the electricity sector and the transportation sector. The electricity sector worldwide is undergoing a remarkable change. Since 2012, new additions in renewables overtook additions in fossil and nuclear power generation capacities1. In 2015, global investment in new renewable power capacity, at USD 265.8 bn, was more than double the USD 130 bn allocated to new coal and natural gas fired power plants2. Renewables outpaced fossil fuels regarding capacity additions and investments. Due to the increasing commitment to carbon emission reduction, climate change mitigation is now a worldwide target. The Paris Agreement entered into force on 4 November 2016 after countries responsible for an estimated 55 % of the total global greenhouse gas emissions (including China, the USA and the European Union) have ratified it. Political measures that reduce emissions (e.g. subsidies and tax reduction for technologies, bans for other technologies, CO2 pricing) will probably increase in the most important markets. There will be a further clear trend towards renewable power generation technologies, and solar photovoltaic and wind generation will dominate the market for new capacity additions.