Renewable energy harvested from wind or the sun fluctuates widely and cannot be matched to today’s power consumption. For this reason, intermediate storage systems will be needed in future that reconcile supply with demand. This is where hydrogen lends itself as an energy carrier. IAV has teamed up with partners to work on an alkaline water electrolyzer with an output of 100 kilowatts that is to benefit from automotive development.
Today, central large-scale power plants are geared towards the familiar consumption patterns of private households and businesses. Sun and wind are not as considerate. There are already major surpluses: “In feed-in management, the lost production of electricity amounting to 555 gigawatt hours in 2013 almost tripled to 1,581 gigawatt hours in 2014 according to the German Federal Grid Agency’s monitoring report. A further significant rise is expected for the future because the lost energy production in 2014 was more or less reached in the first six months of 2015 alone”, reports Dr. Christopher Severin, head of the System Development and Combustion Process Concepts department at IAV. “Added to this is the major north-south divide between production and consumption. All this means we will need new technologies in future to store the electricity that is not being needed.”
Hydrogen is an ideal energy carrier for this: It can be produced relatively easily from water and electricity by electrolysis and stored or processed in many different ways. Hydrogen can either be reconverted into electricity, is a fuel suitable for fuel cells, is a sought-after raw material in the chemical industry and can be turned into methane by “methanization” – a type of synthetic natural gas – that can be fed into Germany’s large natural gas grid with its huge storage capacity. It also forms the basis for the production of electricity-generated liquid fuels used in combustion engines or aircraft engines.
Low-cost electrolyzer with an output of 100 kilowatts
In particular, smaller electrolyzers are still too expensive for “power-to-gas” technology. Together with its partners, the Center for Solar Energy and Hydrogen Research BadenWürttemberg (ZSW) in Stuttgart, the Reiner Lemoine Institute (RLI) in Berlin and Wasserelektrolyse Hydrotechnik GmbH from Karlsruhe, this is something IAV wants to change. As part of the “ecoPtG” funded project, the researchers and engineers are developing an alkaline water electrolyzer with an output of 100 kilowatts. To reduce costs, they are using experience and components that have already been proven in automobile engineering. This seems appropriate because many of the requirements are very similar. “At 100 kilowatts, the output of an electrolyzer more or less equates to the output levels in hybrid and electric vehicles”, Severin says. “This is why we want to use the synergetic effects – such as for the power electronics, control and sensor system, as well as process-engineering components for temperature control and the media circuit, for example.” All electrified powertrains work with a converter that processes recuperated braking energy for the battery. Precisely this also needs to be done for the energy storage systems. The AC voltage from the power grid needs to be rectified for the electrolyzer. This can be done by converters from the automotive industry just as well as by expensive industrial rectifiers.
However, the components work under very different boundary conditions than in the vehicle. They are in quasi-continuous use and, in part, must cope with different currents. Therefore the technology cannot be used in power engineering without modifications. “This is why we are looking at a new development with basic modules from the automotive industry that are also suitable for several applications”, Severin explains. “The power electronics could not only control the electrolyzer but also recharge e-cars in car parks or supply the storage batteries in smart homes.” IAV’s high-performance control units can also be used in the new electrolyzers.
Components and methods from automotive engineering
Besides the electronics, the mechanical components of the new electrolyzer are also to benefit from the experience of automobile developers. For example, its cell frame could be made from far less expensive plastic instead of metal and, on top of this, existing vehicle components such as line cables and separators could be used for the electrolyzer’s process engineering. Added to this are the development methods from the automotive industry that are well and truly proven and also suitable for use in power engineering. And finally, IAV’s Energy Container provides a robust means for accommodating the system, lending itself for a hydrogen filling station that can be extended in modular fashion.
The partners have been working together in the “ecoPtG” project since November 2015. The concept phase has been completed and fundamental parameters, such as cell area and current density, defined for the electrolyzer. Primary research is currently in progress on potential materials and, from the second half of 2016, it is planned to develop the power electronics. This – as well as the first version of the electrolysis block – will be available in mid-2017 and then go into operation at ZSW. The project ends in October 2018, by which time there will be a second version of the electrolyzer integrated into the IAV Energy Container. By then, the project partners want to present a simulation-assisted analysis of market potential and operating concepts.
Modular system structure
“Our low-cost electrolyzer of the 100-kilowatt class is to produce 4 to 35 kilograms of hydrogen a day”, Severin says. “As it is modular in structure, it can be extended in line with demand, such as at hydrogen filling stations. As long as there are few fuel cell vehicles on the road, small low-cost filling stations can satisfy the demand for hydrogen fuel. As soon as demand rises, the electrolyzer can be extended in modular fashion and matched to needs.” This way, the technology not only helps to achieve the energy transition but also to decarbonize road traffic.
The German Federal Ministry for Economic Affairs and Energy is funding the project “ecoPtG” with a total of around € 4.75 million. Besides coordinating the project, IAV is also in charge of the work packages covering cost analysis and concept development, system integration as well as the electrolyzer’s periphery.