Renewable methane for marine applications
Headed jointly by mtu
and the DVGW (German Technical and Scientific Association for Gas & Water) Research Unit at the Engler-Bunte Institute of the Karlsruhe Institute for Technology, the ‘MethQuest Project’ currently involves 27 partners who are working on methods of generating fuels from renewable energy sources for use in engines. One area of their activities involves mtu
researchers looking at two new engine concepts for marine applications. “We are working on two different projects. One focuses on an Otto engine concept and the other involves a flexible-fuel engine concept with direct injection,” explained project leader, Dr Manuel Boog.
Otto engines have been around for a long time because it is easy to burn gas in Otto engines. The problem with this concept is that the gas is never entirely combusted and uncombusted methane can escape. The phenomenon is called ‘methane slip’. “Methane is more damaging to the atmosphere than CO2. Consequently, the potential of gas engines to achieve substantial reductions in greenhouse gases is not exploited,” said Boog. One of the aims of the MethQuest Project is to develop a ‘methane oxicat’ (catalytic converter) to neutralize the negative effects of methane. The problem is that methane requires high temperatures for oxidation in the exhaust gas tract. In the engine, such temperatures are only present upstream of the turbocharger turbine. The catalytic converter therefore needs to be located here. However, this has a seriously negative influence on engine dynamics and mtu engineers are therefore working on an electrically assisted turbocharging concept that will counteract these disadvantages.
Gas engine with no methane slip
The second gas-engine concept under investigation for marine applications, the flexible-fuel, direct-injection concept, involves the development of a completely new combustion process. “Here, just like in a diesel engine, the air is first compressed in the combustion chamber. The main source of energy, gas, is then introduced and a small quantity of diesel is injected at the same time to ignite the gas,” explained Boog. The advantage of this process is that the gas is almost entirely combusted and the unwanted occurrence of methane slip remains negligible. “We have already demonstrated that this combustion process works in a different, publicly sponsored project called ‘FlexDi’,” added Boog. The concept has the additional benefit that the combustion process involved also means that methanol can be used to power engines without complications. One of the challenges remaining to be solved here is the development of a suitable high-pressure gas system as the injection concept means the gas needs to be highly compressed and heated for injection.
“We will run trials with both concepts and the pressurized gas supply system and will then decide which is the most promising for further development in the context of the drive system overall,” said Boog. Both concepts aim to produce engines that deliver comparable power and performance to diesels but with a significant reduction in environmentally negative emissions.
Hydrogen and the combustion engine
In the context of the ‘MethPower’ research project, mtu
is also working on the development of engine concepts for stationary gas engines. “We want to establish which engine will allow us to generate electricity most efficiently,” said Project Leader Dr Michael Thoma. This project also involves the development of two engine concepts that will ultimately be compared with each other. One is a hydrogen-powered engine. “Hydrogen can be produced from superfluous electric power by electrolysis. It therefore makes sense to use it in our engines,” explained Thoma. Just as with the natural gas engine, the MethPower Project employs the combustion of hydrogen using the Otto process. A spark plug is used to ignite the hydrogen/air mixture. However, hydrogen burns much faster than natural gas. “That is a challenge we will deal with over the coming months,” declared Thoma.
Together with its other aims, the MethPower Project is working on the continued development of an engine that will run on natural gas and/or methane. “The mtu
portfolio has included these engines for quite some time. What we are now seeking is to incorporate the engine in a system based on fuel generation and exhaust gas utilization,” said Thoma. The CO2 generated during combustion could be extracted directly from the engine exhaust and this CO2 could be used to produce new methane. “The idea is particularly interesting in the context of microgrids,” said Thoma. In this configuration, the gas engine is integrated in a network of power generators and storage devices. The network could be extended by including a ‘power-to-gas’ installation that would reduce the battery requirement. “The power-to-gas installation would work in conjunction with a gas storage vessel, like a large battery. It would use renewable electrical energy to produce methane that could be converted back to electricity if required whenever no sun or no wind is available,” explained Thoma.
At the end of the process, R&D specialists will have to decide which concept will provide the best balance between energy generation and energy consumption and thus deliver the greatest efficiency.
Solutions for the future
Synthetic fuels and new engine concepts all have one thing in common – they all make a major contribution to minimizing CO2 emissions and promoting moves toward the more responsible use of energy. “That is our aim and our duty as a responsible company. We aim to develop drive solutions for the future and we commit to playing an active role in that process,” said Dr Peter Riegger in summary.