Professor Behrendt, you are Director of the Innovation Centre Energy (IZE) that brings together expertise in the energy field at the Technical University of Berlin. What are the main emphases of your research?
We are currently engaged in interdisciplinary work on fifty areas in five research clusters: efficient gas turbines, photovoltaics, networks and storage, use of low-temperature heat and energy-efficient buildings and towns.
A crucial question for the future is energy storage...
That’s connected with the network question. You see, existing networks are designed for just a few input points, in other words, large-scale power plants, and until now they have functioned by generating less electricity or heat when there is lower demand. Today we have a large number of decentralized input points as a result of the extensive introduction of renewable energies, and the input volume, for example in the case of wind turbines, is not particularly predictable. That alone presents a technological challenge. However, what do we do if there is no demand for electricity at the place it is generated and it cannot be delivered elsewhere in the quantities produced? In the past the fuel itself was the store. Today we need to think about storage.
Is a solution emerging here?
A solution is definitely not emerging for all sectors. The development of lithium-ion batteries is the path that will be taken in the small-scale sector once a number of technical problems have been overcome – and that is already foreseeable. Hydrogen is an option for larger solutions. We could use electricity to produce hydrogen through electrolysis and later generate electricity again in fuel cells to feed it into the grid at times of high demand. At the moment, however, the efficiency of this process is only 35 to 40%. A lot of energy is lost. So we have to develop electrolysis further and improve fuel cell technology.
What is the research cluster for energy-efficient buildings and towns focusing on?
Substantial elements of the technology are already available for buildings, but the incentive systems aren’t working properly yet. The field of “energy-efficient towns” raises interesting questions. One reason why we have so much mobility today is the fact that in the past people didn’t want to live where they worked – for example, near smoky factories. In a services-based society like the one we have today, however, we ought to think about ways of bringing living and working spaces closer together. That immediately reduces the number of necessary journeys and with it the amount of CO2 emitted.
Cars are the third largest emmitters of CO2 after buildings and power plants. What are you doing in that area?
There’s considerable need for development here. Today if you analyze fuel consumption and the driving performance achieved, you obtain an efficiency of roughly 20% under real conditions. That is unsatisfactory to say the least. We must therefore find strategies that enable us to significantly reduce the energy consumption of the automobile as an overall system. In the research cluster on low-temperature heat we are thinking about ways of using the energy contained in vehicle exhaust fumes. That may sound strange, but in fact a third of the energy that you bought with the fuel is blown out of the exhaust in the form of heat. That doesn’t really make sense. We must therefore find a way to recover part of that heat, for example, through thermoelectric conversion – whether for addition propulsion or to provide electricity in the vehicle. Exhaust emissions leave the engine at a temperature of 900 degrees Celsius. That could certainly be put to good use.
It is planned to produce 20% of primary energy from renewable sources by the year 2020. Can that target be achieved?
The Federal Government has upped the ante. And this is where science must warn against all too unrealistic expectations. For example, when I hear that the production of a litre of ethanol from maize in Iowa – that’s the relevant centre in the United States – requires roughly 4,500 litres of water to take it from the field to the fuel pump, then we really must see that we don’t throw the baby out with the bath water. Nevertheless, we are taking up the challenge.
But 20% from renewable sources still means that 80% will come from other sources...
Thank you for pointing that out, because that is often overlooked in the debate. We must certainly endeavour to achieve a 20% share of primary energy from renewable sources. Yet we must equally strive to optimize the energy yield of fossil fuels – in other words, further increase the energy efficiency of power stations. Because of the enormous amounts of fuel they use, every half percentage point improvement in efficiency represents a multmillion euro saving in annual fuel procurement costs. And in the case of fossil fuels, that also represents an enormous decrease in CO2 emissions. The best way to reduce CO2 emissions is to increase efficiency.
