Veröffentlicht 2. Juli 2010 von Beatrice Lugger
Energy for the future – a search
Energy and sustainability are this year’s focus for the panel discussion and the exhibition on the Isle of Maine. A couple of thoughts in advance (1). About 80 percent of the world’s energy needs today are met by fossil fuels: oil, coal and gas. The combustion of materials millions of years old has made humans ever more mobile and accelerated the pace of industrialisation. Supplies, however, are finite, and wasteful burning of these resources is leading to exceedingly high emissions of carbon dioxide, with all the attendant consequences for the earth’s climate.
"It is important that we work more intelligently with energy, which is becoming ever more precious," Theodor Hänsch, Physics Nobel Laureate 2005, demands. First and foremost, energy conservation bears a truly great potential.
The Director of the Max Planck Institute of Quantum Optics hopes that his field of research will aid indirectly in such efforts by speeding up the flow of data, thus enabling more video conferencing and a greater exchange of information online, which will help people avoid travel. "In principle, we will have to place our bets on an entire spectrum of possible alternatives, including nuclear energy as an interim solution, until we can, hopefully, exploit other forms of energy on a large scale," Hänsch feels.
Great hopes are being placed in a broad renaissance of such renewable energy sources as hydroelectric, wind and solar power. It has been a long time since wind and hydroelectric power have driven tools directly. In today’s highly technical plants, electricity is generated and then fed into the public grid. Solar energy itself is used in a similar way, whether by photovoltaic means (conversion into electrical energy) or by solar thermal means (conversion into heat). One of the most ambitious projects in this regard is named Desertec: electricity generated by the power of the Saharan sun, could supply Africa and Europe as a lasting source of energy. Solar thermal power plants covering around 20,000 square kilometres would capture sunlight in parabolic trough mirrors and use it to evaporate water which would in turn drive turbines to produce electricity. "Europe could draw around 15% of the electricity it needs from the desert by 2050," explains Robert Pitz-Paal, Deputy Director of the Institute of Technical Thermodynamics at the German Aerospace Centre (DLR), which is playing a pivotal role in developing the technology behind the vision for Desertec.
The cost per kilowatt hour of solar thermal power is still much too high, admittedly, to compete with that of electricity from coal and nuclear power. But Pitz-Paal is convinced that "they will be more financially competitive within the next 15 to 20 years." But price isn’t everything. The solar researchers at the DLR still have their work cut out for them: They want to increase efficiency and find out how to get the electricity to Europe without enormous waste along the way – high voltage cables that work on a DC basis instead of the usual AC could be one solution here. And they also have to find suitable storage facilities that can make energy available at night as well, when the sun doesn’t shine. They are working with salt and sand, concrete and even chemical storage systems on the basis a vast array of different materials.
Perhaps hydrogen will, in the end, win the race to be the energy storage medium of the future. Great hopes have already been placed in it because the principle behind it seems so simple. Water is made to undergo fission, and the hydrogen in it stores the energy that can then, when needed, be made to combust with oxygen and create water again. It sounds both clean and feasible. Jules Verne wrote as early as 1874: "Water is the coal of the future."
However, storage in hydrogen is no simple undertaking. Larger amounts do allow themselves to be stored relatively well at extremely low temperatures or under enormous pressures. However, other storage forms will be needed if it comes to be used in the mobile sector. At the Max Planck Institute (MPI) for Coal Research and at the MPI for Metals Research, work is being done on such promising storage media as metal hydrides and what are called MOFs, all of which can bunker a great deal of hydrogen. Hydrogen is often being used as the energy-bearing medium in fuel cells. Researchers at the MPI for Solid State Research are working to use improved materials that will make this application both more reliable and more cost-effective.
A vision for a hydrogen future already exists: Cars powered by a fuel cell and an electrical engine in place of the classic internal combustion engine. But there is no mass production of them and no network of hydrogen stations across any entire area.
"There could also be hybrid systems made up of a battery and fuel cell, possibly still coupled to a range extender that would help the vehicle go further," says Holger Hanselka, Head Coordinator of the Research Group for System Research into Electro-mobility at the Fraunhofer Gesellschaft. The group wants to get electric cars onto the street and is betting on the know-how of the staff at its 33 different institutes to do so.
Another instance is the Institute for Chemical Technology, where Jens Noack wants to use what is called a "Redox" flow battery made up of liquid electrolytes to create a system of electrical stations "that only need a few minutes to completely recharge a vehicle." One should then be able to drive around 100 kilometres. Thanks to such innovations by the research group, and those made by many others, Hanselka thinks that it is realistic to believe "that by 2020 more than one million electric vehicles will be driving Germany’s roads, and we will have the matching network of stations offering drivers a variety of opportunities."
The mix in our mobile future will also continue to include cars powered by fuels from biomass. At the Institute of Technology (KIT) in Karlsruhe, they are counting on biofuels of the second generation. "We are exploiting biomass that is mostly dry, nothing that takes up land in competition to food production," says Nicolaus Dahmen, Project Director for "Bioliq" at KIT. Consideration is being given to residual straw and wood from agricultural and forestry activities as well as that from conservation efforts.
This biomass can be energetically densified into a special oil mixture, called BioSyncrude, at small, decentralised plants. Then kerosene, diesel or regular fuel for internal combustion engines can be made from it at one centralised plant.
All in all, though, electricity will probably play an ever more important role. Even in geothermal, people have long been thinking not just in terms of directly exploiting only the heat coming up from the earth’s depths. At the German Research Centre for Geosciences, for instance, Ernst Huenges is converting thermal energy into mechanical energy that can, in turn, be used to generate electricity – in Germany at a water temperature of 120 to 150 °C, albeit with a huge loss in energy of 90%. But that is exactly what Huenges and his team want to greatly improve upon and as he explains, "After all, this energy source is truly richly abundant."
Theodor Hänsch is urging caution on many of today’s programmes and warns against launching large-scale projects, for instance in solar and wind energy, all too quickly using today’s technologies. He reminds us that "We must not neglect fundamental research that might, after all, lead to entirely new approaches that could in turn take us a huge step forward." Research into the basics gives young people an opportunity to shape the future perhaps a bit differently using entirely new ideas.
Who knows, perhaps it will be possible to bring the sun down to earth? According to one model of the fire that powers stars, hydrogen isotopes fuse to form helium, releasing huge amounts of energy in the process. The peaceful use of nuclear fusion is an idea that has prodded physicists on for more than 50 years and has turned out to be a truly Herculean task. To fuse, atoms have to strip off their electron shells to create a plasma. On earth, researchers are employing the hydrogen isotopes deuterium and tritium because they fuse more easily than their solar original. "However, we have to heat the plasma to 200 million degrees to induce the fusion reaction," explains Günther Hasinger, Scientific Director of the Max Planck Institute of Plasma Physics. Because the ultra-thin fuel cools off immediately after each material contact, physicists have to enclose the plasma in non-contact magnetic fields.
At present, the International Experimental Reactor ITER, Latin for "the way," is being built in France with German involvement. By the mid-2020ies, researchers are hoping to use it for nuclear fusion that will generate ten times the energy required to heat plasma. If they succeed, DEMO, ITER’s successor, should then, starting around 2040, generate the first fusion electricity. Actual power stations could then go onto the grid in 2050. If the use of this source of energy succeeds, it would mean the discovery of an economically viable, safe and environmentally sustainable source for electricity. But the results are still open, as Theodor Hänsch points out – "though it would, of course, be a dream come true."
(1) this article has been published by far in the catalogue for the Mainau Exhibition "Entdeckungen 2010: Energie", which can be visited till August 29th 2010.
more about sustainability and energy at Lindau:
A sustainable look at the future – Lindau
The 60th Nobel Laureate Meeting at Lindau