According to IFO-Energy Unlimited in Hungary, creators of an untethered, autonomous flying wind power plant, there are at least three well known problems of conventional wind energy production, firstly there are fluctuations and the unsteady nature of surface winds and these fluctuations in wind energy production put stress on the power system so capacity reserves (surplus power plants) are necessary to ensure system reliability.
Another problem of wind power plants is their low efficiency. A wind turbine will generate around 20-30% of its maximum rated capacity depending on the location of the plant, which means that if we want to utilize wind power in large volumes we have to build wind power plants as far as the eye can see.
The third common problem is that wind power suffers from a lack of energy density, that is, not only large numbers of wind generators (and thus large land areas) are required to produce useful amounts of electricity but huge dimensions too.
Therefore, the idea of harnessing high altitude winds blowing at 10,000 meters altitude seems to be promising.
Wind towers or tethered floating devices are not the only way to harvest energy from the atmosphere as un-tethered flying units are also capable of harvesting wind energy. In order to do away with tethering, the device would need to use the updrafts and ‘dynamic soaring’ using the energy in wind gradients commonly used by soaring birds.
The storage of energy would need to be considered and according to one of the possibilities an air liquefaction machine is set in motion letting the produced liquid air be the energy storing medium. There is no need to forward the liquid air to the ground continuously, e.g. by means of a pipeline. It can be done in distinct doses, in so called „quanta”, by means of GPS-guided parafoils. Another way is applying molten salt energy storage systems, utilizing heat of fusion. Research is going on all over the world to find even larger heat effects for energy storing, e.g. heat of formation of chemical substances instead of heat of fusion. These investigations are very promising also for IFO’s project.
In the simplest case an un-tethered autonomous flying energy-harvesting unit as well as a receiver ground-station are integral parts of the complete system. These two physically detached parts constitute a logistic unit, and their collaboration according to a fixed timetable ensures the realization of the invention. A ground-station could support several flying units.
The IFO-Energy Unlimited invention is based on several well known technical solutions, but the result of their synthesis and unique application yield new routes and so far unutilized possibilities in wind energy production. Some of these benefits and possibilities include greater intensity with smaller equipment and because the storing of energy as liquid air is the central idea of the invention means that there could always be great reserves of liquid air available at the ground-station. The “warm” heat sink of this thermal power plant is the ambient air, so it does not need a heat up period prior to start. It is always ready to run and can function as a peak-load power plant.
By warming up the liquid air and expanding it we get work at the expense of ambient heat. When this work finally degrades into heat, the thermal balance of the local system is zero. The machines are running, but no waste heat is produced at the point where the energy is used.
Onboard superconducting technology – Superconductivity is a phenomenon characterized by the resistance of certain materials dropping to exactly zero, when cooled below a critical temperature. It was discovered that some materials have critical temperatures above 90 kelvins. Since the boiling point of liquid air at ambient pressure is 79 kelvins, this means that many commercial applications are feasible using the liquid air produced in virtually boundless amounts by the flying wind power plant. These high-temperature superconductors make it possible to apply high-performance superconducting electric motors and generators, power storage devices, fault current limiters, as well as complex systems such as power stations based on this project.
As liquid air can be the fuel of a thermal power plant, so it can be used as a fuel in the propulsion of vehicles. The benefits can be used in a complex system, namely in urban traffic. In this case, the smaller energy content of the cryogenic fuel is not a serious problem. Applying a kinetic energy recovery system (KERS), the demand for external energy can be significantly lowered recovering the energy of the frequent braking. As the high-temperature superconductor technology is already “onboard”, the possibility is given to benefit from the advantages of high performance electric motors and power storage devices. Today, everything is ready for the utilization of this technology only the large amount of cheap cryogenic fuel (liquid air rather than liquid nitrogen) is missing. Should this proposal be put into operation, the pollution due to the urban traffic could be eliminated at once.
The invention is based on well known technical solutions, but the result of their synthesis and unique application has yielded new routes and so far unutilized possibilities in wind energy production. The invention is easible but the details need significant further R&D, as well as investment.