Patent Application
20050284146
Solar power plants might be the future electricity generators. The disadvantage is their dependence on direct sunlight, which means no power at nighttime. It has been proposed that fossil-fired power plants provide the power over night. But not only do they cause ecological damage by emitting CO2 and NOx, the fact that they run only a few hours per day causes them to be uneconomical.
Fuel cells could be used if hydrogen is produced by the solar generators during sunshine hours, however the high costs of these cells deters this to be economical in dimensions sufficient for public utilities.
The invention overcomes these disadvantages. According to the invention the solar power generator produces beside electricity for the grid also electricity to split water molecules into 2H2 and O2. The hydrogen and oxygen will be stored for nighttime use. As soon as the solar electricity production falls below the demand, they will be consumed in a highly efficient magneto-plasma-dynamic generator, producing charged ions. This combustion product is a steam plasma with the temperature of a welding torch. It races across a magnetic field that oppositely diverts the positive and negative charge carriers to electrodes running parallel to the gas flow. By this orthogonal splitting of the charge carriers, a large part of the recombination energy converts directly to electricity. Hereby the gas stream looses the energy, which is converted into electricity. The leaving gas-stream then has a lower temperature.
In the last century the magneto-plasma-dynamic generators were proposed as stages for combustion power plants of which a few samples were built. While the theoretical calculation showed that up to 60% of the combustion energy could be converted into electricity, test results showed efficiencies, which did not justify the extra costs. The calculated efficiencies required flame-temperatures above 3,000K. To reach such high temperatures, the combustion gases had to be preheated to 1,300K, which absorbs a large part of the combustion energy. Since in this process a substantial part of the combustion gases consisted of N2, which had to be preheated and partly oxidized to NOx, the process did not only loose sensitive heat but also fusion energy. Because the preheating of the combustion gases could not be avoided this led to the end of the tests.
This disadvantage can be avoided by stoichiometric combustion of oxyhydrogen-gas, which reaches temperatures of 3,300 to 3,500 K. At the same time the forming of the poisonous NOx is avoided, which is in the exhaust-gases of all other high temperature processes. Calculations show that the degree of the ionization doubles if temperature increases by only 10%.
Since the part of the gas-stream, which is not ionized and which reaches only a lower Carnot-quality, but still has a temperature of about 2,000 K when it exits as exhaust-gas, the invention intends to use the kinetic and thermal energy of this exhaust gas stream in a gas turbine, which drives an electric generator. This increases the total efficiency of the aggregation of system components. The exhaust gas of said gas turbine still can be used to drive a further thermodynamic machine. As a preferred solution the invention uses the energy of this secondary exhaust gas stream in a hot-vapor water-splitting unit. The heat of this exhaust gas can also be used for a medium-temperature electrolyzer, even the waste heat of the hot steam-unit may be hot enough to improve the efficiency of the electrolyzer. Both methods reduce the amount of solar electricity, which has to be branched off from the daily solar electricity production for water-splitting.
Instead of magneto-plasma-dynamic generators high-temperature Stirling motors or other combustion engines can be used to drive electric generators. The parts of these machines sliding in one another are preferably made from ceramic and have to be gas-lubricated. The invention intends to use a piston-engine, which burns H2 and O2 in the stoichiometric proportion 2:1. To create a supporting lubrication layer which warrants no contact between the parts the piston is rotated for instance by an electric motor. The still very hot exhaust gases of these engines can be used in a further positive displacement expander engine or turbine. When the exhaust gases are used in a positive displacement expander engine the invention intends to connect the pistons of the two stages with a common concentrically arranged rod, so that only one electric motor is necessary for the rotation of both pistons.
In solar power plants, which predominantly produce hydrogen for industrial use or motor vehicles, it is intended to use natural gas instead of the valuable hydrogen with oxygen—being a by-product of water splitting—for production of electricity for the night hours. Since the content of carbon in natural gas is much smaller than in all other fossil fuels and the nightly electricity consumption is only a small percentage of the total electricity production, the CO2-production is negligible compared to that of today's electricity production.
