Abstract: A fuel cell system in which methanol is supplied in liquid form to the fuel cells (so-called Direct Methanol Fuel Cell (DMFC) system) with a container containing a supply of methanol, a conduit line designed to supply liquid methanol leading from the container to the fuel cells, another conduit line running from the fuel cells back to the container, a nozzle present in the other line and a pressure-boosting pump present in the conduit system, characterized by the fact that the pump is arranged in the conduit line leading from the container to the fuel cells, and a cooler is preferably arranged in the conduit line leading from the container to the fuel cells. In this way, one succeeds in supplying the fuel cells with a liquid fuel which is undersaturated with CO2 and therefore can absorb CO2 forming in the fuel cells so that as little gaseous CO2 as possible is contained in the fuel cell system, thus increasing the power of the system.

Abstract: A fuel cell system is described with a so-called direct methanol fuel cell (DMFC). To minimize the methanol crossover the concentration of the methanol/water mixture supplied to the anode of the fuel cell is made dependent on the magnitude of the electrical power takeoff. In order to be able to adapt the concentration of the methanol quickly in the case of a load change, it is proposed that a separating column be introduced into the anode cycle which reduces the concentration of the methanol. To achieve adapted increases in the concentration of methanol, both a concentrated methanol/water mixture from a secondary cycle and possibly additionally pure methanol from a tank are supplied. In the case of a reduction in the power demand only the secondary cycle needs to be blocked with the result that a lean mixture is available immediately.

Abstract: A fuel cell system is described whose fuel cell is driven with a methanol-water mixture. The problem with such systems is that at the outlet from the cathode, as a result of the chemical reaction in the fuel cell, carbon dioxide is present which must be removed from the anode cycle. The previously known systems, however, have the disadvantage that water and methanol are also discharged simultaneously with the discharge of CO2 in so-called vapor separators, and therefore are no longer available as energy carriers. Therefore, systems have already been proposed in which the liquid-vapor mixture is cooled before entering the vapor separator. In addition, combinations of several vapor separators are proposed. The present invention is related to this and proposes that the gas containing methanol emerging from a high temperature vapor separator be fed via a branch-stream cooler to the liquid accumulation of a low temperature vapor separator in a low temperature path.

Abstract: A fuel cell system is described with a so-called direct methanol fuel cell (DMFC). To minimize the methanol crossover the concentration of the methanol/water mixture supplied to the anode of the fuel cell is made dependent on the magnitude of the electrical power takeoff. In order to be able to adapt the concentration of the methanol quickly in the case of a load change, it is proposed that a separating column be introduced into the anode cycle which reduces the concentration of the methanol. To achieve adapted increases in the concentration of methanol, both a concentrated methanol/water mixture from a secondary cycle and possibly additionally pure methanol from a tank are supplied. In the case of a reduction in the power demand only the secondary cycle needs to be blocked with the result that a lean mixture is available immediately.

Abstract: A fuel cell system in which methanol is supplied in liquid form to the fuel cells (so-called Direct Methanol Fuel Cell (DMFC) system) with a container containing a supply of methanol, a conduit line designed to supply liquid methanol leading from the container to the fuel cells, another conduit line running from the fuel cells back to the container, a nozzle present in the other line and a pressure-boosting pump present in the conduit system, characterized by the fact that the pump is arranged in the conduit line leading from the container to the fuel cells, and a cooler is preferably arranged in the conduit line leading from the container to the fuel cells. In this way, one succeeds in supplying the fuel cells with a liquid fuel which is undersaturated with CO2 and therefore can absorb CO2 forming in the fuel cells so that as little gaseous CO2 as possible is contained in the fuel cell system, thus increasing the power of the system.

Abstract: A fuel cell system is described whose fuel cell is driven with a methanol-water mixture. The problem with such systems is that at the outlet from the cathode, as a result of the chemical reaction in the fuel cell, carbon dioxide is present which must be removed from the anode cycle. The previously known systems, however, have the disadvantage that water and methanol are also discharged simultaneously with the discharge of CO2 in so-called vapor separators, and therefore are no longer available as energy carriers. Therefore, systems have already been proposed in which the liquid-vapor mixture is cooled before entering the vapor separator. In addition, combinations of several vapor separators are proposed. The present invention is related to this and proposes that the gas containing methanol emerging from a high temperature vapor separator be fed via a branch-stream cooler to the liquid accumulation of a low temperature vapor separator in a low temperature path.

Abstract: A fuel cell system having two fuel cell stacks with different operating temperatures, i.e. a low temperature stack (LT stack) and a high temperature stack (HT stack). The high temperature stack is connected in front of the low temperature stack with respect to the process flow of fuel through the fuel cell system.