Process and device for using of low temperature heat for the production of electrical energy

Abstract

The invention relates to the using of low temperature heat for the production of electrical energy by using of supercritical carbon dioxide as working fluid. It included a process and a device for process realizing with higher efficiency in relation to other known processes and with a wide temperature working range. This is related to a wider adjustability which allows an optimal operation both in summer and in winter operation without technical or constructional changes. The process is realizable without damages to the environment and is realizable with low effort. The relative emission of carbon dioxide is reduced in relation to other processes. Low temperature heat from a given heat source ( 1 ) is taken off by carbon dioxide at high supercritical pressure as heat transfer and working fluid in the process. Then the heated fluid is expanding in an expansion machine ( 2 ), which is connected with a generator ( 3 ) for the production of electric power. In this process the fluid will be cooled, then liquefied by using of a cold source ( 4 ) and in liquid state compressed to the working pressure.

1 . A process for using of low temperature heat for the production of electric power, the process comprising:
 using supercritical carbon dioxide as working fluid, in which high compressed supercritical carbon dioxide as heat transfer fluid takes off low temperature heat of a heat source and then is expanded in a labor-producing expansion machine, which is connected with a generator, is cooled in this process and liquefied by means of a cold source, then increased of pressure by a pump for liquids to the working pressure and stored in a high pressure interim storage.   
     
     
         2 . A process as claimed in  claim 1 , wherein the labor-producing expansion is made into the range of vapor-liquid-equilibrium with a partial condensation of carbon dioxide and the vapor-liquid-mixture is liquefied totally by means of a cold source, then increased of pressure by a pump for liquids to the working pressure and stored in a high pressure interim storage. 
     
     
         3 . A process as claimed in  claim 1 , wherein as interim storages are used salt caverns in big depth. 
     
     
         4 . A process as claimed in  claim 1 , wherein the waste heat of a power station is used as heat source. 
     
     
         5 . A process as claimed in  claim 1 , wherein the waste heat of motors is used as heat source. 
     
     
         6 . A process as claimed in  claim 1 , wherein the waste heat of machines and plants is used as heat source. 
     
     
         7 . A process as claimed in  claim 1 , wherein geothermal energy is used as heat source. 
     
     
         8 . A process as claimed in  claim 1 , wherein solar energy is used as heat source. 
     
     
         9 . A process as claimed in  claim 1 , wherein the geothermal potential in depth of 5 to 30 meters is used as cold source for the liquefaction of the carbon dioxide at last partially. 
     
     
         10 . A process as claimed in  claim 1 , wherein the ambient air or substances which are tempered by the ambient air are used as cold source for the liquefaction of the carbon dioxide at last partially. 
     
     
         11 . A process as claimed in  claim 1 , wherein deep water of seas, rivers or oceans or substances which are tempered by deep water are used as cold source for the liquefaction of the carbon dioxide at last partially. 
     
     
         12 . A process as claimed in  claim 1 , wherein the cold energy of the expansion of compressed air or natural gas or substances which are tempered by the cold energy of the expansion are used as cold source for the liquefaction of the carbon dioxide at last partially. 
     
     
         13 . A process as claimed in  claim 1 , wherein the labor-producing two-stage expansion is characterized by an expansion into the two-phase region in the first step by separating of the gas part and using of a liquid part of this stream for cooling of the whole stream for the expansion, in this process will be the stream heated and then in a second step expanded to lower pressures, then used for the cooling and liquefying of the first gas stream and after them compressed and assembled with the liquefied first gas part and in the liquid form compressed to the working pressure. 
     
     
         14 . A process as claimed in  claim 1 , wherein the salt caverns in the process are used both storages for carbon dioxide in the supercritical high pressure state and geothermic heat sources and heat exchanger, through which the potential of the carbon dioxide emission is lowered additional 
     
     
         15 . A process as claimed in  claim 1 , wherein the liquefaction takes place in the earth near the surface of the earth and the depth storage in more than 400 meters because the high pressure of the carbon dioxide of 10 MPa at least by safety reasons and the high static pressure the costs of the compression reduces. 
     
     
         16 . A process as claimed in  claim 1 , wherein the process is operating in joint with a peak load power station of natural gas basis and operating discontinuously, through which the excess energy is used to load natural gas, compressed air and carbon dioxide in underground buffers under high pressure and, when needed, to take off air and natural gas discontinuously and the storage for carbon dioxide to use both as buffer storage and as geothermal heat source for the working fluid. 
     
     
         17 . A device realizing the process as claimed in  claim 1 , wherein is used at least a given heat source, a heat exchanger with liquefying function, a medium for the heat transfer, an expansion machine, a generator which is connected with the expansion machine, a pump for the compression of the liquid carbon dioxide, a buffer for the storage of the liquid working fluid, control devices and valves.