ORC for transforming waste heat from a heat source into mechanical energy and compressor installation making use of such an ORC

An Organic Rankine Cycle (ORC) installation for transforming waste heat from a heat source containing compressed gas into mechanical energy, the ORC comprising:

• a closed circuit containing a two-phase working fluid,
• the closed circuit comprising a liquid pump for circulating the two-phase working fluid in the closed circuit consecutively through an evaporator which is in thermal contact with the heat source;
• through an expander for transforming the thermal energy of the two-phase working fluid into mechanical energy;
• and through a condenser which is in thermal contact with a cooling element,
• wherein the ORC installation is equipped with a determiner of mechanical energy generated by the expander and a control device that regulates a vapor fraction of the two-phase working fluid entering the expander,
• wherein the control device is configured to regulate the vapor fraction based on the determined mechanical energy such that the mechanical energy generated by the expander is maximum and wherein the expander is configured to accept a mixture of liquid and gaseous working fluid,
• wherein the control device is configured to regulate the vapor fraction of the working fluid entering the expander, by varying the working fluid flow through the pump and/or by varying the working fluid flow through the expander,
• wherein the vapor fraction of the working fluid entering the expander is further regulated by switching repeatedly between two control algorithms, whereby the first control algorithm consists of varying the working fluid flow through the pump until the mechanical energy generated by the expander is at a local maximum and the second control algorithm consists of varying the working fluid flow through the expander until the mechanical energy generated by the expander is at a further optimized maximum.

A compressor installation comprising:

• a compressor element for compressing a gas and a cooler for cooling the compressed gas, and
• an ORC installation for transforming waste heat from a heat source containing compressed gas into mechanical energy, the ORC comprising:
• a closed circuit containing a two-phase working fluid,
• the closed circuit comprising a liquid pump for circulating the two-phase working fluid in the closed circuit consecutively through an evaporator which is in thermal contact with the heat source;
• through an expander for transforming the thermal energy of the two-phase working fluid into mechanical energy;
• and through a condenser which is in thermal contact with a cooling element,
• wherein the ORC installation is equipped with a determiner of output power generated by the expander and a control device that regulates a vapor fraction of the two-phase working fluid entering the expander,
• wherein the control device is configured to regulate the vapor fraction based on the output power such that the output power generated by the expander is maximum and wherein the expander is configured to accept a mixture of liquid and gaseous working fluid,
• wherein the cooler is integrated in an heat exchanger which also integrates the evaporator of the ORC for heat transfer between the cooler and the evaporator,
• wherein the determiner is a power meter or a power sensor that measures the output power generated by the expander.