Power cycle and system for utilizing moderate temperature heat sources

• US 7,021,060 B1
• Filed: 03/01/2005
• Issued: 04/04/2006
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Kalina Power Limited
• Original Assignee: Kalex Systems LLC
• Inventors: Kalina, Alexander I.
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US11/069,937
• Time in Patent Office: 399 Days
• Field of Search: 606/49, 606/51, 606/53, 606/71
• US Class Current: 60/649
• CPC Class Codes: F01K 25/06 using mixtures of different fluids plants using mixtures of steam and gas F01K21/04

Abstract

A new thermodynamic cycle is disclosed for converting energy from a moderate temperature stream, external source into useable energy using a working fluid comprising of a mixture of a low boiling component and a higher boiling component and including a higher pressure circuit and a lower pressure circuit. The cycle is designed to improve the efficiency of the energy extraction process by recirculating a portion of a liquid stream prior to further cooling. The new thermodynamic process and system for accomplishing the improved efficiency is especially well-suited for streams from moderate-temperature geothermal sources.

Claims

1. A method comprising the steps of:

transforming a portion of thermal energy in a superheated vapor stream into usable energy to produce a spent stream;

transferring thermal energy from an external heat source stream to a first vapor stream to form the superheated vapor stream and a first cooled external heat source stream;

transferring thermal energy from the first cooled external heat source stream to a first mixed stream to form the first vapor stream and a second cooled external heat source stream;

transferring thermal energy from the spent stream to a first pre-heated higher pressure, basic working fluid substream to form a partially condensed spent stream and a first heated, higher pressure, basic working fluid substream;

transferring thermal energy from a third cooled external heat source substream to a second pre-heated higher pressure, basic working fluid substream to form a second heated, higher pressure, basic working fluid substream and a first cooled external heat source substream;

combining the first and second heated, higher pressure basic working fluid substreams to form a combined heated, higher pressure basic working fluid stream;

transferring thermal energy from a first portion of the second cooled external heat source stream to the combined heated, higher pressure basic working fluid stream to form a higher temperature, higher pressure, basic working fluid stream and the third cooled external heat source substream;

separating the partially condensed spent stream into a separated vapor stream and a separated liquid stream;

pressurizing a first portion of the separated liquid stream to a pressure equal to a pressure of the combined higher temperature, higher pressure basic working fluid stream to form a pressurized liquid stream;

transferring thermal energy from a second portion of the second cooled external heat source stream to the pressurized liquid stream to form a second mixed stream and a fourth cooled external heat source substream;

combining the second mixed stream with the combined higher temperature, higher pressure basic working fluid stream to form the first mixed stream;

combining a second portion of the separated liquid stream with the separated vapor stream to from a lower pressure, basic working fluid stream;

transferring thermal energy from the lower pressure, basic working fluid stream to a higher pressure, basic working fluid stream to form a pre-heated, higher pressure, basic working fluid stream and a cooled, lower pressure, basic working fluid stream;

transferring thermal energy from the cooled, lower pressure, basic working fluid stream to an external coolant stream to from a spent external coolant stream and a fully condensed, lower pressure, basic working fluid stream; and

pressurizing the fully condensed, lower pressure, basic working fluid stream to the higher pressure, basic working fluid stream.