WO2008124890A1

WO2008124890A1 - Energy transfer system

Info

Publication number: WO2008124890A1
Application number: PCT/AU2008/000540
Authority: WO
Inventors: Garth Davey
Original assignee: Innovative Design Technology Pty Limited
Priority date: 2007-04-17
Filing date: 2008-04-17
Publication date: 2008-10-23

Abstract

An energy transfer system comprising a multi-stage turbine, or multi-cylinder gas expansion or reciprocating engine, driven by high pressure gas, the high pressure gas being produced by passing liquefied gas through a heat exchanger carrying fluid at ambient temperature to heat the gas to cause the liquefied gas to boil, the exhaust gas of the turbine /engine being fed to a condensing chamber containing an evaporator of a refrigeration cycle operating at a temperature below the condensation temperature of the gas to condense the gas, the condensed gas being transferred by a feed pump back through the heat exchanger to complete the cycle.

Description

TITLE: ENERGY TRANSFER SYSTEM

Introduction

This invention relates to an energy transfer system and more particularly systems utilizing cryogenic turbines .

Background of the Invention

For decades, the world has been grappling with an energy crisis . The environmental consequences of global warming caused by the combustion of fossil fuels, the known downsides of nuclear energy and the dwindling supplies of oil and gas have caused huge interest in alternative energy sources such as solar power, wind power or tidal power .

It is well known that the environment in which we live is full of energy sources that, if correctly harnessed, can be transferred to more practical uses. The harnessing of solar energy to generate electricity is one example. Another example is the use of hydrodynamic issues to generate electricity.

It is the appreciation of readily available energy sources and the use of energy transfer systems that avail themselves of those sources that has brought about the present invention.

Summary of the Invention

According to one aspect of the present invention, there is provided an energy transfer system comprising a multistage turbine, or multi-cylinder gas expansion or reciprocating engine, driven by high pressure gas, the high pressure gas being produced by passing liquefied gas through a heat exchanger carrying fluid at ambient temperature to heat the gas to cause the liquefied gas to boil, the exhaust gas of the turbine/engine being fed to a condensing chamber containing an evaporator of a refrigeration cycle operating at a temperature below the condensation temperature of the gas to condense the gas, the condensed gas being transferred by a feed pump back through the heat exchanger to complete the cycle.

Preferably the high pressure gas that drives the multistage turbine or multi cylinder engine is argon and the refrigerant used in the refrigeration cycle is oxygen.

In a preferred embodiment the energy transfer system essentially comprises two cycles namely a power cycle and a refrigeration cycle. The power cycle uses a closed circuit of argon whilst the refrigeration cycle uses a closed circuit refrigerant of oxygen. Preferably the power cycle comprises a feed pump that feeds liquid argon through the first and second heat exchangers to cause the liquid argon to boil from which it is then fed to a multistage gas turbine which in turn drives a generator, the argon on leaving the turbine is then fed to a condensing chamber which is coupled to part of a refrigeration cycle to cause the nitrogen to condense to be then fed by the feed pump in liquid form back to the first heat exchanger. In a preferred embodiment the first heat exchanger is associated with part of the refrigeration cycle to cool down the refrigerant .

Preferably in the refrigeration cycle liquid oxygen is caused to boil in the condensing chamber to then pass through a compressor from which the gas is passed into the first heat exchanger to be fed to an auxiliary turbine that drives a generator, the oxygen enters and leaves the turbine in liquid form to be then returned to the condensing chamber. Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration of two cycles that make up an energy transfer system.

Figures 2a and 2b are side and perspective views of a first heat exchanger split in half;

Figures 3a and 3b are side and perspective view of an auxiliary heat exchanger split in half;

Figures 4a, 4b and 4c are perspective and elevational views of an alternative heat exchanger that uses ambient air; and

Figures 5a, 5b, 5c and 5d are perspective and elevational views of a bank of cores and ice scrapers that form part of the heat exchanger shown in Figure 4.

Description of the Preferred Embodiment

In the energy transfer system disclosed herein, argon is used to fuel a multi-stage turbine 10. The argon gas exiting the turbine 10 is then fed to a condenser which is coupled to a refrigeration cycle R to condense the argon gas to liquid argon which is then fed back via a feed pump 13 to a heat exchanger 20 fed by sea water to in turn be fed back as a gas to the multi-stage turbine 10 thus defining the power cycle P.

The power cycle P essentially comprises the feed pump 13 that feeds liquid argon to a first heat exchanger 37 which causes the argon to boil . The argon is in turn fed to the second heat exchanger 20 that is preferably fuelled by sea water at ambient temperature to further heat the argon gas which is then fed to the multi-stage turbine 10. The output 11 of the turbine 10 operates a generator 12. The exhaust gases of the turbine 10 are fed directly to the condenser 15. The condenser 15 incorporates an evaporator 16 of a refrigeration cycle R and causes the argon gas to condense so that the liquid argon can then be fed from the condenser 15 to the fuel pump 13 thus completing the power cycle P.

The refrigeration cycle R is fed by liquid oxygen into the condenser 15. The liquid oxygen boils in the evaporator 16 thus drawing heat from the gaseous argon causing the argon to condense. The output 30 of the evaporator 16 feeds the oxygen gas to a compressor 31 which compresses the gas to be fed at high temperature and pressure to the first heat exchanger 37. The heat exchanger 37 cools the oxygen gas until it liquefies by heating up the liquid argon to cause it to boil. The liquid oxygen output 35 of the first heat exchanger 37, still at high pressure, then drives a turbine 36 which may be coupled to an auxiliary generator (not shown) which assists in driving the feed pump 13.. The output of the turbine is in the form of liquid oxygen which is then fed back to the condenser 16 to complete the refrigeration cycle.

Oxygen is specifically used in the refrigeration cycle R because it has a different latent heat of vaporisation and critical point than argon gas . It is thus the latent heat that is used to boil the oxygen in the condenser 15 that is drawn from the argon thus causing the argon to condense to then be returned in liquid form to the feed pump 13.

Although the preferred refrigerant is oxygen, it is understood that other refrigerants include neon, helium R14, R32 or any mixture of these refrigerants and not limited to only these gases . The working gas used in the power cycle whilst it is described as argon is not restricted to this gas and could include gases such as nitrogen, ethane, methane or a mixture of these gases depending on the application.

The power cycle "P" is thus in essence a Rankin power cycle P coupled to reverse Rankin refrigeration cycle R using argon in the power cycle and oxygen in the refrigeration cycle. The only power source is the heat extracted from the sea water in the heat exchanger 20. The power to drive the feed pump 13 and compressor 31 comes from either the generator 12 on the multi-stage gas turbine 10 or the smaller generator on the smaller turbine 36 that is used in the refrigeration cycle R.

As shown in Figure 2, the main heat exchanger 20 is fed, in the preferred embodiment, by seawater at ambient temperatures via an inlet 71 that is well above the boiling point of the argon. The feed pump 13 pumps the liquid argon up to a pressure of about 100 bar and this liquid passes along the passages 72 via an inlet 73 to an outlet 74. The liquid argon boils in the heat exchanger 37 and is further heated in the main heat exchanger 20. The argon gas then reaches the entry of the multi-stage turbine 10 at 100 bar and 300⁰K. The feed pump 13 is a multi-stage centrifugal pump that maintains the pressure of the argon depending on the resistance of the turbine 10. The desired operating entry pressure is 100 bar but this would vary depending on the load on the turbine 10.

The turbine 10 is preferably a five stage turbine. The turbine design has to be capable of dealing with a certain amount of condensation occurring in the last two stages due to the fact that in order to assist in the re- liquification of the working gas the gas has to be expanded along its saturation line. This requirement requires that both the rotor and stator of the latter stages have to have variable angle blades to cater for variations in volume due to saturation occurrences . Furthermore, unlike most multi-stage turbines, the rotors will not be mounted on a common shaft. In the preferred embodiment, it is envisages that stages one, two and three would be on a single shaft 60 with stages four and five operating on separate shafts 61 and 62 each of which independently drive the respective sun and planetary gears in gear set 65. This arrangement allows reduction in peripheral speeds in the latter stages in order to help control the effect of liquid impact on the rotor blades in the final expansion stages. A further option is to provide a controllable by-pass around the last stage of the turbine which can be operated until the desired operating temperature has been reached. The output 11 of the multi-stage turbine 10 drives an alternator 12 but also has a variable tangential drive 19 which can be used to drive the compressor 31 in the refrigeration cycle R. The liquid turbine 36 that is used in the refrigeration cycle R may either directly or indirectly drive the feed pump 13.

The main power turbine 10 can be connected to the alternator 12 via a gearbox for units under 20Mw and directly for units over that size which will usually spin at 3000rmp for 50Hz or 3600rpm for 60Hz.

The multi-stage turbine 10 is designed so that each stage expands the gas by halving the pressure.

Because the outlet side of the turbine 10 operates at very low temperatures close to the condensation point of argon, it is important that the turbine is constructed of materials that can operate at these temperatures . It is also important that the turbine is designed so that there is no need to use conventional lubricants which would freeze at these temperatures. The input energy to drive the cycle comes from the ambient temperature of the seawater which is very high in comparison with the boiling point of liquid argon and the energy that is needed to drive the feed pump 13 comes from the auxiliary generator driven by the turbine 36. The compressor 31 in the refrigeration cycle R is either driven by the output 11 of the turbine 10 or by power generated by the alternator/generator 12.

It is, however, understood that a separate source of electricity can be used to power auxiliary pumps and fans or to start up the cycle.

Although seawater is suggested as the ambient fluid, it is understood that the fluid could include fresh water, waste water, ambient air or any other low grade and readily available heat source.

In another embodiment, ambient air is used to heat the boiled argon in the main heat exchanger and this heat exchanger 100 is illustrated with reference to Figures 4 and 5.

The heat exchanger 100 comprises a casing 101 that has a pair of air inlets 102,103 powered by electric fans 104,105. A series of heat exchanger tubes in banks 106,107 are located within the enclosure and the air outlets 108,109 are shown at either end of the enclosure. The cold argon is fed into the enclosure via an infeed pipe 110 that then branches off to pass through the cores 106,107 of the heat exchanger 100 to exit via a pipe (not shown) on the other side of the heat exchanger. Each core 106,107 is shown in Figures 10 and comprises a pair of spaced cylindrical pipes 112,113 joined by a plurality of equally spaced bridging pipes 115. The bridging pipes 115 are grooved 116 and carry gears 120 that are interconnected. An electric motor (not shown) is coupled to the gears to ensure that they rotate about the tubes . As the heat exchanger operates, the argon gas is heated by the ambient air to a temperature well past its boiling point and this causes a build up of ice on the extremity of the core. The rotating rings cause this ice to be stripped clear of the core to ensure that the core does not become clogged with ice. The ice drops into the base of the heat exchanger to melt and then be collected. The heat exchanger uses the temperature of the ambient air to cause the boiled liquid argon to further heat up, which is then fed to the multi-stage turbine as described above.

Although a multi-stage turbine 10 is used in the preferred embodiment it is understood that this could be replaced by a reciprocating piston and cylinder engine, the cylinders of which would be progressively fuelled by the argon gas at high pressure. The engine would have electronically controlled valves and would have a variable number of cylinders in a variety of configurations.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1 An energy transfer system comprising a multi-stage turbine, or multi-cylinder gas expansion or reciprocating engine, driven by high pressure gas, the high pressure gas being produced by passing liquefied gas through a heat exchanger carrying fluid at ambient temperature to heat the gas to cause the liquefied gas to boil, the exhaust gas of the turbine/engine being fed to a condensing chamber containing an evaporator of a refrigeration cycle operating at a temperature below the condensation temperature of the gas to condense the gas, the condensed gas being transferred by a feed pump back through the heat exchanger to complete the cycle.

2 The energy transfer system according to claim 1 wherein the high pressure gas that drives the turbine or engine is argon and the refrigerant used in the refrigeration cycle is oxygen.

3 The energy transfer system according to either claim 1 or claim 2 wherein the condensed gas is pumped through a first heat exchanger that is coupled to the refrigeration cycle and then through the heat exchanger which carries fluid at ambient temperature.

4 The energy transfer system according to claim 3 wherein the refrigerant leaves the evaporator in the condensing chamber as a gas, and is compressed in an externally driven compressor, passed through the first heat exchanger to liquefy the gas which is then used to drive a turbine to then return to the evaporator as a liquid.

5 The energy transfer system according to claim 4 wherein the output of the turbine drives a generator. 6 The energy transfer system according to any one of the preceding claims wherein the output of the multi-stage turbine or engine drives a generator.

7 The energy transfer system according to either claim 5 or claim 6 wherein the generator powers the feed pump and compressor in the refrigeration cycle.

8 The energy transfer system according to claim 4 wherein the output of the multi-stage turbine or engine drives the compressor in the refrigeration cycle.

9 The energy transfer system according to any one of the preceding claims wherein a five stage turbine has stages one, two and three driven by a common drive shaft but stages four and five are driven by independent drive shafts with all the drive shafts interconnected through a planetary gear train.

10 The energy transfer system according to any one of the preceding claims wherein the entry gas pressure of the multi-stage turbine is about 100 bar and the exit gas pressure is about 2 bar.

11 The energy transfer system according to any one of the preceding claims wherein the entry gas temperature of the multi-stage turbine is about 300⁰K and the exit temperature is about 90⁰K.

12 The energy transfer system according to any one of the preceding claims wherein the heat exchanger carrying fluid ambient temperature heats the incoming gas from about 138°K to 300⁰K.

13 The energy transfer system according to any one of the preceding claims wherein the ambient fluid is either sea water, fresh water, waste water or ambient air, or any other low grade heat source .