Method, system and process for passive energy recovery in high pressure gas energy systems

Description of the invention Technical field of the invention

[0001] The present invention relates to method, system and process for passive energy recovery in high pressure gas energy systems. More particularly, the invention relates to the use of cylinders gas assembly with a precision multistage turbomachine and a generator.

Background of the invention

[0002] Gaseous fuel-based energy power systems which use pressurized compressed gases for their operation are becoming common these days because of higher range, easy refilling, unexpected demand of petroleum-based fuels and advantages of reduced emissions. CNG/LPG/Propylene based internal combustion engines and Hydrogen/Methane/Propane/Ethane based fuel cell systems which run on pressurized gases have become a viable solution to overcome the fossil fuel demand and its environmental effect. [0003] Compressed natural gas CNG/Liquefied petroleum gas LPG combusted pressurized energy systems utilize chemical energy by combustion of the stored fuel using internal combustion engine. The internal combustion engine is attached to the pressurized cylinders by using a set of multistage pressure regulators. The fuel gases are stored at a pressure of 250 bar capacity. The gas is brought down to less than 5 bars before sending to the internal combustion engine for combustion. The compressed natural gas and liquefied propylene gas based systems operate at minimum of 5 bars pressure before a refill is required. [0004] Electrochemical power devices such as Proton Exchange Membrane Fuel Cell system and Solid Oxide Fuel Cell system are two types of fuel cells which use compressed gases. In Proton Exchange Membrane Fuel Cells compressed Hydrogen is used as a fuel for operation while in Solid Oxide Fuel Cell systems, compressed Methane/Ethane/Propane is used as fuel for operation. In fuel cells, the compressed gas is stored at a pressure of 700 bars. The gas is brought down to less than 5 bars for sending it for electrochemical consumption inside a fuel cell stack. These systems operate at minimum of 5 bar pressure before a refill is required. This is how the currently designed systems operate by utilizing only the chemical energy.

[0005] For higher operational power capacity, gas storage systems rely on pressurized chamber to store as much gaseous fuel as possible which translates to more range density. Hence the pressure of these gases may be higher than 250/700 bars.

[0006] In both internal combustion engine and fuel cell systems, the gas pressure is lowered from pressurized to operating range using multi-staged regulators, which include both a manual high-pressure regulator and an electronic pressure regulator which is used to meet power requirements accurately. The first regulator is a manual high-pressure diaphragm or a spring-based regulator which reduces the pressure from stored pressure to a lower value and the second regulator is an electronic pressure regulator which regulates this lower value pressure to adjust to lower pressure as per power demand. The problem with using a diaphragm or a spring-based regulator is that potential energy is transformed to diaphragm or a spring and hence no substantial work is derived from the state these pressurized gases are in.

[0007] Patent document US20120228040A1 titled“ Hybrid vehicle with exhaust powered turbo generator” discloses a hybrid vehicle employing an internal combustion engine and an electric drive. The hybrid vehicle includes a turbine powered by exhaust gases from the internal combustion engine. The turbine drives a generator which provides electrical power to the electric drive motor and the battery. Further, the exhaust gas energy recovery system may be used with a serial hybrid system or a parallel hybrid system.

[0008] Patent document US6591926B2 titled“ System and method for recovering energy of a hydrogen gas fuel supply for use in a vehicle discloses a system for recovering the potential energy of hydrogen gas fuel supply within a fuel cell powered vehicle. The invention relates to a system which selectively channels pressurized hydrogen gas through energy conversion unit which lowers the pressure of hydrogen gas and generates electricity. A controller causes the generated electricity to be selectively communicated to compressor, electrical accessories and battery using a switching module, based on the vehicle attribute data received from sensors.

[0009] Patent document US20120067304A1 titled “ Economical Hybrid fuel” discloses a system and method of recovering waste energy from engine and converting it to usable energy whereby the fuel requirement is reduced and pollution is diminished.

[0010] Patent document US8874291B2 titled“ Electricity generating suspension system for hybrid and electric automobiles” discloses a vehicle for transporting which at least partially uses electrical energy and wherein the electrical energy is substantially produced within the vehicle by converting kinetic energy generated in the vehicle during its motion to electrical energy and stored temporarily.

[0011] Hence, in order to overcome the disadvantages that exist in the state of the art, there is a need for a method and system which can effectively recover energy in automotive and stationary systems which run on pressurized gaseous fuels and thus increase the power output as a function of the supplied energy in the system during refueling.

Summary of the Invention

[0012] The present invention overcomes the drawbacks in the prior art and provides method, system for passive energy recovery in high pressure gas energy systems. The system for recovering reserve energy comprises a precision multistage turbomachine installed after a pressurized fuel cylinder to reduce the pressure of a fed gaseous fuel. The multistage turbomachine reduces the pressure of the fed gaseous fuel from 50 bar onwards. A generator is connected to a shaft of the multistage turbomachine to convert the potential energy of the pressurized gas in cylinders to electrical energy.

[0013] A power conditioning unit is used for stabilizing the generated DC power and converting direct current (DC) power to alternative current (AC) power to charge batteries. A filter is attached after the turbocharger to remove contamination in the outlet fuel gas. A heat exchanger is used for fuel gas temperature conditioning. The heat exchanger increases the temperature of the fuel gas to working temperature requirements of the fuel cell stack.

[0014] An electronic pressure regulator is used to adjust the fuel pressure before the fuel gas enters the fuel cell stack.

[0015] Thus, the invention provides a method and system for passive energy recovery in high pressure gas energy systems. The method and system which effectively recover energy in automotive and stationary systems which run on pressurized gaseous fuels and thus increase the power output as a function of the supplied energy in the system during refueling.

Brief description of the drawings

[0016] The foregoing and other features of embodiments will become more apparent from the following detailed description of embodiments when read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.

[0017] Figure 1 illustrates a block diagram of a system of for recovering reserve energy from pressurized gas energy systems using an energy device consisting of subsystems namely a turbomachine, alternator and heat exchanger for both internal combustion engine and fuel cell systems. [0018] Figure 2 illustrates a flow diagram of a method to recover the reserve potential energy from pressurized gas system.

[0019] Figure 3 illustrates a flow diagram of a manual/electronic pressure regulators in either stationary or moving energy systems for free energy in the long run.

Detailed description of the invention

[0020] Reference will now be made in detail to the description of the present subject matter, one or more examples of which are shown in figures. Each example is provided to explain the subject matter and not a limitation. Various changes and modifications obvious to one skilled in the art to which the invention pertains are deemed to be within the spirit, scope and contemplation of the invention.

[0021] In order to more clearly and concisely describe and point out the subject matter of the claimed invention, the following definitions are provided for specific terms, which are used in the following written description.

[0022] The term‘ pressurized gas-based energy systems’ describes the systems which runs on pressurized gaseous fuels, usually carbon hydrogen compounds stored in pressurized cylinders either composite or reinforced. The gases are typically stored at pressure greater than 5 bars. At the time of expansion of the gaseous fuel in turbomachine, the pressure is reduced, there is change in enthalpy and thereby constituting a reserve energy of the system which is discarded in the conventional energy systems.

[0023] According to the present invention, the reserve energy of high-pressure gaseous fuel is effectively recovered using below describes turbomachine to provide conditioned fuel using an additional gas conditioning unit as per the power demand. The turbo expander operations and its basic parts are described below. [0024] The turbo expander is a multiple staged expansion device comprising a turbine wheel, nozzles, diffuser, the shaft, two journal bearings and two thrust bearings and appropriate housing.

[0025] The system of the present invention includes a high-pressure ratio turbo machine coupled to a heat exchange mechanism for gas conditioning and a power AC (a) synchronous generator, which extract reserve energy of the gases and simultaneously charges a battery/capacitor bank.

[0026] The system of the present invention replaces at least one pressurized regulator in the existing systems with turbomachine connected to single or hybrid power systems via suitable power distribution unit and power conditioning unit for conditioning DC power to either DC regulated power or AC power.

[0027] The present invention is an integrated system which includes a turbomachine, altemator/generator and a heat exchanger for further temperature regulation of the fuel before it enters the power generating device such as fuel cell stack or an internal combustion engine.

[0028] According to the present invention a single multistage radial turbomachine fitted with suitable bearings (air bearings for oil-less system used in the invention) is installed after the high-pressure cylinders to fully or partially recover pressure energy partially and thereby reduce pressure of tanks, if further down the pressure line the gas is consumed chemically. The pressure of compressed gas at the inlet of designed turbomachine is minimum 50 bars in case of hydrogen fuel tank and 5 bar for internal combustion engines. The electrical power generated alternator is function of pressure difference between tank pressure and designed outlet pressure of turbomachine. The gas movement happens because of pressure difference P _{cyi -} Pnominal or design pressure within the turbomachine. During steady operating condition the gases behave as continuum. The advantage of this method is that no feedback is taken from any sensors to regulate the pressure of gaseous fuel in and out of the turbocharger.

[0029] The system of the present invention includes a heat exchanger for fuel gas temperature conditioning connected to the turbomachine. The heat exchanger or any other method of curing the gas ensures that the temperature of the fuel gas can be increased to working temperature requirements of the fuel cell stack or internal combustion engine for its prolonged life. Heat exchanger conditions the gas for nominal temperature.

[0030] The generator/altemator is connected to batteries/capacitors either for single or hybrid systems.

[0031] In the present invention, at the outlet of the gas conditioning unit is a suitable manual/Electronic Pressure Regulator which is fixed to further adjust the fuel pressure before it enters the fuel cell stack or the internal combustion engine.

[0032] Power conditioning unit in the power distribution system is used for adjusting DC power and converting it to AC power, if required. The power conditioning unit can be inbuilt the alternator or separate unit.

[0033] A suitable filter is attached after the turbocharger to remove contamination and impurities when oil is used in the turbocharger.

[0034] Figure 1 illustrates a block diagram of the system for recovering reserve energy from pressurized gas energy systems. According to figure 1, the system (1) for recovering reserve energy consists of a precision multistage turbomachine (3) installed after the pressurized fuel cylinder (2) to reduce pressure from a range of 50 bar onwards. A suitable generator/altemator (4) connected to the shaft of a turbocharger is to convert the potential energy of the pressurized gas in cylinders to electrical energy. The power conditioning unit (9) is used for stabilizing DC power and converting it to AC power to charge the batteries and the batteries may inbuilt in the assembly (10). A suitable filter (5) is attached after the turbocharger to remove contamination in the outlet fuel gas. A heat exchanger (6) for fuel gas temperature conditioning ensures that the temperature of the fuel gas is increased to the working temperature requirements of the fuel cell stack or internal combustion engine.

[0035] The turbomachine (3) reduces the pressure of the inlet fuel by using a rotating rotor assembly fixed on to a shaft using suitable bearing assembly which is covered under stator and shroud assembly, where inlet of the turbocharger is connected to pressurized cylinders via suitable piping and outlet of the turbocharger is connected to a suitable heat exchanger (6). Suitable optimal geometry of the turbine leads to required pressure at the outlet. Further, the system (1) does not necessitate any feedback from sensors and there is a lag of a few seconds for the output power to reach maximum.

[0036] Figure 2 illustrates a flow diagram of a method to recover the reserve potential energy from pressurized gas system. The method to recover the reserve potential energy from pressurized gas system which runs on carbon and hydrogen compounds (10) comprises the steps of feeding the pressurized gaseous fuel to a turbomachine (3) at step 11. The turbomachine (3) reduces the pressure of the fed gaseous fuel. At step 12, the method converts the reserve energy of pressurized gas with the help of the generator (4) to electrical energy. The method stabilizes the generated direct current (DC) power and converts the direct current (DC) power to alternative current (AC) power at step 13 to charge batteries (10) in either stationary or automotive systems.

[0037] Figure 3 illustrates a flow diagram of a manual/electronic pressure regulators in either stationary or moving energy systems for free energy in the long run. The method to replace one or more manual/electronic pressure regulators in either stationary or moving energy systems for free energy in the long run. At step 21, the method removes the contamination in the outlet gas in case of turbomachine (3). At step 22, the method feeds the pressure reduced gaseous fuel to the heat exchanger (6) for fuel gas temperature conditioning and directs the gaseous fuel (7) from the heat exchanger (6) to an electronic pressure regulator. The method further adjusts the fuel pressure before it enters the fuel cell stack or the internal combustion engine (8) by using an electronic pressure regulator (7) at step 23. Feedback from any sensors to regulate the pressure of gaseous fuel in and out of the turbocharger. Further, there are no bypass valves to regulate the outlet gas pressure in the turbocharger.

[0038] An important advantage of the present invention is that it increases the power range of the system by at least 100% and thus lowering operational costs by half. Thus, the present invention intends to replace at least in part a manual/electric regulator to bring down the pressure of pressurized gaseous fuel. The invention utilizes the reserve potential energy stored in mentioned compressed gaseous fuel. This is extracted with the help of designed turbomachine (3) power generation unit and gas conditioning unit (9) and an additional charging bank or ports it back to the grid . For all practical purposes, this process is a non-adiabatic and isentropic process.

[0039] While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.