Patent Description:
The invention relates to a boosting gas turbine system for providing combined cooling, heating, and power (CCHP), and specifically to a boosting CCHP gas turbine system which is compact, energy efficient, and suitable for use with micro-turbines.

CCHP gas turbines provide energy that can be used for cooling, heating, and electrical power. Typically cooling is generated by absorption technology, heating by the flow of hot turbine exhaust gas, and electrical power by rotating the shaft of an electric alternator.

Cooling by absorption technology requires the use of large volume components, such as air cooling towers, and is typically unsuitable for use with compact CCHP turbines, such as micro-turbines.

In micro-turbines fueled by natural gas (NG), such as those used in urban areas, the NG supply is at a low pressure, e.g. <NUM> bar. In such cases, a fuel compressor is needed to boost the fuel pressure into the turbine compressor to approximately <NUM> bar. A typical fuel compressor consumes about <NUM>% of the electrical energy output of the micro-turbine. The weight and cost of the overall system are increased because of the wasted electrical energy and added weight of the fuel compressor.

<CIT>, and entitled "Integrated Cooling, Heating, and Power Systems", provides a single-effect absorption chiller, including an absorber operatively connected to a solution heat exchanger and a generator, and a condenser in fluid communication with the absorber, wherein the absorber is sized and configured to receive a feed of water from a source of water and to transfer heat to the feed of water and then to convey the feed of water to the condenser without further heat conditioning of the feed of water prior to its entry into the condenser, and wherein the condenser is sized and configured to receive the feed of water from the absorber and to transfer heat to the feed of water, thereby cooling the condenser without resorting to an external heat exchanger.

<CIT>, and entitled "System and Method for Improving Output and Heat Rate for a Liquid Natural Gas Combined Cycle Power Plant", discloses a combined cycle power plant and heating and cooling system and method for the power plant having a liquid natural gas supply and a vaporizer configured to vaporize the liquid natural gas into natural gas that is supplied to a gas performance heater before entering a combustion section of a gas turbine. A closed cooling water circuit is in fluid communication with at least one power plant component such as a gas turbine inlet heating/cooling coil, a heat recovery heat exchanger, the vaporizer, and mixtures thereof. An open cooling water circuit is in fluid communication with at least one power plant component such as at least one steam turbine condenser, the heat recovery heat exchanger, and mixtures thereof.

US patent application publication <CIT>, and entitled "Humid Air Turbine Power, Water Extraction, and Refrigeration Cycle", teaches a combined heat and power (CHP) system which includes a turbine system, a turbocharger system, and a refrigeration system. The refrigeration system can receive combustion products from the turbine system and compressed air from the turbocharger system. The refrigeration system can cool the combustion products and the compressed air to generate a cooled combustion product mixture that is provided to the turbine system.

These contemporary CCHP systems exhibit several drawbacks. Absorption chillers typically have a low coefficient of performance (COP) and are too massive for use in a compact CCHP system. Furthermore, Liquefied Natural Gas (LNG) is a relatively expensive fuel, and is not readily available in many geographical locations.

The present invention is directed to embodiments of a boosting CCHP gas turbine system, which incorporates a pressure booster and has low weight and high energy efficiency according to the appended claims.

According to the invention, the boosting CCHP gas system has a pressure booster and a turbo-compressor. The pressure booster includes a fuel inlet, a fuel outlet, and a piston, and is in fluid communication with a gas turbine engine. The pressure booster also includes a coolant inlet, a coolant chamber, and a coolant outlet, and is in fluid communication with a closed pressurized coolant flow. The turbo-compressor includes a compressor and a turbine, and is in fluid communication with a water input flow and with the closed pressurized coolant flow. A coolant flow control valve controls the closed pressurized coolant flow. The system also includes an exhaust valve and is configured to provide a cold water flow for a first position of the coolant flow control valve and of the exhaust valve and to provide a hot water flow for a second position of the coolant flow control valve and of the exhaust valve.

According to some aspects, the gas turbine engine is a micro-turbine engine.

According to some aspects, the pressure booster is powered by a thermal exhaust power provided by the gas turbine engine.

According to some aspects, the pressure booster is powered by a portion of a compressor flow in the turbo-compressor.

According to some aspects, the pressure booster further includes a pressurized fuel tank.

According to some aspects, the turbo-compressor further includes a mechanical drive or an electric motor.

According to some aspects, the electric motor is powered by electrical power provided by the turbine engine.

According to some aspects, the gas turbine engine is fueled by natural gas.

According to some aspects, the closed pressurized coolant flow includes carbon dioxide gas.

According to some aspects, the system operates at temperatures as low as -<NUM> degrees Celsius, without icing.

According to some aspects, the system of claim <NUM> further includes a water tank.

According to some aspects, the system includes a recuperator heat exchanger.

According to some aspects, the pressure booster is powered by an exhaust gas flow of the recuperator heat exchanger.

According to some aspects, the system further includes a compact water cooler.

According to some aspects, an energy efficiency of the system, when configured to provide a cold water flow, is characterized by a coefficient of performance whose value exceeds <NUM>.

Some embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention.

Attention is now directed to the drawings, where like reference numerals or characters indicate corresponding or like components. In the drawings:.

<FIG> shows an exemplary cycle flow diagram for a cooling and boosting CCHP gas turbine system <NUM>, configured to provide a hot water output flow <NUM>, according to an embodiment of the invention. System <NUM> includes a rotating turbo-compressor <NUM> which includes a turbine <NUM> connected by a shaft to a compressor <NUM>. The turbo-compressor <NUM> is driven either by a mechanical drive <NUM> or by an electric motor <NUM>. In some embodiments, a portion of the electrical power <NUM> which is provided by the gas turbine engine <NUM> may be used to energize the electric motor <NUM>.

Pressure booster <NUM> pressurizes a fuel, such as natural gas (NG), for use by the gas turbine engine <NUM>. The fuel pressure is typically less than <NUM> bar in an external low-pressure fuel supply (not shown) which is connected to fuel inlet <NUM>; whereas the fuel pressure is greater than, for example, <NUM> bar in fuel outlet <NUM>. The increase in pressure is provided by a reciprocating piston <NUM> and spring <NUM>, driven by a pressurized coolant, such as carbon dioxide (CO<NUM>) gas. Pressurized fuel tank <NUM> feeds fuel to a combustor (not shown) of the gas turbine engine <NUM>. For embodiments in which the engine <NUM> is a micro-turbine engine, the fuel mass flow rate into the combustor is typically less than or equal to <NUM> grams/sec.

A coolant, such as CO<NUM> gas, which is provided by an external coolant source (not shown), flows through coolant inlet <NUM> into coolant chamber <NUM> and exits the chamber through coolant outlet <NUM>. A closed pressurized coolant flow passes from the coolant outlet <NUM> through flow control valve <NUM> and into the compressor <NUM>.

In <FIG>, the system <NUM> is configured to heat the water input flow <NUM>. The flow control valve <NUM> is in a closed position, and the exhaust valve <NUM> is in an open position. This enables a recuperator heat exchanger (HX) <NUM> to use a portion of the thermal exhaust power <NUM> provided by the gas turbine engine <NUM> to raise the inlet gas temperature to the turbine <NUM>. A portion of the resulting increase in turbine expansion energy is used by the flow in compressor <NUM> to drive the pressure booster <NUM>.

The recuperator exhaust gas <NUM> may be used, in some embodiments, to drive the turbo-compressor <NUM>, thereby saving the energy that would otherwise be expended by mechanical drive <NUM> or electric motor <NUM>. Alternatively, the recuperator exhaust gas may be used to provide another source of output power.

In an exemplary implementation, the values for the pressure ratio, temperature T in degrees Kelvin (°K), and temperature increments ΔT in °K at the five stations indicated in <FIG> by the encircled numbers <NUM> through <NUM>, are shown in TABLE <NUM> below.

For a CO<NUM> flow rate of <NUM>/sec and a pressure booster power of up to <NUM> kW, the fuel outlet pressure is <NUM> bar, and the gas turbine engine <NUM> may be configured to generate a thermal exhaust power <NUM> equal to <NUM> kilowatts (kW) and an electric power <NUM> equal to <NUM> kW.

<FIG> shows an exemplary cycle flow diagram for a cooling and boosting CCHP gas turbine system <NUM>, configured to provide a cold water output flow <NUM>', according to an embodiment of the invention.

When the system is configured for cooling, the flow control valve <NUM> is in an open position, and the exhaust valve <NUM> is in a closed position. This enables an ambient air flow <NUM> to reach a compact water cooler <NUM>', and also enables the thermal exhaust power <NUM> of the gas turbine engine to be redirected to external users requiring heat. Air is cooled at the outlet of compressor <NUM> by the cooler <NUM>'and/or an air fan, as shown in <FIG>. In an exemplary implementation, the resulting temperature at the inlet of turbine <NUM>, located at station number <NUM>, is approximately <NUM> °K. The temperature at the outlet of turbine <NUM>, located at station number <NUM>, is approximately <NUM> °K, and water flows into the water tank <NUM>, thereby warming the fan air flow <NUM>' and cooling the water inside the cooler <NUM>'. The fan air flow <NUM>' reaches a temperature of about <NUM> °K at the cooler exit, and is then redirected to the compressor inlet, located at station number <NUM>.

In <FIG>, the closed pressurized coolant flow is statically pressurized to, for example, <NUM> bars. When circulated, the coolant pressure is increased to <NUM> bars, which is sufficient to activate the piston <NUM> of the pressure booster <NUM>. The circulation of the coolant flow is powered either by the electric motor <NUM>, by the turbine <NUM>, or by the mechanical drive <NUM>.

In an exemplary implementation, the values for the pressure ratio, temperature, and temperature increments at the stations in <FIG> are shown in TABLE <NUM> below.

For a CO<NUM> mass flow rate (M) equal to <NUM>/sec and a CO<NUM> specific heat (Cp) equal to <NUM> Joule/(kg-°C),<MAT><MAT> The corresponding coefficient of performance (COP) is equal to (<NUM>/<NUM>)=<NUM>. This is significantly higher than the COP's achieved in typical aerospace turbo-compressor cooling systems and in absorption systems, which typically have COP's of about <NUM> and <NUM>, respectively.

The cooling and boosting CCHP gas turbine system of the invention provides several additional advantages over existing CCHP turbine systems. For example, the invention avoids a need to use hot pressurized bleed air from the compressor of the gas turbine engine <NUM>, as is commonly used in prior-art aerospace cooling systems. This avoids contamination of the air with oil or fuel residuals as well as the need to cool hot exhaust gases.

Furthermore, when CO<NUM> is used as the pressurized coolant, the system of the present invention can operate at temperatures as low as -<NUM> (<NUM>), without the icing difficulties that plague existing open air systems.

In addition, the pressure booster <NUM> of the present invention may increase fuel pressure using energy drawn from the recuperator exhaust gas, and thus avoid the need for an external source of power.

Claim 1:
A boosting gas turbine system (<NUM>) for providing combined cooling, heating, and electrical power (CCHP), comprising:
a pressure booster (<NUM>) in fluid communication with a gas turbine engine, and comprising a fuel inlet, a fuel outlet, and a piston;
the pressure booster further comprising a coolant inlet (<NUM>), a coolant chamber (<NUM>), and
a coolant outlet (<NUM>), and in fluid communication with a closed pressurized coolant flow;
a turbo-compressor (<NUM>) comprising a compressor and a turbine, and in fluid communication with the closed pressurized coolant flow;
a coolant flow control valve (<NUM>) controlling the closed pressurized coolant flow;
and an exhaust valve (<NUM>);
characterized in that the system is configured to provide a cold water flow for a first position of the coolant flow control valve and of the exhaust valve and to provide a hot water flow for a second position of the coolant flow control valve and of the exhaust valve.