Patent Application
20170298866
The object of this patent application relates to the methods and apparatus for combined heat and power systems waste heat recovery (i.e. cogeneration power plants) wherein incorporated water source high temperature heat pump utilizes at least one waste heat source of cogeneration unit.
Heat pumps that have been used in prior art to enhance the heating power of combined heat and power systems by utilizing the waste heat recovery have been deployed in a number of designs. According to US2006037349 a waste heat is used to improve the heating performance of a heat pump type air conditioner or to prevent an outdoor heat exchanger of the heat pump type air conditioner from being frosted. Yet another solution as disclosed in EP2299098 incorporates an air source type heat pump for utilizing the waste heat source of cogeneration unit, wherein similarly to the one stated before, the main disadvantage of represented approach is relatively low thermal coefficient of performance compared to the water source heat pump potential.
This invention relates to the combined heat and power systems, wherein at least one incorporated water source high temperature heat pump is used to upgrade a low temperature heat from at least one waste heat source to the higher temperature heat output, which can be afterwards used by at least one heat consumer for space or process heating, preferably in the scope of district heating. It is important to notice, that the heat pump according to the invention is used to heat up and rise the temperature of a heat transfer medium in a return line of a heat distribution network, wherein a design (i.e. operational) temperature of the heat transfer medium in a forward line of the heat distribution network is substantially higher than 60° C., when operating at normal operating conditions. It can be understood, that operating conditions of the heat distribution network are provided after commissioning and warm-up process where at least basic design temperature of the heat distribution network is successfully achieved and maintained (i.e. established) over at least a short period of time, hence at least one internal combustion engine is turned on and operating by firing the fuel in the combustion process in continuous operation and at least one heat pump is turned on and operating for liquid-vapor phase change thermodynamic cycle process (i.e. heat pump principle) and waste heat source utilization. In accordance, at least one internal combustion engine and at least one heat pump are used to provide a first and second heat source respectively in the scope of heat distribution network where individual unit shall substantially operate in the range between its minimum and maximum rated (i.e. full load) operating power, preferably at normal rated power for highest power developed in continuous operation.
Exemplary embodiment of the present invention will now be described with reference to the accompanying drawing, i.e. schematics of a cogeneration power plant with incorporated water source high temperature heat pump in a heat distribution network (i.e. preferably at least one closed loop circuit heating system).
Referring to the preferential embodiment of the cogeneration unit (CHP) with incorporated water source high temperature heat pump (HP), the system comprises an internal combustion engine (ICE), preferably a water cooled gas engine, which runs on a gas fuel, such as natural gas, liquefied petroleum gas, landfill gas, wood gas or biogas for example. While internal combustion engine (ICE) and generator (G) are used for electricity and heat generation when powered, a significant amount of heat is released from the cylinders within the combustion process and other subcomponents (i.e. lubrication oil, charging air and exhaust gas, hereinafter addressed as flue gas), wherein the heat is either used by heat consumer (HC) rather than dissipated to the ambient (O) through the external cooling system (CT1). It is important to notice, that the main heat source for heat consumer (HC) is preferably represented by internal combustion engine (ICE) cooling system (i.e. a jacket type heat exchanger, having an inlet and outlet aperture, herein addressed as inflow and outflow aperture) whereby plurality of waste heat sources arise in the scope of the cogeneration unit (CHP) and incorporated heat pump (HP) when the internal combustion engine (ICE) and heat pump (HP) are turned on and powered, preferably at optimum efficiency or full load regime.
Effective recovery of waste heat is critical to provide a good total utilization of fuel energy, thus, first and most important waste heat source is represented by flue gas in exhaust system, which is a product of the combustion process within the internal combustion engine (ICE). Secondly, there are at least two additional waste heat sources represented by lubrication oil cooling systems, the first one represented by internal combustion engine (ICE) lubrication oil cooling system and a second one represented by the heat pump (HP) lubrication oil cooling system (i.e. incorporated compressors lubrication oil cooling system). Furthermore, there are few minor waste heat sources, as internal combustion engine (ICE) charging air cooling system for example, which are under certain circumstances still important for good total waste heat source utilization.
According to the depicted preferential embodiment as represented on
As partially known from prior art, the waste heat of flue gas is utilized by incorporated heat exchanger (HE1) which collects the high temperature waste heat of flue gas in exhaust system, wherein the exhaust heat exchanger (HE1) is capable to collect the waste heat due to the significant temperature difference between the flue gas in exhaust system and primary heat transfer medium in incorporated heat exchanger (HE1). Furthermore, exhaust system according to the invention preferably comprises at least one additional condensing heat exchanger (HE2), which is incorporated to collect at least the residual low temperature waste heat of flue gas, being used afterwards by water source high temperature heat pump (HP) to enhance the heating power of the cogeneration unit (CHP). More precisely, the depicted embodiment comprises two heat exchangers (HE1, HE2) incorporated into the internal combustion engine (ICE) exhaust system with aim to collect the waste heat of combustion process, wherein it is important to notice, that the first heat exchanger (HE1) is operably coupled to the forward line of heat distribution circuit, wherein the flow of primary heat transfer medium through the heat exchanger (HE1) cools down the temperature of flue gas to approximately 120° C.; and furthermore, the second (i.e. preferably condensing) heat exchanger (HE2) is operably coupled with a high temperature heat pump (HP) evaporator unit, preferably in a closed loop piping system with secondary heat transfer medium involved, hence the temperature of the flue gas in exhaust system is additionally reduced to the temperature close to the ambient (O), preferably bellow 25° C. While the temperature of flue gas in exhaust system is rapidly reduced, the exhaust system may further comprise a suction fan (F1) for removal of flue gas from exhaust system, if necessary.
If appropriate, the heating power of represented cogeneration unit (CHP) can be furthermore enhanced if the first heat exchanger (HE1) is partially or completely bypassed by means of flue gas stream manipulation (i.e. regulation) means comprising motorized valves, preferably hatches (H1-H4), regulated by said control unit. It can be understood, that the utilization of flue gas waste heat source is maximized by high temperature heat pump (HP), if the first heat exchanger (HE1) is completely bypassed and hence the stream of the high temperature flue gas is fully enforced through the condensing heat exchanger (HE2), which collects the waste heat required for heat pump (HP) principle utilization. Even more, if appropriate, the heat exchanger (HE2) and heat pump (HP) shall be implemented in a multistage approach or cascade principle comprising a plurality of heat pumps (HP) and/or heat exchangers (HE2) in parallel and/or serial connection, to reach the simplified and cost effective solution for exhaust system as well. As follows, similarly as described for flue gas waste heat utilization, the waste heat of internal combustion engine charging air or lubrication oil cooling system can be collected as well by at least one additional heat exchanger (HE3), which is operably coupled to the heat pump (HP) evaporator unit in serial or parallel connection with above described heat exchanger (HE2) in exhaust system, wherein the lubrication oil cooling system of heat pump (HP) compressor is preferably incorporated into the water source high temperature heat pump (HP) enclosure.
While there are several options for waste heat source utilization it is essential to notice, that preferential embodiment of water source high temperature heat pump (HP) utilization uses at least one low temperature waste heat source for vaporization of working medium of incorporated heat pump (HP), wherein the condenser unit outlet is preferably fed to the heat distribution circuit return line, more precisely to the inflow of the internal combustion engine (ICE) cooling system, where the aim of proposed inventive approach is to reach and maintain the maximum allowed temperature of the primary heat transfer medium at the inlet of the engine cooling system. According to depicted embodiment on
Furthermore, the invention relates to a method of the heat pump (HP) integration process, to a method for utilization of low grade temperature waste heat sources of cogeneration unit (CHP) by water source high temperature heat pump (HP) and to a method of using the apparatus according to the invention.
The following steps represent the key features of a heat pump (HP) integration and novel method for cogeneration unit (CHP) waste heat source utilization:
The following steps represent the key features of a method of using the apparatus according to the invention:
In addition to represented method of using the apparatus according to the invention, few explanations and definitions are required, wherein combustion process is substantially a continuous process, while said internal combustion engine (ICE) normally operates in the range between its minimum and maximum rated operating power, preferably at normal rated power in continuous operation. Similarly the liquid-vapor phase change thermodynamic cycle utilization process is substantially a continuous process, wherein said heat pump (HP) operates in the range between its minimum and maximum rated operating power, preferably at normal rated power in continuous operation. If appropriate, the fuel combustion process in complex (i.e. advanced) heat and power generation plant shall be provided by plurality of internal combustion engine (ICE) units, wherein the heat in the scope of the first heat releasing unit is transferred in serial and/or in parallel connection with aim to transfer the heat between individual engine cooling systems and similarly, the liquid-vapor phase change thermodynamic cycle utilization process shall be utilized by plurality of heat pump (HP) units to provide a second heat releasing unit of the advanced heat and power generation plant.
While one of the key features of method and apparatus according to the invention is establishment of predetermined set point value for internal combustion engine coolant temperature, the thermal energy balance adjustment is executed by adapting the power of said heat pump (HP) and/or by adapting the power of said internal combustion engine (ICE) and/or by adapting the mass flow of the primary heat transfer medium through the engine cooling system of said internal combustion engine and/or by adapting the mass flow of the primary heat transfer medium through the heat pump (HP) and/or by adapting the mass flow of the secondary heat transfer medium in at least one of said closed loop circuit for waste heat source utilization. Accordingly the mass flow of the primary heat transfer medium in said heat distribution circuit is adapted by changing the flow velocity in said heat distribution circuit and/or the mass flow of the secondary heat transfer medium in said closed loop circuit is adapted by changing the flow velocity in said closed loop circuit, wherein the velocity of heat transfer medium in heat distribution network is adapted by switching (i.e. on/off regulation) and/or by adjusting the power of at least one circulation pump for mass flow adjustment. In addition, the mass flow of the primary heat transfer medium in said heat distribution circuit is alternatively adapted by stream flow regulation, wherein at least a portion of the primary heat transfer medium stream in the return line of said heat distribution circuit is redirected to the return line of said heat distribution circuit to provide a heat pump (HP) bypass connection, and/or wherein at least a portion of the primary heat transfer medium stream from said heat pump (HP) is redirected to a forward line of the heat distribution circuit to provide an engine cooling system bypass connection. Similarly the mass flow of the secondary heat transfer medium in said closed loop circuit for waste heat source utilization is adapted by stream flow regulation, wherein at least a portion of the secondary heat transfer medium stream is redirected in said closed loop circuit to provide a bypass connection for at least one waste heat recovery unit. Accordingly, the mass flow regulation of the primary heat transfer medium and/or the mass flow regulation of the secondary heat transfer medium for thermal energy balance adjustment is determined, controlled and executed by at least one control unit (i.e. electronic controller), wherein the position and/or the state (i.e. open/closed or on/off regulation) of the automated regulation means is adjusted in respect to the heat demand in said heat distribution network.
Apparatus according to the invention further comprises at least one control unit, wherein such a controller shall be autonomous device for thermal management regulation or alternatively, at least basic functions of the thermal management controller for determination process, comparison process and execution process could be incorporated and implemented to the internal combustion engine (ICE) controller or in to the heat pump (HP) controller as well. In the determination process the environment and thermal conditions of heat distribution network is determined by the group of thermal, pressure or other sensors, wherein at least one input from at least one sensor of heat distribution network or internal combustion engine (ICE) is used for comparison process, where at least one value of at least one input parameter (i.e. preferably a temperature of the primary heat transfer medium in engine cooling system) is analyzed and compared to the limiting values, preferably being pre-defined and stored in the control unit. Accordingly the execution process comprises a process of executing instructions stored in control unit to generate appropriate output signal, where at least one parameter for thermal energy balance adjustment is generated, executed and performed by control electronics in cooperation with automated regulation means in order to reach and maintain the threshold set-point value, wherein said threshold value is defined between the maximum value and the minimum value for set point equal value with aim to provide a hysteresis for thermal energy balance adjustment.
It can be understood that control unit (i.e. electronic module) may communicate with various output devices where the temperature of the heat transfer medium in the heat transfer network is determined, controlled and regulated by a group of automated regulation means comprising motorized valves, pumps and sensors, wherein regulation means are preferably adapted to be manipulated by at least one control unit. And furthermore, the heat distribution process in heat distribution network is provided by at least one heat transfer medium, preferably by plurality of heat distribution mediums. Accordingly the heat in said heat transfer network is transferred from first heat releasing unit to the heat consumer (HC) by circulation of the primary heat transfer medium in at least one closed loop circuit, and similarly the heat from waste heat recovery unit is transferred to the heat pump (HP) by circulation of the secondary heat transfer medium in at least one closed loop circuit, wherein the heat upgraded by at least one heat pump (HP) is furthermore transferred from heat pump (HP) condenser unit to the engine cooling system of at least one internal combustion engine (ICE) by said primary heat transfer medium.
Summarizing, the cooling circuits of cogeneration unit (CHP), herein represented as low temperature waste heat sources, are used for utilization of water source high temperature heat pump (HP), wherein its hot water output is preferably used for establishing and maintaining the highest possible or maximum allowed temperature of primary heat transfer medium for internal combustion engine (ICE) cooling system inflow (i.e. cooling jacket inlet). It can be understood, that all vital components of heat distribution circuit are preferably operably coupled for heat transfer medium circulation, wherein the compressor of the incorporated heat pump (HP) shall be driven by electric machine, powered by electricity from grid or generator (G), or alternatively if appropriate, a high temperature heat pumps (HP) compressor shall be mechanically coupled to and driven by internal combustion engine (ICE) as well. Furthermore, as can be clearly read out from previous description, the primary heat transfer medium in preferential embodiment is water and similarly, the secondary heat transfer medium in preferential embodiment is mix of water and glycol.
In the foregoing description those skilled in the art will readily appreciate that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims expressly state otherwise.
| Number | Date | Country | Kind |
|---|---|---|---|
| P-201400339 | Oct 2014 | SI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2015/001617 | 9/14/2015 | WO | 00 |
