TW201522766A - Organic rankine cycle system and operation mode changing mathod for sub-critical cycle and transcritical cycle - Google Patents

Abstract

An organic Rankine cycle system which can be operated in subcritical ORC mode and transcritical mode and an operation mode changing method for sub-critical cycle and trans-critical cycle of the organic Rankine cycle system includes judging if the real pressure value of working fluid before passing an expander is equal to the critical pressure value or bigger than the critical pressure value. If yes, the organic Rankine cycle system works as a trans-critical cycle operation mode. If no, the organic Rankine cycle system works as a sub-critical cycle operation mode.

Description

Organic Rankine cycle system and its subcritical operation mode and switching mode of wearing critical operation mode

This proposal relates to an organic Rankine cycle system, in particular an organic Rankine cycle system and its switching method of subcritical operation mode and through critical operation mode.

The Organic Rankine Cycle (ORC) uses a low-boiling organic substance at normal pressure as the working fluid, which is the most efficient and economical in the current medium-low temperature thermal power generation technology. The organic Rankine cycle is operated at or above the critical point depending on the internal circulation working fluid to be classified as a Sub-critical cycle system or a Transcritical cycle system. In general, the critical circulation system has a higher system thermal efficiency and a heat source heat extraction rate, so that the power generation amount is larger under the same cold and heat source conditions.

The heat source used in the critical organic Rankine cycle system is diversified and wide-ranging, including variable heat sources such as medium and low temperature waste heat, geothermal heat, hot springs, and solar thermal energy. However, since the temperature of the variable heat source and the supply amount per unit time have periodic, intermittent or irregular variations, if the critical organic Rankine cycle faces the above-mentioned variable heat source, it may be due to the heat source. The conditions change to the conditions under which the critical organic Rankine cycle operates, resulting in the shutdown of the organic Rankine cycle system, which in turn limits the use of the organic Rankine cycle system. As a result, the cumulative power generation of the organic Rankine cycle system will be reduced, so how to improve the organic Rankine cycle system The amount of power generated by a variable heat source, and thus its economic benefits, will be one of the problems that R&D personnel should solve.

The proposal is to provide an organic Rankine cycle system and a method for switching between its subcritical operation mode and the through critical operation mode, thereby improving the operable range of the organic Rankine cycle system in the face of a variable heat source.

The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system disclosed in the proposal includes the following steps: determining an actual pressure value before the working fluid of one of the organic Rankine cycle systems enters the inlet of an expander Whether it is greater than or equal to one of the critical pressure values of the working fluid: if so, the organic Rankine cycle system is operated in a critical operating mode. If not, the organic Rankine cycle system is operated in a critical operating mode.

The organic Rankine cycle system operable in the subcritical and breakthrough critical state disclosed in the proposal comprises a heat source heat exchanger, an expander, a condenser, a pump, a pressure sensor and a control element. The expander is connected to the heat source heat exchanger by a pipe. The condenser is connected to the expander by a pipe. The pump is connected to the condenser and the heat source heat exchanger by a line. The pump is used to drive a working fluid, and the pump sequentially flows through the heat source heat exchanger, the expander and the condenser to form an organic Rankine cycle. The working fluid has a critical pressure value. The pressure sensor is used to detect the actual pressure value of the working fluid at the inlet of the expander. The control element is used to determine the relationship between the actual pressure value of the working fluid and the critical pressure value. If the actual pressure value of the working fluid is greater than the critical pressure value, the control element controls the organic Rankine cycle to operate in a critical operating mode. If the actual pressure value of the working fluid is less than the critical pressure value, the control element controls the organic Rankine cycle to operate in a critical operating mode.

According to the organic Rankine cycle system disclosed in the above proposal, and the switching method of the subcritical operation mode and the critical critical operation mode, the operation mode of the organic Rankine cycle system is switched by the pressure condition, so that when the condition of the working fluid changes, the organic The Rankine cycle system can be continuously adjusted to the appropriate mode of operation in order to increase the operational range and utilization of the organic Rankine cycle system and increase its cumulative power generation, thereby increasing the economics of the organic Rankine cycle system.

The above description of the contents of this proposal and the description of the following embodiments are used to demonstrate and explain the principles of this proposal, and to provide a further explanation of the scope of the patent application of this proposal.

10‧‧‧Organic Rankine Cycle System

100‧‧‧heat source heat exchanger

200‧‧‧expander

300‧‧‧Condenser

400‧‧‧ pump

510‧‧‧ Pressure Sensor

520‧‧‧temperature sensor

600‧‧‧ generator

700‧‧‧Control elements

1 is a schematic diagram of a system of an organic Rankine cycle system in accordance with an embodiment of the present proposal.

Figure 2 is a schematic diagram of the temperature-entropy performance of the organic Rankine cycle system of Figure 1 in the critical operating mode.

Figure 3 is a schematic diagram of the temperature-entropy performance of the organic Rankine cycle system of Figure 1 in the subcritical mode of operation.

Fig. 4 is a flow chart showing a method of switching the subcritical operation mode and the through critical operation mode of the organic Rankine cycle system of Fig. 1.

Fig. 5 is a flow chart showing the operation of the organic Rankine cycle system of Fig. 1 in the critical operation mode.

Fig. 6 and Fig. 7 are schematic diagrams showing the temperature-entropy performance of the heat source temperature variation of the organic Rankine cycle system of Fig. 1.

Figure 8 is a flow chart showing the operation of the organic Rankine cycle system of Fig. 1 in the subcritical operation mode.

Please refer to Figures 1 to 3. Figure 1 is a diagram of an embodiment of the present proposal A schematic diagram of the system of the organic Rankine cycle system. Figure 2 is a schematic diagram of the temperature-entropy performance of the organic Rankine cycle system of Figure 1 in the critical operating mode. Figure 3 is a schematic diagram of the temperature-entropy performance of the organic Rankine cycle system of Figure 1 in the subcritical mode of operation.

As shown in FIG. 1, the embodiment can operate in a subcritical and critical state. The organic Rankine cycle system 10 includes a heat source heat exchanger 100, an expander 200, a condenser 300, a pump 400, a pressure sensor 510, a temperature sensor 520, a generator 600, and a Control element 700.

The heat source heat exchanger 100 is used to supply an external heat source. Heat source and organic The Ken Circulatory System 10 performs heat exchange to provide thermal energy to the organic Rankine cycle system 10. The heat source is, for example, medium and low temperature waste heat, geothermal heat, hot spring, solar heat, and the like. The expander 200 is used to release fluid pressure. The condenser 300 is used to supply an external cold source, and the cold source exchanges heat with the organic Rankine cycle system 10 to carry away the thermal energy of the organic Rankine cycle system 10. The cold source is, for example, a water-cooled cooling tower, an air-cooled cooler, river water, sea water, or other cryogenic fluid. The pump 400 is used to drive the working fluid flow of the organic Rankine cycle system 10 and to adjust the working fluid pressure.

The heat source heat exchanger 100, the expander 200, the condenser 300, and the pump 400 are connected to each other by a pipeline, and the pump 400 is used to drive a working fluid to sequentially flow from the pump 400 to the heat source heat exchanger 100, and expand. The machine 200 and the condenser 300 form an organic Rankine cycle to convert thermal energy into mechanical energy. The working fluid has a critical pressure value P _C (as shown in Figures 2 and 3). If the actual pressure value before the working fluid flows into the heat exchanger heat exchanger 100 and before entering the inlet of the expander 200 is greater than the critical pressure value P _C , then the representative working fluid has only a single phase at a single point in time. If the actual pressure value before the working fluid flows into the heat exchanger heat exchanger 100 and before entering the inlet of the expander 200 is lower than the critical pressure value P _C , it means that the working fluid has more than two phases at a single point in time. The working fluid is an organic refrigerant. In this embodiment, the R-134a organic refrigerant is taken as an example, but not limited thereto. The organic refrigerant may also be selected from the group consisting of HFCs (eg, R134a, R245fa, R32, R23, R41, R125, R152a, R236fa, etc.). Mixed refrigerant (such as: R404A, R407C, R507A, R410A, etc.), HCs (such as: R116, R218, RC318, n-pentane, etc.), FCs (such as: butane, isobutene, propane, methane, etc.) one of them. In addition, the pump 400 is a variable flow pump or a constant flow pump with a variable frequency motor. The expander 200 is a turbine, a screw expander 200, a scroll expander 200, a positive displacement expander 200, a reciprocating expander 200, and the like.

In the present embodiment, the pump 100 is a constant flow pump. Control element 700 transmits An inverter device 800 changes the output frequency value or the output flow value of the pump 100. However, the variable frequency device 800 is not an essential component. In the embodiment where the variable flow pump is selected in the pump 100, the frequency conversion device 800 need not be provided.

The pressure sensor 510 is configured to detect an actual pressure value P _r after the working fluid flows into the heat source heat exchanger 100 and enters the inlet of the expander 200.

The temperature sensor 520 is configured to detect an actual temperature value T _r before the working fluid flows into the heat source heat exchanger 100 and enters the inlet of the expander 200.

Generator 600 is coupled to expander 200. The expander 200 is used to drive the generator 600 to operate to convert mechanical energy into electrical energy.

A control element 700 for determining the actual value of the pressure of the working fluid and the critical pressure P _r of the relationship between P _C, if the actual value of the pressure of the working fluid pressure P _r is greater than the threshold value P _C, then the control element 700 controls the Organic Rankine Cycle The system 10 operates in a critical operating mode (the temperature-entropy performance of the organic Rankine cycle system 10 in the critical operating mode is as shown in Figure 2). If the actual pressure value P _{r of the} working fluid is less than the critical pressure value P _C , the control element 700 controls the organic Rankine cycle system 10 to operate in a critical operating mode (temperature-entropy of the organic Rankine cycle system 10 in the subcritical operating mode) The performance diagram is as shown in Figure 3.

The organic Rankine cycle system 10 can be based on heat source history data and The temperature/flow variation condition and the operating parameters of the organic Rankine cycle system 10 determine the operating temperature range corresponding to each pressure value of the organic Rankine cycle system 10 when operating in the critical operating mode and preset during the subcritical operating mode operation. a suitable range of superheat, and recording the above information in a supercritical working fluid pressure temperature database of the control element 700 and a superheat calculation module to enable the control element 700 to pass the supercritical working fluid pressure temperature database and The superheat calculation module automatically adjusts the output frequency value or the output flow value of the pump 400.

The supercritical working fluid pressure temperature database has multiple sets of pressure and working temperature range data of the organic Rankine cycle system 10 in the subcritical operating mode, and each set of pressure and working temperature range data has a pressure value and a corresponding work. temperature range.

Please refer to Figures 4 to 5. Fig. 4 is a flow chart showing a method of switching the subcritical operation mode and the through critical operation mode of the organic Rankine cycle system of Fig. 1. Fig. 5 is a flow chart showing the operation of the organic Rankine cycle system of Fig. 1 in the critical operation mode.

As shown in Figure 4. First, the control element 700 determines whether the actual pressure value P _r before the working fluid of the organic Rankine cycle system 10 passes through the heat source heat exchanger 100 and enters the inlet of the expander 200 is greater than or equal to a critical pressure value P _{C of the} working fluid (as in the steps). S100)).

If so, the control element 700 will cause the organic Rankine cycle system 10 to operate in a critical operating mode (as shown in step S200).

If not, the control element 700 will cause the organic Rankine cycle system 10 to The boundary operation mode operates (as shown in step S300).

As shown in FIG. 5, in the operation mode of the critical operation mode, first, the control component 700 searches a supercritical working fluid pressure temperature database to obtain an operating temperature range corresponding to the actual pressure value P _r (step S210). Shown).

Next, the control element 700 determines the relationship between an actual temperature value T _r before the working fluid passes through the heat source heat exchanger 100 and enters the inlet of the expander 200 and the operating temperature range TR (as shown in step S220).

If the temperature sensor 520 measures that the actual temperature value T _r of the working fluid before entering the inlet of the expander 200 is lower than the lower limit T _{R,MIN of the} operating temperature range, the control element 700 lowers the output frequency of the pump 400. Value or output flow value (as shown in step S230). If the pressure sensor 510 determines that the actual pressure value P _r of the working fluid before the inlet of the expander 200 is lower than the critical pressure value P _C , the control element 700 causes the operation mode of the organic Rankine cycle system 10 to be operated by the critical stroke. The mode is switched to the sub-critical operation mode (as shown in step S260) to enable the organic Rankine cycle system 10 to continue to generate electricity to increase the cumulative power generation.

If the temperature sensor 520 measures the working fluid before entering the inlet of the expander 200 When the actual temperature value Tr falls within the operating temperature range, the output frequency value or the output flow value of the pump 400 that drives the working fluid is maintained (as shown in step S240).

If the temperature sensor 520 measures that the actual temperature value T _r of the working fluid before entering the inlet of the expander 200 is higher than the upper limit T _{R, MAX of the} operating temperature range, the control element 700 raises the output frequency of the pump 400. Value or output flow value (as shown in step S250). If the pressure sensor 510 determines that the actual pressure value P _r of the working fluid before entering the inlet of the expander 200 is higher than the allowable maximum pressure value P _{A,MAX of the} organic Rankine cycle system 10, then the control element 700 will cause the organic component The Ken Circulatory System 10 is deactivated (as shown in step S270) to avoid damage to the organic Rankine cycle system 10.

The following is an example of the operation of the organic Rankine cycle system 10 in the critical mode. situation. Please refer to Figure 6 and Figure 7. Fig. 6 and Fig. 7 are schematic diagrams showing the temperature-entropy performance of the heat source temperature variation of the organic Rankine cycle system of Fig. 1.

It is assumed that the organic Rankine cycle system 10 operates stably in the critical operation mode under a stable heat source (temperature Ts1, flow rate Ms1) and cold source conditions. Before entering the expander 200, the working fluid has a pressure, temperature and mass flow rate of the first pressure value P1, the first temperature value T1 and the first mass flow rate M1 (with the output frequency value or output of the pump 400). The flow value is proportional to). When the cold source is fixed, the heat source flow rate is fixed, but the temperature is increased, the first temperature value T1 of the heat exchanged working fluid is raised to the first transient temperature value T1-1. At this time, the control element 700 can gradually increase the output frequency value or the output flow value of the pump 400, thereby increasing the pressure of the working fluid from the first pressure value P1 to the second pressure value P2 (the mass flow rate of the working fluid is also Corresponding from the first mass flow rate M2 to the second mass flow rate M2). Since the working fluid mass flow rate is increased (M2>M1) and the external heat source is limited, the temperature of the working fluid before entering the inlet of the expander 200 is lowered from the first transient temperature value T1-1 to the second temperature value T2. At this time, the control component 700 determines whether the second temperature value T2 falls within the operating temperature range of the second pressure value P2, and if not, continues to modulate the output frequency value or the output flow value of the pump 400 until the operation The temperature of the fluid falls within the operating temperature range. Furthermore, assuming that the second pressure value P2 of the adjusted working fluid is higher than the system allowable maximum operating pressure value P _A,MAX , the control element 700 will cause the organic Rankine cycle system 10 to shut down.

It is assumed that the organic Rankine cycle system 10 operates stably in the critical operation mode under a stable heat source (temperature Ts1, flow rate Ms1) and cold source conditions. Before entering the expander 200, the working fluid has a pressure, temperature and mass flow rate of the first pressure value P1, the first temperature value T1 and the first mass flow rate M1 (with the output frequency value or output of the pump 400). The flow value is proportional to). When the cold source is fixed, the heat source flow rate is fixed, but the temperature is lowered, the first temperature value T1 of the working fluid after the heat exchange is lowered to the second transient temperature value T1-2. At this time, the control element 700 can gradually reduce the output frequency value or the output flow value of the pump 400, thereby reducing the pressure of the working fluid from the first pressure value P1 to the third pressure value P3 (the mass flow rate of the working fluid is also Corresponding from the first mass flow rate M2 to the third mass flow rate M3). Since the working fluid mass flow rate is reduced (M3 < M1) and the external heat source is limited, the temperature of the working fluid before entering the inlet of the expander 200 is raised from the second transient temperature value T1-2 to the third temperature value T3. At this time, the control component 700 determines whether the second temperature value T2 falls within the operating temperature range of the second pressure value P2, and if not, continues to modulate the output frequency value or the output flow value of the pump 400 until the operation The temperature of the fluid falls within the operating temperature range. In addition, if the third pressure value P3 of the adjusted working fluid is lower than the critical pressure value P _{C of the} working fluid, the control element 700 will switch the operation mode of the organic Rankine cycle system 10 from the critical operation mode to the subcritical operation. mode. Assuming that the adjusted third working pressure value P3 of the working fluid is lower than the system allowable minimum operating pressure value P _A,MIN , the control element 700 will cause the organic Rankine cycle system 10 to shut down.

Further, if the heat source temperature is fixed and the flow rate is changed, the operation procedure of the organic Rankine cycle system 10 is also the same as described above, and therefore will not be described again.

In the above, the method for the control element 700 to modulate the output frequency value or the output flow value of the pump 400 can be set by the PID control.

Please refer to Figure 8. Figure 8 is a flow chart showing the operation of the organic Rankine cycle system of Fig. 1 in the subcritical operation mode.

As shown in FIG. 8, the operation mode of the subcritical operation mode, firstly, the superheat calculation module of the control element 700 is calculated according to the actual pressure value P _r and the actual temperature value T _r before the working fluid enters the inlet of the expander 200. An actual superheat value OS _{r is output} (as shown in step S310).

Next, the control element 700 determines the relationship between the actual superheat value OSr of the working fluid before entering the inlet of the expander 200 and a predetermined superheat range OS _R (as shown in step S320).

If the temperature sensor 520 measures that the actual superheat value OS _r of the working fluid before entering the inlet of the expander 200 is less than the lower limit of the preset superheat range OS _{R, MIN} , the control element 700 will lower the pump 400 The frequency value or the output flow value is output (as shown in step S330). If the pressure sensor 510 determines that the actual pressure value P _r before entering the inlet of the expander 200 is lower than the allowable minimum pressure value P _{A,MIN of the} organic Rankine cycle system 10, then the control element 700 will cause the organic Rankine cycle system 10 is stopped (as shown in step S360) to avoid damage to the organic Rankine cycle system 10.

If the temperature sensor 520 measures that the actual temperature value Tr of the working fluid before entering the inlet of the expander 200 falls within the operating temperature range T _R , an output frequency value or an output flow value of the pump 400 that drives the working fluid is maintained. (as shown in step S340).

If the temperature sensor 520 detects that the actual superheat value OS _r of the working fluid before entering the inlet of the expander 200 is greater than the upper limit OS _{R, MAX of the} preset superheat range, the control element 700 raises the pump 400. The output frequency value or the output flow value (as shown in step S350). If the pressure sensor 510 measures that the actual pressure value P _r of the working fluid before entering the inlet of the expander 200 is higher than the critical pressure value P _C , then the control element 700 causes the operating mode of the organic Rankine cycle system 10 to be sub-critical. The operation mode is switched to the critical operation mode (as shown in step S370) to obtain a better power generation efficiency.

According to the organic Rankine cycle system disclosed in the above proposal, and the switching method of the subcritical operation mode and the critical critical operation mode, in addition to the pressure conditions, the operating temperature is further The range condition and the superheat condition are used to switch the operation mode of the organic Rankine cycle system, so that when the conditions of the external cold and heat source change, the organic Rankine cycle system can be continuously adjusted to the appropriate operation mode, so as to improve the organic Rankine cycle system. The operating range and usage increase the cumulative power generation, which in turn increases the economics of the organic Rankine cycle system.

Although the embodiments of the present disclosure are as described above, and are not intended to limit the present proposal, any person skilled in the art, regardless of the spirit and scope of the proposal, may have the shapes, structures, and features described in the scope of the application of the present proposal. And the quantity can be changed slightly, so the scope of patent protection of this proposal shall be subject to the definition of the scope of patent application attached to this specification.

Claims (20)

A method for switching a subcritical operating mode and a critical critical operating mode of an organic Rankine cycle system, comprising the steps of: determining whether an actual pressure value of a working fluid of an organic Rankine cycle system before entering an expander inlet is greater than or equal to A critical pressure value of the working fluid: if so, the organic Rankine cycle system is operated in a critical operating mode; and if not, the organic Rankine cycle system is operated in a critical operating mode. The method for switching the subcritical operation mode and the critical critical operation mode of the organic Rankine cycle system according to claim 1, wherein the operation flow of the critical operation mode comprises the following steps: searching for a supercritical working fluid pressure temperature database, Obtaining an operating temperature range corresponding to the actual pressure value; and determining an actual temperature value before the working fluid enters the expander inlet and the operating temperature range: if the actual temperature value is lower than the operating temperature range a lower limit value, which is an output frequency value or an output flow rate value that drives one of the working fluids; if the actual temperature value falls within the operating temperature range, the output frequency value of the pump is maintained or The output flow value; and if the actual temperature value is above the upper limit of the operating temperature range, raising the output frequency value or the output flow value of the pump. The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system according to claim 2, wherein if the actual temperature value is lower than the lower limit of the operating temperature range a value, wherein the step of decreasing the output frequency value or the output flow value of the pump further comprises: if the actual pressure value before entering the expander inlet is lower than the critical pressure value, the organic Rankine is made The operation mode of the circulation system is switched from the critical operation mode to the sub-critical operation mode. The method for switching the subcritical operation mode and the critical critical operation mode of the organic Rankine cycle system according to claim 2, wherein in the operation flow of the critical operation mode, if the actual temperature value is higher than the operating temperature range The upper limit value, after the step of increasing the output frequency value or the output flow value of the pump, further comprises: if the actual pressure value before entering the expander inlet is higher than the allowable maximum pressure of the organic Rankine cycle system At the time of the value, the organic Rankine cycle system is stopped. The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system according to claim 2, wherein the supercritical working fluid pressure temperature database has a plurality of sets of pressures in the operating process of the critical operating mode With the operating temperature range data, each set of pressure and operating temperature range data has a pressure value and a corresponding operating temperature range. The method for switching the subcritical operation mode and the critical critical operation mode of the organic Rankine cycle system according to claim 1, wherein the operation process of the subcritical operation mode comprises the following steps: calculating the actual pressure value according to the actual temperature value An actual superheat value of the working fluid; and a relationship between the actual superheat value before the working fluid enters the expander inlet and a predetermined superheat range: if the actual superheat value is less than the preset superheat range a lower limit value, which is to decrease the output frequency value or the output flow value of the pump; Maintaining the output frequency value or the output flow value of the pump if the actual superheat value falls within the preset superheat range; and if the actual superheat value is greater than the upper limit of the preset superheat range The value increases the output frequency value or the output flow value of the pump. The method for switching the subcritical operation mode and the critical critical operation mode of the organic Rankine cycle system according to claim 6, wherein in the operation flow of the subcritical operation mode, if the actual superheat value is less than the preset superheat degree The lower limit value of the range, after the step of reducing the output frequency value or the output flow value of the pump, further comprising: the actual pressure value before entering the expander inlet is lower than the tolerance of the organic Rankine cycle system At the minimum pressure value, the organic Rankine cycle system is stopped. The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system according to claim 6, wherein if the actual superheat value is greater than the upper limit of the preset superheat range, the After the step of pumping the output frequency value or the output flow value, further comprising: if the actual pressure value before entering the expander inlet is higher than the critical pressure value, the operation mode of the organic Rankine cycle system is The subcritical operation mode is switched to the through critical operation mode. The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system according to claim 1, wherein the pump is a variable flow pump or a constant flow pump with a variable frequency motor. The method for switching the subcritical operation mode and the critical critical operation mode of the organic Rankine cycle system according to claim 1, wherein the expander is a turbine, a spiral expander, a scroll expander, a volumetric expander, or a reciprocating machine. Expander, etc. The method for switching the subcritical operating mode and the critical critical operating mode of the organic Rankine cycle system according to claim 1, wherein when the temperature or flow rate of the heat source or a cold source of the organic Rankine cycle system is supplied, In the through-critical operation mode, the organic Rankine cycle system performs a step of determining whether an actual temperature value before the working fluid enters the expander inlet falls within an operating temperature range, if the organic Rankine cycle system is In the subcritical operation mode, a step of determining whether an actual superheat value before the working fluid enters the expander inlet falls within a predetermined superheat range is performed. An organic Rankine cycle system operable in a subcritical and critical state, comprising: a heat source heat exchanger; an expander connected to the heat source heat exchanger by a pipeline; and a condenser through a pipeline The expander is connected; a pump is connected to the condenser and the heat source heat exchanger by a pipeline for driving a working fluid to flow through the heat source heat exchanger by the pump, the expansion And the condenser constitute an organic Rankine cycle, the working fluid has a critical pressure value; a pressure sensor for detecting an actual pressure value of the working fluid before entering the expander inlet; and a control component And determining a relationship between the actual pressure value of the working fluid and the critical pressure value. If the actual pressure value of the working fluid is greater than the critical pressure value, the control component controls the organic Rankine cycle system to wear The critical operation mode operates, and if the actual pressure value of the working fluid is less than the critical pressure value, the control element controls the organic Rankine cycle system to operate in a critical operation mode. An organic Rankine cycle system operable in subcritical and critical states as described in claim 12 The system further includes a temperature sensor for detecting an actual temperature value of the working fluid before entering the expander inlet. The control element has a supercritical working fluid pressure temperature database, and the supercritical working fluid pressure temperature data. The library has multiple sets of pressure and working temperature range data, each set of pressure and working temperature range data has a pressure value and a corresponding operating temperature range, and the organic Rankine cycle system is in the critical operating mode if the actual If the temperature value is greater than the upper limit of the operating temperature range, the control component increases an output frequency value or an output flow value of the pump, and if the actual temperature value is less than a lower limit value of the operating temperature range, the control component is lowered. The output frequency value of the pump or the output flow value. An organic Rankine cycle system operable in a subcritical and through critical state as recited in claim 13 wherein, in the through critical mode of operation, if the actual pressure value is greater than an allowable maximum pressure value of the organic Rankine cycle system, Then, the control element stops the organic Rankine cycle system, and if the actual pressure value is less than the critical pressure value, the control element switches the organic Rankine cycle system from the through critical operation mode to the subcritical operation mode. An organic Rankine cycle system operable in a subcritical and critical state as described in claim 13 wherein the control element has a superheat calculation module, and the superheat calculation module of the control element is based on the actual pressure value Calculating an actual superheat value of the working fluid with the actual temperature value. When the organic Rankine cycle is in the subcritical operation mode, if the actual superheat value is less than a lower limit of a preset superheat range, then And decreasing the output frequency value or the output flow value of the pump, if the actual superheat value is greater than a preset superheat range upper limit, increasing the output frequency value or the output flow value of the pump . An organic Rankine cycle system operable in a subcritical and breakthrough critical state as recited in claim 15, wherein in the subcritical operating mode, the actual pressure value is less than the organic Rankine cycle The minimum allowable pressure value of the system, the control element stops the organic Rankine cycle system, and if the actual pressure value is greater than the critical pressure value, the control element switches the organic Rankine cycle system from the subcritical operation mode To the critical operating mode. An organic Rankine cycle system operable in a subcritical and critical state as described in claim 12, wherein the working fluid is an organic refrigerant selected from the group consisting of HFCs (eg, R134a, R245fa, R32, R23, R41). , R125, R152a, R236fa, etc.), mixed refrigerant (such as R404A, R407C, R507A, R410A, etc.), HCs (such as R116, R218, RC318, n-pentane, etc.), FCs (such as butane, isobutene, propane, methane, etc.) One of the groups formed. An organic Rankine cycle system operable in a subcritical and critical state as described in claim 12, wherein the pump is a variable flow pump or a constant flow pump with a variable frequency motor. An organic Rankine cycle system operable in a subcritical and critical state as described in claim 12, wherein the expander is a turbine, a spiral expander, a scroll expander, a volumetric expander, or a reciprocating expander Wait. An organic Rankine cycle system operable in a subcritical and critical state as described in claim 12, further comprising a generator coupled to the expander to convert the rotational kinetic energy of the expander to an electrical energy output.