Organic Rankine Cycle Power Generation Unit

Abstract

A simple organic Rankine cycle power generation device that can efficiently generate electricity is provided. The organic Rankine cycle power generation device includes: a pump (2) that delivers condensed actuating medium; an evaporator (3) that evaporates the actuating medium from the pump (2) through heat exchange with a heat source; an expander (4) driven by the steam evaporated by the evaporator (3); a condenser (5) that can deliver the steam condensed in the expander (4) through the pump (2); and a generator (6) whose input shaft is connected to the output shaft of the expander (4). The generator (6) is designed such that its rated operating torque is the same as that of the expander (4).

Description

Technical Field

[0001] This invention relates to an organic Rankine cycle power generation device that utilizes the organic Rankine cycle. Prior Technology

[0002] Previously, organic Rankine cycle power generation, which extracts heat from high-temperature heat sources (such as geothermal, industrial exhaust heat, solar thermal, biomass energy, etc.), boils an organic medium, uses its steam to rotate a turbine (expander) to generate electricity, and then cools the steam through a heat exchanger to turn it back into a liquid. The liquid is then pumped back to the heat exchanger and heated to turn back into steam. This type of power generation is well-known. As an example, the electric regenerative Rankine cycle system described in Patent Document 1 can be cited.

[0003] In the system described in Patent Document 1, a target speed map is used to represent the relationship between the heat of the heating fluid and the rotational speed of the electric generator, which is also the speed at which the heat of the heating fluid input to the evaporator is used as the target rotational speed of the electric generator. Feedback control is then applied to the torque of the electric generator. This allows the expander to be rotated using the rotational speed at which stable and efficient power is obtained. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-152029 Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] However, according to the system in Patent Document 1, the rotational speed obtained by inputting the heat of the heating fluid into the evaporator into the target rotational speed map is used as the target rotational speed of the electric generator to feed back and control the torque of the electric generator, which is why the system is complex.

[0007] The object of the present invention is to provide a simple organic Rankine cycle power generation device that can generate electricity efficiently, in view of the problems of the prior art. [Methods used to solve problems]

[0008] (1) The organic Rankine cycle power generation device of the present invention comprises: A pump is used to deliver a solidified working medium; An evaporator that evaporates the aforementioned actuating medium from the aforementioned pump through heat exchange with a heat source; An expander, which is driven by steam evaporated by the aforementioned evaporator; A condenser, which can condense the steam expanded in the aforementioned expander and then pump it out using the aforementioned pump; and A generator, whose input shaft is connected to the output shaft of the aforementioned expander; characterized in that: The aforementioned generator is designed such that its rated operating torque is consistent with that of the aforementioned expander.

[0009] According to the present invention, the output shaft of the expander is connected to the input shaft of the generator. Because the rated operating torque of the generator is the same as that of the expander, the rotational torque generated by the expander can be used to the maximum extent. Therefore, the output of the generator can be maximized, achieving high power generation efficiency.

[0010] Furthermore, as mentioned above, proper matching of the generator and expander allows for stable generator operation under load variations by adjusting the torque (current) solely in accordance with the generator's output voltage, thus improving system reliability. Moreover, the matching torque of the generator and expander minimizes mechanical load, further enhancing system stability. Additionally, proper matching of the generator and expander minimizes the required generator size, reducing system costs.

[0011] (2) In this invention, the torque of the aforementioned generator during rated operation can be the torque when the generator's efficiency is at its highest. Accordingly, because the generator's efficiency is at its highest during rated operation, the generator can generate maximum power and minimize energy loss.

[0012] (3) In this invention, a torque control unit may also be included, which adjusts the output current of the generator based on the output voltage of the aforementioned generator. Since the output voltage corresponds to the rotational speed and the output current corresponds to the torque, the torque control unit monitors the output voltage and adjusts the output current as necessary. In this way, the generator can be reliably prevented from deviating from its rated operating state, and the stable operation of the generator can be maintained, thereby improving the reliability of the device. Simple Explanation of the Diagram

[0013] [Figure 1] shows a block diagram of the configuration of an organic Rankine cycle power generation device according to one embodiment of the present invention. Implementation

[0014] Hereinafter, embodiments of the present invention will be described using drawings. FIG1 shows the configuration of an organic Rankine cycle power generation device according to an embodiment of the present invention.

[0015] As shown in Figure 1, the organic Rankine cycle power generation device includes: a tank 1 for storing the operating medium, a pump 2 for discharging the medium stored in the tank 1, an evaporator 3 for evaporating the operating medium discharged by the pump 2 through heat exchange with a heat source, an expander 4 driven by the operating medium evaporated by the evaporator 3, a condenser 5 for returning the operating medium expanded in the expander 4 to the tank 1, and a generator 6 whose input shaft is connected to the output shaft of the expander 4.

[0016] As the actuating medium for the organic Rankine cycle power generation device, organic fluorocarbons or organic compounds such as cyclopentane and cyclohexane can be used. As the heat source 7 suitable for the organic Rankine cycle power generation device, low-temperature heat sources such as waste heat from industrial processes, solar heat, geothermal energy, and biomass fuels can be used. The evaporator 3 has the function of transferring heat obtained from the heat source 7 to the liquid actuating medium, changing it from a liquid state to a steam state.

[0017] Expander 4 has the function of expanding the working medium under high pressure and using the energy released by the working medium to rotate the turbine by achieving a low pressure state. Regarding such positive displacement expanders, the types are known: steam turbines are used in large-scale power generation, and screw expanders are used in medium-scale power generation of 20-50 kW; however, for small-scale power generation of less than 10 kW or power generation from low-temperature heat sources, it is preferable to use a turbine-type expander that is highly efficient, has low vibration, and is relatively small.

[0018] The condenser 5 has the function of returning the low-temperature actuating medium vapor discharged from the turbine of the expander 4 to a liquid state. For small-scale installations, an air-cooled condenser 5 is preferred, while for large-scale installations, a water-cooled condenser 5 is preferred.

[0019] The generator 6 is designed so that its rated operating torque is the same as that of the expander 4. The rated operating torque of the generator 6 is the torque at which the generator 6 achieves maximum efficiency.

[0020] Furthermore, the organic Rankine cycle power generation device includes: a torque control unit 8 that adjusts the output current I of the generator 6 based on the output voltage V of the generator 6; a system control unit 9 that controls the flow rate of the actuating medium; and a lithium-ion battery 10 that stores the electricity generated by the generator 6. The torque control unit 8 adjusts the current value I flowing to the generator 6 by changing the load connected to the output port side of the generator 6.

[0021] The flow rate of the actuating medium delivered by pump 2 is proportional to the rotational speed of pump 2, which is driven by a motor. The system control unit 9 controls the rotational speed of the motor through inverter 11 to maximize the flow rate of the actuating medium.

[0022] In designing generator 6, as described above, the torque of generator 6 is designed to be consistent with the torque of expander 4. In this case, firstly, expander 4 is driven without connecting generator 6. The speed of expander 4 is determined by determining the mass flow rate of the actuating medium flowing in expander 4. Next, the theoretical adiabatic thermal gradient of the actuating medium used in expander 4 is determined by considering the pressure difference between the inlet and outlet of the actuating medium.

[0023] The actual rotational energy, i.e., shaft driving force, of the expander 4 is determined by multiplying the theoretical adiabatic heat drop by the efficiency of the expander 4. Since this shaft driving force is proportional to the rotational speed and torque, the torque of the expander 4 can be calculated as a value.

[0024] Therefore, because the expander 4 and the generator 6 rotate at the same speed, the torque of the generator 6 is designed to be consistent with the torque calculated for the expander 4. Moreover, the generator 6 is designed to maintain a constant torque until it reaches rated operation.

[0025] Furthermore, the torque of generator 6 is proportional to the current flowing into generator 6, but efficiency decreases due to heat loss caused by heat generation as the current increases. Also, the number of coil windings contributes to the voltage. Moreover, there is an optimal relationship between wire diameter and the number of windings. These factors were also taken into consideration in the design of generator 6. In this way, the relationship between the speed and torque of expander 4 can be made to match the optimal relationship between the speed and torque of generator 6 for optimal efficiency.

[0026] In this configuration, during the operation of the organic Rankine cycle power generation unit, in accordance with the instructions from the system control unit 9, the pump 2 delivers the actuating medium from the tank 1 to the evaporator 3. The evaporator 3 converts the delivered liquid actuating medium into a steam state through heat exchange with the heat source 7 and delivers it to the expander 4.

[0027] Expander 4 receives the high-temperature, high-pressure actuating medium and expands it, converting the expansion force into rotational force, causing the output shaft of expander 4 to rotate. Condenser 5 cools and condenses the expanded steam actuating medium in expander 4 and returns it to tank 1.

[0028] On the other hand, in the generator 6, whose input shaft is connected to the output shaft of the expander 4, its rotor rotates at the same speed as the output shaft of the expander 4 and generates electricity. At this time, when the expander 4 and the generator 6 are in rated operating condition, the torque of the expander 4 is the same as that of the generator 6, so the generator 6 uses the rotational torque generated by the expander 4 to the maximum extent and generates electricity with high power generation efficiency.

[0029] During this period, the torque control unit 8 controls the current I corresponding to the torque of the generator 6 based on the output voltage V corresponding to the rotational speed of the generator 6, preventing the generator 6 from deviating from its rated operating state due to load changes, etc. In this way, power generation by the generator 6 can be carried out continuously at high power generation efficiency. The electricity generated by the generator 6 is stored in the lithium-ion battery 10 and supplied to other loads.

[0030] As described above, according to this embodiment, because the rated operating torque of the generator 6 is the same as the rated operating torque of the expander 4, the rotational torque generated by the expander 4 can be utilized to the maximum extent. Therefore, the output of the generator 6 can be maximized, achieving high power generation efficiency.

[0031] Furthermore, due to the appropriate matching of the torque relationship between the speed of generator 6 and expander 4, the rated operating state can be easily maintained under conditions such as load fluctuations by controlling the voltage V and current I of generator 6 caused by torque control unit 8, thus maintaining stable operation of the generator. In this way, the reliability of the organic Rankine cycle power generation device can be improved.

[0032] Furthermore, because the torques of generator 6 and expander 4 are consistent, the torque control unit 8 only monitors the voltage V for simple control, thereby minimizing the mechanical load and improving the stability of the device. Moreover, through this proper matching of generator 6 and expander 4, the necessary size of generator 6 can be minimized, reducing the cost of the organic Rankine cycle power generation device.

[0033] In particular, since the estimated torque map or target speed map and torque feedback control are not necessary for the electric regenerative Rankine cycle system disclosed in Patent Document 1 above, the device configuration or control method can be simplified.

[0034] 1: slot 2: Pump 3: Evaporator 4: Expander 5: Condenser 6: Generator 7: Heat source 8: Torque Control Unit 9: System Control Department 10: Lithium-ion batteries 11: Inverter

Claims

1. An organic Rankine cycle power generation device, comprising: a pump for discharging condensed actuating medium; an evaporator for evaporating the actuating medium from the pump via heat exchange with a heat source; an expander driven by steam evaporated by the evaporator; a condenser for condensing the steam expanded by the expander and then discharging it using the pump; a generator with its input shaft connected to the output shaft of the expander; and a torque control unit for adjusting the output current of the generator according to the output voltage of the generator; wherein: The aforementioned generator is designed such that its input shaft is connected to the output shaft of the aforementioned expander and the rated operating torque of the generator is consistent with the rated operating torque of the expander; the aforementioned torque control unit controls the current corresponding to the torque of the generator based on the output voltage corresponding to the rotational speed of the aforementioned generator, so as to prevent the generator from deviating from the rated operating state due to load changes.

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