A heat recovery type energy storage liquid cooling system driven by solar energy

Abstract

The utility model belongs to the energy storage power station heat management technical field, concretely relates to a heat recovery type energy storage liquid cooling system driven by solar energy, it includes: solar energy heat storage system, power generation system, energy storage liquid cooling heat dissipation system and waste heat recovery system. The utility model's heat recovery type energy storage liquid cooling system driven by solar energy, the organic rankine cycle power generation system driven by solar energy is incorporated into the power supply circuit of energy storage liquid cooling, and the generated electric energy is directly supplied to the liquid cooling unit of liquid cooling system, replaces the power supply of power grid, recycles the waste heat of battery liquid cooling system for heating, and greatly improves the overall energy utilization efficiency of energy storage power station.

Description

Technical Field

[0001] This utility model belongs to the field of thermal management technology for energy storage power stations, and specifically relates to a solar-driven heat recovery liquid cooling system for energy storage. Background Technology

[0002] In recent years, driven by multiple favorable policies and business models, my country's energy storage industry has achieved leapfrog development and has become a key force supporting energy transformation. The importance of green energy is becoming increasingly prominent, and high-efficiency energy storage power stations are attracting much attention. However, some of the energy efficiency improvements in energy storage power stations come from the energy saving of liquid cooling equipment. Traditional energy storage liquid cooling systems need to continuously consume grid electricity to drive water pumps and compressors to maintain stable battery temperatures. At the same time, the waste heat generated during battery operation (usually 30–60°C) is directly emitted into the environment, which increases heat dissipation energy consumption and wastes thermal resources.

[0003] Therefore, improvements are needed to address the above technical issues. Utility Model Content

[0004] In view of the above-mentioned shortcomings in the existing technology, the present invention provides a solar-driven heat recovery energy storage liquid cooling system, which reduces the power consumption of the energy storage liquid cooling system and increases the utilization of battery waste heat.

[0005] To achieve the above-mentioned objectives, this utility model adopts the following technical solution:

[0006] A solar-driven heat recovery energy storage liquid cooling system includes: a solar thermal collection and storage system, a power generation system, an energy storage liquid cooling heat dissipation system, and a waste heat recovery system;

[0007] The solar thermal collection and storage system includes a solar thermal collection device and a thermal storage device;

[0008] The power generation system includes an evaporator, an expander, a condenser, a working fluid pump, and a generator. The heat source side of the evaporator is connected to a solar thermal collector, a heat storage device, a heat source inlet, and a heat source outlet through a first circulation pump to form a first circulation loop. The working fluid side of the evaporator is connected to the working fluid outlet, the expander, the condenser circulation loop, and the working fluid inlet through a working fluid pump to form a second circulation loop, which drives the expander to drive the generator to generate electricity.

[0009] The energy storage liquid cooling heat dissipation system includes a liquid chiller, a battery pack, and a cooling tower. The power input terminal of the liquid chiller is connected to the output terminal of the generator. The cooling end of the liquid chiller is connected to the cooling end outlet, cooling water supply pipeline, battery pack cold plate, cooling return water pipeline, and cooling end inlet through a first cooling circulation pump to form a cooling loop. The heat dissipation end of the liquid chiller is connected to the heat dissipation end outlet, heat dissipation water supply pipeline, cooling tower, heat dissipation return water pipeline, and heat dissipation end inlet through a second cooling circulation pump to form a heat dissipation loop.

[0010] The waste heat recovery system includes a heat recovery heat exchanger and a heating circuit. The heat source end inlet of the heat recovery heat exchanger is connected to the heat dissipation end outlet of the liquid chiller, the heat source end outlet of the heat recovery heat exchanger is connected to the heat dissipation end inlet of the liquid chiller, and the heat absorption end of the heat recovery heat exchanger is connected to the heating circuit.

[0011] As a preferred embodiment, the outlet of the heat storage device is connected to the heat source input end of the heat recovery heat exchanger, and the heat source output end of the heat recovery heat exchanger is connected to the first circulation loop, forming a supplementary heat loop as an auxiliary heat source.

[0012] As a preferred embodiment, a second circulation pump is connected before the heat source inlet of the heat recovery heat exchanger to increase the circulation efficiency through pressurized flow.

[0013] As a preferred embodiment, the heat source inlet of the heat recovery heat exchanger is connected to the heat dissipation outlet of the liquid chiller and the heat dissipation water supply pipeline through a first electric tee pipe. The heating circuit is equipped with a first temperature sensor, and the first electric tee pipe is electrically connected to the first temperature sensor. Thus, the heat dissipation flow rate of the first electric tee pipe can be controlled according to the temperature demand of the heating circuit.

[0014] As a preferred embodiment, the outlet of the heat storage device is connected to the heat source input end of the heat recovery heat exchanger and the heat source side inlet of the evaporator through a second electric tee pipe. The second electric tee pipe is electrically connected to the first temperature sensor, so that the heat replenishment flow of the second electric tee pipe can be controlled or switched according to the temperature demand of the heating circuit.

[0015] As a preferred embodiment, the solar thermal collector is equipped with an irradiation sensor, and a second temperature sensor is installed in front of the expander port. The irradiation sensor and the second temperature sensor are electrically connected to the first circulating pump, thereby enabling the flow rate of the first circulating pump to be controlled according to the solar irradiation and the steam temperature of the expander.

[0016] As a preferred option, the heat transfer medium in the first circulation loop is an aqueous solution of ethylene glycol or molten salt to ensure operation in extremely cold environments.

[0017] As a preferred embodiment, the heat-conducting working fluid in the second circulation loop is an organic working fluid R245fa, which has a low boiling point.

[0018] As a preferred embodiment, the heat transfer medium in the cooling circuit is an aqueous solution of ethylene glycol, the temperature of the heat transfer medium at the outlet of the cooling end of the liquid chiller is 5~15℃, the temperature of the heat transfer medium in the cooling return water pipe is 15~25℃, the liquid chiller has a refrigerant circulation loop inside, the refrigerant is refrigerant R134A, the temperature of the working medium in the heat dissipation water supply pipe is 35~40℃, and the thermal energy utilization efficiency is high.

[0019] As a preferred embodiment, the battery pack cold plate consists of several cold plates connected in parallel, and the battery pack cold plates are connected to a differential pressure balancing pipe to ensure balanced flow among the parallel cold plates.

[0020] Compared with the prior art, the advantages of this utility model are as follows: The solar-driven heat recovery energy storage liquid cooling system of this utility model incorporates the solar-driven organic Rankine cycle power generation system into the power supply circuit of the energy storage liquid cooling system. The generated power is directly supplied to the liquid cooling unit of the liquid cooling system, replacing the power grid supply. At the same time, the waste heat of the battery liquid cooling system is recovered for heating, which greatly improves the overall energy utilization efficiency of the energy storage power station. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the solar-driven heat recovery energy storage liquid cooling system according to Embodiment 1 of this utility model;

[0022] in:

[0023] 1. Thermal collection and storage system; 11. Thermal collection device; 12. Thermal storage device; 13. First circulating pump; 14. First electric three-way valve; 15. Irradiation sensor; 16. Pressure relief valve;

[0024] 2. Power generation system; 21. Evaporator; 22. Expander; 23. Condenser; 24. Generator; 25. Working fluid circulation pump; 26. Second temperature sensor;

[0025] 3. Energy storage liquid cooling heat dissipation system; 31. Liquid cooling unit; 311. Cooling water supply pipeline; 312. Cooling water return pipeline; 313. Heat dissipation water supply pipeline; 314. Heat dissipation water return pipeline; Battery pack cold plate; 32. Battery pack cold plate; 321. Differential pressure balance pipe; 33. Cooling tower; 34. First cooling circulation pump; 35. Second cooling circulation pump; 36. Second electric three-way valve;

[0026] 4. Waste heat recovery system; 41. Heat recovery heat exchanger; 42. Heating circuit; 43. Second circulation pump; 44. First temperature sensor. Detailed Implementation

[0027] To more clearly illustrate the embodiments of this utility model, the specific implementation methods of this utility model will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of this utility model. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0028] Example 1

[0029] like Figure 1As shown, this embodiment illustrates a solar-driven heat recovery energy storage liquid cooling system. The solar-driven heat recovery energy storage liquid cooling system includes: a solar thermal collection and storage system 1, a power generation system 2, an energy storage liquid cooling heat dissipation system 3, and a waste heat recovery system 4.

[0030] The solar thermal collection and storage system 1 includes a solar thermal collector 11 and a thermal storage device 12. The solar thermal collector absorbs solar radiation energy and converts it into heat energy. The thermal storage device 12 is used to store the heat energy generated by the solar thermal collector 11. Existing models that can achieve heat collection and heat storage functions can be selected. In this embodiment, the solar thermal collector 11 and the thermal storage device 12 are selected as vacuum tube collectors and phase change thermal storage devices.

[0031] The power generation system 2 includes an evaporator 21, an expander 22, a condenser 23, a working fluid pump, and a generator 24. The heat source side of the evaporator 21 is connected to the solar collector 11, the heat storage device 12, the heat source side inlet, and the heat source side outlet through the first circulation pump 13 to form a first circulation loop. The first circulation loop provides a heat source for the power generation system 2 through the solar collector and heat storage system 1. The first circulation pump 13 provides power to drive the working fluid to circulate. All components can form a closed loop. In this embodiment, after the working fluid is heated by the solar collector, the high-temperature working fluid flows into the heat storage device 12 to release sensible heat and latent heat. The cooled working fluid is driven by the first circulation pump 13 to re-enter the solar collector, completing a complete closed loop. The closed loop system has stable pressure and low working fluid loss and pollution. Furthermore, the working fluid in the first circulation loop can be an aqueous solution of ethylene glycol or molten salt to ensure operation in extremely cold environments. In this example, the working fluid in the first circulation loop is an aqueous solution of ethylene glycol, with an operating temperature range of -40℃ to 120℃. The working pressure of the solar thermal collector and storage system 1 is designed to be 0.6 MPa. A pressure relief valve 16 is also installed in the first circulation loop to improve the stability of system operation.

[0032] The working fluid side of evaporator 21 is connected to the working fluid side outlet, expander 22, condenser 23, and working fluid side inlet loop via a working fluid pump to form a second circulation loop, driving expander 22 to drive generator 24 to generate electricity; the power generation system 2 is an Organic Rankine Cycle (ORC) architecture. The heat energy output from solar thermal energy collection and storage system 1 flows into evaporator 21, heating the working fluid and causing it to evaporate into high-pressure saturated steam, which then enters expander 22. Adiabatic expansion converts thermal energy into mechanical energy, which is then converted into electrical energy by generator 24. The cooled, low-pressure working fluid steam flows into condenser 23 and condenses into low-pressure liquid working fluid. The liquid working fluid is pressurized and sent back to evaporator 21 via working fluid circulation pump 25 to complete the closed-loop cycle. Furthermore, the structure of power generation system 2 is not limited; for example, it can be a multi-stage Organic Rankine Cycle architecture.

[0033] Furthermore, the heat transfer medium in the second circulation loop is the organic working medium R245fa, which realizes the conversion of heat energy into electrical energy. With a boiling point of 15.3℃, it is low in boiling point and highly efficient. Its working cycle is as follows: Evaporation and heat absorption: The high-temperature heat energy output from the solar thermal storage system 1 is input into the evaporator 21, heating the R245fa working medium and causing it to change phase to 1.2MPa / 80℃ high-pressure saturated steam; Expansion and work: The high-pressure steam drives the expander 22 for adiabatic expansion, reducing the pressure to 0.25MPa and the temperature to 45℃. During this process... The thermal energy to mechanical energy conversion efficiency reaches 75-82%; power generation output: the mechanical torque output by the expander 22 drives the rotor of the generator 24 to rotate, generating 50Hz AC power (conversion efficiency ≥96%); condensation phase change: low-pressure steam enters the condenser 23, and the latent heat is carried away by air cooling, and the working fluid condenses into a low-pressure saturated liquid of 0.25MPa / 35℃; working fluid reflux: liquid R245fa is pressurized to 1.2MPa by the working fluid circulation pump 25 and returned to the evaporator 21 to restart the circulation. The pump power consumption accounts for about 4% of the power generation.

[0034] The energy storage liquid cooling heat dissipation system 3 includes a liquid cooler unit 31, a battery pack, and a cooling tower 33. The power input terminal of the liquid cooler unit 31 is connected to the output terminal of the generator 24, and the liquid cooler unit 31 is directly powered by the power generation system 2.

[0035] The liquid cooling system consists of two independent loops: a battery cooling loop and a heat dissipation loop. The cooling end of the liquid cooler unit 31 is connected to the cooling end outlet, cooling water supply pipe 311, battery pack cold plate 32, cooling water return pipe 312, and cooling end inlet via a first cooling circulation pump 34 to form a cooling loop. The heat dissipation end of the liquid cooler unit 31 is connected to the heat dissipation end outlet, heat dissipation water supply pipe 313, cooling tower 33, heat dissipation water return pipe 314, and heat dissipation end inlet via a second cooling circulation pump 35 to form a heat dissipation loop. The cooling loop is used for battery heat dissipation, and the heat dissipation loop is used to dissipate the heat acquired by the cooling loop. The liquid cooler unit 31 transfers heat between the cooling loop and the heat dissipation loop.

[0036] Furthermore, the liquid-cooled unit 31 has an internal refrigerant circulation loop, with refrigerant R134A as the working fluid. The refrigerant in the evaporator inside the liquid-cooled unit 31 absorbs heat from the chilled water, vaporizes, and is then pressurized and heated by the compressor to form a high-temperature, high-pressure gaseous refrigerant at 120-150°C. This gaseous refrigerant releases heat to the working fluid in the internal condenser. The internal evaporator-compressor-expansion valve-condenser completes a closed-loop cycle. Furthermore, the operating power of the liquid-cooled unit 31 can be controlled based on the temperature feedback from the battery BMS.

[0037] In this embodiment, the heat transfer medium in the cooling circuit is an aqueous solution of ethylene glycol. The liquid chiller 31 outputs a working medium at a temperature of 5-15°C from the cooling circuit side, meaning the temperature of the working medium at the cooling end outlet of the liquid chiller 31 is 5-15°C. This working medium is then transported to the battery pack cold plate 32 via the cooling water supply pipe 311. The heat from the battery compartments is conducted to the working medium through the wall of the cold plate. Furthermore, in this example, the battery pack cold plate 32 consists of several cold plates connected in parallel. The battery pack cold plate 32 is also connected to a differential pressure balance pipe 321 to ensure balanced flow among the parallel cold plates. The working medium is heated to 15-25°C by the battery pack cold plate 32, meaning the temperature of the working medium in the cooling return water pipe 312 is 15-25°C. The first cooling circulation pump 34 pressurizes the working medium and sends it back to the liquid chiller 31 via the cooling return water pipe 312, completing the closed-loop circulation.

[0038] The working fluid temperature output from the heat dissipation circuit side of the liquid chiller unit 31 is 35~40℃, meaning the working fluid temperature in the heat dissipation water supply pipe 313 is 35~40℃. This 35~40℃ working fluid enters the cooling tower 33, where, driven by a fan, it undergoes evaporative convection heat exchange with the air, cooling down to 30~32℃. The working fluid is then pressurized and returned to the liquid chiller unit 31 via the second cooling circulation pump 35, completing the open-loop circulation.

[0039] The waste heat recovery system 4 includes a heat recovery heat exchanger 41 and a heating circuit 42. The heat source inlet of the heat recovery heat exchanger 41 is connected to the heat dissipation outlet of the liquid chiller unit 31 to recover the waste heat from the liquid cooling system's refrigerant at 35-40°C. The heat source outlet of the heat recovery heat exchanger 41 is connected to the heat dissipation inlet of the liquid chiller unit 31 to form a circulation. The heat absorption end of the heat recovery heat exchanger 41 is connected to the heating circuit 42, supplying domestic hot water to the building via the heating water circuit. The heat recovery heat exchanger 41 can be any type capable of heat exchange, such as a plate heat exchanger; this embodiment does not impose any limitations.

[0040] Furthermore, the outlet of the heat storage device 12 is connected to the heat source input end of the heat recovery heat exchanger 41, and the heat source output end of the heat recovery heat exchanger 41 is connected to the first circulation loop, forming a supplementary heat loop as an auxiliary heat source.

[0041] Furthermore, a second circulation pump 43 is connected before the heat source inlet of the heat recovery heat exchanger 41 to pressurize the flow and improve circulation efficiency.

[0042] Furthermore, the heat source inlet of the heat recovery heat exchanger 41 is connected to the heat dissipation outlet of the liquid chiller unit 31 and the heat dissipation water supply pipe 313 via a first electric tee pipe. The heating circuit 42 is equipped with a first temperature sensor 44, and the first electric tee pipe is electrically connected to the first temperature sensor 44. Thus, the heat dissipation flow rate of the first electric tee pipe can be controlled according to the temperature demand of the heating circuit. Taking this embodiment as an example: In the battery cooling circuit, the 15°C working fluid is transported from the liquid chiller unit 31 to the battery pack, absorbs heat and rises to 20°C, and then returns to the liquid chiller unit 31 via the first cooling circulation pump 34; In the heat dissipation circuit, the 37°C working fluid is discharged from the liquid chiller unit 31 and distributed proportionally to the waste heat recovery system 4 or the cooling tower 33 via the first electric tee pipe diverter valve according to the ratio β. Among them: the working fluid flowing to the cooling tower 33 is cooled to 32°C by the tower fan; the working fluid flowing to the waste heat recovery system 4 is connected to the waste heat recovery heat exchanger 41. The first electric three-way valve 14 is electrically connected to the first temperature controller for diversion control and regulation. The two working fluids eventually return to the liquid chiller unit 31 via a confluence. The waste heat recovery β value is inversely proportional to the power consumption of the cooling tower 33 fan; when β=100%, the fan power can be reduced by up to 36%.

[0043] Furthermore, the outlet of the heat storage device 12 is connected to the heat source input end of the heat recovery heat exchanger 41 and the heat source side inlet of the evaporator 21 through the second electric three-way valve 36. The second electric three-way valve 36 is electrically connected to the first temperature sensor 44. Thus, the supplementary heat flow of the second electric three-way valve 36 can be controlled or switched according to the temperature demand of the heating circuit, so as to realize the automatic switching or flow control of the outlet of the heat storage device 12 to the evaporator 21 of the power generation system 2 or the heat recovery heat exchanger 41. Furthermore, the control of the second electric three-way valve 36 can adopt a multi-condition or multi-condition interlocking control strategy.

[0044] Furthermore, an irradiance sensor 15 is installed on the solar collector 11, and a second temperature sensor 26 is installed in front of the port of the expander 22. The irradiance sensor 15 and the second temperature sensor 26 are electrically connected to the first circulating pump 13, so that the flow rate of the first circulating pump 13 can be controlled according to the solar irradiance and the steam temperature of the expander 22.

[0045] In this embodiment, the solar thermal collection and storage system 1 collects solar energy through a heat-conducting working fluid and stores it in the thermal storage device 12. The stored heat drives the low-boiling-point organic working fluid in the organic Rankine cycle power generation system 2 to evaporate and expand, which drives the expander 22 to output mechanical work to drive the generator 24 to generate electricity. The generated electricity is supplied to the liquid cooling unit 31 in the energy storage liquid cooling heat dissipation system 3. The liquid cooling unit 31 performs forced liquid cooling on the battery pack through the battery pack cold plate 32. At the same time, the waste heat recovery system 4 captures the battery waste heat discharged by the liquid cooling unit 31 through the heat recovery heat exchanger 41 and delivers the recovered heat to the building heating network or domestic hot water system.

[0046] According to industry data from the "Energy Storage Industry Research White Paper (2024)" published by the Zhongguancun Energy Storage Industry Technology Alliance, liquid cooling systems rely on grid power for more than 15% of the total energy consumption of power plants. This utility model innovatively achieves triple energy optimization: using solar energy to drive the cooling of the energy storage system, replacing grid power supply and reducing grid energy consumption of the liquid cooling unit; realizing the thermoelectric conversion of low-grade solar energy through an organic Rankine cycle power generation system; and secondary recovery of battery heat for heating, thereby increasing the overall energy utilization rate of the system by 30%-38%.

[0047] It should be noted that the technical features of the above embodiments can be freely combined as needed. The above description is only a detailed explanation of the preferred embodiments and principles of this utility model. For those skilled in the art, there will be changes in the specific implementation methods based on the ideas provided by this utility model, and these changes should also be considered within the protection scope of this utility model.

Claims

1. A solar-driven heat recovery energy storage liquid cooling system, characterized in that, include: Solar thermal collection and storage systems, power generation systems, energy storage liquid cooling and heat dissipation systems, and waste heat recovery systems; The solar thermal collection and storage system includes a solar thermal collection device and a thermal storage device; The power generation system includes an evaporator, an expander, a condenser, a working fluid pump, and a generator. The heat source side of the evaporator is connected to a solar thermal collector, a heat storage device, a heat source inlet, and a heat source outlet through a first circulation pump to form a first circulation loop. The working fluid side of the evaporator is connected to the working fluid outlet, the expander, the condenser circulation loop, and the working fluid inlet through a working fluid pump to form a second circulation loop, which drives the expander to drive the generator to generate electricity. The energy storage liquid cooling heat dissipation system includes a liquid chiller, a battery pack, and a cooling tower. The power input terminal of the liquid chiller is connected to the output terminal of the generator. The cooling end of the liquid chiller is connected to the cooling end outlet, cooling water supply pipeline, battery pack cold plate, cooling return water pipeline, and cooling end inlet through a first cooling circulation pump to form a cooling loop. The heat dissipation end of the liquid chiller is connected to the heat dissipation end outlet, heat dissipation water supply pipeline, cooling tower, heat dissipation return water pipeline, and heat dissipation end inlet through a second cooling circulation pump to form a heat dissipation loop. The waste heat recovery system includes a heat recovery heat exchanger and a heating circuit. The heat source end inlet of the heat recovery heat exchanger is connected to the heat dissipation end outlet of the liquid chiller, the heat source end outlet of the heat recovery heat exchanger is connected to the heat dissipation end inlet of the liquid chiller, and the heat absorption end of the heat recovery heat exchanger is connected to the heating circuit.

2. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The outlet of the heat storage device is connected to the heat source input end of the heat recovery heat exchanger, and the heat source output end of the heat recovery heat exchanger is connected to the first circulation loop.

3. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, A second circulation pump is connected before the heat source inlet of the heat recovery heat exchanger.

4. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The heat source inlet of the heat recovery heat exchanger is connected to the heat dissipation outlet of the liquid chiller and the heat dissipation water supply pipeline through a first electric tee pipe. The heating circuit is equipped with a first temperature sensor, and the first electric tee pipe is electrically connected to the first temperature sensor.

5. The solar-driven heat recovery energy storage liquid cooling system as described in claim 2, characterized in that, The outlet of the heat storage device is connected to the heat source input end of the heat recovery heat exchanger and the heat source side inlet of the evaporator through a second electric tee pipe, and the second electric tee pipe is electrically connected to the first temperature sensor.

6. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, An irradiation sensor is installed on the solar thermal collector, and a second temperature sensor is installed in front of the expander port. The irradiation sensor and the second temperature sensor are electrically connected to the first circulating pump.

7. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The heat-conducting medium in the first circulation loop is an aqueous solution of ethylene glycol or a molten salt.

8. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The heat-conducting working fluid in the second circulation loop is the organic working fluid R245fa.

9. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The heat transfer medium in the cooling circuit is an aqueous solution of ethylene glycol. The temperature of the heat transfer medium at the outlet of the cooling end of the liquid chiller is 5~15℃, and the temperature of the heat transfer medium in the cooling return water pipe is 15~25℃. The liquid chiller has a refrigerant circulation circuit inside, and the refrigerant is refrigerant R134A. The temperature of the working medium in the heat dissipation water supply pipe is 35~40℃.

10. The solar-driven heat recovery energy storage liquid cooling system as described in claim 1, characterized in that, The battery pack cold plate consists of several cold plates connected in parallel, and the battery pack cold plate is connected to a differential pressure balance pipe.

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