Carbon dioxide heat pump energy storage system coupled with solar energy utilization

Abstract

The application discloses a carbon dioxide heat pump energy storage system coupled with solar energy utilization and belongs to the technical field of energy storage systems. The carbon dioxide heat pump energy storage system coupled with solar energy utilization comprises a tower type solar heat collecting subsystem, a heat pump energy storage subsystem, a supercritical carbon dioxide power cycle energy releasing subsystem and a transcritical carbon dioxide power cycle energy releasing subsystem. The application reasonably utilizes the high heat storage temperature feature of the tower type solar heat collecting system, effectively improves the turbine inlet temperature of the energy storage system without improving the compressor pressure ratio of the heat pump energy storage system, and improves the energy storage system efficiency. The turbine exhaust of the transcritical carbon dioxide power cycle system is condensed into liquid by the cold energy stored in the heat pump energy storage system, and the cold energy stored in the heat pump energy storage system is efficiently and reasonably utilized.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a carbon dioxide heat pump energy storage system coupled with solar energy utilization. Background Art

[0002] With the large-scale integration of renewable energy sources such as wind and solar power, their intermittent and unstable nature poses significant challenges to the safe and stable operation of the power grid, leading to widespread "wind and solar curtailment" (abandonment). Energy storage systems can decouple the generation and consumption of power on the grid, reducing the impact of renewable energy integration on the grid and increasing the rate of renewable energy integration.

[0003] Compared to other existing energy storage methods, heat pump energy storage systems have the advantages of high energy storage density, no geographical restrictions, low environmental impact, and low investment. They are currently the most promising new energy storage method. The heat pump energy storage system uses a heat pump cycle to convert electricity from renewable energy sources such as wind power and solar power that cannot be connected to the grid into cold energy and heat energy for storage during the low-load phase of the power grid. During the high-load phase of the power grid, the stored cold energy and heat energy are converted into electricity and transmitted to the power grid. Because it uses a heat pump cycle to convert electricity into cold energy and heat energy, if its compressor pressure ratio is small, there is a problem of low heat storage temperature. If the compressor pressure ratio is increased, the compressor operating parameters will be too high, posing a challenge to the safe and stable operation of the system. In addition, the cold energy stored in the currently proposed heat pump energy storage system is not fully utilized. Summary of the Invention

[0004] In view of the problems of low heat storage temperature and insufficient utilization of stored cold energy in the above-mentioned existing heat pump energy storage system, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to provide a carbon dioxide heat pump energy storage system coupled with solar energy utilization, which aims to solve the technical problems of low heat storage temperature and insufficient utilization of cold energy in traditional heat pump energy storage systems.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0007] A tower-type solar thermal collection subsystem includes a heliostat field and a solar energy storage unit corresponding to the heliostat field;

[0008] A heat pump energy storage subsystem comprising a heat pump compressor, a heat pump system heat energy storage unit connected to the heat pump compressor via a gate valve, a heat pump system heat recovery unit connected to the heat pump system heat energy storage unit via a gate valve, a heat pump expander connected to the heat pump system heat recovery unit via a gate valve, and a heat pump system cold energy storage unit connected to the heat pump expander via a gate valve;

[0009] A supercritical carbon dioxide power cycle energy release subsystem, comprising a super-II compressor and a super-II turbine connected to the solar energy storage unit, and also comprising a cooler disposed between the super-II compressor and the super-II turbine;

[0010] And, a transcritical carbon dioxide power cycle energy release subsystem includes a trans-turbine connected to the cooler, a condenser connected to the trans-turbine, and a working fluid pump connected to the condenser.

[0011] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization described in the present invention, the solar energy storage unit includes a receiver corresponding to the heliostat field, a molten salt cold tank and a molten salt hot tank connected to the receiver through a gate valve, and a molten salt heat exchanger connected to the molten salt cold tank and the molten salt hot tank through a gate valve.

[0012] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization of the present invention, the heat pump system heat energy storage part includes a packed bed heat accumulator connected to the heat pump compressor through a gate valve.

[0013] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization described in the present invention, the heat pump system heat recovery part includes a heat regenerator connected to the heat pump system heat energy storage part, a heat pump expander, a heat pump system cold energy storage part and a heat pump compressor.

[0014] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization described in the present invention, the cold energy storage part of the heat pump system includes a heat exchanger connected to the heat pump expander, and a refrigerant hot tank and a refrigerant cold tank connected to the heat exchanger through a gate valve.

[0015] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization of the present invention, the orientation of the heliostat field of the tower solar collector subsystem can be adjusted in real time as the sun moves.

[0016] As a preferred solution of the carbon dioxide heat pump energy storage system coupled with solar energy utilization of the present invention, the medium used in the packed bed heat accumulator is pebble medium.

[0017] Beneficial effects of the present invention: The present invention rationally utilizes the high heat storage temperature characteristic of the tower solar thermal collection system, and utilizes the tower solar thermal collection system to effectively increase the turbine inlet temperature of the energy storage system without increasing the compressor pressure ratio of the heat pump energy storage system, thereby improving the efficiency of the energy storage system; utilizes the cold energy stored in the heat pump energy storage system to condense the turbine exhaust of the transcritical carbon dioxide power cycle system into liquid, effectively reducing the turbine back pressure of the transcritical carbon dioxide power cycle system, improving the working capacity of the transcritical carbon dioxide power cycle system, and realizing the efficient and reasonable utilization of the cold energy stored in the heat pump energy storage system. In summary, the present invention effectively improves the turbine inlet parameters of the energy storage system without increasing the compressor pressure ratio of the heat pump energy storage system, and realizes the efficient and reasonable utilization of the cold energy stored in the heat pump energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort. Among them:

[0019] Figure 1 Schematic diagram of the overall structure of the heat pump energy storage system of the present invention. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0023] Furthermore, the present invention is described in detail with reference to schematic diagrams. For ease of illustration, when describing the embodiments of the present invention, cross-sectional views illustrating device structures may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of protection of the present invention. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0024] Example 1

[0025] Reference Figure 1 , which is the first embodiment of the present invention, provides a carbon dioxide heat pump energy storage system coupled with solar energy utilization, the device comprising:

[0026] The tower solar thermal collection subsystem 100 includes a heliostat field 101 and a solar energy storage unit 10 corresponding to the heliostat field 101. The heliostat field 101 reflects and focuses sunlight onto the solar energy storage unit 10. The solar energy storage unit 10 absorbs this solar radiation and converts it into thermal energy in a heat storage medium such as molten salt, which is then stored and further utilized.

[0027] The heat pump energy storage subsystem 200 includes a heat pump compressor 201, a heat pump system heat energy storage unit 20 connected to the heat pump compressor 201 through a gate valve, a heat pump system heat recovery unit 21 connected to the heat pump system heat energy storage unit 20 through a gate valve, a heat pump expander 204 connected to the heat pump system heat recovery unit 21 through a gate valve, and a heat pump system cold energy storage unit 22 connected to the heat pump expander 204 through a gate valve. The heat pump system heat energy storage unit 20 is used to absorb and store heat energy of the heat pump energy storage system, and the heat pump system cold energy storage unit 22 is used to absorb and store cold energy of the heat pump energy storage system. The heat pump system heat energy storage unit 20 and the heat pump system cold energy storage unit 22 are connected to the heat pump system heat recovery unit 21 through a gate valve to recover heat energy of the working fluid at the outlet of the heat pump system heat energy storage unit 20.

[0028] The supercritical carbon dioxide power cycle energy release subsystem 300 includes a super-second compressor 301 and a super-second turbine 302 connected to the solar energy storage unit 10, as well as a cooler 303 disposed between the super-second compressor 301 and the super-second turbine 302. This subsystem functions during the energy release phase, converting the thermal energy stored in the heat pump energy storage system 200 and the tower solar thermal collection system 100 into electrical energy. The super-second compressor 301 compresses the carbon dioxide to a supercritical state, which then enters the heat pump system thermal energy storage unit 20 to be heated to a certain temperature, and then enters the molten salt heat exchanger 105 to be further heated. The super-second turbine 302 utilizes the heated carbon dioxide to expand and perform work, driving a generator to generate electricity. The carbon dioxide working fluid that has completed the expansion work in the super-second turbine 302 enters the cooler 303 to be cooled, and then the cooled carbon dioxide working fluid enters the super-second compressor 301 to restart the cycle.

[0029] In addition, the transcritical carbon dioxide power cycle energy release subsystem 400 includes a trans-turbine 401 connected to the cooler 303, a condenser 402 connected to the trans-turbine 401, and a working fluid pump 403 connected to the condenser 402. This subsystem also works in the energy release stage, using the heat energy of the turbine exhaust of the super-turbine 302 and the cold energy stored in the heat pump energy storage subsystem 200 to generate electricity. The trans-turbine 401 uses this heat energy to expand and do work, and the condenser 402 is responsible for using the cold energy stored in the heat pump energy storage subsystem 200 to condense the carbon dioxide discharged from the trans-turbine 401, and the working fluid pump 403 returns the condensed carbon dioxide to the system for recycling.

[0030] The solar energy storage unit 10 includes a receiver 102 corresponding to the heliostat field 101, a molten salt cold tank 103 and a molten salt hot tank 104 connected to the receiver 102 through a gate valve, and a molten salt heat exchanger 105 connected to the molten salt cold tank 103 and the molten salt hot tank 104 through a gate valve. The molten salt cold tank 103 is used to store the initial low-temperature molten salt, while the molten salt hot tank 104 is used to store the high-temperature molten salt heated by the receiver 102. The gate valve plays a key role in controlling the flow direction and flow of the molten salt to ensure the effective transfer and storage of thermal energy.

[0031] The system has two working stages: energy storage stage and energy release stage:

[0032] When the power grid is in a low-load period and the wind farm has surplus power that cannot be connected to the grid, the system is in the energy storage stage:

[0033] Gate valves V1 and V2 are open, while gate valves V3 and V4 remain closed. The low-temperature molten salt thermal storage medium stored in the molten salt cold tank 103 enters the receiver 102. The heliostat field 101 reflects sunlight, focusing it onto the receiver 102 located on the tower. In the receiver 102, the low-temperature molten salt thermal storage medium is heated by the reflected and focused sunlight, turning it into high-temperature molten salt thermal storage medium. The high-temperature molten salt thermal storage medium is then stored in the molten salt hot tank 104.

[0034] Gate valves V5, V6, V9, and V10 are open, while gate valves V7, V8, V11, and V12 remain closed. Heat pump compressor 201 compresses the incoming carbon dioxide to a high-temperature, high-pressure state. The high-temperature, high-pressure carbon dioxide then enters packed bed regenerator 202. Packed bed regenerator 202 is filled with pebbles as a heat storage medium. The high-temperature, high-pressure carbon dioxide exchanges heat with the pebbles in the packed bed regenerator 202, transferring the heat energy it carries to the pebbles for storage. The high-pressure carbon dioxide, having completed heat exchange in packed bed regenerator 202, enters regenerator 203 from its hot-side inlet, where it exchanges heat with low-pressure carbon dioxide entering from its cold-side inlet. This increases the temperature of the low-pressure carbon dioxide entering heat pump compressor 201 and reduces the temperature of the high-pressure carbon dioxide entering heat pump expander 204. The high-pressure carbon dioxide working medium, which has completed heat exchange in regenerator 203, enters heat pump expander 204, where it expands and performs work, providing some energy for the operation of heat pump compressor 201. This expansion also converts the high-pressure carbon dioxide working medium into low-temperature, low-pressure carbon dioxide working medium. In the present invention, the electric motor is coaxial with heat pump compressor 201 and heat pump expander 204. Heat pump expander 204 provides some energy for the operation of heat pump compressor 201, while the remaining energy is provided by the electric motor, which relies on wind farm electricity that is not grid-connected. The low-temperature, low-pressure carbon dioxide, which has completed expansion work in heat pump expander 204, enters heat exchanger 206 through the cold-side inlet. Simultaneously, the refrigerant stored in refrigerant hot tank 205 enters heat exchanger 206 through the hot-side inlet. In heat exchanger 206, the low-temperature, low-pressure carbon dioxide exchanges heat with the refrigerant, lowering the refrigerant's temperature and transferring its cold energy to the refrigerant. The cooled refrigerant flows out of the hot-side outlet of heat exchanger 206 and is stored in refrigerant cold tank 207. The low-pressure carbon dioxide that has completed heat exchange in heat exchanger 206 enters regenerator 203 from the cold-side inlet of regenerator 203, exchanging heat with the high-pressure carbon dioxide entering regenerator 203. It absorbs the heat of the high-pressure carbon dioxide, thereby raising the temperature of the low-pressure carbon dioxide entering heat pump compressor 201 and lowering the temperature of the high-pressure carbon dioxide entering heat pump expander 204. The low-pressure carbon dioxide that has completed heat exchange in regenerator 203 enters heat pump compressor 201 and is compressed to a high-temperature and high-pressure state. Through the above process, the heat pump energy storage subsystem 200 converts the wind farm's ungrid-connected electricity into the thermal energy of the pebbles in the packed bed regenerator 202 and the cold energy of the refrigerant in refrigerant cold tank 207 for storage.

[0035] When the grid is under high load and needs to provide power, the system is in the energy release stage:

[0036] Gate valves V3, V4, V7, V8, V11, and V12 are open, while gate valves V1, V2, V5, V6, V9, and V10 remain closed. Super II compressor 301 compresses the carbon dioxide working medium to a high pressure. The high-pressure carbon dioxide then enters the packed bed regenerator 202, where it is heated by the pebble-shaped heat storage medium. After completing the heat exchange, the high-pressure carbon dioxide working medium enters the molten salt heat exchanger 105 from the cold side inlet. Simultaneously, the high-temperature molten salt heat storage medium stored in the molten salt hot tank 104 enters the molten salt heat exchanger 105 from the hot side inlet. In the molten salt heat exchanger 105, the high-pressure carbon dioxide working medium is further heated by the high-temperature molten salt heat storage medium. After heat exchange with the carbon dioxide working medium, the high-temperature molten salt heat storage medium is converted to a low-temperature molten salt heat storage medium, which is then stored in the molten salt cold tank 103. The carbon dioxide working fluid that has completed heat exchange in the molten salt heat exchanger 105 flows out of the cold side outlet of the molten salt heat exchanger 105 and enters the super-second turbine, where it expands and performs work, driving a generator to generate electricity and supply it to the grid. The carbon dioxide working fluid that has completed work in the super-second turbine still contains a certain amount of heat. Subsequently, the carbon dioxide working fluid enters the cooler 303 from the hot side inlet to heat the working fluid of the transcritical carbon dioxide power cycle energy release subsystem 400. The carbon dioxide working fluid that has completed heat exchange in the cooler 303 flows out of the hot side outlet of the cooler 303 and enters the super-second compressor 301, where it is compressed to a high pressure state. The working fluid of the transcritical carbon dioxide power cycle energy release subsystem 400, heated in the cooler 303, flows out of the cold side outlet of the cooler 303 and enters the trans-second turbine 401, where it expands and performs work, driving a generator to generate electricity and supply it to the grid. The carbon dioxide working fluid that has completed work in the second turbine enters condenser 402. Simultaneously, the refrigerant stored in refrigerant cold tank 207 also enters condenser 402, condensing the carbon dioxide working fluid into a liquid state. The refrigerant that has completed heat exchange in condenser 402 is stored in refrigerant hot tank 205. The condensed liquid carbon dioxide working fluid is then re-entered into cooler 303 from the cold side inlet by working fluid pump 403, where it is heated by the exhaust gas from the supercritical carbon dioxide power cycle turbine.

[0037] Through the above process, in the energy release stage, the supercritical carbon dioxide power cycle energy release subsystem 300 and the transcritical carbon dioxide power cycle energy release subsystem 400 convert the thermal energy stored in the tower solar collector subsystem 100 and the heat pump energy storage subsystem 200 in the energy storage stage and the cold energy stored in the heat pump energy storage subsystem 200 into electrical energy and transmit it to the power grid.

[0038] Example 2

[0039] Reference Figure 1, which is the second embodiment of the present invention. This embodiment is different from the first embodiment in that: the heat pump system thermal energy storage part 20 includes a packed bed heat accumulator 202 connected to the heat pump compressor 201 through a gate valve. This configuration can improve the heat storage efficiency and reduce the complexity of the system.

[0040] Compared to Example 1, the heat pump system reheat unit 21 further includes a regenerator 203 connected to the heat pump system heat energy storage unit 20, the heat pump expander 204, the heat pump system cold energy storage unit 22, and the heat pump compressor 201. The regenerator 203 can recover the heat energy of the working fluid at the outlet of the heat pump system heat energy storage unit 20, thereby improving system efficiency. The integration of the heat pump expander 204 allows the energy released during the expansion process to be recycled and reused, further improving the system's energy utilization rate.

[0041] Compared with Example 1, the heat pump system cold energy storage part 22 further includes a heat exchanger 206 connected to the heat pump expander 204, and a refrigerant hot tank 205 and a refrigerant cold tank 207 connected to the heat exchanger 206 through a gate valve. The refrigerant hot tank 205 is used to store refrigerant to absorb cold energy, and the refrigerant cold tank 207 is used to store the cold energy of the heat pump energy storage system for condensing turbine exhaust, and the heat exchanger 206 is responsible for transferring the cold energy of the heat pump energy storage system to the refrigerant.

[0042] Example 3

[0043] Reference Figure 1 , which is the third embodiment of the present invention. This embodiment differs from the second embodiment in that the orientation of the heliostat field 101 of the tower solar thermal collection subsystem 100 can be adjusted in real time as the sun moves. This dynamic tracking technology can maximize the efficiency of collecting solar radiation and ensure that the receiver 102 is always in the best receiving state.

[0044] Compared with Example 2, further, the medium used in the packed bed regenerator 202 is pebble medium. Pebbles can effectively store and release thermal energy due to their high heat capacity and good thermal stability, and are suitable for high-temperature thermal energy storage applications. Cost-effectiveness and material availability are also taken into consideration.

[0045] Compared with Example 2, further, the working fluid pump 403 has an adjustable flow control device to adapt to different flow requirements. The flow control device can be a variable frequency drive, a regulating valve or other types of regulating systems, which makes it convenient for staff to adjust the flow rate and flow of the working fluid according to actual needs.

[0046] Compared with Example 2, further, the heat exchanger 206 includes multiple parallel heat exchangers to achieve effective management of refrigerant with different flow rates. The design of the parallel heat exchanger provides greater flexibility, allowing the system to independently control each heat exchanger as needed to adapt to different heat loads and operating conditions.

[0047] The remaining structures are the same as those of Example 2.

[0048] It is important to note that the construction and arrangement of the present application shown in a number of different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape, and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, changes in orientation, etc.) without departing substantially from the novel teachings and advantages of the subject matter described in this application. For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature, number, or position of the discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "means plus function" clause is intended to cover the structure described herein that performs the function, and is not only structurally equivalent but also equivalent structures. Other replacements, improvements, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiments without departing from the scope of the present invention. Therefore, the invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0049] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (i.e., those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A carbon dioxide heat pump energy storage system coupled with solar energy utilization, characterized by: include, A tower-type solar thermal collection subsystem (100) comprises a heliostat field (101) and a solar energy storage unit (10) corresponding to the heliostat field (101); A heat pump energy storage subsystem (200) comprises a heat pump compressor (201), a heat pump system heat energy storage unit (20) connected to the heat pump compressor (201) via a gate valve, a heat pump system heat recovery unit (21) connected to the heat pump system heat energy storage unit (20) via a gate valve, a heat pump expander (204) connected to the heat pump system heat recovery unit (21) via a gate valve, and a heat pump system cold energy storage unit (22) connected to the heat pump expander (204) via a gate valve; The electric motor is coaxial with the heat pump compressor (201) and the heat pump expander (204); the heat pump expander (204) provides part of the energy for the operation of the heat pump compressor (201); the remaining energy is provided by the electric motor using the electric energy that the wind farm cannot connect to the grid; A supercritical carbon dioxide power cycle energy release subsystem (300) includes a super-second compressor (301) and a super-second turbine (302) connected to the solar energy storage unit (10), and also includes a cooler (303) arranged between the super-second compressor (301) and the super-second turbine (302); And, a transcritical carbon dioxide power cycle energy release subsystem (400), comprising a trans-turbine (401) connected to the cooler (303), a condenser (402) connected to the trans-turbine (401), and a working fluid pump (403) connected to the condenser (402); The solar energy storage unit (10) includes a receiver (102) corresponding to the heliostat field (101), a molten salt cold tank (103) and a molten salt hot tank (104) connected to the receiver (102) via a gate valve, and a molten salt heat exchanger (105) connected to the molten salt cold tank (103) and the molten salt hot tank (104) via a gate valve; The heat pump system heat energy storage unit (20) includes a packed bed heat accumulator (202) connected to the heat pump compressor (201) via a gate valve; The heat pump system heat recovery unit (21) includes a heat regenerator (203) connected to the heat pump system heat energy storage unit (20), a heat pump expander (204), a heat pump system cold energy storage unit (22), and a heat pump compressor (201); The heat pump system cold energy storage unit (22) includes a heat exchanger (206) connected to the heat pump expander (204), and a refrigerant hot tank (205) and a refrigerant cold tank (207) connected to the heat exchanger (206) via a gate valve.

2. The carbon dioxide heat pump energy storage system coupled with solar energy utilization according to claim 1 is characterized in that: The orientation of the heliostat field (101) of the tower-type solar thermal collection subsystem (100) is adjusted in real time as the sun moves.

3. The carbon dioxide heat pump energy storage system coupled with solar energy utilization according to claim 2, characterized in that: The medium used in the packed bed heat accumulator (202) is a pebble medium.

Images