Recursive method for converting natural heat energy into electric energy by using carbon dioxide

Abstract

The invention discloses a recursive method for converting natural heat energy into electric energy by using carbon dioxide. A carbon dioxide energy storage power plant working in a low-temperature area with the temperature lower than 150 DEG C needs to store a certain amount of water and carbon dioxide, but due to the fact that the construction cost of a storage tank is high, people hope to reduce the storage amount. 2, in addition to the technologies mentioned in two invention patents of DE102017003238 and DE102020000131, the technology of the invention is applied to carry out energy exchange between a recursion process and a power plant environment. In the recursion process, the gasification temperature of the carbon dioxide needs to be controlled below 30 DEG C, and the carbon dioxide can absorb the energy of the environment by applying a mature technology, so that efficient energy conversion can be realized, and the storage capacity is reduced. And 3, by integrating the technology of the invention and the patented technologies of the two inventions, the whole set of more economical and efficient solution for solving the two major problems of climate change and energy shortage can be formed.

Description

Technical Field

[0001] The present invention relates to a recursive cycle process that uses carbon dioxide as a working medium and energy carrier to efficiently convert natural heat energy into electrical energy economically. Background Art

[0002] One can combine and apply two authorized patent technologies (DE102017003238 and DE102020000131 ([1], [2])), which are regarded as the basis for the transfer of natural heat energy in the spatial and temporal dimensions and are called discrete storable and transportable cycle systems, with the German abbreviation DSTK (Diskrete Speicherbare und Transportierbare Kreislaufsysteme). So far, some application scenarios of DSTK require storing a large amount of water or carbon dioxide, especially when without them, it is impossible to provide cheap cooling energy in time for the liquefaction of carbon dioxide in a carbon dioxide energy storage power plant. However, building such storage capacity may require a large amount of financial support. Summary of the Invention

[0003] By applying the technology of the present invention and exchanging heat between the recursive cycle system and its environmental system, the economic burden brought by this weakness can be significantly reduced, thereby greatly improving the economic benefits of applying DSTK technology.

[0004] In the descriptions of the above two patents, the current level of this technology is introduced. The integrated technology formed by combining the technologies mentioned therein with the technology of the present invention is called the carbon dioxide energy storage power generation technology in the low-temperature region, with the German abbreviation Teskon( T echnik für E nergiespeicherung und S stromerzeugung mittels Kohlendioxid im N Tiefstemperaturbereich). The low-temperature region generally refers to the temperature range below 150 °C. The natural heat energy mentioned here refers to the heat energy in the earth's surface layer with a temperature between -60 °C and +60 °C, such as the heat energy existing in water, air or soil. In addition, waste heat is also equally important for Teskon applications.

[0005] Based on the utilization of waste heat or natural heat energy, by applying some mature technical equipment, such as heat pumps, absorption chillers or solar collectors, people can economically and effectively increase or decrease the temperature level of this basic heat energy. Moreover, the electric energy required to operate such technical equipment can also be non-steady-state electric energy such as wind power and photovoltaic power. And by using the long-term storage function of DSTK and other short-term storage technologies, the instability of this wind and photovoltaic power can also be overcome, that is, using this non-steady-state electric energy can produce cold energy below 0°C or heat energy above 20°C and use them in the recursive process of the technology of the present invention, thereby outputting steady-state electric energy. Since the wind and photovoltaic power technical equipment already has good reliability, people only need to consider their usage cost here, and this cost has been reduced to about 0.2 yuan per kilowatt-hour. Brief Description of the Drawings

[0006] Figure 1 is a device system that uses carbon dioxide to convert natural heat energy into electric energy;

[0007] Figure 2 is another device system that uses carbon dioxide to convert natural heat energy into electric energy. Detailed Embodiment

[0008] The application of the technical method of the present invention requires a certain amount and a certain temperature of cold energy and heat energy, and obtaining these cold energy or heat energy should be free or inexpensive. In this context, first use Figure 1 to describe the basic principle of the method; then assume the exemplary starting conditions of the recursive cycle method and conduct specific thermodynamic calculations; finally, give Figure 2 the recursive cycle system shown, and give the example calculation results corresponding to Figure 2 Thereby showing that the heat energy in nature can be efficiently converted into electric energy.

[0009] To describe the process of the method, please consider Figure 1 . Through nodes 1 and 2 shown in the figure, cold energy is supplied to the Figure 1 thermodynamic cycle system shown, that is, the cycle system shown by nodes 3->4->5->6->7->8->3; and through nodes 9 and 10, heat energy is supplied to it. Recursive cycles occur at two node pairs: 1-5 and 2-6. The recursive cycle process will continue until the occurrence of certain thresholds. For example, as long as the recursive cycle still makes economic sense, the recursive cycle can continue, otherwise it will be terminated.

[0010] As is well known, each node in a thermodynamic system has its state value. Some relevant values of such nodes can be expressed by the following vector: (T, P, S, H, M, ·) i, where T represents temperature in °C; P represents pressure in bar; S represents entropy in kJ / (kg·K); H represents enthalpy in kJ / kg; M represents mass flow rate in kg / s; the dot above represents the phase state of the medium, which has three values: g, f, k, where g represents the gaseous state, f represents the liquid state, and k represents the supercritical or sub-supercritical state; the subscript i below represents the node number, Figure 1 or Figure 2 the node numbers shown in start from 1 and go up to 10 or up to 11.

[0011] Note that there is at least one space between two adjacent components of the vector to avoid confusion.

[0012] Example 1:

[0013] (-45, 45, 0.61185, 103.6925, 0.5, f)1

[0014] This means that the state of node 1 has the following values: temperature is -45 °C, pressure is 45 bar, entropy is 0.61185 kJ / (kg·K), enthalpy is 103.6925 kJ / kg, mass flow rate is 0.5 kg / s, and the medium phase state is liquid.

[0015] To simplify the vector representation, sometimes some vector components irrelevant to the calculation process can be omitted. Since the positions of the components in the vector may cause confusion, the corresponding units should be added, or assigned to the corresponding letters with an equal sign.

[0016] Example 2:

[0017] (-45 °C, 45 bar, f)1

[0018] That is, the state of node 1 is liquid, temperature is -45 °C, and pressure is 45 bar.

[0019] Example 3:

[0020] (T = -45, S = 0.61185, 103.6925 kJ / kg, f)1

[0021] This means that the state of node 1 is liquid, temperature is -45 °C, entropy is 0.61185 kJ / (kg·K), and enthalpy is 103.6925 kJ / kg

[0022] To represent the source of the vector component values, sometimes the node number is used as a subscript to supplement the component letter.

[0023] Example 4:

[0024] T1 = -45, which is the temperature component of the state vector of node 1, and its temperature value is equal to -45 °C.

[0025] To indicate the recursion depth of the recursive loop, a corresponding depth subscript is appended to the left of the component letter.

[0026] Example 5:

[0027] 2 P1 represents the pressure at node 1 during the second recursive loop.

[0028] It is also agreed here that the recursion depth of the recursive loop, like the node number, starts from 1.

[0029] As we know, in a single-substance system of thermodynamics, the value of a certain state quantity at a certain node is determined by the values of two other different state quantities at the same point, and this relationship can be represented by function symbols.

[0030] Example 6: S(T, P)

[0031] Each of the three letters S, T, and P can have subscripts or superscripts of nodes or recursive loops.

[0032] In addition, as we also know, one can calculate the thermodynamic state variables of carbon dioxide in the saturated state. Here, one state variable is the function value of another state variable. For example: T(P) or P(T), called the pressure-steam curve. T or P can also have subscripts or superscripts of nodes or recursive loops.

[0033] In the following calculations, these function symbols S(T, P) and T(P) and the subscripts and superscripts can sometimes be omitted by directly giving the relevant numerical values.

[0034] Sometimes, to avoid confusion, all the technical components shown in Figure 1 or Figure 2 also need to have corresponding subscripts in order to distinguish them in different recursive loops.

[0035] Example 7:

[0036] 2 W1 represents the heat exchanger W1 in the second recursive loop.

[0037] So far, we have introduced the necessary terms and symbols for describing the recursive loop process. Next, we will gradually describe this recursive loop process from the principle aspect according to Figure 1 shown as follows:

[0038] 1. The low-temperature cold energy is input into the current thermodynamic cycle system through nodes 1 and 2 on one side of the heat exchanger W1, which can be simply referred to as a cycle, a cycle round, or a recursive loop. The carbon dioxide liquid or other medium fluid flows from node 1 to node 2 on this side (referred to as side A for short), and their vectors are respectively

[0039] (1 T, 1 P, f)1 and 1 T, 1 P, g)2

[0040] 2. On the other side of the heat exchanger W1 (abbreviated as side B), the corresponding flow of carbon dioxide fluid occurs: The carbon dioxide gas flows from node 3 to node 4 on this side, and their vectors are respectively

[0041] ( 1 T, 1 P, g)3 and 1 T, 1 P, f)4

[0042] 1 T4 is usually 1 5 °C higher than 1 T3 is usually 1 T2 is also 5 °C higher, so as to transfer heat through the temperature difference. In the heat exchanger W1, phase changes should occur on both sides. That is, on the side from node 1 to node 2, the phase change is from liquid to gas, and on the other side from node 3 to node 4, the phase change is the opposite. In this way, compared with the energy transfer without phase change, more energy will be transferred by the phase change.

[0043] 3. The CO2 liquid from side B of W1 is pressurized by the carbon dioxide liquid pump P, and its pressure increases, and the state becomes 1 T, 1 P, f)5. Here, by driving the liquid pump P with a small amount of electrical energy, the pressure of the CO2 liquid can be significantly increased.

[0044] 4. The CO2 liquid continues to flow, and the CO2 liquid will vaporize in the recursive cycle R. Therefore, at node 6, the carbon dioxide has become gaseous, and its vector is: 1 T, 1 P, g)6. Due to the vaporization phase change of CO2, a large amount of cold energy is transferred to the recursive cycle R, and this recursive cycle R will be further explained in step 7 below.

[0045] 5. The high-pressure CO2 fluid flows into one side of the heat exchanger W2. Due to the heat transferred from the other side of W2, the temperature of the carbon dioxide increases, and its thermal energy is supplied by the heat source WQ with a certain high temperature. The thermodynamic state of the CO2 fluid becomes supercritical or sub-supercritical at node 7, and its value is: 1 T, 1 P, k)7.

[0046] Now, the carbon dioxide fluid has high pressure and high temperature, and can expand to do mechanical work in the turbine of TG and generate current through the connected generator. Therefore, the state of the CO2 fluid at node 8 is: 1 T,1 P, g)8

[0047] 6. The state is (( 1 T, 1 The carbon dioxide fluid with the state of P, g)8 flows through the heater H and is heated to increase its temperature, usually 5°C higher than the temperature 1 T2, and thus the carbon dioxide fluid returns to the state at node 3.

[0048] 7. The recursive path between node 5 and node 6 is achieved through two pairs of nodes 1 T5 = 2 T1 and 1 T6 = 2 T2, that is, in the next recursive loop, 1 T5 acts as 2 W1's 2 T1, and 1 T6 acts as 2 W1's 2 T2. Thus, it enters the next round of recursive loop, that is, the second round of recursive loop. In this round of recursive loop, there are technical components of the same type as in the previous round, and the same design method as in the previous round, that is, the first round of recursive loop, is adopted. When the next round of recursive loop cannot bring any economic benefits, the recursive loop should terminate. In each round of recursive loop, new technical components of the same type are used, so there will be additional investment and operating costs. Compare these costs with the electrical energy benefits that can be generated in this round of recursive loop. If the benefits are equal to or less than the total costs of this round of recursive loop, this recursive loop system should not be constructed anymore.

[0049] Before presenting the example data of the recursive loop, some advantages of the recursive loop process are described first.

[0050] · Since the carbon dioxide liquid in this loop has been vaporized in the heat exchanger 2 W1 in the next loop, the heat energy that the heat exchanger 1 W2 in this loop still needs to transfer is much less compared with the case without recursive loop. Therefore, supplying a small amount of heat energy can increase the perceived temperature of the carbon dioxide gas. It can be deduced that the heat energy for heating carbon dioxide required for 1 W2 can be saved from the heat source WQ equipment system. Therefore, the heat storage capacity or the transportation cost of the heat energy carrier can be saved.

[0051] · The heater H can economically heat the low-temperature carbon dioxide fluid from TG by using the natural heat energy in the low-temperature region, and thus the next cycle can be achieved.

[0052] · Generally speaking, compared with the electric energy generated by TG, the energy consumed by the liquid pump P is less, but it can increase the pressure of the carbon dioxide liquid several times.

[0053] · Since the cold energy provided in the first round of cycle is reused in subsequent recursive cycles, people can save cold energy. Therefore, the amount of cold energy required for carbon dioxide liquefaction can be reduced, and its cold storage capacity, or the transportation volume of the cold energy carrier, can be significantly decreased.

[0054] · The heat source WQ has a lower requirement for the temperature level. The higher the temperature, the higher the cost required to obtain the thermal energy at this temperature level. Similarly, for the cold source KQ, the lower its temperature, the more complex it is to obtain cold energy.

[0055] Now we provide example data for the recursive cycle process so as to see the specific results and better understand the recursive cycle process. Here it is assumed that the heat source WQ supplies heat with a temperature greater than or equal to 60 °C, and the cold source KQ supplies cold energy with a temperature less than or equal to -45 °C.

[0056] Figure 1 The vector of node 1 in [[]] is set as (-45, 45, 0.6119, 103.69, 0.5, f)1

[0057] Figure 1 The vector of node 2 in [[]] is (T = 10, P = 45, H = 422.95, M = 0.5, g)2

[0058] To simplify the description, it is assumed that the working medium flowing through node 1 and node 2 is carbon dioxide, and the mass flow rate is 0.5 kg / s. Of course, cold energy can also be transferred to the first recursive cycle system through another working medium via the heat exchanger W1.

[0059] In the heat exchanger W1, CO2 gasification occurs during the flow of carbon dioxide from node 1 to node 2. The heat transfer power is 159.63 kW. On the other side of W1, from node 3 to node 4, CO2 gas liquefaction occurs, and its heat transfer power is also 159.63 kW. The vector of node 3 is

[0060] (T = 15, P = 10.05, H = 487.84, M = 0.4257, g)3

[0061] And the vector of node 4 is

[0062] (T = -40, P = 10.05, S = 0.6658, H = 112.90, M = 0.4257, f)4

[0063] The carbon dioxide liquid flows out from the B side of W1 and passes through the carbon dioxide liquid pump P, and its pressure increases. Therefore, the vector of node 5 is

[0064] (T = -38, P = 45, S = 0.67163, H = 117.50, M = 0.4257, f) 5

[0065] The power of the driving liquid pump P is 1.96 kW.

[0066] In the heat exchanger of the next round of recursive loop 2 W1, the carbon dioxide liquid is vaporized, so the vector of node 6 is

[0067] (T = 10, P = 45, H = 422.95, M = 0.4257, g) 6

[0068] It should be noted that the vaporized carbon dioxide can utilize natural heat with a temperature higher than 10 °C. That is to say, this thermal cycle system can absorb heat energy from the environmental system or other cheap heat sources, and its input power is 130.05 kW. Due to the phase change, compared with the heat exchange power for heating the carbon dioxide gas in the subsequent heat exchanger W2, this power is quite large. The heat for heating CO2 in the heat exchanger W2 is supplied by the heat source WQ, with a temperature above 60 °C. Generally speaking, such heat requires a certain effort to obtain. In the heat exchanger W2, the temperature of the CO2 gas rises to 55 °C, and its heat exchange power is 29.78 kW, which is much smaller than the previous 130.05 kW. Ignoring the pressure loss in the carbon dioxide process, we have prepared a sub-supercritical carbon dioxide fluid at a temperature of 55 °C and a pressure of 45 bar, which can do work in the TG and drive the generator to generate electricity. The vector of node 7 is

[0069] (T = 55, P = 45, S = 2.01725, H = 492.9, M = 0.4257, k) 7

[0070] The sub-supercritical carbon dioxide fluid expands and does work in the turbine of the TG, so the vector of node 8 is

[0071] (T = -40, P = 10.05, H = 435.30, S = 2.048, M = 0.4257, g) 8

[0072] The output power of the turbine is 24.52 kW.

[0073] The expanded carbon dioxide fluid is heated by the heater H, and its temperature rises to 15 °C, and node 3 has the vector mentioned above

[0074] (T = 15, P = 10.05, H = 487.84, M = 0.4257, g) 3

[0075] The heat exchange power of the heater H is 22.37 kW. The recursive cycle system can absorb heat with a temperature higher than 15 °C from the environmental system or other low-cost heat sources, so that the recursive cycle can continue to operate.

[0076] Next, we will demonstrate the second round of the recursive cycle. For clarity, we have almost omitted the upper left subscripts of the first round of the recursive cycle so far. In the second round of the recursive cycle, this subscript must be introduced to avoid confusion. For example, the vector symbol in the 3rd node of the first recursive cycle is

[0077] (T = 15, P = 10.05, H = 487.84, M = 0.4257, g)3

[0078] Now the vector should be written as follows:

[0079] ( 1 T = 15, 1 P = 10.05, 1 H = 487.84, 1 M = 0.4257, g)3

[0080] For the second round of the recursive cycle, the heat source 2 WQ is set the same as in the first round. The vector of node 1 in the second round is

[0081] ( 2 T = 1 T5, 2 P = 1 P5, 2 H = 1 H5, 2 M = 1 M5, f)1

[0082] Where: 1 T5 = -38, 1 P5 = 45, 1 H5 = 117.5, 1 M5 = 0.4257

[0083] The vector of the 2nd node in the second round is

[0084] ( 2 T = 1 T6, 2 P = 1 P6, 2 H = 1 H6, 2 M = 1 M6, g)2

[0085] Where: 1 T6 = 10, 1 P6 = 45,1 H6 = 422.95, 1 M6 = 0.4257

[0086] According to the previous calculations, for the heat exchanger 2 the heat exchange power of W1 is 130.05 kW. Now, calculate the vectors of each node in the second round of recursive loop in a similar manner to the first round. The vector of node 3 is

[0087] ( 2 T = 15, 2 P = 12.895, 2 H = 484.47, 2 M = 0.3639, g)3

[0088] The vector of node 4 is

[0089] ( 2 T = -33, 2 P = 12.895, 2 S = 0.7249, 2 H = 127.15, 2 M = 0.3639, f)4

[0090] Coming from 2 the CO2 liquid from W1 flows through the carbon dioxide liquid pump 2 P, and its pressure increases. Therefore, the vector of node 5 is

[0091] ( 2 T = -31, 2 P = 48, 2 S = 0.7293, 2 H = 131.51, 2 M = 0.3639, f)5

[0092] The power of the liquid pump 2 P is 1.59 kW.

[0093] If the current second recursive loop is not the last one, then in the next third recursive loop, the carbon dioxide liquid from 2 P vaporizes in the heat exchanger 3 W1. Therefore, the vector of node 6 is

[0094] ( 2 T = 13, 2 P = 48, 2 H = 440.42, 2 M = 0.3639, g)6

[0095] Here, it should be noted again that the heat exchanger 3The carbon dioxide gasification in W1 can be carried out using natural heat with a temperature level higher than 13°C. That is to say, the current thermodynamic system can absorb heat energy from the surrounding environment system or other low-cost heat sources, and its input power is 112.43 kW. In the subsequent heat exchanger 2 heat the carbon dioxide gas in W2, 2 the heat in W2 is provided by a heat source with a temperature above 60°C 2 WQ, but this kind of heat usually requires a certain amount of investment cost to obtain. In the heat exchanger 2 W2, the temperature of the carbon dioxide fluid rises to 55°C, and the required heat exchange power is 17.95 kW, which is much smaller than the previous 112.43 kW. Ignoring the possible carbon dioxide pressure loss, now we have prepared a sub-supercritical carbon dioxide fluid with a temperature of 55°C and a pressure of 48 bar, which can 2 do work and generate electricity in TG. Therefore, the vector of node 7 is

[0096] ( 2 T = 55, 2 P = 48, 2 H = 489.75, 2 S = 1.9973, 2 M = 0.3639, k)7

[0097] After the sub-supercritical carbon dioxide fluid expands and does work in the 2 turbine of TG, the vector of node 8 is

[0098] ( 2 T = -33, 2 P = 12.895, 2 H = 436.50, 2 S = 2.013, 2 M = 0.3639, g)8

[0099] Its work power is 19.38 kW.

[0100] The expanded carbon dioxide gas is heated by the heater 2 H, and its temperature rises to 15°C. Then node 3 has the vector mentioned above

[0101] ( 2 T = 15, 2 P = 12.895, 2 H = 484.47, 2 M = 0.3639, g)3

[0102] The heat exchange power is 17.46 kW. This system can absorb heat above 15°C from the environment system or other low-cost heat sources, so that the recursive cycle can continue.

[0103] We calculate the recursive loop again, that is, the third round. Then we end the calculation of the recursive loop. For the third recursive loop, the heat source WQ is set the same as in the first round.

[0104] The vector of node 1 in the third recursive loop is

[0105] ( 3 T = 2 T5, 3 P = 2 P5, 3 H = 2 H5, 3 M = 2 M5,f)1

[0106] Where: 2 T5 = -31, 2 P5 = 48, 2 H5 = 131.51, 2 M5 = 0.3639.

[0107] The vector of node 2 in the third recursive loop is

[0108] ( 3 T = 2 T6, 3 P = 2 P6, 3 H = 2 H6, 3 M = 2 M6,g)2

[0109] Where: 2 T6 = 13, 2 P6 = 48, 2 H6 = 440.42, 2 M6 = 0.3639.

[0110] According to the previous calculation, the heat exchange capacity of the heat exchanger 3 W1 is 112.43 kW.

[0111] Now calculate the vectors of other nodes in the third recursive loop in a way similar to the second round. The vector of node 3 is

[0112] ( 3 T = 18, 3 P = 16.29, 3 H = 483.45, 3 M = 0.3290,g)3

[0113] The vector of node 4 is

[0114] (3 T = -26, 3 P = 16.29, 3 S = 0.7832, 3 H = 141.70, 3 M = 0.3290, f)4

[0115] The carbon dioxide liquid flows through the liquid pump 3 P, and its pressure increases. Therefore, the vector of node 5 is

[0116] ( 3 T = -24, 3 P = 53, 3 S = 0.7855, 3 H = 145.81, 3 M = 0.3290, f)5

[0117] Liquid pump 3 The electric power consumed by P is 1.35 kW.

[0118] If the current recursive loop iteration is not the last one, in W1 of the next fourth recursive loop, the carbon dioxide liquid will vaporize in it, and the vector of node 6 is

[0119] ( 3 T = 17, 3 P = 53, 3 H = 423.53, 3 M = 0.3290, g)6

[0120] It should be noted here that the vaporization of carbon dioxide can occur under natural heat at a temperature higher than 17 °C, that is to say, this thermodynamic system can already obtain thermal energy from the environmental system or other cheap heat sources, and its input power is 91.36 kW. In the subsequent heat exchanger 3 W2, heat the carbon dioxide gas, and its heat needs to be supplied by the heat source WQ at a temperature of 60 °C. Obtaining this kind of heat usually requires a certain amount of investment cost. In 3 The W2 heat exchanger, the temperature of the carbon dioxide fluid reaches 55 °C, and its heat exchange power is 19.94 kW, which is much smaller than the previous 91.36 kW. Ignoring the possible pressure loss of carbon dioxide, now a sub-supercritical carbon dioxide fluid at a temperature of 55 °C and a pressure of 53 bar is ready, and it can 3 Do work and generate electricity in TG. Therefore, the vector of node 7 is

[0121] ( 3 T = 55, 3 P = 53, 3 H = 484.14, 3 S = 1.9653, 3M = 0.3290, k)7

[0122] The sub - supercritical carbon dioxide fluid expands and does work in the 3 TG turbine. Therefore, the vector of node 8 is

[0123] ( 3 T = - 26, 3 P = 16.29, 3 H = 437.00, 3 S = 1.978, 3 M = 0.3290, g)8

[0124] The power output of the turbine is 15.51 kW.

[0125] After expansion work, the carbon dioxide fluid passes through the heater 3 H for heating, and its temperature rises to 18 °C. The vector of node 3 is the aforementioned vector

[0126] ( 3 T = 18, 3 P = 16.29, 3 H = 483.45.49, 3 M = 0.3290, g)3

[0127] 3 The heating power of H is 15.28 kW. This system can absorb heat above 18 °C from the environmental system or other low - cost heat sources.

[0128] We have seen that in the possible fourth recursive loop, 4 The heat exchange power in W1 is 91.36 kW. If the total cost of the fourth recursive loop is lower than the power generation revenue of the fourth round, the fourth round can continue. But here we assume that is not the case, so the fourth recursive loop does not start. For this reason, we can set an air heat exchanger with a heat exchange capacity of at least 91.36 kW at the 3 R position in the third recursive loop. The air temperature at this time should be higher than - 24 °C, otherwise a heat source with a temperature higher than - 24 °C must also be prepared.

[0129] Table 1 below provides the recursive loop data from nodes to cycle rounds. For example, the temperature changes of node 1 in three - round cycles are: - 45 °C, - 38 °C, - 31 °C, increasing by 7 °C each round. These changes are mainly determined by the temperature difference required for heat transfer in the heat exchanger W1, and another factor is the influence of the carbon dioxide liquid pump P.

[0130] Table 1: Data from Nodes to Cycle Rounds

[0131] node cycle round T P S H M phase state <![CDATA[Power kW > 1 1 -45 45 0.6119 103.69 0.5 f 2 -38 45 117.50 0.4257 f 3 -31 48 131.51 0.3639 f 2 1 10 45 422.95 0.5 g 159.63 2 10 45 422.95 0.4257 g 130.05 3 13 48 440.42 0.3639 g 112.43 3 1 15 10.05 487.84 0.257 g 2 15 12.895 484.47 0.3639 g 3 18 16.29 483.45 0.3290 g 4 1 -40 10.05 0.6658 112.90 0.4257 f 159.63 2 -33 12.895 0.7249 127.15 0.3639 f 130.05 3 -26 16.29 0.7832 141.70 0.3290 f 112.43 5 1 -38 45 0.67163 117.50 0.4257 f 1.96 2 -31 48 0.7293 131.51 0.3639 f 1.59 3 -24 53 0.7855 145.81 0.3290 f 1,.5 6 1 10 45 422.95 0.4257 g 130.05 2 13 48 440.42 0.3639 g 112.43 3 17 53 423.53 0.3290 g 91.36 7 1 55 45 2.0173 492.90 0.4257 k 29.78 2 55 48 1.9973 489.75 0.3639 k 17.95 3 55 53 1.9653 484.14 0.3290 k 19.94 8 1 -40 10.05 2.048 435.30 0.4257 g 24.52 2 -33 12.895 2.013 436.50 0.3639 g 19.38 3 -26 16.29 1.978 437.00 0.3290 g 15.51 3 1 15 10.05 487.84 0.4257 g 22.37 2 15 12.895 484.47 0.3639 g 17.46 3 18 16.29 483.45 0.3290 g 15.28

[0132] Another sorting is from the recursive loop rounds to the data of the nodes. In the first round of the loop, cold energy is received from the outside through Node 1 and Node 2. In the next loop, cold energy is received from its previous loop through the respective heat exchanger W1.

[0133] Table 2 Data from the loop rounds to the nodes

[0134] cycle round node T P S H M phase state <![CDATA[Power kW > 1 1 -45 45 0.6119 103.69 0.5 f 2 10 45 422.95 0.5 g 159.63 3 15 10.05 487.84 0.4257 g 4 -40 10.05 0.6658 112.90 0.4257 f 159.63 5 -38 45 0.67163 117.50 0.4257 f 1.96 6 10 45 422.95 0.4257 g 130.05 7 55 45 2.0173 492.90 0.4257 k 29.78 8 -40 10.05 2.048 435.30 0.4257 g 24.52 3 15 10.05 487.84 0.4257 g 22.37 2 1 -38 45 117,50 0,4257 f 2 10 45 422.95 0.4257 g 130.05 3 15 12.895 484.47 0.3639 g 4 -33 12.895 0.7249 127.15 0.3639 f 130.05 5 -31 48 0.7293 131.51 0.3639 f 1.59 6 13 48 440.42 0.3639 g 112.43 7 55 48 1.9973 489.75 0.3639 k 17.95 8 -33 12.895 2.013 436.50 0.3639 g 19.38 3 15 12.895 484.47 0.3639 g 17.46 3 1 -31 48 131.51 0.3639 f 2 13 48 440.42 0.3639 g 112.43 3 18 16.29 483.45 0.3290 g 4 -26 16.29 0.7832 141.70 0.3290 f 112.43 5 -24 53 0.7855 145.81 0.3290 f 1.35 6 17 53 423.53 0.3290 g 91.36 7 55 53 1.9653 484.14 0.3290 k 19.94 8 -26 16.29 1.978 437 0.3290 g 15.51 3 18 16.29 483.45 0.3290 g 15.28

[0135] In the above example, the initial temperature of the second round of the recursive loop is 7 °C higher than the previous round, and the initial pressure also increases monotonically. The mass flow rate of each recursive loop will decrease, and the output power of each round will thus strictly monotonically decrease. The output power of the third round of the recursive loop is only 15.51 kW, and the mass flow rate is 0.3290 kg / s.

[0136] Now, the key points regarding the recursive loop can be given as follows:

[0137] 1. By increasing the mass flow rate of the first round of the loop by 0.5 kg / s, TG can do more mechanical work and generate more electrical energy, but more cold energy needs to be provided.

[0138] 2. The total power required for the liquid pumps P in the three recursive loops is 4.90 kW, and the total mechanical work done by the three turbines is 59.41 kW. In comparison, this ratio is 8.25%.

[0139] 3. The total heat exchange power required from Node 6 to Node 7 in the heat exchanger W2 is 67.67 kW. Compared with the mechanical power output of 59.41 kW, its efficiency is 87.79%.

[0140] 4. The total heat exchange power from Node 8 to Node 3 is 55.11 kW, and the total heat exchange power required from Node 5 to Node 6 is 339.84 kW. The two together amount to a heat power of 394.95 kW. Since its temperature level is within the ambient temperature range and most of the heat below 20 °C is free of charge, it can be almost ignored.

[0141] 5. In the first round of the recursive loop, the cooling power from Node 3 to Node 4 is 159.63 kW; in the subsequent recursive loop rounds, no additional cooling power from the outside is required. The ratio of the mechanical output power of 59.41 kW to this refrigeration power is 37.22%.

[0142] 6. The refrigeration power is 159.63 kW plus the heating power of 67.67 kW, so the total required power is 227.30 kW, while the total output power is 59.41 kW. Therefore, the total efficiency is 26.14%. This high efficiency is largely due to the advantages of the recursive cycle. If such thermal or cold energy can be obtained at little or no cost, the economic effect will be even better.

[0143] 7. The heat source with a temperature level of 60 °C can be linked to the ambient temperature. For example, in summer, the ambient temperature is 30 °C, so only the heat required to raise the temperature from 30 °C to 60 °C needs to be supplied. In winter, it can be assumed that the geothermal or water temperature is 5 °C. Similarly, the cold source at -45 °C can also be connected to the ambient temperature. If the ambient temperature in winter is -30 °C, then only the temperature needs to be lowered from -30 °C to -45 °C. Moreover, in some application scenarios, heat or cold can be supplied for free during operation, such as the heat collected by solar collectors or the cold generated during the vaporization of liquefied natural gas.

[0144] In the above recursive cycle, we can see that the temperature increases with each subsequent recursive cycle. One may wonder whether this temperature increase can be prevented. For this purpose, we place a cooler between the liquid pump P and the recursive cycle R, as Figure 2 shown. Thus, Figure 2 the temperature at node 6 in

[0145] can be cooled to the temperature at node 1. Under this condition, we again use the example data mentioned above to calculate the state data of each node in the recursive cycle. The calculation results can be seen in the following two tables: Table 3 and Table 4.

[0146] Table 3: Data from cycle rounds to nodes with a cooler

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[0149] Table 4: Data from nodes to cycle rounds with a cooler

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[0152] By installing the cooler K, we obtain 3.77 kW more output power than before, but we need to pay an additional 10.89 kW of cooling power. Since the third round is the last recursive cycle, the cooler 3 K is no longer needed. Although the mass flow rate decreases with each recursive cycle, just as in the case without installing the cooler, the temperature and pressure at the inlet and outlet of the technical components remain unchanged in each recursive cycle.

[0153] In the above two cases with and without a cooler, we assume that the heat source WQ and the cold source KQ have the same initial conditions, and the temperature levels are set as 60°C for the heat source and -45°C for the cold source respectively. Based on this, the recursive cycle comparison calculations with and without a cooler are carried out. Similarly, we can also perform calculations and operations for other initial conditions. For example, the temperature of the cold source KQ can be set as: -30°C, -20°C, -10°C, -5°C, 0°C. Until a certain cold source temperature level is reached, there will be no economic benefits or there will not be enough enthalpy difference to drive the turbine. A similar consideration can also be made for the temperature level of the heat source WQ.

[0154] There can be various possible combinations of the temperature of the heat source WQ and the temperature of the cold source KQ. For example, in the above example, the inlet state of the turbine can be changed. The inlet temperature can be set as 30°C and the inlet pressure can be set as 30 bar, while its outlet state remains unchanged. Based on this, the corresponding calculations can be carried out similarly. However, the optimal combination of the initial conditions of WQ and KQ to be set locally in the carbon dioxide energy storage power plant can only be determined according to the local specific conditions. For example, the temperature level throughout the year, the availability of water resources, industrial waste heat, wasteland such as desert areas, and many other local conditions need to be comprehensively considered by people.

[0155] To sum up, we can say that due to the recursive cycle, on the one hand, much less WQ heat energy is required to heat carbon dioxide in the heat exchanger W2, because the carbon dioxide liquid in the current recursive cycle is first vaporized by using the natural heat energy of the next recursive cycle in W1, and then only the sensible heat for heating the carbon dioxide gas stream needs to be added in W2. Therefore, the heat energy or heat storage required by the WQ system is much smaller than that in the case without a recursive cycle; on the other hand, since the cold energy supplied in the first cycle is reused in subsequent cycles, a large amount of cold energy is saved, which is usually supplied from the outside for liquefying carbon dioxide gas. Therefore, compared with the case without a recursive cycle, the amount of cold energy or cold storage to be supplied in the KQ equipment system is much smaller. In addition, if the ambient temperature is high enough or low enough, the ambient heat source or ambient cold source can also be used as the heat source WQ or the cold source KQ. Therefore, the new thermodynamic system with a recursive cycle opens a door to dynamically exchange energy with the environment and convert it into electrical energy. This is different from a coal-fired power plant, which releases most of the heat obtained from the initial energy into the environment and does not absorb heat from the environment again. Therefore, by applying the technology of the present invention, the two major problems of climate change and energy shortage can be solved in a timely, economic and effective manner before the occurrence of climate disasters.

[0156] List of reference symbols

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[0159] Printed document

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Claims

1. A recursive method for converting natural heat energy into electric energy using carbon dioxide, characterized in that the method is carried out on a device system including a heat exchanger W1, a liquid pump P, a heat exchanger W2, a thermo-dynamic engine TG with a generator, a heating device H, a cold source KQ, a heat source WQ, and a recursion R representing a new cycle system: 1.1 A heat exchanger W1: 1.1.1 One side of W1, i.e., the side from node 1 to node 2, is called side A. On this side, cold energy is present in the flow of the fluid medium from node 1 to node 2, and the temperature of node 1 is less than or equal to 0 °C; 1.1.2 The other side of W1, i.e., the side from node 3 to node 4, is called side B. The cold energy presented on side A is absorbed by the CO2 fluid flow on side B, that is, the temperature of node 4 or node 3 is higher than that of node 1 or node 2 respectively; 1.1.3 On side B, a phase change from gaseous to liquid occurs during the flow of the CO2 fluid from node 3 to node 4; 1.1.4 On side A, a phase change from liquid to gas must occur during the flow of the medium from node 1 to node 2. If the medium on side A is carbon dioxide, this phase change must occur; 1.1.5 Node 1 is a node between the cold source KQ and the heat exchanger W1 when the medium flows from the cold source KQ to the adjacent heat exchanger W1; Node 2 is a node between the cold source KQ and the heat exchanger W1 when the medium flows from the heat exchanger W1 to the adjacent cold source KQ; Node 3 is a node between the heating device H and the heat exchanger W1 when the medium flows from the heating device H to the adjacent heat exchanger W1; Node 4 is a node between the heat exchanger W1 and the liquid pump P when the medium flows from the heat exchanger W1 to the adjacent liquid pump P; 1.2 A liquid pump P for increasing the pressure of the CO2 liquid flowing out of side B of the heat exchanger W1; 1.3 A heat exchanger W2: 1.3.1 One side of W2, i.e., the side from node 9 to node 10, is called side C. On this side, heat energy is provided during the flow of a fluid medium from node 9 to node 10, and the temperature at node 9 is higher than 20 °C; 1.3.2 The other side of W2, i.e., the side from node 6 to node 7, is called side D. On side D, the heat energy provided on side C is absorbed by the flowing CO2 fluid, and its temperature at node 6 or node 7 is lower than that at node 10 or node 9 respectively; 1.3.3 Node 6 is a node between the recursion R and the heat exchanger W2 when the medium flows from the recursion R to the adjacent heat exchanger W2; Node 7 is a node between the heat exchanger W2 and the thermo-motor TG with a generator when the medium flows from the heat exchanger W2 to the adjacent thermo-motor TG with a generator; Node 9 is a node between the heat source WQ and the heat exchanger W2 when the medium flows from the heat source WQ to the adjacent heat exchanger W2; Node 10 is a node between the heat source WQ and the heat exchanger W2 when the medium flows from the heat exchanger W2 to the adjacent heat source WQ; 1.4 A thermo-motor TG with a generator, in which carbon dioxide fluid expands to do work and drives the generator to generate electricity; 1.5 A heating device H, by using which the temperature of the expanded CO2 fluid is heated to the temperature at Node 3, thus closing the flow cycle of the CO2 fluid; 1.6 The recursive cycle for repeating the above cycle: The recursion proceeds in the following way, that is, Node 5 or Node 6 of the current cycle is respectively regarded as Node 1 or Node 2 of the heat exchanger W1 in the next recursive cycle, and this recursive cycle is designed and constructed in the same way as the current cycle; The CO2 liquid flow from the current liquid pump P undergoes a phase change to become a CO2 gas flow at its current pressure, and this phase change occurs in W1 of the recursive cycle, that is, during the flow of carbon dioxide from Node 1 to Node 2; As a result, the cold energy generated when the carbon dioxide liquid vaporizes on the A side is transferred from the current cycle to the next cycle for the liquefaction of the carbon dioxide gas on the B side; The heat exchanger W1 for transferring this CO2 cold energy is herein called the recursive heat exchanger, and the recursive cycle is numbered starting from 1, and the current recursive cycle is called the first recursive cycle; To clarify the depth of the recursive cycle, the recursive cycle is also called the recursive round; The technical components included in a recursive cycle constitute a thermodynamic cycle system; With this equipment system, the following method can be effectively described, 1.7 For the transfer of cold energy from the natural environment to the circulation system and the absorption of natural heat energy by the circulation system, phase changes occur on both sides of the recursive heat exchanger W1, and the phase changes occur within the temperature range of -55°C to 30°C. 1.8 To achieve the recursive function and high efficiency of each recursive circulation system, within the temperature range of -55°C to 150°C, the temperature and pressure levels of each node of the system should be selected through thermodynamic calculations to make them match each other. 1.9 Compared with the case without a recursive cycle, the amount of heat to be transferred from the heat source WQ to the recursive cycle through the corresponding heat exchanger W2 is much less. These heats are used to increase the sensed temperature of the carbon dioxide gas flow flowing out of the corresponding heat exchanger W1. Therefore, the amount of heat that the heat source system needs to provide is much smaller, and the corresponding heat storage capacity is also much smaller. 1.10 The cold energy provided by nodes 1 and 2 of the heat exchanger W1 in the first recursive round can be used for the liquefaction of CO2 gas in multiple circulation systems due to the subsequent multiple cold energy transfers of the corresponding heat exchanger W1. Thus, a large amount of cold energy can be saved. Therefore, compared with the case without a recursive cycle, the amount of cold that the cold source system of the recursive cycle needs to provide is much smaller, and the corresponding cold storage capacity is also much smaller. 1.11 The heating device H uses environmental heat, waste heat, or the heat of the heat source WQ to heat the CO2 fluid expanded in the TG heat engine to the temperature level of the current recursive cycle at node 3, thereby absorbing this heat into the circulation system to enable the next recursive cycle. 1.12 The pressure of the CO2 liquid flowing out of the heat exchanger W1 increases many times after being pressurized by the CO2 liquid pump P. Moreover, the electrical energy required to drive the liquid pump P is much less than the electrical energy generated by the TG in the current recursive cycle.

2. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that, If the total cost of the next round of recursive circulation system is higher than the revenue it can obtain from power generation, then the current recursive round becomes the last round of recursive circulation.

3. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, wherein In each round of recursive circulation, a cooler K is configured after the liquid pump P but before the next recursive cycle R. It reduces the temperature level of the CO2 liquid flow flowing out of the liquid pump P to the same temperature as node 1 on the A side of W1 before the liquid pump P. The coolers K of all recursive circulations are connected to the corresponding cooling sources. In this way, each technical component can have the same inlet and outlet states in all recursive circulations, but the mass flow rate of carbon dioxide in each recursive circulation will be different. Therefore, technical components with good load performance should be used, and among them, the technical component is a turbine to bring higher economic benefits.

4. The recursive method for converting natural heat energy into electric energy by using carbon dioxide according to claim 1, characterized in that, The provision of thermal energy or cold energy to the heat source WQ or the cold source KQ can be achieved through natural heat energy or natural cold energy, or the storage and transportation of heat carriers or cold carriers; in terms of the cold source KQ, using appropriate storage technologies, the deep cold energy produced by using wind power, photovoltaic power, or grid surplus power and equal to or lower than 0°C is stored for a long time. Here, water or carbon dioxide can be used as the storage medium, and the cold energy stored in this way is used as the cold energy of the cold source KQ of the recursive cycle.

5. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that, All recursive cycle systems can be connected to the same heat source WQ to supply them with heat, while the cold energy power provided by the cold source KQ is provided once in the first recursive cycle and can be used multiple times in subsequent recursive cycle rounds.

6. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that, The temperature of the heat source WQ is set to be equal to or greater than 20°C, which can be achieved by: 6.1 Use water as a heat carrier, first heated with natural heat, then further heated with different types of heat to the desired temperature level; 6.2 Use solar thermal technology to provide heating; 6.3 Utilize industrial waste heat; 6.4 Providing heat by burning carbon dioxide neutral fuels such as straw, shredded branches and waste wood; 6.5 Use wind power, photovoltaic power or surplus power from the power grid to drive heat pumps to produce heat.

7. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that the temperature of the cold source KQ is set equal to or less than 0°C, which can be achieved by: 7.1 Use carbon dioxide as the cold energy working medium, first use natural cold energy to cool it, and then use different types of cold energy to further cool it, especially using deep cold energy produced by wind power, photovoltaic power or grid surplus power to further cool the working medium to the required cold source temperature; 7.2 Using the heat energy and natural cold energy as described in claim 6 and wind power, photovoltaic power or grid surplus power to drive an absorption refrigeration system for refrigeration; 7.3 Using a combination of compression and absorption refrigeration systems, using natural heat or waste heat and the thermal energy mentioned in claim 6, as well as wind power, photovoltaic power or grid surplus power for refrigeration; 7.4 Use existing storage technology to store large amounts of water ice or snow in winter, and use the melting cold energy of snow or water ice as basic cold energy to cool carbon dioxide in summer or when needed, and use the deep cold energy produced by wind power, photovoltaic power or surplus power from the power grid to cool CO2 to the required temperature level below 0°C.

8. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that, The heat pump driven by wind power, photovoltaic power or surplus power from the power grid obtains heat or cold, which is used for step-by-step heating or cooling to reach the desired temperature level of the heat source WQ or the cold source KQ.

9. The recursive method for converting natural heat energy into electrical energy using carbon dioxide according to claim 1, characterized in that, The heat energy released when the working fluid of the thermal power plant is condensed is used as the heat source WQ of the recursive cycle, or this heat energy is used as the basic heat energy, and then mature technology is used to make WQ reach the required temperature level; or the deep cold energy generated by LNG liquefied natural gas during gasification is used as the cold energy of the cold source KQ of the recursive cycle system.

10. An apparatus system for converting natural heat energy into electric energy by using carbon dioxide as a working medium and an energy carrier, characterized in that, The device system is configured according to the method according to any one of claims 1 to 9 and is used for energy conversion using carbon dioxide.

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