RU2390079C2 - Method for special extraction of electric energy from all types of electrochemical sources of current with help of frequency pulses and its application in sources of power supply - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: current is extracted by frequency pulses provided that specific impedance of each anode of elements in electrochemical sources of current makes not more than 1.87 Ohm·cm². Source of electric power supply is used for method of special frequency extraction of electric energy with application of anode of electrochemical source elements with specific impedance of not more than 1.87 Ohm·cm², comprising electrochemical source of current filled with solution of electrolyte and DC-DC converter, specified by the fact that DC-DC converter comprises transformer, primary circuit of which consists of electrochemical source of current, parallel circuit (shunt) and switching element with control device, and secondary circuit consists of inductive accumulator of energy, capacitor-accumulator and consumer.

EFFECT: compact and light source of electric power supply with required power and capacity on the basis of various electrochemical elements, improved characteristics of power and increased current capacitance.

9 cl, 1 tbl, 4 ex

Description

The use of electrochemical cells for the production of power supplies is widely known. In particular, for portable power supplies, air-metal elements that use metal anodes, gas diffusion cathodes, and an electrolyte solution are widely used. Examples of anode metal are magnesium, zinc and aluminum. As an electrolyte solution, we are talking mainly about aqueous alkaline solutions or sodium chloride solutions.

For the mobile use of such power sources, the weight and size of the power sources and their consumables play an important role. Since the required power characteristics of power sources are set before application, a compact design with low weight is achieved only by optimizing the efficiency of power sources. Factors that limit the performance of electrochemical cells include, among others, the formation of reaction products, insufficient gas diffusion, and insufficient surface activity. For this reason, various studies have so far been conducted to improve portable power sources by changing the design and chemical composition of electrode materials.

US 6127061 describes the improvement of the specific power of air-metal elements using a special air cathode containing a catalytic layer made of a mixture of carbon particles, hydrophobic particles, metal hydroxide and material from particles with a large surface. An electrically conductive structure is applied to it, on which, in turn, an air-permeable and waterproof layer is applied.

US Pat. No. 5,004,654 discloses an aluminum-air cell whose anode material is doped with magnesium and / or calcium, and tin is present in the electrolyte and / or anode material. US Pat. No. 5,360,680 describes an ergonomic design of air-metal elements as mechanically rechargeable power sources, as well as various anode materials, in particular activated zinc in suspension. Particular attention is paid to the use in electric vehicles and the characteristics required in connection with this are high current density, high battery capacity and high maximum power.

Patent EP 1843418 A1 describes an electrochemical voltage / power supply, in particular a fuel cell or a battery in which seawater and / or an alkali solution of an anode suitable for use in an electrochemical air-metal cell and a gas diffusion or air cathode are used as an electrolyte, having at least one hydrophobic layer. In this case, the battery case has a space bounded by one or more hydraulically impermeable partitions, into which air or oxygen is supplied through at least one opening. At least one of the hydraulically impervious partitions inside the battery is formed by a cathode or a hydrophobic layer of the cathode. The intermediate space is at least partially filled with an electrolyte, in particular seawater, an aqueous salt solution or alkali solutions.

The invention presented in claim 1 is based on the problem of improving the characteristics of electric power and capacity of a power source for a given design of the electrochemical current source used in it.

The invention is illustrated by drawings, where figure 1 shows a power source associated with a consumer; figure 2 is an equivalent circuit of the resistance of the anode; figure 3 - dependence of resistivity on current density in constant current mode; figure 4 - typical curves of the differential capacitance of metals.

The problem of improving the characteristics of the electric power and capacity of the power source for a given design of the electrochemical current source used in it is solved by the method of selecting current from the electrochemical current source according to claim 1, which describes a method of selecting current from all types of electrochemical current sources, characterized in that that the current is selected due to the frequency pulses, provided that the specific impedance of each anode of the electrochemical elements is It does not exceed 1.87 Ohm · cm ² . This method serves as the basis for determining the optimal parameters for circuit components. Optimization of a specific power source occurs according to one or more criteria for solving specific consumer problems. For example, the optimization of a DC-DC converter for an air-metal element is carried out according to the consumption of the anode metal, provided that the output power of the power source is not less than the installed power. By changing the frequency of the pulses of the RC generator in the control device using an auxiliary resistor (resistor with variable resistance), the dependences of the anode flow rate (in grams per Wh) and the maximum output power on the pulse frequency are experimentally constructed. Both graphs show the frequency at which the flow rate of the metal anode is minimal, provided that the maximum output power of the current source is not lower than the set value. Further, the design parameters of a planar transformer, inductor, etc. are optimized at the obtained frequency.

Claim 2 describes the generation of frequency pulses through a switching element with a control device whose advantage is a technically simple design, as well as providing specific impedance according to claim 1.

Claim 3 describes a power source for implementing the method according to claims 1 and 2, comprising an electrochemical current source (1) filled with an electrolyte and a direct current converter, characterized in that the direct current converter has a transformer (4) whose primary current circuit consists of an electrochemical current source (1), a parallel circuit (shunt) (2) and a switching element with a control device (3), and the secondary circuit consists of an inductive storage device (5), a storage capacitor (6) and a consumer body (7).

Due to the design of the power source according to the invention (Fig. 1), which works on the principle according to items 1 and 2, an improvement in the power characteristic is achieved for all types of electrochemical current sources. In most species, capacity increases further. This is achieved by optimizing the frequency pulse generated by the switching element with the control device (3) from the electrochemical element (1) to the transformer (4), followed by the accumulation of energy in the drive (5) and its transmission to the consumer (7).

Thus, due to the invention, a more compact and lightweight power source of the required power and capacity based on various electrochemical current sources is realized.

Particular advantages of inventions are reflected in the following paragraphs.

Claim 4 illustrates an optimized application of a switching element with a control device capable of delivering specific frequency pulses to a transformer. An example of this node in a DC-DC converter is described below: a switching element may be a group of transistors. The control device itself can consist, among other things, of a controller (microcircuit) with the necessary adjustments, a start-up circuit, a feedback system that regulates pulse and pause times within a period depending on the load power, microcircuits to reduce losses and buffer circuits to reduce the switching time of the above transistors.

Claim 5 describes the preferred use of a planar transformer as a transformer in a DC / DC converter. Advantages result from the following specific properties of a planar transformer:

- improved mutual induction in a planar transformer increases the efficiency of the DC-DC converter;

- the overall dimensions of the DC-DC converter when using a planar transformer is significantly smaller;

- serial production of a planar transformer for a given DC-DC converter is more simple and technologically more reliable than conventional types.

In paragraph 6 of the claims, advantageous parameters are presented for optimal coordination of structural elements of the current extraction circuit with an electrochemical current source.

The performance of the electrochemical current source, especially suitable for portable power sources, is the metal-air element presented in paragraph 7 of the claims, which provides separate storage of the electrolyte from the battery and delivery to the place of operation.

Another advantageous development of the invention is the use of magnesium as an anode material as described in claim 8, which provides lower weight with good power characteristics of the electrochemical cell.

The type of cell with sodium chloride as an electrolyte specified in claim 9 of the claims has a decisive advantage in that the end user will have to handle non-hazardous consumables and not alkaline solutions that require special precautions. In addition, the disposal of waste products in this case is environmentally friendly.

An example of the construction of the invention is shown in figure 1, the principle of which is described below in more detail. The necessary technical result of the improved electrical characteristics of the power source is achieved through the use of an electrochemical current source (1), which is connected to a planar transformer (4) through a switching element with a control device (3). In addition, a parallel circuit (shunt) (2) with a capacitor CSh is connected to the electrochemical current source. The secondary winding of the planar transformer (4) is connected to the inductive storage (5), the storage capacitor (6) and the load resistance (consumer) (7).

The power source operates as follows. When the contact is closed by the control device (3), a current flows, consisting of the sum of the current of the electrochemical current source (1) and the current of the parallel circuit (2) of the capacitance CSh. Energy is collected in the inductor (5) and flows through the capacitor-drive (6) to the consumer (7). The time of the disconnected state is determined by the minimum time of transfer of energy stored in the inductive storage (5) to the consumer (7). The maximum power transmission efficiency is achieved by reducing the input resistance of the current converter below 1 mOM.

For example, a metal-air element with a magnesium anode, a gas diffusion cathode, and an electrolyte from an aqueous solution of sodium chloride serves as an electrochemical current source. The internal resistance R of the electrochemical cell is the sum of the resistances of the anode, cathode, and electrolyte (R = R _A + Rк + Re), moreover, the resistance of the anode can be simplified as a circuit according to FIG. 2 (Re = electrolyte resistance, R _D = double layer specific resistance , C _{D, s} = specific differential capacity of the double layer).

Below we study the anode component of the total internal resistance of the electrochemical current source in two functional forms: constant current mode and frequency energy selection mode.

In the constant current mode of the electrochemical cell, the resistance of the double electric layer R _D determines the total resistance R _A. The component R _D decreases with increasing current density due to an increase in the concentration of reaction elements in the double electric layer and a change in the activation energy caused by a potential jump in the dense part of the double layer. Figure 3 shows the dependence of the resistivity R _D on the current density.

In the frequency selection mode, the anode resistance Ra is determined by the impedance

R = 1 / 2π · C · f,

C = differential capacity of the double layer

f = frequency.

The capacity of the double electric current in this case depends on the potential of the anode.

Figure 4 shows typical curves of the differential capacitances of various metals in a 0.1 M solution (1 = Hg, 2 = Bi, 3 = Pb, 4 = Sn, 5 = Cd, 6 = In, 7 = In + Ga, 8 = Ga) and C ₅ H ₁₁ OH in the background with 0.1 N solutions of surface inactive electrolytes (Frumkin AN "Zero-charge potentials". Nauka, 1979, 1982).

In the range of negative potential of surface inactive electrolytes, the value of the differential capacitance of the double electric layer for all metals is 17 μF / cm ² . That is, under a certain mode of energy release frequency, the total resistance of the anode can be reduced so that the internal resistance of the electrochemical cell approaches the resistance of the electrolyte. At a frequency of about 100 kHz, the specific impedance of the anode reaches 0.09 Ohm · cm ² . The specific resistance of the electrolyte at an interelectrode distance of 0.5 cm and an operating temperature of 60-70 ° C is 2.5-3 Ohm · cm ² . The specific resistance of modern diffusion cathodes at the same temperature is 0.8-1.0 Ohm · cm ² . Thus, for the total internal resistance of the electrochemical cell in the frequency mode of 100 kHz (in the case of maximum values for Re and Rк), a value of about 4.1 Ohm · cm ^{2 is} obtained, and Ra forms approximately 2.5% of the total internal resistance.

In the constant current mode of the electrochemical cell, the Ra component at a current density of 50-100 mA / cm ² , which is practiced, is 6 Ohm · cm ² (see FIG. 3). Accordingly, the total specific internal resistance reaches about 10 Ohm · cm ² , which is 2.5 times higher than in the frequency mode. Ra forms about 60% of the total resistance.

The increase in power compared to the direct current mode of energy release is determined by the minimum value of the intervals between pulses, which is limited by the time of transmission of energy stored in the storage element to the consumer. A parallel circuit with capacities from CSh = 0.5 · (CD, s · S) to 5 · (CD, s · S) (where S = anode area and CD, s = specific differential capacitance of the anode) is selected so that for disconnecting the electrochemical current source from the converter, the anode potential would not decrease more into a negative one, since the specific capacitance at higher negative potential values is higher, especially during the adsorption of organic substances (see Fig. 4).

As a practical example of the above embodiment, a metal-air element was used, whose magnesium anode had an area of 280 cm ² and a gas diffusion cathode - 240 cm ² . The interelectrode distance was 0.5 cm. An aqueous solution of sodium chloride served as the electrolyte. The metal-air element had an open circuit voltage of 1.74 V. A converter was made including a shunt capacitance C _w = 10500 μF, a key element with a control unit (switching element with a control device), a planar transformer with a storage element and a storage capacitor in the secondary circuit. The power supply, consisting of the above element and the converter, provided an output voltage of 12 V. The input resistance of the converter was 1 mOhm. The element in constant current mode gave a maximum power of 42 W at a voltage of 0.84 V on it at a temperature of 50 ° C. The current density was 197 mA / cm ² . After 40 minutes of operation, the voltage on the element decreased to 0.75 V, after which operation was stopped, since the interelectrode space was filled with reaction products. In the constant current mode of operation of the element, the internal resistance was R _ext = 18 mOhm, current = 50 A.

After working in constant current mode, a converter was connected to the element. The converter output had an output voltage of 12.05 V, a load current of 3.5 A and a power of 41.2 watts. The converter was tested before the experiment: the efficiency at an input voltage of 0.9 V and power from 45-60 W was 0.8. Losses in the converter amounted to 11.5 watts. Losses in the connecting wires were 1.5 watts. Consequently, ≈54.2 W was applied to the input of the converter. The current element in this case was 58 A. The current voltage - 0.93 V. Based ΣR _corolla element was 13 milliohms. According to the ever-current-mode element amount ΣR _ext = 18 milliohms. Thus, the decrease in resistance was 5 mOhm.

Next, the converter was tuned to a frequency of 77000 Hz. The internal resistance of the element decreased insignificantly - from 13 MΩ to 12.5 MΩ, however, the metal consumption decreased by almost 10%. When operating in the 27 kHz mode, the flow rate was 1.62 A · h / g. When operating in the 77 kHz mode, the flow rate was 1.78 A · h / g. The voltage on the element during operation in the frequency sampling modes did not decrease, and the interelectrode space was not clogged by the reaction products.

Comparative analysis.

The advantages achieved using the above technology are manifested when comparing the prototype “akwa MB 12/40”, developed using the method according to this application with the products manufactured by MVIT, Moscow, Russia on a commercial basis, the products “MVIT 4-800 PS” and “MVIT 2- 400 PS ".

Currently, the applicant has prepared mass production of autonomous, environmentally friendly, compact, salt water-powered power sources using the invention.

a) Maximum power characteristic and dimensions.

Comparison of the maximum power characteristics shows that the power source created using the invention in its power corresponds to "MVIT 4-800 PS". At the same time, the dimensions of MVIT exceed the dimensions of akwa by more than four times. Weight comparison provides akwa with similar benefits. Dry-charged weight (storage and transportation) of MVIT is more than five times greater, operational weight is more than four times that of akwa,

b) Power (capacity) of the spare cartridge

Comparison of the spare cartridge power shows that the “akwa MB 12/40” power of 480 W · h exceeds the power of “MVIT 2-400 PS” by 80 Wh At the same time, the akwa replacement cartridge consists of only two anodes with a weight of 0.338 kg, while the MVIT cartridge consists of 4 anodes, with a total weight of 0.480 kg. This means that the efficiency of metal use is at least 1.7 times greater.

The akwa replacement cartridge provides, among other things, the following applications:

- power supply of an incandescent lamp (energy-saving) (12 V, 12 W) for up to 40 hours

- TV power supply (12 V) for up to 25 hours

- power supply of the traveling refrigerator (35 W) for up to 40 hours

- up to 7 laptop charges (4800 mAh)

- Up to 25 charges of a cell phone, digital camera, walkie-talkies, GPS receivers, radio devices and portable CD / DVD players;

- Charging the car battery (55 Ah).

The following table compares the characteristics of various power supplies.

Table MVIT 4-800 PS AQUA ^® MB 12/40 MVIT 2-400 PS Rated voltage [V] 12 12 12 Max. Power, W] 40 40 21 Rated power per cartridge, [W · h] 800 480 400 Min ambient temperature [° C] -twenty -25 -twenty Dry weight, [kg] 5,4 one 3 Weight in operation, [kg] Max. 11,4 Max. 2.6 Max. 6 Weight of one spare cartridge, [kg] 0.96 0.338 0.48 Dimensions (L / W / H), [mm] 250/420/220 190/100/225 250/230/220 The concentration of salt water, [g / l] 100-150 Dry Shelf Life min 10 years Guaranteed Service Life min 3000 hours

Claims (9)

1. A method of special frequency selection of electrical energy from all types of electrochemical current sources, characterized in that the current is selected by frequency pulses, provided that the specific impedance of each anode of the elements of electrochemical current sources is not more than 1.87 Ohm · cm ² . 2. The method according to claim 1, characterized in that the frequency pulses are generated by a switching element with a control device. 3. A power source for implementing a method of special frequency selection of electrical energy from all types of electrochemical current sources, in which current is sampled by frequency pulses, provided that the specific impedance of each anode of the elements of electrochemical current sources is not more than 1.87 Ohm · cm ² containing an electrochemical current source filled with electrolyte (1) and a DC-DC converter, characterized in that the DC-DC converter contains a transformer whose primary circuit consists of: namic power source (1), a parallel circuit (shunt) (2) and the switching element to the control device (3) and the secondary circuit - from the inductive energy storage device (5), capacitor storage (6) and the consumer (7). 4. The power source according to claim 3, characterized in that the switching element with the control device (3) is configured to transmit optimized frequency pulses through the transformer (4), which are used for energy storage in the inductive storage device (5). 5. The power supply according to claim 3 or 4, characterized in that the DC-DC converter has a planar transformer (4). 6. The power source according to claim 5, characterized in that the ratio of the capacitance of the parallel circuit (CSh) to the area (S) and the specific differential capacitance (CD, s) of the anode is from CSh = 0.5 · (CD, s · S) up to CSh = 5 · (CD, s · S). 7. The power supply according to claim 6, characterized in that the electrochemical current source (1) has a metal anode and a gas diffusion cathode. 8. The power supply according to claim 6, characterized in that an aqueous solution of sodium chloride is used as the electrolyte solution. 9. The power supply according to claim 7, characterized in that the anode consists of magnesium.

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