EP2089926A1

EP2089926A1 - Electric energy production by voltaic cell solution temperature change

Info

Publication number: EP2089926A1
Application number: EP07824966A
Authority: EP
Inventors: Vasilios Styliaras
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-16
Filing date: 2007-11-14
Publication date: 2009-08-19
Also published as: GR20060100620A; WO2008059297A1

Abstract

Electrical energy production by changing the solution of a voltaic cell and use of heat. Voltaic cell opperation, causes electrolyte concentration change. The solution passes through heat exchanger, so that the temperature changes and electrolyte crystals are formed and removed.The cell solution is replaced by another solution which in, the removed electrolyte crystals have been dissolved and operation at opposite direction is forced. The difference of the electromotive force of the two cell solutions, gives the useful electric energy.

Description

Electric energy production-heat transfer- by voltaic cell solution change

DESCRIPTION

The invention refers to electric energy production, using electric (electric-galvanic) cells. Electric cells are used to convert chemical to electric energy and vice versa. To achieve a cyclic process (charge -discharge) of a cell, electric energy has to be consumed. The charge energy equals the discharge one (reverse processes are assumed). In this way, a cell can be used only for energy storage. The use of hydrogen fuel cells is hydrogen consuming.

The difference of this invention is that the cell charge (when we offer power), takes place in a different solution from that of the discharge (we take power). We select the solutions so that the electromotive force (emf) during charging is lower than that of discharging. The difference is the useful power. Solutions concentration change during cells operation. Electrolyte is transferred from one solution to the other. Heat is used for this process.

Depending on the solution, heat is absorbed or rejected during electrolyte secondary phase formation (crystallization) and its dissolution (crystal dissolution) into the other solution. If the solution (solvent -solute combination) is such that heat is absorbed during crystallization and rejected during dissolution, heat is transferred from discharge temperature level to charge level. Heat losses are removed to keep the temperature of the process at a selected level. The solution circulates between the cell and a heat exchanger so that crystallization heat is exchanged at the heat exchanger. In this case heat is absorbed by the solution through heat exchanger. The conversion of chemical energy to electrical, is based on the fact that when an electrode (metallic bar,) is dipped into an electrolyte solution, electric potential (emf) appears on its surface. This potential is different for each element. When the poles of two different bars (elements) dipped into the solution are connected , electric current flow will take place. In the same time, ions of the electrolyte release from the electrodes (bars).Depending on the particular solution, the opposite may happen(ions leave the solution,depositing on the electrodes ). Connecting an electric source of opposite potential between poles, the solution concentration and electrodes will return to their original situation(Reverse processes are assumed).Ignoring losses, energy consumed when current flows in one direction, equals that of the opposite direction. The electrolyte consumed during one phase of operation, is reconstructed during the opposite phase. The potential of the electrodes as well as the energy released, depends on the electrolyte concentration and the solvent. It means that solutions of different concentration release and consume different energy amounts. The same electrolyte on a different solvent, will release different energy amount as well.

Suppose an aqua ZnCk solution is combined with Zn/Zn** andPt/ Cl/Cl^' electrodes.The discharge reaction is Zn+Cl2— ►ZnCk+ΔG _di_schmg_e* where ΔG is the free energy change, converted to electricity. Δ G=-zFE=-2*96487*2.12=-409105 J=-97.8Kcal/mole electrolyte.The electromotive force (emf) of Zn/Zn^ is -0.76Vand emf of Pt/ Cl/Cl- is +1.36V.Thus E=Eo=I.36-(- 0.76)=2.12V.z is the ion charge and F the Faraday constant. This is accurate for a solution of activity a=l.When i.e. M=0.13mole electr./Kg solution, thenΔG=-115.5Kcal/mole.In general E=Eo-(RT/zF)ln(γ+-m+). In another cell, Pt/H₂/HCl/Ag/AgCl when c=0.0010mol/dm , ΔG=55920 and for c=0.054, ΔG=36880.

Useful energy= (Eθdisch.-Eo_Chargc)+RF(T dischhi(γ+- m_+-disch.)-T chln(γ+- m_+ch.)). If the (M=O.13 ZnC12) solution is used for discharge and the other for charge, a useful electric energy of ΔGdisch-ΔGcharge=l 15.5-97.8=17.2Kcal/mole will result, (numerical values are approximate). Lets see Figure l.Cell U₁ includes a H₂O-ZnCl₂ solution at 30⁰C and 1^29.EIeCtTOdCS Hl and H2 are dipped into the solution.One of them is a Pt electrode and the other a Zn one.C-₂ is fed to Pt and the poles are connected to an electrical consumption.Zn ions enters the solution and the ZnCl₂ concentration increases to M₂=32(saturated).Electric energy is offered by the cell. In the next step,the electrodes are transfered to cell π₂which includes another (secondary) solution or the original solution of IIiis replaced by this secondary one. This secondary solution consists of the same electrolyte at different concentration (and temperature)or in different solvent too.Lets say that this is an aqua ZnCl₂ solution too of M₄=45 at 100 ⁰C (saturated).The poles are connected through an electrice source HTI,the voltage of which is reverse and a little higher from the emf of the poles. A current of reverse direction will flow and OiJLn ⁺ ions will move toward the electrodes.The reaction is

ZnCl₂ →l/2Zn₂+Cl₂ -ΔG_chMge The solution concentration will decrease to Mv=42. The original solution which concentration increased to M₂,is driven through a heat exchanger EN so that its temperature changes to 20 ^υC and crystals of electrolyte are formed. Since the solubility at this temperature is Mi=29, three (3)moles of salt will separate. These crystals are removed from the solution and enter the secondary solution which exits cell IT₂ so that its concentration changes from M₃ to MμThe original solution is driven back to cell FIi recovering heat from heat exchanger EN. The original solution may be concentrated from the beginning (M2 instead of Ml) so that crystals will be created without temperature change imposition. Crystals may enter the saturated solution (M4).Dissolution will take place during cell operation(as electrolyte ions move to electrodes) and the solution concentration will remain constant. The heat exchanged by the system is a)crystallization enthalpy offered to (absorbed by) the system through heat exchanger is ql ¹¹^¹¹¹H_MISOI, where m the crystal moles and H_MI_SOI the solution enthalpy at concentration Ml and temperature Tl b)heat evolved (rejected )during crystals solution ,where HM_3soithe solution enthalpy at concentration M3and temperature T3.

The total heat consumption from (offered to) the system is ql-q3 and equals (approximately) the useful electric energy= ΔGdischarge -ΔG_Charg_e . A cycle has been completed since the two solutions recover their original concentration and the electrodes their original form.

Depending on the particular solutions used, application of electrical source may not be used.

Selecting the right solutions, the electric power that is offered by the cell may be higher from that consumed for recharge.ΔG of many solvents, are so different, as to create a satisfactory voltage difference. Removing of first solution particles from the second solution may need, in case such particle are transferred by the electrolyte. In a cycle variation, electric power is offered by the cell when electrolyte ions are moved towards the electrodes (It may be attained by using the convenient solution). We bring these products together, so that they react forming the original electrolyte. This electrolyte dissolves into the solution, restoring the initial concentration. The cycle is completed. As an example, suppose a volatile electrolyte is used, so that two gases are released from the electrodes while we take electrical energy. We bring the gases together and they react reforming the electrolyte which is again dissolved in the solution.

Claims

1. The method and equipments for electric energy production by changing the solution of a voltaic cell characterized by the fact that the charge of the cell takes place in a solution, different from that, the discharge takes place. During one of the operating phases i.e.(discharge),the cell offers electric energy and the electrolyte concentration increases(if the solution is already concentrated ,produced electrolyte may be partially dissolved). Passing the solution through a heat exchanger, the temperature changes and the concentration decreases, reaching the original concentration. The electrolyte quantity formed during cell operation is removed in this way. Next ,this electrolyte quantity, is poured (dissolved) into the second solution (charge solution).Electrodes are removed into this solution (or this solution replaces the first one)and the poles are connected through an electric source, so that reaction in the cell moves the reverse direction and the cell is charged until its concentration became the same with that at the beginning (before charge start). A cyclic process is completed since the solutions recovered their original concentration and the electrodes their original form. Electrodes are moved to the first solution (discharge solution) and the cell works offering again electric power. The two solutions (charge and discharge) have different electrolyte concentration and may consist of different solvent too. The charge solution may be concentrated when the cell works, so that the separated phase (i.e. solid crystals) is created without need of temperature change. Using a solution absorbing heat when a different phase is formed (crystals) and rejecting when this phase is dissolved, heat transfer from one temperature level to another takes place. Rejected heat and heat losses during operation are used inside the cycle or for space heating. Discharge process is kept at a selected temperature by removing heat. The solution is circulated between the cell and a heat exchanger so that crystallization absorbs heat from the heat exchanger (when such a solution has been selected ).

Other processes, like pressure change, may be used to help removing and dissolving of electrolyte in the solutions (i.e. when using volatile electrolytes) while particles of one solution entering the other have to be removed.

2. The method and equipments for electric energy production by using an electric cell of convenient solution so that when electricity is offered by the cell, electrolyte ions are moved toward the electrodes. We bring these products (electrolyte atoms or moles created on the electrodes) together so that they react, forming the original electrolyte. This electrolyte is dissolved again in the solution. The original solution (concentration) is reformed.