WO2015197885A1

WO2015197885A1 - Thermochemical method for the transfer and storage of concentrated solar energy

Info

Publication number: WO2015197885A1
Application number: PCT/ES2015/000084
Authority: WO
Inventors: José Manuel VALVERDE MILLÁN
Original assignee: Universidad De Sevilla
Priority date: 2014-06-26
Filing date: 2015-06-26
Publication date: 2015-12-30
Also published as: ES2555329A1; ES2555329B2

Abstract

The aim of the invention is the transfer and storage of concentrated thermosolar energy using a bed of granulated solids consisting of a mixture of inert solids, preferably sand, and CaCO3/CaO, fluidised by a controlled gas flow consisting of a mixture of inert gas, preferably air, and CO2 in controlled proportions. The invention corresponds to the field of energy and environmental technology as it is the sector of application wherein that of renewable energies would be applied.

Description

Title

THERMOCHEMICAL PROCEDURE FOR CONCENTRATED SOLAR ENERGY TRANSFER AND STORAGE

Object of the invention

The object of the present invention is the chemical transfer and storage of concentrated solar thermal energy through the use of a bed of granulated solids consisting of a mixture of inert solids, preferably sand, and CaCCVCaO fluidized by a controlled gas flow consisting of a mixture of inert gas, preferably air, and C0 ₂ in controlled proportion.

The area to which the invention corresponds is that of Energy and Environmental Technology, being the application sector in which the Renewable Energies would be applied.

State of the art

The technique described in the present invention aims to improve the transfer and storage of concentrated solar energy (CSP). In recent years there has been a great growth in the commercial development of this type of thermal power plants (1), being its main advantage the possibility of generating electricity even in the absence of solar radiation during a certain period of autonomy compared to nature flashing of other types of renewable energy plants such as wind or photovoltaic solar. In conventional fossil thermal plants, water vapor produced in a high pressure boiler is expanded in a turbine to generate mechanical work on its axis according to the Rankine cycle to be subsequently transformed into electrical energy by means of a generator. In CSP plants, the boiler is replaced by a concentrated solar radiation collector, the rest of the process (power cycle) being a thermal to electrical energy transformation similar to that of a fossil thermal.

Mainly, there are currently 2 types of CSP power plants in commercial expansion phase operating through central tower and parabolic trough technology, respectively. In the central tower CSPs, a set of reflector mirrors (heliostats) distributed over a large surface is used in order to reflect the solar radiation they receive on the same white collector located at the top of a central tower with more than 100 meters high. In the first commercial scale CSP plants with central tower technology (PS10 in 2007 and PS20 In 2009 located in Sanlúcar La Mayor, Seville, generating 11 and 20 MWe, respectively, of electrical power), heat is used directly to generate water vapor that is stored at high pressure and conducted to the power cycle. This design only allows a period of autonomy of electricity generation around 1 h. New designs already in operation in commercial plants incorporate thermal transfer fluids (HTF) with high heat capacity and transfer heat to water through heat exchangers. The first CSP with tower receiver technology (in operation since 2011) and thermal storage in HTF (molten salts) is the Gemasolar plant (19.9 MWe) located in Fuentes de Andalucía (Seville). The molten salts heated in the tower are stored in a large capacity hot salt tank and conducted to a heat exchanger. Once they give heat to the power cycle they are transported to a tank of cold salts to be recirculated back to the tower. The storage of heat in the hot salt tank allows an autonomy of electricity generation of up to 15 hours without solar input. In CSPs with parabolic trough technology, sunlight is concentrated on a collecting cylinder located in the center of a row of parabolic section reflectors. The collecting cylinder contains a mineral oil that acts as HTF. Solana, the largest CSP (280 MWt) with parabolic trough technology recently completed in the US It has an autonomy of 6h of storage.

CSP technology has enormous potential for short-term growth, especially in countries in North Africa and the Middle East, as well as in the US, South Africa, Australia, Chile, India and China where they have been successfully completed or several commercial scale projects are underway (2). Spain has been a pioneer country in the development of this type of power plants and as of January 2014 it continues to be a world leader in CSP with an installed capacity of 2,204 MWt. The development of efficient and low-cost HTFs is a key point for the commercial success of CSPs since the storage of solar thermal energy during long periods of low solar radiation would allow the generation of electric current continuously and on demand. Alternatively, there are projects in which the CSP-HTF is integrated in a hybrid system with a fossil thermal power plant, whose energy is used to raise the temperature of the HTF in the case of prolonged periods of reduced solar radiation.

According to the Rankine cycle (thermodynamic process that takes place in the power cycle in a steam power plant), the efficiency of heat conversion into mechanical energy increases with the temperature of the water vapor produced. In fossil plants, this temperature is limited by the resistance of materials used in the steam conduction system. Standardized steam turbines can operate at steam temperatures around 550 ° C. An important field of research focuses on the development of materials with very high resistance in order to increase the efficiency of electric power production and thus reduce CO2 emissions by fossil power plants. Recently, the American Society of Mechanical Engineers (ASME) has approved the use of a Ni-Cr-Co alloy (Inconel® 740) for the manufacture of steam conduction materials capable of withstanding temperatures up to 700 ° C (2). In CSP-HTF with parabolic trough technology, the temperatures reached in the collector are limited to values around 400 ° C, so it is not possible to obtain a high thermoelectric efficiency. Mineral oils used as HTF decompose at higher temperatures and have a freezing point around 12-20 ° C. On the other hand, the Gemasolar plant (Fuentes de Andalucía, Sevilla) with central tower technology operates at steam temperatures close to 550 ° C, which makes it possible to use standardized steam turbines commonly used in fossil thermal plants although potentially attainable temperatures in the collector of this type of CSP power plants could reach 900 ° C. In principle, the possibility of reaching higher temperatures would increase the conversion efficiency of solar energy concentrated in electricity (2). However, this temperature is limited by the degradation of the molten salts currently used as HTF and which decompose around 600 ° C. Another drawback of the use of molten salts such as HTF is that they have freezing points at relatively high temperatures (between 120 ° C and 220 ° C) with the consequent risk of freezing and large heat losses during night hours in desert areas and / or of high altitude that have a very high insolation that make them ideal for the installation of CSP power plants. This makes efficient thermal insulation necessary, limiting the flow of the fluid and eventually using energy to heat the salts in the cold tank in order to avoid freezing (in Gemasolar the temperature of the "cold" tank is maintained at 290 ° C). An additional problem associated with the use of mineral oils or molten salts such as HTF is generally its high corrosive and contaminating power. Valves, pipes, instruments, joints and standard monitoring systems are not suitable for the conduction of such HTFs, which implies an additional cost that makes CSP-HTF technology more expensive.

The development of materials compatible with the limitations imposed by the use of molten salts or mineral oils as well as the synthesis of new HTFs with improved thermal properties (increased heat capacity, reduced freezing point and increased decomposition temperature) (3 , 4) constitute Current research topics of great interest. In the CSP EOS project (Cyprus) it is planned to build a commercial scale plant (50 MW) in which the storage and heat transfer medium consists of solid graphite blocks with high melting point and specific heat. The commercial expansion of CSP technology necessarily involves enhancing its competitiveness even lower compared to fossil thermal power plants (2). The most urgent challenge to achieve this goal is to improve the efficiency of storage and transfer of concentrated solar energy. It is therefore a completely open field and in great development.

The object of the present invention is the transfer and storage of concentrated solar thermal energy through the use of gas fluidized beds of granulated solids (FB): "Fluidized Beds". As the SOLTESS project ("Solar Thermal Energy Solid Storage" carried out in Italy) has just demonstrated with the installation of a 0.1 MWt CSP-FB demonstration plant, the solid / gas fluidized bed system is very suitable for transfer and concentrated solar energy storage. This bed uses a bed of fine siliceous sand fluidized with air (at speeds of the order of cm / s) as a means of reception, exchange and transfer of concentrated solar energy allowing to reach steam temperatures in the range 530-730 ° C With an autonomy of 10-15 h, that is, it can generate electricity efficiently during 24 hours (5). The gas fluidized bed has a high coefficient of thermal transfer and diffusion that are adjustable through the control of the gas flow, while it is possible to achieve a high degree of storage in the granulated solids due to its high heat capacity. As an added advantage, the FB technology allows the gas combustion in the fluidized bed to be integrated into a hybrid system in order to heat it if necessary in long periods of absence of intense solar radiation. The CSP-FB technology would also allow the avoidance of corrosion and contamination problems associated with the use of molten salts or mineral oils. The sand is an inert material, abundant and readily available (especially in desert areas where the installation of CSP plants is indicated) which would contribute to the commercial expansion of the technology. The high performance of the demonstration plant built in Italy suggests that CSP-FB power plants could be sold in small modules depending on the demand of the region where they are installed. This feature will facilitate the commercial development of CSP technology because the need for CSP-HTF based on central tower and parabolic trough technology to have a relatively large minimum size (around 10MWe) to achieve acceptable performance is exceeded. which makes the cost of the installation excessively high Currently, the group that has executed the SOLTESS project projects the construction of a commercial module CSP-FB of 1, 85MWt and that will supply 0.65MWe. This year 2014, another 2 industrial projects have been initiated in the United States (US Solar Holdings) and United Arab Emirates (SANDSTOCK) in which the sand / gas fluidized bed technology will also be analyzed with the final objective of building a CSP-FB plant to commercial scale These studies demonstrate that CSP-FB integration has significant potential for the development of concentrated solar energy on a commercial scale. The object of the present invention is a method that will foreseeably improve the energy storage capacity by means of this innovative technology.

References

(1) V. S. Reddy, S. Kaushik, K. Ranjan, and S. Tyagi, "State-of-the-art of solar thermal power plants: a review," Renewable and Sustainable Energy Reviews, vol. 27, pp. 258-273, 2013.

H.L. Zhang, J. Baeyens, J. Degreve, G. Caceres, "Concentrated solar power plants: Review and design methodology", Renewable and Sustainable Energy Reviews, vol. 22, pp. 466-481, 2013.

(2) J. T. Hinkley, J. A. Hayward, B. Curtin, A. Wonhas, R. Boyd, C. Grima, A.

Tadros, R. Hall, and K. Naicker, "An analysis of the costs and opportunities for concentrating solar power in Australia," Renewable Energy, vol. 57, pp. 653-661, 2013.

(3) D. Shin and D. Banerjee, "Enhanced specific heat of silica nanofluid," Journal of Heat Transfer, vol. 133, p. 024501, 2011.

(4) Andy. Skumanich, "Csp: Developments in heat transfer and storage materíals," Renewable energy focus, pp. 40-43, September / October 2010.

(5) R. Chirone, P. Salatino, P. Ammendola, R. Solimene, M. Magaldi, R. Sorrenti, GD Michele, and F. Donatini, "Development of a novel concept of solar receiverAhermal energy storage system based on compartmented dense gas fluidized beds, "in The 14th International Conference on Fluidization From Fundamentalis to Products, Engineering Conferences International, 2013.

Description of the figures

Figure 1.- Scheme of the integration of concentrated solar thermal energy technologies with transfer and storage of thermal and chemical energy in a fluidized bed of granulated solids (mixture of inert materials with high heat capacity and thermal conductivity and CaC03 / CaO) by means of a controlled flow of gas containing C02 in a certain percentage.

(a) Solar radiation incident. (b) Controlled gas flow containing C02.

(c) Mixture of inert granulated solids and CaC03 / CaO.

(d) Control unit of gas composition and flow.

(e) Heat exchanger.

(f) Power cycle.

Figure 2 - Concentration values (% by volume) of C02 in the gas and temperature that determine the displacement of the reaction CaC03 = CaO + C02 in order to store or obtain energy by means of this fluidized bed reaction.

Description of the invention

This invention proposes the use of a bed of granulated solids consisting of a mixture of inert solids (for example sand) and CaCCyCaO (derived for example from natural limestone) fluidized by a controlled gas flow consisting of a mixture of inert gas (for example air) and C0 ₂ in order to transfer and store thermochemically concentrated solar energy. The novelty of the invention is the use of CaC0 ₃ / CaO in the fluidized bed and C0 ₂ in the fluidization gas, which makes it possible to complement the storage of solar energy thermally in the sand with chemical storage by means of the endothermic decarbonation reaction of CaC0 ₃ . When the temperature reached at certain points of the bed is excessively high and cannot be exploited in the power cycle, controlling the proportion of C0 ₂ in the gas flow would allow the endothermic decarbonation of CaC0 ₃ . Conversely, when this temperature dropped below a desired value due to long periods of low solar radiation, it would be possible to carbonate the CaO by exothermic reaction that would provide the heat previously used in decarbonation to transfer it to the power cycle. In this way it would be possible to increase autonomy and thermoelectric efficiency. Likewise, chemical storage would reduce the volume of solid fluidized bed / gas that may become excessively high if only thermal storage is operated. The chemical storage of solar energy would not present losses as occurs with thermal storage. In this novel procedure, the advantages of the use of fluidized beds associated with high values of thermal transfer and diffusion with the high heat capacity of inert solids for thermal storage and the high latent and sensitive heat values of CaC0 ₃ are integrated in the same technology Chemical storage of energy stably. The mixture of CaC0 ₃ with an inert material such as silica would also increase the reversibility of the decarbonation / carbonation reactions because silica favors the thermal stability of CaC0 ₃ / CaO. Likewise, if a hybrid system is included, including the combustion of gas in the fluidized bed, the decarbonation / carbonation of CaC0 _{3 will} allow the excess heat to be chemically stored for later use according to demand. Finally, the use of additional fluidized beds exclusively of CaC0 _{3 would} allow not only storing but also transporting concentrated solar energy (in the form of CaO) without loss for use in other applications, which would expand the range of possibilities of use of CSP plants and thus help its commercial development.

The use of concentrated solar energy to calcine CaC0 ₃ at high temperature, this heat being able to be recovered when necessary by carbonation of CaO, has already been proposed as a method of storing solar energy. CaC0 ₃ has a high energy density (1.7 MJ / kg of latent heat and 0.87 MJ / kg of sensible heat much higher than the typical values that have molten salts) and is a raw material that can be obtained from natural materials available in abundance and low cost (for example natural limestone). In addition, both CaC0 ₃ and CaO can be stored for long periods of time in atmospheric conditions and without thermal losses as occurs with HTFs used in CSP technologies with storage in molten salts or mineral oils (CSP-HTF) or with the sand used in technology with solid fluidized bed / gas storage (CSP-FB).

Thus, the decarbonation (or calcination) and carbonation cycle of CaC0 ₃ / CaO (CaL) has recently been proposed in an integrated concept (CSP-CaL) in order to store and transfer concentrated solar energy. According to this concept, the CaO and C0 ₂ generated by the calcination of CaC0 ₃ would be transported separately, and when the demand made it necessary, the carbonation of the CaO would serve to transfer heat to a gas stream used for the production of electricity by A gas turbine However, the results suggest that CSP-CaL integration would only be advantageous with respect to CSP-HTF technology in a limited range of CaO conversion values between 20% and 30% (percentage of CaO converted to CaC0 ₃ in the carbonation reaction), which constitutes an important practical limit for the possible start-up of CSP-CaL technology, which has not yet been proven in practice. Normally, the conversion values of CaO in the reaction of Carbonation in a fluidized bed exclusively of CaO oscillates in a very wide range of values (between 80% and 7%) depending significantly on the calcination / carbonation conditions (basically temperature, concentration of C0 ₂ and residence time of the gas in the bed) and the number of previous cycles. Experimental results show that high temperature calcination causes the residual conversion (the one obtained after a high number of cycles) of CaO to fall below 10%, which would make it unfeasible to use CaL technology as the only storage method of concentrated solar energy. On the other hand, although there are synthetic materials based on CaO / CaC0 ₃ , and treatment methods that can reactivate the CaO derived from natural limestone, the use of such techniques would cost more a technology whose greatest potential advantage should lie in its low cost and abundance of a non-polluting raw material.

In the present invention, the integration of CaL technology with CSP-FB fluidized bed storage technology is proposed in order to increase the storage autonomy and efficiency of the latter. In CSP-FB concentrated solar energy is stored exclusively in thermal form. Although the use of large volumes of inert material such as sand (which can be a problem due to the size of the bed in relation to the power generated) can be a solution to extend the transitory period of storage, CSP integration -FB-CaL would allow the storage of energy in chemical form and therefore permanent to be used when the heat was necessary. This integration would therefore have the advantages of high thermal transfer and diffusion provided by the fluidized bed of sand with thermal storage on the one hand and, on the other, permanent storage in chemical form by means of CaL technology.

In the CSP-FB-CaL integration proposed in the present invention, the transfer and storage of concentrated solar energy would be carried out in a fluidized bed formed by a mixture of inert granulated solids which is the thermal transfer medium (for example sand) with CaC0 ₃ / CaO, which is the medium where energy will be chemically stored. The relative proportion of CaCOs / CaO can vary from 100% to 0%. The fluidization gas velocities would be small (of the order of cm / s as in the current CSP-FB technology) so that the residence times of the gas in the bed are prolonged, which allows the calcination / carbonation reactions in around equilibrium reach advanced states. Since calcination would occur slowly at temperatures close to equilibrium as soon as it is exceeded, the reactivity of the regenerated CaO will not be seen. significantly diminished as in CaL technology where CaC0 ₃ suddenly heats up to temperatures well above equilibrium. Likewise, mixing CaC0 ₃ with inert granulated solids such as silica (sand) contributes to thermally stabilize the limestone according to experimental observations.

The fluidization of sand / CaCCVCaO in contact with the solar collector using a C0 ₂ / air mixture in percentages that can vary from 0% (if you want to calcine at temperatures below approximately 700 ° C) up to 100% (if desired carbonation at high temperatures), would result in calcination of CaC0 ₃ at temperatures above a desired critical value and exothermic carbonation of CaO when the temperature dropped below a certain value which would allow increasing the autonomy of this storage method and homogenize the heat delivery to the power cycle. In addition, the volume of material that would be necessary to use to maintain a sufficiently high storage bed temperature could be reduced. In the pilot device CSP-FB of 0.1 MWt in current operation (SOLTESS project) about 15000 kg are used in the storage bed to maintain its temperature between approximately 530 ° C and 780 ° C in night / day cycles and thus allow a continuous operation of the power unit with a global efficiency of transformation of solar energy to the power unit around 70% (much higher than in CSP with parabolic trough and central tower technology that is established around 20%) . With 15,000 kg of sand, an autonomy of operation is achieved around 10/15 h. It is to be expected, however, that the need to use volumes of sand that are too high represents a problem in the higher level scaling of CSP-FB technology. In addition, the energy required to fluidize the material can be a limiting factor if very high volumes are required since the pressure drop across the bed of the applied gas flow must necessarily compensate for the total weight per unit area of the bed. Taking into account the high latent and sensitive heat of CaC0 _{3, it} is foreseeable that the total mass of material needed in CSP-FB-CaL technology can be reduced, so this integration proposed in the present invention could provide an advantage in a relevant aspect. in the commercial development of technology such as the energy needed to fluidize large volumes of material. On the other hand, the CSP-FB technology offers the possibility of varying control parameters that regulate the thermal transfer such as the speed of the gas in order to counteract the effect of the variability of the intensity of solar radiation on the bed temperature of storage. Through the CSP-FB-CaL integration that we propose in the The present invention would have a new strategic control parameter (% C0 ₂ in the fluidization gas) in order to cause decarbonation or carbonation reactions as desired to reduce or increase the temperature of the bed depending on the intensity of solar radiation . The carbonation during periods of low radiation using gas flows with high% C0 _{2 would} allow the temperature to rise thus increasing the performance of the technology. Depending on the intensity of solar radiation, an optimum proportion of CaC0 ₃ can be chosen in the granular solids mixture. The fluidizing gas may circulate in a closed circuit so that C0 ₂ emissions to the atmosphere are prevented.

In CSP-FB it is necessary to divide the fluidized bed into compartments for receiving, exchanging and storing solar thermal energy for the selective control of the gas velocity in each of them in order to avoid minimizing the inevitable thermal losses. During the night, for example, the gas supply to the receiving compartment is cut off (to avoid heat leaks to the solar radiation receiving cavity) and to the storage compartment if its temperature falls below a critical value. The absorption / release of chemical energy in the integrated CSP-FB-CaL technology proposed in the present invention can be selectively controlled along the fluidized bed by regulating the% C0 ₂ in the fluidization gas through each compartment which would contribute to reduce heat losses. In addition, the possibility of adding a compartment for a fluidized bed exclusively of chemical energy storage CaC0 _{3 is considered} . The high thermal transfer in solid fluidized bed / gas would allow efficient transfer of excess heat to this compartment. The CaO generated by calcination in this compartment can be used in the same plant if necessary to generate heat and increase the steam temperature or be transported if produced in excess for heat generation in other industrial applications.

The effectiveness of the CSP-FB-CaL integration described in the present invention would critically depend on the reactivity of the regenerated CaO in each cycle by calcination. Results obtained in our laboratory show that it is possible to maintain a high cyclic reactivity of CaO regenerated under certain conditions of calcination / carbonation as calcination in air and carbonation in an atmosphere with high concentration of C0 ₂ at temperatures between 600 ° C and 900 ° C The possibility of introducing H ₂ 0 vapor, around 20% by volume, into the fluidized bed would also contribute to increasing the reactivity of CaO as experimental results show. Taking into account the oscillation range of temperatures in the current CSP-FB technology, these conditions would be compatible with an efficient CSP-FB-CaL integration.

Embodiment of the invention

An exemplary embodiment of the invention based on the integration of CSP-FB-CaL technologies (thermochemical transfer and storage of concentrated solar energy in a fluidized bed of inert granulated solids and CaC0 ₃ / CaO) is shown in Figure 1. Solar radiation (a) is collected by the fluidized bed (c) by a cavity in the same way as is done in the proven CSP-FB technology. The bed of granulated solids is formed by a mixture of inert solids (for example fine siliceous sand) of high heat capacity and thermal conductivity and CaC0 ₃ / CaO (derived for example from natural limestone). The bed is in a fluidized state by the application of a gas flow (b) consisting of a mixture of inert gas (for example air) and C0 ₂ at a rate and in an adjustable proportion in the control unit (d) . The possibility of introducing steam is contemplated in order to intensify the reactivity of the CaO if necessary. Through heat exchangers (e), the heat stored in the fluidized bed is transferred to the power cycle (f) for the generation of electric energy following the conventional procedure carried out in fossil plants. It is possible to divide the fluidized bed into different compartments (receiver, exchanger and energy storage) as in the CSP-FB technology. The modification introduced in the present invention consists in the integration of CaL technology. In a division in compartments of the fluidized bed it is possible to use mixtures of inert solids / CaC0 ₃ / CaO in varying proportions in each of the compartments in order to intensify the exothermic carbonation in the regions close to the exchangers and thus increase in mode more efficient steam temperature. There is also the possibility of passing gas flows with different% C0 ₂ through each compartment in order to intensify decarbonation in the higher temperature region by reducing% C0 ₂ (normally the reception compartment during the day) and intensifying the carbonation by applying a flow with high% C0 ₂ (usually in the exchanger and the storage unit if the temperature is too low). An exclusive chemical storage compartment consisting of a fluidized bed of CaC0 ₃ can also be added. The CaO generated in this compartment can be used in the same plant to release heat by carbonation or be transported for use in other applications that require hot. This CaO can be stored without energy losses for use when and where necessary. Although fluidization allows a high degree of thermal transfer to be obtained, there is the possibility of applying techniques that intensify the transfer of heat and mass to enhance the carbonation of CaO. One of these techniques of proven efficiency to enhance the carbonation of CaO in other applications in a high temperature fluidized bed reactor is the application of high intensity and low frequency sound that could be implemented in this invention.

The control of the% C0 ₂ used in the fluidization gas can be carried out in accordance with the equilibrium of the decarbonation / carbonation reaction of CaC0 ₃ represented in Fig. 2 and depending on the temperature distribution in the fluidized bed. This diagram allows to anticipate the direction in which the reaction will move according to the% C0 ₂ in the fluidization gas and the temperature. Thus, if for example the% C0 ₂ is maintained at around 10%, the system will release heat (carbonation of CaO) where and when the temperature drops below 750 ° C and absorb heat when the temperature rises above this value. (decarbonation of CaC0 ₃ ). The regulation of% C0 ₂ in the fluidizing gas in the gas control unit would be used as a temperature control mechanism in the fluidized bed so that it is transferred with few oscillations to the power cycle.

The total amount of heat absorbed and released in the fluidized bed depends on the proportion of CaC0 ₃ and CaO used in the mixture of granulated solids that can also be variable depending on the incident solar radiation characteristic of the region where the plant is installed . At all times, excess heat will be stored chemically permanently and stably in the form of CaO to be used when necessary. This heat can come from the combustion of gas in the same fluidized bed as proposed in the CSP-FB technology in a hybrid system. However, heat can only be stored temporarily in CSP-FB since the bed of inert solids (sand) will always have thermal losses. The only possible solution in CSP-FB to prolong the transitory storage period is to increase the volume of the fluidized storage bed with the consequent loss of technology efficiency. In the CSP-FB-CaL concept proposed in the present invention, excess heat can be permanently stored chemically until it is necessary to recover it, so it is expected that this innovation will result in improved storage with respect to CSP technology. FB

Claims

1. Thermochemical procedure for the transfer and storage of concentrated solar energy characterized in that it consists in subjecting a bed of concentrated solids to the solar fluid concentrated by gas and which is divided into compartments for the reception, exchange and storage of energy depending on the proportion of mix.

2. Thermochemical process for transferring and storing concentrated solar energy according to claim 1, characterized in that the granulated solid is constituted by a mixture of inert granulated solids, preferably sand, and CaCCyCaO, preferably derived from natural limestone.

3. Thermochemical process for transferring and storing concentrated solar energy according to claims 1 and 2, characterized in that the gas flow used for fluidization is formed by a mixture of inert gas, preferably air, and C0 ₂ in controlled proportion such that by Above a critical temperature value, preferably 700 ° C, chemical energy is stored by decarbonation of CaC0 ₃ .

4. Thermochemical process for transferring and storing concentrated solar energy according to claims 1 and 2 characterized in that the gas flow used for fluidization is formed by a mixture of inert gas, preferably air and C0 ₂ in controlled proportion such that below from a critical temperature value, preferably 700 ° C, chemical energy is released through the carbonation of CaO.

5. Thermochemical process for transferring and storing concentrated solar energy according to claim 4, characterized in that the incorporation of controlled quantities around 20% by volume of H ₂ 0 vapor in the gas flow allows to increase the reactivity of CaO.

6. Thermochemical energy transfer and storage method according to claim 1, characterized in that the application of sound waves on the fluidized bed intensifies the transfer of heat and mass in the fluidized bed.