ES2434665B2 - Concentrating solar thermal power plant with two fluids in the receiver and in storage - Google Patents

Abstract

Thermosolar power plant with condensable fluid concentration with a multi-tube receiver (5) with low (2), intermediate (3) and high (4) radiation zones such that the low radiation zone (2) is used to heat the working fluid of the cycle, in a liquid state, from the condensation temperature, from a condenser (13) of variable level, to that of evaporation, being stored in a boiler (12) of variable level at said temperature. The intermediate (3) and high (4) radiation zones are used to heat a calorific fluid from its minimum temperature to its maximum temperature, being stored in two or three storage tanks (9, 10 and 11) at different temperatures, to a subsequent transfer of heat to the working fluid to evaporate and overheat it before entering the turbine (32) of the cycle.

Description

Technical sector

The invention falls within the field of solar power plants that require concentration of the original radiation, which reaches a multitube receiver with a concentration gradient (with active areas of greater and lesser concentration), as is the case of a Cavity receptor in a Fresnel field of reflection or an outer receiver in a field of central tower helioslails. Specifically, it refers to the use of two fluids in a multi-tube receiver and in storage, and to the procedure to maximize the use of low concentration areas and minimize exergy losses.

In particular, the invention takes into account the variation of the concentration in a multitube receiver, and how the different optimum working temperatures of two heat fluids can be used to maximize the energy use of the incident radiation.

Technical problem to solve

This invention aims to solve two technical problems: on the one hand, to take advantage of the incident radiation in a solar receiver with relatively low concentrations due to the dispersion of the reflected beam and, on the other hand, to allow a thermal storage system with more than one level of temperature, which minimizes exergy losses in heat transmission; All this seeks to simplify the plant and reduce costs.

In solar fields with a fixed receiver where several heliostats reflect the radiation towards said single receiver, such as the Fresnel linear collectors and the central towers, there is a scattering of the light proportional to the distance between each mirror and the receiver. This produces that in the central part of the receiver the incident radiation is very high, while

which on the sides is much smaller. The use of a single calorific fluid in the receiver makes the temperature range relatively narrow, being between 290 oC and 400 oC in synthetic oils (traditionally used in parabolic trough collectors), and between 290 oC and 565 oC in the salts cast (used in some central towers). The main problem lies in the threshold of use of the calorific fluid, which prevents the use of areas of low concentrations. This would not have to be in the case of direct steam generation, in which water can be introduced at a very low temperature (the one that exists at the exit of the condensate pump), and preheated with exergetic use in the areas of lower concentration to evaporate and then overheat in the central area; However, such a system would be faced with transient management difficulties, as well as for the storage of thermal energy due to the enormous specific volume of steam, this being an essential point in the generation of concentrated solar electricity. In this way, the invention aims to solve the conjunction of the maximization of the thermal use of the concentrated radiation on the receiver and the storage of that energy in volumes and with acceptable costs.

Background of the invention

The invention has two immediate antecedents, some of the inventors of the present and said invention being the same. The first antecedent is the patent ES 2 334 198 82, "Helio-thermal power plant with exergy heat management", which deals with the storage of thermal energy in hours of maximum radiation due to a solar multiple greater than one, with exergy use by the use of two hot storage tanks at different temperatures. The storage fluids in this case, which may be the same or different for the two tanks, are different from the calorific fluid that cools the receiver of the solar plant. Thus, storage at different temperatures is not made from a collection of radiation with different concentrations, but from transmitting heat from the heat fluid in two stages in series.

On the other hand, there is an antecedent regarding the receiver: the patent ES 2 345 759 82 "Receiver for solar power plant with longitudinal mirrors", with the same inventors as the previous one. In the second claim of said patent the use of a symmetric multitube receiver is mentioned, so that the tubes are grouped into beams according to their distance to the longitudinal central axis, the lateral beams being subjected to a lower concentration than the central ones. The calorific fluid enters a relatively low temperature through the lateral beams, subsequently passing through the plant, so that the creation of entropy is minimized. This claim, however, is limited to the passage of a single fluid through the receiver, and does not concern the storage of thermal energy. In addition, patent ES 2 356 549 81, "Variable width solar receiver and width variation method", whose inventors are included in the present invention, describes a multi-tube receiver with valves at the ends of each tube or tube bundle, of so that the flow through them can vary. Specifically, in its claim 4 it is said that at the outlet of each tube the fluid may go either to an outlet manifold, or to the next tube in series.

With respect to multi-tube receivers, WO 2009/029277 A2 patent proposes its use in a Fresnel reflection concentration thermoelectric power plant in its figures 8 to 11, but in them there is no clear exergy use, and in no case the use of two fluids The same authors of this last patent use the same figures of a multi-tube receiver in WO 2009/023063 A2, where the circulation of the heat fluid is not mentioned in any case.

Finally, US Patent 4400946 A shows in Figures 3 and 7 the possibility of storing in several tanks with different temperatures. However, at no time does it refer to the use of these deposits with different fluids, which can also be calorific fluids of the recipient.

Description of the invention

The invention describes a concentration solar thermal power plant, which follows a condensed fluid power cycle and comprises:

a steam turbine and a hydraulic pump;

a multi-tube solar radiation receiver;

a boiler of variable level, which acts as a boiler for the cycle and storage of a working fluid saturated at the evaporation pressure of the cycle;

a variable level condenser, which acts as a condenser of the cycle and storage of the saturated working fluid at the condensing pressure of the cycle;

a thermal energy storage system in a heat fluid with at least two temperature levels, with a low temperature tank and another high temperature tank;

at least three heat exchangers of the calorific fluid with the working fluid: a preheater, an evaporator and a superheater.

Among the above elements there is a plurality of hydraulic connections. On the other hand, two different fluids circulate through the multitube receiver: a working fluid, which produces power when expanding in the turbine, and a calorific fluid, which serves to accumulate energy in different deposits of the installation. In addition, the receiver consists of three radiation concentration zones:

a first zone of low radiation, so that the radiative intensity at each of its points is lower than at any point of the receiver not belonging to the low radiation zone, with a superstition relative to the total superstice such that the average captured energy in that area it is between 25% and 40% of the total energy captured in the receiver; a second high radiation zone, such that the radiative intensity at each of its points is greater than at any point of the receiver not belonging to the high radiation zone, with a surface relative to the total superty of the receiver such that the captured energy average in that area is between 5% and 35% of the total energy captured in the receiver; Y,

a third intermediate radiation zone between the low radiation zone and the high radiation zone, so that the radiative intensity at any of its points is greater than the radiative intensity at any of the points in the low radiation zone, but less than in any of the high radiation zone.

The working fluid circulates through the tubes of the low radiation zone, and the heat fluid flows through the tubes of the high radiation zone and the intermediate radiation zone, so that

the working fluid circulates in the liquid state through the low radiation zone of the receiver to the evaporation pressure of the cycle, increasing its temperature to, at most, the saturation temperature at said pressure; the heat fluid flows through the intermediate and high radiation zones of the receiver, increasing its temperature to its maximum working temperature for maximum concentrations of the time of the given year.

It is also true that the low radiation zone is located on the sides of the receiver; the high radiation zone is in the central zone of the receiver, and the intermediate radiation zone is between the low radiation zone and the high radiation zone.

The solar thermal power plant comprises valves and an expansion vessel in the circuit of the low radiation zone of the receiver, so that:

the valves open and close and the hydraulic pump is activated and deactivated depending on the radiation received in the low radiation zone of the receiver, The expansion vessel allows expansions and contractions of the working fluid in the circuit due to temperature changes if the valves are closed.

In another configuration of the solar thermal power plant there is at least one storage tank for heat fluid, at an intermediate temperature between the temperatures of the first tank and the second storage tank of the heat fluid.

The solar thermal power plant also includes:

a plurality of shut-off or shut-off valves in the various connection circuits between the two storage tanks and the boiler, the turbine, the condenser and the condensate pump, and receiver and heat exchangers; a plurality of flow drive pumps;

so that said valves and said pumps are activated and deactivated depending on the radiation received in each zone of the receiver depending on the radiation received.

In another configuration the solar thermal power plant comprises:

a plurality of shut-off or shut-off valves in the various connection circuits between the three storage tanks and the boiler, the turbine, the condenser and the condensate pump, and receiver and heat exchangers; a plurality of flow drive pumps;

so that said valves and said pumps are activated and deactivated depending on the radiation received in each zone of the receiver depending on the radiation received.

The invention also describes a method of operating a concentrating solar thermal power plant so that when the radiation in the low radiation zone of the receiver causes a temperature in the working fluid to reach at least 100 oC below the temperature in the boiler, and provided that the condenser is not empty and the boiler is not full, the working fluid is pressurized from the condensing pressure in the condenser to the evaporation pressure in the boiler, being pumped at said pressure in the state liquid from the condenser to the boiler through the circuit of the low radiation zone of the receiver.

According to said procedure: when the temperature reached by the working fluid in the circuit of the low radiation zone of the receiver is lower than that of saturation at the pressure of the boiler, heat fluid is pumped from the high temperature tank to the tank of low temperature by the preheater heat exchanger, where it yields heat decreasing its temperature until reaching the temperature of the tank; and the working fluid circulates in a liquid state from the low radiation zone of the receiver to the boiler through the preheater, where it absorbs the heat ceded by the heat fluid by increasing its temperature to the boiler temperature, which is the saturation temperature at evaporation pressure of the cycle.

According to another variant of the procedure: when the temperature reached by the working fluid in the circuit of the low radiation zone of the receiver is lower than that of saturation at the pressure of the boiler, calorific fluid is pumped from the intermediate temperature tank to the low temperature tank by the preheater heat exchanger, where it yields heat by lowering its temperature until it reaches the temperature of the low temperature tank; and the working fluid circulates in a liquid state from the low radiation zone of the receiver to the boiler through the preheater, where it absorbs the heat transferred

by the calorific fluid increasing its temperature to the boiler temperature, which is the saturation temperature at the evaporation pressure of the cycle.

In another configuration of the procedure, when the radiation in the intermediate and high radiation zone of the receiver increases until the heat fluid reaches the temperature of the high temperature storage tank, and provided that the low temperature tank is not empty and that the High temperature tank is not full, the heat fluid is pumped from the low temperature tank, circulating first through the circuit of the intermediate radiation zone of the receiver and then through the circuit of the high radiation zone of the receiver, to the tank high temperature

In another variant of the procedure:

when the radiation in the intermediate radiation zone of the receiver increases until the heat fluid reaches the temperature of the intermediate temperature storage tank, and as long as the low temperature tank is not empty and the intermediate temperature tank is not full, the heat fluid is pumped from the low temperature tank, circulating through the circuit of the intermediate radiation zone of the receiver to the intermediate temperature tank; when the radiation in the high radiation zone of the receiver increases until the heat fluid reaches the temperature of the high temperature storage tank, and as long as the intermediate temperature tank is not empty and the high temperature tank is not full, The heat fluid is pumped from the intermediate temperature tank, circulating through the circuit of the receiver's high radiation zone, to the high temperature tank.

In another variant of the procedure, when the operation of the power plant is required for power generation, and provided that:

The high temperature tank contains heat fluid, the boiler contains working fluid,

the low temperature tank is not full of heat fluid,

the condenser is not full of working fluid,

then: the heat fluid is driven from the high temperature tank to the low temperature tank, passing first through the superheater exchanger and then through the evaporator heat exchanger, where it yields heat decreasing its temperature to that of the low temperature tank; the working fluid in a saturated liquid state is driven from the boiler by the evaporator, where it absorbs the heat transferred by the heating fluid by partially evaporating, returning the working fluid to the boiler in the state of liquid-vapor mixture at the same pressure and temperature;

the working fluid in a saturated vapor state circulates from the boiler through the superheater, where it absorbs the heat given by the heat fluid, increasing its temperature at approximately constant pressure to a temperature between 30 oC and 5 oC below the temperature of the hot tank; the working fluid circulating in the form of steam superheated afterwards by the turbine, where its pressure and temperature drops giving energy to the turbine; and flowing the working fluid to the temperature and condensing pressure in the condenser, where it is condensed and stored in the form of saturated liquid.

In another variant of the procedure, when the operation of the power plant is required for power generation, and whenever

intermediate and high temperature tanks contain heat fluid,

the boiler contains working fluid,

Low and intermediate temperature tanks are not filled with heat fluid,

the condenser is not full of working fluid,

so:

the heat fluid is driven from the intermediate temperature tank to the low temperature tank by the evaporator heat exchanger, where it yields heat decreasing its temperature to that of the tank; the working fluid in a saturated liquid state is driven from the boiler by the evaporator, where it absorbs the heat transferred by the heating fluid by partially evaporating, returning the working fluid to the boiler in the state of liquid-vapor mixture at the same pressure and temperature; The heat fluid is driven from the high temperature tank to the low temperature tank by the superheater heat exchanger, where heat is transferred by lowering its temperature to that of the tank;

the working fluid in a saturated vapor state circulates from the boiler through the superheater, where it absorbs the heat given by the heat fluid, increasing its temperature at approximately constant pressure to a temperature between 30 oC and 5 oC below the temperature of the hot tank; the working fluid circulating in the form of steam superheated afterwards by the turbine, where its pressure and temperature drops, giving energy to the turbine; and flowing the working fluid to the temperature and condensing pressure in the condenser, where it is condensed and stored in the form of saturated liquid.

Finally, in another variant of the procedure, when the operation of the power plant is required for power generation, and whenever

intermediate and high temperature tanks contain heat fluid,

the boiler contains working fluid,

low and intermediate temperature tanks are not filled with heat fluid,

the condenser is not full of working fluid,

so:

the heat fluid is driven from the intermediate temperature tank to the low temperature tank by the evaporator heat exchanger, where it yields heat decreasing its temperature to that of the tank; the working fluid in a saturated liquid state is driven from the boiler by the evaporator, where it absorbs the heat transferred by the heating fluid by partially evaporating, returning the working fluid to the boiler in the state of liquid-vapor mixture at the same pressure and temperature;

the heat fluid is driven from the high temperature tank to the intermediate temperature tank by the superheater heat exchanger, where heat is transferred by lowering its temperature to that of the tank;

the working fluid in a saturated vapor state circulates from the boiler through the superheater, where it absorbs the heat given by the heat fluid, increasing its temperature at approximately constant pressure to a temperature between 30 oC and

5 oC lower than the temperature of the hot tank; circulating the working fluid in the form

of steam superheated afterwards by the turbine, where its pressure and temperature drops

giving energy to the turbine; and flowing the working fluid to the temperature and

condensing pressure in the condenser, where it is condensed and stored in

saturated liquid form.

Description of the figures

Figure 1 shows the radiation received, in kW / m2, on the active face of a Fresnel linear collector receiver, the abscissa of the figure being the transverse coordinate of the receiver, with a determined design and for an instant of one day of the year dice.

Figure 2 shows a schematic of a Fresnel linear collector multitube receiver.

Figure 3 shows a scheme of the invention, in which the different components necessary for its operation in a variant of the invention are appreciated.

Figure 4 shows the scheme of the storage load by passing the two fluids through the receiver.

Figure 5 shows the scheme of the discharge of the storage and generation of mechanical power in the turbine.

Figure 6 shows a diagram of another variant of the invention, in which the same components are appreciated, with the only difference that at the outlet of the superheater heat exchanger the heat fluid flows to the intermediate tank, being reused in the evaporator before going back through the receiver to absorb heat.

Figure 7 shows a diagram of another variant of the invention, in which some of the components of the previous schemes are appreciated, with the proviso that there are only two deposits of calorific fluid, one hot and one cold, so that said fluid passes through two heat exchangers in series (superheater and evaporator, in this order, from the hot tank to the cold one) during cooling. In the same way the calorific fluid passes in series through the intermediate and high radiation zones of the receiver from the cold to the hot tank.

Figure 8 shows an interchanged temperature-heat diagram in which the thermal evolution obtained in the invention is compared with that of other commonly used technologies.

In order to facilitate the understanding of the figures of the invention, and of their embodiments, the relevant elements thereof are listed below:

one.

Radiation profile across a given Fresnel receiver, at a given time.

2.

Low radiation zone of the receiver (5), used for preheating the pressurized working fluid to the saturation temperature in the boiler (12).

3.

Intermediate radiation zone of the receiver (5), used to heat the calorific fluid to an intermediate temperature.

Four.

High radiation zone of the receiver (5), used to heat the calorific fluid to the nominal temperature under the typical radiation conditions of the time of the year.

5.

Solar radiation receiver, consisting of tube bundles of low, intermediate and high radiation zones (2, 3 and 4), insulation between zones (6), insulating box (7) and transparent window (8).

6.

Isolation between receiver zones (5) of the low, intermediate and high radiation zones (2, 3, 4).

7.

Insulating receiver drawer (5).

8.

Transparent window of the receiver (5).

9.

Storage tank for heating fluid at low temperature, specifically at a temperature higher than the evaporation of the working fluid and below the maximum temperature of the heating fluid.

10.

Storage tank for calorific fluid at an intermediate temperature between that of the low temperature tank (9) and the maximum temperature of the calorific fluid for the given conditions.

eleven . High temperature heating fluid storage tank, the maximum temperature of the heating fluid being for the given time of year conditions.

12.

Boiler of the steam turbine that serves as the storage of preheated liquid working fluid up to the evaporation temperature, after a variable level.

13.

Condenser of the steam turbine that serves as the storage of saturated liquid working fluid at low pressure after passing through the turbine, then at a variable level.

14.

Shut-off valve of the low radiation zone pickup circuit (2) of the receiver

(5) after the condenser (13).

fifteen.

Shut-off valve of the low radiation zone pickup circuit (2) of the receiver

(5) after this.

16.

Condensate pump of the power cycle, which pressurizes the liquid working fluid from the condensation pressure to the evaporation pressure.

17.

Preheater heat exchanger between the heat fluid coming from the intermediate temperature (10) or high (11) heat fluid reservoir, according to the variant of the invention, and which has just preheated the working fluid to the evaporation temperature if the passing through the receiver would have been insufficient before arriving at the boiler (12).

18.

Shut-off valve of the capture circuit of the intermediate radiation zone (3) of the receiver (5), which allows the passage of heat fluid through said receiver from the low temperature tank (9) to the intermediate temperature tank (10) .

19.

Circulation pump of the collection circuit of the intermediate radiation zone (3) of the receiver (5), which forces the passage of heat fluid through said receiver from the low temperature tank (9) to the intermediate temperature tank (10) .

twenty.

Shut-off valve for the capture circuit of the high radiation zone (4) of the receiver (5), which allows the passage of heat fluid through said receiver from the intermediate temperature tank (10) to the high temperature tank (11) .

twenty-one . Circulation pump of the high collection circuit the high radiation zone (4) of the receiver (5), which forces the passage of heat fluid through said circuit from the intermediate temperature tank (10) to the high temperature tank (11 ).

22

Closing valve of the final preheating circuit, which allows the passage of heat fluid through the preheater heat exchanger (17) from the intermediate temperature tank (10) to the low temperature tank (9).

2. 3.

Circulation pump of the final preheating circuit, which forces the passage of heat fluid through the preheater heat exchanger (17) from the intermediate temperature tank (10) to the low temperature tank (9).

24.

Evaporation circuit circulation pump, which forces the passage of saturated liquid working fluid from the boiler (12) through the evaporator heat exchanger (25) back to the boiler (12), after being partially evaporated.

25.

Evaporator heat exchanger between the heat fluid entering at intermediate temperature, either from the intermediate temperature tank (10) or from the superheater exchanger (30), and partially evaporating the saturated liquid coming from the boiler (12).

26.

Evaporation circuit shut-off valve, which allows the passage of heat fluid through the evaporator heat exchanger (25) from the intermediate temperature tank

(10) towards the low temperature tank (9).

27.

Evaporation circuit circulation pump, which forces the passage of heat fluid through the evaporator heat exchanger (25) from the intermediate temperature tank (10) to the low temperature tank (9).

28.

Shut-off valve of the superheat circuit, which allows the passage of heat fluid through the superheater heat exchanger (30) from the high temperature tank (11) to the low temperature tank (9).

29.

Circulation pump of the superheat circuit, which forces the passage of heat fluid through the superheater heat exchanger (30) from the high temperature tank (11) to the low temperature tank (9).

30

Superheater heat exchanger between the heat fluid coming from the high temperature heat fluid reservoir (11), which overheats the saturated steam coming from the boiler (12).

31. Turbine inlet shut-off valve (32).

32

Turbine of the power cycle of the plant.

33.

Expansion vessel in the low radiation zone (2) of the receiver (5).

3. 4.

Condenser refrigerant circuit (13).

35

Shut-off valve of the superheat circuit, which allows the passage of heat fluid through the superheater heat exchanger (30) from the high temperature tank (11) to the intermediate temperature tank (10)

36.

Circulation pump of the superheat circuit, which forces the passage of heat fluid through the superheater heat exchanger (30) from the high temperature tank (11) to the intermediate temperature tank (10).

37.

Shut-off valve of the superheat and evaporation circuit, which allows the passage of heat fluid first through the superheater heat exchanger (30) and then through the evaporator heat exchanger (25) from the high temperature tank

(11) towards the low temperature tank (9).

38.

Circulation pump of the superheat and evaporation circuit, which forces the passage of heat fluid first through the superheater heat exchanger (30) and then through the evaporator heat exchanger (25) from the high temperature tank (11) to the tank low temperature (9).

39.

Closing valve of the final preheating circuit, which allows the passage of heat fluid through the preheater heat exchanger (17) from the high temperature tank (11) to the low temperature tank (9).

40

Circulation pump of the final preheating circuit, which forces the passage of heat fluid through the preheater heat exchanger (17) from the high temperature tank (11) to the low temperature tank (9).

41.

Shut-off valve for the collection circuit of intermediate (3) and high radiation zones

(4) of the receiver (5), and which allows the passage of heat fluid through the circuit from the low temperature tank (9) to the high temperature tank (11).

42

Circulation pump of the collection circuit of the intermediate (3) and high (4) radiation zones of the receiver (5), which forces the passage of heat fluid through it from the low temperature tank (9) to the temperature tank intermediate (11).

43

Line of preheating, evaporation and overheating of the working fluid of a steam turbine without extractions, represented in an interchanged temperature-heat diagram.

44.

Heat transfer line of a binary molten salt providing heat between its maximum and minimum temperatures to the working fluid of the steam turbine to preheat, evaporate and superheat, represented in a heat-exchanged temperature diagram.

Four. Five.

Heat transfer line of a binary salt that works between an intermediate and minimum temperature to evaporate the working fluid of the steam turbine in an interchanged temperature-heat diagram.

46.

Heat transfer line of a binary salt that works between the maximum and minimum temperatures to superheat the steam before entering the steam turbine (32) in a heat-exchanged temperature diagram.

47

Heat transfer line of a binary salt that works between the maximum and minimum temperatures to evaporate the working fluid and superheat the steam generated before its entry into the steam turbine (32) in a heat-exchanged temperature diagram.

48.

Heat transfer line of a binary salt that works between the maximum and intermediate temperatures to superheat the steam before entering the steam turbine (32) in a heat-exchanged temperature diagram.

Detailed description of an embodiment of the invention

The invention consists in using a multitube receiver (5) in a solar field with non-uniform radiation, so that a high temperature calorific fluid capable of storing thermal energy passes through the central part of the receiver, subject to greater radiation. that through the lateral areas, subject to lower concentrations, the working fluid of the power block (a condensable fluid in its liquid phase) flows, acting as a calorific fluid, heating up to the saturation temperature, and being stored as such in the boiler (12) of said power block. From this moment on, the fluid that circulates through the low radiation zone (2) working fluid will be called, since it is then used directly in the power block, and the fluid that circulates through the intermediate radiation zones (3) and high (4) calorific fluid, being no more than a mere conveyor and accumulator of thermal energy. Thus, the invention comprises the following components:

A multi-tube receiver (5), designed to circulate liquid pumped from the condenser (13) of the cycle from the most lateral to the most central of this area from the condenser (13) of the cycle to the evaporation pressure of the boiler (12), increasing its temperature in the low radiation zone (2) of the receiver (5) to the saturation temperature at said pressure; and for its central tubes to circulate in two circuits, which may be separated or in series, one in the intermediate radiation zone (3) and another in the high radiation zone (4), a heat fluid that acts as thermal storage

Three tanks for the calorific fluid, one smaller than the other two at the maximum attainable temperature, called the high temperature tank (11), one at the minimum fluid operating temperature, called the low temperature tank (9), and another at a temperature somewhat higher than that of saturation in the boiler (12) of the power block, called the intermediate temperature tank (10), the three adequately insulated to prevent freezing. Alternatively, only one high temperature tank (11) and another low temperature tank (9) can be provided, the heat-transfer fluid yielding successively in two heat exchangers (30 and 25) arranged in series.

An evaporator heat exchanger (25) that exchanges heat between the heat fluid entering at intermediate temperature and the saturated liquid phase working fluid from the boiler (12), to be partially evaporated.

An overheater heat exchanger (30) that exchanges heat between the heat fluid, after leaving the hot tank (11), and the evaporated saturated working fluid from the boiler (12).

A preheater heat exchanger (17) that exchanges heat between the heat fluid from the intermediate (10) or high (11) temperature tank and the working fluid, which has been preheated in the low radiation zone (2) of the receiver (5), if the outlet temperature of said zone does not reach saturation at the boiler pressure (12).

A boiler (12) of variable level suitably sized, so that during the day it is loaded with sufficient liquid working fluid saturated at evaporation pressure to operate the power block without solar radiation during the established nominal storage hours .

An appropriately sized variable level condenser (13), so that during the discharge of the storage system the expanded working fluid in the turbine (32) is stored in it in the form of saturated liquid, waiting to be pumped again to heat up in the receiver (5) when there is solar radiation for it.

The invention includes a plurality of shut-off or shut-off valves (14, 15, 18, 20, 22, 26, 28, 31, 35, 37, 39 and 41), in the various branches of the connection circuits between the aforementioned components , so that the heat collection system is closed when there is no solar radiation, the power block can operate independently of the heat collection. To prevent the generation of vacuum in the receiver tubes due to the increase in the density of the working fluid upon cooling, the low radiation circuit is connected to an expansion vessel (33). In addition, the system includes a series of pumps (19, 21, 23, 24, 27, 29, 36, 38, 40 and 42) to force the flow of the fluid through the different components.

In this way both the heat absorption in the receiver (5) and the heat transfer to the working fluid of the steam turbine are sectorized, so that the exergy losses in the different sections of the heat transmission process are minimized, What are they:

The low temperature section, which consists of the passage of working fluid in a liquid state from the condenser (13) of the steam turbine, pressurized by the condensate pump of the power cycle (16) to the evaporation pressure of the cycle , through the low radiation zone (2) of the receiver (5), located on its sides, starting the flow through the tubes or bundles of end tubes and then passing through series in interior areas where its temperature rises to reach the saturation temperature at the boiler pressure (12). At the exit of this circuit, the working fluid will stop at the boiler (12) of variable level, previously passing through the preheater exchanger (17). Said preheater exchanger (17) is fed or not by heat fluid depending on the thermal conditions reached by the working fluid in the low radiation zone (2) of the receiver (5). Thus, in case the radiation in the low radiation zone (2) of the receiver (5) is not sufficient to reach saturation temperature, the fluid is finally heated to said temperature in its heat exchanger passage preheater (17), fed by heat fluid from the intermediate temperature storage tank (10) or, failing that, from the high temperature storage tank (11). The passage of the working fluid through the preheater exchanger (17) when the radiation in the receiver (5) reaches the evaporation temperature, that is, when the preheater exchanger (17) is not fed by heat fluid, can be avoided by a bypass, not shown in the figures, in order not to increase load losses unnecessarily. During the sections of the day in which the radiative power that reaches the receiver (5) is greater than that necessary to operate the cycle in nominal conditions, the working fluid that is preheated to the saturation temperature is greater than that admitted by the steam turbine after being evaporated and overheated in the following sectors, with which the level of liquid fluid in the boiler (12) is increasing. On the contrary, it may be heating less flow

of working fluid in the receiver from which the turbine is being consumed, in which case the liquid level will drop. Finally, if the radiation in the low radiation zone (2) of the receiver (5) does not allow to reach at least a temperature lower than that of saturation at 100 oC, the receiver circuit (5) will be closed by the valves (14 and 15), operating the steam generator from the working fluid stored in the boiler (12) until it reaches its minimum level; in the same way, when the mass flow through the turbine (32) is greater than that of the receiver (5), because the radiation is insufficient or zero, the condensed working fluid will be stored in the condenser (13), which will be level variable, like the boiler (12). The intermediate temperature section, which consists, during the reception of radiation, in the passage of the heat fluid from the low temperature tank (9), at a temperature slightly higher than the evaporation of the working fluid (boiler temperature (12 » , through the intermediate radiation zone (3) of the receiver (5), starting with the lateral tubes of said zone and approaching in series towards the centrals, until reaching a certain temperature, higher than the evaporation temperature and lower than the maximum temperature of the fluid, passing either to the intermediate temperature tank (10) or to the high radiation zone (4) of the receiver (5) During the generation of power, the heat fluid at intermediate temperature, coming either from the intermediate temperature tank ( 10) or directly from assigning heat at a higher temperature in the superheater heat exchanger (30), it is used to transfer heat in the evaporator heat exchanger (25). saturated liquid working fluid taken from the boiler (12) is partially evaporated in said exchanger, and then returned to the boiler (12), where there is liquid-vapor equilibrium; while the heat fluid flows to the low temperature tank (9) once heat has been transferred to the exchanger (25). In parallel there is a branch of calorific fluid from the intermediate temperature tank (10) or high temperature (11) to the low temperature tank (9) through the preheater exchanger (17), which will be open at the time of day in which the radiation in the low radiation zone (2) of the receiver (5) is not sufficient for the working fluid to reach saturation temperature. The heating of calorific fluid in the intermediate radiation zone (3) of the receiver (5) and its cooling in the evaporator and preheater are decoupled, so that each mass flow can be adapted to the radiative power and the needs of electrical power in the turbine (32) respectively. Both circuits, loading and unloading, may be in series with those of high temperature, the intermediate temperature reservoir being unnecessary in the limit (10).

He

stretch high temperature which consists during load, in he step of fluid

calorific from the intermediate temperature tank (10) through the high radiation zone

(4) of the receiver (5), passing first through the side tubes of this area and leaving by

the centrals

to the nominal operating temperature for the working time,

S

Minor that the maximum permissible temperature by the fluid, towards the high tank

temperature (11). The hot circuit is closed at the discharge by extracting

heat fluid from the high temperature tank (11) and its passage through a heat exchanger

superheater heat (30). In said exchanger the working fluid in the form of

saturated steam, which is extracted from the boiler (12), is superheated before entering the

10

turbine steam (32); at the same time the fluid calorific leaves the exchanger

superheater (30), after having ceded heat until reaching an intermediate temperature,

to the intermediate temperature tank (10) or to the heat exchanger

hot

evaporator (24),

according the setting. Again, he heating of the fluid

calorific

in he receiver (5) and the assignment from hot to the steam in he exchanger

fifteen

superheater (30) are decoupled, being able to adapt each mass flow to the

power

radiative Y to the needs from  power electric in the turbine (32)

respectively.

This invention is suitable for concentration solar collectors in which several

20 mirrors located at different distances from the receiver (5) reflect the light on it. Due to the scattering of light, the radiation that reaches the receiver (5) is not constant throughout its surface, but is higher in the center and low in the sides. An example is the radiation that arrives in a Fresnel collector, with the configuration of the Fresdemo prototype built in the Solar Plant of Almería, for an instant of the day, as

25 shows figure 1. In said figure it is observed that the radiation profile (1) in the center becomes 60 kW / m2, while in the lateral part of the receiver it is less than 10 kW / m2. In this way, three zones of low (2), intermediate (3) and high (4) radiation can be defined, which in this figure refer to the areas of the radiation profile (1), and which must then correspond to the same areas of the receiver (5).

A preferred embodiment of the solar receiver (5) is shown in Figure 2. Said solar radiation receiver (5) comprises a plurality of tubes through which two different fluids circulate: a working fluid, which produces power by expanding in the

corresponding turbine (32), and a calorific fluid that serves to accumulate energy in different tanks (9, 10, 11) of the installation.

The solar receiver (5) has a geometric configuration such that the different tubes that run through it receive solar radiation of different radiative intensity, due to the distribution of the radiation that reaches it after reflection in the collector. Thus, there is a first group of tubes that is located in an area called high radiation (4); This zone is characterized in that the radiative intensity at each of its points is greater than the radiative intensity at any point in another zone of the receiver. A second group of tubes is located in an area called low radiation (2), characterized in that the radiative intensity at each of its points is less than the radiative intensity at any point in another area of the receiver. And a third group of tubes is located in an area called intermediate radiation (3), characterized in that the radiative intensity at any of its points is greater than at any point in the low radiation zone (2), but less than from any point in the high radiation zone (4). As can be seen in Figure 2, the low radiation zone (2) is located at the lateral ends of the receiver (5), the high radiation zone (4) is located in the central part of the receiver (5), and the intermediate radiation zone (3) is between the high radiation zone (4) and the low radiation zone (2).

The receiver tubes (5) have a well differentiated design for the low radiation zone

(2) and the areas of intermediate and high radiation (3 and 4), since the first one passes a fluid at very high pressure (50-60 bar) against the slightly higher atmospheric pressure of the calorific fluid in the zones intermediate and high radiation (3 and 4). This means that once the receiver (5) is designed, the low radiation zone circuit (2) cannot be modified. However, by means of collectors at the entrance and exit of the receiver (5) for the other two heating sections (intermediate and high temperature), and three-way valves, the half-radiation circuit can be widened by narrowing the high, and vice versa, storing one type or another of energy according to the radiation of the moment of the day.

As can be seen in Figure 3, the preferred assembly of the invention entails the use of a special two-way steam turbine cycle: on the one hand it is a cycle without extractions, then much simpler than the installed cycles in the current state of the art, they have up to six regenerative extractions for power cycles that

they do not exceed 50 MW. In this way the temperature of the working fluid when entering the receiver (5) is low, which allows to take advantage of the low radiation zone (2), with which one could not reach working temperatures of typical heat fluids such as oils synthetic (300-400 'C) or molten salts (290-565' C). On the other hand, the condenser (t3) and the boiler (12) of the cycle are used as storage of the working fluid in a liquid state that you want to use during moments of the day without radiation; In the case of using a conventional steam turbine without overheating, this translates into an average of 3.6 tons of water per hour of storage and per MW of nominal power. The temperature of the condenser (13) is slightly higher than that of the refrigerant circuit (34), the pressure in the condenser (13) being that of saturation at the temperature of the working fluid in said condenser (13). On the other hand, the temperature and pressure in the boiler (12) are given by the thermal equilibrium in the zone (2) of the receiver (5) and in the evaporator (25), being the pump (16) responsible for pumping the liquid working fluid from the condenser (13) to the boiler (12) through the receiver (5) in moments of radiation, then the valves (14 and 15) are open.

The storage of working fluid in a saturated liquid state in boiler (12) and condenser (13) causes a complication, since its pressures are very different from the atmospheric one (in the case of using a water steam turbine, around 50-90 bar the first, and 0.1 bar the second), which implies non-negligible tensions in these elements. This storage of preheated working fluid saturated at working pressure does not only consist of the storage of the fluid to be used, but it implies 25-40% of the thermal storage of the total of the plant, depending on the existence or not of preheating and evaporation pressure and maximum temperature; said thermal storage is achieved thanks to the fact that it is not necessary to preheat the fluid before evaporating it in the steam turbine cycle, which entails a reduction in the amount of heat fluid (of higher cost) necessary for thermal energy storage thereof order. The fact that the storage of preheated or after expansion working fluid is stored in the boiler (12) or the condenser (13), respectively, is not arbitrary, but is about the two elements of the cycle in which there are a liquid-vapor equilibrium and, therefore, the volume of liquid can be varied without the need for a gas that completes the area not occupied by the liquid at all times. As regards the other fluid that circulates through the receiver, the calorific fluid is stored according to the first variant of the invention (as shown in Figure 4) in three tanks at different temperatures: a first low temperature tank ( 9), at a temperature slightly higher than the temperature of the boiler (12), a second intermediate temperature tank (10), higher in a range between 50 oC and 175 oC than the previous one and a third high temperature tank (11 ), at the maximum temperature attainable by the fluid in the conditions of the year. The low temperature tank (9) must have the capacity to store the heat fluid that fits in the intermediate temperature tank (10) and in the high temperature tank (11), since the heat fluid of both tanks (10 and 11) ) will flow into the first (9) after the heat is transferred to the corresponding heat exchangers (17, 25 and 30), as shown in Figure 5. The heat fluid from the high temperature tank (11) it is used, while the valve (28) is open, to give heat to saturated steam coming from the boiler (12) in the superheater heat exchanger (30), overheating it before entering the turbine (32). The passage of steam through the superheater is given by the difference in pressure between boiler (12) and condenser (13). However, a shut-off valve (31) is necessary to stop and regulate power generation. The heat fluid yields sensible heat, cooling to its minimum temperature (provided that it is higher than the evaporation in the boiler (12)), and being pumped by the pump (29) into the low temperature tank (9). In the case of using molten salts as a calorific fluid and water as a working fluid, the approximate specific heat of the former is 1.5 kJ / kg · K, compared to a specific heat of the water vapor that varies significantly according to the temperature, but which It is between 2 and 4 kJ / kg · K. Adopting a weighted average value of 3 kJ / kg · K, as is the case for a pressure of 60 bar and a maximum superheated steam temperature of 555 oC, and assuming that the increase in steam temperatures is similar to the decrease in temperatures of molten salts, it turns out that the flow rate of calorific fluid is approximately twice the flow rate of steam. In the case of storage, this implies that the mass of calorific fluid stored for the overheating of saturated steam will be approximately twice the preheated liquid water stored in the boiler of variable level, that is, about 7.2 tons per MW and hour of storage. Since the density of molten salts is approximately twice that of saturated water at 300 oC, the previous result implies similar storage volumes for both fluids. Obviously, in the case of choosing to reheat the steam after a first expansion, the flow of calorific fluid is greater by a factor greater than two, the size of the high temperature tank (1 1) being proportionally larger than the average (10) However, since this would imply an improvement in the performance of the steam turbine cycle, the necessary storage volumes per MW and hour of energy produced would be lower.

As for molten salts stored at intermediate temperature, these have a double purpose:

On the one hand, they provide the necessary sensible energy to the preheated working fluid in the receiver if at its output it had not reached the saturation temperature (preheater exchanger 17 in Figure 4); that is to say, it is an exclusive use for times of day during charging in which the energy concentrated in the zones of the intermediate and high radiation receiver (5) (3 and 4) is proportionally larger than the one that affects the Low radiation zone (2) with respect to the design conditions. As it is an occasional use in storage loading, it cannot be coupled to the other intermediate temperature fluid circuit, the valve (22) being the one that allows or not the passage of the heat fluid, which is pumped by the pump (23) from the intermediate temperature tank (10) through the preheater heat exchanger (17), where heat is transferred to the working fluid to its saturation temperature, to the low temperature tank (9). It is therefore not part of the storage system, since preheating does not take place when there is no incident solar radiation in the receiver.

On the other hand, the fluid stored in the intermediate temperature tank (10) has as its main mission to evaporate the saturated liquid working fluid of the boiler (12) in the evaporator heat exchanger (25) during the discharge mode, see figure 5. The flow of working fluid through the evaporator is forced by a pump (24), while the flow of the heating fluid is controlled by a shut-off valve (26) and a pump (27). The working fluid flow through the evaporator (25) and superheater (30) heat exchangers must be such that the mixture in the boiler (12) is maintained at a constant pressure (then temperature) despite possible liquid level changes in loading and unloading. The ratio of mass flow rates of heat fluid flowing through the evaporator

(25) and water that evaporates in it depends on the temperature at which the calorific fluid is in the intermediate tank (10). Taking into account that the enthalpy of water evaporation is approximately 1500 kJ / kg at 290 oC and again assuming molten salts as a calorific fluid (specific heat of 1.5 kJ / kg · K), it turns out that the mass of molten salts that must pass through the evaporator per kg of evaporated water is 1000 / .8.T, where.8.T is the temperature difference between the intermediate temperature tank (10) and the low temperature tank (9). In this way, if a temperature is accepted in the intermediate temperature tank (10) 50 oC higher than that of the cold tank (9), it turns out that the mass to be stored in the first one is 20 times greater than the mass of water preheated stored in the boiler (12). If a higher temperature differential is chosen, for example 100 oC as in the storage of the Andasol plant, one of the first commercial plants with thermal storage, built in Granada (Spain), the mass of molten salts in said Deposit is 10 times higher than that of the variable level boiler (12), 36 tons per MW and storage time. The recommended maximum temperature gradient between the cold tank (9) and the intermediate temperature

(10) is 150 oC for this variant, which implies a storage mass in the intermediate tank (10) of 6.7 times that of the boiler (12), since if it were larger, another variant of the invention would be more appropriate at cost level.

The storage charge circuit is also at three levels of radiation and temperature, as shown in Figure 4. At loading times the valves (14 and 15) are open, allowing the pumping of working fluid in liquid state to the condensing temperature by the pump (16). The working fluid passes first through the outermost tubes of the low radiation zone (2), successively approaching its central tubes as its temperature rises, and through a circuit that crosses the preheater heat exchanger (17) to the boiler (12). The preheater (17) is fed by the heat fluid at intermediate temperature only in case the temperature of the working fluid at the exit of the low radiation zone (2) is lower by more than 5 oC at the saturation temperature a the boiler pressure (12). The mass flow of working fluid through the circuit pumped by the pump (16) may be greater, equal to or less than the mass flow of steam through the turbine (32), depending on the solar radiation existing at that time. If there is no radiation, the valves (14 and 15) are closed, keeping the area of low radiation (2) pressurized. The contractions of the working fluid when lowering its temperature in the absence of radiation are absorbed by the expansion vessel (33).

The section of heat capture at temperature and intermediate radiation consists of pumping by means of the pump (19), after opening the shut-off valve (18), of heat fluid from the low temperature tank (9) through the area of intermediate radiation (3) of the receiver (5), increasing its temperature to the intermediate temperature of the fluid, being taken to the intermediate temperature tank (10). During the hours of the day without radiation, the valve (18) remains closed, prior to emptying the receiver tubes, or a residual flow is maintained to prevent cooling of the fluid below its minimum temperature.

The high temperature and radiation collection section works similarly to the previous one, opening the valve (20) and causing the pump (21) to pump heat fluid from the intermediate temperature tank (10) to the high temperature tank (11) through the high radiation zone (4), in the central part of the receiver (5). In the hours without radiation the same method is used as with the intermediate temperature, either the emptying of the receiver tubes or the maintenance of a residual flow.

The total storage volume of calorific fluid can be reduced with an alternative to the invention, which consists in cooling the calorific fluid in the superheater exchanger (30) only to the temperature of the intermediate tank (10), so that the last cooling section is carried out in the evaporator (25), as can be seen in figure 6. That is, when the valve (35) is open, the pump (36) pumps heat fluid from the high temperature tank (11) to the temperature intermediate (10) through the superheater (30), operating the rest of the installation (evaporation and preheating) in the same way as the first description. Both the volume of the high temperature tank (11) and that of the intermediate temperature (10) depend on the temperature of the second. If it is assumed that it is 100 oC higher than the temperature of the low temperature tank (9), and the assumptions made in the previous examples are maintained, it turns out that the mass of molten salts necessary to overheat a kg of steam is somewhat greater than 3 kg, resulting in a high temperature tank (1 1) with capacity for 11, 3 tons per MW and storage time approximately (assumed without overheating), that is, greater than in the previous variant. On the other hand, the mass of calorific fluid necessary to evaporate a kg of water is the same as for the previous variant of the invention, 10 kg, but the size of the tank will be smaller, since the flow that circulates through the superheater exchanger (30) goes to the intermediate temperature tank (10). In this way the capacity of said deposit (10) must be 36-11.3 = 24.7 tons per MW and storage time. The higher the temperature of the intermediate temperature tank (10), the smaller its size, in exchange for a larger size of the high temperature tank (11).

The limit case occurs for a temperature such that the volume of the intermediate temperature tank (10) is zero. This takes place when the heat flow rate required in the superheater exchanger (30) is the same as in the evaporator exchanger (25), which is equivalent, for the previous example, to a temperature of inlet of the heat fluid to the evaporator exchanger ( 25) 175 oC higher than that of the low temperature tank (9). This leads to a third variant of the invention, which can be seen in Figure 7, which consists of the installation of only two tanks, in addition to the condenser (13) and the boiler (12) of varying heights: a low temperature tank ( 9) and one of high temperature (11), of equal size. According to this variant, when the shut-off valve (37) is open, the pump (38) forces the passage of heat fluid first from the high temperature tank (11) through the superheater exchanger (30) and then through the evaporator exchanger ( 25), being taken to the low temperature tank (9). This reduces the mass of calorific fluid that must be stored with respect to the previous variants, being approximately 5.5 times greater than the mass of preheated water stored in the boiler (12); that is, approximately 19.8 tons per MW and hour of storage. However, all this mass must be stored at its maximum temperature, which worsens the efficiency of the receiver in the heat collection with respect to the other variants.

The benefits of each variant of the invention in terms of exergy losses can be seen in Figure 8. It shows the distance between the preheating, evaporation and overheating line of the working fluid (43) with the cooling fluid heating line according to the different alternatives for assigning heat (45, 46, 47 and 48) in a temperature vs. heat exchanged diagram. The greater the separation between the working fluid heating line and the heating fluid cooling line, the greater exergy losses. As a comparative basis, it can be assumed that the calorific fluid is responsible for carrying out all the heating, from preheating to overheating, as shown in the upper line (44), which requires 30 tons of heat fluid per MW and storage time according to the previous assumptions. This would be the case of the state of the art, such as the aforementioned Andasol solar plant, with the difference that the power block of that plant has six extractions and an overheating, with the preheated water entering the heat exchangers with the heat fluid, which reduces the consumption of molten salts. The invention described here involves a direct preheating of the working fluid to the evaporation temperature, whereby all the alternatives thus reduce the exergy losses. In the first alternative there is an evaporation zone with calorific fluid, which ranges from intermediate to low temperature, line (45), and an overheating zone, in which the calorific fluid decreases its temperature from maximum to minimum, line (46). In the second alternative the only difference is that overheating occurs with a decrease in temperature from the maximum to the intermediate, line (48). Finally, in the third variant, the same flow of calorific fluid passes through the superheater and through the evaporator, the cooling line being the continuation of one another, line (47). The greater the distance between the cooling fluid heating line and the working fluid heating line, the greater the exergy losses. Thus, it is observed that the variants of the invention that imply a lower total use of calorific fluid are those that have more exergy losses, which results in a worse overall system performance.

The percentage of total energy that must be absorbed in each zone depends on the design characteristics of the steam turbine cycle, that is, the cooling temperature (34), the boiler pressure (12), the inlet temperature at the turbine and the existence or not of an intermediate reheating; as well as the storage design characteristics, which become the variant of the chosen invention and the temperatures of each of the calorific fluid storage tanks.

The low radiation zone (2) of the receiver (5) must absorb the energy necessary to heat the working fluid from the temperature in the condenser (13) to the temperature in the boiler (12). This implies between 25% and 40% of the total energy that the working fluid must absorb, admitting that it is water and that the maximum temperature varies between 390 oC and 555 oC, with or without overheating. Thus, the width of the low radiation zone (2) must be such that the incident energy is in that percentage range with respect to the total energy incident in the receiver (5).

The width of the intermediate radiation zone (3) of the receiver (5) depends not only on the configuration of the steam turbine cycle, but also on the variant of the invention. In any case, the percentage of energy required to overheat the working fluid with respect to the total energy absorbed by it is in the range of 13% to 24% if there is no overheating, and from 18% to 37% if there is. , both for the maximum range and temperatures of 380 oC to 555 oC. However, in case of using the variant of the invention observed in Figure 3, since the heating fluid is heated in the high radiation zone (4) only from the temperature of the intermediate temperature tank (10) to that of the tank high temperature (11), while cooling in the superheater exchanger (30) cools down to the temperature of the low temperature tank (9), the percentage of energy to be absorbed in the high radiation zone (4 ) may be less than the percentage of energy needed to overheat.

5 If another variant of the invention is used, these numbers would coincide. It follows that the width of the high radiation zone (4) of the receiver (5) must be such that the energy absorbed in said zone is between 5% and 35% of the total energy absorbed in the receiver (5 ).

The present invention should not be considered limited by the particular embodiment described herein. Those skilled in the art may be able to obtain other configurations in view of the present description. Therefore, the scope of protection of the invention is defined by the following claims.

Claims (1)

1-Concentration thermosolar center, which follows a cycle of condensed fluid power and comprises: a steam turbine (32) and a hydraulic pump (16); a multi-tube solar radiation receiver (5); a boiler (12) of variable level, which acts as a boiler of the cycle and storage of a saturated working fluid at the evaporation pressure of the cycle; a capacitor (13) of variable level, which acts as a cycle condenser and storage of saturated working fluid at the condensation pressure of the cycle; a thermal energy storage system in a heat fluid with at least two temperature levels, with a low temperature tank (9) and another high temperature tank (11); at least three heat exchangers of the calorific fluid with the working fluid: a preheater (17), an evaporator (25) and a superheater (30); There is a plurality of hydraulic connections between the previous elements,  characterized by: Two different fluids, a working fluid, circulate through the multitube receiver (5). produces power by expanding in the turbine (32), and a heat fluid that serves to accumulation of energy in different tanks (9 and 11) of the installation; and the receiver (5) consists of three radiation concentration zones: a first low radiation zone (2), so that the radiative intensity at each of its points is less than at any point of the receiver (5) not belonging to the low radiation zone (2); a second high radiation zone (4), such that the radiative intensity at each of its points is greater than at any point of the receiver (5) not belonging to the zone high radiation (4); and a third intermediate radiation zone (3) between the low radiation zone (2) and the high radiation zone (4), so that the radiative intensity at any of its points is greater than the radiative intensity at any of the points in the low radiation zone (2), but less than in those of the high zone radiation (4); the working fluid circulates through the tubes of the low radiation zone (2), and through the tubes the fluid circulates from the high radiation zone (4) and from the intermediate radiation zone (3) calorific, so that: or through the zone (2) of low radiation of the receiver (5) the working fluid circulates in liquid state at the evaporation pressure of the cycle, increasing its temperature to, at most, the saturation temperature at said pressure; or fiuido circulates through the intermediate (3) and high (4) radiation zones of the receiver (5) calorific, increasing its temperature to its maximum working temperature for the maximum concentrations of the time of the given year. 2-Concentration thermosolar center according to claim 1, characterized in that the low radiation zone (2) is located on the sides of the receiver (5); the high radiation zone (4) is in the central zone of the receiver (5); Y the intermediate radiation zone (3) is between the low radiation zone (2) and the high radiation zone (4). 3-Concentration thermosolar center according to any of the preceding claims, characterized in that it comprises valves (14 and 15) and an expansion vessel (33) in the circuit of the low radiation zone (2) of the receiver (5), so that the valves (14 and 15) open and close and the hydraulic pump (16) is activated and deactivated depending on the radiation received in the low radiation zone (2) of the receiver (5); The expansion vessel (33) allows expansions and contractions of the working fluid in the circuit due to temperature changes in case of valves (14 and 15)  closed. 4 -Central thermos concentration alarm according to any one of the preceding claims, characterized in that there is at least one storage tank (10) for heating fluid, at an intermediate temperature between the temperatures of the first tank (9) and the second tank (11) calorific fluid storage. 5 -Central solar concentration center according to any of claims 1 to 3, characterized in that it comprises: a plurality of cutting or closing valves (14, 15, 31, 37, 39 and 41) in the various connection circuits between the two storage tanks (9 and 11) and the boiler (12), the turbine (32) , the condenser (13) and the condensate pump (16), and the receiver (5) and heat exchangers (17, 25 and 30); a plurality of flow drive pumps (24, 38, 40 and 42); so that said valves (14, 15.31, 37.39 and 41) and said pumps (24.38, 40 and 42) they are activated and deactivated depending on the radiation received in each zone (2, 3 and 4) of the receiver (5) depending on the radiation received. 6 - Thermosolar concentration center according to claim 4, characterized in that it comprises: a plurality of shut-off or shut-off valves (14, 15, 18, 20, 22, 26, 28, 31 and 35) in the various connection circuits between the three storage tanks (9,10 and 11) AND the boiler (12), the turbine (32), the condenser (13) and the condensate pump (16), and the receiver (5) and heat exchangers (17, 25 and 30); a plurality of flow discharge pumps (19, 21, 23, 24, 27, 29 and 36); so that said valves (14, 15, 18, 20,22,26, 28, 31 and 35) and said pumps (19,21, 23, 24, 27, 29 and 36) are activated and deactivated depending on the radiation received in each zone (2, 3 and 4) of the receiver (5) depending on the radiation received. 7 -Procedure of operation of a concentration solar thermal power plant according to any of the preceding claims characterized in that when the radiation in the Low radiation zone (2) of the receiver (5) reaches a temperature in the working fluid of at least 100 oC below the temperature in the boiler (12), and provided that the condenser (13) is not empty and the boiler (12) is not full, the working fluid is pressurized from the 'condensing pressure in the condenser (13) to the pressure of evaporation in the boiler (12), being pumped at said liquid pressure from the condenser (13) to the boiler (12) by the circuit of the low radiation zone (2) of the receiver (5). 8 -Procedure of operation of a solar thermal power plant according to claim 7 characterized in that: when the temperature reached by the working fluid in the low zone circuit Radiation (2) of the receiver (5) is less than that of saturation at the pressure of the boiler (12), Calorific exhaust is pumped from the high temperature tank (11) to the low temperature tank (9) by the heat exchanger preheater heat (17), where heat yields lowering its temperature until reaching the temperature of the tank (9); and the working fluid circulates in a liquid state from the low radiation zone (2) of the receiver (5) to the boiler (12) through the preheater (17), where it absorbs the heat transferred by the heat fluid increasing its temperature to the boiler temperature (12), which is the saturation temperature at the evaporation pressure of the cycle. 9 -Procedure of operation of a concentration solar thermal power plant according to claim 7 characterized in that: when the temperature reached by the working fluid in the low zone circuit radiation (2) of the receiver (5) is less than that of the pressure saturation of the boiler (12), pumps heat fluid from the intermediate temperature tank (10) to the tank low temperature (9) by the preheater heat exchanger (17), where heat yields decreasing its temperature until reaching the temperature of the tank (9); and the working fluid circulates in a liquid state from the low radiation zone (2) of the receiver (5) to the boiler (12) by the preheater (17), where it absorbs the heat transferred by the heat fluid by increasing its temperature to the boiler temperature (12), which is the saturation temperature at the evaporation pressure of the cycle. 10 -Procedure of operation of a concentration solar thermal power plant according to any of claims 7 or 8 characterized in that when the radiation in the intermediate radiation zone (3) already ". (4) of the receiver (5) increases until the fluid heat reaches the temperature of the high temperature storage tank (11), and as long as the low temperature tank (9) is not empty and the high temperature tank (11) is not full, the heat fluid is pumped from the low temperature tank (9), first circulating through the circuit of the intermediate radiation zone (3) of the receiver (5) and then through the circuit of the high radiation zone (4) of the receiver (5), to the tank at a "temperature (11). 11 -Procedure of operation of a solar thermal power plant according to any of claims 7 or 9 characterized in that: when the radiation in the intermediate radiation zone (3) of the receiver (5) increases until the heat fluid reaches the temperature of the storage tank of intermediate temperature (10), and provided that the low temperature tank (9) is not empty and that the intermediate temperature tank (10) is not full, the heating fluid is 33 pumped from the low temperature tank (9), circulating through the area circuit intermediate radiation (3) from the receiver (5) to the intermediate temperature tank (10); when the radiation in the high radiation zone (4) of the receiver (5) increases until the heat fluid reaches the temperature of the high temperature storage tank (11), and as long as the intermediate temperature tank (10) is not empty and the high temperature tank (11) is not full, the heat fluid is pumped from the intermediate temperature tank (10), circulating through the circuit of the zone of high radiation (4) from the receiver (5), to the high temperature tank (11). 12 -Procedure of operation of a solar thermal power plant according to any of claims 7 to 11 characterized in that: when the operation of the plant is required for power generation, and always that the high temperature tank (11) contains heat fluid, the boiler (12) contains working fluid, the low temperature tank (9) is not filled with heat fluid the condenser (13) is not full of working fluid,  so the heat fluid is driven from the high temperature tank (11) to the low one temperature (9) passing first through the superheater exchanger (30) and then through the evaporator heat exchanger (25), where it yields heat decreasing its temperature to that of the tank (9); the working fluid in an illiquid or saturated state is driven from the boiler (12) by the evaporator (25), where it absorbs the heat given off by the heat fluid evaporating partially, returning the working fluid to the boiler (12) in a state of liquid mixing steam at the same pressure and temperature;

-

_ the working fluid in a state of saturated steam circulates from the boiler! (12) through the worker heater (30), where it absorbs the heat ceded by the heat fluid by increasing its temperature at approximately constant pressure to a temperature between 30 'C and 5 'C below the temperature of the hot tank (11); the working fluid circulating in the form of steam superheated afterwards by the turbine (32), where its pressure and temperature drops giving energy to the turbine (32); and flowing the working fluid to the

3. 4 condensing temperature and pressure in the condenser (13), where it is condensed and stored in the form of saturated liquid. 13 -Procedure of operation of a concentration solar thermal power plant according to any of claims 7 to 11 characterized in that when the operation of the plant is required for power generation, and always that intermediate (10) and high (11) temperature tanks contain heat fluid, the boiler (12) contains working fluid, the low temperature (g) and intermediate (10) tanks are not filled with heat fluid, the condenser (13) is not full of working fluid,  so: the heat fluid is driven from the intermediate temperature tank (10) to the of low temperature (9) by the evaporator heat exchanger (25), where it yields heat decreasing its temperature to that of the tank (9); the working fluid in a saturated liquid state is driven from the boiler (12) by the evaporator (25), where it absorbs the heat ceded by the heat fluid by evaporating partially, returning the working fluid to the boiler (12) in a state of liquid mixing steam at the same pressure and temperature; the heat fluid is driven from the high temperature tank (11) to the low one temperature (9) by the superheater heat exchanger (30), where heat yields decreasing its temperature to that of the tank (10); The working fluid in a state of saturated steam circulates from the boiler (12) through the superheater (30), where it absorbs the heat ceded by the heat fluid, increasing its temperature at approximately constant pressure to a temperature between 30 'C and 5'C lower than the temperature of the hot tank (11); circulating working fluid in the form of steam superheated afterwards by the turbine (32), where its pressure drops and temperature giving energy to the turbine (32); And flowing the working fluid to the temperature and pressure of condensation in the condenser (13), where it is condensed and stored in the form of saturated liquid. 14 -Procedure of operation of a solar thermal power plant according to any of claims 7 to 11 characterized in that when the operation of the power plant is required for power generation, and whenever intermediate (10) and high (11) temperature tanks contain heat fluid, the boiler (12) contains working fluid, the low temperature (9) and intermediate (10) tanks are not filled with heat fluid, the condenser (13) is not full of working fluid,  then: the heat fluid is driven from the intermediate temperature tank (10) to the of low temperature (9) by the evaporator heat exchanger (25), where it yields heat decreasing its temperature to that of the tank (9); The working fluid in a saturated liquid state is driven from the boiler (12) by the evaporator (25), where it absorbs the heat transferred by the heat fluid by partially evaporating, returning the working fluid to the boiler (12) in a liquid mixing state. steam at the same pressure and temperature; The heat fluid is driven from the high temperature tank (11) to the intermediate temperature (10) by the superheater heat exchanger (3D), where yields heat by lowering its temperature to that of the tank (10); the working fluid in a state of saturated steam circulates from the boiler (12) through the superheater (30), where it absorbs the heat ceded by the heat fluid by increasing its temperature at approximately constant pressure to a temperature between 30 oC and 5 oC lower than the temperature of the hot tank (11); the working fluid circulating in the form of steam superheated afterwards by the turbine (32), where its pressure and temperature drops, giving energy to the turbine (32); And flowing the working fluid to the Condensation temperature and pressure in the condenser (13), where it is condensed and stored as a saturated liquid. 36