JPS5948311B2 - solar power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar thermal power generation plant, and particularly to its system configuration and control method.

A solar thermal power generation plant is a plant that converts sunlight energy into electrical energy via thermal energy.

The solar energy obtained on the ground is affected by the weather, and it is not possible to expect to obtain steady thermal energy; rather, it may repeat sudden changes in density and density, so it is impossible to directly apply sudden thermal fluctuations to the power generation system. Can not.

Furthermore, sunlight cannot be obtained at all at night, and power generation cannot continue at night without some kind of countermeasure.

In order to deal with this problem, a heat storage system is installed between the condensing heat collector system and the power generation system, and a part of the collected heat is stored when the solar radiation conditions are good, and the heat storage system is used when the solar radiation conditions are poor. Conventionally, methods have been considered to continue generating electricity by extracting heat from the system.

FIG. 1 is a schematic system diagram of a conventionally proposed solar thermal power generation plant with the greatest feasibility.

Water is used as the heat collection working medium (hereinafter referred to as the medium) that collects heat from sunlight in this plant and drives the turbine 4, and a latent heat type molten salt heat storage device (hereinafter referred to as the heat storage device) that uses molten salt as a heat storage material. )2 For example, potassium fluoride-lithium fluoride-thorium fluoride (KF-L, iF-NaF, mixing ratio 42-46.5-11.5 mo1%, melting point 454°C
, latent heat of fusion 95 kcal/'kg) or salt, potassium chloride-lithium chloride (KCI-LiC'l, mixing ratio 41
．． Molten salts having a melting point slightly higher than the main air temperature of the steam turbine are used as heat storage materials.

-7 The operation control method of this power generation plant is as follows:
50-10 below the melting point of the heat storage material of heat storage device 2.
It is heated to a high temperature of 0° C., passed through a heat storage device 2, and stores the amount of heat up to the melting point of the heat storage material as latent heat of fusion of the heat storage material, and further drives the turbine 4 to obtain power generation output from the generator 5.

When solar radiation conditions are good and the amount of heat collected is greater than the load on the generator 5, the amount of water supplied to the collector 1 is increased and the excess steam is transferred to the output of the heat storage type 2 from the steam pipe 1. At 18, the hot water is led to the accumulator 3 and stored as compressed water.

On the other hand, if the solar radiation conditions are bad and the amount of heat collected is less than the load of the generator 5, the amount of water supplied to the collector 1 is reduced and the steam shortage is generated by adjusting the control valve 10 to reduce the pressure in the accumulator 3. The saturated steam is guided to the heat storage device 2 population side through the steam pipe 19, passes through the heat storage device 2 together with the steam from the condenser collector 1, and is heated to the same temperature as the melting point of the power heat storage material using the latent heat of fusion of the heat storage material. supply to.

Further, when a power generation output is required when there is no solar radiation, all the required amount of steam is reinforced by the accumulator 3 and superheated into steam by the heat storage device 2 to drive the turbine 4.

Steam discharged from the turbine 4 is cooled and condensed in a condenser 6, and sent to a concentrator 1 by a water supply pump 7 for recirculation.

In this way, the heat storage system consisting of the accumulator 3 and the heat storage device 2 absorbs fluctuations in the amount of heat collected due to changes in the amount of solar radiation and operates the plant according to the demands of the load. It has been proposed to control the power to the same temperature as the melting point of the heat storage material, and to prevent sudden thermal fluctuations from being caused to the turbine 4.

However, upon careful consideration, it is clear that even in such conventional plants, the temperature of the steam at the exit of the heat storage system fluctuates greatly, and there is a risk of rapid thermal fluctuations occurring in the power generation system.

This shortcoming can be explained using the trial design of a power generation output IMW plant as an example.
This will be explained using the calculation results of the driving characteristics.

Table 1 shows a trial design of an IMW solar thermal power generation plant and its general specifications.

The design conditions were such that the installation location was Kagawadoko, and the solar and heat collector system was designed to produce IMW power generation output when the solar radiation intensity was 0.75kW/m2 two hours after the midpoint of the vernal equinox. .

Concentrating heat collectors include tower concentrating method, power mullet concentrating method, and
There are a combination of plane mirror and parabola, and a combination of plane mirror and parabola.

Turbine main steam conditions are pressure 14ata, temperature 343℃
And so.

In consideration of main steam conditions, the heat storage device has a hot water storage pressure (working pressure range) of 18 to 40 ata in the accumulator, and the molten salt pressure accumulator has the above-mentioned KC, which has a melting point of 354°C.
Calculations were made using a capsule-type heat storage device in which l-LiC1 was used as a heat storage material and the heat storage material was sealed in a small sealed container.

The heat collecting temperature of the light collector was set to 420° C., which is 66° C. higher than the melting point of the KCI-LiC1 heat storage material.

In addition, the heat storage capacity of the heat storage device was such that it could generate rated IMW power for about 4 hours at maximum heat storage.

The mechanical specifications of the IMW solar thermal power generation plant, which were trial designed under these conditions, are as shown in Figure 2.
Plane mirror area) 11,600 m2, heat collected steam volume at rated time (=
Main steam amount) 6200 kg/h.

The total volume of the accumulator is approximately 272 m3, and the maximum is 219 m3.
It is possible to store tons of hot water.

The molten salt heat storage device has a scale in which about 20 tons of KCl-LiC1 heat storage material is sealed in 479 capsules with an outer diameter of 48.6 mm and an effective heat transfer length of 16 m, and is capable of storing about 4300 Mcal of heat.

The operating characteristics of this plant, especially the followability of the heat storage device, will be calculated based on actually measured solar radiation conditions, and its shortcomings will be clarified.

In this calculation, the Monte Carlo method was used for the concentrating heat collector, and the finite difference method was used for the molten salt heat storage device and accumulator.

Figure 2 shows the variable names for the calculations shown below, each having the following meanings.

φ8: Direct solar radiation (kW/m2) Go: Amount of heat collected steam (kg/h) Value when heat collection conditions are controlled to 40a ta, 420℃ GH: Amount of steam passing through the molten salt heat storage device (kg/h) -G.

+GAou1G□: Turbine required steam amount (kg/h)
GA: Accumulator hot water storage amount (tons) GAin: Accumulator inflow steam amount (kg/h) G
AOut: Accumulator release steam amount (kg/h) TH
, n: Molten salt heat storage inlet steam temperature (°C) T, 4°ol:
Molten salt heat storage outlet steam temperature ('C) T□: Main steam temperature ('C) PA: Accumulator hot water storage pressure (ata) QH: Molten salt heat storage remaining heat storage amount (Meal) Pw: Power generation output request value (k
W) Figure 3 shows IMW solar power generation plan I based on the trial design.
The followability of the heat storage device is calculated based on the experimental value of solar radiation φ8 on September 278, 1977 at the assumed installation location, and when the required power generation output value Pw is assumed to be as shown in the figure and operated.

In addition, at the end of the previous H power generation, the heat storage device has enough heat storage to enable the rated IMW power generation for about 1.3 hours. At the end of the current generation, we decided to leave the same amount of heat for the next generation.

That is, if there is the same amount of solar radiation φ on consecutive days, it is possible to obtain a power generation output of BP on consecutive days.

Power generation will begin at 7:30.

At the beginning of operation, the amount of solar radiation φ8 is small, so the amount of collected steam G
.

There are also few.

It increases as time passes and decreases again in the afternoon.

The main steam amount G1 is the required amount of steam to satisfy the power generation output request value PW.

The operation of the accumulator is determined by the relationship between the amount of collected steam Gc and the required amount of main steam G It is supplied to the accumulator from the -1 side.

Conversely, if the required amount of main steam G□ is greater, the shortage (GA
Out ``' GT ''' Go) is replenished from the accumulator.

However, in this calculation example, the required amount of main steam G□ is large at startup in the morning, so steam is released from the accumulator (GAOLI
υ will be

However, when it is in the mouth, the amount of collected steam GC is large, so it is stored in the accumulator. Steam is released from the accumulator again in the evening.

However (in 7, the accumulator hot water storage pressure PA and the hot water storage amount GA change depending on the steam flow to the accumulator, and the end of power generation r
At 7:30 p.m., it will be in a PC state compared to when it started at 7:30.

On the other hand, the amount of steam passing through the molten salt heat storage device GH is j′ if there is no steam release from the accumulator, all of the collected steam is present, and when there is steam release from the accumulator, the mixed steam of the collected steam and the steam released from the accumulator is: When the condensing heat collector is not operated, only the steam released from the accumulator passes through, stores or absorbs heat depending on the relationship between the inflow steam temperature and the heat storage temperature, and is supplied to the turbine.

However, at 7:30 when the plant was started up, the collected steam at 420°C and the steam released from the accu-j and the rotor merged, and -
The heat storage material melting point is 35 when supplied at 260℃ (Tl(ir,)
Heated to 4°C (THou, ).

■As the withstand capacity φ8 increases, the amount of collected steam GC increases (the amount of steam released from the accumulator decreases), and the inflow temperature TI gradually increases.
(ir increases.

Since there is no steam released from the accumulator after 8:15 p.m., collected steam at 420°C flows in, radiates heat to the heat storage device, and is released at approximately 354°C.

Moreover, after 15:30, the inflow temperature T, □ due to re-steam release from the accumulator.

7, and after 17, only the steam released from the accumulator flows in, but is heated to -354°C.

In other words, the inflow temperature T, 1, □ is higher than the outflow temperature 'rHOr
, 1 indicates the time when heat is being stored in the heat storage device, and the location where the inflow temperature is lower indicates the time when heat is released from the heat storage device.

Due to repeated heat storage and heat radiation, the amount of heat stored in the heat storage device, Q, increases by 1.
Or it decreases and the plant stops at 19:00 and starts at 7:00;
The temperature is the same as the heat storage state for 30 minutes.

The shortcomings of the conventional plant appear in this calculation result.

In other words, when the heat storage unit is discharged at around 10:20, the steam temperature TI
(At 01 Jt, despite the increase in heat storage Q,
It has risen to C.

Since the steam flowing out of the heat storage device is directly supplied to the turbine, the main steam temperature 'r1, is equal to the heat storage temperature [-1 steam temperature 'l[
'Varies depending on HOLlt.

In other words, in the conventional Buran I, the main steam temperature may fluctuate to a large extent, causing large thermal fluctuations in the turbine.
It is clear that there is a risk of

Output of the heat storage ['steam temperature T,.

The reason why Y fluctuates in this way will be explained in detail with reference to FIG.

FIG. 5 shows the heat storage material temperature distribution (solid line) inside the heat storage device and the steam temperature distribution (dashed line) at each time in the above operation characteristic calculation.

At startup at 7:30, the heat storage type is turned on due to the heat dissipation from the evening of the previous day.
” side is low temperature (about 220℃), and the output L-1 side is high temperature (about 35℃).
4°C).

Therefore, the inflowing low-temperature steam at this time is heated in the middle part of the heat storage 15.

At around 9 o'clock, the temperature of the incoming steam reaches 420°C, and heat is stored in the low-temperature heat storage material on the inlet side.

By storing heat, the temperature of the steam itself decreases to about 300°C, but it is heated to about 354°C by the heat storage material on the downstream side.

In other words, during this time storage, heat is stored as a whole, but heat is stored on the large LJ side of the heat storage device, and heat is radiated on the exit side.

Accordingly, the lowest temperature part (2) of the heat storage device gradually decreases and gradually moves to the downstream side.

However, after 9 o'clock, the influence of the low temperature zone (2) appears on the outflow steam temperature, which drops to about 320°C by 10:20.

On the other hand, during L1, heat is stored by collected steam at 420℃,
The number of high-temperature parts (■) at 420°C will gradually increase in the heat storage unit.

When the temperature of the incoming steam drops after 3:00 pm, it is heated by the heat storage material near the inlet and rises to 420℃, and on the outlet side, the steam gives heat to the heat storage material and is released at 1.354℃. .

That is, during this time period, the high temperature part (2) gradually decreases and gradually moves to the downstream side.

However, at 17:00, the effect appears on the outlet side of the heat storage device, and the temperature of the outflow steam reaches approximately 370°C.

As explained above using the trial design and operation characteristic calculation results of an IMW solar power generation plant as an example, in conventional plants, the main steam temperature fluctuates widely, which may cause large thermal fluctuations to the turbine.

Furthermore, there are drawbacks that greatly affect the lifespan, safety, etc. of the plant.

An object of the present invention is to eliminate the drawbacks of the conventional solar thermal power generation plants and to provide a solar thermal power generation plant that can operate stably by controlling main steam conditions to a constant level.

The purpose of this is to install a heat collecting working medium temperature detector on the outlet side of the pressure accumulator, and to supply a heat collecting working medium with a higher temperature than the outlet side of the condensing heat collector between the temperature detector and the outlet side of the heat accumulating device. Piping that leads to
Separately, a pipe for guiding a low temperature heat collecting working medium is provided, and the high temperature heat collecting working medium or the low temperature heat collecting working medium is supplied to the heat collecting working medium on the outlet side of the heat storage device according to the temperature detected by the temperature detector. , achieved by a solar thermal power plant with constant control of the temperature of the collecting working medium entering the turbine.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

Water is used as the heat collection working medium in this embodiment, and the heat storage device consists of a potassium chloride-lithium chloride (KCI-LiC1) molten salt heat storage device 2 and an accumulator 3 similar to the conventional example shown in FIG. .

In FIG. 5, the same numbers as those in the conventional example in FIG. Concentrator 1 between the 18 branch points
A steam pipe 16 having a control valve 11 is provided on the way to guide high-temperature medium vapor from the outlet side of the steam pipe, and a control valve 14 is provided on the way to guide the discharged steam of the accumulator 3 between the control valve 13 and the temperature sensor 15. A steam pipe 17 having a diameter is provided.

A control valve 12 is also provided between the inlet side of the heat storage device 2 and the confluence point of the main steam pipe 19 of the accumulator 3.

The operation control system of this embodiment is the same as the conventional example shown in FIG. 1 in its main parts.

The control of this embodiment is performed when the temperature of the outflow steam of the heat storage device 2 fluctuates from the set temperature (which is the melting point of the heat storage material), which is a drawback of the conventional example.

That is, the temperature detector 15 constantly monitors the main steam temperature, and when the main steam temperature falls below the set temperature (for example, around 10 o'clock in FIG. 3), the control valve 11 of the steam pipe 16 is adjusted to collect the high temperature. The hot steam is guided to the outlet side of the heat storage device 2, and the main steam temperature is adjusted to the set temperature.

In this case, the reason why the confluence point of the steam pipes 16 is placed downstream of the branch point of the steam pipes 18 to the accumulator 3 is to avoid wasteful heating of the steam stored in the accumulator 3.

On the other hand, when the main steam temperature rises above the set temperature (for example, around 17:00 in Fig. 3), the control valve 1 of the steam pipe 17
4, the steam released from the accumulator 3 is guided to the outlet side of the heat storage device 2, and the main steam temperature is adjusted to the set temperature.

In this way, the main steam temperature can always be adjusted to the set temperature.

The effects of this embodiment will be explained using as an example the results of calculation of driving characteristics under the same conditions as the conventional example.

Figure 6 shows variable names for the calculations shown below, and the same symbols as in Figure 2 have the same meanings.

The two new variables have the following meanings.

GCb: Amount of collected steam (kg/h) supplied from the heat collector to the outlet side of the heat storage unit through the steam pipe 16; GA: Quantity of collected steam supplied from the accumulator to the outlet side of the heat storage unit through the steam pipe 17. Amount of released steam (kg/h) FIG. 7 shows the calculation results of the operating characteristics of this example under the same conditions as described above.

The set temperature of the temperature detector 15 was set to the melting point of the KCl-LiC1 heat storage material, 354°C.

Solar radiation amount φ5, heat collected steam amount G.

, power generation output request value PW, required steam amount G, 1~ are the same calculation conditions as in FIG. 3.

Outlet steam temperature THo1 of heat storage device 2. ．． The temperature gradually decreases after 9:00 and reaches around 320°C by around 10:30.

However, the temperature detector 15 detects a temperature change, and the control valve 11 is actuated in response to the signal to reduce the required amount of molten salt heat storage bypass flow rate G.

b flows, joins with the steam that has passed through the molten salt heat storage, increases its temperature, and the main steam temperature T□ entering the turbine is maintained at the set temperature of 354°C.

On the other hand, around 17:20, the molten salt heat storage outlet steam temperature THOut rises to a maximum of 370°C, but as above, the temperature detector 15 detects this temperature change, and in this case, it is higher than the set temperature. , the control valve 14 at the accumulator outlet is activated, low-temperature steam (flow rate GAB) merges with the steam that has passed through the molten salt heat storage, and the main steam temperature is regulated as shown by T1 in the bottom row of Figure 8. is kept constant.

In particular, the steam turbine is the main equipment in a power generation plant, and a core change or a large change in the main steam temperature [-1J] leads to an increase in thermal stress and, therefore, a decrease in service life.

Since the main steam temperature can be maintained constant according to the present invention, the life of the steam turbine can be extended and reliability can be improved.

FIG. 8 shows another embodiment of the present invention, in which the same numerals as in the embodiment of FIG. It does not have 13.

A desuperheater 2 is installed between the temperature detector 15 and the confluence of the steam pipe 16.
4, and a control valve 23 is provided on the way to guide the low temperature condensate of the heat advancing working medium (low temperature water in this case) cooled and condensed by the condenser 6 from the outlet side of the water supply pump 7 to the attemperator. A piping 25 is provided, and when the steam temperature THOu at the outlet of the heat storage device rises to about 370° C. as in the previous embodiment, low temperature water is guided to the desuperheater 24 according to the detection by the temperature sensor 15. The main steam temperature T1 is controlled to a constant set temperature of 354° C. by contacting with the child steam.

As described in detail above, the present invention has the effect of eliminating the drawbacks of conventional solar thermal power generation plants, controlling the main steam temperature at a constant level, and enabling stable operation of Plan I.

Although the present invention has been specifically described with respect to its embodiments, various modifications are possible within the technical scope of the present invention.

For example, the condenser 1 may be a tower condensing type, a parabola condensing type, a convex lens condensing type, a Fresnel lens condensing type, etc., instead of a plane mirror/parabola combination type, and the heat storage device is a KCl-LiC1 molten salt, Instead of a heat storage device, it may be another molten salt heat storage device, another latent heat type heat storage device, or a sensible heat type heat storage device.

Furthermore, the heat collecting working medium may not be water, but may be another different medium.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional solar thermal power generation plant;
The figure shows the variable names for the calculation of blunt operating characteristics in the conventional plan I. Figure 3 is a chart of the calculation results of the operating characteristics of the conventional plant shown in Figure 1. Figure 4 is the molten salt heat storage type in the calculation of Figure 3. Figure 5 is a schematic system diagram of an embodiment of the present invention, Figure 6 is a diagram showing the names of variables used in calculating the operating characteristics of this embodiment, and Figure 7 is a diagram showing changes over time in internal temperature distribution. FIG. 8 is a schematic system diagram of another embodiment of the present invention. 1... Light collector, 2... Molten salt heat storage device, 3... Accumulator, 4... Turbine, 5... Generator, 6...Condenser, 7...Water pump, 8 to 14, 23...
... Control valve, 15 ... Temperature detector, 16 to 19 ... Steam pipe, 24 ...
・Desuperheater, 25...Piping.

Claims (1)

[Claims] 1. A solar collector that collects solar heat and heats a heat collecting working medium/7 [1] and collects solar energy as thermal energy, and a heat storage device that stores a part of the collected heat energy.
A solar thermal power generation plan I having a turbine for converting heat and energy into electric energy/and a generator driven by the turbine, the exit side of the heat storage device and the generator The heat collecting working medium temperature detector installed between the A pipe leading to a thermal working medium, another pipe leading to a low-temperature heat-collecting working medium, and a controller 1 provided in each of the two pipes.
a solar thermal power generation device, wherein the control I/roll valve is controlled in response to a signal from the heat collecting working medium temperature detector to keep the temperature of the heat collecting working medium entering the turbine constant. plant.