RU2300058C2 - Cylindrical parabolic sun energy concentrator with absorber and sun tracking system - Google Patents

Abstract

FIELD: solar power engineering, possible use in broad range depending on working area of concentrator, namely: ranging from production of hot water for home needs to production of high potential energy of overheated steam.

SUBSTANCE: solar energy concentrator is made in such a way that absorber located in its focus does not create a shadow in working mirror zone and allows positioning of concentrator rotation axis in gravity center of whole system. Absorber is represented by parabolic cylindrical concentrator with low focus distance, and focuses of concentrator and absorber do not coincide, between them, receiver with heat carrier is positioned, and system for tracking sun by azimuth and its elevation, based on calculated and constant characteristics, corresponding to geographical location where concentrator is mounted and provide required speed of rotation around polar axis and change of height during the day with consideration of time of the year. Device is a reverse mechanical drive, rotating a screw pair, to nut of which a toothed bar is rigidly fastened, during movement of which toothed sector turns and, simultaneously, turning the bar with the follower, which monitors daily sun height change.

EFFECT: production of maximal quantity of light stream energy, increased precision and reliability of device.

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Description

The invention relates to solar energy and can find application in a wide range of uses depending on the working area of the concentrator, namely: from producing hot water for domestic needs to obtaining high potential energy of superheated steam.

In order to trace a system that will determine the initial data for installing a parabolocylindrical solar energy concentrator in the desired geographical location, and, moreover, ensure the efficiency of tracking the sun in azimuth and elevation, it is necessary to determine constant initial values that will form the basis of the calculation for actuators operating in the sun tracking system.

It is known that when the solar concentrator rotates around the polar axis, the annual insolation of one square meter exceeds two or more times the insolation of a square meter located horizontally. During the day, the earth rotates around its axis 360 degrees, however, the concentration of solar energy in the device will occur in the interval when the sun is in the sky. This period of time will vary depending on the latitude and location of the solar concentrator. For this purpose, it is necessary to follow two conditions for changing the height of the sun during the day and the conditions for changing the height of the sun over the seasons.

1. Conditions for changing the height of the sun during the daytime.

Using weather service data on the length of the day, the height of the sun in the morning, and the maximum height at noon and in the evening at a given time, you can determine the angle of rotation of the parabolic-cylindrical solar energy concentrator when the energy removal is maximum, provided that the light flux passes parallel to the focal plane of the parabola. For this purpose, the focal plane of the parabolic cylindrical concentrator should be constantly oriented strictly perpendicular to the ecliptic (the movement of the sun from west to east in a large circle of the celestial sphere).

2. The condition for changing the height of the sun depending on the time of year.

For each specific place on earth, there are coordinates. In this regard, in order to tie the installation of a parabolic cylindrical solar energy concentrator to the terrain, it is necessary to trace the dependence of the change in equatorial coordinates that affect the principle of installing a solar concentrator with a tracking mechanism.

Consider the location of the object at latitude - j (constant value). The Earth's axis deviates at an angle of 23 ° 27 'from the perpendicular to the ecliptic plane, so each of the geographical zones of the earth is tilted for the part of the year towards the sun, and the other part of the year to the opposite side.

The midday height of the sun on the vernal equinox at latitude j is h = 90 ° -j.

On the day of the summer solstice, the noonday height of the Sun at this northern latitude reaches the maximum value hmax = 90 ° -j + 23 ° 27 '.

When the sun is at the point of the autumnal equinox (September 23), then on the whole earth the sun rises at the point of the east and sets at the point of the west and again at all latitudes except the poles, the length of the day is equal to the length of the night. The height of the sun at noon at a given latitude j on the day of the autumnal equinox is again 90 ° -j.

When the sun is at the point of winter solstice (around December 22), it rises in the southeast, and sets in the southwest. Most of its daily route is below the horizon. At a given northern geographical latitude, the duration of the day is minimum, and nights are maximum. The height of the sun on the day of the winter solstice in this northern latitude reaches a minimum value hmin = 90 ° -j-23 ° 27 '.

On the remaining days of the year, the height of the sun at noon lies between the values of hmin hmax.

Thus, from hmax to hmin, these are the limits of the angle of inclination of the parabolic cylindrical solar energy concentrator, depending on the latitude of the concentrator and the time of year. These significant changes in the tilt angles of the concentrator are in the range from 80 to 40 degrees (for the city of Vladivostok it is 43 degrees) to the equatorial plane of the globe, therefore it cannot be ignored, otherwise, the length of the absorber will need to be increased by almost 20%, especially in high latitudes. This is the second of the constant conditions for constructing a sun tracking device. The sun is moving across the horizon from east to west, so the longitudinal focus line of the cylindrical concentrator should be oriented strictly from north to south perpendicular to the ecliptic with its apex to the north. Considering the height of the sun in the design solutions for the above reasons - the parabolic cylindrical concentrator of solar energy, it is necessary to turn around the polar axis from east to west at a speed equal to the speed of the sun in the sky.

Thus, the basis for the calculation are constant values.

1. The geographical latitude of the parabolic cylindrical solar energy concentrator - j.

2. Weather station data on the length of the day and the height of the sun in the daytime from sunrise to sunset.

3. Data on the seasons, depending on geographical latitude, this angle is in the range from hmin to hmax, which changes over 180 days and comes back also over 180 days, changing its position during the day within 0.18-0.23 degrees. Adjustment for such a shift can occur once a month manually by the operator, it is not advisable to automate this process, therefore, adjustment screws are provided in the device.

Various solar energy concentrators with absorbers and heat sinks are known from literature, in which constant orientation to the sun during tracking is provided by a photoelectric sensor and an electronic signal conversion unit, an electric motor with a gearbox for rotating the solar collector structure (RU 2105936, RU 2061933, US 47949090).

The main disadvantage of these devices is the inability to track the sun with its partial absence in the daytime.

The closest in technical essence and the achieved result to the solar energy concentrator is the Solar power plant according to patent RU No. 2190810 C2, 7 F24J 2/14, F24J 2/52 “Solar power plant”, which is a parabolic cylinder, in the focus of which a heat-receiving element is placed (solar boiler), through which the coolant circulates, contains a concentrator located in the direction from north to south, the drive of the rotation mechanism, providing maximum power concentrate ora irrespective of declination of the sun and program management. As a heat carrier, water or a non-freezing liquid is used.

The disadvantages of this tracking device are:

- even with short-term dimming of the sun, photoelectric sensors do not work, orientation is lost, the process of tracking the sun is disrupted;

- only in the zenithal position of the sun is the light flux perpendicular to the surface of the parabolic mirror, and in its extreme positions the light flux deviates by an angle of about 15 degrees, depending on the geographical position of the solar installation.

The aim of the invention is to obtain the maximum amount of energy of the light flux, increasing the accuracy and reliability of the parabolic cylinder concentrator of solar energy.

The goal is achieved in that the solar energy concentrator is designed in such a way that the absorber placed in its focus does not create a shadow in the working mirror zone and allows you to place the axis of rotation of the concentrator in the center of gravity of the entire system, while the absorber is a small parabolic cylindrical concentrator with a small focal length moreover, the foci of the concentrator and the small parabolic cylinder concentrator do not coincide; between them there is a receiver with a coolant, and the tracking system for the sun in azimuth and elevation angle, the base on the calculated constant characteristics that correspond to the geographical location of the concentrator and the change in the height of the sun during the day, taking into account the time of year, provides the necessary speed of rotation around the polar axis and is a reversible mechanical drive that rotates a screw pair, to the nut of which the gear rack is rigidly fixed, when moving which the gear sector is rotated, mounted on the axis of rotation of the concentrator, and simultaneously turning the bar along the copier, which controls the daily change in the height of the sun, and the change in the height of the sun over the time of the year is provided by a screw pair pivotally mounted in the support posts, the screw of which is connected to the corridor, to obtain the maximum amount of light flux energy , improving accuracy and reliability.

Figure 1 shows a parabolic cylindrical solar energy concentrator with a cavity absorber of solar energy and a sun tracking mechanism.

Figure 2 - system for tracking the sun.

Figure 3 - absorber with a heat sink.

The proposed parabolic cylindrical solar energy concentrator consists of a two-column support frame 1 and a rotary axis 2 on the bearing bearings 3, mounted on the ends of the support posts 4. The carrier frame 5 of the parabolic cylindrical solar energy concentrator is mounted on the rotary axis 2, passing through the center of gravity of the entire system in a balanced position, and can be rotated on bearing bearings 3. At the ends of the racks of the supporting frame 5 are fixed thrust bearing bearings 6 of the axis of rotation 7 of the parabolic cylinder concentrator 8 with an absorber installed above it 9. The axis of rotation 7 of the parabola is oriented in the south-north direction and is perpendicular to the rotary axis 2 of the swing of the carrier frame 5. At the end of the axis of rotation 7 is fixed the gear sector 10, which rotates the parabola when moving the gear rack 11, for example: eight hours at 120 degrees. The gear rack 11 is rigidly connected to the nut 12 and moves when the spindle 13 is rotated from the reversing drive 14, mounted on the carrier frame 5. The nut 12 is pivotally connected to the upper end of the rod 15, which passes through the swivel joint 16, mounted on the carrier frame 5. Lower the end of the rod 15 is in constant engagement of the guides of the copier 17, which is pivotally mounted on the supporting frame 18. The supporting frame 18 is rigidly connected through the lever 19 with the rotary axis 2 and its angular position together with the supporting frame 5 and the parabolic cylinder The rum 8 relative to the horizon is changed by a screw 20, the nut 21 of which is pivotally mounted between the support posts 4. The angle of inclination of the axis of rotation 7 of the parabolic-cylindrical hub 8 relative to the horizon varies periodically, for example once a month. In this case, the luminous flux should be perpendicular to the surface of the sun-tracking parabola for, for example, from 9 to 17 hours, which corresponds to 120 degrees of rotation of the parabola during the most light flux. Since only at the zenith the luminous flux is absolutely perpendicular to the axis of rotation of the parabola, at the beginning and at the end of the parabola, for example, at 9 and 17 hours, the luminous flux slightly deviates by an angle.

Correction of the angle of inclination of the axis of rotation 7 of the parabola is carried out by the rod 15. At the beginning and at the end of the parabola, the rod 15 takes an inclined position, and in the middle of the work, when the sun is at its zenith, it is in a vertical position. In this case, the lower end of the rod 15, abutting against the guide of the copier 17, raises or lowers the end of the carrier frame 5 relative to the rotary axis 2 to a height h corresponding to the angle of deviation of the light flux of 15 degrees.

The absorber 9 (see Fig. 3) consists of a small parabolic-cylindrical concentrator with a small focal length 22, a heat sink 23 made of heat-resistant glass 24, while the absorber 9 is set so that its heat sink 23 is located between the foci of the small and main concentrators. The reflected rays 25, 26 and 27 of the light flux are distributed across the width of the absorber 9.

The proposed device operates as follows.

The preliminary two-line supporting frame 1 of the parabolic cylindrical solar energy concentrator is set so that the rotation axis 7 of the rotation of the parabolic cylindrical concentrator 8 is oriented strictly in the north-south direction, and the rotary axis 2 of the carrier frame 5 of the parabolic cylindrical concentrator should be horizontal. Manual rotation of the screw 13 together with the rack 11 and the gear sector 10 is set in the middle position, in which the focal plane of the parabolic-cylindrical concentrator 8 should be vertical and coincide with the axis of the rod 15. In the zenith position of the sun with screws 20 through the lever 19 by turning on the carrier rotary axis 2 of the frame 5, the angle of inclination of the axis of rotation of the parabola 7 relative to the horizon is set so that the light flux from the sun is strictly perpendicular to the surface of the parabola, while the angle between the supporting frames oh 5 and fixed lever 19 will be maximum and equal to 15 degrees. Then, manually rotating the spindle 13 of the para-cylinder concentrator 8 is set to the initial position corresponding to the beginning of the working session, the signal of which gives the time relay, for example, nine hours. The time relay at the beginning of the session includes a reversible drive 14, which automatically rotates the parabolic cylindrical hub 8, ensuring the accuracy of tracking the sun. At the end of the session, the reversing drive 14 switches with the end switch to quickly return the parabolic-cylindrical concentrator 8 to its original position, in which the other end switch turns off the reversing drive 14 and turns on the timer in standby mode for the start of the session. Thus, the automatic tracking of the sun, which does not depend on the intensity of the light flux.

During the session, the angle of inclination of the axis of rotation of the parabola 7 is automatically changed within +15 degrees due to rotation around the rotary hinge 16 of the rod 15, the upper end of which is pivotally connected to a nut 12, which, when the rotor 13 rotates, moves along it with a rail 11 rotation of the gear sector 10 on the axis of the parabola. This ensures a constant directivity of the light flux of the sun perpendicular to the surface of the mirror of the parabolic concentrator 8, from which the most concentrated rays 25 directly fall on the heat sink 23 of the absorber 9, and the remaining rays 26 fall on the heat sink 23 after reflection from the mirror of a small parabolic concentrator 22, some of which are reflected rays 27 will give part of their thermal energy to the mirror of the absorber 9, without falling onto the surface of the heat receiver 23.

Claims (1)

A parabolic cylindrical solar energy concentrator with an absorber and a tracking system for the sun, containing a concentrator located in the north-south direction, a drive of a rotation mechanism providing maximum power to the concentrator regardless of the declination of the sun, characterized in that the solar energy concentrator is designed in such a way that its focus, the absorber does not create a shadow in the working mirror zone and allows you to place the axis of rotation of the concentrator in the center of gravity of the entire system, while the absorber dstavlyaet a small parabolic trough concentrator with a small focal distance, the concentrator and small foci parabolic trough concentrator do not match; between them there is a receiver with a coolant, and the tracking system for the sun in azimuth and elevation angle, based on calculated constant characteristics that correspond to the geographical location of the concentrator and the change in the height of the sun during the day, taking into account the time of year, provides the necessary speed of rotation around the polar axis and is a reversible mechanical drive that rotates a screw pair, to the nut of which a gear rack is rigidly fixed, when moving which the gear sector is rotated, mounted on the axis of rotation of the concentrator and at the same time turning the bar on the copier, which controls the daily change in the height of the sun, and the change in the height of the sun during the seasons is provided by a screw pair pivotally mounted in the support posts, the screw of which is connected to the copier, to obtain the maximum amount of light flux energy, increase accuracy and reliability.

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