ES2321271A1 - Solar power concentrator (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Solar energy concentrator with double reflection comprising at least: - a primary parabolic mirror (1) that sends to its own focal point f1, all the rays coming from the sun to its surface, - a hyperbolic secondary mirror (2) facing the primary parabolic mirror, which intercepts the sun's rays reflected by the primary mirror and redirects them to the effective focus f located between the primary mirror (1) and the secondary mirror (2). - a receiver or collector of heat or solar energy (3) for its transformation into electrical energy located in the center of the structure of the parabolic primary mirror, so that it moves in solidarity with it. (Machine-translation by Google Translate, not legally binding)

Description

Solar power concentrator

Object of the invention

The invention is framed in the field of Solar Energy uptake, and the object of the invention is concentrate it at a collection point, by means of a double reflection, to improve the performance of the facilities and lower costs.

Background

Renewable energies are many and varied and the techniques developed for its use progress every day.

Currently solar concentrators allow you to concentrate the sun's rays at a point for your use and transformation into electrical energy or thermal

Known solar concentrators and more used to date consist of parabolic mirrors aligned, which allow solar radiation to be concentrated at one point (focus) of each mirror, such that a duct, with liquid in inside, passes through all the foci of each of the mirrors, for obtaining thermal energy, increasing considerably the temperature in the duct, thus obtaining thermal energy that can be used for its transformation into electric power.

There is also what is known as "Disco Parabolic "or" Solar Plate ", consisting of a single mirror parabolic, concentrating the sun's rays at a certain point or sensor, which is usually in front of the parabolic mirror, subject through a structure, and that is usually a type engine Stirling. The problems offered by this system are, one the economic, given the difficulty of building a structure to stabilize the Stirling engine so far from the parabola mirror, taking into account that the whole system is at weathering, and another problem with this system is the defocusing of the sun's rays, at the point of reception, is that is, the point where the Stirling engine is located, as any  adverse weather condition, such as wind, can move the slightly sensor and improper placement will mean significant performance losses.

On the other hand, solar concentrators with flat mirrors are not able to optimize and take advantage of all the solar radiation possible, concentrating on a single point, as they make the parabolic mirrors.

Description of the invention

The present invention offers a solution novel to the aforementioned problems, for maximum use of solar radiation and its transformation into energy electric

The concentrator of the invention comprises two curved mirrors, one parabolic and one hyperbolic, facing each other and oriented towards the sun's rays to obtain a double reflection, placing the fixed solar energy collector and in solidarity with the center of the curved mirror structure, which contributes simplicity of construction, reliability of concentration and structural stability

The first mirror has a solar plate with a parabolic curvature and solar rays reach it perpendicularly and concentrates them in the second mirror, located in front and whose solar plate has a hyperbolic curvature, which at its instead it concentrates the rays in the center of the initial parable, where a collector is installed, which transforms solar energy into energy electric The solar energy collector, preferably an engine Stirling, is located in the center of the structure of the primary mirror with parabolic shape, and moves in solidarity with the movement of said mirror.

The advantages of the present invention are:

- better focus of the sun's rays, due to that the set moves as a stable structure so solidarity and that the concentration of radiation is brought to the center of the primary mirror (the parabola) on a point (the sensor), and  produces in two stages,

- regulate the approach or distance of focus effective (f), thanks to the Stirling engine position, and so on achieve a greater or lesser concentration of heat in the receiver, according to the needs.

- better evacuation of the energy obtained, from the sensor, thanks to the good positioning of the sensor in the center of the parable,

- by simplifying the structure, the cost will be reduces considerably, resulting in a much more structure Stable and reliable, at a lower price.

Brief description of the drawings

Then it goes on to describe very brief a series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention presented as a non-limiting example of is.

Figure 1 shows a mirror scheme parabolic primary and the defining characteristics

Figure 2 shows a mirror scheme hyperbolic secondary and the defining characteristics

Figure 3 shows the two primary mirrors and secondary and the focal length of the primary mirror f_ {1}

Figure 4 shows a scheme where represent the two primary and secondary mirrors and the distance resulting focal

In this figure the references represented belong to:

1.- Parabolic primary mirror

2.- Hyperbolic secondary mirror

3.- Receiver or heat collector

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Description of a preferred embodiment of the invention

The concentrator of the invention comprises two mirrors one parabolic primary (1) and another hyperbolic secondary (2) and a receiver or collector of heat or solar energy (3) for its transformation into electrical energy, such as a motor Stirling which is a known engine whose main feature is which only needs a heat source external to the cylinder of said engine, for power generation.

The two mirrors are located, as shown in Figure 4, in such a way that the parabolic primary mirror (1) sends all the rays that arrive from the Sun to its surface, to its own focal point f_ {1} located behind of the secondary mirror (2), these being intercepted by the secondary mirror (2), which is in its path, and redirected to the effective focus f located one meter before the primary mirror (1), between it and the secondary one (2) .

The concentrator design procedure of solar energy of the invention, comprises the steps of

-

calculation of the equations of the two primary (1) and secondary (2) mirrors and their respective position, to from the equations of the parable and the hyperbole, considering that the effective focus f is one meter before primary mirror (1), between this and the secondary mirror (2),

-

placement of the sensor (3) or absorber with Stirling engine (or some other receiver or heat collector that transforms solar energy into electrical energy) in the center of the structure of the parabolic primary mirror, fixedly and in solidarity with him, this is a function of its opening diameter, of the area of the absorber plane and of the radiation that it can hold or distribution of the flow that is required and in turn this It will be a function of the quality of the mirrors.

The placement of the focus f to a meter of the primary mirror and between the two given the hypothesis of Stirling engine use, as the best position for when placing the engine, depending on the concentration of radiation required, this can be placed later or back around the plane and thus not vary much the moment torque generated by engine weight.

The technical development or calculation of the optics of mirror system that explains the operation of the system of the invention, is developed below, including an example with Possible dimensions.

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A) Calculation of the equations of the two primary mirrors parabolic (1) and hyperbolic secondary (2) and its position respective

The average distance from our planet to the Sun It is approximately 149 million km, so we can consider the "Astro Rey" as a light source what far enough so that the light comes collimated to our instruments, that is, with the rays parallel to each other. This point is important when choosing the way you should have a reflective surface with which it is intended to focus the light or, what is the same, make it converge on a point or a  region. The only conical surface capable of focusing collimated light it is a paraboloid and it does it on its optical focus which is a point of the optical axis on which the collimated light parallel to it is focused. So our primary mirror (1) must be a paraboloid

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The equation of a paraboloid is:

1 \ rho2 = 2RA_ {1}

Where "\ rho" is the distance from all points of the surface to the optical axis, since we can consider this as a succession of rings whose distance to that axis varies (\ rho2 = x2} + y2), and " A1 " is the distance from the center, from each circumference to the central vertex of the mirror, it is a coordinate, if we rotate the paraboloid and place its vertical axis it would be the height ( z axis ) (see fig . one).

The vertex of the mirror is defined as the point where it would cut the axis of revolution of the mirror, which in the present case at all times coincides with the optical axis, to the surface of the mirror.

Another important point is where it will be placed the focus of the primary mirror, that is, its focal length. By security reasons should focus on the mirror secondary, because having all the light concentrated at one point in the air at a very short distance from the second mirror can overheat it and because if at any time some technician commits the madness of placing some object or part of your body in this point while the mirror is focused the consequences may Be very negative. If we place the focus behind the mirror secondary we will only have the light concentrated in one point, in the final focus resulting from the optical system.

Taking the mirror configuration in the concentrator indicated in figure 4, the rays do not reach the mirror secondary (2) collimated, but focused by the mirror (1), is This is why the surface must be a hyperbole. Since the focus of the mirror (1) is located behind (2) and this is now the new object that you want to focus on. The equation of the hyperbole is:

one

Where again "\ rho" is the distance from all points of the surface to the optical axis, " A_ {2} " is the distance from the center of each circumference to the central vertex of the secondary mirror (2) and " a " and " b "are the following relationships:

2

Being " s " the distance from the object to the vertex of the mirror, in this case the focus of the primary mirror (1), and "s'" the distance from the vertex of the mirror to the image, in this case the focus resulting from the combination of The two mirrors.

As we see in Figure 3, for the calculation of the focal length f_ {1} of the primary mirror (1), since the tg \ alpha is

3

and taking into account that in this particular case the diameter of the primary mirror D 1 is 8 m, the diameter of the secondary mirror D 2 is 1.2 m and the distance between mirrors d is 4 m, it is possible to deduce that f_ {1} = 4,706 m, that is, behind the secondary mirror (2).

For the calculation of the radius of curvature of the primary mirror (1) R_ {1}, according to the equation of the mirrors:

4

since the sun is far away we can consider that in the \ infty

s = \ infty \ leftrightarrow s f = F

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in such a way that it follows that

R_ {1} = 2f_ {1}

R_ {1} = 9.412 \ m

Therefore, the equation that defines the shape of the primary parabolic mirror (1) is:

\ rho_ {1} {} 2 [m2] = 18,824 [m] \ cdot A_ {1} [m]

Where the square brackets [] indicate the units in that each part of the equation is expressed.

Another way to write this equation is:

z = 0.053 (x2 + and 2)

Units: m

Since \ rho {2} = x ^ {2} + y {2} and the distance from the center of each circle to the center vertex of the mirror is the z coordinate axes if placed in the conventional manner.

For the calculation of the mirror distance secondary (2) to focus f, it is necessary to be clear before where They want to focus the rays after crossing the system. For do not concentrate the rays just above the absorber plane of the Stirling engine since this could cause the material from which they are made is founded, the focus is placed before the Stirling engine, so you just have to delay the engine position to receive less concentrated radiation.

Placing the resulting focal 1 m from the mirror Primary, as shown in Figure 2, we have:

s = 0.706 [m]

s' = 3 [m]

The equation of the hyperboloid mirror resulting (2)

5

Where we can again call z to A_ {2} .

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B) Calculation of the reflection a) On the parabolic primary mirror (1)

The equation that gives the angle of reflection of the rays from the Sun, if the system points its optical axis at This is a function of the point on the surface of the next mirror defined by the distance (\ rho) from this to the optical axis and by the primary mirror equation (1)

6

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a) On the hyperbolic secondary mirror (2)

To find the angle of reflection (?) At each point on the surface, you must first calculate two angles
(\ phi, γ) and make use of the hyperboloid equation:

7

The parameters that describe a point about this the curve of the secondary mirror (2) is \ rho_ {2} and z_ {2}, with one of the two is enough for us since they relate to the equation of hyperboloid If we also want to know what relationship the points on the secondary mirror (2) with those of the primary mirror (1) or with the angle of reflection on the primary mirror, just Know that the equation that relates both is:

\ phi = 2α

Claims (3)

1. Solar energy concentrator characterized by comprising at least:

-

a parabolic primary mirror (1) that sends to its own focal point f_ {1} all the rays that come from the Sun to its surface,

-

a secondary hyperbolic mirror (2) faced with the primary mirror parabolic (1), which intercepts the sun's rays reflected by the primary mirror and redirects them to the effective focus f located between the primary mirror (1) and the secondary mirror (2).

-

a receiver or collector of heat or solar energy (3) for transformation into electrical energy, located in the center of the parabolic primary mirror structure, so that it moves in solidarity with him.

2. Solar concentrator according to claim 1 characterized in that the collector is a Stirling motor (3). 3. Solar concentrator according to claim 1 characterized in that the primary (1) and secondary (2) mirrors are positioned such that the focus f is placed one meter before the primary mirror.