WO2014003680A1

WO2014003680A1 - Method and device for heating using sunlight

Info

Publication number: WO2014003680A1
Application number: PCT/SE2013/050820
Authority: WO
Inventors: Rolf Ljunggren; Thomas Davidsson
Original assignee: H2Do Ab
Priority date: 2012-06-29
Filing date: 2013-06-28
Publication date: 2014-01-03
Also published as: EP2867594A4; EP2867594A1; SE1250743A1

Abstract

Device (10) for heating using sunlight, whereby at least two sunlight focusing devices (11,12,13) are arranged to focus sunlight and to convey the focused sunlight into and along a respective one of at least to optical fiber devices (14, 15, 16). The invention is characterised in that the at least two optical fiber devices are arranged to convey the light to a certain common area ( 20; 120; 220 ) so that the light from the at least two optical fiber devices incides towards the common area.

Description

Method and device for heating using sunlight

The present invention relates to a method and a device for heating using sunlight.

In many industrial processes, energy is required in the form of heat, cool or electricity. A problem in such contexts is to achieve such energy supply without adversely affecting the environment, such as by carbon dioxide outputs to the atmos- phere or pollution.

It is known to use solar energy to supply for instance heat to an industrial process, but it is difficult to achieve sufficiently high temperatures in sufficient quantities in order to drive more large-scale industrial processes only using solar energy.

Furthermore, it has proven difficult to achieve a sufficient supply of solar energy to industrial processes with low loss- es and high efficiency.

Moreover, there is a need for a way to supply solar energy to such processes in a way allowing rapid and simple ramping up and down of the energy supply.

The present invention solves the above described problems.

Hence, the invention relates to a device for heating using sunlight, whereby at least two sunlight focusing devices are arranged to focus sunlight and to convey the focused sunlight into and along a respective one of at least to optical fiber devices, and is characterised in that the at least two optical fiber devices are arranged to convey the light to a cer- tain common area so that the light from the at least two optical fiber devices incides towards the common area.

The invention will now be described in detail, with reference to exemplifying embodiments of the invention and to the appended drawings, wherein:

Figure 1 is a simplified outline sketch of a device according to the present invention comprising several sunlight focusing devices ;

Figure 2 is a simplified outline sketch of a sunlight focusing device according to the invention;

Figurers 3a, 3b and 4 are simplified outline sketches of different embodiments according to the invention for exploiting focused sunlight.

Figure 1 illustrates a device 10 according to the present invention for focusing large amounts of sunlight towards a common area 20, arranged as a part of an object 21 to be heated and possibly to be disinfected.

The expression "common area" shall, in this context, be interpreted so that light from more than one fiber device (see below) is directed so that it incides towards a common area on or inside an object, in the form of a common focus point, across a common, limited surface, through a limited common volume of a translucent material or the corresponding. The common area does preferably not have a larger magnitude of size than an area which is lit by the light from one single fiber device, and it is preferred that the area onto which the light from each fiber device is focused overlaps with the light from at least one other fiber device. It is realized that the "area" can be in the form of a one-dimensional point, a two-dimensional surface or a three-dimensional vol^¬ ume .

A plurality, in other words more than two, preferably at least three, rather at least ten, rather at least one hundred, sunlight collecting devices 11, 12, 13, which for instance may comprise parabolic mirrors, are arranged to focus sunlight incident towards the respective device 11, 12, 13 into a respective optical fiber 14, 15, 16, or a respective optical fiber cable which itself comprises several parallel optical fibers. At least two, preferably at least ten, rather at least one hundred of the devices 11, 12, 13 are arranged to convey light into one respective own optical fiber 14, 15, 16 or a respective own optical fiber cable according to the above, which is not shared with any other of the sunlight collecting devices. It is noted that a single sunlight collecting device may be arranged to focus light into a bunch of optical fibers that all constitute a part of an optical fiber cable. What is important is that each one of the sunlight collecting devices 11, 12, 13 as such only focuses incident sunlight into one respective such fiber cable each.

Hence, the fibers 14, 15, 16 convey the thus collected sunlight further to the object 21, and direct the light 17, 18, 19 towards the common area 20, which then becomes warm. It is preferred that the material in the optical fiber is selected so that sufficient amounts of UV light is conveyed through it in order for the area 20 to also be disinfected. It is preferred that the fibers 14, 15, 16 each are at least 10 meters of length.

By using several sunlight focusing devices 11, 12, 13, that via individual fibers 14, 15, 16 or fiber cables convey the focused light to a common area 20, a number of advantages are achieved as compared to the conventional art. Firstly, great flexibility is achieved regarding the positioning of the sunlight focusing devices 11, 12, 13, which can be positioned relatively freely in relation to both each other and to the common area 20. For instance, this can be advantageous in locations where the ground area is limited, whereby solar collectors can be installed on roofs while the rest of the equipment can be placed in spaces with easier access. Moreover, the devices 11, 12, 13 can be positioned at different places, so that for instance certain devices are placed on a roof and others on the ground next the house. It is also possible to spread out the devices 11, 12, 13 so that at least some of the devices 11, 12, 13 are not shadowed at each point in time across a whole day.

Secondly, it is made possible for several solar collectors to be used for exploiting the collected solar energy, for instance for heating of water in one and the same boiling device (see below) . Since the light power which can be conveyed through one and the same fiber is limited, and since one and the same sunlight focusing device 11, 12, 13, having only a limited surface, can only focus a limited amount of sunlight, this way a considerably increased liberty is achieved regarding the performance of the device in terms of the maximum amount of produced distilled water, which may be increased at only linear cost increase by extending the plant with additional sunlight focusing devices. The use of only one common area 20 also often gives rise to economies of scale, which for instance is the case if the solar energy is to be used for boiling water in a boiling device in which the common area 20 is arranged. Figure 2 illustrates a device according the present invention for focusing incident sunlight into an optical fiber 53 or an optical fiber cable which itself comprises several parallel optical fibers.

The device comprises a primary sunlight focusing device 50, such as a parabolic mirror which is conventional as such, as well as a secondary sunlight focusing device 51, such as an additional mirror. Incident sunlight L is first reflected by the primary focusing device 50 and is then directed towards, and is reflected further by the secondary focusing device, whereby the light is directed towards a lens 52, which in turn is arranged to focus the light towards and into an end 53a of the fiber 53.

A challenge in concentrating sunlight from one or several sources into one or several optical fibers is that high power then needs to be transported from one medium into another. Foremost at the borders there is a risk for large energy losses .

In order to solve this problem, the side of the lens 52 through which the light exits the lens 52 and the end surface of the fiber end 53a constitute two respective limiting walls of a chamber 54 in the interior 55 of which there is a limited pressure, preferably vacuum. In other words, the light travelling between the lens 52 and the fiber end 53a will not pass through any other medium apart from the vacuum in the interior 55 of the chamber 54. This results in that the focused light cannot heat any other medium, such as air, except the fiber end 53a itself. Since the fiber end 53a can lead surplus heat away along the fiber 53a, this way a very intensive incident sunlight radiation can be focused down into and along the fiber 53 without risking overheating at the very transition into the fiber end 53a. Alternatively, a more low performing material regarding the fiber 53 itself and connections, etc., at the said transition can be selected at the same incident light radiation intensity.

Moreover, such an arrangement results in that higher efficiency is reached through decreased thermal losses. An additional advantage is that the useful life of the fiber end 53a, the lens 52 and other parts of the connection between the lens 52 and the fiber end 53a is prolonged, since the more intensive heat in combination with air contact would result in faster material ageing by for instance oxidation.

The vacuum is preferably a gas pressure inside the interior 55 of the chamber 54 of 0.05 bars or less, preferably 0.01 bars or less.

As is shown in figure 2, it is preferred that the fiber end 53a projects a certain distance into the chamber 53, so that a part of the envelope surface of the fiber 53 constitutes a limiting wall of the chamber 53. This results in that the location where the sunlight is focused can be kept at a safe distance from all thermally conductive media. It is preferred that the lens 52 has a maximum diameter of at the most 10 cm, preferably at the most 5 cm. Moreover, it is preferred that the fiber end 53a projects into the chamber 54 at least 5 mm, preferably at least 10 mm, so that it runs freely this distance inside the interior 55 of the chamber 54 with no contact with surrounding material, such as housings, air or jointings.

The sunlight which is focused using the above described device can be exploited in several different ways. A first example, which is illustrated in figure 3a, is for achieving a gas for use in different industrial processes. Sunlight is conveyed via fibers 114, 115, 116 in a way simi- lar to the one described above, and rays of light 117, 118, 119 are directed towards a common focus area 120 on a black body 121 arranged in a boiling container 122 for a fluid, with a fluid surface 123. The focus area 120 may be arranged on, at or inside the container 122, so long as the black body 121 is heated using the incident sunlight radiation. As a consequence thereof, the liquid surrounding the black body 121, and especially that which surrounds the focus area 120, is also heated. The liquid is heated to its boiling point, and the gas phase of the liquid formed by the boiling is transported through a conduit 124, via a valve 125, to a process step 132 in which the gas is to be used. The used gas, or condensed gas in liquid phase, is preferably transported back from the process step 132, via a conduit 126 and a valve 127, back to the boiling container 122 so that a closed loop is achieved.

The liquid may be any suitable liquid the gas phase of which is useful in an industrial process. However, it is preferred that the liquid is water and that the gas phase is steam.

By suitable design of the boiling container 122 and the valve 125, and by selections of the liquid, the produced gas phase can selectively be pressurized and/or hot, something which may be exploited in various industrial processes.

Preferred such industrial processes in which the produced gas can be used comprise use in steam turbines and steam engines in order to perform mechanical work, in particular mechanical work for producing electricity. According to a preferred embodiment, the pressurized gas is transported to a turbine driven by the gas pressure, which in turn drives a generator producing electricity. This way, electricity can be produced only using solar energy and based upon the existence of only a small amount of water.

Other industrial processes in which the produced gas can be used, especially if the gas is steam, comprise for instance steam treatment processes within the food industry, as well as manufacturing of different products and substances.

A preferred process step 132 is an adsorption cooling step, in which the hot gas phase is used as a heating source in a per se conventional circuit for adsorption cooling of another medium. The achieved cool can for instance be used for cooling indoors air and for various other industrial cooling processes. The adsorption material can for instance be water or other fluid material, as well as silica gel or zeolite which may be combined with water.

This way of generating cool is energy efficient and also very flexible. It makes it possible to produce cool even in locations where the access to electrical energy is limited, as long as a small amount of water and sunlight are accessible.

Figure 3b, sharing reference numerals with figure 3a for corresponding parts, illustrates an alternative use for the produced gas, in order to obtain distilled liquid, preferably distilled water, for instance potable water. In this case, steam that has been evaporated in the boiling container 122 is transported, via the conduit 124 and the valve 125, to a container 131 for distilled water. The steam is either condensed in a separate condenser (not shown) , or by heat exchange using a heat exchanger 130, which preferably is of counterflow type and is arranged to transfer thermal energy from the steam in the conduit 124 to supply water to be cleaned. The supply water is supplied through a conduit 128 and a valve 129, and is in thermal contact, via the heat exchanger 130, with the steam in the conduit 124. This way, potable water can be achieved in a very energy efficient way, based upon filthy or infected water, since the water to be cleaned is preheated before it enters the boiling container 122.

Such a device can be driven without externally provided energy, except solar energy, in case for instance the water to be cleaned is supplied via the conduit 128 using a pump driven using electricity produced by a turbine and a generator as described above.

The production of a gas phase in this way is very energy efficient, since essentially all collected solar energy is used to heat and to boil the liquid to gas phase. The system can in many cases be made self-circulatory, so that it is driven by the gas pressure itself. When this is not possible, it can be driven using solar driven pumps or the like according to the above. Furthermore, high power can be guaranteed by arranging a sufficient number of solar collecting devices 11, 12, 13. This results for instance in that the temperature of the exiting gas can be high, such as substantially higher than the condensing temperature, which can increase the efficiency of the process step 132. Moreover, there is a great flexibility when it comes to the design and location of the boiling device 122 itself, since the light being conveyed up to the boiling device 122 through the fibers 114, 115, 116 can be collected at a distance from the boiling device 122 and also be conveyed up to a clearly defined area also deep inside the boiling device 122. According to another preferred embodiment, which is illustrated in figure 4, light 217, 218, 219 which has been focused according to the above, is conveyed through respective fibers 214, 215, 216, and is focused towards an area 220 on a material 221 arranged in a container 222. The material 221 is preferably a moist fraction, such as biomass sludge; other moist industrial products, such as for instance minerals in concentration processes; or foodstuffs or fodder, and the solar energy is used to dry the material 221 by heating.

This arrangement brings with it also the advantage that the material 221 can be disinfected using the UV radiation contained in the sunlight. This is especially useful for steri- lizing for instance sludge from a sewage water treatment plant or foodstuffs .

Dried off moist from the material 221, in the form of hot steam, is thereafter brought, via a conduit 223 and a valve 224, to another container 225, which comprises an additional container 226 onto which the hot steam condenses and thereby transfers thermal energy to the container 226. Thereafter, the remaining gas phase and condensate are transported, via a conduit 227 and a valve 228, for further treatment. The con- tainer 226 contains an additional moist fraction, which may be the same as or similar to the material 221, but which may be dried at lower temperatures. The second moist fraction is dried using the thermal energy from the condensed liquid in the container 225. Evaporated gas from the fraction in the container 226 is led off, via a conduit 229 and a valve 230, for further treatment.

With such a condensing drying step, which is connected in series with a primary drying step, the fact can be exploited that the solar energy incident towards the material 221 is capable to heat the material 221 to much higher temperatures. Drying is conventionally a very energy demanding industrial process, which according to the present invention can be performed completely or essentially with no externally supplied energy, except the solar energy, and at high efficiency.

The heating of the material 221 can also take place indirectly, by focusing the incident solar radiation towards an area on a receiver which is in thermal contact, either through heat conduction, heat radiation or convection, with the material 221. Indirect heating can also take place using boiled off gas from a boiling device 122 according to the above said in connection to figure 3a.

Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications may be made to the described embodiments without departing from the basic idea of the invention.

Hence, the invention shall not be limited to the described embodiments, but may be varied within the scope of the enclosed claims.

Claims

C L A I M S

1. Device (10) for heating using sunlight, whereby at least two sunlight focusing devices (11,12,13) are arranged to focus sunlight and to convey the focused sunlight into and along a respective one of at least two optical fiber devices (14,15,16), c h a r a c t e r i s e d i n that the at least two optical fiber devices are arranged to convey the light to a certain common area ( 20 ; 120 ; 220 ) so that the light from the at least two optical fiber devices incides towards the common area .

2. Device (10) according to claim 1, c h a r a c t e r i s e d i n that the device comprises a light focusing lens (52), a side of which constitutes a limiting wall to a chamber (54) in which there is a reduced pressure, and in that a free fiber end (53a) of one of the optical fiber devices (53) constitutes an additional limiting wall to the chamber, so that light incident from the lens to the fiber end only pass- es through the interior (55) of the chamber and not through any other medium.

3. Device (10) according to claim 2, c h a r a c t e r i s e d i n that the free fiber end (53a) protrudes a cer- tain distance into the chamber (54), so that a part of the envelope surface of the optical fiber device (53) also constitutes a limiting wall to the chamber.

4. Device (10) according to any one of the preceding claims, c h a r a c t e r i s e d i n that the device comprises a container (122) for a fluid, where the common area (120) is arranged on, at or in the container, so that the liquid is heated to the boiling point by the light when the light incides towards the common area.

5. Device (10) according to claim 4, c h a r a c t e r i s e d i n that the liquid is water, in that a conduit device (124) is arranged to transport steam that has been boiled off from the liquid, via a heat exchanger (130), to a collecting container (131) for condensed water, in that another conduit device (128) is arranged to transport water to be boiled, via the heat exchanger, to the container, and in that the heat exchanger is arranged to transfer thermal ener- gy from the boiled off steam to the water to be boiled.

6. Device (10) according to claim 4, c h a r a c t e r i s e d i n that a conduit device (124) is arranged to transport hot gas that has been boiled off from the liquid to a process device (132) for performing an industrial process, in that the process device comprises an adsorption cooling step in which the gas is used as a heat source, a drying step in which the gas is used as a heat source or an electricity production step in which the gas is used as a pressure source in a turbine in the electricity productions step.

7. Device (10) according to any one of claims 1-3, c h a r a c t e r i s e d i n that the device comprises a space (222) for a moist material (221) to be dried, and in that the common area (220) is arranged so that the moist material is heated using the incident sunlight.

8. Device (10) according to claim 7, c h a r a c t e r i s e d i n that a conduit device (223) is arranged to transport hot steam, which has evaporated from the moisture content in the moist material (222), to a secondary drying step (225) in which the heat content in the hot steam is used to dry a second moist material.

9. Method for heating using sunlight, whereby sunlight is focused, using at least two sunlight focusing devices (11,12,13), and is conveyed into and along a respective one of at least two optical fiber devices (14,15,16), c h a r - a c t e r i s e d i n that the at least two optical fiber devices convey the light to a certain common area (20; 120; 220) so that the light from the at least two optical fiber devices incides towards the common area.

10. Method according to claim 9, c h a r a c t e r i s e d i n that the light on its way into one of the optical fiber devices (14,15,16) is conveyed through a lens (20), in that the light which travels between the lens and a free fiber end (53a) of the fiber device in question only passes the interior (55) of a chamber (54), where one side of the lens constitutes a limiting wall to the chamber and where the free fiber end constitutes an additional limiting wall to the chamber, and in that a limited pressure is caused to prevail inside the chamber.

11. Method according to claim 10, c h a r a c t e r i s e d i n that the free fiber end (53a) is caused to protrude a certain distance into the chamber (54), so that a part of an envelope surface of the optical fiber device (14,15,16) also constitutes a limiting wall for the chamber.

12. Method according to any one of claims 9-11, c h a r a c t e r i s e d i n that a liquid in a container (122) is heated to the boiling point using light incident towards the common area (120) , which is arranged on, at or in the container .

13. Method according to claim 12, c h a r a c t e r i s e d i n that the liquid is water, in that a conduit device (124) transports steam that has been boiled off from the liquid, via a heat exchanger (130), to a collecting container (131) for condensed water, in that another conduit device (128) transports water to be boiled, via the heat exchanger, to the container (122), and in that the heat exchanger transfers thermal energy from the boiled off steam to the water to be boiled .

14. Method according to claim 12, c h a r a c t e r i s e d i n that a conduit device (124) transports hot gas that has been boiled off from the liquid to a process device (132) for performing an industrial process, in that the process device is caused to comprise an adsorption cooling step in which the gas is used as a heat source, a drying step in which the gas is used as a heat source or an electricity production step in which the gas is used as a pressure source in a turbine in the electricity productions step.

15. Method according to any one of claims 9-11, c h a r a c t e r i s e d i n that the device (10) is caused to comprise a space (222) for a moist material (221) to be dried, and in that the common area (220) is caused to be arranged so that the moist material is heated using the incident sunlight.

16. Method according to claim 15, c h a r a c t e r i s e d i n that a conduit device (223) transports hot steam, that has evaporated from the moisture content of the moist material (221), to a secondary drying step (225) in which the heat content in the hot steam is used to dry a second moist material .