FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: DEVICE FOR GENERATING STEAM
2. Applicant(s)
NAME NATIONALITY ADDRESS
TATA CONSULTANCY Indian Nirmal Building, 9th Floor, Nariman Point,
SERVICES LIMITED Mumbai 400021, Maharashtara, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The subject matter as described herein relates to devices for generating steam.
BACKGROUND
[0002] With high rate of technological advancement and growth of human population, the pressure on non-renewable natural resources is ever-increasing. As the non-renewable natural resources are being depleted at a tremendous rate, development of alternative sources of energy is imperative. One such alternative source of energy is solar energy. The greatest advantage of solar energy is that it is non-exhaustible in nature.
[0003] Various systems and devices have been devised in order to harness and utilize solar energy for different purposes, such as cooking and power generation. For example, solar heaters and solar cookers are commonly used, as are photo-voltaic cells and other photosensitive devices. The photo-voltaic cells are capable of using radiations that lie in the visible range of spectrum of solar radiations, and converting them into electric power. On the other hand, devices, such as solar heaters and solar cookers, generally use energy from the solar radiations for domestic heating and cooking applications and other general heating applications.
[0004] Apart from using solar energy for small scale applications, large scale solar-thermal power generation systems have been conventionally developed for converting solar energy into a useable form of energy. Such systems usually use energy of the solar radiations for heating water and generating steam. The steam is then utilized to operate a turbine, and hence, to generate useable power.
SUMMARY
[0005] The subject matter described herein relates to a device for generating steam when positioned on a water body. According to an embodiment, the device includes a base comprising a floor. The floor comprises a plurality of pores for entry of water into the base from the water body. A floatation body is attached to the base to provide buoyancy to the device. The device further includes a transparent cover disposed on the base. The transparent cover directs solar radiations onto the water in the base to generate steam.

[0006] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
BRIEF DESCRIPTION OF DRAWINGS
[0007] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.
[0008] Fig. 1 illustrates a device for generating steam, according to an embodiment of the present subject matter.
[0009] Fig. 2 illustrates a base of the device, according to an embodiment of the present subject matter.
[0010] Fig. 3 illustrates a thermal power system implementing the device, according to an implementation of the present subject matter.
[0011] Fig. 4 illustrates a super heater unit implemented in the thermal power system, according to an embodiment of the present subject matter.
[0012] Fig. 5 illustrates a controlling device implemented in the thermal power system, according to an embodiment of the present subject matter.
DETAILED DESCRIPTION
[0013] The present subject matter relates to a device for generating steam. The device as described herein can be used in different applications, for example, in a thermal power system for power generation, for sewage treatment, or for salt extraction.
[0014] Solar energy is seen as one of the most important alternate sources of energy because of its non-exhaustible nature. Conventionally, various systems and devices have been devised in order to harness and utilize solar energy for different purposes, such as for cooking and for power generation. For example, solar heaters and solar cookers are commonly used

for cooking and general heating, and photo-voltaic cells and other photo-sensitive devices are commonly used for electric power generation. However, devices such as photo-voltaic cells suffer from low efficiency of conversion of solar energy into useable power. Usually, efficiency of the photo-voltaic cells lies in the range of about 20% to 30%. In addition, the photo-voltaic cells are capable of using radiations lying in visible range of a spectrum of solar radiations. Moreover, the photo-voltaic cells are costly to manufacture. Other devices, such as solar heaters and solar cookers, also suffer from low efficiency in terms of utilization of the solar energy incident thereon.
[0015] Further, solar-thermal power generation systems (hereinafter referred to as systems) have been conventionally developed on a large scale for thermal power generation. Such systems involve generation of steam using solar energy and then using the steam to operate a turbine, and hence, to generate useable power. However, construction of such systems employ large amount of infrastructure in terms of land and construction material, such as steel, and hence, incur large capital investment. Furthermore, such systems are usually slow start-up systems, i.e., the systems usually take a few hours, say 3 or 4 hours, before they can constantly start producing useable power.
[0016] The present subject matter describes a device for generating steam, which may be used in a thermal power system. The device includes a base, a floatation body attached to the base, and a transparent cover disposed on the base. The device is configured to float on the surface of a water body, for example, reservoir, lake, pond, or stagnant part of a sea away from shore. In an example, the device is placed on the surface of a substantially stagnant water body. Further, the water body can also include a waste water body, such as sewage tanks. In use, the water from the water body enters and accumulates in the base, and is heated by the solar radiations, and is converted into steam.
[0017] In an embodiment, the base can be formed as a hollow container in the shape of a right truncated cone, also understood as a cone frustum. In one example, the base is formed as a circular cone frustum. When placed on the surface of the water body, surface of the base having smaller diameter, referred to as a floor of the base, rests on the surface of water. The other end of the base, having greater diameter, is open, and is referred to as open side of the base. Hence, when placed on the surface of water, the base appears as a bowl. In said

embodiment, the floor of the base is made thicker than lateral slanting walls of the base, so that the base is able to withstand the stress due to weight of the transparent cover at the top and the water surface from the bottom. With such a construction of the base, the floor of the base is heavy and the centre of the gravity of the device lies at about the same level as the surface of water, which enhances the stability of the device and prevents the device from toppling.
[0018] In another embodiment, the base can be formed as a circular plate. In said embodiment, the base can be considered to include only the floor.
[0019] In an implementation, the base can be made of a light-weight material, which is resistant to corrosion and poor conductor of heat. In one example, the base is made of pultruded fibreglass, which is comprised of fibres and resins. The fibres reinforce the structure of the fibreglass and impart structural stiffness to the base, whereas the resin imparts corrosion resistance, for example, chemical resistance and heat resistance. The fibreglass also has low density and low thermal conductivity. The low density of the fibreglass provides buoyancy to the base and the low thermal conductivity provides insulation and prevents unnecessary loss of thermal energy from the base.
[0020] Further, the material of the base is selected to have high emissivity. In case of fibreglass being used as the material for the base, the base exhibits high emissivity. As a consequence of high emissivity of the base, the solar radiations absorbed by the base are further emitted as radiations. In one example, the radiations emitted by the base have wavelength lying in a range from about 6.4 µm (microns) to about 20 µm. Such radiations are readily absorbed by water and impart energy to the water. In another embodiment, the base can be lined with an emissive coating to impart high emissivity to the base.
[0021] In addition, the floor of base can be designed to allow the ingress of water into the base. For allowing ingress of water into the base, a plurality of pores can be provided in the floor of the base that allow inlet of water into the base. In an embodiment, the pores can be provided in the shape of a nozzle with the diameter of the pores gradually increasing from an outer surface of the floor towards an inner surface of the floor. With such a construction of the pores, the velocity with which the water enters the pores is high and the velocity reduces as the water moves inwards through the pores and emerges at the surface inside the base. As a

result, substantial stagnation of water inside the cavity of the base is achieved, which facilitate uniform heating of water in the base. Further, with the stagnation of water in the base, the uniform heating of water takes place throughout the volume of water, resulting in substantial amount of boiling of water and considerably less evaporation. Consequently, the steam obtained from the device by boiling the water has substantially less wetness and correspondingly high quality.
[0022] In an embodiment, the plurality of pores in the floor of the base can have different diameters. In said embodiment, the pores lying near the circumference of the base in proximity to the lateral slanting side walls have a small diameter and the pores in proximity to the centre of the base have large diameters, with the diameters progressively increasing from the periphery towards the centre of the base. Further, the pores are distributed in such a way that the incoming water forms various laminar flow paths inside the base and does not create turbulence in the water in the base. The lack of turbulence in the water inside the base further facilitates in the uniform distribution of the heat in the volume of water in the base.
[0023] Further, the transparent cover is placed on the open side of the base, for example, on a rim or circumference of the open side of the base. In another embodiment, in which the base is formed as a circular plate, the transparent cover is supported on an edge of the base. In said embodiment, the transparent cover can be fixed onto the base to provide a leak-proof joint between the base and the transparent cover.
[0024] In an embodiment, the transparent cover is formed of glass in the shape of a truncated sphere. The spherical shape of the transparent cover does not require a change in the orientation of the device with respect to the position of sun during changing seasons or variation in the altitude and position of the sun during the day. The spherical shape of the transparent cover ensures the solar radiations are uniformly distributed over the surface of water in the base, throughout the day and during different seasons. In an example, the transparent cover can be formed as a hemi-sphere having a crescent-shaped cross-section. In said example, the thickness of the transparent cover is greatest at the central portion of the surface and decreases at the edges. According to such an embodiment, the transparent cover can be designed to function as a convex lens, which focuses the solar radiations towards the

water in the base. Further, such a structure of the transparent cover can add to the stability of the device.
[0025] Further, the base of the device can have the floatation body attached near the floor of the base. In an embodiment, the floatation body is in the shape of a hollow disc having its edges folded away from the surface of water. Further, the edges can be coated with a reflective coating to reflect the incident solar radiations onto the water in the base. This assists in enhancing the operational efficiency of the device. Further, the floatation body also exhibits good heat insulation properties and further aids in insulating the water stored in the base.
[0026] According to an aspect of the present subject matter, scalability of such a device and thermal power system is very high. For example, a few devices and the associated thermal power system, on one hand, can be used in a pond of a village to generate a few kilowatts of power. On the other hand, a large number of devices can be used in large scale thermal power systems to generate large amount of electric power. Further, the device for generating steam, as described herein, can be used for a quick start-up thermal power system, in which useable power can be obtained within a couple of hours from starting the set-up.
[0027] In addition, the device can find application in sewage treatment plant, where the waste sewage can be collected in the base of the device. The water, converted into steam by the device, can be collected and used for, for example, drinking purposes. In another implementation, the device can be used for off-shore applications, for example, on surface of a salt-water body. In said implementation, the device can, on one hand, serve for obtaining useable salt from such salt-water body, and on the other hand, be coupled to the thermal power system for generation of useable electric power.
[0028] These and other advantages of the present subject matter are described in greater detail in conjunction with the figures.
[0029] Fig. 1 illustrates a device 100 for generating steam, in accordance with an embodiment of the present subject matter. The device 100 can include a base 102, a transparent cover 104, and a floatation body 106. In one example, the device 100 can be placed on the surface of a substantially stagnant water body, such as a reservoir, pond, lake, or stagnant portion of a sea. In another example, the device 100 can be placed on the surface of a waste water body, such as a sewage tank. In one implementation, the device 100 can be

partially or completely submerged under the surface of the water body. The water from the water body enters the device 100 through the base 102, is heated in the base 102 by solar radiations to generate steam. In an embodiment, the floatation body 106 is attached to the base 102 to provide buoyancy to the device 100 for floating on the surface of the water body.
[0030] According to an embodiment of the present subject matter, the base 102 of the device 100 is formed as a hollow container. In said embodiment, the base 102 can be formed in the shape of a truncated right cone, such a shape also referred to as cone frustum. Further, according to an embodiment, the surface of the base 102 having smaller diameter is placed on the surface of the water body to form a wide-mouthed bowl placed on the surface of the water body. The surface of the base 102 on which the device 100 rest on the water is referred to as floor (not shown in figure) of the base 102, whereas the surface of the base 102 opposite to the base 102 is open and is referred to as open side of the base 102. In an embodiment, one or more pores are provided in the floor of the base 102 to allow entry of water from the water body into the base 102.
[0031] In another embodiment, the base 102 can be formed as a plate. In one example, the base 102 can be formed as a circular plate and can be considered to be comprised of only the floor.
[0032] The base 102 can be made of a light-weight material, which is resistant to corrosion and poor conductor of heat. In one embodiment, the base 102 is made of pultruded fibreglass having fibres and resins. The fibres facilitate in imparting structural stiffness to the base 102, whereas the resin imparts corrosion resistance, for example, chemical resistance and heat resistance. The fibreglass also has low density and low thermal conductivity, the low density providing buoyancy to the base 102 and the low thermal conductivity providing insulation and preventing unnecessary loss of heat from the steam in the device 100 to the surroundings through the base 102. Further, fibreglass also exhibits high emissivity, as a result of which the solar radiations absorbed by the base 102 are emitted having wavelength in a certain range. In one example, the base 102 emits radiations lying in a range of wavelength from about 6.4 µm (microns) to about 20 µm. Such radiations emitted by the base are readily absorbed by water and impart energy to the water.

[0033] In another embodiment, the base 102 can be lined with an emissive coating to impart high emissivity to the base 102. In said embodiment, the emissive coating can be of different materials, such as an alloy of nickel, chromium, and iron; carbon lampblack; platinum black; lampblack oil paint; lacquer black; acetylene soot; kylon paint; alkyl enamel broma paint; or black spray enamel paint.
[0034] The structure of the base 102 is discussed in detail with reference to Fig. 2.
[0035] Further, the transparent cover 104 of the device 100 is placed over the base 102 to envelop the open side of the base 102. In an embodiment, the transparent cover 104 is formed in the shape of a transparent truncated sphere and placed on a rim of the open side of the base 102. In another implementation, in which the base 102 is formed as a plate, the transparent cover 104 is placed on an edge of the base 102 to cover the surface of the base 102. The transparent cover 104 can be fixed onto the base 102 to provide a leak-proof joint between the base 102 and the transparent cover 104.
[0036] In one example, the transparent cover 104 can be formed in the shape of a hemisphere with a crescent-shaped cross-section, such that thickness of the transparent cover 104 is greatest at a central portion of surface of the transparent cover 104 and reduces at the edges. Such a structure of the transparent cover 104 serves as a lens and facilitates in concentrating the radiant flux towards the water in the base 102. Further, with such a structure of the transparent cover 104, centre of gravity of the device 100 shifts to around the surface of the water body. In addition, the heavy structure at the central portion of the transparent cover 104, as a result of the thickness, ensures structural strength of the transparent cover 104 to withstand high steam pressures built-up inside the device 100.
[0037] In another embodiment, the transparent cover 104 can be formed integral to the base 102. In said embodiment, the transparent cover 104 and the base 102 can be formed of the same material.
[0038] Further, with the provision of the transparent cover 104 in a spherical shape, the transparent cover 104 is capable of concentrating solar radiations towards the water in the base 102, without changing the orientation of the device 100 with respect to change in position of the sun during changing seasons or change in altitude of the sun during a day.

[0039] Further, according to an embodiment of the present subject matter, the transparent cover 104 is formed of glass, which allows passage of certain radiations, such as visible radiations of the solar spectrum, into the device 100. In an example, use of glass for the transparent cover 104 allows all the radiations having a wavelength ranging from about 300 nanometer (nm) to about 1500 nm to be transmitted by the transparent cover 104 into the device 100. Since most of the solar radiations reaching the earth’s surface lie within the wavelength of 300 nm to 1500 nm, such a transparent cover 104 facilitates in transmitting a considerable amount, say about 90%, of solar radiations onto the water in the device 100. Further, the radiations re-emitted by the base 102 and the water in the base 102 lie within a range of wavelength of about 2500 nm to about 5000 nm, i.e., infrared radiations, which are high energy radiations. Such high wavelength radiations are not allowed to escape by the transparent cover 104 and are trapped in the device 100. As a result, the transparent cover 104 facilitates in creation of greenhouse effect inside the device 100. The high energy radiations trapped in the device 100 facilitate in rapid heating of the water in the base 102 and enhance overall thermal efficiency of the device 100.
[0040] Additionally, such a transparent cover 104 is structurally stable and does not have any residual internal stresses and provides good insulation for the steam generated in the device 100. In addition, the transparent cover 104 made of glass exhibits chemical inertness towards water at different temperatures and is thermally stable at different temperatures. Further, the material of the transparent cover 104 can be selected based on the heating requirements inside the device 100.
[0041] In an embodiment, the transparent cover 104 can also be provided with an anti-reflective coating. The anti-reflective coating can be provided on the outside surface or inside surface or both surfaces of the transparent cover 104. The anti-reflective coating reduces the reflection of solar radiations, and the hence, reduces the energy lost due to reflection of the radiations, from the surface of the transparent cover 104. As a result of the provision of the anti-reflective coating on the transparent cover 104, the overall thermal efficiency of the device 100 is improved.

[0042] In an embodiment, material of the anti-reflective coating is magnesium fluoride (MgF2). Further, thickness of the anti-reflective coating to be applied on the surface of the transparent cover 104 can be determined based on the following relation:
tanti-reflective = λincident /4 …..(1)
[0043] In relation (1), tanti-reflective depicts the thickness of the anti-reflective coating and λincident is the wavelength of radiations incident onto the transparent cover 104. In an example, the thickness of the anti-reflective coating on the transparent cover 104 is about 138 nm.
[0044] In another embodiment, the surface of the transparent cover 104 can be textured. In one example, micro texturing technique is used for surface texturing the surface of the transparent cover 104. In said example, the surface of the transparent cover 104 is exposed to laser pulses of a wavelength of about 800 nm and a frequency of about 1 pulse per 100 femtoseconds (fs). With surface texturing, various crest-like structures are formed on the surface which increase the area of the surface of the transparent cover 104 and facilitate in capturing photons at the surface. In an example, the surface of the transparent cover 104 can be partially or completely textured.
[0045] The available radiant flux for heating the water in the device 100, is a design constant, and is dependent on size of the transparent cover 104 and size of the base 102. Hence, depending upon available radiant flux for heating, the sizes of base 102 and of the transparent cover 104 can be determined. In an example, in case of a circular base 102 and a spherical transparent cover 104, the relation between the available radiant flux and the sizes of the base 102 and the transparent cover 104 is elucidated by the following relation:
Available radiant flux = Normal radiant flux {1 + (dtransparent cover – dbase)} …..(2)
[0046] In the above relation, the dtransparent cover depicts diameter of the spherical transparent cover 104 and dbase depicts diameter of the base 102 measured at the rim at the open side.
[0047] In addition, as mentioned previously, the device 100 can include a floatation body 106. The floatation body 106 provides buoyancy to the device 100, along with providing structural stability and facilitating insulation of the device 100. According to an embodiment, the floatation body 106 is attached to the base 102. In another embodiment, the device 100

can be configured to be partially or completely immersed in water and, in said embodiment, the floatation body 106 can be fastened to the transparent cover 104.
[0048] The floatation body 106, in one embodiment, is formed in the shape of a hollow disc. The internal measurements of the floatation body 106 correspond to the portion of the device 100 to which the floatation body 106 is attached. For example, if the floatation body 106 is attached to the base at the circular floor of the base 102, then an internal diameter of the hollow disc-shaped floatation body 106 corresponds to the diameter of the floor of base 102.
[0049] Further, edges of the floatation body 106 can be curved away from the surface of the water body. Such a structure of the floatation body 106 prevents water from splashing onto the transparent cover 104, which can otherwise deposit on the surface of the transparent cover 104 and reduce clarity of the transparent surface. In an embodiment of the present subject matter, curved surfaces formed by curving the edges of the floatation body 106 are lined with reflecting material to obtain concave reflective surfaces. Such curved reflective surfaces on the floatation body 106 serve to provide a catchment area for capturing the radiant flux, for example, the radiant flux reflected from the transparent cover 104, the radiant flux emitted by the transparent cover 104, and the radiant flux incident on the floatation body 106 directly from the source, i.e., sun. The provision of the curved reflective surfaces on the floatation body 106 enhances the overall thermal efficiency of the device 100. In one example, the overall thermal efficiency of the device 100 can be improved by about 15% to 30% with the provision of such curved reflective surfaces on the floatation body 106.
[0050] According to an embodiment, the floatation body 106 can be formed of ceramic alumina (Al2O3) encased in polypropylene. The ceramic alumina can, in one example, be provided in the form of spherical shells. Such a float has a density which, on one hand, is considerably lower than density of water and, on the other hand, is considerably higher than density of air. As a result, the float provides good floatation as well as good stability to the structure. Further, in said embodiment, the provision of propylene for encasing the ceramic alumina prevents absorption of water by the ceramic alumina, and hence, prevents loss of buoyancy of the floatation body 106. In addition, the material imparts stiffness and high degree of thermal insulation to the water in the device 100.

[0051] The size of the floatation body 106 plays an important role on the floating ability of the device 100 on the water surface. A volume of the floatation body 106 is based on the size and material of the base 102 and the transparent cover 104. In one implementation, the volume of the floatation body 106 to be used in the device 100 can be computed based on the following relation:
Vfloat = [Vtransparent cover .(ρtransparent cover/(ρwater–ρfloat)]+[Vbase .((ρbase–ρwater)/(ρwater –ρfloat))] ….(3)
[0052] In the above relation (3), V and ρ depict the volume and density, respectively, of the different components of the device 100 and of water.
[0053] The device 100 includes an exit duct 108 provided for the exit of steam from the device 100. In an embodiment, the exit duct 108 is provided at a top of the transparent cover 104. Having the exit duct 108 at the top of the transparent cover 104 allows easy and natural flow for exit of the steam generated in the device 100.
[0054] Further, the device 100 can include a sediment expulsion mechanism (not shown in figure). According to an embodiment, the sediment expulsion mechanism can be provided as a flap valve at a bottom portion of the base 102. In an implementation, sediment expulsion mechanism is provided in the floor of the base 102. In said implementation, the sediment expulsion mechanism can be opened for removing silt and sediment present in the water and collected on the floor of the base 102. The removal of sediment, such as soluble salts, avoids re-dissolution of the sediment in the water and improves flow characteristics of the water.
[0055] In an implementation, the sediment expulsion mechanism can be operated by a control device (not shown). In one example, the control device is calibrated to regulate an opening and closing of the sediment expulsion mechanism on the basis of weight of sediment on the floor of the base 102. Further, in an implementation, the sediment expulsion mechanism can include one or more wipers for expelling the sediment from the base 102. In an example, the operation of the wipers is also controlled by the control device based on, for example, the weight of sediment settled on the floor of the base 102.
[0056] In another example, the wipers of the sediment expulsion mechanism can be operated by a mechanical system. In said example, a fan (not shown in figure) can be provided in the exit duct 108, which is operated by the steam exiting the device 100. Further,

rotation of the fan can be translated into the movement of the wipers for removing sediment from the floor of the base 102. For example, the fan can be coupled to a wiper shaft, driving the wipers, through a gear train which transfers and multiplies the torque produced by the rotation of the fan and provides a greater torque at the wipers.
[0057] In yet another example, the control device can be calibrated to control the sediment expulsion mechanism based on the amount of steam being generated by the device 100.
[0058] Fig. 2 illustrates a cross sectional view of the base 102 of the device 100, in accordance with an embodiment of the present subject matter. As described earlier, in one embodiment, the base 102 is formed as a circular cone frustum. In an implementation, the base 102 is placed on the water surface with a floor 200 of the base 102 making contact with the water surface. In said implementation, hence, the base appears like a bowl placed on the water surface. The circular shape of the base 102 imparts structural stability to the base 102, and the uniformity of the shape helps in uniform exposure of the base 102 to solar radiations.
[0059] According to an embodiment, the floor 200 is thicker than side walls 202 of the base 102 to provide strength to the floor 200. With such provision, the floor 200 is capable of enduring stresses due to weight of the transparent cover 104 and also the stresses due to the thrust of water. Further, a vertical height of the base 102 is one of the factors for determining the stability of the device 100 placed on the water surface. Hence, the base 102 is designed considering a height of the centre of gravity of the device 100 with reference to the water surface of the water body. In one implementation, the base 102 is designed in such a way that the centre of gravity of the device 100 is at a level in proximity of the water surface of the water body. Such a design assists in achieving stability of the device 100.

[0061] In the above relation, hCG water represents the height of CG of water in the base 102, hbase represents a height of the base 102, dbase top represents a maximum diameter of the base,
[0060] A height of centre of gravity (CG) of water contained in the base 102, when the base 102 is placed on the water surface, is given by the following relation:

measured at the surface which is farthest from the water surface, and dbase floor represents a minimum diameter of the base 102, which is measured at a bottom most part of the base, i.e., the floor 200.
[0062] Further, the height of CG of the base 102 is represented by the following relation:

[0063] In the above relation (5), hCG base represents height of CG of the base 102 and k represents the factor by which the floor 200 is thicker than the side walls 202.
[0064] The actual height of CG of the base 102, when placed on water surface and containing the water, is given by a combination of the above two relations. Consequently, the actual height of CG of the base 102 is represented by the following relation:

[0065] In the above relation, hactual CG base represents the actual CG of the base 102 and ρ represents the densities of different components of the base 102 and of water. Based on the above relation, the height of CG of the base 102 can be determined and the base 102 can be designed for providing optimal stability to the structure. Further, the height of the base 102 and the height of the CG of the base 102 is determined and selected such that the base 102 is slightly under the surface of water. With such a provision, floating materials, such as plastics and oil, which can hamper the operation of the device 100, do not enter the base 102. Hence, with such a design of the base 102, the efficiency of the device 100 is not affected.
[0066] Further, in an embodiment, a plurality of pores 204 are provided in the base 102 for ingress of water into the base 102. In said embodiment, the pores 204 are provided in the floor 200 such that when the device 100 is placed on the water surface, water enters the base 102 through the pores 204. The weight of the device 100 takes the base slightly under the water surface and, as a result of the downward thrust due to weight of the device 100, water enters the base 102 through the pores 204.

[0067] The steam generated by the device 100 is dependent on the number of pores 204 that are open. In one embodiment, the device 100 can include a pore valve (not shown), which is operated by a control device (not shown) to open and close one or more pores 204. In an implementation, the control device can be calibrated to operate the control device for opening or closing the pores 204 based on the amount of steam to be obtained from the device 100.
[0068] According to an embodiment of the present subject matter, each of the pores 204, individually referred to as pore 204, is provided in the shape of a circular nozzle. In other embodiments, the pores 204 can have other cross-sectional shapes, such as polygonal. According to an embodiment, the pore 204 has a small diameter at an opening in an outer surface 206 of the floor 200 and the diameter gradually increases from the outer surface 206 to an inner surface 208 of the floor 200. In one embodiment, the inner surface 208 of the floor 200 is filleted at the outlet of the pores 204 to provide a convex shape at the outlet of the pores 204 at the inner surface 208. Such a shape of the pores 204 at the outlet facilitates in achieving stagnation of water entering the base 102.
[0069] Hence, it will be understood that, in said embodiment, the pore 204 is designed as an inverted nozzle having the nozzle end towards the water surface, with a small inlet diameter measured at the outer surface 206 and a large outlet diameter measured at the inner surface 208 of the floor 200. In one example, the amount of steam to be generated is one of the factors for determining the size of the pores 204 and angle of taper of the pores 204. The angle of taper can be understood as the angle made by the slanting lateral wall of each pore with the longitudinal central axis of the pore.
[0070] As a result of formation of the pores 204 in the shape of a nozzle, water enters the base 102 through the pores 204 at a high velocity, which provides a thrust for removing any impurities blocking the pores 204. Further, as the water gradually reaches the base 102 through the pores, the velocity of water reduces as the water emerges at the surface in the base 102. As a result, substantial stagnation of water is achieved inside the base 102, which further facilitates in uniform heating of water in the base 102. Further, as a result of the uniform heating of water, the heating of water takes place throughout the volume resulting in substantial amount of boiling of water and considerably less evaporation. Consequently, the

steam obtained from the device 100 is by boiling and the steam has substantially less wetness and correspondingly high quality.
[0071] Further, according to an embodiment, different pores 204 can have different diameters. According to said embodiment, the pores 204 in proximity of the side walls 202 have a small outlet diameter measured at the inner surface 208 of the floor 200. Further, the outlet diameters of the pores 204 gradually increase, in said embodiment, towards the centre of the base 102. Hence, the outlet diameters of the pores 204 in proximity to the centre of the base 102 have greater outlet diameters than the pores in proximity to the side walls 202. As will be understood, the outlet diameter of the pore 204 is the diameter measured at the point where water exits the pore 204, i.e., at the inner surface 208 of the floor 200. Such a configuration of the pores facilitates in mitigating turbulence in the water flow into the base 102.
[0072] The distribution of the pores 204 in the floor 200 of the base 102 influences the flow characteristics of the water entering the base 102 through the pores 204. Accordingly, the pores 204 are uniformly distributed in the floor 200 at constant intervals. The distance between two adjacent pores 204 can be determined based on average inlet velocity of water entering the base 102, which in turn depends on the weight of the device 100. The distance between adjacent pores 204 is determined to be such that the water entering the base 102 from the adjacent pores 204 forms a laminar flow path. Such flow of water reduces the turbulence in the water collected in the base 102 and, at the same time, helps in mixing the water for uniformity of temperature throughout the volume of water.
[0073] As described previously, in another embodiment, the base 102 can be formed as a plate, and in said embodiment, the base 102 comprises only the floor 200. Further, in said embodiment, the plurality of pores 204 is provided in the plate-shaped base 102 for inlet of water into the device 100.
[0074] The device 100 for generating steam as described above can be implemented for various purposes. In one example, the device 100 can be used for sewage/sludge treatment by placing the device 100 on the waste water surface. The impurities and wastes in the waste water are left behind, whereas the steam leaving the device 100 can be captured and used further, for example, for drinking or in batteries.

[0075] In another example, the device 100 can be implemented for salt extraction. In such an implementation, the device 100 is placed on the surface of a salt-water containing water body. Upon evaporation of the water in the form of steam, the salt is left behind as sediment. The salt is then removed from the device 100 with the help of the sediment expulsion mechanism as explained before.
[0076] The device 100 can also be employed in a thermal power system. Fig. 3 illustrates a schematic of a thermal power system 300 implementing the device 100 for generating steam. The thermal power system 300 utilizes hot steam to run a turbine 302 coupled to a generator 304. The generator 304, in turn, generates electric power, which can either be directly used or can be stored for later use. In an embodiment, the turbine 302 used in the thermal power system 300 can be an impulse turbine.
[0077] As explained earlier, the exit duct 108 allows the exit of the hot steam from the device 100. In an embodiment, the exit duct 108 is connected to a super heater system 306 of the thermal power system 300. In the super heater system 306, the steam from the device 100 is heated to high temperatures using solar energy and substantially dry and superheated steam is obtained.
[0078] In an embodiment, the super heater system 306 can include one or more super heater units 308-1, 308-2,……308-N, collectively referred to as super heater units 308 and individually referred to as super heater unit 308. Further, the super heater units 308 are connected to each other through a plurality of controlling devices 310-1, 310-2,….310-N, collectively referred to as controlling devices 310 and individually referred to as controlling device 310.
[0079] In an implementation, the super heater units 308 are connected to each other in series, i.e., steam from a first super heater unit 308-1 is sent to a second super heater unit 308-2 through a first controlling device 310-1, and subsequently from the second super heater 308-2 to a third super heater unit 308-3 through a second controlling device 310-2, and so on. Further, each of the super heater unit 308 of the super heater system 306 is also connected to the turbine 302 of the thermal power system 300 through the controlling device 310. The controlling device 302, in one implementation, can regulate the number of super heater units

308 serving the turbine 302, i.e., supplying steam to the turbine 302, at a time for generating power from the thermal power system 300.
[0080] In another implementation, the super heater units 308 can be connected in parallel and the controlling devices 310 can be configured to measure the cumulative effect of steam from the super heater units 308 for producing the predetermined power. Based on the measurement by the controlling devices 310, the number of super heater units 308 serving the turbine 302 can be controlled. The controlling devices 310 are discussed in detail with reference to Fig. 5.
[0081] The turbine 302 receives super heated steam from the super heater system 306, which impinges on the turbine 302 and causes a rotation of the turbine 302. The rotation of the turbine 302, coupled to the generator 304, causes rotation of the generator 304, for example, of the rotor of the generator 304, and generation of useable electric power.
[0082] Further, exhaust steam from the turbine 302 can be utilized in an economizer 312. In an embodiment, the economizer 312 receives the exhaust steam from the turbine 302 and utilizes the reminiscent heat of the exhaust steam to heat the water in the water body near the base 102 of the device 100. This further helps in improving the operational efficiency of the device 100 and of the thermal power system 300. The steam leaving the economizer 312 can be collected and condensed to obtain distilled water.
[0083] Fig. 4 illustrates the super heater unit 308, according to an embodiment of the present subject matter. In said embodiment, the super heater unit 308 includes a super heater duct 400, which receives hot steam from, for example, the exit duct 108 of the device 100. In one example, the super heater duct 400 can obtain hot steam from serially previous super heater unit 308 in the super heater system 306. Further, the super heater unit 308 can include a concentrating device 402 and a rear wall 404. In an embodiment, the concentrating device 402 is fixed on the rear wall 404 and the super heater duct 400 passes through the assembly of the rear wall 404 and the concentrating device 402. Further, a surface of the rear wall 404, facing the super heater duct 400, can be coated with a reflective coating for concentrating the solar radiations on the super heater duct 400 carrying hot steam, and is referred to as a reflective surface 406 of the super heater duct 400.. In an embodiment, the rear wall 404 can be curved

and the reflective surface 406 is provided on a concave surface of the rear wall 404, facing the super heater duct 400.
[0084] During operation, the concentrating device 402 focuses the solar radiations on the super heater duct 400 to heat the steam in the super heater duct 400. Further, the solar radiations suffering refraction and reflection at the concentrating device 402 and the super heater duct 400, respectively, are further reflected from the reflective surface 404 and incident on the super heater duct 400. In an example, the reflective surface 404 is a concave mirror and the concentrating device 402 is a biconvex lens.
[0085] The concentration of the solar radiations on the super heater duct 400 assists in heating the steam to high temperatures, and hence, in achieving super heated steam. Such super heated steam has almost negligible wetness, i.e., water vapour content. The minimal amount of water vapour in the steam reduces corrosion of the components, such as the turbine 302, of the thermal power system 300. As a result, the maintenance cost of the thermal power system 300 is brought down, without additional expenditure of energy on super heating the steam.
[0086] Fig. 5 illustrates the controlling device 310, according to an embodiment of the present subject matter. As described earlier, the controlling device 310 includes a control unit 500 to regulate the number of super heater units 308 that are supplying steam to the turbine 302. In said embodiment, the controlling device 310 is provided at an outlet of the super heater unit 308 and receives super heated steam from the super heater unit 308. Further, the control unit 500 is configured to analyze whether the steam received after from the super heater unit 308, say the first super heater unit 308-1, is capable of running the turbine 302 in such way that a predetermined amount of power is generated by the generator 304. The controlling device 310 includes a valve regulator 502, which is regulated by the control unit 500, based on the analysis, to direct the steam from the super heater unit 308 to the turbine 302 or to a subsequent super heater unit 308, say the second super heater unit 308-2. In an embodiment, the controlling device 310 includes a valve 504 for regulating the flow of steam to the turbine 302 and the subsequent super heater unit 308.
[0087] In an embodiment, the controlling device 310 includes a temperature sensor 506 and a velocity sensor 508 to measure steam parameters, i.e., temperature and velocity,

respectively, of the incoming steam from the super heater unit 308. The steam parameters are indicative of the condition of the steam exiting the super heater unit 308 and entering the controlling device 310. Further, the temperature sensor 506 and the velocity sensor 508 provide measured values the steam parameters of the incoming steam as inputs to the control unit 500. Based on the measured values, in an implementation, the control unit 500 can be configured to determine the amount of power that the generator 304 can generate, when this steam is impinged on the turbine 302 to run the turbine 302. In one example, the velocity sensor 508 can be a fan calibrated to measure the velocity of steam incident thereon.
[0088] If the determined power is equal to or greater than the predetermined power, then the control unit 500 induces the valve regulator 502 to operate the valve 504 and directs the steam towards the turbine 302. In another case, if the measured power is less than the predetermined power, then the controlling device 310 causes an actuation of the valve 504 to direct the steam towards the subsequent super heater unit 308 for further heating. In one example, the valve regulator 502 can be an actuator, such as a motor.
[0089] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. It is to be understood that the appended claims are not necessarily limited to the features described herein. Rather, the features are disclosed as embodiments of the device 100 for generating steam.

I/We Claim:
1. A device (100) for generating steam when positioned on a water body, the device (100)
comprising:
a base (102) comprising a floor (200), wherein the floor (200) comprises a plurality of pores (204) for entry of water into the base (102) from the water body;
a floatation body (106) attached to the base (102) to provide buoyancy to the device (100); and
a transparent cover (104) disposed on the base (102), wherein the transparent cover (104) directs solar radiations onto the water in the base (102) to generate steam.
2. The device (100) as claimed in claim 1, wherein the floor (200) of the base (102) is thicker than side walls (202) of the base (102).
3. The device (100) as claimed in claim 1, wherein the plurality of pores (204) are formed in shape of an inverted nozzle having a smaller inlet diameter than an outlet diameter, and wherein the inlet diameter is measured at an outer surface (206) of the floor (200) and the outlet diameter is measured at an inner surface (208) of the floor (200).
4. The device (100) as claimed in claim 1, wherein the plurality of pores (204) in proximity of side walls (202) of the base (102) have smaller outlet diameter than outlet diameter of the plurality of pores (204) in proximity of a centre of the floor (200) of the base (102).
5. The device (100) as claimed in claim 1, wherein the base (102) comprises pultruded fibreglass.
6. The device (100) as claimed in claim 1, wherein the base (102) is coated with an emissive coating to impart high emissivity to the base (102).
7. The device (100) as claimed in claim 1 further comprising a sediment expulsion mechanism for releasing sediment from the device (100).
8. The device (100) as claimed in claim 7, wherein the sediment expulsion mechanism is provided in the base (102), and wherein the sediment expulsion mechanism is a flap valve.
9. The device (100) as claimed in claim 7, wherein the sediment expulsion mechanism comprises at least one wiper for expelling sediment from the device (100), and wherein

the at least one wiper is coupled to a mechanical system operated by the steam generated from the device (100).
10. The device (100) as claimed in claim 1, wherein the floatation body (106) comprises curved edges lined with reflective material, and wherein the curved edges of the floatation body (106) are curved away from the water body.
11. The device (100) as claimed in claim 1, wherein the floatation body (106) comprises ceramic alumina encased in polypropylene.
12. The device (100) as claimed in claim 1, wherein the transparent cover (104) is formed as a truncated glass sphere having a crescent-shaped cross-section.
13. The device (100) as claimed in claim 1, wherein the transparent cover (104) is coated with an anti-reflective coating to prevent reflection of incident solar radiations from the transparent cover (104).
14. The device (100) as claimed in claim 1, wherein a surface of the transparent cover (104) comprises a textured surface for capturing incident solar radiations.
15. A thermal power system (300) comprising:
a device (100) for generating steam, wherein the device (100) comprises,
a base (102) comprising a plurality of pores (204) for entry of water from a water body into the base (102); and
a transparent cover (104) disposed on the base (102) for enclosing an open side of the base (102), wherein the transparent cover (104) directs solar radiations onto the water inside the base (102) for generating steam;
a super heater system (306) for heating the steam generated in the device (100); and
a turbine (302) coupled to a generator (304), wherein the steam from the super heater system (306) is impinged upon the turbine (302) to actuate the generator (304) to produce useable power.
16. The thermal power system (300) as claimed in claim 15, wherein the super heater
system (306) comprises a plurality of super heater units (308), each super heater unit
(308) comprising:

a super heater duct (400) for receiving steam;
a concentrating device (402) for directing solar radiations onto the super heater duct (400) carrying the steam to heat the steam; and
a rear wall (404) comprising a reflective surface (406) for directing solar radiations directed by the concentrating device (402) and the solar radiations reflecting off the super heater duct (400), onto the super heater duct (400) for heating the steam.
17. The thermal power system (300) as claimed in claim 16, wherein the plurality of super heater units (308) in the super heater system (306) are connected in series.
18. The thermal power system (300) as claimed in claim 15, wherein the super heater system (306) further comprises at least one controlling device (310) to regulate a number of super heater units (308) supplying the steam to the turbine (302).
19. The thermal power system (300) as claimed in claim 18, wherein the controlling device (310) comprises:
at least one sensor (506, 508) to determine at least one steam parameter, wherein the steam parameter is indicative of a condition of the steam;
a control unit (500) configured to,
determine, based on the steam parameter, whether the steam is capable of generating a predetermined amount of power, and
actuate a valve (504) to direct the steam to one of the turbine (302) and a subsequent super heater unit (308), based on the determining.
20. The thermal power system (300) as claimed in claim 18, wherein the controlling device
(310) is provided at an exit of at least one of the device (100) and one or more super
heater units (308).