Abstract: A photothermal seawater desalination material with a multi-stage structure and a preparation method and application thereof. The photothermal seawater desalination material includes a light-absorbing material having a C/WO3-x heterogeneous junction, which is obtained by depositing a nano-C material on a porous metal foam material using plasma enhanced chemical vapor deposition (PECVD), and then synthesizing WO3-x with plasma resonance effect by a solvothermal reaction.

Abstract: Technical challenges of efficiently and cost-effectively deriving energy from the sun are addressed using a manifold and an array of evacuated tubes in fluid connection, in a butterfly or other planar arrangement. Tube and manifold fluid guides are plumbed for coaxial flow and/or parallel flow, and thermally protected by sleeves, stainless steel piping, and/or vacuum. Tubes are provided with a selective low emissivity coating and/or internal mirror to reduce thermal loss. The solar absorption surface of evacuated tubes may be five square meters or more, with only low-quality concentration optics, or no concentration optics used. The tubes array tracks the sun with a two-axis motion platform. Fluid operating temperatures range from 150 to 300 degrees centigrade, depending on the sunlight exposure, working fluid, and supplemental heat source if any. Fluid may circulate heat between the manifold and heat engine, cogeneration facility, and/or other module.

Abstract: A method of forming a spectral selective coating is disclosed. The method may include providing particles on a substrate, wherein the particles include submicron particles. The method may farther include sintering the particles under atmospheric pressure to form a sintered layer an the substrate and texturing the sintered layer to provide a submicron surface roughness height on the sintered layer.

Abstract: A solar collector receiver tube containing an improved getter system is described. The solar collector receiver tube has a base, pills of getter material that are uniform in height, and a containment metallic mesh having a non-uniform height and presenting at least one depression.

Abstract: Techniques, systems, devices and materials are disclosed for spectrally selective coatings for optical surfaces having high solar absorptivity, low infrared emissivity, and strong durability at elevated temperatures. In one aspect, a spectrally selective coating includes a substrate formed of a light absorbing material, and a composite material formed over the substrate and including nanoparticles dispersed in a dielectric material, in which the composite material forms a coating capable of absorbing solar energy in a selected spectrum and reflecting the solar energy in another selected spectrum.

Abstract: A solar thermal collector including a carrier, channels and a solar selective coating is provided. The channels are embedded in the carrier for a heat transfer fluid flowing therein. The solar selective coating is deposited on an outer surface of the carrier. The solar selective coating includes a damping layer, an absorbing layer and an anti-reflecting layer. The damping layer is deposited on the outer surface of the carrier. The absorbing layer is deposited on the damping layer, wherein the absorbing layer has a transition region including plural sub-layers and located adjacent to the damping layer. The anti-reflecting layer is deposited on the absorbing layer, wherein a light beam is adapted to enter the absorbing layer through the anti-reflecting layer, and irradiation energy of the light beam is transformed by the collector into thermal energy, which is then transmitted to the heat transfer fluid in the channels.

Abstract: The present invention offers improved absorber plates for solar energy collectors, improved cover glazings for solar energy collectors, improved concentrating solar energy collectors, and solar energy collection methods that use one or more of the improved solar energy collectors for useful residential, commercial, and industrial applications. The improved absorber plate solar energy collectors utilize a porous metal to improve solar radiant absorption collection and utilization, the improved concentrating solar energy collectors are Fresnel lens faced ducts of various geometries that enable efficient axial length solar energy collection, and the improved cover glazings utilize transparent front and back faces with other improvements to enable increased solar radiant energy collection per unit front face cover area of solar collector.

Abstract: Solar heat collector, especially an evacuated-tube solar heat collector, filled with first solid heat storage and conducting material transfers the solar heat to an electric power heat insulated utensil through second heat conducting/transferring material for cooking foods and making coffee/tea. A set of solar cooking appliance having a solar heat collector filed with a first solid heat storage and conducting material and a solar cooking range filled with third solid heat storage and conducting material. The solar cooking range having a heat insulated enclosed compartment and also having a cooktop. The cooking range having a set of cooking chambers which are in thermal contact with the first and second heat storage and conducting material for cooking food therein. The cooking appliance also has a group of removable parts that cover the cooking chambers separately. An electric power heater provides a backup energy source and electric heat storage.

Abstract: A solar heat collector includes a heat collecting board, a solar radiation absorbing layer provided at one surface in a thickness direction of the heat collecting board, and a low emissivity and low solar reflectance layer provided at one surface in the thickness direction of the solar radiation absorbing layer.

Abstract: A solar receiver tube assembly is provided with at least one first solar receiver tube with a first selective absorptive coating; at least one second solar receiver tube with a second selective absorptive coating, wherein values of at least one optical characteristic of the first selective coating and the second selective coating differs from each other while an operating the solar receiver tube assembly. The optical characteristics are preferably ? and ?. The idea is to improve the effectiveness of the receiver tubes along the receiver assembly.

Abstract: A layer material for corrosion protection and to a solar receiver having such a layer material is provided. The layer material comprises a binding agent consisting of a resin containing at least one of the following substances: oligo- or polysiloxane, silicone resin, silicone, silicate, polyphosphate, and which is dissolved in a solvent, a pigment consisting of zinc microparticles having an average diameter of at least 1 um, wherein a further pigment consisting of titanium oxide or silicon oxide nanoparticles having an average diameter of no more than 100 nm is present in the layer material. The layer advantageously has a self-healing effect in addition to the corrosion protection effect thereof owing to the use of zinc particles.

Abstract: A paint formulation can include an inorganic oxide-based pigment and an organic binder. The organic binder can be irreversibly converted to an inorganic binder upon curing of the paint formulation at a temperature greater than 200° C. The oxide-based pigment and/or the paint formulation itself can have an absorptivity of at least 80% with respect to the AM 1.5 spectrum. The paint formulation can also include at least one organic solvent, an inorganic filler, and/or at least one additive. Such paint formulations may be stable at high temperatures (e.g., 750° C.) and can be used as solar-radiation-absorbing heat-resistant coatings for components of a solar tower system.

Abstract: A solar receiver includes a cavity that is operable to receive concentrated solar energy and a heat exchanger in thermal-receiving communication with the cavity. The heat exchanger includes a plurality of thermal capacitors. Each of the plurality of thermal capacitors has a regular geometry. The plurality of thermal capacitors defines open flow passages there between and at least two of the plurality of thermal capacitors have a different size. The plurality of thermal capacitors has a packing factor of greater than 74% with regard to the volume of the heat exchanger.

Abstract: A solar power tower solar receiver absorber including: an enclosure; at least one panel configured to be illuminated by solar flux; a core made of at least one material with heat conductivity at least partially encompassed by the enclosure; and a plurality of tubes passing through the core and extending substantially in a parallel direction with respect to the panel configured to be illuminated. The tube is configured for circulation of a fluid to be heated, for example a gas for operating a gas turbine.

Abstract: A solar collector is made primarily of plastic materials. A wide variety of collector configurations may be made from similar parts, and thus the collector may be adapted to mount in locations where traditional flat panel collectors may not be feasible. The collector may conveniently be used with a nanofluid as the heat transfer fluid, to increase the heat transfer characteristics of the heat transfer fluid. A control system for stagnation remediation, freeze protection, or both may be utilized. For example, when the collector is in danger for stagnation or freezing, water may be circulated through a ground coupled heat exchange loop to cool or heat the collector. Preferably, the stagnation remediation mode does not sacrifice thermal energy previously collected and stored.

Abstract: A glass tube with a glass tube wall is provided, wherein an inner surface of the glass tube wall comprises at least partially at least one infrared light reflective coating. Additionally a heat receiver tube for absorbing solar energy and for transferring absorbed solar energy to a heat transfer fluid, which can be located inside a core tube of the heat receiver tube, is provided. The core tube comprises a core tube surface with a solar energy absorptive coating for absorbing solar absorption radiation of the sunlight. The core tube surface and an encapsulation are arranged in a distance between the core tube surface and the inner surface of the encapsulation wall with the infrared reflective surface such, that the solar absorption radiation can penetrate the encapsulation with the infrared light reflective coating and can impinge the solar energy absorptive coating.

Abstract: In an embodiment, an assembly, comprising: a glazing layer; a light absorbing layer; and a thermo-responsive layer between the glazing layer and the light absorbing layer. The thermo-responsive layer comprises a matrix polymer having a glass transition temperature and an inorganic filler, wherein the matrix polymer comprises 0.5 to 10 weight percent of repeat units derived from acrylonitrile, based upon a total weight of the matrix polymer. The refractive indices of the matrix polymer and the inorganic filler differ by less than or equal to 0.05 at 25° C.

Abstract: Systems, methods, and apparatus by which solar energy may be collected to provide electricity or a combination of heat and electricity are disclosed herein. Examples of solar energy receivers are disclosed that may be used to collect concentrated solar radiation.

Abstract: A solar receiver device includes a metal conduit and a glass container disposed around the metal conduit such that there is a space between the glass container and the conduit. A coating is disposed on the metal conduit and has a composition that includes at least one element from silicon, titanium, aluminum, barium, and samarium.

Abstract: The present invention relates to a covering that selectively absorbs visible and infrared radiation, which comprises: (a) a first anti-diffusion barrier layer (2); (b) an IR-reflecting metallic layer (3) made from at least one metallic element selected from a group comprising An, Ag, Al, Cu, Ti and Pt; (c) at least a second anti-diffusion barrier layer (4) formed by oxidation of the layer (3); (d) a structure that absorbs in the UV-VIS range, which comprises at least a first film (5) and a second film (6) made from cermet, which in turn comprises a metallic fraction made from a metal selected from Pt, Cr, Mo, W, Zr, Nb, Ta and Pd, or any alloy thereof, and a ceramic comprising an oxygen-free nitride which is constituted by a metallic oxide in which the metal is selected from aluminium, silicon and chromium; and (e) a dielectric layer that is non-reflecting in the UV-VIS range, which comprises a nitride of at least one metal selected from silicon, aluminium and chromium.

Abstract: A solar receiver for a solar thermal system that is formed with ytterbium hexaboride (YbB6) is provided. A solar thermal system having a solar receiver of this kind is also provided.

Abstract: A thin-film spectrally selective coating for receiver tube of vacuumed type for use in thermodynamic solar installations and operating both at medium temperature (up to 400° C.) and at high temperature (up to 550° C.), coating where the optically absorbing layer is a multilayer of cermet material of type: WyN—AlNx or MoyN—AlNx, material prepared with reactive co-sputtering technique from an Al target and a W or Mo target, process conducted under a transition regimen, under PFM (Plasma Emission Monitoring) or CVM (Cathode Voltage Monitoring) monitoring for the sole Al target, with inletting near the Al target of a N2 amount adequate for obtainment of a high-transparency, high growth rate sub-stoichiometric ceramic AlN and with inletting near the W or Mo target of a N2 amount adequate for obtainment of the sole W2N or Mo2N phase, phase very stable at high temperature, such as to make the cermet material as close as possible to the formulation W2N—AlNx or Mo2N—AlNx (with x comprised between 0.90 and 1.

Abstract: A solar radiation absorber element for a thermal concentrating solar power plant is achieved by forming a selective coating on an outer surface of a substrate made from stainless steel, chosen from stainless steels presenting an aluminium content of more than 0.5% by weight. Formation of the selective coating includes a surface treatment step of the substrate, by polishing, and a heat treatment step of the substrate, in an oxidizing atmosphere, in a temperature range included between 550° C. and 650° C. The heat treatment in particular enables at least one intrinsically selective superficial thin layer to be formed on the outer surface of the substrate.

Abstract: A solar absorber for a concentrated solar power (CSP) system includes a cylindrically shaped blackbody cavity receiver fused to a cylindrically shaped heat exchanger shell covering the receiver to form a monolithic cavity receiver and heat exchanger. An exterior surface of the cavity receiver has grooves embedded to create a duct spiraling about the exterior of the cavity receiver so that the duct forms tubes of a tube-style heat exchanger when covered by the heat exchanger shell. An interior diameter of the cavity receiver is greater than or equal to a diameter of an aperture of the cavity receiver, and a longitudinal interior depth of the cavity is greater than or equal to twice the interior diameter of the cavity receiver. The monolithic solar absorber is preferably composed of a ceramic material such as silicon carbide having emissivity greater than 0.9.

Abstract: The solar panel includes a housing for a heat collecting element, delimited by walls, one of which includes slits for the passage of solar rays. At least one reflective area is arranged to face the heat collecting element. At least one reflective strip is arranged outside the housing to face a respective slit so as to focus the solar rays received towards this slit. Elongated reflective elements are arranged side by side, and include coplanar flat bases, forming together the wall of the housing having slits and the flat base of at least one elongated reflective element forming a reflective area of this wall of the housing, and including one concave surface arranged to face the reflective strips such that the solar rays reflected by each concave surface are focused towards the corresponding reflective strip.

Abstract: Solar energy receivers and methods of using the same are provided. The receiver includes a plurality of absorber members configured to absorb concentrated solar radiation. The plurality of absorber members define at least one fluid transport channel. The solar receiver also includes a plurality of structural plates, wherein each of the plurality of structural plates is positioned between adjacent absorber members to define an inner fluid transport passage and a plurality of outer fluid transport passages. The inner fluid transport passage is in flow communication with the plurality of outer fluid transport passages. The plurality of outer fluid transport passages are in thermal communication with the plurality of absorber members.

Abstract: A method (100) for manufacturing a thermal absorber for a solar thermal collector includes arranging (120) a substrate of the thermal absorber on a vacuum coating line and depositing (160) by way of a physical vapour deposition on the substrate that is arranged on the vacuum coating line layers configured to absorb light.

Abstract: An electromagnetic radiation collection apparatus includes an exterior including a bottom portion and first and second walls extending from the bottom portion, the exterior defining a cavity in the bottom portion, the cavity being configured to receive a thermally absorbing material; and a radiation collector. The radiation collector includes a first surface on an interior of the first wall, the first surface being at least partially reflective and positioned to reflect radiation that is incident on the first surface into the cavity; and a second surface on an interior of the second wall, the second surface being at least partially reflective and positioned to reflect radiation that is incident on the second surface into the cavity, where the first and second surfaces face each other to at least partially define an interior region of the radiation collector, and the cavity defines an opening to the interior of the radiation collector.

Abstract: Inventive concentrated solar power systems using solar receivers, and related devices and methods, are generally described.

Abstract: A system for heating a fluid conveyed or contained in a pipe or other process equipment by solar energy is disclosed. The system includes passive and active control methods to control the temperature of the fluid within a selected temperature range. The passive methods use the natural properties of selected materials for the system and the geometry and the orientation of the materials to control the temperature range. The active methods uses one or more than one control mechanism for changing the ratio of energy gain and heat loss at any point in time during a day and between days and across seasons, with these mechanisms including mechanisms to control energy transfer in and heat transfer out of the fluid.

Abstract: The radiation-selective absorber coating for absorber tubes of parabolic trough collectors includes two or more barrier layers (24a, 24b); an infrared reflective layer (21) on the barrier layers (24a, 24b); at least one cermet absorption layer (22) above the infrared reflective layer (21) and an antireflection layer (23) above the at least one cermet absorption layer (22). The two or more barrier layers (24a, 24b) include a first barrier layer (24a) of thermally produced oxide and a second barrier layer (24b) arranged above it. The second barrier layer (24b) is a cermet material including at least one oxide compound and at least one metal. The oxide compound is aluminium oxide, silicon oxide, nickel oxide and/or chromium oxide. The metal is molybdenum, nickel, tungsten and/or vanadium. The invention also includes an absorber tube with the absorber coating on it.

Abstract: A solar receiver (100) having a radiation capturing element (3) about which is formed a channel (8) through which a working fluid flows such that thermal energy of the radiation capturing element (8) is absorbed by the working fluid, the channel (8) being shaped to provide a uniform cross sectional area along a length thereof between an inlet thereto and an outlet therefrom.

Abstract: A solar energy collection system includes a reflector configured to reflect and focus a majority of solar energy from visible light and infrared spectra. The solar energy collection system also includes a light trap configured to receive concentrated solar energy from the reflector. The light trap includes a black body that is configured to absorb a majority of the concentrated visible light and infrared energy and convert the absorbed energy into thermal energy.

Abstract: A solar absorber for a concentrated solar power (CSP) dish system includes a cylindrically shaped blackbody cavity receiver fused to a cylindrically shaped heat exchanger shell covering the receiver to form a monolithic cavity receiver and heat exchanger. An exterior surface of the cavity receiver has grooves embedded to create a duct spiraling about the exterior of the cavity receiver so that the duct forms tubes of a tube-style heat exchanger when covered by the heat exchanger shell. An interior diameter of the cavity receiver is greater than or equal to a diameter of an aperture of the cavity receiver, and a longitudinal interior depth of the cavity is greater than or equal to twice the interior diameter of the cavity receiver. The monolithic solar absorber is preferably composed of a ceramic material such as silicon carbide having emissivity greater than 0.9.

Abstract: A heat collection receiver includes a heat absorption body and a support body. The heat absorption body includes at least one honeycomb unit in which a plurality of flow paths through which a heat medium passes are provided in parallel with each other. The at least one honeycomb unit includes porous silicon carbide and silicon that fills pores in the porous silicon carbide. A surface region of the at least one honeycomb unit includes a porous layer which includes pores in a predetermined depth from the surface. The surface region is irradiated with solar light. The pores of the porous layer are not filled with the silicon. The support body accommodates and supports the heat absorption body and the heat medium flows through the support body.

Abstract: A thermal receiver includes a heat absorption body and a support body. The heat absorption body includes at least one honeycomb unit having a plurality of flow paths arranged for circulation of a heat medium. The heat absorption body includes silicon carbide. A surface of the at least one honeycomb unit to which solar light is radiated is subjected to a roughening treatment or a coating treatment. The support body accommodates and supports the heat absorption body and allows circulation of the heat medium.

Abstract: A thermal collector tube includes a main body portion that houses a heat medium, and a coating layer provided on an outside surface of the main body portion. The coating layer has a radiation rate of 0.70 to 0.98 at room temperature and at a wavelength of 1 ?m to 15 ?m. The thermal collector tube is used in concentrated solar power generation in which solar light is collected using reflecting mirrors, the collected solar light is converted into heat using a thermal collector having the thermal collector tube, and power is generated using the heat.

Abstract: A thermal receiver includes a heat absorption body and a support body. The heat absorption body is made of at least one honeycomb unit having a plurality of flow paths arranged for circulation of a heat medium. The support body supports the heat absorption body and allows circulation of the heat medium. The heat absorption body includes silicon carbide and is supported at a position away from an inner surface of the support body by a predetermined distance.

Abstract: A solar energy absorptive coating for absorbing sunlight energy is provided. The coating includes a multilayer stack including, a first absorbing layer with first absorbing layer material for absorbing an absorption radiation of a certain spectrum of the sunlight, a transmission dielectric layer with a transmission dielectric layer material for a transmission of the absorption radiation, and a second absorbing layer with a second absorbing layer material for absorbing the absorption radiation, wherein at least one of the absorbing layer materials has an absorbing layer material refractive index for the absorption radiation, between 1.5 and 4.0, and an absorbing layer material extinction coefficient for the absorption radiation, between 0.8 and 3.0, and the transmission dielectric layer material has a dielectric layer material refractive index for the absorption radiation, between 1.0 and 3.0, and a dielectric layer material extinction coefficient for the absorption radiation, between 0.0 and 0.2.

Abstract: The invention concerns a solar collector board formed as a layered construction. The board comprises at least a first and a second platelike body being congruent or close to congruent, and arranged mutually parallel or close to parallel with a mutual distance, the first platelike body being, at its surface facing the second platelike body, provided with absorbing properties, and the second platelike body being transparent or opaque and made of at least one low emission material, and wherein a seal is arranged in between the first and the second platelike body at their respective side edges to assure said mutual distance and at the same time to provide a fluid tight space between the first and the second platelike body, the space between the first and the second platelike body being adapted for circulation of a fluid, and the layered construction being further provided with at least one inlet and at least one outlet for the circulating fluid.

Abstract: The invention relates to a method for producing a selectively absorbing coating on a solar absorber component comprising the steps of: Providing a substrate having a metallic surface, Determining the inner surface of the metallic surface, Determining the charge quantity per unit area required for producing the absorbing coating according to the inner surface, Electrolytically producing the absorbing coating by direct-current anodising the metallic surface of the substrate, forming a porous oxide layer, and then alternating-current pigmenting the pores of the oxide layer; until the charge quantity per unit area determined for the respective step from the inner surface is reached, wherein the ratio between the charge quantity per unit area for the direct-current anodising and the charge quantity per unit area for the alternating-current pigmenting is 0.65 to 0.8. In addition, the invention relates to a solar absorber component produced according to this method.

Abstract: A heat receiver tube for absorbing solar energy and for transferring the absorbed solar energy to a heat transfer fluid is provided. The heat receiver tube includes a first partial surface, which is covered by a solar energy absorptive coating, and a second partial surface, which is substantially uncovered by the absorbing coating. Also provided is a parabolic trough collector with a parabolic mirror having a sunlight reflecting surface for concentrating sunlight in a focal line of the parabolic minor and a heat receiver tube which is arranged in the focal line of the parabolic mirror, wherein the heat receiver tube is arranged in the focal line such that the first partial surface with the solar absorptive coating is at least partially located opposite to the sunlight reflecting surface and the second partial surface at least partially averted to the sunlight reflecting surface.

Abstract: A solar collector for heating and transferring fluids, having an inlet manifold and an outlet manifold through which fluid is respectively transferred into and out of the solar collector; and a plurality of polymer tubes each connected between the inlet and outlet manifolds, the polymer tubes having co-extruded concentric inner and outer tube layers, wherein the outer tube layer is composed of a harder polymer than the inner tube layer.

Abstract: Various embodiments provide an absorber tube that comprises an inner tube having an exterior surface, at least a portion of which contains a plurality of coating layers. The absorber tube also includes an outer tube spaced apart from the inner tube so as to define a cavity between the two. At least one of the coating layers may be configured to substantially impede migration of gaseous particles from the interior surface and into said cavity. At least one of the coating layers may be a reflective copper coating that is adhered to the exterior surface via an electrical charging process. An absorber tube comprising a connecting member between central and end portions of the tube is also provided. The central portion may be formed from carbon steel, while remaining portions are formed from stainless steel. Coating layers may be likewise adhered to only the central portion.

Abstract: A solar power tower solar receiver absorber including: an enclosure; at least one panel configured to be illuminated by solar flux; a core made of at least one material with heat conductivity at least partially encompassed by the enclosure; and a plurality of tubes passing through the core and extending substantially in a parallel direction with respect to the panel configured to be illuminated. The tube is configured for circulation of a fluid to be heated, for example a gas for operating a gas turbine.

Abstract: A solar collector apparatus with Dewar-type evacuated tubes results in the more efficient collection of solar radiation by, for example, maintaining the level of a volatile liquid flowing into the solar collector so that no more than 80% of the volume of an inner cylinder of a collection tube is filled with liquid and a corresponding manifold collects the vapor produced when heat is transferred from the surface of the inner glass cylinder that absorbs solar radiation to the volatile liquid. The aforementioned apparatus may likewise be used to heat a liquid within an absorber tube, the liquid having a volatile and a non-volatile component. As heat is transferred to the liquid, a fraction of the volatile component is converted to vapor, leaving the liquid more concentrated in the non-volatile component.

Abstract: A method for providing a thermal absorber, which can be used in solar thermal collectors. The method includes a step of depositing on a substrate a first layer having a composition that comprises titanium, aluminium, nitrogen, and one of following elements: silicon, yttrium, cerium, and chromium. The method further optionally includes a step of depositing a second layer deposited on the first layer, the second layer having a composition including titanium, aluminium, nitrogen, oxygen and one of the elements of silicon, yttrium, cerium, and chromium, and a step of depositing a third layer having a composition including titanium, aluminium, silicon, nitrogen, and oxygen, the third layer being a top layer of the thermal absorber.

Abstract: The solar panel includes a housing for a heat collecting element, delimited by walls, one of which includes slits for the passage of solar rays. At least one reflective area is arranged to face the heat collecting element. At least one reflective strip is arranged outside the housing to face a respective slit so as to focus the solar rays received towards this slit. Elongated reflective elements are arranged side by side, and include coplanar flat bases, forming together the wall of the housing having slits and the flat base of at least one elongated reflective element forming a reflective area of this wall of the housing, and including one concave surface arranged to face the reflective strips such that the solar rays reflected by each concave surface are focused towards the corresponding reflective strip.

Abstract: A solar thermal collector includes a receptacle and a fluid conduit. The receptacle is evacuated to a subatmospheric pressure. The receptacle includes a window and a reflector facing the window. The window and the reflector are exposed to the subatmospheric pressure in the receptacle. The fluid conduit extends through the receptacle between the window and the reflector. The reflector concentrates solar radiation passing through the window onto the fluid conduit.

Abstract: This invention relates to a fluid heating system, wherein the fluid is capable of being heated by means of solar energy, the fluid heating system including: an outer housing; an inner housing contained within the outer housing and including an absorbent material core located within the inner housing to define a flow passage between it and the walls of the inner housing; the absorbent material core being suitable for absorbing solar energy transmitted through the outer and inner housings; and wherein the outer housing; inner housing; and the absorbent material core are arranged such that solar energy is transferred through the fluid in the flow passage before being absorbed by the absorbent material core.