GB2501713A

GB2501713A - Solar heat exchanger utilising graphene foam

Info

Publication number: GB2501713A
Application number: GB1207607.1A
Authority: GB
Inventors: Gideon Sta Wan Kukard; Maria Fernanda Kukard
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-05-01
Filing date: 2012-05-01
Publication date: 2013-11-06
Also published as: GB201207607D0; WO2013164557A3; WO2013164557A2

Abstract

A solar heat exchanger comprises a fused quartz glass tube containing a graphene foam 5 and water 4, where the water, which is to be heated by solar energy, is in direct contact with the graphene foam. In operation, the graphene foam is designed to absorb energy from incident sunlight, heat up, and transfer the heat into the surrounding water. Preferably, the glass tube comprises an inner tube 2 and an outer tube 1, with a vacuum 3 maintained in the space between the inner and outer tubes so as to minimise heat losses and maximise heat absorption. A further graphene coating 6 may be included on the inside surface of the inner tube. Water may be pumped through the inner tube of the heat exchanger and around the graphene foam. The graphene foam may include a metal substrate, which can either be melted out to leave the graphene foam as the only structure or left in place to make the foam a darker colour for improved solar heat absorption. Preferably, the graphene foam comprises a rolled up sheet or stacked layers of graphene. A Fresnel lens (7, fig.2) may be used to concentrate solar energy onto the heat exchanger.

Description

I

SOLAR GLASS HEAT EXCHANGER

BACKGROUND OF THE INVENTION

It is very hard to efficiently extract the energy within a sunbeam and transfer that energy into another medium. The materials used so far have really low efficiency due to low absorption which limits the amount of heat getting onto the heat exchanger or thermal conductivity which limits the speed that the absorbed heat can transferred at, into another medium, like water. Normally solar heat exchangers are made from darkened glass or darkened metals. The medium used poses a considerable barrier to the overall efficiency regardless of any, more efficient coatings that can be added to either side of the glass or metal, as the medium with the lowest thermal efficiency determines the overall efficiency of the heat exchanger as it limits the speed of heat transfer.

DESCRIPTION OF PRIOR ART

There are many solar heat exchangers that extract heat from sun beams (Patent Application Publication US 2011/0253128) which uses the sun's beams using multiple mirrors and reflects them into a centre receiving plate and (Patent Application Publication US 2010/0314081) which uses a graphite in the heat exchanger.

The present invention uses a Fresnel lens to concentrate the solar beams onto the heat exchanger, concentrating the suns beams raises the temperature from ambient to several hundred degrees centigrade or even >1000. The concentrated sunlight goes through two tubes of clear fused quarts glass onto a graphene foam sheet. This foam structure is made by coating a single layer of graphene onto a metal foam made from copper or nickel, using Chemical Vapor Deposition (CVD). The metallic foam base can then be melted out at high temperatures to leave just the graphene layer in place forming a foam structure. The graphene has a very high thermal conductivity and directly contacts the sunlight and the water, making the overall efficiency of the heat exchanger very high. Graphene is also dark allowing it to absorb more sunlight and therefore heat. There is a vacuum maintained between the inner and outer tube, to trap any heat and force it into the water, and the inner tube also has a single graphene layer coated on the inside again using (CVD). This is done to transfer any heat from the inner glass tube into the water.

The vacuum is maintained by sealing the ends of the outer tube onto the inner tube. Water is pumped through the inner tube of the heat exchanger and around the graphene foam, to transfer the absorbed heat from the graphene into the water. Pumping the water through the heat exchanger also prevents overheating/steam and makes it possible to heat large volumes of water fast. De-aerated water is used to allow the water be heated to very high temperatures without it boiling or forming steam. The Fresnel lens and solar heat exchanger can be fitted onto a heliostat to track the sun and keep the lenses' focal point on graphene foam. The speed that the water is being pumped through the heat exchanger can be varied to create the desired temperature rise.

BRIEF DESCRIPTION OF THE DRAWING

Fig 1 -Front view of solar glass heat exchanger Fig 2 -Fresnel lens focussing sunlight on solar heat exchanger (fig 1) Fig 3 -shows and side view of the heat exchanger with multi layers of graphene foam, stacked back to back.

Fig 4 -shows a alternative version, where the graphene foam is rolled up, to form multi layers Fig 5-shows the solar heat exchanger integrated into a standard central heating and hot water system Fig 6 -shows the solar heat exchanger integrated into a hot water system Fig 7 -Show the sunlight entering the heat exchanger and how heat is absorbed and transferred into the water.

DESCRIPTION

Fig 1 -shows inside the solar heat exchanger. (1) outside tube of clear fused quarts glass sealed onto the inner tube to maintain vacuum, (2) Inside tube of clear fused quarts glass in oval or round shape, (3) vacuum between two layers of glass, (4) de-aerated water being pumped through heat exchanger, (5) graphene foam which is multi layered or rolled up to form multi layers (6) graphene layer coated on the inside of inside tube (2).

Fig 2-shows a (7) Fresnel lens, focussing the sunlight onto the (5) multi layeied graphene foam inside the heat exchanger while passing through (1) outside tube of fused quartz glass tube, (3) the vacuum and through the (6) inside tube of fused quartz glass. The graphene foam will heat up and transfer heat to (4) water being pumped through heat exchanger by direct contact.

Fig 3-shows a side view of the heat exchanger with multi layers of(S) graphene foam, stacked back to back. Where (1) outer clear fused quarts layer (2) oval shaped inner clear fused quarts tube, (4) de-aerated water being pumped through heat exchanger, (6) graphene coating on inside of inner tube, (3) vacuum between inner and outer tubes Fig 4-(1) outer fused quarts tube, (2) inner tube of fused quarts in oval shape, (3) vacuum, (4) water being pumped through heat exchanger, (6) graphene coating on inside of inner fused quarts tube, (5) rolled up graphene foam sheet.

Fig 5-(8) solar glass heat exchanger as in figure 1(7) Fresnel lens focussing sunlight on (8) solar heat exchanger (10) metal plate heat exchanger to separate solar circuit (9) and boiler circuits (15 and 16) and to facilitate heat transfer between them, (18) pump for circulating water through the (9) solar circuit, (11) gas or oil boiler, (12) expansion vessel, (16) central heating circuit moving heated water to radiators for heating, (15) heated water being pumped through the (17) cylinder coil to produce domestic hot water,(14) motorized valve or valves diverting water between central heating and domestic hot water circuits, (9) pumped solar water circuit with de-aerated water, (19) Radiator on central heating circuit radiating heat. When the solar heat exchanger (8) is being used to heat the water of the circuits (15 and 16), the boiler will be off and when there is no sunlight available, the boiler (11) will heat the water on the circuit, because the solar heat exchanger (8) and solar circuit (9) will not being in use.

Fig 6-(8) solar heat exchanger as in figure 1, (9) pumped solar heating circuit with de-aerated water, (20) hot water cylinder with internal coils, (21) internal coil connected to gas or oil boiler, (22) backup electrical immersion heater, (23) cold water feed into cylinder, (24) coil connected to solar heat exchanger in cylinder used to produce domestic hot water while sun is shinning, (7) Fresnel lens, (25) hot water draw off to hot water taps. This lay out will allow the cylinder to produce hot water in any conditions with the possibility of getting all or most of the heat of the sun.

Fig 7-In this figure, Sunlight enters from the top of the heat exchanger, through (1) outer layer of fused quartz glass which will absorb minimal amounts of heat as it is clear glass and the focal point of the Fresnel lens is on the graphene foam(s). The light then passes through the (3) vacuum and the (2) inner tube of fused quartz glass which is also clear, but will absorb more heat than (1) because it is closer to the focal point. The heat that it does absorb, will be distributed into the water by (6) graphene coating on the inside of the tube, as it cannot go the other way being blocked by the (3) vacuum. The sunlight continues down and hits the (5) dark graphene foam, where most of the heat is absorbed this can be multi layers of graphene foam stacked back to back, or a large sheet of graphene foam rolled up. The heat is then distributed through the length of the graphene foam, because of the very high thermal conductivity of the graphene into the de-aerated water, by direct contact. The water is being pumped passed the graphene foam to keep it from overheating and forming steam. This also assists in heating large volumes of water.

Claims

Claims -The heat exchanger is made from high temperature fused quartz glass -The heat exchanger incorporates, the most efficient method of transfer of sunbeams energy into water, as the graphene directly absorbs the sunlight's heat and transfers it into water by direct contact.-Maintaining a vacuum between inner and outer tubes minimises heat loss and maximises heat absorption.-The graphene foam can have the metal substrate, melted out to leave the graphene foam as the only structure, or left in place, to make foam colour darker for better sunlight! heat absorption.-The Frcsnel lens and the heat exchanger can be incorporated onto a heliostat to keep the focal point on the graphene foam to maximise heat recovery and performance.-The focal point of the Fresnel lens can be changed by varying the distance between the Fresnel lens and the heat exchanger, which will alter the temperature rise in the water.-The speed of the water passing through the heat exchanger can be varied to get the desirable temperature rise.-The Fresnel lens can be omitted, if a slower rate of heat absorption is required.-The shape or diameter of the tubes is not significant, as it can be varied from application to application.-The water does not have to be dc-aerated as in lower temperatures, it does not mater.-If the flow of water through the heat exchanger is slow down enough or stopped altogether, steam can be created and used.-The heat exchanger can be of any size.-The heat exchanger can be put in series or parallel to other similar heat exchangers.-The graphene foam can be a rolled up sheet or stacked layers of graphene -The graphene foam's substrate metal can be left in place to obtain a darker colour to aid in the absorption of light/heat.-This heat exchanger can be used to heat other liquids -This heat exchanger can be used to heat air, passing through it -This heat exchanger can be used to absorb radiant heat created by combustion of flammable gasses in air.-This heat exchanger can be used to absorb radiant heat from any flame as a result of combustion. p 4Amendments to the claims have been filed as follows: Claims I-A solar heat exchanger comprising a fused quartz glass tube containing a graphene foam, where the tube also contains water to be heated by solar energy that is in direct contact with the graphene foam.

2-The heat exchanger according to claim I, is made from high temperature fused quartz glass, which incorporates, the most efficient method of transfer of sunbeams energy into water, as the graphene directly absorbs the sunlight's hcat and transfers it into water by direct contact, while maintaining a vacuum between inner and outer tubes minimises heat loss and maximises heat absorption.

3-The heat exchanger according to claim 1, can be used to heat other liquids; it can also be used to heat air, passing through it or can be used to absorb radiant heat created by combustion of flammable gasses in air, it can also absorb radiant heat from any flame as a result of combustion.

4-The graphene foam can have the metal substrate, melted out to leave the graphene foam as the only structure, or left in place, to make foam colour darker for better sunlight! heat absorption.

5-The graphene foam can have the metal substrate, melted out to leave the graphene foam as the * : *.: only structure, or lcft in place, to make foam colour darker for better sunlight! heat absorption, the *:" * graphene foam can be a rolled up sheet or stacked Layers of graphene.* 6-The heat exchanger according to claim 1, can be of any size, and can bc put in series or parallel :.: . to other similar heat exchangers. * . * .** * * *