WO2016062804A2

WO2016062804A2 - Method and apparatus form operating a solar furnace 24 hours a day

Info

Publication number: WO2016062804A2
Application number: PCT/EP2015/074470
Authority: WO
Inventors: Brian Howard
Original assignee: Darkenergy Limited
Priority date: 2014-10-22
Filing date: 2015-10-22
Publication date: 2016-04-28
Also published as: GB2531569A; GB201418812D0; WO2016062804A3

Abstract

A method of operating a solar furnace 24-hours a day is provided. The method involves providing a solar furnace having a heatable pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy. The solar furnace is operated during periods of daylight so that the pressure vessel is heated by solar energy and using the energy imparted on the heat transfer medium to drive the electrolysis of water to form hydrogen gas and oxygen gas. The solar furnace can also be operated during periods of low light or darkness so that the pressure vessel is at least partially heated by thermal energy produced by burning the hydrogen gas produced during the daylight operation of the solar furnace.

Description

METHOD AND APPARATUS FOR OPERATING A SOLAR FURNACE

24 HOURS A DAY

Field of the Invention

The present invention relates to solar furnace and more specifically a solar furnace that is capable of operating during periods of bad weather, low light or even darkness.

Background of the Invention

Solar furnaces offer a promising source of renewable energy that can be deployed in regions that may have limited natural resources, whether in the form of fossil fuels or geographical phenomena (e.g. wind), that might otherwise be used to generate electricity.

Solar furnaces make use of the Sun's energy (i.e. solar energy) to raise the temperature of a heat transfer medium. This energised heat transfer medium can then be used to generate electricity or put to other work, such as, for example, air conditioning, pasteurisation or desalination.

International PCT application publication number WO2010/073022, which is an earlier application made by the authors of this document, describes a solar furnace that uses solar energy to raise the temperature of a pressure vessel within the solar furnace. The pressure vessel is provided with a convoluted internal pathway in the form of a substantially helical pathway or spiral. When heat transfer medium, which is introduced into the pressure vessel at a temperature just below its boiling point, comes into contact with the interior walls of the heated pressure vessel it instantly atomises. This causes the heat transfer medium to flash and gain kinetic energy and move forward at greater speed.

This process continues along the convoluted internal pathway of the pressure vessel until the energised heat transfer medium exits the pressure vessel and is put to work (e.g. driving a steam turbine to generate electricity). Although the solar furnace described in WO2010/073022 provides an effective and viable source of renewable energy it is appreciated that further development of the design will further enhance the utility of the solar furnace.

Summary of the Invention The present invention improves on the solar furnaces of the prior art by providing a method of operating a solar furnace 24-hours a day. The method comprising: providing a solar furnace having a heatable pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; operating the solar furnace during periods of daylight so that the pressure vessel is heated by solar energy and using the energy imparted on the heat transfer medium to drive the electrolysis of water to form hydrogen gas and oxygen gas; operating the solar furnace during periods of low light or darkness so that the pressure vessel is at least partially heated by thermal energy produced by burning the hydrogen gas produced during the daylight operation of the solar furnace.

By providing a secondary means of heating the pressure vessel it is possible to supplement and even replace the heating effect of the Sun. In this way the solar furnace can be operated without interruption through periods of low light (e.g. bad weather) and even at night.

One of the key aspects of the improved solar furnace of the present invention is that it is completely self-contained and utilises the energy harvested from solar energy during periods of daylight to form the hydrogen gas that is subsequently used in periods of low light to power the secondary pressure vessel heating means. As a result the solar furnace of the present invention can be operated in remote locations away from other fuel sources. It is envisioned that the amount of energy generated during the normal daylight operation of the solar furnace is sufficient to drive the electrolysis of water whilst at the same time serving other energy requests.

Preferably the heat transfer medium that leaves the pressure vessel with increased kinetic energy may be used to drive an electricity generator. Further preferably the electricity generated by the generator may be used to power the electrolysis of the water.

Preferably the method may further comprise the provision of an atmospheric water generator (AWG) to capture the water used in the formation of the hydrogen and oxygen gases.

The provision of an AWG to capture water from the ambient air found around the solar furnace serves to further enhance its self-contained capabilities. It will be appreciated that in locations where running water is not readily available the use of an AWG to capture water moisture from the air would ensure that the production of hydrogen gas can continue. It is envisioned that the AWG may be powered by electricity generated by the generator.

However, it is appreciated that in locations where an alternative source of water is readily available the use of an AWG might not be essential.

Preferably the thermal energy produced by burning hydrogen may be imparted on the pressure vessel via a burner wand located within the pressure vessel.

Preferably the method may further comprise monitoring the levels of solar energy being collected by the solar furnace and, if necessary, supplementing the heating of the pressure vessel by burning hydrogen.

In this way the transition between heat sources used to heat the pressure vessel can be smooth thus ensuring that the temperature of the pressure vessel remains substantially constant through changes in the daylight levels.

Preferably the method may further comprise storing the hydrogen gas produced by the electrolysis of water until such time as it is required. Storing the hydrogen gas locally again ensures that the transition between heat sources is smooth and instantly available. It is appreciated that the storage capacity has a direct bearing on how long the solar furnace can operate during a period of low light or darkness.

Preferably the method may further comprise routing exhaust gases, generated by burning hydrogen, past a heat transfer medium storage tank, which supplies the vessel inlet, so that at least some of the thermal energy in the exhaust gases can be imparted to the heat transfer medium within the storage tank. Using the thermal energy within the exhaust gases given off from burning hydrogen to heat the heat transfer medium before it is introduced into the pressure vessel reduces the level of supplementary heating needed and thus the energy required to ensure the heat transfer medium is provided at the required temperature. In this way the energy efficiency of the solar furnace is enhanced.

The present invention also provides apparatus for use in accordance with the above described method. To this end the present invention provides a solar furnace capable of being operated 24-hours a day, said furnace comprising: a heatable pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; a lens array positioned to capture and direct solar energy on to the pressure vessel so as to heat said pressure vessel; electrolysis means for decomposing water to form hydrogen gas and oxygen gas, whereby, in use, the energy to drive the electrolysis means is obtained from the heat transfer medium leaving the pressure vessel; and pressure vessel heating means that generate heat by burning the hydrogen gas formed by the electrolysis of water.

Preferably the solar furnace may further comprise an electricity generator that is configured to use the heat transfer medium leaving the pressure vessel to generate electricity. Further preferably the electrolysis means may be powered by the electricity generated from the heat transfer medium.

Preferably the solar furnace may further comprise an atmospheric water generator that, in use, captures water from the environment and supplies it to the electrolysis means. In this way the solar furnace can be operated in areas where water sources such as rivers, lakes and seawater are not readily available.

Preferably the pressure vessel heating means may comprise a hydrogen burner wand located within the pressure vessel. In this way the thermal heat produced by burning the hydrogen gas can radiate outwards from the core of the pressure vessel along the length of the pressure vessel, thereby ensuring a consistent heating effect. Preferably the solar furnace may further comprise control means that monitor the levels of solar energy being collected by the lens array and operate the pressure vessel heating means appropriately to maintain the pressure vessel at a predetermined operational temperature.

Preferably the solar furnace may further comprise a storage tank to house the hydrogen gas produced by the electrolysis means until such time as the hydrogen is required by the pressure vessel heating means.

Further preferably the hydrogen storage tank may comprise a stainless steel shell with a polymer lining-Lining the storage tank with a polymer, such as polycarbonate, gives corrosion resistance against hydrogen embrittlement and provides a permeation barrier. It is envisioned that a storage tank may also be provided to house the oxygen gas produced by the electrolysis means. Such oxygen could then be used when burning the hydrogen. However it is appreciated that the use of stored oxygen is not crucial and the hydrogen could be burnt in air taken from the environment without departing from the central aspect of the present invention. Preferably the solar furnace may further comprise a heat transfer medium storage tank. Said tank preferably has one or more polycarbonate mesh mats provided on the outer surface thereof to control the electromagnetic radiation (EMR) reflection and absorption characteristics of the tank. The polycarbonate, which absorbs the EMR, covers 40% of the surface area of the tank. The remaining 60% of the tank's reflective surface is not covered by polycarbonate. In this way the mesh lets 60% of the light reflect and absorbs 40% into the medium tank.

In this way the heat transfer medium storage tank can utilise some of the solar energy incident on it to heat the heat transfer medium stored therein and reflect the rest of the solar energy back onto the pressure vessel. As will be appreciated from the detailed description of a preferred embodiment of the present invention, the positioning of the heat transfer medium storage tank relative to the pressure vessel facilitates this arrangement.

Preferably the pressure vessel heating means may further comprise an exhaust conduit that directs the exhaust gases past the heat transfer medium storage tank before the gases are expelled from the solar furnace. In this way thermal energy present in the exhaust gases produced by burning hydrogen is not wasted but rather put to work in preheating the heat transfer medium before it is introduced into the pressure vessel. This reduces the energy required from other sources (e.g. electricity generated by solar furnace) to preheat the heat transfer medium, thereby increasing the power output of the solar furnace. Preferably the solar furnace may be housed within a standard shipping container, said shipping container being configured to completely enclose the solar furnace and provide means to allow solar energy to reach the lens array.

It is envisioned that by providing the solar furnace within a standard shipping container the solar furnace can be readily transported to where it is required. By ensuring that the solar furnace can be completely housed within the shipping container the chances of the solar furnace being damaged during transit are reduced. This also enables multiple shipping containers to be stacked in the normal manner.

Further preferably said means may to comprise an opening in the top of the container that is configured to provide unobstructed access to the lens array. In this way the container does not prevent solar energy reaching the lens array. It is also envisioned that in an alternative arrangement the top of the container itself may form the lens array.

Advantageously the solar furnace may further comprise adjustable support members that can be operated to adjust the height of the lens array relative to the opening in the top of the container. In this way the lens array be housed within the container during transit - thereby protecting the lens from damage - and then raised through the opening during the operation of the solar furnace - such that the lens array has the maximum exposure to solar energy. Preferably the container may also house one or more storage tanks selected from the group consisting of: water storage tank, hydrogen storage tank, oxygen storage tank, heat transfer medium tank.

In addition to the above identified method and apparatus the present invention also provides a solar furnace array comprising multiple solar furnace units. It will be appreciated that combining multiple solar furnace units will increase the power generated from solar energy at a given site. To this end the present invention provides a solar furnace array comprising a plurality of solar furnaces stacked on top of one another, wherein each solar furnace comprises a lens array and a pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; wherein the solar furnaces in the stack are oriented so that the lens array of each solar furnace is directed towards the lens array of an adjacent solar furnace to form lens pairings and the solar furnace on the top of the stack is oriented skywards; and said array further comprising solar energy collectors positioned on the exterior of the array and one or more light conduits that direct solar energy from the collectors to the lens pairings within the stack.

By stacking multiple solar furnace units one on top of another it is possible to increase the power generated at a given site without increasing to amount floor space required. This allows users with limited floor space to generate higher power outputs by stacking.

Preferably the solar energy collectors may be lens arrays located adjacent the lens array of the solar furnace on top of the stack.

Preferably the solar furnace array is made up of solar furnaces according to the present invention. However it is envisioned that the array may also comprise solar furnaces such as those described previously in WO2010/073022.

Brief Description of the Drawings

The present invention will now be described in more detail with reference to preferred embodiments shown in the drawings, wherein:

Figure 1 shows a semi-transparent side view of a preferred embodiment of the solar furnace of the present invention;

Figure 2 shows a semi-transparent end view of the solar furnace of Figure 1 ;

Figure 3 shows a semi-transparent plan view of the solar furnace of Figure 1 ; Figure 4 shows a semi-transparent perspective view of a preferred embodiment of the water reactor component of the solar furnace of used for the production of Hydrogen gas during operation of the present invention;

Figure 5 shows a semi-transparent side view of the water reactor of Figure 4; Figure 6 shows a semi-transparent plan view of the water reactor of Figure 4;

Figure 7 shows a semi-transparent perspective view of a preferred embodiment of a container-based solar furnace according to the present invention;

Figure 8 is a system diagram of a preferred embodiment of the solar furnace of the present invention; Figure 9 shows a side view of a preferred embodiment of a solar furnace array according to the present invention;

Figure 10 shows a plan view of the solar furnace array of Figure 9.

Detailed Description of the Preferred Embodiments

The present invention provides an improved method and apparatus for use in operating a solar furnace 24 hours a day through periods of daylight, where the solar furnace is heated primarily (if not exclusively) by solar energy from the Sun; periods of low light (e.g. during bad weather), where the solar furnace is heated by a combination of solar energy and the thermal energy provided by burning hydrogen gas within the solar furnace; and periods of complete darkness (i.e. at night), where the solar furnace is heated primarily by thermal energy provided by burning hydrogen.

One of the core principles behind the present invention is the use of solar energy, when it is abundant, to not only to generate power (e.g. electricity) - which is the main product of the solar furnace - but also to store some of the power generated during periods of daylight so that it can be used during periods of low light or darkness. To this end the present invention makes use of hydrogen gas decomposed from water by electrolysis as an energy storage medium.

The solar furnace of the present invention is a development on the solar furnace described previously in the author's International PCT application published as WO2010/073022. In view of this the teachings of WO2010/073022 are incorporated herein by way of reference.

In addition, and so that the present invention will be readily understood, a brief overview of the mechanism by which the solar furnace produces an energised heat transfer medium suitable for use in electricity generation will now be provided.

To this end reference is now made to Figures 1 , 2 and 3 which show a preferred embodiment of the solar furnace of the present invention. The views are semi- transparent so that the various components, which might otherwise be hidden, are visible. It will be appreciated that in order to clearly explain the key features of the preferred embodiment of the present invention certain components that are important to the general running of the solar furnace have been removed from the figures.

One of the key components of solar furnace 1 described both here and in WO2010/073022 is the pressure vessel 2. Preferably the pressure vessel 2 is made from copper, although it is envisioned that other materials (such as grade 316L stainless steel, for example) with suitable thermal and mechanical properties might also be employed without departing from the present invention.

The pressure vessel is effectively a sealed elongate chamber with an inlet 3 and one thereof and an outlet 4 at the other end thereof. Within the pressure vessel 2 is provided a convoluted internal pathway that runs from the inlet 3 to the outlet 4.

Inside the pressure vessel 2 is provided a convoluted pathway 5 running from an inlet 3 at one end of the pressure vessel 2, where a heat transfer medium is introduced, to an outlet 4 at the opposite end of the pressure vessel 2, where the heat transfer medium leaves the pressure vessel 2. The convoluted pathway 5 serves to greatly increase the number of times the heat transfer medium comes into contact with the heated surface of the pressure vessel 2 along its length. This is important because every time the heat transfer medium comes into contact with the heated surface of the pressure vessel it flashes and gains kinetic energy that causes the medium to move along the pressure vessel at a greater speed. It will be appreciated that the greater the level of kinetic energy present when the heat transfer medium reaches the outlet 4 and eventually leaves the pressure vessel 2 the more effectively electricity can be generated by, for example, a turbine/generator 6 located adjacent to the outlet 4. The pressure vessel 2 is located within an evacuated enclosure within the main body of the solar furnace 1 . Locating the pressure vessel within an evacuated enclosure increases the overall efficiency of the heat transfer process.

The convoluted pathway 5 of the pressure vessel 2 is preferably defined by a combination of the walls of the elongate chamber and a central core 7 having a substantially helical cross-section. Another way of describing the central core is that is shaped like an Archimedes screw.

The central core 7 is preferably made from the same material as the rest of the pressure vessel 2. Advantageously the interior of the pressure vessel that defines the convoluted path may be coated with a heat absorbing substance specially formulated to gain and retain heat. The heat-absorbing substance would be a matt black coating, such as heat absorbing paint.

The diameter of helical cross-section is such that the central core 7 comes into contact with internal walls of the pressure vessel 2 at various points along the length thereof. This allows for steam expansion as it heats along its path through the pressure vessel. It is appreciated that although the turns of the helical central core are shown in Figure 1 as being uniformly spaced from one another it is envisioned that the spacing of such turns may vary along the length of the pressure vessel 2.

Situated on top of the solar furnace 1 is a convex top 8 which comprises a lens array (not shown) to enhance the wanted light values and solar energy. The convex top 8 may also incorporate a series of light filters (not shown) to stop light of unwanted frequency being admitted.

The convex top 8 and the lens array are made of optically clear acrylic lens tiles that contain filter elements built into them during their formation. In a preferred arrangement the lens tiles that make up the lens array are held within a matrix of aluminium epoxy coated extrusions, which help maintain the evacuated enclosure in which the pressure vessel 2 is located.

Situated around the pressure vessel 2 is a reflector portion 9 that serves to direct incident solar energy, captured by the convex top 8 and lens array, onto the pressure vessel 2. To this end the reflector portion is positioned along the sides and underside of the pressure vessel. It will be appreciated that in order to prevent direct light from the convex top 8 and lens array being obstructed the reflector portion does not cover the top side of the pressure vessel 2.

The reflector portion 9 ensures that pressure vessel 2 is bombarded with greatly enhanced solar energy and light. To achieve this, the reflector portion of the preferred embodiment is substantially parabolic-shaped so as to direct as much of the incident solar energy onto the surface of the pressure vessel 2.

The solar furnace 1 is provided with a heat transfer medium tank 10, which provides a reservoir of the heat transfer medium for supply to the inlet 3 of the pressure vessel 2. In the preferred embodiment the heat transfer medium tank 10 is integrated with the reflector portion 9 and as such is positioned along the sides and underside of the pressure vessel 2.

Although not shown in the figures it is envisioned that the reflector portion 9 located on the reflecting surface of the heat transfer medium tank 10 (i.e. the surface that faces the pressure vessel 2) comprises one or more polycarbonate mesh mats.

The polycarbonate mesh is configures to control the Electromagnetic radiation (EMR) reflection and absorption characteristics of the tank 10 so that around 60% of the EMR is reflected back onto the pressure vessel and around 40% is absorbed by the tank 10. In this way some of the solar energy can be used to heat the heat transfer medium within the tank 10.

As will be readily understood, it is important that the temperature of the heat transfer medium, and example of which is distilled water, when it enters the pressure vessel at the inlet 3 at just below the boiling point of said medium. It will be appreciated therefore that the use of solar energy to heat the heat transfer medium whilst it is in the tank 10 serves to reduce or even remove the need for energy from other sources needed to pre-heat the heat transfer medium before it enters the pressure vessel 2 at the inlet 3. In order to prevent potentially dangerous pressures building up within the heat transfer medium tank 10 at least one automatic air bleed valve 1 1 is provided to enable the tank to vent when the pressure reaches an undesirable level.

The pre-heating of the heat transfer medium is described in more detail in WO2010/073022, which is incorporated herein by way of reference.

As will be appreciated from Figure 8 (described below) the pre-heating means are typically powered by way of the steam being routed through the preheater pipes. The pre-heaters 35a and 35b are fed directly from the output end of the condenser box 15 to a solar powered lift pump 36 that delivers the medium to the first pre-heater 35a then the second 35b which delivers the warmed medium to the medium tank 10. The pre-heaters 35a and 35b are in direct contact with the external wall of the medium tank 10 with their exposed surface being fully insulated to conserve heat.

As will be described in more detail below the solar furnace 1 of the present invention provides other means for pre-heating the heat transfer medium that further enhance the efficiency of the system.

As will be readily understood the light and solar energy captured by the solar furnace heats the pressure vessel 2 to 100 to 120°C Thus, when the pre-heated heat transfer medium is injected into the convoluted pathway 5 of the pressure vessel 2 by an atomiser ring (not shown), any atomised medium that comes into contact with the heated surfaces of the convoluted pathway will flash to medium steam and in doing so gain kinetic energy.

It is important that the medium within the pressure vessel 2 is not allowed to become too dry as it passes along the convoluted pathway 5 as this would result in a loss of pressure (i.e. kinetic energy). In order to avoid this and keep the medium within the pressure vessel 2 'wet' a number of attemperators (not shown) are strategically positioned along within the pressure vessel along the length of the convoluted path. The attemperators, which are mounted on an attemperator rail 12, preferably take the form of small spray nozzles that automatically spray a fine mist of a heat transfer medium that with a temperature that is cooler than the boiling point of said medium.

This gives moisture to the medium steam that has lost kinetic energy by becoming too dry.

When the heat transfer medium finally reaches the outlet of the pressure vessel is energised with kinetic energy. Typically the medium leaving the pressure vessel will be at a temperature of around 130°C with a pressure of about 12 bar (i.e. approx. 1200kPa). This energised heat transfer medium is then put to work to drive a turbine/electrical generator assembly 13 which is preferably located in the proximity of the pressure vessel outlet 4.

The electricity produced by the turbine/electrical generator 13 is then available to power both external and internal power requirements.

After passing through the turbine 13 the heat transfer medium, which is in the form of steam, is returned by conduits 14 to the heat transfer medium tank 10 by way of a condenser box comprising condenser plates 15. The condenser box cool the medium steam and drop condensate which then returns to the heat transfer medium tank 10 as a liquid.

The solar furnace 1 is provided with pumping means to urge the return of the heat transfer medium back to the heat transfer medium tank 10. The pumping means (not shown) is preferably driven by energy obtained from solar panels, although alternative means for powering the pumps are possible without departing from the present invention.

Once the heat transfer medium is returned to the heat transfer medium tank 10 the cycle begins again with the medium being pre-heated before it is reintroduced into the pressure vessel 2 of the solar furnace 1 .

The above summary provides an overview of the normal daytime operation of the solar furnace during periods when sunlight levels are suitable. However this operation model is impaired and can even be stopped when sunlight levels fall. It is during these low light periods (e.g. bad weather/at night) that the supplementary heating functionality of the present invention step in.

The supplementary heating functions of the solar furnace 1 will now be described with reference to Figures 1 -3. As previously identified the supplementary heating of the pressure vessel is achieved by a hydrogen fuelled heat source.

As will be appreciated from Figure 1 the central core 7 of the pressure vessel 2 is provided a combustion chamber 16. The combustion chamber 16 is positioned coaxially with the elongate chamber of the pressure vessel 2 and extends along the length of the central core 7. Within the combustion chamber 16 is provided a hydrogen burner wand 17. During use the burner wand 17 is supplied with hydrogen to burn in the combustion chamber 16.

The combustion chamber 16 is also supplied with a source of oxygen to facilitate the combustion reaction. It is envisioned that preferably, although not essentially, the oxygen may be the product of the electrolysis process used to produce the hydrogen gas that fuels the burner wand.

The combustion of the hydrogen gas generates thermal energy which radiates/conducts out from the central core 7 to the rest of the pressure vessel 2 and in doing so supplements (or even replaces) the heating effect provided by solar energy during normal operation of the solar furnace 1 . The combustion chamber 16 and the burner wand 17 are supplied with a mixture of hydrogen and oxygen(or air) by automatic mixing valves 33. The automatic mixing valves ensure that the desired heat output is achieved for the pressure vessel 2. The calculation of the mixture takes into account the size of the pressure vessel that is to be heated. The calculation of the required hydrogen/oxygen mix also takes in to account several environmental factors including: geographical location of the solar furnace; altitude; ambient weather conditions.

It is envisioned that an initial calculation of the required hydrogen/oxygen mix would be carried out when the solar furnace is first installed at a location, with the various constant factors, such as altitude and pressure vessel size, being used. However once the solar furnace is operational further fine tuning of the mixture is achieved automatically by internal sensors within the solar furnace. It will be appreciated that in order for the solar furnace of the present invention to be self-contained the hydrogen that is burned by the burner wand is produced by an electrolysis reaction powered by the solar furnace 1 itself.

The electrolysis of water to produce hydrogen gas and oxygen gas is carried out within a water reactor vessel 18. The water reactor vessel 18 will now be described in more detail with reference to Figures 4, 5 and 6.

The water reactor vessel 18, which is essentially an electrolysis device, comprises a sealed vessel 19 that is divided into two chambers 20 and 21 by a dividing wall 22. The dividing wall 22 takes the form of a profiled diaphragm with a series of perforations 22a provided across the lower portion thereof such that the perforations 22a remain below the water line. This positioning of the perforations 22a facilitates the passage of water between the two chambers whilst minimising the passage of the evolved gases (i.e. hydrogen/oxygen) between the chambers 20, 21 .

A first electrode (e.g. a diode) 24 is provided in the first chamber 20, and a second electrode (e.g. an anode) 23 is provided in the neighbouring second chamber 21 . As will be understood by the skilled person during operation of the water reactor the first chamber 20, in which the diode 24 is located, will evolve oxygen gas. At the same time the second chamber 21 , in which the anode 23 is located, will evolve hydrogen gas. So that the evolved gases can be harvested from the water reactor vessel 18 each of the chambers are provided with a gas outlet. Specifically the first chamber 20 is provided with an oxygen gas outlet 26 and the second chamber 21 is provided with a hydrogen gas outlet 25.

As will be appreciated from Figures 1 -3, the solar furnace 1 is preferably provided with an oxygen storage tank 27 and a hydrogen storage tank 28. Preferably, therefore, the oxygen gas outlet 26 is connected via suitable conduits to the oxygen storage tank 27. Similarly the hydrogen gas outlet 25 is connected to the hydrogen storage tank 28 via suitable conduits.

The hydrogen storage tank 28 is preferably constructed from a stainless steel shell (although a carbon fibre shell might alternatively be used) that is polymer lined to give corrosive resistance against hydrogen embrittlement. The polymer (e.g. polycarbonate) also provides a permeation barrier to prevent hydrogen leakage.

Preferably the oxygen storage tank 27 is made of stainless steel and has an inner coating of polycarbonate liner. Both storage tanks 27, 28 are provided with electrically operated valves or inner tank regulators to control the flow of gas.

In the preferred embodiment the electricity required to drive the electrolysis of the water to produce hydrogen/oxygen is supplied by the electrical generator 13, which, as explained above, is driven by the action of energised heat transfer medium from the pressure vessel working a turbine 13.

As will be appreciated from the flow diagram of Figure 7 the conduit that takes the hydrogen gas from the water reactor vessel 18 to the hydrogen storage tank 28 is provided with a branch pipe that splits off from the main conduit at a manifold 37. The branch pipe directs the hydrogen gas to the hydrogen storage tank 28 by way of the condenser box, which comprises condenser plates 15.

The hydrogen in the branch pipe absorbs heat from the exhaust steam medium as it passes the condenser plates 15 and in doing so help convert the exhaust steam back to condensate prior to its return to the heat transfer medium tank 10.

Whilst it is envisioned that the water supply for the water reactor vessel 18 might be provided from an external water source, such as river or lake in the locality of the solar furnace 1 , in the case of the preferred embodiment shown in the figures the water supply is provided by an atmospheric water generator (AWG) 29.

As will be appreciated by the skilled person an atmospheric water generator is essentially an air compressor that converts ambient air into a condensate, which includes water. It will also be appreciated that even in areas without flowing (e.g. rivers) or standing (e.g. lakes) water sources there is always a moisture component in the air. It is this moisture that the AWG 29 collects, filters and supplies to the water reactor vessel 18 as water. Preferably the solar furnace may be provided with a water storage tank (not shown in the figures) to store the excess water produced by the AWG 29 until such time that the water reactor vessel 18 has need of it.

As with the water reactor vessel 18, the AWG 29 is powered by electricity generated by the electrical generator 13. In view of the energy requirements of both the water reactor vessel 18 and the AWG 29 they need to be operated during the periods of daylight when the solar furnace is operating with its primary heat source (i.e. the Sun).

However, having said that, it is envisioned that the 24-hour operation of the solar furnace facilitated by the supplemental heating of the hydrogen burner ensures that a constant supply of electricity is available to power the water reactor vessel 16 and the AWG 29.

In order to ensure that the temperature of the pressure vessel is maintained at a temperature that is within its operational parameters (around 85 - 105°C) the solar furnace is provided with sensors that monitor the weather conditions and the light values (e.g. using densitometers) of the solar energy incident on the solar furnace.

Additionally the pressure vessel 2 is provided with temperature sensors (not shown) that constantly monitor the temperature of the pressure vessel and signal if supplemental heating from the hydrogen burner 17 is required to maintain the operational temperature of the pressure vessel 2.

The exhaust gases produced in the combustion chamber 16 by the hydrogen burner 17 are expelled from the solar furnace 1 via an exhaust conduit 39. The route of the exhaust conduit is configured so that it takes the hot exhaust gases from the combustion chamber 16 into close proximity with the heat transfer medium tank 10. In this way the thermal energy of the exhaust gases are employed to pre-heat the medium within the tank 10 before it enters the pressure vessel 2. This re-use of the exhaust gases from the combustion chamber further enhances the energy efficiency of the solar furnace 1 .

In a further preferred embodiment of the solar furnace 1 of the present invention the key components of the solar furnace 1 are housed within a standard shipping container 30. As will be appreciated from Figure 7, the container 30 is provided with an opening in its top to allow sunlight to shine on to the solar furnace 1 and in particular the convex top/lens array 8.

Additionally, in the arrangement shown in Figure 7, the solar furnace 1 is provided with solar panels 31 that are also exposed to the sunlight and which can provide energy to drive certain components of the solar furnace - such as the pumps 36 (see Fig. 8) used to move the heat transfer medium around the solar furnace 1 .

The container 30 houses not only the pressure vessel 2, but also the water reactor vessel 18 and the atmospheric water generator 29. Additionally there is space within the container 30 to house the oxygen storage tank 27 and the hydrogen storage tank 28.

During operation of the solar furnace 1 preferably the convex top/lens array 8 of the solar furnace 1 projects through the container opening to ensure the maximum exposure to sunlight. However during the transportation and storage of the solar furnace shown in Figure 7 it is desirable that the convex top/lens array 8, which are vulnerable to damage, do not extend outside of the container's walls.

In order to accommodate both the operational positioning of the convex top/lens array 8 of the solar furnace 1 and the transport/storage positioning the solar furnace is provided with adjustable supports 32. The adjustable supports 32 can be either manually or automatically adjusted to raise and lower the solar furnace and the convex top/lens array 8 relative to the container opening.

Additionally it is envisioned that the adjustable supports 32 can be actuated independently of one another to level off the solar furnace in locations where it is deployed on uneven ground. In order to further improve the understanding of the operation of the solar furnace 1 of the present invention a flow diagram of the key operational components is provided in Figure 8.

The flow diagram show the various feed streams within the system. The main circuit shown in Figure 8 is the pathway that the heat transfer medium takes. The heat transfer medium enters the heated pressure vessel 2 as an atomised spray at an inlet 3. As has already been explained the heat transfer medium then travels along the convoluted path 5 of the pressure vessel 2 gathering kinetic energy as it goes.

The energised heat transfer medium exits the pressure vessel 2 as pressurised steam at outlet 4. The steam heat transfer medium then drives the turbine/generator 13 to produce electricity.

Once it leave the turbine 13 the exhaust steam heat transfer medium begins its return path back to the heat transfer medium tank 10. On this return path the steam passes through the condenser box wherein condenser plates 15 convert the steam back in to a condensate. Before the condensate returns to the heat transfer medium tank 10 it passes through one or more pre-heaters 35a, 35b. As already explained these pre-heaters ensure that the temperature of the heat transfer medium is provided to the tank 10 at a temperature that is with the required operational range (i.e. close to the boiling point of the medium). Once the heat transfer medium returns to the tank 10 the cycle begins again.

Turning now to the supplementary heating system, which is also shown in Figure 8, it can be seen that the water reactor vessel 18 produces both a hydrogen output and an oxygen output.

The oxygen output exits the water reactor vessel 18 and is then directed by a priority valve 38a to either the oxygen storage tank 27 or to feed the automatic mixing valve 33 that supplies the combustion chamber 16.

Oxygen stored in tank 27 also feeds the automatic mixing valve 33. A second priority valve 38b controls which oxygen source (i.e. the direct oxygen source or the stored oxygen source) feeds the automatic mixing valve 33. In use the priority valves 38a 38b are operated to ensure that oxygen produced by the water reactor vessel 18 is routed as appropriate depending on the operational needs of the burner 17 in the combustion chamber 16.

The hydrogen output exits the water reactor vessel 18 and is then directed by a priority valve 38c to either the hydrogen storage tank 28 or to feed the automatic mixing valve 33 that supplies the burner 16 in the combustion chamber 17. The hydrogen feed that takes the hydrogen from the water reactor vessel 18 to the tank 28 is provided with a manifold 37. As already described the manifold 37 can redirect the hydrogen via the condenser plates 15 of the condenser box before it gets to the tank 28. Hydrogen stored in tank 28 also feeds the automatic mixing valve. The feed from the tank 28 is directed through priority valve 38c, which operates to ensure that hydrogen can be supplied to the mixing valve 33 either directly from the water reactor vessel 18 or from the hydrogen store as appropriate.

Finally we turn to the combustion chamber 16 wherein the hydrogen is combusted by the burner 17 in oxygen to generate thermal energy to heat the pressure vessel 2. The combustion chamber 16 is provided with an exhaust conduit 39 so that the exhaust gases can be released.

As will be appreciated from Figure 8 the exhaust conduit 39 is routed passed the heat transfer medium tank 10. In this way at least some of the thermal energy present in the exhaust gases can be used to maintain the heating of the tank 10.

In a further aspect of the present invention there is provided a solar furnace array 40 suitable for deployment in areas where ground space is limited or at a premium. The solar furnace array 40 will be described with reference to Figures 9 and 10.

The array 40 shown consists of three individual solar furnace units 1 a, 1 b and 1 c stacked one on top of another. Units 1 a and 1 c are orientated so that their respective convex tops 8a and 8c are facing upwards.

Unit 1 b, which is positioned between units 1 a and 1 c, is orientated such that its convex top 8b faces downwards towards the convex top 8c of unit 1 c.

The skilled person will appreciate that a suitable structural framework can be employed to retain the units in the shown stacked arrangement. The framework has been omitted from the Figures to avoid over-complication.

As will be understood from the figures the convex top 8a of unit 1 a is fully exposed to the sun and therefore operates in the normal way. However in order to facilitate the operation of units 1 b and 1 c it is necessary to funnel solar energy to the convex tops 8b and 8c by way of light tunnels 41 . Each light tunnel 41 extends from the top of the array 40 to a midpoint on the array that is adjacent to the junction between units 1 b and 1 c. An energy amplifier 42 is provided within each light tunnel 41 to help recover any energy loss caused as the solar energy/light travels down the light tunnel. The energy amplifier essentially acts as a magnifier, to magnify the solar energy and focus it down the tunnel.

At the bottom end of each light tunnel (i.e. the end adjacent to the junction between units 1 b and 1 c) reflection means 43 (e.g. a mirror) is provided to redirect the solar energy/light from the light tunnel 31 into a central chamber. The central chamber, which is sealed, is at least partially defined by convex tops 8b and 8c. The solar energy/light redirected into the central chamber by the reflection means 43 passes through a lens 44 that focuses the pathway of the solar energy/light onto the convex tops 8b and 8c and thereby into their respective solar furnace units 1 b and 1 c.

Preferably a sub divider 45 is also positioned within the central chamber to ensure that any solar energy/light on a path that doesn't intersect with either of the convex tops 8b and 8c is redirected on to the convex tops.

At the top end of the light tunnel 41 (i.e. the end that is adjacent to the top of the array 40) is provided a lens array 46. The lens array 46 facilitates the capture of the required solar energy/light that is incident on the top of the furnace array 40. As can be better appreciated from Figure 10 between the convex top 8a and the lens arrays 46 is provided a plurality of photo-voltaic tiles 47. The tiles 47 are used to generate supplementary power for some of the components of the array 40 (e.g. pumps, etc.).

A control panel 48 is provided the lowermost unit 1 c. The units 1 a-1 c are all linked to one another so that they can all be monitored and operated by the control panel 48.

Claims

1 . Method of operating a solar furnace 24-hours a day, said method comprising: providing a solar furnace having a heatable pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; operating the solar furnace during periods of daylight so that the pressure vessel is heated by solar energy and using the energy imparted on the heat transfer medium to drive the electrolysis of water to form hydrogen gas and oxygen gas; operating the solar furnace during periods of low light or darkness so that the pressure vessel is at least partially heated by thermal energy produced by burning the hydrogen gas produced during the daylight operation of the solar furnace.

2. The method of claim 1 , wherein the heat transfer medium that leaves the pressure vessel with increased kinetic energy is used to drive an electricity generator.

3. The method of claim 2, wherein the electricity generated by the generator is used to power the electrolysis of the water.

4. The method of any of the preceding claims, further comprising the provision of an atmospheric water generator to capture the water used in the formation of the hydrogen and oxygen gases.

5. The method of any of the preceding claims, wherein the thermal energy produced by burning hydrogen is imparted on the pressure vessel via a burner wand located within the pressure vessel.

6. The method of any of the preceding claims, further comprising monitoring the levels of solar energy being collected by the solar furnace and, if necessary, supplementing the heating of the pressure vessel by burning hydrogen.

7. The method of any of the preceding claims, further comprising storing the hydrogen gas produced by the electrolysis of water until such time as it is required.

8. The method of any of the preceding claims, further comprising routing exhaust gases, generated by burning hydrogen, past a heat transfer medium storage tank, which supplies the vessel inlet, so that the thermal energy in the exhaust gases can be imparted to the heat transfer medium within the storage tank.

9. A solar furnace capable of being operated 24-hours a day, said furnace comprising: a heatable pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; a lens array positioned to capture and direct solar energy on to the pressure vessel so as to heat said pressure vessel; electrolysis means for decomposing water to form hydrogen gas and oxygen gas, whereby, in use, the energy to drive the electrolysis means is obtained from the heat transfer medium leaving the pressure vessel; and pressure vessel heating means that generate heat by burning the hydrogen gas formed by the electrolysis of water.

10. The solar furnace of claim 9, further comprising an electricity generator that is configured to use the heat transfer medium leaving the pressure vessel to generate electricity.

1 1 . The solar furnace of claim 10, wherein the electrolysis means is a powered by the electricity generated from the heat transfer medium.

12. The solar furnace of any of claims 9-1 1 , further comprising an atmospheric water generator that, in use, captures water from the environment and supplies it to the electrolysis means.

13. The solar furnace of any of claims 9-12, wherein the pressure vessel heating means comprises a hydrogen burner wand located within the pressure vessel.

14. The solar furnace of any of claims 9-13, further comprising control means that monitor the levels of solar energy being collected by the lens array and operate the pressure vessel heating means appropriately to maintain the pressure vessel at a predetermined operational temperature.

15. The solar furnace of any of claims 9-14, further comprising a storage tank to house the hydrogen gas produced by the electrolysis means until such time it is required by the pressure vessel heating means.

16. The solar furnace of claim 15, wherein the hydrogen storage tank comprises a carbon-fibre reinforced shell with a polymer lining.

17. The solar furnace of any of claims 9-16, further comprising a heat transfer medium storage tank with one or more polycarbonate mesh mats provided on the outer surface thereof to control the EMR reflection and absorption characteristics of the tank.

18. The solar furnace of any of claims 9-17, wherein the pressure vessel heating means comprises an exhaust conduit that directs the exhaust gases past the heat transfer medium storage tank before the gases are expelled from the solar furnace.

19. The solar furnace of any of claims 9-18, wherein the solar furnace is housed within a standard shipping container, said shipping container being configured to completely enclose the solar furnace and provide means to allow solar energy to reach the lens array.

20. The solar furnace of claim 19, wherein the said mean comprise an opening in the top of the container that is configured to provide unobstructed access to the lens array.

21 . The solar furnace of claim 20, further comprising adjustable support members that can be operated to raise and lower the lens array relative to the opening in the top of the container.

22. The solar furnace of claim 19, 20 or 21 , wherein the container also contains one or more storage tanks selected from the group consisting of: water storage tank, hydrogen storage tank, oxygen storage tank, heat transfer medium tank.

23. A solar furnace array comprising a plurality of solar furnaces stacked on top of one another, wherein each solar furnace comprises a lens array and a pressure vessel with a convoluted internal pathway running from a vessel inlet, where a heat transfer medium is introduced, to a vessel outlet, where the heat transfer medium leaves the pressure vessel with increased kinetic energy; wherein the solar furnaces in the stack are oriented so that the lens array of each solar furnace is directed towards the lens array of an adjacent solar furnace to form lens pairings and the solar furnace on the top of the stack is oriented skywards; and said array further comprising solar energy collectors positioned on the exterior of the array and one or more light conduits that direct solar energy from the collectors to the lens pairings within the stack.

24. The solar furnace array of claim 23, wherein the solar energy collectors are lens arrays located adjacent the lens array of the solar furnace on the top of the stack.

25. The solar furnace array of claim 23 or 24, comprising a solar furnace according to any of claims 9-18.