GB2472033A

GB2472033A - Greenhouse system utilising recovered heat

Info

Publication number: GB2472033A
Application number: GB0912701A
Authority: GB
Inventors: Gary Tulie
Original assignee: ALGOIL Ltd
Current assignee: ALGOIL Ltd
Priority date: 2009-07-22
Filing date: 2009-07-22
Publication date: 2011-01-26
Also published as: GB0912701D0

Abstract

A greenhouse system comprises a supply of clean water, evaporators 4 for evaporating the seawater and a condenser 19 for condensing water vapour. The condenser may be in the form of an air to water heat exchanger or an air to air heat exchanger. Heat recovered in the heat exchanger is used to further aid evaporation of seawater. Alternatively, a mechanical vapour recompression unit can be used to recover heat. Air hung seaweed may be used as an evaporator. The temperature in parts of the greenhouse system is optimised for cultivation. The greenhouse system may also incorporate seawater treatment based on alternate magnetic poles which prevents limescale and results in the precipitation of fine crystals of calcium carbonate. The calcium carbonate can be collected by filtration and used in various applications, such as a cement substitute. As a by-product of the greenhouse system, cool air is made available for air conditioning.

Description

Heliostream

Background

Globally, the number of people continues to increase, as does the amount of water used. In many of the more arid parts of the world, demand for water considerably exceeds the ability of natural systems to sustainably supply. As a result of this, underground water sources are being overexploited. We are effectively mining the water rather than harvesting it. Onc&this ground water is gone, there will be no further regular supply, and those people presently depending on the groundwater will face serious problems. For the rich, it is simply a case of bringing in water from more distant sources, desalinating water, or relocating to a more favoured location, however for the poor, it means failed crops, thirst, drinking dirty water, poor health, and very often a slow premature death.

Current desalination technologies are too expensive, and too energy intensive for general application, especially in the poorer arid regions. Hygiene and health, agriculture and food supply are thus compromised. Were sufficient resources made available for example using aid from developed nations, supplying adequate water using conventional distillation or reverse osmosis would still be problematic, and may ultimately result in an increased climate change pressure due to increased use of fossil fuels.

The intent of this invention is to increase the available water supply by replicating on a small scale the hydrological cycle by which water is evaporated by the sun, condenses, and falls back to Earth as potable fresh water. The water produced by the system could either be potable, or irrigation quality depending on the degree of filtration, and would in any case be a vast improvement on current water quality in the most water stressed environments.

Introduction to Heliostream

Heliostream is an integrated system designed to meet a wide range of needs. The system makes provision for a large volume of water production by solar desalination, greenhouse horticulture in cooled conditions, electricity production from integrated photovoltaic systems, space cooling, and anti-desertification measures using some of the water produced. By harnessing multiple benefits, the cost of supplying any one of the above services is kept low. Greenhouse impact is also significantly negative, as the presence of water will enable significant biological sequestration of Carbon Dioxide, whilst avoidance of imports from distant lands -enabled by local cultivation of fruit and vegetables will greatly reduce the embedded emissions of the local food supply. Further, the system will allow for widespread use of evaporative cooling which is substantially more energy efficient than conventional air conditioning, displacing fossil fuel use. The Heliostream uses a roof or horizontal shade curtain of translucent photovoltaic panels, which can potentially supply substantially more electrical power than it uses. The system has potential to benefit from the possibility of carbon offset revenues, as well as making a very considerable contribution to the relief of poverty in some of the poorer coastal desert lands.

The main features of the system are a greenhouse, evaporators, and heat recovery ventilation with heat reuse.

The Process A. In The Greenhouse In desert areas, air is usually hot and dry. When said air is passed over evaporators, water evaporates absorbing latent heat. Air is thus humidified and cooled to the extent that heat is used to drive the evaporation process. Cool damp air is ideal for greenhouse crops in hot lands, and significantly reduces the irrigation needs of said crops. Rather than allow the air to become significantly warmer within the crop area of the greenhouse, the greenhouse is divided into top and bottom layers by a transparent or semi-transparent curtain which offers the opportunity to provide a degree of shade to the crops. Air passes from the greenhouse entry, along the greenhouse below the curtain -passing over a number of evaporators on the way to reduce the rate of temperature rise, then up to the upper layer of the greenhouse where it is further warmed by the sun and continues to pass over evaporators so that as its temperature rises, near 100% humidity can be maintained. Ideally temperatures in the lower greenhouse would be maintained between around 20-30 degrees centigrade to optimise conditions for cultivation, whilst air exiting the upper level and going to the condenser is at a temperature of around SOdegrees centigrade or higher whenever possible (with 100% humidity).

B. In the Condenser The system makes use of a water cooled interface in the form of an air to water heat exchange ventilator. As air enters the condenser, it is exposed to increasingly cold water filled pipes or radiators, so that the air temperature drops and most of the water content of the air condenses out on the radiator surfaces. Water in the radiators passes in the opposite direction and is heated as it cools the incoming air. The majority of the heat which was previously in the air now transfers to the water in the radiators, from where the heat can be reused to drive a supplementary evaporation cycle. The cooled air leaving the condenser is split between two exits, one vented to outside -or sent to nearby buildings to provide air conditioning, and the other going from the condenser to the secondary evaporator circuit.

C. In the Secondary Evaporator Circuit Water heated by passage through the cooling radiators in the condenser is used to drive an evaporation cycle. This is achieved by passing the now hot water into a series of radiators which alternate with evaporators. As an alternative, the radiators themselves could be coated with an evaporating surface such as cloth. The water direction is from the hottest to the coldest radiator, with the coldest radiator at close to the dew point temperature of the outside air as possible. Air taken from the condenser is passed over each radiator in turn starting with the coldest -alternating with evaporators so that at each radiator it is warmed, then passed to the next evaporator where this extra heat is partially exchanged for increased absolute humidity. A target of 100% relative humidity applies throughout, with a temperature on exit as close as possible to the temperature of air exiting the upper stage of the main greenhouse. The air from this system is fed into a T-junction joining the greenhouse air in going through the condenser. In this way, by reusing heat, the volume of water evaporated and condensed is increased so that the amount of water captured per hectare per day is greater than could be achieved without heat recovery. If it were considered beneficial to optimising the process, solar thermal panels can be used to boost the inlet temperature of the secondary evaporator circuit -so allowing more moisture to be carried per cubic meter of air, or a heat pump can be used to provide a final temperature boost -reducing volume flow rate of both water and air whilst raising the final temperature of humid air leaving the evaporator subsystem.

The Heliostream is designed to be an efficient solar still in the form of a greenhouse designed to generate large quantities, of potable water at modest cost. Previous technology has employed evaporatos and condensers, but has made no concerted effort to recover the heat liberated by the condensation of water, and hence to reuse said heat for further evaporation. Reuse of this heat is the fundamental process difference between the Heliostream and previous systems of seawater greenhouse, and is anticipated to result in substantially more water collection than previous systems.

Note: -Heat recovery ventilation systems are in common use with 80-90% heat recovery, indicating potential for a substantial upgrade in available water capture with an optimised Heliostream design.

The system consists of a number of parts, each using broadly conventional technology. The patent application for Heliostream therefore depends on the novelty of the overall integrated process rather than that of any of its components.

Subsystem 1 -Collection and delivery of seawater, and drainage of brine.

In order to carry out any kind of desalination, it is first necessary to obtain a supply of clean sea water. Subsystem I would consist of a seawater inlet with filtration, a large plastic or plastic lined pipe, a seawater reservoir, header tank, associated pumps, and a system of distribution pipes to deliver water to drip trays I mist irrigation system. In the latter case, seaweed growing in air would be kept moist by a regular wetting of seawater, and would serve as living evaporators. Finally, drainage systems to collect used water (brine) and safely return it either to the sea, or to saltpans for salt production. This last is essential to avoid salt damage to the land.

Subsystem 2 -The Evaporators and condenser There are two ways to desalinate sea water, the first, evaporation followed by condensation, and the second, reverse osmosis. Both are in common use for the production of fresh water. The Hydrological cycle which drives the Earth's climate In traditional desalination by distillation, water is boiled and turned to steam which is then condensed, whilst in reverse osmosis, water is forced under pressure through a water permeable membrane which allows water through but blocks salts.

The Heliostream uses a variant of the former system, but at lower temperatures, relying on partial pressure of water vapour rather than steam. In this it replicates the Hydrological cycle on a small scale.

There are two ways to measure humidity -the first relative humidity, in which humidity is measured as a percentage of the maximum water holding capacity of air at the measured temperature, and the latter, absolute humidity which is measured as grams per cubic meter of air.

The absolute capacity of air to hold water as vapour doubles at saturation for every 11.1 degrees centigrade rise in temperature.

Water content of air at lOO% humidity at sea level is roughly as follows OC Sg / cubic meter I OC lOg / cubic meter 20C 1 9g I cubic meter 30C 34g I cubic meter 40C 62g I cubic meter 50C 1 1 9g / cubic meter It follows that for any given temperature, if you first saturate the air with water vapour, and then reduce its temperature by 22.2 degrees centigrade, that approximately 75% of the water vapour held in air will condense given sufficient condensation surface or condensation nuclei.

The Heliostream system aims to produce 100% humid air which is progressively raised to around 50 degrees centigrade whilst retaining 100% relative humidity. The air is then passed over a condenser where it is cooled to around 25C giving around 90 ml of water per cubic meter of air passing through the condenser.

In order to evaporate salt water in large volumes, it is necessary to have heat, salt water, and sufficient interaction between the two to bring about evaporation. This is best provided by a large damp surface exposed to hot moving air.

The Heliostream uses several kinds of interchangeable evaporator -cellulose fibres, cardboard, recycled or low grade cloth, or a living evaporator made up of mist irrigated seaweed (or other salt tolerant crops) suspended from a net or other suitable matrix and growing in air. Marine Macro-algae are best suited to relatively low temperature sections of the system. Where Algae are grown in this way, they can be harvested and utilised for the production of a wide range of products including agar and related water absorbing gels, which when added to the desert soil will enhance productivity by retaining water in the soil -preventing it from unduly draining away.

In this way, the algal crop can enhance the overall effectiveness of the greenhouse by improving the water holding capacity of an increasing area of soil in the surrounding area as time passes.

A further possibility is the use of seawater ponds within the greenhouse for the cultivation of micro-algae, shellfish, shrimp or wet fish. These ponds would have enhanced evaporation as a result of the use of aeration systems, and allow for a wider

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range of crops to be cultivated in the greenhouse. The high evaporation rates in the pond may be particularly conducive to shellfish as carbonate precipitates out of solution. Seawater is a saturated solution of carbonate, so any evaporation results in precipitation. This could well assist in the formation of shell.

Incoming air is pre-humidified before entry to the greenhouse, and through latent heat given to the evaporating water, cooled well below ambient temperature. (At an outside temperature of 45 degrees centigrade with 10% humidity, it is estimated that humidification of the air would cool it to the low 20's degrees centigrade, with near 100% humidity, so optimising conditions for crops in the greenhouse. Minimum possible temperature is governed by the dew point which varies with ambient temperature and absolute humidity.

Collection of Calcium Salts Given that seawater is a saturated solution of Calcium ions, and readily precipitates calcium salts such as Calcium Carbonate, the Heliostream offers options for the collection of these salts as a partial substitute for cement. Use of Physical Water Treatment systems based on alternating magnetic poles would in any case be beneficial to keeping pipes clear of limescale, and results in the formation of fine crystals of carbonate. These can be collected by filtration and utilised in various applications such as cement substitutes, mineral supplements, and for the treatment of fish tanks, as a pigment or as a coating agent. To enhance precipitation, carbon dioxide can be pumped through the seawater, which process results in the sequestration of carbon dioxide. In this way, by mixing the resultant calcium salts with traditional cement, net emissions of the resultant concrete are therefore substantially reduced. This process can be used to reduce the tendency for calcium salts to precipitate within the pipes, so reducing the degree of maintenance required.

Condenser The condenser takes the form of an air to water heat exchange ventilation unit optimised for heat recovery and condensation. An alternative air to air heat exchanger can substitute for air to water. Heat recovered in the heat exchanger is used to evaporate water so increasing the volume of water which can be extracted from each hectare of greenhouse. The amount by which the volume of water produced increases is governed by the efficiency of heat recovery and reuse. Assuming 50% efficiency, water recovery doubles as compared to a system without heat recovery, for 80% efficiency, increases 5 fold, and at 90% 10 fold. It is therefore important to optimise the design of the condenser for heat recovery as small improvements can result in large changes in the amount of water captured, and consequently on the economic performance of the system.

Subsystem 3 -Utilisation of recovered heat in a secondary evaporation system.

Using a once through system, and capturing the heat falling on one hectare of greenhouse for evaporation plus the heat in incoming air, the maximum amount of water which can be evaporated and captured is fixed by the amount of solar energy falling on the greenhouse and the incoming heat in the inlet air. Current technology has a maximum capture of the order of 100 cubic meters per hectare day. (This is based on around 60 Megawatt hours of thermal energy falling on said hectare.) The purpose of the recovered heat reutilisation system is to make use of the heat given up by condensing humid air to heat water and to then use this heat to evaporate water in a secondary greenhouse. The secondary greenhouse is purely for evaporation of water. This secondary greenhouse does not cultivate any crops.

Option 1 for heat recovery Air to water heat exchanger An air to water heat exchanger. This option allows heat to be stored as hot water and moved around with relative ease. Hot water is produced in the water side of the condensing air to water heat exchanger as hot air makes contact with the "radiator" in which it is held. In order to maximise condensation and heat recovery efficiency, water starts cold, and passes through a series of increasingly warm radiators until it reaches a temperature just slightly below that of the incoming air. As air strikes the radiator, the relative cool of the radiator causes water to condense, giving up latent heat of evaporation to the radiator as it does so. As the air passes over the sequence of increasingly cold radiators (travelling in the opposite direction to the water), this process continues until a large proportion of the water vapour present in the exhaust air has condensed out, and much of the heat in the air including latent heat of condensation has transferred to the water in the radiators. The water then continues through the circuit and is fed to a set of radiators in series, each a little cooler than the previous one. Air is fed through a series of evaporators in the opposite direction so that air temperature and absolute humidity increases to the highest level which can be achieved using the recovered heat. Air from the secondary evaporator system is fed into the condenser along with hot humid air from the greenhouse. The secondary evaporator system is in effect the exact opposite of the condenser system, with water progressing from hot to cold, and air progressing from cold to hot and humid.

The water in the radiators is progressively cooled by latent heat of evaporation as the evaporators do their job, so that finally, water that has passed through the sequence of radiators cools to a temperature close to the dew point of air under ambient conditions. As cold water, this water re-enters the radiators of the condenser system and starts to go through the circuit again.

Heat tends to rise, so that it is envisaged that subsystem 3 -the secondary evaporation greenhouse be built on top of the condenser. This will also minimise the footprint of uncultivated land.

As an intermediate step in order to raise the temperature of water in the radiators a heat pump or solar heaters could be used between the condenser and the radiators of the evaporator greenhouse. By boosting the temperature of the water in the secondary evaporator, it is possible to obtain humid air at a higher temperature -closer matched to the temperature of air entering the, condenser from the greenhouse. As increasing the temperature of air greatly increases the quantity of water vapour which can be held in a given volume of air, flow rate of air for a given level of water production would be significantly reduced, as would the flow rate of hot water required in the condenser / radiator circuit. The size of the device could thus be reduced, or the volume of water recovered increased.

Option 2 for heat recovery Air to air heat exchanger Air to air heat exchangers could be used, and would combine the condenser with the secondary evaporator in a single system. Evaporators would have to be installed in the heat exchanger to humidify incoming outside air progressively as it warms by cooling the humid exhaust air leaving the greenhouse.

Option 3 for heat recovery Mechanical Vapour Recompression is an alternate technology which can be used to recover heat from the condenser. Maximum absolute humidity remains very nearly the same for a given temperature regardless of pressure. Suppose 100% humid air is compressed to 10 atmospheres pressure whilst maintaining constant temperature, close to 90% of the water content condenses. In practice, compressing humid air raises its temperature, so that after a series of compression stages heat is recovered at a substantially higher temperature than is possible without compression. By cooling said compressed air, a very high proportion of the humidity in said air is condensed.

Releasing the remaining overpressure, air temperature drops substantially below ambient, giving opportunity for use in refrigerated and frozen storage as well as air conditioning applications. A further advantage is that a higher temperature differential can be obtained between the humid air inlet and the water which provides cooling effect for condensation. The proportion of water condensed in this system is greater than uncompressed systems, and efficiency of heat recovery is substantially enhanced.

The high temperatures achieved in water heated by the circuit which cools compressed air allows for higher temperatures in the radiators of the secondary evaporator system, and thus boosts the level of absolute humidity which can be achieved in the secondary evaporation system. This greatly reduces the volume of air required to be fed through the system per volume of water recovered, giving either a smaller system, or a greater water production Using Mechanical Vapour Pressure compression, air can be moved through the system pumped by the compressor. This allows removal of some of the fans which Advantage -for small temperature differences, COP values of 10-30 are possible, which is significantly better than the alternative heat pump system. A very high efficiency of heat recovery can be achieved with this system, dramatically increasing the amount of water which can be extracted, however at a cost of comparatively high electrical power consumption. A full analysis of the system would therefore be needed to determine the specifications of any individual system, and to ensure that any enhancements to water capture bring overall C02 emission reductions after sequestration by increased crop growth has been taken into account. The additional costs and energy consumption of this system can be substantially offset where refrigerated and frozen warehouses or utilisation of cold for air conditioning is possible on or close to the site.

Disadvantage -Mechanical vapour compression is likely to be significantly more expensive than other systems, so cost benefit analysis is essential.

Process sequence Warm dry air> cool wet air> progressively warmer wet air through the greenhouse (Planted lower layer)> Further Solar warming and evaporation> rises at far end of greenhouse to hot layer> further heating and evaporation> condenser for progressive cooling and condensation with heat removed to the secondary evaporators.

Parts shown in fig 1 -3.

1. Small greenhouse with alternating evaporators and radiators to heat and increase humidity of air before passing it through the condensing room. (All evaporators with drains to remove excess brine not evaporated on the evaporator -this is essential to prevent soil damage from increased salinity).

2. External hot dry air drawn in through secondary evaporators -most likely morning and evening only.

3. Cooler humid air from lower condenser room returned to evaporator greenhouse. -This makes use of any residual latent heat and increased humidity remaining in the exhaust air from the condenser.

4. Sea water evaporators. -Various materials possible including cellulose fibre, cloth, or living seawater mist sprayed seaweed. The latter, suitable for the cooler portions only.

5. Heat exchange radiators and fans.

6. Air flow with increasing humidity and temperature.

7. Air to water heat exchange pipe work returned to condenser room -water exits the condenser room at a temperature only marginally above dew point.

8. Air to water heat exchange pipe work entering the evaporator greenhouse from the condenser -temperature of water close to that of air exiting the main greenhouse -same or higher temperature if solar thermal heat or a heat pump are used to boost temperature, if done, air flow volumes in the evaporator room would be reduced per water produced as absolute humidity would be higher.

9. High level duct from upper main greenhouse joins duct from evaporator greenhouse and feeds hot humid air into the condenser room.

10. Air flow with increased humidity.

11. Last seawater evaporator before condenser room.

12. Upper and lower greenhouse separated by a "clear" horizontal curtain. -This curtain could incorporate a degree of shading, or of translucent photovoltaic electricity generation. The curtain increases the temperature difference between lower and upper sections of the greenhouse to optimise conditions for crops in the lower section whilst maximising evaporation and temperature in the upper.

13. Upper return air flow with increased humidity -air travels two full lengths of the greenhouse, outwards along the bottom, and back along the top, picking up heat and using said heat to boost absolute humidity all the way.

14. Crop greenhouse with evaporators in both lower and upper sections increasing absolute humidity before passing through to condensing area.

15. Upper and lower fan assisted seawater evaporators to help maximise humidity before condenser room.

16. Air temperature rises allowing increased absolute humidity within the greenhouse -Flow rate adjusted to keep temperature in the cultivation area acceptable whilst giving high temperature entry into the condenser room.

17. Clear horizontal curtain stopped before the end of the crop greenhouse to allow air to ascend to the upper level of the greenhouse and return along the length of the greenhouse to the condenser.

18. Warm humid air rises to the upper level of the crop greenhouse.

19. Condenser Heat exchanger -cold water radiators meet hot air so condensing out most of the water vapour content. Air cools progressively through contact with water cooled condensers while water warms progressively whilst passing in the opposite direction.

20. Seawater evaporator at external greenhouse wall to humidify and cool air entering the greenhouse -this reduces crop water demand by both cooling and humidifying thereby reducing the rate of evapotranspiration.

21. Cool humid air flow.

22. Humid air now warmed by the greenhouse.

23. Evaporator Heat exchanger -hot water radiators meet cold humid air which then passes through evaporators increasing water vapour content. Air warms and humidifies progressivelythrough contact with water heated by passage through the condensers. Water in the radiators is progressively cooled by contact with cool humid air until its temperature is marginally higher than the dew point.

24. Condensing area with air to water heat exchangers to maximise potable water extraction. (Variants with air to air heat exchangers, or mechanical vapour recompression are also considered) 25. External hot dry air flow into the system 26. Fan draws air in -prior to contact with the first evaporator.

Claims

Claims 1. This invention recovers latent heat of evaporation so as to enhance the amount of seawater which can be evaporated and condensed in a greenhouse system.
2. Using air hung seaweed as an evaporator, the seaweed crop facilitates terra-reforming by use of seaweed derived products to hold moisture in the soil.
3. Use of an air to water heat exchanger recovers solar heat from the greenhouse and enables its reuse to evaporate more seawater, and hence permit the collection of more potable water.
4. As an alternate to 3, use of an air to air heat exchanger with condensation of fresh water on one side, and evaporation of seawater on the other recovers solar heat from the greenhouse and enables its reuse to evaporate more seawater, and hence permit the collection of more potable water.
5. As a second alternative to 3, a mechanical vapour recompression unit allows recovery of solar heat from the greenhouse and enables its reuse to evaporate more seawater, and hence permit the collection of more potable water.
6. Large volumes of cooled air are made available for space cooling facilitating air conditioning of nearby buildings.
7. Cold seawater pumped to the seawater greenhouse enables the cooling of fresh water using a heat exchanger to reduce the risk of Legionella or other dangerous bacteria in the public mains.
8. The same cooling process as claim 7 permits cooling of water for a district cooling applications.
9. In the event of mechanical vapour recompression being used to condense out water, heat from the greenhouse is upgraded to higher temperatures enabling use for commercial purposes and sanitary hot water.
10. In the event of mechanical vapour recompression being used, release of pressure at the end of the cycle results in a substantial reduction in temperature suitable for providing frozen or refrigerated storage.
ii. In the event of mechanical vapour recompression being used, release of pressure at the end of the cycle results in a substantial reduction in temperature suitable for providing cold water or slush ice for efficient district cooling, or chilling of the public water supply.
12. The system includes options for cultivating marine plants, shellfish, and fish in pond conditions within the device.
13. The system allows for collection of calcium salts as they precipitate during evaporation of seawater.
14. The system allows for carbon sequestration as carbon dioxide is fed through the evaporating water to enhance precipitation of calcium salts.
15. By using mechanisms to precipitate Calcium salts in a controlled way, the amount of limescale forming in project pipe work is greatly reduced cutting maintenance costs.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-Claims 1. A structure and system combining solar desalination, horticulture, evaporative cooling with cellulose, seaweed or other suitable materials acting as an evaporator, photovoltaic power generation, and recovery of salts, the system comprising a greenhouse, seawater evaporators, a condenser unit with heat recovery, a secondary evaporator circuit using recovered heat, the system in addition offering the possibility of fish farming, and permitting recovery of calcium salts for building materials, and sea salt for culinary use.2. This system as in claim 1 that recovers latent heat of evaporation so as to enhance the amount of seawater which can be evaporated and condensed in a greenhouse system.3. Air hung seaweed according to claim 1 as an evaporator so that the seaweed crop facilitates terra-reforming by use of seaweed derived products to hold moisture in the soil.4. The system according to claim 1 that uses an air to water heat exchanger to recover solar heat from the greenhouse and enable its reuse to evaporate more seawater, and hence permit the collection of more potable water.5. As an alternate to 4, use of an air to air heat exchanger with condensation of fresh water on one side, and evaporation of seawater on the other to recover solar heat from the greenhouse and enable its reuse to evaporate more seawater, and hence permit the collection of more potable water.Q 6. As a second alternative to 4, a mechanical vapour recompression unit to allow recovery of solar heat from the greenhouse and enable its reuse to evaporate more seawater, and hence permit the collection of more potable water.7. The system in claim 1 where large volumes of cooled air are made available for space cooling facilitating air conditioning of nearby buildings. 8. The system in claim 1 where cold seawater pumped to the seawater Q greenhouse enables the cooling of fresh water using a heat exchanger to reduce the risk of Legionella or other dangerous bacteria in the public mains.9. The same cooling process according to claim 7 to permit cooling of water for district cooling applications.10. In the event of mechanical vapour recompression being used to condense out water in the system in claim 1, heat from the greenhouse is upgraded to higher temperatures enabling use for commercial purposes and sanitary hot water.11. In the event of mechanical vapour recompression being used as in claim 10, release of pressure at the end of the cycle to result in a substantial reduction in temperature reduction suitable for providing frozen or refrigerated storage.12. In the event of mechanical vapour recompression being used as in claims 10 and 11, release of pressure at the end of the cycle to result in a substantial reduction in temperature suitable for providing cold water or slush ice for efficient district cooling, or chilling of the public water supply.13. The system in claim 1 with options for cultivating marine plants, shellfish, and fish in pond conditions within the device.14. The system in claim 1 that allows for collection of calcium salts as they precipitate during evaporation of seawater.15. The system in claim 1 that allows for carbon sequestration as carbon dioxide is fed through the evaporating water to enhance precipitation of calcium salts.
16. By using mechanisms to precipitate Calcium salts in a controlled way according to claim 14, the amount of limescale forming in project pipe work is greatly reduced cutting maintenance costs. (\J Co