Patent Application
20130192131
The present invention relates to improvements in water efficient greenhouses for efficient growth of agricultural produces and more particularly to a renewable energy desalination greenhouse which can utilize seawater or brackish water to perform a desalination process which, using renewable energy, grows crops in a shorter time period while using only a small fraction of the water which would otherwise be utilized in open field production. The present invention is also shown to be amenable to automated and continuous agricultural production.
In arid areas of the world a conventional greenhouse has a number of disadvantages. Increased sun light can cause a greenhouse to overheat. The answer to overheating has been to open the greenhouse to a cross breeze and increase evaporation for cooling. However, in desert areas this simply translates into a prohibitively greater water usage than would be experienced with the greenhouse in cooler climates. A conventional greenhouse project in the desert would normally require a commitment of several multiples of the amount of water than would be necessary in a cooler climate. Conventional greenhouses contemplate fresh water to be applied to plants in an amount to not only provide a nourishment medium for the plants, but also to humidify the internal space within the greenhouse. However, the internal space within the greenhouse must not over heat, and the main mechanism to prevent overheating is to create a cross draft of outside air to cool. However, this cooling evaporates and dehumidifies the interior growing space of the greenhouse.
The desert environment is well known to have very little fresh water available, or perhaps only sea water, brine from groundwater desalination plants or brackish water available. Such desert environment is also known to have high solar availability, but suffers from excess temperatures associated with the intense solar exposure. The shortcomings of the conventional or more advanced solar still design, where water in an enclosure with a sun facing inclined transparent cover condenses desalinated water on the inside of the cover for collection. Its heat input may be increased by mirrors in order to increase yield of desalinated water per square meter of cover per day, however the original simple solar still and its many variations suffer from the following shortcomings: (1) when the solar still is dedicated for desalination only the cost of the structure becomes very expensive and so does the desalination process and output; (2) as the moisture in the tightly closed cavity of the still increases upon solar heating the evaporation is reduced and the still becomes less efficient; (3) Some of the desalinated water that condenses on the lower side of the transparent cover is preferentially evaporated relative to the salty water in the basin because of its lower density and therefore less salty water is evaporated; (4) there is a problem of obtaining an efficient condenser for the solar still and reliance on the air temperature outside the still to condense the water is not efficient, and the transparent cover becomes hot itself and the temperature drop between the evaporating moisture and the cover is not significant enough to allow substantial condensation; and (5) the above factors result in a still that is expensive with a low output of 2-5 liters per square meter per day. It is therefore desirable to invent a solar desalination device that is less expensive and is more productive per unit of space per day.
The desalination greenhouse is a solar still that doubles as a greenhouse. The desalinated water produced could be used for any purpose such as drinking, boiler water and chemical industry due to its high purity or for agriculture and any combination of the above as it is inexpensively produced. The structure is essentially a greenhouse with an additional inexpensive extra cover and with a side benefit of desalination. The capital cost is therefore appropriated primarily for the greenhouse crop product, and the capital cost of desalination is significantly reduced. The desalination greenhouse of the invention also provides a number of flexible operation controls to produce crops rapidly in a desert environment using brackish water. Both winter and summer operations can be optimized and the desalination greenhouse helps to compensate for changing exterior process operating conditions. Even more surprisingly the desalination greenhouse can produce a source of potable water given an input of only brackish or sea water.
The desalination greenhouse can be optimized for superior crop production and minimization of diseases. It minimizes heating and cooling requirements due to its superior insulation and absorption of heat in summer and its release in winter without obstructing natural light transmission. It uses renewable energy to desalinate water through condensation of sun and wind heated air that is forced through the cavity between the two structures to evaporate a very thin layer of water, and then to a black cover heated zone, to evaporative cooler wet pads. Condensation occurs on the inner surfaces of the outer and inner sections of the desalination greenhouse. Condensation of the inner greenhouse humid air may be achieved through a heat exchanger carrying the cooled water piped from the through of the evaporative cooling pads. The roof of the inner section of the desalination greenhouse is wetted evenly with sea or brackish water for evaporation which also cools the structure of the inner section of the desalination greenhouse. 1.0 to 10.0 mm v to u shaped grooves in the hard cover roof material of the inner section of the desalination greenhouse, preferably made of polycarbonate, guide the water downward and spread it evenly over the surface, providing the right depth for effective evaporation and cooling of the inner greenhouse. The inner greenhouse frame structure elements may be extended to support the outer greenhouse poly cover. The double shell greenhouse as described provides an efficient and cost effective means of heat utilization to desalinate sea or brackish water for irrigation and other uses, reduce heat input into the inner greenhouse, and minimize the crop requirement by over 95% by cutting the production cycle substantially and recovering the evapo-transpiration water.
The space over the water being desalinated is never saturated due to continuous air movement. The thickness of the salty water being evaporated is maintained very thin, within one centimeter, in order to chill the water to lower temperatures through evaporation and removal of moisture by the air. The even distribution of the salt water and its thin layer covering the roof and sides of the production greenhouse, made possible by the channel design (grooves) provides the production greenhouse with a cold surface that makes the environment more conducive to optimal plant growth and enhances condensation on the ceiling and sides of the production greenhouse. The outer shell greenhouse is a canopy to trap the moisture evaporating from the roof of the production greenhouse and enhances condensation on the ceiling and inside wall of the outer shell greenhouse.
An 1008 square meter floor greenhouse, for example, (36×28 and 4 meter high at the gutter and 8 meter high at the center) with one meter space between the inner and outer shell, has a total surface are of roof and sides of 2800 square meters allowing for doors and other vents. This area shall produce about 10 liters per square meter per day, or 28,000 liters per day. A seawater desalination greenhouse of a single shell (1), which relied on cold deep seawater as a condenser, produced between 3 and 6 liters per square meter per day depending on whether the environment is tropical or oasis. When the crop produced in the present desalination greenhouse invention is barley for animal forage production, the cycle per crop averages ten days from seed to harvest (2). The desalination greenhouse will produce 1500 tons of forage annually and consumes 4500 cubic meters of desalinated water per year for irrigation.
The desalination greenhouse of the current invention produces over 10,000 cubic meters of desalinated water, enough for forage irrigation and drinking water for 1000 people, each using 15 liters per day. The desalination greenhouse of the current invention could contribute to solving problems of many regions of the world that require desalinated water for human consumption, industry and irrigation of crops. The high value of the desalinated water makes it valuable for boiler and chemical process water which is expensive to produce and requires substantial energy due to its high level of purity.
The air cycle steps of the desalination greenhouse may be represented as follows: Ambient air>disinfection>filter>blower>distribution>roof humidification>heating>pad humidification>condensation>ambient air. The water cycle steps in the desalination greenhouse may be represented and summarized as follows: a) Salty water. Salty water spread over roof of production greenhouse>evaporation and cooling on roof>evaporation and cooling on evaporation pads or water shower>heat exchanger condenser>Collection and recycle with bleed and blend with fresh salty water; b) Desalinated water. Condensed water on inside and walls of outer shell+Condensed water on inside and walls of production greenhouse+condensed water on heat exchanger carrying cold water from evaporation pads
All condensate is collected in their own gutter like channels separate from salty water channels.
The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which:
Referring to
The outer shell 23 shown is of simple construction and includes a series of vertical walls 31 which include side walls and end walls and topped by a roof 33 which includes a pair of sloped roof walls. Likewise, inner shell 25 shown is of simple construction and includes a series of vertical walls 37 which include side walls and end walls and topped by a roof 39 which includes a pair of sloped roof walls. Roofs 33, 39 of both greenhouses are preferably similar to each other (although shown in
Any number and type of protruding supports 51 may be anchored to the structural body of either of the outer shell 23 or inner shell 25 and for the purpose of anchoring the desalination greenhouse 21, securing the outer shell 23 or inner shell 25 to each other, or for anchoring the outer shell 23 to the ground, with
Conversely, a separate door may be provided for each of the outer shell 23 and inner shell 25, with the space between the two doors remaining an active part of the roof and side cavities 45 and 47. This may not be as preferred as the opening of either of two such separate doors would disrupt the action and flow going on in the roof and side cavities 45 and 47. When access to the inner chamber 41 is had over a long time, such as the introduction or removal of soil and plant materials, the roof and side cavities 45 and 47 would be significantly disrupted. In yet a further alternative, the end wall 57 may be designed not to contain a side cavity 45 and to be built as a wall and support structure common to both the outer shell 23 and inner shell 25. In this case, the user is giving up the desalination action at the end wall 57. However, as can be seen in
With the basics of an overall structure of an example desalination greenhouse 21 having been seen in
The forced air fans 53 introduce ambient air into the roof and side cavities 45 and 47 throughout the desalination greenhouse 21. The hot air will be utilized to evaporate and possibly cool any saline or brackish water which may be introduced onto the surface of the outside of the inner shell 25. The air circulating in the roof and side cavities 45 and 47 whose humidification may be increased after contact with moisture from the outside of the inner shell 25 may deposit some fresh water droplets via condensation on the inside of the outer shell 23. The air circulating in the roof and side cavities 45 and 47 whose humidification may be increased after contact with moisture from the outside of the inner shell 25 may then proceed into the inside of the inner shell 25 through an optional cooling pad 63. Cooling pad 63 may be a matrixed structure which entrains some liquid to facilitate an increased contact between air circulating in the roof and side cavities 45 and 47 and liquid water which may be present in the cooling pad 63 through a variety of mechanisms.
The cooling pad 63 can be a passive fibrous flow device to enable a passing gas to make a greater degree of contact with a wetted area. Cooling pad 63 can include a recycle branch to collect and recirculate liquid which typically passes through it from top to bottom. Cooling pad 63 may also be connected to external heating sources or cooling sources (not shown in
Air which emerges from the cooling pad 63 enters the inner shell 25 which it is available to humidify and provide gentle and stable appropriate temperature air for any growing plant matter located within the inner shell 25. The air from the cooling pad 63 may be arranged for maximum circulation within the inner shell 25, including other circulating fans, such as ceiling fans and blowers, located within the inner shell 25. From inner shell 25, the air passes to and through exhaust fan 55 and back to the atmosphere 61. It may be preferable for inlet fan 53 to operate at a higher pressure rate than exhaust fan 55 so that the air within the outer shell 23 and inner shell 25 may be somewhat slightly pressurized.
Referring to
Not shown in
Explained, the exterior of inner shell 25 will have an even flow of brackish water or brine 73 over its exterior surface. Any energy input into the inner shell 25 will cause water to be vaporized. Vaporized water may condense on the inside of the outer shell 23 and run down the inside of the roof 33 and down the inside of wall 31. At the base of the walls 37 and 31, the clean condensed water from the inside of wall 31 would otherwise mix with the brackish water, or brine 73 flowing down from the outside of wall 37. The prevention of mixing of these two streams by segregating and conserving the pure condensed water provides a source of desalinated water. A barrier 81 separates the flow at the base of the walls 31 and 37 into a brackish water reservoir 83 and a fresh water reservoir 85. Brackish water reservoir 83 may have a lower drainage tap 87 and a fresh water reservoir 85 may have a drainage tap 89. Taps 87 and 89 will assist in harvesting and or recycling the brackish water 73 or the condensed water as needed.
Referring to
The panel 91 may be made of conventional greenhouse building material products such as plastic, polycarbonate, or any other material which is at least partially clear. The grooves 93 may be formed by molding or by matching or by other technique. An outer covering may be of lighter materials such as polyethylene for economics and for easy removal when cleaning of the roof 33 is needed. Air and water within the desalination greenhouse 21 may be uv-disinfected at any, and at many points in the system for to enable the use of an organic crop label for plants grown. Referring to
The use of a vortex system could be employed with the desalination greenhouse 21. Referring to
In general, the use of a vortex system could be employed with the desalination greenhouse 21. The cool air under positive pressure from the air blower 153 will eventually enters inner shell 25 through evaporation or cooling pads 63. Cooling pads 63 may be switched off by either being taken out of the path of flow or simply allowed to run dry, to remove its ability to cool inner shell 25 of desalination greenhouse 21 using cooled air from roof and side cavities 45 and 47. Conversely, cooling pads 63 may be switched on or into or out of the path of flow and with the brine distribution header pipe 71 used wetting roof 39 and side walls 37 of inner shell 25 of desalination greenhouse 21 with roof and side cavities 45 and 47 switched off or isolated from flow, in humid climates so that heating the air reduces its relative humidity and makes it effective in cooling inner section 24 of desalination greenhouse 21. Cool air then passes from roof and side cavities 45 and 47 into inner shell 25 of desalination greenhouse 21 to cool the growing crop, to enable the growing crop to transpire, supply oxygen and remove carbon dioxide and other gases. Air becomes warmer and more humid as it passed from one end of to the other of inner shell 25 of desalination greenhouse 21 due to the incident light and heat and transpiration of the crop in inner shell 25 of desalination greenhouse 21. Air may exit inner shell 25 of desalination greenhouse 21 through a heat exchanger (not shown in
Referring to
Heat exchanger 171 exit condensate is preferably collected through exit line 179 and is piped to an insulated underground cold water storage tank 181. A portion of the desalinated water is transferred by pipe 183 to an insulated underground irrigation tank 185 tank used as an irrigation reservoir. Well balanced fertilizers that include macro and micro nutrients required by the crops may be contained in a fertilizer tank 187 are dosed into the irrigation tank and are topped as the crop uses the fertilizers through a dosing line 189. One possible method of hydrating the plants may involve cold irrigation water is fed to the crop through piping that connects to soaker hoses laid in parallel under the crop. Excess irrigation water may be drained to the irrigation system tank 185 which is topped with fertilizers and desalinated water as needed.
Referring to
The growing trays 201, 203 may also extend along the same direction as a soaker hose 211. Soaker hoses 211 may extend along the length of the desalination greenhouse 21 and may be fed with cold water from fertilizer added irrigation system 185 seen in
In terms of overall process operations, the water for feeding crops is typically the desalinated water which originates at the inside surface of the outer shell 23 of the desalination greenhouse 21 resulting from evaporating of sprayed brackish water 73 using relatively hot air within roof and side cavities 45 and 47 and producing, condensation of inside of roof 33 and sides 31 of desalination greenhouse 21 resulting from evaporation of sprayed brackish water 73 onto the roof 39 and walls 37 of the inner shell 23 of the desalination greenhouse 21 and possibly from cooling pads 63 when operating and evapo-transpiration of the crop. Condensate from vertical walls 31 of the outer shell 23 are collected in a fresh water reservoir 85 which is preferably separated from a brackish water reservoir 83 such as by a barrier 81 as was shown in
In terms of process, and in further detail as to operation, air forced by inlet fans 53 are distributed evenly throughout the roof and side cavities 45 and 47. When this air is heated, it evaporates sea or brackish water 73 on the exterior surface of the inner shell 25. Downward flow of brackish water 73 is delayed by grooves 93, 103 or 113 of panel 91, 101, 111 which make up the roof 39 and side outer surfaces of vertical walls 37, except for doors 59 and vents associated with the inlet and exit fans 53 and 55. Transparent roof 33 of outer shell 23 of the desalination greenhouse 21 preferably passes maximum light and heat to roof and side cavities 45 and 47. Roof 39 and vertical sides 37 of inner shell 25 of desalination greenhouse 21 is wetted with a thin sheet of brackish water 73, of about two centimeters or less thick, fed from a source of sea or brackish water 73 from brine distribution header pipe 71 by a low pressure pump and spread evenly as guided by grooves 93, 103 or 113 of panel 91, 101, 111. Cool air from to roof and side cavities 45 and 47 produced by hot air giving up its heat to vaporize water, especially where brackish water 73 is heated in a black lining sun exposed section of the outer section of the desalination greenhouse 21. As inlet air is heated its relative humidity drops. It then passes through the cooling pads 63 where it may pick up more moisture and cools the inner shell 25 of desalination greenhouse 21. Brackish water 73 on the roof 39 of inner shell of desalination greenhouse 21 is cooled through evaporation and transmits this cooling effect through panel 91, 101, 113 to the inner shell 23 of desalination greenhouse 21 to aid in the cooling of the crop environment and condensation of moisture on the inside of the outer section 23 of the desalination greenhouse 21. Cool air is blown into inner chamber 43 through the cooling pads 61.
When roof 39 of the inner shell 25 is not wetted, as in winter when crop water requirement and cooling are not required, hot air passes through water soaked cooling pads 61 to pick up moisture to produce cool air within inner chamber 43 and to produce cold water where a coil is provided in the cooling pad 61. Cool air will then exit evaporative cooling pads 61 into the inner chamber 43 of the inner section 25 of the desalination greenhouse 21 to cool growing crops and then exit through exhaust fans 55 which operate at lower pressure than forced air fans 53 to maintain positive pressure in both the inner chamber 43 and the roof and side cavities 45 and 47. In the alternative, exhaust fans 55 can be minimized or eliminated with certain designs, particularly a passive exit where overall pressure and air flow in the desalination greenhouse 21 is maintained high.
The forage crop production system in the desalination greenhouse 21 is and can be a 24/7 production system. A quantity of the seeds, depending on the size of the growing tray 201, may be soaked in disinfected water for 24 hours, then drained and covered to germinate in a pail or other container. The seeds may be irrigated with mist nutrient twice a day. Within 3-4 days the germinated seed may be spread in a growing box such as growing tray 201 and placed on a conveyer belt or rollers. The growing trays 201 may be stacked 4-6 high to utilize the inner chamber 43 of the desalination greenhouse 21 effectively. The growing trays 201 may have openings 207 on the sides for light, ventilation and irrigation. The growing trays 201 may be irrigated with a mist of nutrient rich desalinated water. A conveyor built/roller (not shown) can be operated daily to move ⅛ to 1/10 the distance per day so that a crop has an automated harvest indication each day after it has been on this type of moving belt for 8 to 10 days.
The crop, including the roots, may be tipped from the growing tray 201 and into a tub grinder which may cut or otherwise process the crop and feeds it into a wagon or conveyance to be transported fresh to its needed consumption point, such as to a grazing animals for feeding. A typical desalination greenhouse if 1000 square meters area, producing 4 tons of barley forage per day. It will use 50 cubic meters of sea or brackish water per day compared to 10,000 cubic meters per day in field production of sweet water. The energy requirement is 96 KWH per day for the fans. Conventional Reverse Osmosis desalination alone will require 200-400 KWH per day.
Controls of the desalination greenhouse 21, not shown, may be used to control the equipment set forth and other equipment. Equipment controlled includes ventilation, evaporative cooling, spraying and use of both fresh and brackish water, irrigation, vortex device 161 operation, warning systems, pumps and other functions. The advantages of desalination greenhouse 21 are to desalinate brackish water 73 for potable and agricultural use and insulation property of two preferably transparent bodies, as the bulk of the internal and external shells 25 and 23, with air in between within roof and side cavities 45 and 47 which enables a level of control and combine to save major running expenses compared to conventional greenhouse operation. The brine distribution header pipe 71 sprinkling system within the roof and side cavities 45 and 47 creates a sheet of water on the roof 39 and vertical walls 37 of inner shell 25 of desalination greenhouse 21 further insulating it without obstructing light transmission and while cooling inner chamber 43 of desalination greenhouse 21. The superior properties of water to absorb heat to the extent of 540+ calories per cubic centimeter (cc) when evaporating is an effective cooling mechanism in summer while the outer shell 23 of desalination greenhouse 21 insulates it from cold and snow in winter. Such arrangement exemplified in the desalination greenhouse 21 saves energy and is environmentally friendly.
Another advantage of desalination greenhouse 21 is the use of the crop growing structure of inner shell 25 of desalination greenhouse 21 as a support structure for the cover of inner shell 25 of desalination greenhouse 21. Cooling of crop roots using soaker hoses 211 is another advantage of desalination greenhouse 21 for the crop shoots to be enabled to tolerate higher temperatures in their potentially high temperature growing environment. An additional advantage of desalination greenhouse 21 is the ability for sterilization of the air through heat and ultraviolet treatment which enables desalination greenhouse 21 to grow organic crops and reduce insecticide use. A further advantage of desalination greenhouse 21 is use of natural lighting while providing a general thermal insulated inner section 25 of desalination greenhouse 21.
Another advantage of desalination greenhouse 21 is the heating of air for use for effective evaporative cooling where it would otherwise be ineffective in humid areas. A further advantage of the desalination greenhouse 21 is the flexibility and efficiency of using many features independently, especially heating and cooling which contributes to an overall cost reduction. A further advantage of the desalination greenhouse 21 is the use of renewable energy for some or all of its operations. The aforementioned advantages makes the desalination greenhouse 21 simple to operate and competitive especially in developing countries where fuel is expensive and potable water may not be available.
While the present invention has been described in terms of a desalination greenhouse 21 and components which can be used with control to affect (1) fresh water production, (2) quick crop growing times, (3) combination summer and winter operating configurations, the construction and process operation of a desalination greenhouse within the teaching above can be used to make a wide variety of alternate variations thereof.
Although the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention. Therefore, included within the patent warranted herein are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.
