METHOD AND PLANTER TO PROVIDE CONTINUOUS AERATION AS WELL AS HEAT OR COLD

TRANSFER TO PLANT ROOTS

Description:

There is no prior art method as well as an apparatus/planter/container to grow plants that combines the advantages of enhanced natural aeration to plant's root zone from underneath a soil or substrate contained in such planter, provide energy efficient insulation to root zone against heat or cold and its design having features to save the irrigation water and nutrients from being drained to waste.

Background to the invention

Normally the prior art planters are used in outdoor or indoor gardening and commercial growing in a glasshouse, poly-tunnel and open land farming. Majority are moulded from plastic material, which is used to hold soil or substrate to grow various plants. They play an important role from naturally preventing pathogen spread from one planter to another especially in a drain to waste irrigation system. They also assist in easier handling of protected crops grown in glasshouse or poly-tunnel and to some varieties of crop in open land farming. They are designed to have drainage holes in their bottom to allow for drainage of water. If not for these drainage holes the resulting water logging within the planter will have detrimental effect on the plant's root development. One of the main reasons for this problem is lack of continuous aeration to root zone. This is important for vigorous root development and a water logged planter does not allow free passage for aeration. However the downside to drainage holes in a planter is the loss of irrigation water and nutrients which is drained to waste due to gravitational force. It is estimated that more than 30 percent of irrigation water and nutrient are drained to waste due to this reason.

Another requirement for a better root development in plants is the temperature in the root zone, which needs to be favourable and consistent throughout the growing season. The plastic planters are normally manufactured with thin wall sections. This may be due to the high cost of plastic material. Furthermore, the plastic material used in planters have low 'R' value and thereby low insulating properties which do not provide adequate insulation to the plant roots against outside heat and cold. This will have a detrimental effect on root development during hot and cold seasons where plants are grown outdoors as well as in a climate protected greenhouse. The following description particularly focuses on issues in growing protected crops with or without planters/containers in a greenhouse and sums up the reasons for invention.

Growing protected crops in greenhouse

Plants are grown within a protected environment for various reasons i.e. climate protection, quality of product and season extension. The protection would be provided via glasshouse or poly-tunnels (both termed as glasshouse or greenhouse).

For the purpose of understanding energy efficiency and environment protection in greenhouses around the world, the greenhouses can be divided into three main categories. The first category is heated and cooled greenhouses. The second category is either heated or cooled. The third category is the greenhouse without heating or cooling facility, which is used either to grow protected crop for a limited period in a year between Spring and Fall (especially in cold regions) or used as climate protection to grow crops throughout the year in tropical or temperate regions.

Examples of protected crops grown in greenhouses are vegetables (tomato, cucumber, capsicum, aubergine etc) soft fruits (strawberries, cherries, Raspberries etc), salad leaves, herbs, medicinal plants, cut flowers, ornamental and bedding plants. In cold climatic conditions, a greenhouse requires heating to grow these crops throughout the year. In hot climatic conditions, a greenhouse requires cooling when the temperature inside the greenhouse rises above certain limit due to solar radiation which is detrimental to plant growth.

Generally greenhouses in cold climate regions require more heating and less cooling whereas in hot and tropical climatic regions greenhouses require more cooling and less or no heating to grow protected crops throughout the year.

Carbon Footprint in greenhouse

The carbon footprint is a serious issue in growing protected crops especially in heated and cooled greenhouses. Burning of fossil fuels to heat the greenhouse in cold climates generates tremendous carbon footprint and the energy required to cool the greenhouse in hot climates also generates carbon footprint.

Carbon footprint due to food miles

In some regions experiencing extreme and/or longer periods of cold and hot climatic conditions growing locally in greenhouses are abandoned due to high energy costs to heat or cool the greenhouses. Instead the local market demand for vegetables, fruits, flowers etc. is met by imports. This generates carbon foot print in the form of food miles although it may be debated that the carbon footprint impact is lesser in such food miles compared to burning fossil fuel to heat or cool the greenhouse under such climatic conditions.

Carbon footprint from the use of pesticides

Use of pesticides generates carbon footprint. A soil-less or a soil based culture in a protected greenhouse environment has proven to reduce the use of pesticides, which is otherwise required in soil cultivation in the open. Hence there is a large scope to reduce the use of pesticides by changing over from soil based cultivation in the open to growing crops under protection in a greenhouse.

Water footprint

Scarcity of irrigation water is a major issue. Wastage due to draining of irrigated water and evaporation of irrigation water into the atmosphere largely contribute to increasing water footprint. Any possibilities of saving the irrigation water from being drained to waste and growing protected crops in greenhouse to prevent unnecessary evaporation would considerably reduce water footprint. Nutrient pollution

Especially in greenhouses adopted to the drain to waste system a large amount of nutrients along with irrigation water is also drained to waste. This causes multiple problems to the growers because on one hand the grower wastes costly nutrients and on the other hand it results in nutrient pollution to land and water resources.

Current problems with the conventional growing of protected crops in a commercial greenhouse

It is a requirement to maintain an optimum root zone temperature in a greenhouse to successfully propagate and grow a protected crop. Typical greenhouses used to grow protected crops suffer from a large - and unnecessary - carbon footprint and several other inefficiencies.

In particular:

The heating or cooling of overall volume of air in a greenhouse in cold or hot climatic conditions (with absolutely no insulation to its walls and roof) to heat or cool the plant root zone and plant surroundings implies significant wastage of energy.

Currently available systems to cool the root zone in order to protect the plants from the heat during hot climatic conditions (which is normally worsened in a greenhouse due to solar radiation) are not efficient and cost effective for large commercial growing.

Separate irrigation systems administering cold water to the root zone normally with temperature much lower than the Greenhouse air temperature make it difficult to maintain accurate and uniform temperature within the root zone throughout a greenhouse which is conventionally heated by indirect radiation methods i.e. heating the root zone via heating air, heating the floor or beds by running hot water in pipes and forced hot air circulation under the bed.

There are no cost effective plant propagating and growing system that can maximise supply of oxygen via natural aeration to the plant roots. Maximised oxygen delivery will ensure optimal quality and quantity in yield.

Root zone temperature and its effects

It has been established by many lab trials, researches conducted by universities and research centres around the world that an accurate control and maintenance of plant root zone temperature at optimum levels gives: optimum yield, shortest possible propagation, ability to bring forward or extend harvest and an efficient means to balance vegetative and generative growth by manipulating Day/Night temperature (DIF) in majority types of protected crops. The typical optimum root zone temperatures required (ranging between 65° F to 79° F) has been found to vary between the plant species, stages during a growing cycle and the vegetative and generative growth.

Heating air in greenhouse during cold climatic conditions

In cold climatic conditions, the commercial greenhouses are either heated by steam boilers or from the waste heat from CHP (Combined Heat & Power) generators to maintain the entire volume of air at a certain temperature which in turn would transfer heat to the root zone. This conventional method of indirect heat transfer to the root zone generally fails to raise the temperature of the root zone to its optimum temperature levels and to maintain it uniformly throughout a greenhouse from a commercial large scale growing perspective. It has neither been economically viable nor technically sensible (in commercial scale context) to raise the root zone temperature to such established optimum levels during the day or night by indirect method of heat transfer to the root zone from heated air. This is because of

High energy costs associated with increased C0 ₂ emissions.

Natural constraints (which are explained below) in controlling and maintaining optimum root zone temperature (ranging between 65° F to 79° F) by indirect method of heat transfer which makes it more difficult with a separate irrigation system administering much colder water (typically 52° F or less) to the root zone.

Non existing cost effective system or technology for use in a commercial scale to meet the increased demand of oxygen by the plant roots at optimum root zone temperatures.

The indirect method of heat transfer to the root zone from the heated air is not energy efficient because most of the heat in air is lost before it reaches the root zone. This is due to constant loss of heat in air resulting from lack of insulation to greenhouse walls and roof, frequent ventilation and leaks through openings in a greenhouse structure.

Dissolved oxygen in the irrigation water reduces with the increase in its temperature and for this purpose irrigation water of lower temperature (typically 52° F) is administered to the plant roots in a separate irrigation system. It is found that the dissolved level of oxygen is at optimum level when the irrigation water is at 52° F and begins to deplete with the increase in temperature from this point. Therefore it is technically not a sensible idea to increase the root zone temperature to their established optimum levels unless there is a means to increase the oxygen supply. Hence the current methods of heating greenhouse on a commercial scale generally may limit the yield, extend the duration of growing cycle and make it almost impossible to manipulate root zone temperatures to control plant vegetative and generative growth.

Supplementary heating to the root zone in cold climatic conditions

In some greenhouses, further indirect radiation heating methods like under floor heating or heating near root zone as supplement heating by means of circulating hot water in pipes or forced hot air are employed. These methods of indirect heat transfer to the root zone is known to reduce the overall energy demand and help to maintain a more constant root zone temperature. However, they are permanent installations and provide less flexibility and in many instances are not practical to install. It does not improve the situation either with oxygen supply or with the much needed accurate control and maintaining of uniform temperature in the root zone throughout the greenhouse.

Direct heat transfer to the root zone in existing Hydroponic soil-less growing systems

NFT (Nutrient Film Technology) and DWC (Deep Water Culture) which are popular Hydroponic systems can provide direct heat or cold transfer to the root zone and possibly a better uniformity to the root zone temperature throughout the greenhouse (especially in DWC). However, these systems depend heavily on the levels of dissolved oxygen in the feed to prevent plants from wilting. Heating the feed beyond 52° F will deplete the level of dissolved oxygen in the feed hence these systems have increased application as a direct cold transfer system to the root zone in hot climates. However, the scope for these systems is limited because only few types of protected crops are successfully grown in these systems. It is a general opinion that majority types of the protected crops grow better on substrate having good air retention ability than on NFT or DWC systems.

Demand for increased Oxygen supply at optimal root zone temperature

The oxygen demand from plant roots increases with the increase of temperature in the root zone. This further emphasises that plant roots cannot entirely depend on the dissolved oxygen levels in the irrigation water if they are to be maintained at optimum temperature. The indirect radiation heating can neither provide increased supply of oxygen nor make it possible to maintain accurate and uniform optimum temperature in the root zone throughout a greenhouse. Hence there is a good scope to increase the quality and the quantity of the yield if there is a cost effective means available to rise the root zone temperature to optimum levels and maintain it accurately and uniformly throughout a commercial greenhouse with increased supply of oxygen to the root zone.

Energy saving by maintaining higher roots zone temperature & lower air temperature in greenhouse

Among many trials and studies conducted worldwide, and more particularly the one published by NCAT - National Centre for Appropriate Technology, USA, which maintains Natural Sustainable Agriculture Information Service also known as the ATTRA project - in April 2002 by Steve Diver - Root Zone Heating for Greenhouse Crops - provides sufficient evidence that almost 50% of the energy traditionally used to heat greenhouses growing protected crops in cold climates can be saved by maintaining comparatively higher plant root zone temperature (> 72°F) and lower air temperatures (<52°F) in a greenhouse. However, the constraints in raising the temperature in the root zone and maintaining it accurately and uniformly throughout the greenhouse on a commercial scale with the available technology has prevented growers to benefit from this proven concept. AHT (Aeration & Heat Transfer) Technology - the preferred embodiment

It is an invented method as well as an apparatus/planter for direct heating or cooling plant's root zone which is beneficial when used in greenhouses and open cultivation. Unlike prior art apparatus/planter it is designed to provide natural aeration from underneath the soil or substrate contained in apparatus/planter simultaneously with direct heat or cold transfer to the plant roots. An additional advantage is the design and features which make it possible to save water and nutrients which is otherwise drained to waste. The apparatus/planter with inventive engineering features is moulded in Expanded Polystyrene (EPS or EPP) material. This material is specifically chosen for its good insulating property, which protects the roots from outside heat or cold and retains the heat or chillness of the administered irrigation water within the apparatus/planter making it energy efficient.

AHT overcomes all constraints of raising the root zone temperature to optimum levels in a greenhouse

The preferred embodiment overcomes all the constraints of traditional methods of heating to raise the root zone temperature to optimum levels. It provides the plant roots growing in soil or in any substrate (sawdust, Rockwool, Stone wool, coco fibre, Clay pebbles, Perlite etc) with natural aeration simultaneously with direct heat or cold transfer combined with saving of water and nutrients which is otherwise drained to waste. It is a Thermodynamics principle which is engineered to work within a planter moulded to any shape, size and can be custom made to hold a plant or a number of plants.

Engineering of AHT

The preferred embodiment is designed to retain some volume of administered irrigation water at the bottom before it overflows through a return. Also designed are openings from underneath on its body supplemented with channels converging on to such openings to allow unobstructed air passage into the preferred embodiment when substrate or soil is loosely filled into the preferred embodiment or packed in a grow bag, plastic envelope, netted bag etc and placed into the preferred embodiment. This is engineered in a way to prevent the retained or overflowing irrigation water clogging or leaking through the openings of air passages allowing unobstructed passage to incoming air.

Concept of AHT technology, its energy efficiency, increased oxygen supply and optimum feed to the root zone in cold climate

Energy efficiency in preferred embodiment results from the combination of material used in manufacturing preferred embodiment, substrates or soil and the externally heated irrigation water or water mixed with nutrient (feed). The feed is heated to a desired temperature and administered into the preferred embodiment via irrigation pipes. When the heated feed is administered into the preferred embodiment, some volume of the feed is retained in the bottom before it overflows through a return. Unnecessary heat loss from the retained feed is prevented from the natural insulation provided by the substrate or the soil covering the retained feed (reservoir) from above and the body of the preferred embodiment which is made from the material having good insulation property, for example Expanded Polystyrene (EPS or EPP) material covering the sides and the bottom of the retained feed. Furthermore, it is recommended to insulate the irrigation pipes as well as heating and storing tanks in order to prevent the heat loss from the heated feed.

When the heated feed is administered into the preferred embodiment, the volume of the retained feed at the bottom will effectively create a zone which is warmer than the temperature outside preferred embodiment. The retained warm feed is pushed upwards to the root zone by capillary force which occurs naturally due to the porosity in the substrate material or the soil which is fully or partially connected to the reservoir and the additional suction force of the roots absorbing the feed. The combination of all these factors result in heat transfer to the level in the soil or substrate which is immediately above the retained feed and warm up the air which is present in their void spaces due to infusion of air into liquid medium assisted by conduction, convection and radiation. The warmed up air will start moving leaving a vacuum behind. The vacuum attracts comparatively cooler air from outside through the openings for air passage. The cool air when reaching the vacuum zone gets warmer and the cycle repeats. This becomes a constant phenomenon within the preferred embodiment as long as there is a temperature difference between the outside and the inside of the preferred embodiment.

The preferred embodiment now works like an under floor heating system with an added advantage of direct heat transfer and additional aeration while providing optimum feed to the root zone. It heats the roots first to the desired optimum temperature followed by keeping immediate plant surroundings warm. It may not require supplementary heating of the air in a greenhouse during most periods of the cold climatic conditions or may only require air temperature in the greenhouse maintained as low as 52° F (as recommended by NCAT-ATTRA) as opposed to the air temperature maintained >72°F in the greenhouse which saves considerable energy. Also the loss of energy due to the loss of heat from the air resulting from the lack of insulation to the greenhouse walls and roof, ventilation and leak in the greenhouse structure that carry away useful heat is significantly minimised making it a highly energy efficient method of heating the root zone in a greenhouse.

The feed itself is a supplementary source of heat which is protected against the heat loss with adequate insulation. This makes it possible to maintain near accurate temperature in the root zone uniformly throughout the greenhouse and makes it possible to control the root zone temperature as required during a growing cycle. Depletion of oxygen in the heated feed does not pose a problem due to constant aeration provided to the root zone from underneath of soil or substrate resulting in optimal quality and quantity in yield.

Calculating energy efficiency of AHT compared to traditionally heated greenhouse

The energy efficiency of the preferred embodiment in cold climate is demonstrated by comparing the BTU (British Thermal Units) / hour energy consumed in a traditionally heated greenhouse with the greenhouse installed with the preferred embodiment by using the formula BTU/Hour = A* ΔΤ/R where A= Square feet Area of the greenhouse roof and walls, ΔΤ = Temperature difference in °F between inside and outside of the greenhouse and R = the R value of the materials providing insulation i.e. Glass (Glasshouse), polythene sheet (Poly tunnel), Rockwool or Stone wool substrate slabs, Expanded Polystyrene (Body of preferred embodiment) and Elastomeric pipe insulation.

For example, a traditionally heated greenhouse measuring 30 feet wide X 100 feet long X 12 feet eaves height, gives a wall and roof surface area A = Walls = {(2 x 30 x 12) + (2 x 100 x 12)} + Roof = {{2 x 100 x 8) + (2 x 30 x 6 12)} where 8 is the approximate length from the roof ridge to eaves and 6 is perpendicular height from the roof ridge to eaves = 4900 square feet. This excludes floor surface area of 3000 square feet (30 x 100). The ΔΤ is assumed as 40°F (i.e. temperature inside 72 °F minus outside 32 °F) and the glass or polythene sheet R value is 0.88. This gives a BTU/Hour = 222,727. If the air temperature in the greenhouse is reduced to 52°F, the corresponding ΔΤ is reduced to 20°F. This gives a BTU/ Hour = 111,363.

For example Tomatoes are grown in compressed slabs of Rockwool or Stone wool substrate. Generally 384 units of slabs each measuring 1000 mm long (3.30 feet) X 200 mm wide ( 0.67 feet) X 100 mm high 0.33 feet) would fit into the 3000 square feet floor surface area of the above example greenhouse. The surface area (excluding the bottom) of each slab is approximately 6 square feet. The planter holding them would measure approximately 7 square feet (excluding the top but including the bottom).

Compare this to the greenhouse of similar size and air temperature maintained at 52°F (as recommended by NCAT if the root zone is maintained greater than 72°F) which is installed with preferred embodiment. The Area (384 units of preferred embodiment X 7 square feet + surface area of insulated irrigation pipes) = (2688 + 1012) = 3700 square feet. The ΔΤ is 20°F and the R value of 25 mm thick Expanded Polystyrene (body of the preferred embodiment) and 100 mm thick substrate (Rockwool, clay pebble etc) and 25mm thick Elastomeric pipe insulation is an average 11. This gives a BTU / Hour = 6,727 (which is only 3% of traditional consumption if the air does not require to be heated for example, growing short plants) and a total BTU / Hour (111,363 + 6,727) = 118,090.

This is 53 % of currently consumed BTU/Hour in a conventionally heated greenhouse to achieve similar if not a better quality and quantity yield. Additionally, there is loss of heat in a conventionally heated greenhouse because of increase in ventilation due to increase in air temperature. Further heat loss will normally result from the leaks in the structure of the greenhouse. If these heat losses are taken into account, a greenhouse would save more than 50% on currently consumed BTU/Hour energy by installing preferred embodiment.

Benefits of AHT in hot climatic conditions

In hot climates, administering chilled feed into the preferred embodiment keeps the root zone cooler than outside. It is already been established that the plants would withstand higher temperatures in a greenhouse especially during hot climatic conditions if the root zone is maintained at cooler temperature.

AHT works like a under floor cooling system with an added advantage of direct cold transfer, additional aeration and optimum feed to the root zone. It cools the roots first followed by cooling immediate plant surroundings and protects the plants even if the air temperature in a greenhouse has to increase beyond tolerant levels due to solar radiation. Insulation to the irrigation pipes carrying chilled feed and the natural insulation provided by the expanded polystyrene (EPS or EPP) material makes it possible to maintain the chill temperature in the root zone accurately and uniformly throughout the greenhouse. This makes it a highly effective and energy efficient technology for the purpose of protecting the plants in greenhouse during hot climatic conditions.

Saving water, nutrients and prevention of nutrient pollution in AHT

Water efficiency in the preferred embodiment is due to the possibility to save irrigation water and nutrients which is otherwise drained to waste. The irrigated water that drains out due to gravitational force in prior art is instead collected as a shallow reservoir at the bottom of the preferred embodiment before it overflows through an outlet. This provides additional buffer to plant roots. The continuous aeration above the surface of the reservoir unlike prior art overcomes negative effects of any water logging and provides ideal condition for vigorous root development despite the presence of water reservoir.

The substrate or soil may be loosely filled or the substrate which is packed in a grow bag, plastic envelope, netted bag etc is placed inside the preferred embodiment after making provision for partial contact between the underneath of the substrate and the reservoir.

Manipulation of Vegetative and Generative growth in AHT

The possibilities in the preferred embodiment to control the temperature in the root zone and keeping it uniform throughout a greenhouse allows the grower to manipulate day and night temperature difference (DIF) and therefore the vegetative and generative growth more efficiently.

Major problem solved by AHT

Reduces major problem of growing food shortage in the world due to growing population and hurdles in distribution by providing a cost effective, water and energy efficient means to grow fresh produce locally throughout the year under hot or cold climates with an improved quality and quantity in yield.

CONCLUSION

AHT (Aeration & Heat Transfer) - is a new, highly cost effective and necessity based technology beneficial to grow protected crops in greenhouses, open cultivation, indoor and outdoor gardening.

It helps to improve the quality and the quantity of the yield by making it possible for the grower to have a better control on the plant root zone temperature and to manipulate vegetative and generative growth throughout the year under cold or hot climates using only a smaller fraction of energy and water that is being traditionally consumed. Description of drawings:

FIG 1:

A three dimensional view of the preferred embodiment in rectangular shape where (33 ) is the insulating wall of sufficient thickness, (34) is one of the several exit outlet for incoming air, (35) is the channel converging on to the exit outlet hole for incoming air (34), (36) is the reservoir tank and

(37) the overflow outlet for the reservoir.

FIG 2:

Is the top view of FIG 1. FIG 3:

(38) is a smaller block of a substrate for example stone wool or coco fibre used in this case to partially connect the underneath of the main substrate to the reservoir.

FIG 4:

Is the side view of the FIG 3 where (38) is in level with (34), (39) is the 'U' grove formed as a result of (35) converging on to (34) and (40) is one of the several air inlet passage located in the bottom of the preferred embodiment.

FIG 5:

Shows the water reservoir (41) formed from the water flowing down the main substrate (43) due to gravitational force. (42) is the space filled with incoming air. The main substrate (43) for example stone wool or coco fibre packed in a plastic envelope (44) which has openings (45) on its surface for planting and openings (46) underneath to allow aeration as well as water and nutrient uptake from the reservoir via (38) via capillary and root suction force. (47) Shows the area covered by (45) which allows the unobstructed passage for incoming air via 'LT grove but prevent the water in the main substrate clogging or leaking through (34). (48) is the surface of (38) where the incoming air mixes together with the water from the reservoir and assist in aeration to root zone.

FIG 6:

Shows a loosely filled substrate or soil (49). (50) is a separate non permeable material which caps (34). This allows the unobstructed passage for incoming air via 'U' grove but prevent the water in the main substrate clogging or leaking through (34). (51) is the mix of (49) and (41).

FIG 7:

Is the top view of a section showing the separate non permeable material (50) capping (34) and the unobstructed passage for incoming air (52). FIG 8:

Shows loose clay pebbles used as substrate in the preferred embodiment. FIG 9:

Shows a thin liner made of non permeable material for example plastic which snugly fits into the inner contour of the preferred embodiment and having holes (53) that align with all the holes in the preferred embodiment.

FIG 10:

Shows the top view of FIG 9. FIG 11:

Shows the preferred embodiment in the shape of a heart. FIG 12:

Shows the preferred embodiment in the shape of a square. FIG 13:

Shows the insulated main irrigation pipe (54) which carries either warm or chilled water or nutrient feed. (55) is the insulated branch pipe feeding into a substrate for example stone wool, coco fibre, saw dust etc (56). (57) is the preferred embodiment body providing insulation to the water held in (56) as well as water reservoir (58) from sides and bottom. The substrate (56) provides insulation to (58) from above and prevents evaporation from reservoir. The insulation to irrigation pipes enhances energy efficiency. The warm or chilled water reservoir heats or cools the incoming air (60) and maintains the entire main substrate (56) at a constant predetermined temperature for longer duration making it energy efficient. The temperature outside the preferred embodiment will have lesser impact on the temperature inside preferred embodiment due to overall insulation. There will be continuous air movement within the preferred embodiment as long as there is a temperature difference between inside and outside the preferred embodiment.

FIG 14:

Shows the method working similar to FIG 13 when the preferred embodiment is loosely filled with substrate or soil. Where (62) is the stone wool or coco fibre block normally used in loosely filled medium to support initial development of plant roots before it establishes into the main substrate or soil, (63) is the separate non impermeable material covering (34) and (64) is the unobstructed passage for the incoming air.