Agro Resilience Kit Ltd.
ARK Cooling System - Our Passive Cooling system utilizes evaporation to cool down any grow space.
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Our patented technology uses about 5% of the amount of electricity then a swamp cooler in the same size greenhouse. Source McGill thesis
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The ARK Cooling system uses 50% water as compared to a pad and fan cooling system making our system more efficient in terms of water use efficiency. A swamp cooler can use 10 gallons of water per hour with no water recovery
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Temperatures in a grow room can be reduced by 6°C - 20°C (3.4°F - 22°F) below ambient outside air
Simple
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Effective
How it works...
Agro Resilience Kit Ltd. (ARK) is an aggregation of proven technologies working together to offer a comprehensive solution set for advancing greenhouse growing through state-of-the-art structures, energy efficiency, vertical grow structures, lighting, aquaponics and more, to achieve unparalleled productivity, low capital cost, low operating cost and sustainable, resilient operations.
Unparalleled Structure
Sprung utilizes an extruded military grade aluminum substructure which provides superior performance, durability, and longevity. The Sprung aluminum substructure has an indefinite life expectancy and comes with a 50-year pro-rata guarantee. Our one-piece extruded aluminum I-beam with membrane retainer is engineered to endure extreme weather and environmental conditions. And for locating on an existing rooftop aluminum and tensioned fabric provides durability while being among the lightest of materials available so as to minimize likelihood of needing structural upgrades on an existing roof structure subject to a structural engineers report.
Performance Architectural Membrane
Sprung’s performance architectural membrane is not only as tough, durable and color fast as conventional building materials, it offers real cost advantages, through energy efficiency, climate control and quicker build times.
For Greenhouse Installations
Highly Translucent Greenhouse Membrane
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Membrane specifically designed for Greenhouses
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Ideal light transmission while diffusion eliminates shadowing
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Weighs approximately 24 oz. per square yard
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Natural cleaned with rainwater
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10-year pro-rata Guarantee
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Safe —The exterior architectural membrane is fire resistant and extremely durable. Designed to endure any climate imaginable; from -60°F (-51°C) to 122°F (+50°C). All our membranes are created with a high-strength rip stop design.
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Energy efficient—The architectural membrane creates a natural vapor barrier and improves the building’s R-value with virtually no dead air space. A blackout layer prevents solar gain and helps manage climate control. Our daylight membrane option provides an abundance of natural light, reducing lighting costs.
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Attractive —Our selection of finishes eliminates the need to refinish exterior or interior walls. Our membranes can be printed to match any style or design, create a unique look or support branding. Click Here for more information.
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Cost effective—The membrane is installed much quicker than conventional building envelopes, reducing build cost and down time, getting you up and running much faster.
As solar heat in the form of light enters the greenhouse, objects absorb it and reradiate into the greenhouse environment (the greenhouse effect). The more airtight the greenhouse the less cooling loss impact of wind. Conventional greenhouse structures typically see their cooling requirements double as wind speed goes from 0 to 15 miles per hour.
Those with the lowest capital and operating costs always enjoy a competitive advantage. Negawatts or energy an operator doesn’t need to purchase, whereas his competition does, has always been a source of improved margins and advantage. For greenhouses, such an advantage has been proven for decades, to be available, for those who take advantage of it. In some parts of the world, in commercial greenhouses, passive solar negawatt techniques have been used in almost all commercial greenhouses and in other parts of the world, like North America, it is misunderstood and mostly underleveraged. Books, studies and so forth have been written about passive solar greenhouses or climate batteries since at least the 1970’s but really mankind has been leveraging such techniques for much longer than that.
Cooling:
The oldest methods of greenhouse cooling include swamp coolers and shading involving the application of semi-opaque materials to glazing either as unresponsive liquid coatings or in the form of fabric screens. The fabric screens are often fragile with short life spans. The ARK Sprung cooling system offers a long-life option that has been field tested with proven measured performance showing not only capable of cooling below ambient temperatures but also with only 5% of the electricity use of swamp coolers and only 50% of the water consumption. Our system enables us to cool from side to side as opposed to end to end.
Swamp cooler or pad and fan greenhouses have been in use for a long time. Most fruiting plants are prone to reduced quality and yield at maximum temperatures of more than 30 degrees Celsius. The cause often is a reduced viability of pollen and issues transpiring and as a result, the fruit will be soft, dull, misshapen, and smaller in size.
As fruit and vegetable production in greenhouses gained popularity, growers in hot climates resorted to pad and fan greenhouses. The evaporation of water can reduce the air temperature significantly. Everyone experiences the evaporative cooling power of water, after a swim, when you leave the water and a mild breeze starts evaporating the water droplets on your body. It feels warmer to be under the water where no evaporation takes place.
Figure 1 shows how awesome this power is. The psychometric chart graphs what temperature can be achieved through evaporative cooling based on the temperature and humidity of the outside air. Follow the dark blue line at the bottom of the graph that points upward at 45 degrees Celsius. By evaporating the maximum amount of water in air containing 10% humidity, the temperature can be reduced to 22 Celsius (follow the diagonal line to the left). The other two examples show air at 45 degrees with a humidity of 20% and 30% respectively. The corresponding coolest air temperature that can be achieved is 25 and 27 degrees.
Fig 1 Psychometric Chart
Both pad and fan and the semi-closed glasshouse use this cooling technique by using a fan to force air over a cooling pad from one end of the greenhouse to the other.
Fig 2 Pad and Fan Greenhouse
In a pad and fan glasshouse, the fan sucks the warm air out of the glasshouse, creating a flow of air over the cooling pad (see figure 2). In the case of the example above, if the outside temperature is 45 Celsius and the humidity is 10%, the cooling pad can cool the air to 22 Celsius at 100% humidity (this depends on fan speed and thickness of the pad wall). As the cooled air passes through the glasshouse, the sun warms up the air creating a temperature difference between the pad side and the fan side of the glasshouse.
It is not unusual to experience a temperature difference of 6 degrees (or more) Celsius. This complicates growing high yielding crops because maintaining correct and uniform temperatures is one of the main drivers to achieve this. It also complicates the irrigation management as plants in a high temperature area with lower humidity require more irrigation.
The warming up of the air can only be restricted by reducing the distance between the pad and the fan. Generally, a maximum distance of 40 meters is accepted. This reduces the size of the greenhouse. Moving more air also reduces the problem, but a pad and fan greenhouse already moves significantly more air than a semi-closed glasshouse. Figure 3 shows a comparison between the air exchanges of different glasshouse types.
Fig 3 Air Exchange in Different Types of Glasshouse
Both pad and fan and semi-closed greenhouses can maintain a cool climate inside independent of outside wind speed. Therefore, in the table above a wind speed must be mentioned to represent the air exchange for a conventional greenhouse. Pad and fan glasshouses move a considerable amount of air. This is expensive from a cost perspective and reduces the benefit of CO2. The large volume of air makes it impossible to screen the air inlet for small insects. The larger amount of ventilation capacity allows the pad and fan glasshouse to maintain cooler temperatures when the weather is hot, and radiation is high.
It is not difficult to see that a semi-closed greenhouse achieves a much more even climate as it distributes the air evenly through the greenhouse from side to side. The average size of new glasshouses is 5 to 10 Hectares. The size restriction imposed by the distance between pad and fan increasingly causes growers in warmer climates to opt for semi-closed glasshouses.
When temperatures get outside of productive growing ranges for crops, it is critical to maintain greenhouse temperatures at the desirable level, as few crops prosper in excessively hot temperatures. Over the years, several methods have been developed to keep greenhouses cooler, such as evaporative cooling, but greenhouse design has also evolved to incorporate passive ventilation more effectively. Ideally, growers will use a combination of passive and active ventilation to create the optimal growing environment. A balanced approach that uses both passive and active ventilation can keep both temperatures and costs down.
Reduce Cooling Costs with Passive Ventilation
The primary benefit of passive ventilation is its relatively low cost. The initial investment is lower when compared to active electric fan systems, and once your structure is outfitted with the necessary features, the utility and maintenance costs are low as well.
Passive ventilation relies on two factors, the wind effect and thermal buoyancy. The wind effect refers to the principle stating that wind blows around buildings, creating small pressure differences on the outside of the structure. Wind is essential to passive ventilation, and speeds of only two to three miles per hour can provide much of the air circulation. Thermal buoyancy is the effect of cold air lifting warm air up towards the top of the structure. It can aid air exchange exceptionally on cooler days, but less so when it is hot.
The standard passive ventilation methods are roof and wall vents. Growers operating in regions with strong summer winds and plenty of open area can take the most advantage of vents. The American Society of Agricultural & Biological Engineers recommends that the overall vent area should equal 15 to 20 percent of the floor area. Growers can also customize their greenhouse with doors, louvers, shutters and other ventilation passages for improved air circulation. The ideal passive ventilation system will utilize all these options, maximizing the potential air flow.
Greenhouses that are constructed with passive ventilation in mind can take advantage of these two principles, lowering operating costs and increasing energy efficiency. Modern greenhouses are designed to provide maximum ventilation, and growers should work with a professional to design a structure that makes optimal usage of passive ventilation options. Still, there are times when passive ventilation simply will not provide the necessary level of cooling. Fortunately, there are many other cooling options available.
Lower Greenhouse Temperatures with Active Ventilation
Active ventilation can also help lower temperatures, but it requires increased operating costs (electricity consumption) and maintenance. Regardless, in situations when greenhouse temperatures are climbing and passive ventilation is unable to regulate them, active ventilation can be essential.
Fans are a key method for active ventilation. Fans provide positive air movement regardless of weather conditions, drawing cool air in through ventilation passageways. There is a wide selection of circulation fans, shutters, louvers and exhausts available. There are a variety of factors that affect fans’ air circulation capabilities, and it is important to consider them before installing any equipment.
First, fans should be the proper size to sufficiently circulate the air within the greenhouse. For summer ventilation, fans should be able to provide one air exchange per minute up to a height of eight feet. You can discover the ventilation rate that is right for your greenhouse by multiplying the dimensions of your greenhouse by the height used above. In hotter climates, a height of up to 10 feet is sometimes used.
Fan location should also be considered. For a system to work to its fullest potential, fan draw distance should be less than 150 feet. Fans should also be located higher in the structure, so that the air flows over the plant canopy. On the opposite end of the greenhouse, louvers should be placed in the wall to allow proper airflow. It’s also important to perform proper maintenance on fan systems regularly. Cleaning fan blades, belts and motors, and removing dirt, weeds or grass from louvers and shutters are both critical to ensuring a long lifespan for the system.
For growers needing even stronger cooling power, there are more powerful options available, like evaporative cooling.
Cool Even the Hottest Structures with Evaporative Cooling
Evaporative pad and fan cooling is a powerful way to cool a greenhouse, but the ARK cooling system is as powerful using a fraction of the electricity and 50% less water. Using heat in the air to evaporate water from plants, evaporative coolers or swamp coolers use water-soaked pads and other surfaces, by way of lowering temperatures considerably. These systems are also more complex than other cooling methods. They have multiple mechanical parts and require increased utility costs. However, if an operation requires serious cooling capacity, few greenhouse methods compare with evaporative cooling. The ARK cooling system is as effective.
Up to now the fan and pad system has been the preferred method for evaporative cooling. Typically, the system consists of cellulose pads, a water pump, water storage and fans. The cellulose padding is soaked with water administered by the pump. Excess water is then collected into the storage system. Exhaust fans opposite the pads then pull air through the wet surface, evaporating water into the air and cooling the greenhouse. Evaporative cooling works better when relative humidity is low, so this method is especially effective in more arid regions.
It is important to properly size your fan and pad system to ensure maximum cooling efficiency. About one square foot of pad is required to cool 20 square feet of floor area. Likewise, it is necessary to properly clean evaporative pad systems. Algae can quickly become an issue with this method.
When growers need another layer of cooling, or improved control over light and photoperiod, they should consider adding a curtain system.
Keep the Temperatures Balanced with Curtain Systems
Curtain systems are often used in conjunction with other cooling systems. Curtain systems can reduce plant stress and improve the environment of your greenhouse. Supplemental shade screens cool the greenhouse by reducing the amount of light that can enter the structure. Curtain systems can be used internally or externally, although internal shade screens are more common. Internal curtain systems are generally retractable, allowing growers to decide when to reduce light entering the structure. Growers should look to purchase curtain material constructed from durable polyolefin film and featuring a strong monofilament yarn structure.
When choosing a curtain system, there are multiple designs to consider. Gutter-to-gutter systems use less shade material but form bulkier bundles when retracted. Truss-to-truss systems are the most common and can be configured in several ways. Many greenhouses are now using flat truss-to-truss systems, as it reduces the area of greenhouse that needs to be cooled. Recently, growers have started using a two-screen system. By combining a climate screen with a light deprivation screen, growers can achieve maximum control.
Curtain systems come in several colors, though the most popular are black and white. They are also available in different gradients of shade. This gradient is measured in percentages, such as 30, 60, or 90 percent shade. However, while these percentages do illustrate the amount of light being kept out of the structure, it is important to note that these measurements do not represent temperature reduction.
The oldest methods of shading involve the application of semi-opaque materials to the glazing either as unresponsive liquid coatings or in the form of fabric screens. ARK offers responsive, retractable options.
External shading has the advantage of absorbing and reflecting light energy before it enters the enclosed greenhouse, heating the air and all enclosed objects. The disadvantage of external shade methods are that the coatings are semi-permanent (they must be added and washed away with significant labour cost) or externally mounted retractable screens are expensive to construct and maintain due to wind and weather conditions.