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Heating & Cooling Systems

How do I determine the number of fans in a greenhouse?

To calculate the number of fans in a greenhouse, it is important to have three basic factors available. With these basic factors, Vostermans Ventilation can calculate the number of fans step by step.

Basic factors
Greenhouse dimensions: Start by calculating the volume of the entire greenhouse and make a note of the dimensions.

Circulation rate: The circulation rate is equal to how many times per hour the air is circulated in a greenhouse. In practice, we often see that a circulation rate of 2 or 3 is chosen. In some situations, a circulation rate of 12 or higher is chosen. The ideal circulation rate depends on the situation on-site, and the crop.

Fan specification: Finally, it is important to know how many m3 of air the fan moves per hour, and what the maximum recommended usable throw is. Vostermans’ Greenhouse Fans are divided into 3 lines: the 5,000, 7,000 and 8,500 m3/h versions. You can find this information on the lid of the fan motor, in the brochure, or the datasheet.

Current situation
In the current situation, our assumptions are based on a greenhouse of 160,000 m3. If we multiply this by the circulation rate of 3, we know that the circulation fans have to move 480,000 m3 of air per hour.

Step 1: Number of fans to achieve the circulation rate
To know how many m3 of air must be circulated each hour, we can simply divide this by the number of m3 that a fan moves per hour. Depending on your wishes, you can choose a fan from the 5,000, 7,000 or 8,500 m3/h line. In this case, we have assumed an ideal situation with ideal greenhouse sizes and suspension points at any desired location. We have included these variables in steps 2 and 3. We then arrive at the following number of fans:

4,850 m3/h: 99 fans
6,500 m3/h: 74 fans
8,700 m3/h: 55 fans

Step 2: Distance between fans
To prevent fans being located outside of each other’s airflow, we recommend that you do not exceed the recommended throw. We have verified this recommended maximum usable throw in practice, with smoke tests. In practical terms, this means that with hanging options every 4 meters, a fan with a recommended throw of 35 meters will be suspended at a distance of 32 meters.

Step 3: Greenhouse dimensions
Finally, the fans should be evenly distributed along the length of the greenhouse. In practice, the length of the greenhouse is often not divisible by the fan distance calculated in step 2. In this case, the fans are hung even closer together to obtain the right distribution in the greenhouse, and to avoid exceeding the maximum recommended throw.

For more information:
Vostermans Ventilation
www.vostermans.com

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Asia

Priva Middle East team has been in Qatar

Over the past few days, the Priva Middle East team has been in Qatar. Together with colleague Jan Westra from the Netherlands, our GM Giovanni A. visited various knowledge institutes, government entities and the well-known QTFA farm.

The trip, co-organised by Heba leith from the Netherlands Embassy in Qatar, included a visit to Hassad Food, Qatar’s premier investor in the food and agri-business sectors, and the Ministry of Municipality. During these visits, our Priva team discussed potential collaborations including the opportunity to jointly form an eco-system to achieve the set goals of Qatar’s food security strategy.

To build a robust food security strategy, Qatar has outlined its focus on four pillars:

1. Ensure that trade routes are diversified so that risk-exposure is limited and a contingency plan for alternative routes as needed;
2. Move food from port, field or reserves to table as efficiently as possible (i.e., limiting food losses/waste), with regulations that foster competition and encourage safety;
3. Put in place adequate but sensible reserve capacity to act as a buffer in time of crisis, both for inputs (water, seeds, fertilizer) and outputs (food products); and
4. Efficiently cultivate crops, meat and fish within the confines of a Qatar’s resource base to ensure a stable source of perishables in times of crisis, as well as providing a regulatory framework that creates incentives to focus on commodities that make sense from a cost-competitiveness point of view.

Source: (former) Qatar Ministry of Municipality & Environment (MME), Qatar Food Strategy 2018-2023.

Jan and Giovanni also met with representatives from Qatar University and the Qatar Environment & Energy Research Institute (QEERI) part of Hamad Bin Khalifa University. QEERI is a national research institute tasked with supporting Qatar in addressing its challenges related to energy, water and the environment. The institute’s work is in line with the goals set forth by Qatar National Vision 2030, and is supported by the Qatar Foundation Research, Development and Innovation.

On Monday, a visit to Arab Qatari Agricultural Production Company (QTFA) was on the agenda. Established in 1989, QTFA is considered the largest agricultural farm in Qatar. Spanning a total land area of 200 hectares, the farm is divided into open fields and greenhouses (cooled and un-cooled). QTFA produces around 28 types of premium vegetables and among other well-known Dutch companies, Priva’s products are in place at the farm. Senior Agronomist Carol Khadra and Senior Production Supervisor Buddhi Magar very kindly took the time to show our colleagues around the farm and its locally produced crops, including tomatoes and cucumbers.

The trip to Qatar concluded with a luncheon with Dutch Ambassador, H.E. Mrs Marjan Kamstra, Deputy Ambassador, H.E. Tiest Sondaal, Business Developer Gulf Region NL Embassy, Heba leith, and Chairman of the Dutch Business Council Qatar, Robert W. Cats Cats.

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Cultivation

Strawberry substrate production systems: a review by Omafra

Growers have many options when it comes to establishing strawberry substrate production. OMAFRA’s Erica Pate reviews different container options, tabletop and suspended systems, and different structures used for strawberry substrate production.

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Equipment

Pura Hoja: refrigeration extend the shelf life by 2-6 days

Speaking is Tomás Benavente of Pura Hoja, the largest grower of hydroponic lettuce in Chile: “The time of harvesting must be carefully planned, the product must not be harvested too late. Temperature control is also vital for shelf life. Depending on the crop, the entire cold chain ideally takes place in a room with a temperature between 2-5° C.” 
The thin and narrow shape of the land makes distribution a major complication for hydroponic products. By refrigerating their produce, they can keep the lettuce as fresh as possible before it hits supermarket shelves.
purahoja1

Pura Hoja was founded in 2010. Over the past ten years, the company has grown to become the largest grower of hydroponic lettuce in Chile. They are currently growing lettuce on their NFT system, while also doing trials with herbs and baby vegetables. According to Tomás, the company is technologically capable of growing any green leafy vegetable in their greenhouse. He believes there is a great opportunity for the horticultural sector to become more efficient through the use of technology, but the market must also appreciate these products.

Tomás: “Growing a healthy crop all year round is a major challenge. Technologies that regulate the climate, disinfection and disinfection, fertilization and crop management are extremely important. With these techniques we can control all climatic conditions in the area. .”

Since this technology is not easy to manage and also expensive, the market has to appreciate the added value of the hydroponic products. And that is why the lettuce must be of impeccable quality when it reaches the consumer. The Pura Hoja lettuce is sold on the national market, mainly through the retail channels. “The time of harvesting has to be carefully planned, because the lettuce should not be too old. Then temperature control is crucial.”

purahoja2

For extra shelf life, Pura Hoja has been working with a vacuum cooler for two years now. This cooler, supplied by the Dutch company WeberCooling, helps them keep the lettuce as fresh as possible before it hits supermarket shelves.

Sylvia van Uden of Weber Cooling: “By lowering the pressure in the vacuum chamber, you force (a fraction of) the product’s own moisture to evaporate. This evaporation costs energy, which is extracted from the product in the form of a temperature reduction.” The WeberCooling team is also very active in the American vertical farming market and in Latin America with their technology. Both hydro growers and vertical farmers have opted for the systems because it extends the shelf life of the products. The same goes for Pura Hoja.

Tomás: “The vacuum cooler helps us to lower the temperature very quickly after harvesting, which directly affects the shelf life of the product. After harvesting, we cool the products for at least 20 minutes. This process allows us to extend the shelf life by at least 2-6 days and according to some figures even up to 10 days.This way we deliver healthy lettuce with maximum freshness to our consumers.”

For more information:
Pura Hoja
Valparaiso / Chile
www.purahoja.com

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