"A conventional greenhouse, whether it is glass or plastic, is a perfect fit for a climate with cold winters, such as in Canada, The Netherlands or Russia. In these climates the greenhouse can keep the crops warm during winter and provide a cool, protected environment during the mild summer. "However, when you go to any country between the equator and latitude 30, cooling is a much bigger problem than heating. Here conventional greenhouses typically struggle to produce good quality fruits at a low cost during the hot summers. In fact many naturally ventilated houses are empty during the hot summer conditions."
"Therefore, any grower located between the equator and latitude 30 can achieve greater yields and higher quality using a retractable cooling house. This is because the roof covering is designed to block excessive heat before it enters the house, whereas a ventilation system uses <2 kilowatt per hour of electricity per hectare per day and minimal water for cooling. The ability to retract hectares of cooling roofs in minutes when outdoor conditions are optimal allows growers to take advantage of full sunlight and lower humidity conditions. This is especially important for growers of berries and lettuce."
Over the last couple of years, Cravo has gained significant experience with the use of their retractable cooling houses in many locations throughout the world. "Retractable cooling houses were developed specifically for countries where conventional greenhouses and nethouses struggle to maintain optimal growing environments when outdoor temperatures are 35C-50C."
In these hot climates, many growers used pad and fan cooling but found the electricity and water usage prohibitive. Some growers then switched to lower cost nethouses but found that their harvest season was limited by the summer heat, the winter cold and rain. The retractable roof cooling house plus a layer of insect net combines the advantages of a nethouse with the climate optimisation of a retractable roof which eliminates the problems with conventional net house agriculture."
In this video, Richard Vollebregt of Cravo explains the difference between a conventional greenhouse and a retractable cooling greenhouse. He also highlights the system's potential to create better performing crops, with less inputs and a minimal ecological footprint as energy-guzzling pad and fan cooling are no longer required to grow in a hot climate.
To create the best practices and protocols for growing between the equator and latitude 30, Cravo built a retractable cooling house in Culiacan Mexico. This house is used to grow a variety of greenhouse vegetables and serves as their demonstration and training center to showcase the potential of the system. The combination of the retractable cooling roof and insect net has already achieved yields of 40-50 kg/m2 of tomatoes and 15-17 kg/m2 of colored capsicums during the winter production season and potential still exists to increase it further. This year, tomatoes, peppers and cucumbers will be grown 52 weeks per year with crops having been transplanted August 15 and March 1.
“Most research in the world has focused on growing crops in a fully controlled environment. Our own research however, has taught us that exposing plants to the natural outdoors in the morning when outside temperatures are ideal and then protecting them using the cooling roof at midday, causes plants to develop a much higher tolerance to high temperatures and greater fluctuations in humidity. The retractable roof trains the plant to grow a stronger root system and smaller thicker leaves which helps it sustain itself in extreme temperatures."
Cravo is currently building projects with their retractable cooling greenhouses in countries such as Oman, Mexico, Nigeria, Chile and Australia.
For more information
Cravo Equipment Ltd
Richard Vollebregt
President
30 White Swan Road,
Brantford Ontario, Canada N3T 5L4
Phone: +(1) 519 759 8226 x 215
Mobile: +(1) 519 732 8054
Skype: richardvollebregt
richardv@cravo.com
www.cravo.com