Welcome back to the Control Room where we talk about the more technical aspects of our greenhouses. This episode will cover different greenhouse dehumidification strategies for our vented and sealed (otherwise known as our SunChamber™) solutions.
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• The Control Room | Int...
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0:00 Control Room introduction
0:31 Plant transpiration
1:53 Benefits of a sealed system
2:19 Condensation concept
2:58 Refrigerant dehumidification
4:40 Desiccant dehumidification
In this second video, we will talk about dehumidification
It is one of the lesser talked about, and yet more important, subjects related to the grow environment. Before we jump in to discussing dehumidification, let’s first make sure we have a basic understanding of transpiration. If you didn’t know, plants transpire. Transpiration is the process by which plants intake water through the root system in a liquid form and exhaust it from the stomata in a vapor form which increases the amount of moisture in the greenhouse and its relative humidity. Usually, transpiration is driven by environmental factors such as light intensity, carbon dioxide concentration and Vapor Pressure Deficit. Vapor Pressure Deficit (also called VPD) is used to describe the combination of temperature and relative humidity of the air surrounding the plant leaves. When talking about light intensity we need to think about energy. The more energy the plants receive, the more energy they need to release in order to stay healthy, and this is done through transpiration. A healthy crop transpires a lot so there will always be some dehumidification to deal with. If your greenhouse is ventilated, the cheapest way to deal with this added moisture is to exhaust it outside. It gets a little more complicated with a sealed greenhouse like the Ceres SunChamber™ which doesn’t exhaust the air but instead relies on a HVACD system to recirculate and treat the air. So why go sealed? A sealed system allows for many benefits such as biosecurity and a better controlled environment. The downside is a higher energy expenditure. Typically in sealed environments, there are two methods of dehumidification: using refrigerant - (also called condensing) and desiccant. But first; let me introduce the concept of condensation. When warm and moist air gets in contact with cold surfaces, the water vapor in the air condensates. A manifestation of this phenomenon is the dew you can see at dawn on grass or plants after a clear sky night. Clear sky nights make ground surfaces emit more energy, meaning the ground gets colder than cloudy nights when the ground loses less energy since the difference of temperature is smaller. Air can hold less moisture as it gets colder. The temperature at which it cannot hold any more moisture is the saturation point or Dew point. Refrigerant or condensing dehumidification uses the same principle as the refrigeration cycle which we covered in a previous video. please check the link the description below. The same process can be applied to dehumidification. In a grow environment, the excessive moisture introduced by plants transpiration is contained as water vapor in the air. The same air is then sucked towards the HVACD system. When air makes contact with the refrigerant cooling coil and reaches its Dew point condensation occurs, meaning dehumidification is happening. Condensate water is considered clean and can be reclaimed. However, it is not advised to reuse this water directly into your solution unless it has been treated. It is challenging to find efficient equipment to deal with dehumidification. One reason being that to be able to condensate as much as possible, the air has to slowly come in contact with the condenser coil. The second reason is that bringing the air to the Dew point means that you have very cold air being blown into the grow environment. The air needs to be reheated before being reintroduced, otherwise it will stress the plants. So, the air needs to be cooled down to a very low temperature which requires a lot of energy, and then it needs to be heated back which requires even more energy. Dehumidification is a very hungry process. The EcoLoop™ is a smart dehumidification system since it uses refrigerant dehumidification with efficient design of the cooling coils and reuses some of the heat loss from the compressor. It also allows for a very high reclaim percentage of the water being transpired from the plants, up to 95%. To summarize, when cooling is required, the warm air from the greenhouse goes through the condenser coil which is filled with a liquid called refrigerant. The heat transfers from the warm air to the cold refrigerant.
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