Tracking transpiration is the key to saving energy

2HARVEST | www.2harvest.nl

Creating an optimal growing climate in a greenhouse requires energy.

With energy prices on the rise, this is a significant expense for greenhouse operations. There are many options for minimizing the amount you spend on energy, such as installing solar panels or windmills.

However, if you want to reduce the amount of energy you use in your greenhouse, the real secret is to track plant transpiration.

What is transpiration?

Transpiration is a necessary process in plants’ metabolisms that ensures growth. Water absorbed by plants travels through stems and leaves and then evaporates through pores on leaf surfaces. When plants transpire, their pores open allowing for the diffusion of carbon dioxide gas for photosynthesis. Transpiration also changes the osmotic pressure in cells, enabling the flow of mineral nutrients through the shoots.

Plants need to transpire to thrive. Adequate transpiration leads to optimal growth. Plants that transpire sufficiently are more generative, and have smaller leaves, stronger stems, and bigger fruits.

What does transpiration have to do with energy consumption? Plants transpire best when in an active dry climate. How much of the energy used in your greenhouse goes to creating optimal conditions for growth?

Greenhouse energy consumption

Your greenhouse is all about providing plants with optimal growth conditions. Let’s look at power consumption for creating your environment.

• Artificial light: Plants need light for photosynthesis. This light is converted into energy that is used to grow, bloom, and create seeds. In northern climates with less light in the winter season, greenhouses can use about 1 megawatt per hectare per house on artificial light.
• Heating: Tomato, cucumber, and bell pepper plants thrive best around 20 degrees Celsius. If your climate is generally cooler than this, heating is required. However, heating is not just for increasing temperatures. Heating is also used to dehumidify the greenhouse because high humidity can reduce growth. Greenhouses can use about 300,000-500,000 cubic meters of gas per hectare per year for heating.
• Irrigation: Irrigation systems often rely on electric pumps to distribute water throughout the greenhouse.
• Automatization: Anything automated, from trollies, sensors, or other equipment uses energy. These automated systems are hugely important to reduce labor and improve plant production.

While there are many options for reducing the power used for any of these processes, we’re going to focus on the one that uses the most energy: heating. Heating greenhouses has two purposes: the first is to keep plants warm. The second is the reduce the humidity to ensure plants transpire sufficiently. Plants transpire less in humid environments, meaning that heating is an important element to ensure your plants absorb nutrients and photosynthesize as required. Read on to learn how you can reduce the amount of energy invested in heating while ensuring your plants are transpiring sufficiently.

An energy-saving heating strategy

If your heating strategy is based only on the temperature of your greenhouse, then you might not be very energy efficient. You could save energy by basing your heating strategy on transpiration, air ventilation, and airflow. In this strategy, you’ll focus on plant temperature rather than air temperature. Plant temperature is generally 1-2 degrees cooler than air temperature if your plants are transpiring adequately. You can test plant temperature with infrared equipment or other instruments specifically for this purpose.

Based on your plant temperature and transpiration speed, you can decide how much heating is needed in your greenhouse. Before you turn up the gas for heating, try using ventilation to optimize growth with less energy.

For example, mounting a thermal screen on top of your greenhouse is a very efficient way to warm your plants. Acting as a blanket, thermal screens keep warmth inside and isolate the greenhouse by 40%. Adding a second screen or even a third screen provides even more isolation, reducing the need to use energy for additional heating.

To keep plants transpiring with thermal screens, you can keep the windows open in your greenhouse even when the thermal screens are closed. Plants mostly transpire during the day when there is less of a need for heating. Open windows improve ventilation and reduce humidity naturally. Close the windows at night, when plants are less likely to transpire, to keep the greenhouse warm under a thermal screen.

Closed thermal screens increase plant temperature, meaning you’ll be able to set a lower temperature in your greenhouse. You can measure the plant temperature with special tools, which will be a profitable investment when they help you efficiently manage your greenhouse’s climate.

Other options for energy-efficient heating include using solar panels or wind turbines to create your own energy.

How energy efficient is your greenhouse?

Once you’ve developed a heating strategy, you’ll want to test how efficient it is. You can do this by creating benchmarks. First, check how much energy you were using before you implemented your new strategy. Are you using less energy now?

Next, you should benchmark your energy usage against other greenhouses in your climate. How much energy are you consuming compared to them? If you’re consuming more, you might be able to improve further. If you’re using less, great job!

It’s important to note that no matter how efficient your greenhouse is, you still need to use energy to sustain your crops. The most expensive cubic meters of gas are the ones you unnecessarily avoid using. Don’t cut corners with energy usage! If you need to turn on the gas to warm your crops, do it so your plants don’t suffer.

If you’re interested in learning more about Paskal’s range of products and how they can help you benefit from joining the circular economy, contact us today.

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If you like this article you would be interested in reading the following articles:

• The article: From Crops, to the Cockpit
• The article about How sustainability can support you in the long run