Ambient or electric CO₂ vaporizer: what to choose for a greenhouse

CO₂ enrichment raises yield only if the gas arrives steadily and at the right temperature. The vaporizer decides both, and in a Ukrainian winter the choice is not obvious.

Liquid CO₂ is stored at about −20 °C under pressure. If you simply release the pressure without adding heat, part of the product turns into dry ice and blocks the pipeline. That is why a CO₂ vaporizer is not a length of pipe but a device with controlled heat input and temperature control at the outlet.

Ambient air vaporizer

It takes heat from the surrounding air through finned aluminium tubes and needs neither electricity nor steam. For nitrogen, oxygen and argon this is the standard solution. For CO₂ in Ukraine it works only within limits: in cold weather and at high take-off the air simply does not carry enough heat, the unit ices up, and the outlet temperature drops below what the dosing system tolerates.

For a greenhouse there is one favourable factor: the peak of CO₂ demand falls on daylight hours, when the air is warmest. But winter enrichment, which is exactly when it matters most for yield, remains the weak point.

Electric or water-heated

• Stable outlet temperature all year round, independent of weather.
• Controlled automatically to a setpoint, which the dosing computer needs.
• Requires power. As an order of magnitude: the latent heat of CO₂ is around 275 kJ/kg, plus heating the gas to ambient, so roughly 30 kW is needed for 300 kg/h.
• The water or steam version pays off when the site already has a hot water circuit — the running cost then drops to the pump.

How to size the capacity for a greenhouse

As a rough guide, a closed greenhouse consumes about 30–60 kg of CO₂ per hectare per hour at peak, depending on ventilation and the target concentration, which is usually kept at 700–1000 ppm against roughly 420 ppm in outside air. For five hectares that means 150–300 kg/h, so a 300 kg/h vaporizer with a margin is the sensible pick.

Open vents change the picture completely: as soon as ventilation starts, consumption rises sharply while the effect drops. This is worth agreeing with the agronomist before choosing the equipment, not after.

A practical compromise

On many sites the workable answer is an ambient vaporizer as the base plus an electric one for peak and winter operation. The base runs for free most of the year, and the electric unit switches in when the air stops coping.

What else the system needs besides the vaporizer

• A dosing unit with a control valve that the climate computer can command.
• CO₂ sensors in the growing zone, not only near the unit — concentration varies strongly across a greenhouse.
• Distribution hoses along the rows; without them the gas stays where it entered.
• A pressure-reducing station matched to the dosing pressure, usually far below the tank pressure.

The classic mistake

The vaporizer is sized by average daily consumption instead of the peak hour. On paper the numbers add up, in practice the concentration sags exactly at midday, when light is at its maximum and the plant would use the CO₂ best. Size for the peak hour with a margin of twenty to thirty percent; the extra capacity costs far less than a season of underfeeding.

Send us the greenhouse area, crop, ventilation type and target concentration — we will calculate the capacity and show both variants with running costs.