Energy Recovery Group DIY kit

The ERG – short for Energy Recovery Group (ERG) – is an improved supply and exhaust air system with an energy recovery unit.

It recovers the process heat from the warm cultivation room and transfers the heat energy to the supply air. Thus, the ventilation system meets the requirements of the Building Energy Act (GEG in German) which requires that from 1000 m³/h air circulation, at least 75% of the heat from the interior is transferred to the supply air.

In addition, the ERG system passively dehumidifies the room as long as the outside temperatures are lower than the inside temperatures and the outside air is drier than the air in the cultivation room, especially at warmer temperatures. A condensate drain is integrated in the ERG module for this purpose.

The ERG is ideal for energy-efficient ventilation of cultivation rooms in autumn, winter and spring. In summer, we recommend the additional use of climate control systems and dehumidifiers to achieve the desired climate conditions in the cultivation room.

Since their use is energy-intensive and leads to climate fluctuations, a cultivation room with an ERG can be operated with the lights on at night during the summer to take advantage of the lower night-time temperatures. Growing resistant strains that are less susceptible to high humidity and temperatures is another way to minimise the risk of crop loss without the need for additional climate control systems and dehumidifiers.

We use a counterflow heat exchanger for energy recovery. This is one of the most efficient methods of energy recovery and, depending on the outside temperature, transfers up to 95% of the heat energy from the exhaust air back to the supply air.

Other systems, such as rotary heat exchangers, require significantly more space for energy recovery and often exceed the dimensions of the rest of the Air Handling Unit components. In addition, they are less suitable for high air exchange rates due to their design. Another disadvantage is the partial mixing of supply and exhaust air, which increases the risk of contamination of the room air.

On the other hand, cross-flow heat exchangers are less efficient than counter-flow heat exchangers because the contact surface is smaller.

1. Heat Transfer & Efficiency

• Counterflow Heat Exchanger: The clear front-runner with a heat transfer efficiency of up to 95%. The counterflow principle means that the temperatures of the two media converge significantly, ensuring optimal energy utilisation even with large temperature differences. 👉 Maximum energy savings and precise temperature control.

• Crossflow Heat Exchanger: Efficiency is only 50–70%. The temperature approximation is significantly lower because the airflows only briefly cross each other and energy is lost. Suitable for simple applications, but not an optimal solution for demanding systems.

• Rotary Heat Exchanger: Efficient (up to 85 %), but significantly behind the counterflow principle. The continuous heat transfer process is more prone to failure and often leads to mixing of the airflows, which impairs temperature control.

2. Airflow & Throughput

• Counterflow heat exchanger: Excellently suited for high air volumes. The design allows the transport of large volume flows without significantly affecting efficiency. Consistent and uniform performance, even with fluctuating air volumes.
• Cross-flow heat exchanger: The air flow rate is very limited because the cross-flow requires a compact design, which significantly increases the space required for larger volumes.
• Rotary heat exchanger: Can also handle large air volumes, but the rotor causes pressure losses and additional friction losses, which increases the fans' energy consumption. In addition, air mixing is a problem, especially when it is important to keep the airflows separate (e.g. in cultivation rooms).

3. Moisture Removal

• Counterflow heat exchanger: ideal for effectively removing humidity. Because the two airflows remain separate, excess moisture is removed from the room precisely and safely, without being returned. Perfect for cultivation rooms, as well as for climates with high humidity.
• Cross-flow heat exchanger: the airflows also remain separate, so the removal of humidity generally works. However, even in this area, the efficiency lags behind the counterflow heat exchanger.
• Rotary heat exchangers: Not only can they remove moisture, they can even return it to the supply air. This is problematic in areas where humidity control is crucial. In humid climates or where there is high indoor humidity, this often leads to an unwanted increase in humidity.

4. Reliability & Maintenance

• Counterflow heat exchanger: robust, low-maintenance design because there are no moving parts. Particularly in industrial applications and larger buildings, the counterflow heat exchanger is the most reliable and economical choice in the long term.
• Cross-flow heat exchanger: also low-maintenance and reliable, but significantly higher energy costs due to lower efficiency, as less heat is recovered at night and more has to be post-heated.
• Rotary heat exchangers: Significantly higher maintenance requirements due to the rotating element. Parts subject to wear, such as bearings and drives, must be regularly checked and replaced. In addition, leaks and contamination between the incoming and outgoing air flows can occur.

Conclusion – Why CarbonActive uses counterflow heat exchangers for plant cultivation:

The counterflow heat exchanger combines maximum energy efficiency, maximum air flow rate and precise removal of moisture in a low-maintenance and durable system.

The ERG DIY kit is primarily designed for installation by local ventilation experts and electricians or the project team behind the facility.

For this we provide you with all the necessary schematics.

If you insist on an installation by CarbonActive in order to avoid making mistakes, we would be glad to discuss this.

If you have not yet installed any rooms, our IGC may also be worth considering. The »Basic« variant also uses the Energy Recovery Group (ERG) system, in addition to all the other components of the sandwich panels, benches, lighting and recirculating air ventilation installed by our installation team. All components are precisely matched to each other, so you get a cultivation room that meets the highest standards.

Ventilation openings for supply and exhaust air must be installed on-site. In addition, the supplied control cabinet and the motors must be wired to the local power grid and the sensors and actuators must be connected to the control cabinet. Certain connecting ventilation ducts (ideally insulated spiral ducts) must be installed on-site to fit your individual ventilation plans.