The Challenge
A commercial greenhouse vents warm, CO2-rich air to control temperature. That venting wastes both heat and the very CO2 the plants need, raising fertiliser costs.
The Solution
A sensible plate exchanger recovered heat from the vented air to pre-warm the incoming fresh air. Because only heat was transferred, the CO2 stayed in the growing zone while the temperature was controlled.
Results
- Lower heating demand during cold nights
- Less supplemental CO2 needed to maintain growth rates
- More stable canopy temperature
Lesson
When the transferred species matters, sensible-only recovery is the right call. The plate core moved energy without moving the gas you wanted to keep.
The Situation
In the Greenhouse CO2 and Heat Recovery project the plant was expelling large volumes of warm exhaust while paying to heat incoming make-up air from ambient. Energy bills were high and the roof fans ran continuously, so the lost heat represented a clear, repeatable cost rather than a one-off event.
The Solution
We installed an air-to-air heat exchanger sized from measured airflow and temperature, with filtration ahead of the core and a condensate drain on the supply side. The supply fan was balanced against the exhaust to hold the building near neutral pressure, and a bypass damper allowed free cooling in mild weather. Control was kept simple: a temperature signal set the bypass position automatically.
The Result
After commissioning, supply air entered the heater roughly 50 percent warmer than before, cutting heater energy in line with that recovery. The measured payback fell inside the expected one-to-three season window, and a seasonal check showed the core holding its performance once a light cleaning routine was in place. The same approach has since been repeated on similar duties.
Frequently Asked Questions
How was payback proven? By comparing supply temperatures before and after at the same outdoor condition. Was extra maintenance needed? Only a seasonal inspection and occasional exhaust-side cleaning.
Practical Selection Checklist
For the Greenhouse CO2 and Heat Recovery duty, confirm the measured airflow and the temperature difference between the two airstreams before specifying any unit. Choose the core type that matches the exhaust cleanliness and the recovery target, allow margin for fouling, and verify the pressure drop stays inside the fan curve. Place filtration ahead of the core and provide a condensate drain where the supply side may fall below the dew point.
When to Specify This Solution
Energy recovery suits any plant or building that expels warm exhaust continuously while drawing in fresh air that must be conditioned from ambient. Common candidates include make-up air units, drying rooms, commercial kitchens, paint booths, and general process ventilation. Where the annual cost of heating or cooling make-up air is material, a correctly sized exchanger usually pays back within one to three operating seasons.
Next Steps
Start by logging the supply and exhaust conditions for a full duty cycle, then size the core from those numbers rather than from nameplate estimates. Compare the projected energy saving with the equipment and installation cost to get a payback figure, and review the comparison and product guides for the specific configuration that fits your site.