Climate control efficiency and room size

James Eaves · Nov 14, 2017

I often hear from growers that if a grow room becomes too small or too large climate control becomes less efficient. This is a separate issue from the potential cost of a pest or mold outbreak increases with room size. For instance, one grower told me that when the room gets relatively small (for them the cut off was around 1400 ft2) temperature and humidity variability starts to increase to unacceptable levels, and he blamed it on decreases in HVAC efficiency at that scale. At the same time, I recently spoke with an HVAC vender who told me that room size doesn't matter. What do you think? And if you think room size does matter, do you have an explanation why? Thank you.

SchmoeJoe · Nov 14, 2017

James Eaves said:
I often hear from growers that if a grow room becomes too small or too large climate control becomes less efficient. This is a separate issue from the potential cost of a pest or mold outbreak increases with room size. For instance, one grower told me that when the room gets relatively small (for them the cut off was around 1400 ft2) temperature and humidity variability starts to increase to unacceptable levels, and he blamed it on decreases in HVAC efficiency at that scale. At the same time, I recently spoke with an HVAC vender who told me that room size doesn't matter. What do you think? And if you think room size does matter, do you have an explanation why? Thank you.

If anything the only thing that would explain unacceptable levels of variation in a larger space would be not having the right equipment and layout. Even if you went with a +25% margin for a buffer with your equipment if it's all in one side of a large space you're not going to have consistent conditions across that space.

ANC · Nov 15, 2017

I will soon be testing the limits on this. I realised what a hard time (high cost) we have doing a relatively small room.
I decided I would test a new approach building a module that grows just one plant at a time. The incoming air temperature will be modulated by two peltiers set up to warm and cool alternatively, on the same radiator, cold will be "pumped" from external peltier using water or mineral oil. Internal airflow should mainly be to distribute the temperature and humidity evenly as we are pumping the heat out separately. Plants will be in temperature controlled hydro or aero, lights will have water cooling transferring the heat to more external peltiers, where the heat will be given off to the atmosphere and condensation collected where it cannot harm electronics. It leans well to tinkering with fully sealed and CO at a later stage. Each tube should be able to produce about 2 to 3 ounces at a minium.

Everything is to be controlled by a microprocessor (I still do old-school assembly language), so (power hungry) peltiers only come on when the fans on the external coolers can no longer keep up with the baseline room temperature being too high.
Not sure about the luminaire design yet, it needs to be able to move up and down in the tube while connected to 2 water pipes as well as the two wires for the COB/s (considering using 2 at half power for redundancy).This thing will be a consumption beast when summer heat strikes, but it would bite off no more than it can chew and inside the thermally insulated tube, conditions for the plant should be as close to ideal as possible from start to end. The only thing you should be able to fuck up is nutes in the reservoir and setting light levels as the plant's cycle progresses. The rest of the time it would use no more power than needed. At the correct room temp it would be mainly the lights fans, heater and water pumps

SchmoeJoe · Nov 15, 2017

ANC said:
I will soon be testing the limits on this. I realised what a hard time (high cost) we have doing a relatively small room.
I decided I would test a new approach building a module that grows just one plant at a time. The incoming air temperature will be modulated by two peltiers set up to warm and cool alternatively, on the same radiator, cold will be "pumped" from external peltier using water or mineral oil. Internal airflow should mainly be to distribute the temperature and humidity evenly as we are pumping the heat out separately. Plants will be in temperature controlled hydro or aero, lights will have water cooling transferring the heat to more external peltiers, where the heat will be given off to the atmosphere and condensation collected where it cannot harm electronics. It leans well to tinkering with fully sealed and CO at a later stage. Each tube should be able to produce about 2 to 3 ounces at a minium.

Everything is to be controlled by a microprocessor (I still do old-school assembly language), so (power hungry) peltiers only come on when the fans on the external coolers can no longer keep up with the baseline room temperature being too high.
Not sure about the luminaire design yet, it needs to be able to move up and down in the tube while connected to 2 water pipes as well as the two wires for the COB/s (considering using 2 at half power for redundancy).This thing will be a consumption beast when summer heat strikes, but it would bite off no more than it can chew and inside the thermally insulated tube, conditions for the plant should be as close to ideal as possible from start to end. The only thing you should be able to fuck up is nutes in the reservoir and setting light levels as the plant's cycle progresses. The rest of the time it would use no more power than needed. At the correct room temp it would be mainly the lights fans, heater and water pumps

Water isn't a very efficient refrigerant.

ANC · Nov 15, 2017

It would only cycle heat to very large heatsinks with fans and water blocks, with high power Peltier coolers sandwiched in between. I'm sure it will require lots of tweaking as it requires going outside of my skillset.

I need to think out of the box as our temperatures vary by up to 45 degrees C in a year and over 20C on some days so aiming for ambient temperature with pure air cooling is futile.

James Eaves · Nov 15, 2017

ANC said:
I will soon be testing the limits on this. I realised what a hard time (high cost) we have doing a relatively small room.
I decided I would test a new approach building a module that grows just one plant at a time. The incoming air temperature will be modulated by two peltiers set up to warm and cool alternatively, on the same radiator, cold will be "pumped" from external peltier using water or mineral oil. Internal airflow should mainly be to distribute the temperature and humidity evenly as we are pumping the heat out separately. Plants will be in temperature controlled hydro or aero, lights will have water cooling transferring the heat to more external peltiers, where the heat will be given off to the atmosphere and condensation collected where it cannot harm electronics. It leans well to tinkering with fully sealed and CO at a later stage. Each tube should be able to produce about 2 to 3 ounces at a minium.

Everything is to be controlled by a microprocessor (I still do old-school assembly language), so (power hungry) peltiers only come on when the fans on the external coolers can no longer keep up with the baseline room temperature being too high.
Not sure about the luminaire design yet, it needs to be able to move up and down in the tube while connected to 2 water pipes as well as the two wires for the COB/s (considering using 2 at half power for redundancy).This thing will be a consumption beast when summer heat strikes, but it would bite off no more than it can chew and inside the thermally insulated tube, conditions for the plant should be as close to ideal as possible from start to end. The only thing you should be able to fuck up is nutes in the reservoir and setting light levels as the plant's cycle progresses. The rest of the time it would use no more power than needed. At the correct room temp it would be mainly the lights fans, heater and water pumps

So you would potentially fill a room with lots of different modules. The hope would be that the gains from reducing the square footage that you need cool or heat, plus potential gains in quality from more precisely controling the climate of each plant, would compensate for the additional cost of building individual modules. Of course, it will lower outbreak risk as well. Why do the lights need to move up an down?

ANC · Nov 15, 2017

I don't want a short tube with the lights very close to the plants all the time, but during the last week of flower, we come a lot closer with our cobs to drive production. Heat will be produced there no matter how well you thermally insulate and vent the light modules. Was thinking of using the glass pane from an outdoor security lamp as the face to my light module, I want the active bits insulated and temperature controlled, so I don't have to vent as much air to deal with this.

I want to be able to emulate this. The tubes can be standing where ever, indoor, outdoor, doesn't really matter. The goal is to be able to grow weed using a portion of the power that would normally be wasted running HID to run cooling at the expense of the immediate surroundings EVEN WHEN IT WOULD OTHERWISE NOT BE FEASIBLE DUE TO CLIMATE EXTREMES. The more I work with the design the more things change. If a component is active in thermal management, it needs to be insulated way from dumping any heat into or taking any coolness out that is not a part of its design function. Chillers will also remove humidity out of the air. they frost over in no time flat under no load.

A big change I made today, is to not try to cool a large volume of air and then pumping it out the other side a second later.
The chillers will now still have fans, but will have nothing to do with the incoming air for venting as required. Venting more air is seldomly the solution or answer to any growing issue.
The smart grower will vent the minimum amount he can get away with while still supplying adequate CO2 for the light levels employed and controlling humidity

Climate control efficiency and room size

James Eaves

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SchmoeJoe

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ANC

Well-Known Member

SchmoeJoe

Well-Known Member

ANC

Well-Known Member

James Eaves

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ANC

Well-Known Member

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