Technical University of Denmark
A bioreactor that runs on its own
- PID control
A bioreactor that runs on its ownTechnical University of Denmark
A PID loop brought the water to about 19.4 °C and held it within ±0.1 °C, with nobody on site.
The work
Keep live mussels in a bioreactor for six days with nobody tending it. The water started at 17.9 °C and had to reach its setpoint and hold there on its own.
Technical University of Denmark · Health Technology · 2025 · Grade 12/12 · Team of 10
What I found
With the water held near 19 °C, the mussels opened their shells as soon as they went in and stayed open for the whole run.
What I did
- 01Owned the temperature control, a PID loop on the water.
- 02Tuned it from a step-response test: modeled the cooling as a 20 s delay and a 533 s time constant, then set the starting gains with Ziegler–Nichols.
- 03Brought it from 17.9 °C to about 19.4 °C and held it there for six days.
- 04Led planning for the ten of us.
Results
- ±0.1 °C typical, ±0.5 °C at worst
- 6 days unattended
- 33% less cooling energy with sand as insulation
Siphon test: about 20 L/h through two pipes
OD sensor design
Electronics
The whole setup
Shells open