Belimo Energy Valves take control of ∆t
Retrofitting Belimo Energy Valves to control the flow of chilled water to coils in five air-handling units in the Charles Hayden Library of the Massachusetts Institute of Technology has nearly doubled the temperature drop (∆t) across the coils and reduced the flow of chilled water by 49% — massively reducing pumping energy. According to Peter Cooper, manager of sustainable engineering and utility planning at MIT, applying the same fix across the institute would save $1.5 million a year.
Surveys had shown that coils throughout the library had average ∆t readings of 3.4 K, resulting in far more water being pumped than was necessary or even advantageous. Reasons for this small ∆t included fouled coils and the AHU control logic relying on inputs from air sensors.
One benefit of the Energy Valves was to avoid coils becoming power saturated and unable to transfer any more energy, no matter how great the flow, wasting pump energy. The Energy Valves provide precise pressure-independent flow regulation by monitoring the ∆t across the valve and adjusting flow to achieve the desired ∆T. The ∆T was increased to 6.7 K, reducing the flow of chilled water by 49%.
The project convinced Peter Cooper of the value of data: ‘Having such intelligence on the valve actuator means you can characterise a coil’s performance with just a couple of pieces of data. With that information, you can observe the degradation of coils and refocus your maintenance efforts accordingly.’
