Using a MEMS microvalve as a pilot for a traditional spool valve is analogous to using an accelerometer to trigger an airbag--the idea being that the MEMS element just senses conditions, then fires off a signal to the traditional "reaction" circuits to fire the airbag, in the case of accelerometers, or to turn up/down the flow in an HVAC in the case of a microvalve. The MEMS sensor just does a better job of sensing and responding, not actually performing the macro-sized action.
An interesting development - that a controller of a controller improves economy and saves space. Certainly there is a huge market for more cost effective and reliable HVAC and automotive systems.
How is it "that switching to its micro-valves can increase the efficiency of existing HVAC systems by as much as 25 percent, making the technology good for retrofits"?