thermOS is a smart HVAC system to replace the outdated pneumatic HVACs in Porter Hall.

Executive Summary

We decided on doing a project still related to HVAC systems. This project allowed us to do what existing products to but add more functionality. The ultimate goal of these smart HVAC systems is to save energy. We also wanted to add analysis for the sensing data. For our controller we used a Raspberry Pi. Being a microcontroller not only can we take sensing input, set the fan speed, and control the actuators for the heating and cooling valves but also connect to a server where data is stored. With OSI/PI we can store and process sensing data sent from the controller and make decisions based on what is occurring. This data can eventually be generated into reports that can give insight on how the system is working. To keep things simple we started working with just temperature and occupancy data. Based on a desired temperature and tolerance the microcontroller activates the heating or cooling valves and then sets the fan speed to enforce this temperature. This sequence of events is triggered by the motion sensor. Additionally the microcontroller takes into account GPS location, another common feature of existing products. We introduced this through a mobile application. Based on distance it will activate the control flow described earlier. This application is the manual override for the controller and is a convenient way for monitoring the state of the system.

An inside look

The main components of the controller is the fan control, the actuator control, and the sensors. The fan control operates using relays to switch between the different fan speeds to regulate airflow. The actuator uses PWM to modulates a voltage source to rotate the hot and cold air valves. The sensors read the temperature and occupancy in the room as inputs for the control scheme.

Security and Future Development

We also attempted to tackle some of the privacy and security issues related to this. If our solution takes into account things such as location and times of usage, we have to keep it private or only expose it as much as the user wants. Using the rooms in Porter Hall as an example, most of the thermostats in Porter are pneumatic which leaves little room for control. There’s a need for smarter control of the HVAC systems that isn’t manual. Our goal is to establish a system that allows not only control but also monitoring of all rooms with the controller. With this done the next step could be scheduling the rooms to be at set temperatures during the day. In the future someone may be able to build a centralized controller which can be able to flatten out the energy consumption of the building.