In thermodynamics, exergy is defined as the maximum useful work that can be extracted from a system as it reversibly comes into equilibrium with its environment. Contemplating the built environment, one could define a term “eXergy” as the maximum comfort that can be extracted from an intelligent building as it reaches the optimal equilibrium between efficiency and Quality of Experience (QoE). Or more directly, eXergy is a measure of how well all the energy-driven devices in an intelligent building work together as a system to add or detract from the humans’ environmental comfort.
Context: Intelligent Buildings
An intelligent building should be “able to vary its state or action in response to varying situations, varying requirements, and past experience.” That’s the dictionary definition, by the way, not Pete’s. Oxford Languages also tells us that intelligence is “the ability to acquire and apply knowledge and skills” and that a building is “a structure with a roof and walls.”
By those definitions, intelligent buildings have existed for decades—petrochemical plants, power plants, and myriad other industrial buildings have been built from the ground up with embedded SCADA systems that adjust the plant to produce the maximum output at maximum efficiency—the optimal tradeoff between the amount of energy and material consumed and the amount of oil/electricity/whatever produced. SCADA systems operate by a set of rules derived from past experience according to which the various components of the plant communicate with each other and make adjustments to maintain optimal efficiency without human intervention.
Context: eXergy through Intelligent Buildings
Today’s “smart home” consumer technology largely relies on the resident human to set parameters in some version of a “controller of controllers” that, in the best case, aggregates the user interfaces of various regulators into a unified dashboard to enable remote control of those regulators, perhaps with some automation—for example, setting a thermostat to different temperatures at different times of day. Some “smart” devices contain sensors that trigger an action based on a predefined threshold—for example, a motion-activated light. Each component (light, temperature, air flow, etc.) is separately regulated, either by a numerical rule (like temperature at 70° F) or by human action (like turning on a light when entering a room).
An intelligent building whose purpose is to produce optimal comfort for humans would be designed to connect all the systems and sensors in the building so that they can acquire and apply the knowledge of when the resident human is experiencing maximum comfort and communicate with each other to vary their state in response to changing conditions to maintain that level of comfort in the most efficient way. Can this be done? Yes. All the pieces and knowledge to do it exist today. All that is needed to achieve eXergy through intelligent building is vision and a willingness to overcome the inertia of doing things the way they have always been done.