7. Efficiency, Energy, and Entropy
Source: ebook ch. 5 (“Systems Efficiency & Energy”).
Chapter 2 (02-system-fundamentals.md) defined a function purely
as input → process → output, deliberately deferring one question: what is the system
processing, and how well does it do it? This chapter fills that gap.
Resource and entropy
- A resource is a stored form of energy — an ordered structure that enables a system to perform work. Examples: food metabolized by humans to fuel their bodies; petroleum, where energy is stored in chemical bonds.
- Entropy is the opposite of energy: the incapacity to perform work, and a measurement of the degree of disorder within a system. Where a stored form of energy is called a resource, a stored form of entropy may be loosely equated with the term waste. Example: a vase that has fallen and shattered — its parts are now arranged randomly, incapable of serving their intended function.
A resource can be understood as anything that provides the system with the capacity to do work; inversely, entropy is anything that reduces the system’s capacity to function.
Energy and entropy are typically measured using information theory: the degree of order or disorder within a system is measured in terms of the information correlation between its constituent elements — the more patterns there are between the parts, the less information it takes to describe the system, and the more ordered it is said to be. Thermodynamics studies energy in relation to heat specifically; energetics studies energy more broadly across all physical systems, and is closely related to systems theory.
Productive vs. consumptive functions
A system’s functioning can be either productive or consumptive:
- Productive: the system takes in a resource from its environment and performs work on it by transferring energy to it, outputting a resource of greater value than it took in. Example: simply lifting an object off the ground — we input an object at low potential-energy state and, by transferring energy to it (lifting), output an object at a higher potential-energy state: a resource with greater capacity to perform work than before the operation.
- Consumptive: the reverse — the resource that was input transfers its energy to the system, which conserves that energy internally while outputting entropy (waste) to its environment. Example: digestion in mammals — food is input, energy is extracted from it, and a waste product (excretion) is exported.
Systems efficiency
Systems efficiency is defined as the ratio between the energy inputted to a system and the energy outputted by it.
Crucially, what counts as “energy” and what counts as “entropy” is not objective — it is relative to the system’s environment and to what we’re asking the system to do. Example: a lightbulb consumes electricity (input) and produces light (output). Not all the electricity is converted to light — some becomes heat. With respect to the lightbulb’s function as a light producer, that heat is waste (entropy). But if we’re interested in heating the house, that same excess heat may instead be considered a resource.
Understanding this relativity requires stepping outside the system itself and thinking about its
environment and the interactions between systems — which is exactly the transition made in
03-boundary-and-environment.md.