energievrij
Energievrij is a Dutch term that literally means energy-free. In practice, it is used to describe situations, products, or systems that operate without requiring external energy input from power suppliers. Because energy needs vary by context, energievrij is not a precise technical category; its meaning depends on what is counted as input (direct electricity, fuel, or energy captured from the environment) and on the boundaries of the system being considered.
The expression appears in several domains. In consumer products, examples include mechanical devices powered by stored
Critics note that the term can be misleading if used without context, since most systems incur energy