For technologies with a TRL/MRL of only 1-2 (observation of basic principles and formulation of concept), theoretical values or "back-of-the-envelope" estimations can be used. For example, a 100% thermodynamic conversion efficiency could be used for mass flow simulation, and industry averaged capital or utility costs from a similar technology could be used as an early estimate for capital and operating costs. If "proof-of-concept" studies have been conducted