In this paper a novel concept is introduced for the energetic evaluation of technical systems, based on the law of entropy. Our technical systems are considered as open systems interacting with their environment. Main attention is directed to waste energy as the source for the entropy export necessary to maintain a desired state of order within the system. The entropy export results from internal and external irreversibilities. A reduction of both irreversibilities, i.e. an approach towards a reversible process management, reduces pollution on the environment through entropy export and primary energy expenditure. With that, the strategy developed here and called entropy economy, contributes to a better optimization of technological processes and thus to sustainable development. The most important means for avoidance and reduction of irreversibilities are discussed in detail and applied to definite regional objectives. As examples reveal, from a thermodynamic perspective it turns out that in some cases a considerable amount of primary energy could be saved with the currently known technical methods. Additional expenditures for devices and technical equipment are not the only obstacles for realization: opposition from the realms of economic, social and legal requirements is likely to exert a negative influence on the development of optimally integrated 'cascading' cycles. (C) 2003 Elsevier Ltd. All rights reserved.