Historically, energy conversion was seen as a one-dimensional system, in the sense that one form of energy was converted into another form. By-products of the conversions such as heat were disregarded and/or treated as waste. Cogeneration is a first step towards system improvement since the 'waste heat' is recovered and used as a valuable product. Trigeneration systems, which take the concept even further, are proposed for the simultaneous production of chemicals, power, and heat, and are integrated into larger systems, such as chemical plants, to achieve increased overall performance. In these systems electricity may just be a by-product. However, co- and trigeneration systems are still characterized by a single input. In this paper we further extend this concept and explore the potential role of multi-source multi-product (MSMP) systems. (c) 2006 Published by Elsevier Ltd on behalf of the International Association for Hydrogen Energy.