De Muur, spijkers en boeven vangen volgens plan

De Muur viel in 1989, in 1992 had de Sovjet-Unie opgehouden te bestaan en daarmee was ook het politiek-economische regime van centraal geleide planning daar ten einde. Je moet het een nieuwe generatie, de generatie die het niet meer zelf (van dichtbij of uit de verte) heeft meegemaakt, uitleggen: Weet u (weet je), vroeger, maar nog niet zo lang geleden, was er een land, een rijk eigenlijk, dat de Sovjet-Unie heette

System Performance and Testing

This chapter compares and contrasts the system performance of two widely used solar thermal systems using testing and simulation programs. Solar thermal systems are used in many countries for heating domestically used water. In addition to the simple thermosiphon systems, better designed pumped systems with new operational strategies are becoming available. "Low-flow systems" achieve higher system performance than standard "high-flow systems." To compare system performance, objective criteria must be defined. The preferred criteria are the fractional solar savings that represent the solar gain compared to a non-solar reference system. Simulation programs with different levels of sophistication are used to estimate the yearly solar gain of a particular system. Using detailed models, systems simulation is used to evaluate the performance criterion for accelerated aging tests on the basis of materials properties. CEN and ISO test methods, which are used for performance testing of the systems, are compared and applied to systems of various sizes. © 2004 Elsevier B.V. All rights reserved