In 2000 the STEC models were updated to be fully compatible with the new TRNSYS15 and Iisibat3. This work was mainly done by former TRNSYS engineer Nathan Blair, working under Prof. Beckman at the University of Wisconsin, Madison. In early 2001, parts of the STEC library were successfully validated with measurement data from the SEGS VI plant, a commercial solar thermal power plant in the Californian dessert.  While agreement between the simulation and actual plant data was generally within 10%, there was difficulty in modeling solar field flow rate during transients.  Later that year, Thorsten Stuetzle, Prof. Beckman and colleagues at the University of Wisconsin performed a ground-up analysis of the problem and developed a dynamic solar field model and new control algorithms that can both better model existing plant behavior and offer the possibility of more stable field outlet temperatures if implemented in place of human control.  This work was initially performed in the EES simulation environment, but will be transferred to TRNSYS.

In September 2002 the completely revised version 2.2 of the STEC library was released containing a number of new models in the brayton, rankine and solar thermal subsection.

Today, the STEC library is distributed to more than 30 institutions world wide. The models are used in research and development as well as in commercial projects. One impulse of interest was the free distribution of the STEC library also to non-SolarPACES members in 2003. But lately, with numerous commercial solar thermal power projects emerging -mostly in Europe and the U.S.- the interest is even increasing and moving from public research to private business institutions.

CONTENTS, DESCRIPTION, VALIDATION

The STEC model library is subdivided into a Rankine section, a Solar Thermal Element (STE) section and a Brayton section. The Rankine section consists of various models to simulate a complete steam turbine cycle: Preheater, Economiser, Evaporator, Turbine, Condenser and several utility components like pumps, steam splitter, controller, etc. All these are zero capacitance models with quasi steady-state behaviour. A thermal capacitance model can be linked to include thermal 'inertia' to the system. The STE section contains models for concentrating solar technologies: A parabolic trough field model working with a one phase fluid. For solar power towers there is a central receiver model and a heliostat field model using a field efficiency matrix which can be derived from other computer codes for calculation of heliostat field layout (e.g. DELSOL). Additionally there are models for high temperature thermal storage systems like thermocline storage and concrete/oil storage. The Brayton section offers models to simulate in detail arbitrary gas turbine systems: compressor stage, combustion chamber, turbine stage, hydronic and control elements.