TRNSYS (Transient System Simulation Program) is a software program used to simulate energy and power systems over time. It can be used to simulate the behavior of a wide range of energy systems, including building systems, solar systems, district heating systems, and the energy grid. It is a powerful tool for engineers and researchers to analyze the performance of energy systems. TRNSYS integrates a variety of simulation techniques and provides a comprehensive interface to analyze system performance at various time scales. It has many features such as a graphical user interface, a library of component models, a data visualization tool, and many more. TRNSYS is widely used in the energy industry for research and development, system design, and control optimization.
EES is a solver, as TRNSYS is a block simulation software.