The thermal object is intended to be a singleton (that is, one thermal object per model), including all of the relevant economic information and linked to all of the power reservoirs. The thermal object provides an economic evaluation for the entire RiverWare model. In addition to economic evaluation, the thermal object is a useful place to summarize the power data of a model. The thermal object has many power related multislots and each multislot can be linked to the individual power related slots on the power reservoirs in a model. Figure 27.1 shows a red thermal object linked to power reservoirs. Like all links, these links may be hidden, dotted, or displayed in a different way to change the relative emphasis of the links in the model. See Display Groups in User Interface for details on link groups.

These linked multislots then provide the system totals for these power attributes. Some of the power attributes that may be linked include hydro generation, hydro capacity, pumping generation pumping capacity, and energy in storage. See the full list of multislots below for more detail.

A thermal object may be used with any of the controllers: Simulation, Rulebased Simulation, or RPL-based Optimization.

In a simulation or rule-based simulation model, a thermal object provides an economic evaluation of a solution, but does not influence the solution. An important difference with many other object classes is that the only calculations performed during the timesteps of a run are the multislot totals. All of the economic calculations are performed at the end of the run, after simulation has set all of the other slot values. One consequence of this is that the economic calculations cannot be used to drive a simulation model.

The thermal object is used in most optimization models, because economics is usually a factor in these models. Unlike simulation, in optimization the thermal object can influence the solution. In addition to allowing a modeler to maximize the economic value of hydropower, the thermal object allows a modeler to write constraints and objectives on the power related multislots. For example, total system hydropower generation or capacity can be maximized or constrained to meet a minimum level.