4.4. Combined cycles / Cogeneration¶

4.4.1. Combined cycles¶

In Gas turbine, an important part of energy is loss with exhausted combustion gases. This energy can possibly used as hot source for a vapor turbine. We then talk about combined cycle.

4.4.2. Cogeneration¶

Finally, whatever the heat engine is, thermal energy is provided to a cold sink. Cogeneration consists in using these residual energy for a heating system. By the way, the installation produces mechanical work and heat. The global efficiency of a cogenerative installation may be evaluated by:

$\eta_{cogen} = \frac{-\dot{W}_t + |\dot{Q}_{recup}|}{\dot{Q}_C}$

With $|\dot{Q}_{recup}|\leq \dot{Q}_C$ .

These installation may reach 70 to 80% or efficiency.