Trigeneration, also called CCHP (combined cooling, heat and power), refers to the simultaneous generation of electricity, useful heating and useful cooling from the same original heat source such as fuel. Waste heat insufficient in energy to produce electricity through mechanical means, such as through a steam turbine, contains usable energy that is harnessed for thermal regulation purposes as described in cogeneration. Trigeneration differs from cogeneration in that some of the waste heat is used for cooling. CCHP systems can attain higher efficiencies per unit fuel than cogeneration or traditional power plants.

Another field of activities in building department is utilization of CCHP systems. Considering low efficiency of thermal power plants, need for reducing electricity dependency, conservation of fuel consumption and subsequently reduction of air pollutants made managers pay special attention to CCHP matters.

As a result investigation feasibility studies for four sites including "MahmoodAbad Complex", "Ahvaz and Tehran petroleum hospital" and "Ahvaz Oil Company" has been performed. At present, studies for purchasing and installation the system for "Ahvaz petroleum hospital" is carrying out.