Eff of Cogeneration & Absorption Machine
Eff of Cogeneration & Absorption Machine
(OP)
We have a 600 kW NG CoGen plant and all heat produced (H2O and exhaust) is wasted. We also run a NG direct fired absorption unit for chilled water. We are looking into the feasibility of retiring the existing unit and installing another absorption unit that can run off of the waste heat. Does anyone know about the efficiency of the units? In other words, BTUs of Cooling Out vs. BTUS of Hot Water IN.





RE: Eff of Cogeneration & Absorption Machine
This depends on the quality of the waste heat.. temp mostly. See a chiller vendor for details.
RE: Eff of Cogeneration & Absorption Machine
I just did a project with cogen waste heat and the new absorption units run at highest efficiency at 175F waste water temp, very much lower than the old ones that required 210-220F.
Given that you're paying for the NG absorption and not for the recovered heat absorption, the efficiency increase is 100%. Other than this, efficiencies are vendor-specific; speak to a salesman.
RE: Eff of Cogeneration & Absorption Machine
If the efficiency is 1/2 Btu/hr per 1 Btu/hr input, you are still ahead of the game as the input is waste.
If you plant is a cogen, would that imply you are using exhaust gas to produce steam to produce electricity through a steam boiler? If so, low grade steam would work well in an absorption chiller, likely better than exhaust gas.
RE: Eff of Cogeneration & Absorption Machine
RE: Eff of Cogeneration & Absorption Machine
With NG at $6-10/million btu, capital paydown without regard to efficiency will probably be less than 3 yrs.
RE: Eff of Cogeneration & Absorption Machine