9-6. A steam generation system at a biomassfueled power plant uses an electrostatic precipitator

(ESP) to clean its gaseous effluents. The power plant has consistently made use of the same type of ESP over the past several years. The installed cost of a new ESP has been relatively constant at $80,000. Records of operation and maintenance expenses indicate the following average expenses per year as a function of the age of the ESP.

The MVs of the ESP are also reasonably well known as a function of age.

Year 1 2 3 4 5 O&M expense $30,000 $30,000 $35,000 $40,000 $45,000 Market value 60,000 50,000 40,000 25,000 12,500 Determine the best time to replace the ESP if the MARR is 15% per year. (9.5)