This investigation was conducted to determine the indicated annual savings which could be expected from the proposed installation of a 5000 Kw turbo-generator unit in the Virginia Polytechnic Institute Heating and Power Plant. These savings were determined by comparing three proposed plans of generating or purchasing electric power while supplying the college with steam.

The daily log sheets and flow meter charts of the plant were used to determine the electric load curves and the steam demand curves for the year 1952. These curves were projected into the future to include the years, 1956, 1957, 1958, and 1959. These curves, together with performance curves for a 5000 Kw three stage extraction condensing turbo-generator were used in the investigation. The average outdoor temperature days were grouped in 5°F increments from 20°F through 70°F. A set of four daily load curves was plotted for each 5°F increment. Curve No. 1 shows the total electric load on the system. Curve No. 2 shows the steam demand on the plant when the proposed 5000 Kw three stage extraction condensing turbo-generator is carrying the total electric load while extracting the heating and process steam. Curve No. 3 shows the electric power that the proposed 5000 Kw two stage extraction back pressure turbo-generator would generate while meeting the heating and process steam demand. Curve No. 4 shows the total heating and process steam demand.

The area under curve No.1 represents the total electric load in kilowatt-hours on the system for a day. The area under curve No. 4 represents the total heating and process steam demand in pounds for a day. The daily cost of plan No. 1 was obtained by multiplying these areas by their respective scale constants and then adding these products. The area under curve No. 3 and under curve No. 1 where curve No. 1 is below curve No. 3 represents the electric power in kilowatt-hours that could be generated by the proposed back-pressure unit. The daily saving of plan No. 2 was determined by multiplying this area by its scale constant. The daily cost of plan No. 2 was obtained by subtracting this saving from the daily cost of plan No. 1. The area under curve No. 2 and curve No. 4 where curve No. 4 is above curve No. 2 represents the steam demand in pounds for a day of the condensing unit carrying total electric load while extracting the heating and process steam. The daily cost of plan No. 3 was obtained by multiplying this area by its scale constant. The daily saving obtained by using the extraction condensing turbine over the plan of purchasing all the electric power was determined by subtracting the daily cost of plan No. 3 from that of plan No. 1. The daily saving obtained by using the extraction condensing turbine over the back-pressure turbine was determined by subtracting the daily cost of plan No. 3 from that of plan No. 2.

The yearly costs and savings were determined by multiplying the daily costs and savings by the number of days in each group of average outdoor temperature days and adding these products. The expected yearly saving of plan No. 3 over plan No. 1 for 1956 would be $137,400.00, for 1957, $147,600.00; for 1958, $158,000.00 and for 1959, $171,300.00. The expected yearly saving of plan No. 3 over plan No. 2 for 1956 would be $64,300.00; for 1957, $73,200.00; for 1958, $79,900.00 and for 1959, $93,300.00.