An economic study of turbo-generator units to meet the future demands of the Virginia Polytechnic Institute heating and power plant

This investigation was conducted to determine the indicated average heating season saving which could be expected from several different size turbines with different throttle conditions and varying stages of feedwater heating when operating in the Virginia Polytechnic Institute Central Heating and Power Plant. Such a saving in cost of power produced locally is possible because of the higher cost of power when purchased from the Appalachian Electric and Power Company. This investigation covers the heating season of 1966-1967, and assumes that the present turbo-generators will not be in use at that time.

The electric load and steam demand load for the average heating season day of 1952-1953 were taken from existing records and were projected into the future to the heating season of 1966-1967. Two values were used as factors to project the steam demand into the future because of the uncertainty of the future college expansion. From this data electric load versus time curves and steam demand versus time curves were plotted for the average heating season day. This information, together with steam rates and exhaust rates for one, two, and three stage feedwater heating cycles for each proposed turbo-generator unit was used. Four curves were plotted for each throttle condition for the average heating season day in order to determine the kilowatt hours which could be generated by each proposed unit of sufficient size to supply the expected future steam demand. These curves were: Curve No. 1, the expected total electric load; Curve No. 2, the expected electric power generated by the proposed unit with one stage feedwater heating; Curve No. 3, the expected electric power generated by the proposed unit with two stage feedwater heating; Curve No. 4, the expected electric power generated by the proposed unit with three stage feedwater heating. The areas under curves two, three, and four represent the kilowatt hours which could be generated by the proposed unit supplying the expected steam demand.

The value of these areas in terms of dollars saved was determined by multiplying the areas, in square inches, by a scale constant, 1000 Kw-hrs per square inch, and by $0.008 per Kw-hr minus the fuel cost per Kw-hr. The value $0.008 is the minimum rate of energy paid by the college for purchased power from the Appalachian Electric Power Company. The resulting figure represented the average daily saving for the heating season. This figure was used to calculate the total saving for the heating season.

The indicated savings which might be expected for the heating season of 1966-1967 ranged from $89,000.00 for a throttle condition of 250 psig. and 500 F and a 3750 Kw unit with one stage feedwater heating to $249,480.00 for a throttle condition of 1200 psig. and 950 F and a 9375 Kw unit with one stage feedwater heating. The results for each throttle condition and turbine with varying heater stages are tabulated in part C of the investigation