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Wentworth's Tri-Gen Plant
Wentworth Institute has upgraded their existing, 15-year-old combined heat and power plant to the latest 21st-century CHP technology. The upgraded plant consists of a 12-cylinder lean burn Caterpillar “Hot-CAT”, operating at high jacket water temperatures (up to 260°F). The elevated jacket water temperature allows for efficient thermal transformation into low-pressure steam for the Institute’s HVAC and main plant systems. The system produces 570kw of computer-quality grade electricity and approximately 2800 lb/hour of low-pressure (12 psig) steam recovering all of the engine’s waste heat through a waste heat recovery boiler.
The energy produced offsets the peak electrical demands during its operation for the campus, while simultaneously providing steam that is used for heat, hot water, and cooling during the summer, using the Institute’s existing absorption chiller technology. Through the addition of selective catalytic reduction (SCR) the system will operate well beyond accordance with Massachusetts State Emission levels using the Best Available Control Technologies (BACT). The Greenhouse Gas reductions from the system will be well over 1000 tons per year in CO2 sequestration, the equivalent of planting hundreds of acres of forest every year.
The Institute will also be saving tens of thousands of dollars per year in overall energy costs. The system can be totally controlled remotely through the service bureau that looks after the CHP plant and is set-up to run fully automatic with the Institute’s existing main plant systems.
The upgraded combined heat and power plant also provides a tremendous amount of data acquisition that is available to anyone on campus via the schools intranet; this information will be used by faculty as a teaching tool, providing real time data for students to study. Wentworth is one, if not the only, school in the Commonwealth having real-time data from a Combined Heat and Power system available for classroom curriculum studies over the intranet, as well as wireless throughout the campus for students to monitor and study in real time.
In November of 2008, the Wentworth Central Power Plant went back on line after a comprehensive upgrade had been made to its boiler room. Two new Cleaver Brooks 300 hp low-pressure steam boilers, with the latest CB Hawk energy control packages, were added alongside of an older CB 250 hp boiler that had recently been retrofitted with an energy efficient Limpsfield burner/Auto Flame control package. The Institute’s old over-drafting chimney stack was abandoned for new Selkirk Metalbestos Pressure Stacks. In addition to these energy savings measures, Wentworth added on to each boiler new O2 trim packages, parallel positioning, and variable speed drives onto the blower motors.
The two new CB 300’s can produce a combined 18,700 lb/hr of steam that easily carries the main campus existing peak load of 10,000 lb/hr. The third older CB 250 is for redundancy and is rated for another 8,250 lb/hr. The Cogen conveniently provides an approximate 2800 lb/hr that works well with carrying the steam demand in the majority of the shoulder months for heating and cooling.
The main cooling plant consists of two Trane absorbers, one steam and the other gas fired. The steam-fired absorber at full load can utilize the 2800 lb/hr of steam that the Cogen can put out. The steam-fired absorber can handle the majority of the cooling season with its 170 tons of cooling capacity. Peak load for cooling for the main campus is 200 tons, which means the gas fired absorber, at 300 tons output, can be brought on line either separately or in combination with the steam fired absorber to easily meet demand.