College of Wooster

Cogeneration System

| College of Wooster | Wooster, Ohio |

Overview

Cogeneration is the use of a primary energy source to produce more than one useful form of energy. Robert H. Fuller & Associates, Inc. analyzed existing conditions at the College of Wooster and designed a system which utilizes steam produced from a coal-fired boiler to provide beating and electricity to the Campus. The system is a packaged unit: a turbine-generator set in parallel to the steam pressure reducing valve station at the College's Central Heating Plant. The unit is a 375 kW, topping cycle, backpressure turbine driving an induction generator set. The handvalves on the turbine are automated to allow the unit to maximize output as steam flows fluctuate to meet steam requirements on campus. The automated handvalves are operated in reference to generator speed and turbine backpressure.

This project was an energy conservation measure which was eligible for federal grant funds through the Department of Energy's Grant Program for Schools and Hospitals, also known as the Institutional Conservation Program (ICP). Robert H. Fuller & Associates, Inc. completed the necessary study and grant application for the College, and was successful in securing a 50% federal grant for this project. The turbine/generator set has been estimated to produce 1,280,000 kWh/yr while burning an additional 145 tons/yr of coal. The estimated cost avoidance for the College is $50,000. The project cost was $233,000, creating an overall simple payback of 4.7 years. The payback for the College with the 50% grant was 2.3 years.

Project Details

The College of Wooster's Central Heating Plant was operating a primary coal-fired boiler (40,000 lb/hr capacity) to produce saturated steam at 175 psig. The steam passed through a pressure reducing valve (PRV) station and was distributed to the campus at 25 psig. The steam was only used for heating and absorption cooling in the campus buildings (1,100,000 gross sq. ft.).

While conducting energy survey work for the College as a part of the College's efforts to conserve energy, Robert H. Fuller & Associates, Inc. noted the potential opportunity for cogeneration. The PRV station function is necessary, but potential energy available to do work was being wasted. A cogeneration project was incorporated into a technical assistance study which became a part of a federal grant application for project funding.

The economic analysis was based on a unit which was sized to operate twelve (12) months per year with the existing steam conditions. Hourly steam flows for a twelve month period were analyzed utilizing the boiler steam flow charts. The Engineer was able to arrive at an estimated kWh output by utilizing the steam flow data and the Willan's curves. The estimated electrical production is l,280,000 kWh/yr, which is approximately 10% of the campus consumption.

The study and grant application were submitted to the Department of Energy. The project was successful in securing 50% funding for design and construction.

Once funding had been secured, Robert H. Fuller & Associates, Inc. designed and provided construction documents for a cogeneration system for the College of Wooster, which consisted of a turbine/generator set in parallel with the PRY station at the Central Heating Plant. Three (3) Prime Contracts were awarded for the Construction Phase:

The purchase and start-up service of the unit was bid as a prime contract providing the owner with direct access to and control over the contractor who was the manufacturer of the unit. Construction and start-up were completed on time. The project cost was within 0.5% of the estimate. The unit was officially brought on line October 1, 1992 and has operated with minimal manual intervention since that date.

The unit is a packaged 375 kW, topping cycle, backpressure turbine and induction generator set. The unit follows the steam load demand of the campus and produces full capacity at 23,500 lb/hr steam flow. The unit was designed to maintain the campus steam distribution conditions.

The turbine is a single stage, multivalve unit with three inlet ports. The factory handvalves which are normally manually operated to control the amount of steam allowed to pass into the inlet chambers were replaced with three (3) automated valves with pneumatic actuators. These valves are operated through a combination of Power and Woodward controllers. The combination of controllers make it possible to reference and adjust multiple setpoints. Two (2) setpoints are used for this installation:

Automated handvalves are not common on turbines in this small size range. The manual operation of the handvalves was neither practical nor acceptable to the College because of the unit being remotely located from the main operating level. This unit was designed with automated handvalves to allow the turbine to operate more efficiently by maximizing the turbine output while also very closely following the fluctuating steam flow requirements of the campus.

The unit can be controlled from two (2) locations: a main control panel adjacent to the unit on the heating plant lower level and a remote control panel located on the boiler operating level. The unit can only be started from the main control panel. All other system functions can be controlled at either location.

Steam separators are installed on the turbine inlet and outlet piping. The inlet separator protects the turbine blades from water droplet damage. The outlet separator maintains the quality of steam entering the distribution system.

The generator is a 500 HP, 3 phase 4160 volt, induction motor operated in overspeed. The generator is excited by Utility power which eliminates the need for synchronizing equipment. The rated speed of the motor is 3600 rpm. The generator is run at 3610 to 3632 rpm. The generator is connected in parallel with the Utility through a vacuum circuit breaker. The circuit breaker includes all protective relaying required by the Utility and for the unit protection. Capacitors are connected in parallel with the generator to provide power factor correction. (The large motor has poor power factor at partial loading). The circuit breakers on the generator and the capacitors are interlocked such that when the generator circuit breaker closes the capacitors are also brought on line.

The Robert H. Fuller and Associates, Inc. design team included:

Principal in Charge / Mechanical Design - Gary S. Ash, PE
Project Manager / Electrical Design Robert J. Cameruca, PE
Mechanical Design / Controls - Michael J. White, PE
Quality Control - Walter L. Hartman, PE

| District Energy in Ohio |
HTML by Morris A. Pierce
29 March 1996