Engine Plant Cuts CO2 and Energy Costs with Cogeneration
Pratt & Whitney’s Middletown, Conn., jet engine manufacturing, assembly and test facility faced a number of operational challenges in its plant powerhouse. The existing boilers burned only #6 fuel oil and were oversized for current steam requirements, resulting in inefficiencies. Boiler maintenance and repair costs were increasing, and it was becoming more difficult to meet ever-changing environmental requirements. Electricity and energy prices were rising, and the state of Connecticut offered opportunities and incentives to help offset capital costs of “behind the fence” generation. The company also recognized intrinsic efficiency and security benefits of cogeneration.
The facility decided to replace two Erie City Boilers (100,000 pounds per hour) that had been built in 1956 and a Keeler Boiler (150,000 pounds per hour) installed in 1975 with a Solar Turbine Taurus 70 combined heat and power (CHP) plant and an associated heat-recovery steam generator. The CHP plant can produce 7.5 MW. Two quick-start Rentech boilers (40,000 pounds per hour) also were installed to balance the steam load. “This new line-up of equipment provides all our steam needs and nearly two-thirds of our annual electricity requirements of 90 million kWh at the site,” says Mark Kopera, Pratt & Whitney energy services manager. Natural gas replaced #6 oil as the primary fuel, with #2 oil as an alternate. “This environment-friendly solution reduced our greenhouse gas footprint by over 10% in just one year and has been operating since January of 2008,” says Kopera.
The turnkey installation project, designed and constructed by Carrier Corp., was completed in 12 months after breaking ground. The compressed timeline required significant efforts on all parts to find innovative ways to install the equipment. For example, the enclosure building was fabricated after the turbine was set in place, eliminating nearly three weeks of rigging time, and the turbine and associated hardware were delivered early and placed in nearby storage to speed site installation. Critical path analysis determined when overtime was necessary to keep elements either on or ahead of schedule.
Waste heat from the cogeneration facility is piped directly into the existing steam distribution system and is used for heating, process and air-conditioning loads. The unit also reduces the need for operating labor and eliminates the costs associated with maintenance and repair of the old, inefficient boilers. Other savings were realized from no longer having to continually heat fuels in the storage tank, lack of acidic condensation in the stack, energy savings of new highly efficient pumps and motors, and reduced emissions fees paid to the state department of environmental protection.
The savings the CHP unit generates yield an overall internal rate of return greater than 20%, and a simple payback in the range of five years. Demand for electricity from Connecticut Light and Power is reduced by more than 60%, and the CHP unit also qualifies for production subsidies for producing electricity from renewable sources. The Renewable Energy Credits it obtains for producing electricity can later be sold on the market. This practice generates close to $1 million in additional revenue for the company.
Aside from the cost savings and greenhouse gas reductions, operating these unites during peak demand periods offers a significant community benefit. As Pratt & Whitney is able to generate most of its own power, the power they would have taken from the grid can be directed to other higher-priority uses such as local hospitals, educational institutions and community centers. This distributed-generation model can minimize or even eliminate the risk of a brown-out or black-out in the community. “Our employees also actively participate in these events by reducing power consumption in their work areas during these periods of high consumption,” Kopera adds.