Design of a Cost-Effective Power Plant

Photo of Adam Behrman, Sean Berg, James Svenstrup (Team Leader) Students: Adam Behrman, Sean Berg, James Svenstrup (Team Leader)

Sponsor: Texas Instruments

Date: Fall 2008

Requirements:
The primary requirements and constraints include system economics, performance, and environmental impact. The designed power plant must provide a payback period of no more than 5-10 years and an energy cost of less than $0.10/kWh with an anticipated 5% annual increase. The system must perform at an overall thermal efficiency of greater than 60% at all times. The plant must be sized not to exceed the power load of the manufacturing facility, which is 17-20MW. The plant must be located to fit within the available land owned by TI in Sherman, TX, as well as meet the emissions guidelines for a Texas Standard Permit to operate in Sherman, TX.

Problem:
Our task was to research potential energy alternatives for TI to generate their own power to offset energy costs and recommend a power plant design.

Solution:
The project was complete in three phases. Phase I included research and basic feasibility analysis of various energy alternatives. Phase II included selecting and pricing components for the selected energy alternative, and Phase III included sizing the system, accounting for environmental impact and economics. We selected a natural gas cogeneration/trigeneration cycle and compared using either fuel cells (such as DFC 3000 molten carbonate fuel cells) or gas engines (such as GE Jenbacher JSM-620 reciprocating engines) to provide electric power and waste heat to the subsequent processes within the cycle. To assess the advantages of both options, we performed a cost analysis and considered using multiple fuel cells and multiple Jenbachers to provide either power and heating, power and cooling, or power, heating and cooling. The plant requires a shell and tube heat exchanger for hot water heating to produce 180° F process water for TI using available waste heat. We considered using an absorption chiller for providing chilled water at 42° F for TI using available waste heat. We sized the equipment for the system based on TI's heating and cooling loads, and the amount of waste heat available from the power cycle to cover these loads; this also accounts for installing a power cycle that would not exceed the power load of 17-20MW.
We recommend that TI install a cogeneration system with one gas engine to provide 3MW of electric power, and a heat exchanger to provide hot process water. This particular system results in the fastest payback period, highest rate of return on investment after 10 years, and lowest energy cost ($/kWh) of all the variations of cogeneration/trigeneration considered. This is also the only system variant with a less than 10 year payback that will meet the emissions guidelines for a Texas Standard Permit. The design will also qualify TI for a 10% federal tax credit on installation since the system will operate between 61-84% efficiency; this efficiency depends on the amount of waste heat used (150-310hp for the boiler heating load).

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