Session: 3.2 - Plant Construction, Supply Chain Mgmt. & Economics & 4.4 - Integrated Energy Systems & Micro-grids

Paper Number: 108708

108708 - Trigeneration System Replacement for a University Central Plant Boiler Facility 

This paper explores a replacement option for the aging space heating boilers at the California State Polytechnic University, Pomona which serves the hot water needs of four buildings. A new system is designed and proposed herein utilizing solar thermal energy, thermal energy storage, and a combined cooling, heating, and power (CCHP) cycle with a focus on efficiency and reduced carbon emissions. A reheat Rankine cycle acts as the energy production cycle for this system. The proposed Rankine cycle also has a low stage steam extraction system paired with a lithium bromide cycle to produce heating and cooling. The primary source of high grade input heat energy for the Rankine cycle will be a set of solar troughs placed on the site of the former dorm houses. These solar troughs will heat oil to high temperatures, this hot oil will then be used to boil water to produce steam in a boiler. This system will rely on a steam extraction system that draws saturated steam from the low stage turbine in the Rankine cycle. During times of high heating demand, steam will be drawn off to drive a lithium bromide cycle. This cycle will produce both cooling and heating with a COP of roughly 1.5 for heating and 0.75 for cooling. By this method, this system can offset electrical energy demand, space heating demand, and space cooling demand simultaneously. This will allow for greatly reduced resource costs and carbon emissions. This paper also presents the analysis of the required boiler including capacity and temperature plots. All components were selected to meet the required capabilities of the system. Further analyses were performed to identify an adequate pump solution to drive the pressure gradient required for Rankine cycle operation. Condenser analyses were also performed to ensure that a correctly sized condenser is present in order to ensure proper heat rejection from the system. The design of this system was optimized by the utilization of NREL SAM, MATLAB CoolProp, and Mathcad. The facility described herein was designed to produce up to 1.565 MW of electricity, 813.54 tons of heating, and 220 tons of cooling. This system will utilize an 11-acre solar facility to be located on the site of the former dorm units at the university. The solar field will be capable of producing 4.260 MW of thermal energy which will be used to drive the reheat Rankine cycle. Equipment selection and specification was performed in order to identify off the shelf components that can be used in the construction of this system. All components including the turbine, condenser, boiler, and pump were selected to be available off the shelf from primary suppliers.

Presenting Author: Kevin R. Anderson California State Polytechnic University at Pomona

Presenting Author Biography: Dr. Kevin R. Anderson is Professor of Mechanical Engineering at Calif. State Polytechnic Univ. Pomona.