Cogeneration system design tools
Design and Optimization of Combined Heat and Power (DOCHP): A New Tool for Building Integrated Energy and Thermal Generation Set Analysis and Optimization
Building integrated cogeneration systems (e.g., combined heat and power, or CHP, systems) can provide for increased on-site energy resource efficiency through the simultaneous production of electricity and useful thermal energy from a single source of fuel. Current methods for both design sizing and performance optimization for combinations of cogeneration systems and commercial buildings lag behind the tremendous advancements that have been made in building performance simulation methods. Thus, it is necessary to develop and apply an improved integrated systems analysis tool for optimizing the complex operation of the generation set(s) that are continuously subject to load variations at off-design conditions at the building and/or campus scale. This work describes the development and application of a new Design and Optimization of Combined Heat and Power (DOCHP) systems optimization and analysis tool. DOCHP combines generalized natural gas generation set performance curves and hourly building energy simulation outputs to model the dynamic part-load operation of a generation set based on hourly time-step thermal and electrical load profiles. The generation set control programming is load-based; therefore, the energy balance in the cogeneration system model is dependent on the instantaneous partial loading coincident to key generation set performance parameters (e.g., the heat-to-power ratio, HPR, and electric heat rate, EHR). The DOCHP tool uses hourly thermal and electrical load profiles from energy simulations as input parameters and optimally sizes generation sets by minimizing annual greenhouse gas emissions, fuel and energy costs, and/or annual source energy consumption.
The DOCHP tool combines generalized non-linear natural gas generation set performance curves and hourly building energy simulation outputs to model the dynamic part-load operation of a generation set based on predicted hourly thermal and electrical load profiles. The tool is built as a single Microsoft Excel workbook comprising a series of transparent input, output, and data worksheets. The tool includes a graphical user interface (GUI) to provide the user with a selection of the following inputs based on their application needs: location-specific annual average energy and fuel costs, with 2014 Energy Information Administration (EIA) data as the default; power grid subregion greenhouse gas emission factors, with default values from the Emissions & Generation Resource Integrated Database (eGRID); part-load generation set performance curve approximations, with generic equipment curves as default; auxiliary heating plant efficiency, operational mode, and a generation set minimum turn-down ratio; auxiliary heating systems; and cogeneration operation mode (e.g., electric or thermal load following).
Download – DOCHP_V01_beta