Abstract
Combined Cooling, Heating and Power (CCHP) systems have been widely used in different kinds of buildings to make better use of fuels because of their high overall efficiency. This paper presents a mathematical analysis of a CCHP system in comparison to a Heating, Ventilation and Air Conditioning (HVAC) system. The operation strategies following electric load (FEL), thermal load (FTL) and a hybrid electric-thermal load (FHL) are proposed and investigated in this study. Criteria, namely primary energy saving (PES), exergy efficiency (ηexergy), and CO2 emission reduction (CER) are defined to evaluate the performances of CCHP systems for a hypothetical building located in Dalian (China). The results indicate that: (1) a new mathematical foundation is established to find whether the recovered thermal energy and the amount of electricity generated by the power generation unit (PGU) are enough to provide the energy required; (2) the CCHP system does not always perform better than a HVAC system from an instantaneous perspective, especially in FTL mode; (3) the CCHP system in FEL operation mode can be seen as a suitable energy system in Dalian from the annual performance perspective. Furthermore, a sensitivity analysis is presented in order to show how the performances vary due to the changes of various technical variables.
Highlights
Combined cooling heating and power (CCHP) systems, called trigeneration systems, are broadly defined as an energy supply system that generates electricity near the load
While the primary energy saving (PES) curves are in accordance with the ratio curve, the recovered heat is enough to provide to the building in following the electric load (FEL) operation mode and part of the electricity is needed from the grid in following the thermal load (FTL) operation mode
This paper presents an analysis of CCHP systems operated following FEL, FTL and following a hybrid electric-thermal load (FHL) mode
Summary
Combined cooling heating and power (CCHP) systems, called trigeneration systems, are broadly defined as an energy supply system that generates electricity near the load. Some researchers [5,6] have investigated the operation modes of CCHP systems under two basic modes: following the electric load (FEL) and following the thermal load (FTL). These two basic modes do not provide optimal operation of a CCHP system. CCHP systems operated following the hybrid electric-thermal load have better performance than. In addition to the operation modes, it is necessary to apply evaluation methods to guarantee the better performance of CCHP systems over conventional technologies. Nelson et al [15] defined Building Primary Energy Ratio (BPER) as a parameter to guarantee better energy performance of a CCHP system. Generation efficiency of CCHP system ηe , efficiency of HVAC system ηeHVAC and the exhaust gas temperature (Th) of boiler export are introduced as a changing variable to generate a sensitivity analysis to show how the optimal operation strategy would vary
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