Thermodynamic boundaries of energy saving in conventional CCHP (Combined Cooling, Heating and Power) systems

• An improved calculational method of ESR regarding energy adjustments is presented.
• Definition of R is proposed to help find the most suitable users of CCHP systems.
• Maximums of ESR of CCHP systems have been calculated.
• “Thermodynamic boundaries” problem in CCHP systems is solved.
• ESR distribution of CCHP systems in China is shown based on investigation results.

In this research, an improved calculational method of ESR (energy saving rate) considering energy adjustments caused by climate effects is presented based on international standards or regulations regarding energy management. The indicator of “general heat-to-electricity ratio” (R) is proposed to illustrate the energy configurations of CCHP (Combined Cooling, Heating and Power) systems and their potential users. Theoretical calculations of “thermodynamic boundaries” incorporating the general heat-to-electricity ratio as well as the maximum of ESR have been discussed in the mode of “priority of providing cooling” to find the most suitable users for CCHP systems and to envision the energy saving potentials of CCHP systems. Moreover, investigation of CCHP systems in China in terms of ESR distribution has been undertaken to corroborate the theoretical calculations. Theoretical results show that the most suitable CCHP users should have their general heat-to-electricity ratios valued in the range of 0.9–2.8 (without heating demand) or 0.65–1.3 (with heating demand). Furthermore, particularly in Beijing, the maximums of ESR of CCHP systems without and with heating demand cases are 32.5% and 38%, respectively. Deviations between the investigation and theoretical calculations can be partially attributed to the assumptions, which have also been discussed.