Structural Design of the mCCHP-RES System - Design for Micro-Combined Cooling, Heating and Power Systems - page 215

where:
ʷ Href = 0.8 is the ef ciency reference value for heat production;

ʷ Eref = 0.33 is the ef ciency reference value for power production;

e sys is the annual speci c electricity production from CCHP system;

q sys is the annual speci c heat production from CCHP system;

q F is the speci c fuel consumption of CCHP system.

PES does not point if this production of the CCHP system is useful or not. The
energy could be exceedingly produced and dissipated in the environment (espe-
cially the thermal energy).

The second indicator namely Energy ef ciency (EFF) sets the correlation

between the primary and useful energy and shows how much of the primary
energy is found to be useful energy and is given by the relation:

￿

e sys þ q sys

EFF ¼

q ST

100 % ð 63 Þ

q F þ e PV þ

where:
e PV

is the annual speci c electricity production from PV panels;

q ST is the annual speci c heat production from ST panels.

7.2 Performance Evaluation and Improving in the Case
of Structural Models with Mechanical Compression
Chiller

To calculate the two indicators PES and EFF, we need to determine the speci c fuel

consumption of CCHP system. Speci c fuel consumption is the sum of fuel input

for cogeneration unit and additional boiler. Its determination involves knowledge of
cogeneration unit and boiler energy production, and cogeneration unit and boiler
ef

ciency.
To exemplify, let us consider the illustrative exercise from the paragraphs above.
Using data corresponding to the illustrative exercise, namely from Table 31 for
monthly energy speci c consumption of the mCCHP system in the case of cooling

with mechanical compression chillers, and from Table 6 for monthly speci c power

and heat production of the panels, we can determine the energy production of the
CHP and backup boiler. The results obtained for the mCCHP system with
mechanical compression chiller are shown in Table 35 , then PES = 73 % and
EFF = 55 % for the whole CCHP system. Even though the PES is high, the
ef

ciency is low indicating an excessive energy production.