Combined Micro-Systems - Design for Micro-Combined Cooling, Heating and Power Systems - page 76

Thus, the dependency of the overall ef ciency of separate energy production on the

cogeneration index may be mathematically expressed with the relation:

1 þ c

EFF SHP ¼ ð 10 Þ

c
g e þ

1
g th

The overall cogeneration ef ciency, de ned by the relation:

E Q

Q CHP ¼

þ E Q

Q SHP

þ Q SHP

Q CHP ¼ g SHP

Q SHP
Q CHP

EFF CHP ¼ ð 11 Þ

leads to the following dependency on the cogeneration index:

1 1 þ c

EFF CCHP ¼ ð 12 Þ

c
g e þ

1
g th

0 ; 95

Figure 12 represents the dependency of ef ciency on the power ratio.

ciency
cogeneration based on a useful heat demand is a Community priority given the
potential bene

According to the Directive 2012/27/EC, the promotion of high-ef

ts of cogeneration with regard to saving primary energy, avoiding
network losses and reducing emissions, in particular of greenhouse gases. In

addition, ef cient use of energy by cogeneration can also contribute positively to

the security of energy supply and to the competitiveness of the European Union.
Directive 2012/27/EC on the promotion of cogeneration based on a useful heat
demand in the internal energy market shows that the power to heat ratio is a
technical characteristic that needs to be de

ned in order to calculate the amount of
electricity from cogeneration. Electricity from cogeneration shall mean electricity
generated in a process linked to the production of useful heat and is calculated
according to the following formula: E ¼ c Q

Fig. 12 Efficiency
dependency of the power to
heat ratio

0.75

0.65

EFF CHP

0.55

EFF SHP

0.45

0.1 0.5 1 1.5 2 2.5 3 3.5 4

10% E
90% Q

80% E
20% Q

Power to heat ratio