Structural Design of the mCCHP-RES System - Design for Micro-Combined Cooling, Heating and Power Systems - page 212

Surfaces PQRS and MNRS are the annually power load and heat load of the
system, respectively.

￿

(PV panels load) full and (ST panels) full are the surfaces UaVU si UbVU
respectively, and represent the annually load of the PV panels and ST panels
when they are working at their full installed capacity.

￿

(SE heat load) adopted is the surface IJRVbUS, represents the annually heat load
of the Stirling engine, and is adopted on the base of other assumptions.

￿

(Boiler load) is the surface IJNM, represents the annually heat load of boiler,
and is given by relation:

￿

ð Boiler load Þ ¼ Heat load MNRS ð Þ SE heat load ð Þ adopted ST panels ð Þ full ;

only positive values.

(SE power load) is the surface KLRS, represents the annually power load of the
Stirling engine, and is given by relation:

￿

ð SE power load Þ ¼ c SE heat load ð Þ adopted

- (Power excess) is the surface PQLK and represents the power remaining.

If this power cannot be valorized otherwise, then the excess power risk could be
mitigated as follows:

(a) by modulation of the (SE heat load) when the (SE heat load) adopted will be
replaced with (SE heat load) modulated , given by relation:

=c;

ð SE heat load Þ modulated ¼ ð Power load PQRS Þ ð PV panels load Þ full and

(b) by a corresponding decrease of the PV panels area, A PV .
To determine the electrical energy produced by the cogeneration unit, e cg ,we
will use the power balance equation for the stationary regime at batteries level and
result:

e cg ¼ e sys e PV ð 59 Þ

If result e cg < 0, then the cogeneration unit does not operate, the required energy
is provided by PV panels and the excess is stored in the battery. Further, because e cg
and q cg are connected by the power to heat ratio, γ , the speci c heat produced by the

cogeneration unit is given by the relation: