T
he thermodynamic and
economic
performance of a
solar
combined heat
and power
(S
-
CHP)
system based on an array of
hybrid photovoltaic
-
thermal (PVT)
collectors
and
an organic
Rankine cycle (ORC)
engine
is considered
for the
provision of
heating and power
to swimming
pool
facilities
. Priority is given to
meet
ing the thermal
demand of the swimming pool
,
in order to
ensure a comfortable condition for swimmers in cold
er
weather conditions, while
excess
thermal
output from the collector
s
at high
er
temperatures
is converted
to
electricity
by the ORC
engine
in
warm
er
weather conditions. The thermodynamic performance of this system and its dynamic
characteristics
are analysed on the basis of a transient thermodynamic model. Various heat
losses and gains are considered in accordance
to
environmental and
user
-
rela
ted
factors
for both
indoor and outdoor swimming pools.
A case study is then performed for the swimming pool
at
the University
Sport
Centre (USC)
of Bari, Italy. The r
esults show that
employing
a
zeotropic
mixture
of R245fa/
R227ea
(30/70%)
as the
ORC
working fluid
allows such an ORC
system
to
generate
~50% more power than when using
pure
R236ea
due to the better
temperature
match
of
the cycle
to
the low
-
temperature hot
-
water heat source
from the output of the PVT collectors
.
Apart from generating
electricity, the ORC
engine
also
alleviates
PVT collector
overheating
,
and reduc
es
the required size of the
hot
-
water
storage
tank.
With an installation of 2000 m
2
of
PVT collectors, e
nergetic analyses
indicate that the
proposed
S
-
CHP
system
can cover
84
-
9
6
%
of the thermal demand of the swimming pool
during
the
warm
summer
months and 61
% of
its
annual
ly integrated
total
thermal demand. In addition, the system produces
a combined (from
the
collectors
and
ORC engine) of
328 MWh
of
electricity
per year,
corresponding to 36% of the
total electricity demand of the
USC
, with ~4% coming from the
ORC engine
.
The
analysis
suggests
a minimum payback time of
12.
7
years
with a
n
optimized
tank volume of 125 m
3