1. Introduction - Firenze University Press

2.5. Selecting the number of TSs
Selecting the number of TSs depends on the accuracy required. Fig 4 presents the obtained Pareto
results from the multi-objective optimisation, where minimal numbers of TSs are shown vs.
different tolerances selected.
INA [%] 20
18
16
14
12
10
8
6
4
2
0
0 10 20 30 40 NTS 50
Fig. 4: Selecting an acceptable inaccuracy
As can be seen from Fig 4, by increasing the tolerance the number of TSs decreases but, however,
the inaccuracy becomes too high. On the other hand, if the tolerance is too small, the number of TSs
might become too high and, hence, the further steps of integration would be too complex; however,
no significant improvement may be achieved. The exact trade-off between the number of NTS and
INA depends on the users INA tolerance. As can be seen from Fig 4, generally, a tolerance of
between 5 and 10 % should be acceptable as with increase NTS the inaccuracy is not increased
significantly.
3. Estimating the supply-loads
The supply of the loads is determined separately in each TS. Estimation of the supply-loads depends
on the capture system. Different kinds of systems are possible, or even a system coupled with a heat
pump [21]. A simplified scheme for capturing was assumed during this work (Fig 5). The heattransfer
from the collectors in this model can be (i) direct or (ii) indirect. Direct heat-transfer is
feasible when solar thermal-energy is available and there is a demand within the evaluated TS. If
the amount of heat is higher than the demand or the heat-transfer is unfeasible in one TS, then the
heat is transferred to storage. This heat will be available for covering any heat-demand in the
following TSs. The indirect heat-transfer is the described transfer through storage.
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