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 In the examined island (i.e. Lampedusa), for both the scenarios concerning the coverage of
connection costs, the supply of hot water for space heating, DHW and space cooling (by on-
site production via thermally-driven chillers) is much more viable than the supply of hot water
for space heating and DHW only. In fact, the linear heat density corresponding to the former
scenario (indicated by yellow diamond-type markers in Figures 11 and 12) is much higher
(and the distribution cost consequently lower) than the heat density corresponding to the latter
scenario (indicated by black bullets in Figures 11 and 12). Then for the examined island, due
to the prevalence of cooling loads (compared to space heating and DHW ones, see Figure 9),
induced in its turn by the high touristic vocation of the islands which makes the number of
occupants in the summer period much higher than in winter, only a heat distribution system
designed to supply energy to cover all the thermal and cooling requests could be at some
extent economically justifiable;
 From a comparison between the distribution of the yellow diamond-type marks in Figure 11
and 12, it is evident that most of the pipes/trenches achieve much higher linear heat densities
(and much lower distribution costs) in the scenario with “coverage of distribution costs by the
company owning the network” (see Figure 12) compared to the costs in the scenario with
“coverage of distribution costs by the private customers” (see Figure 11). Then, the much
lower connection rate assumed in this latter scenario would represent a strong barrier to the
feasibility of the network, inducing to consider the former scenario as the most attractive;
 A limited number of pipes (T8, T10, T11, T12, Tb4, Tb5 and Tb6) resulted not economically
viable. The cause of their high distribution cost is evident in Figure 9: they distribute hot
water only toward the Areas 1 and 2, which are characterised by low energy loads and are the
farthest from the power plant. Then, limiting the extension of the main of the DH network to
the pipes distributing heat toward the Areas 1-4 (the only ones resulted Economically Viable,
EV) seems to be the preferable solution. However, in the framework of this particular study,
the analysis is carried out by assuming to distribute heat also toward these two small areas
(via Non Economically Viable pipes, NEV). In fact, the study is aimed at finding a reasonable
compromise between the economic viability of the designed solution and the public interest to
increase as much as possible the share of energy loads covered by CHP.
Similar analysis were performed for all the six examined islands, again identifying the most
promising scenarios, the economically viable pipes of the main configuration and, eventually,
assuming a final design with a slightly larger DH network configuration (i.e. including some Not
Economically Viable pipes), in order to maximise the energy loads covered by CHP. The results
for the six examined islands are schematically resumed in Table 4.

Table 4. Most promising scenarios identified on the basis of distribution costs diagrams

Most attractive scenario Most attractive scenario
as concerns the Range of
coverage of connection as concerns the energy Total extension Total distribution costs
Island costs uses to be supplied of the viable extension of for the Viable
(cost<10 €/GJ) the main pipes (EV) and Not
Coverage Coverage Space Space heat. main pipes [m] assumed to Viable (NEV)
by private by DH heat. + + DHW + install [m] main pipes [€/GJ]
customers company DHW Space cool.

EV: 3.9-8.1
Lampedusa × × 3398.1 4484.6 NEV: 14.8-27.4
EV: No viable
Favignana × × 0.0 2789.1 pipes
NEV: 16.4-52.3

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