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EV: 7.2-9.1
Pantelleria × × 2231.8 7005.7 NEV: 27.4-46.9

EV: No viable
Ustica × × 0.0 683.9 pipes
NEV: 21.7-33.9

EV: No viable
Giglio × × 0.0 895.9 pipes
NEV: 25.2-37.4

EV: No viable
Linosa × × 0.0 553.0 pipes
NEV: 28.7-36.1

We may observe that almost in all the examined cases (with the only exception of Pantelleria)
having the connection costs covered by the company owning and operating the DH network is
preferable, due to the much higher linear heat density achievable. As concerns the energy uses to
be supplied, limiting the hot water distribution to cover the space heating and domestic hot water
uses is in general preferable; only in two islands (Lampedusa and Pantelleria) the distribution of
hot water to feed decentralised thermally driven chillers resulted the most promising option.

(iii) Identification of reasonable supply temperatures and type of pipes to be installed
Second level headings

In the previous subsection a reasonable network configuration and the specific energy uses to be
supplied via distributed hot water have been identified. Now, for each of the examined island,
design assumptions concerning the hot fluid supply temperature and the type of pipes to be
installed are briefly discussed. In particular, two main solutions are identified:
a. For islands where only space heating and Domestic Hot Water uses must be covered, the hot
water may be distributed at moderately high temperatures. However, there is no need to
consider very low supply temperatures, since the heat losses through the insulated pipes do
not represent a major issue, due to (i) the temperate climatic conditions, (ii) the moderate
amounts of heat distributed, on annual basis, (iii) the fact that the available waste heat from
the engines often exceeds the requests and may be considered as “free”. Then, a
Tsupply=85°C and a Treturn=60 °C were assumed. As concerns the pipes to be installed, the
operating conditions allow for installation of cross-linked polyethylene pipes which ensure
safe operation at pressures up to 12-14 bars (which have been verified compatible with the
expected operating conditions, also keeping into account the altimetric profile of the DH
network derived by an orographic study of the sites);
b. For the two islands where space heating, DHW and space cooling loads must be supplied,
the supply temperature must be consequently higher to drive the decentralised absorption
chillers. Then, it is assumed to distribute superheated water at Tsupply=110 °C, with a
Treturn=85 °C. In order to allow for safe operation, pre-insulated steel pipes are assumed to be
installed. Of course, when calculating the total cost of the network, costs for special
elements such as expansion joints will be included.

(iv) Evaluation of investment costs and possible revenues from selling heat to
private/public customers
The investment cost for the DH company (assumed, as said before, coincident with the company
that owns and operates the power plants) was calculated by the following Eq. (7):

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