IEEE Electrification Magazine - June 2017 - 26

associated with decommissioning of thermal capacity are
not considered in the following.
The regulatory framework has to be adapted for this
project, having to reconcile all actors involved in the operation and management of a small NIIPS with very high
RES penetration: HEDNO as the operator of the NIIPS, the
owner and operator of the thermal power station, independent power producers from small RES stations, as
well as the owner and operator of the new RES and storage facilities that will be installed as part of the Smart
Island Project. Identification and resolution of potential
conflicts with the minimum possible derogations from
the existing legal and regulatory framework are prerequisites for the successful deployment and subsequent operation of the project.

Selected Island
An island suitable to host the Smart Island Project is Astypalea (see Figure 10), because of its size and the lack of large
RES installations, existing or planned. Astypalea is located
in the southeastern Aegean Sea and has a population of
1,334, with a peak annual load of 2.3 MW and annual energy demand of 6,600 MWh (year 2015), with the typical summer peaking demand pattern. The power station of the
island comprises five diesel units with a total capacity of
4.3 MW. Four ground PV stations and seven rooftop PV systems are in operation (320 kW and 35 kW, respectively).

Supporting Studies
Prefeasibility studies have been performed by HEDNO to
determine fundamental management policies and analyze the operation and anticipated economics of the
Smart Island Project.
The NII Management Code details a specific generation
management framework, outlined in the third section,
which is not optimal for this particular application, especially the RDAS stage. This framework has been simplified to
include a UC cycle scheduling thermal unit start and stop
operations based on load and RES-generation forecasts over

a one-to-four-hour look-ahead period and the state of
charge of the batteries. Then a load dispatch cycle takes
place, typically on a one-to-ten-min cycle, determining load
allocation to storage, diesel, and RES units. A similar concept
is described in E. Vrettos and S. Papathanassiou.
Besides generation management studies, a variety of
additional technical studies are to be performed, to
address, for example, network development, protection,
frequency and voltage control, necessary upgrades to the
thermal units, and SCADA and ECC infrastructure.

Preliminary Findings
The reference scenario adopted in the prefeasibility studies considers a system comprising a 0.4-MW ground PV
station, 2-MW wind farm, and a 2-MW/8 MWh battery
storage system. The simulations results, assuming the
management policy described previously, show that RES
penetration levels as high as 73% of the annual demand
can be achieved (around 8% being due to the existing
small PV stations), reducing the output of the thermal
units from 6,320 to 1,840 MWh per year.
The optimal combination of RES technologies that
could ensure the highest internal rate of return (IRR), at a
level of RES penetration beyond 60%, was one of the main
questions addressed. Figure 11 presents indicative results,
assuming different wind-farm and PV station sizes.
Although differences in the anticipated return on investment are not significant, it appears that wind should be
the dominant RES-generation technology for the Smart
Island Project, which is reasonable given the significantly
higher capacity factor (typically 30-35%) compared to PVs
(15-18%) at similar investment costs per MW.
Storage is the most expensive component of the Smart
Island Project, and, therefore, sizing its capacity has a
major impact on project feasibility. Increasing storage to
8 MWh (i.e., a four-hour equivalent duration) in the reference scenario is not economically optimal, as shown in Figure 12, but was driven by the need to reduce the number of
start/stop operations of thermal units, as well as to ensure

15.00

IRR (%)

14.50
14.00
13.50

0.4 MW PV,
2.4 MW WT

1.6 MW PV,
0.8 MW WT

0.8 MW PV,
1.6 MW WT

0.4 MW PV,
2 MW WT

12.50

0 MW PV,
2.4 MW WT

13.00

Wind and PV Sizing
Figure 10. The island of Astypalea.

I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2017

Figure 11. Anticipated IRR for different RES capacity combinations.

Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2017