New Wind-Diesel System from PitchWind®
In December 2002, a new wind-diesel system rated 30 kVA was
commissioned on Osmussaare, Estonia, by the Swedish company PitchWind
Systems AB. The wind-diesel system is the only power source on this isolated
island where a radar station is under construction. The end user is the
Estonian Border Guard and the project was carried out in cooperation with the
local partner Empower EEE, who also supplied the tower of the wind turbine.
The island Osmussaare (Swedish name Odensholm) is located at the inlet to
the Gulf of Finland, about 10 km from the Estonian coast. Today the island is
a nature reserve, inhibited permanently only by a farmer and his wife, and
there is no connection to the power grid on the mainland. Information about
the interesting history of the island, maps, etc can be found on
http://www.kultgeog.uu.se/vanback/ (in Estonian and Swedish).
When the Estonian Border Guard ordered the construction of a radar station
on the island, they asked for a wind-diesel system to reduce the fuel
consumption, compared to using only diesel power. Transportation of fuel to
the island is very costly. There is no harbour and the shallow beaches make it
impossible for deep-going boats to reach the island. During the winter, the ice
situation sometimes makes the island accessible only by helicopter.
The power system on Osmussaare is designed for a maximum power output
of 30 kVA and consists of the following main components:
One PitchWind 30/14 wind turbine (14 m diameter), equipped with a
hybrid control system. The wind turbine’s electrical system includes a
standard frequency converter by ABB, with input also for diesel and
battery power. A lattice tower, supplied by Empower EEE, is used on
this site (hub height 35 m). On Osmussaare, the wind turbine was
installed using two mobile cranes, but a climbing crane can be used
instead on sites where mobile cranes cannot be used.
Two SDMO diesel gensets, each rated 32 kW, with auxiliary
equipment, such as fuel tanks. The reason for choosing two diesel
gensets is redundancy (if one diesel genset is out of order, there is one
A battery bank with a gross capacity of 100 kWh. The battery bank is
optional and can be disconnected (e.g. if the batteries would be
damaged). The system will work anyway but fuel savings will be
greater with the battery bank connected.
Battery charger of standard industrial type.
Wind Is the Main Power Source
The wind-diesel system on Osmussaare is made for high wind penetration,
and is based on a concept originally developed at Chalmers University of
Technology in Gothenburg, Sweden. While other wind-diesel concepts for
high wind penetration are usually rather complex, the overall system design is
here simplified by using a wind turbine with the most suitable characteristics –
variable speed, pitch control and a special control system. This enables a
higher level of controllability than ordinary, grid-connected wind turbines. The
PitchWind wind turbine can control the power output to match the needs of
the grid. Also, the rotational energy of the wind turbine can be used as a
short-term energy storage, to even out the fast fluctuations in wind speed.
On Osmussaare, this means in practice that when the wind speed is high
enough for the wind turbine to alone supply the load, the diesel genset(s) are
automatically shut off. No expensive dumpload, rotary converter or custom-
built diesel genset (common components in some other wind-diesel systems)
is necessary to accomplish this.
When there is excess energy available, the battery charger is connected.
Excess energy can also be used for low-priority loads, such as hot water
heaters, but this option is not used on Osmussaare.
During the period december -02 to february -03 the wind supplied more than
85% of the energy consumed on the island corresponding to an annual fuel
savings of 25-30 m3 diesel fuel.
The features of the HCS hybrid system concept available from PitchWind can
be summarized as follows:
Large wind capture capability, 75-90 % wind
One or more wind turbines can supply the inverter, 30-120 kVA
One or more diesel gensets can be controlled
Diesel gensets can be stopped when the wind can supply the load
Standard diesel gensets can be used (no clutch or flywheel needed)
Excisting diesel sites can be uppgraded to HCS-system sites by adding
the PitchWind Wind Energy Converter(s)
Ability to integrate solar or hydro power
Large batteries, containing lead, acid or cadmium, are not necessary
Open control system, based on LonWorks technology
Grid back-up or UPS-function can be achieved by the HCS-system
Each year, more than 30 000 liters of diesel fuel can be saved giving
the operator the prerequisites for a good economy
Places that have an unreliable grid connection can also benefit from this
technology. In that case, the hybrid power system can function like a large
UPS (uninterruptible power supply) combined with renewable energy
LonWorks Control System
The hybrid control system, developed by the ÅF Group, is based on
LonWorks technology. This is a distributed and open control architecture,
which is used practically all over the world. It is ideal for applications like
hybrid power systems and distributed generation, because control systems
can be built with inexpensive off-the-shelf components, be designed to be
fault tolerant, conveniently integrate equipment from different manufacturers
and also combine the renewable energy production with efficient use of
In this context, “distributed” means that LonWorks control solutions are built
as networks, where controllers can communicate with each other over a
variety of media. In the hybrid control system, there are several controllers
that communicate in a peer-to-peer fashion with each other. There is no
master controller, which the entire system is dependent on.
An open communication protocol is used, which simplifies machine to
machine communications. In this case, it made it easy to integrate the
frequency converter from ABB, an electricity meter made by Gossen-
Metrawatt, a datalogger with GSM modem from Prolon and several other
devices into one interoperable control system.
An option of the hybrid control system, which was not implemented on
Osmussaare, is functions for efficient use of energy. This can bring increased
wind penetration, reduced costs and helps avoid oversizing the power system
due to high peak loads. One way of doing this is by demand side
management, which means that certain low priority loads are switched on and
off by the control system. Another way is to use a multiple tariff system, which
gives consumers an incentive to use more electricity when abundant wind is
available and less when generation costs are higher.
Next Island: Vaindloo
During May-June 2003, PitchWind Systems AB will install the second wind-
diesel system together with Empower EEE on Vaindloo, another remote
PitchWind Systems AB
Phone: +46 708 237 219
PitchWind Systems AB
SE-443 22 Lerum
Ph: +46 708 237 219
Ph/Fax: +46 302 159 04