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Lars  Overgaard

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Ry Havnefront fotograf er Gert Skærlund Andersen

MPDH - Marina Power Distribution Hub

Photo: Gert Skærlund Andersen

There are close to 2600 pleasure motorboats in the Danish river Gudenaa and connecting lakes. The majority of the boats are located in a 19 km river section from Ry to Silkeborg, which is a closed system that only very small boats can sail away from; other boats must leave by road.

There is no central registration of boats in Denmark and therefore no credible numbers have been found for motorboats. It is assumed by the project that the high concentration of boats in the Silkeborg – Ry area may represent less than 10% of all the Danish leisure motorboats and as such allow for a very rough extrapolation to a national scale.

The project has in this limited geographic area assessed the energy potential with respect to leisure and tour boats, which could be electric without performance degradation, and the energy that would shift from fossil fuels to renewable electric energy. The national energy target on becoming independent of fossil fuels sets the expectation that most leisure boats will be powered by electricity in 2050.

Assuming that the transition from Internal Combustion Engines (ICE) to batteries and electric motors had not yet started, the project idea was to analyse if and how the future electric boats can support the SmartGrid control necessary to achieve 100 % independence from fossil fuels in the Danish electric power supply network. The project had focus on three areas – to assess the potential for shift to smart managed renewable electric power for leisure boats.

  1. Analysing the number of boats that are suitable for electrification
  2. Some electric boats may have PV-panels for sailing, with a surplus production.
  3. Optimise use of renewable energy by smart exchange of energy locally in marinas and reduce load both on the grid and the marina power feed connection.

Conclusions are summarised below using three hypotesis. 

The project hypothesis no. 1

Few boats are now propelled electrically but many of the boats have the potential to become powered by renewable electric energy in the future. 

  • Has a transition towards electric boats started? Are there any indicators as to when it might peak?
    [no transition started in 2012 and a transition peak was estimated more than 5 years away]
  • Find the number of motorboats that are readily feasible for electric propulsion powered by batteries.
    [52% of the motorboats never leaves the area meaning approximate 1300 of the boats could be electric without range problems]
  • What is the size of the related electric power/energy needed from a charging infrastructure? [1300 boats charging at the same time with 1 kW would require two full standard size 10/0.4kV substations that are typically used for a couple of hundred houses. The average time needed for charging the boats would be fairly short – very few hours only meaning that with a proper charging management the actual continuous power required may be reduces by a factor 20 to 50.]

Project hypothesis no. 2

Many of the future battery powered boats will likely have Photovoltaic panels (PV-panels) to charge the battery and extend the range. If the in-use-frequency of most leisure boats is very low, the PV-panels will be idling already few hours after last tour. Assuming that PV panels can in most applications produce much more energy than the battery can hold if not in use.

  • Can it be estimated how much solar energy could be “wasted” on a typical solar powered leisure boat?
    [example: One sunboat (SunCat21) cold produce 3kWh or more per day not sailing in the summer period.]
  • What is the typical leisure boat use frequency?
    [the boats are only away from the harbour 2-8% of the time and 59% sail less than weekly]

Project hypothesis no. 3

Using surplus solar energy from PV-panels on battery boats to help charge other battery boats and contribute to the marina and the electric grid would support the national energy strategies very well.

  • Analyse boundary conditions for establishing a local energy hub system (model) to handle energy from
    1. a PV boat to a) battery boat; b) Marina club house; c) the grid (only surplus energy from the PV-array) [The PV boat must have its own separate production meter and the energy can only be sold to the grid as any generator. Other consumers must pay full price including tax]
    2. a battery boat to b) Marina club house; c) the grid [The Battery boat must have its own separate production meter and the energy can only be sold to the grid as any generator. . Other consumers must pay full price including tax]
    3. a land based PV system to a) battery boat; b) Marina club house; c) the grid [The Marina must have its own separate production meter and the energy can only be sold to the grid as any generator. Other consumers must pay full price including tax.
    4. in general [Energy can only be shared behind a meter within a single plot of land. You are not even allowed to use excess PV-power from your own boat tied up to your own plot but in river-water. Unless the boat is on dry land on your own plot it is considered a different plot requiring separate metering for any production. The present Danish tax system and regulation is quite effective in preventing any smart use of renewable power.]

Half the leisure boats analysed never leaves the lakes meaning that they are suitable for being propelled electrically and powered by batteries. The project was and still is early relative to a transition towards electric powered boats. The motorboat owners seem to be fairly conservative and a transition to electric power is not exactly welcomed by the marina representatives. The boat owners fear that politicians may be tempted to force specific solutions without respect for the large investments done in the current leisure boat fleet.

The power consumed by the leisure motorboats is marginal compared to road transport. The local leisure motorboat fleet seems to consume less diesel fuel than two 12m city busses on an annual basis. This small energy consumption per boat distributed on the full fleet cannot yet justify investments in e.g. new SmartGrid charging equipment.

The final report from the project can be found here


Project name was ’Marina Power Distribution Hub with Smart-Grid Functionality’, and the project was led by Lars Overgaard from Danish Technological Institute in Aarhus.

Project duration from 1’st of February 2011 to 30’th of June 2012.

Project was financially supported with 1,6 mio. kr. from the ForskEL under the  Climate- og Energy Ministry. Partners in the project was Danish Technological Institut, Solbaaden ApS, EnergiMidt A/S, Municipality of Skanderborg,  Destination Skanderborg, Municipality of Silkeborg, Hjejleselskabet and Kvickly in Ry.

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