Fact check requested - Schleswig Holstein solar ferry

Various and sundry versions of this story of an epic fail of a solar ferry boat in Germany have been making the rounds, but I can't seem to find anything approaching a reliable account of the alleged fiasco. I am willing to believe it, but I'd prefer to not have to. Anyone in Germany or Denmark familiar with this episode which apparently played out over a couple years. Any specs on the old ferry's propulsion power compared to the new one? And is it cable guided or does it winch it's way across? And what is the fare?

Here's one account.



There seem to be a handful of similar craft that actually do try to do similar jobs in restricted emissions areas. Most seem to have appeared around 2022. Any info on successes would be welcome as well. Personally, it doesn't make sense to me to do that; but for the price, I reckon it ought to be feasible to transit a 100 yard cableway with a solar ferry. Maybe more of a boat problem than a power problem?

 

Something doesn’t add up…

I can understand and accept the ferry being underpowered and in need of bow thrusters for better maneuverability, but to suggest that the solar panels aloft created so much windage that they were drastically slowing the boat seems strange based on their flat low profile and operation on what I assume is flat body of water (no rolling/pitching).

Seems more likely that when loaded, the ferry’s increased displacement and wetted surface area along with wind and water current calls for larger more powerful motors.

Agree it would be interesting to learn more about the system design.

Curious about the propellers and operating speeds of the vessel.

 

Articles about the ferry. While in German I was able to read them translated to English using the Chrome browser.
Ärger um Schleifähre Missunde geht weiter: Die neue Elektro-Fähre startet frühestens Ende 2025 https://www.ndr.de/nachrichten/schleswig-holstein/Missunde-Neue-Elektro-Faehre-startet-fruehestens-Ende-2025,missunde188.html
Schleifähre "Missunde II": Frust statt Freude nach Fährstart https://www.ndr.de/nachrichten/schleswig-holstein/Schleifaehre-Missunde-II-Frust-statt-Freude-nach-Faehrstart,missunde182.html
Update on the ferry debacle: petition to preserve the old grinding ferry https://www.boote-magazin.de/en/travel-and-charter/territories/update-on-the-ferry-debacle-petition-to-preserve-the-old-grinding-ferry/

Many, but not all, of the problems encountered are the result of the new ferry being much larger than the old one with twice the carrying capacity. The infrastructure needs modifications beyond those already done.

The structure supporting the solar panels would have considerable drag, and it is not present on the older ferry. Also the area reportedly is windy.

The ferry has batteries in additon to solar panels. I am curious what portion of the power used to charge the batteries is supplied by the solar panels, and what portion is supplied by a shore connection while docked.

 

I'm having a real problem understanding this. I estimate about 7000 sq ft, or 700 sq meters of solar. During tourist season, that should net 2.1MWe. If you have a 14 hour day and a duty cycle of around 0.1, you can average 1000 hp! So you will need batteries to handle the peak power, but that isn't too hard. Even if the trip distance is longer than what was reported and the duty cycle is 0.2, you still have gobs of power for a simple grinder ferry.

I thought it rather funny that the operator reported that even if they get the new one running, they won't be able to operate it at a profit for just one car at a time. If that was a desirement, then they really did screw the pooch. This new one isn't likely to do well as a tramp ferry. They will need a schedule and a minimum aggregate fare. There probably should have been some discussion of the point that a ferry that can carry the weight of a tractor trailer probably can't carry bikes one at a time at a profit.

 

The articles cited show that the problems mainly refer to the cable system (it is a cable ferry, no propellers) beeing too weak to hold the new, bigger vessel on track in "high" wind and (water-)current conditions. The only component that increases wind sensitivity for the new ferry, compared to a similar sized vessel with combustion engines, is the solar panel array. All other lateral surfaces are of comparable dimensions.

It seems the SOR to which it was built is not well suited to the local demands, and the lack of insight regarding the cable loadings has resulted in docking calamities. Principally, on a short trip like this here, I see no benefit carrying the solar panels onboard; they should be stationary and either charging onboard batteries during docking periods or direct feeding the puller winches via cables.

 

The solar panel area is about 260 m² (31 m * 8,8 m * 0,95). The Globalstrahlung (all the sun gives to this region (nearest data point is Kiel)) in the whole year of 2023 was 1,093 kWh/m² that makes 284 MWh energy of solar radiation. Solar panels of today may have an efficiency of 20% that makes 56.8 MWh electric power harvesting per year (Losses not accounted). Per day it is 156 kWh.

The ferry is owned by the state who has to provide a reasonable network of public transport. This is not for making profit but to serve the people living and working in this area.

 

The rendering is rather misleading as to size. Those must be kiddie-sized picnic tables. And I goofed because I used a per-panel daily productivity from memory, but applied it to the area in square meters of panels. The numbers work much better now.

Also found some good info on Vessel Tracker - Missunde III - Passenger ship, MMSI 211866190, Rufzeichen DJ9714, Flagge Germany - vesseltracker.com https://www.vesseltracker.com/de/Ships/Missunde-Iii-I3170528.html