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(UPDATE: In 2015 solar panel company SolarCity announced [http://www.solarcity.com/newsroom/press/solarcity-unveils-world%E2%80%99s-most-efficient-rooftop-solar-panel-be-made-america commercial cells that are 22.5% efficient].)
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= Renewable Solar Power =
[[:{{TALKPAGENAME}}|Discussion/Comments]]
== Summary ==
There have been a lot of new developments on the renewable-energy front, and yet solar energy is not a good candidate for boat propulsion. A few years ago powering a trawler boat with solar energy would require towing a solar-barge larger than the boat, and in 2015 2016 not much has changed.
But still the headlines persist about the miracle of renewable wind and solar energy:
* [http://www.solvoltaics.com/ Sol Voltaics] in April 2016 announced a photovoltaic (PV) module with efficiencies of 27% or more.
* Holographic foil that is twice as efficient as typical photovoltaic (PV) solar cells, using light selection, deflection, and concentration. The Dresden-based company Apollon GmbH & Co claims this has 28% efficiency compared to a typical 17%.
* Modern silicon and indium-tin-oxide-based solar cells are approaching the theoretical limit of 33.7% efficiency but a research team at Princeton has used nanotechnology to create a mesh that increases efficiency over organic solar cells nearly threefold.
* Solar
* [[FuelCell|Hydrogen]]
Wind is a non-starter for propulsive power because, well, if you want to use wind power, get a sailboat! Right?
In practice, for an 8-hour summer day, 40 degree latitude, the sun delivers an average [http://zebu.uoregon.edu/1998/ph162/l4.html 600 W/m²]. Currently the best commercial solar panels are ~16% efficient. At an efficiency of ~16% on a perfect sun day this is a yield of 96 W/m² averaged over 8 hours (0.768 kWh).
Now, metric horsepower, widely used in the auto industry, is defined as 0.73549875 kilowatt (kW). Assuming we need 200 horsepower (hp) to drive a 70-ft boat, this is ~147kW. At 96 W/m² this equals 1,531 m² (16,472 ft2) of panel acreage [1 m² = 10.76 ft²]. And this is just for propulsion during daylight hours. There is no extra for storage in a battery for night operations.
