Solar boat

You might be onto something there

I believe it was Archimedes who used simple mirrors to light the apposing armies landing craft on fire. Maybe you could have some shore based minions set up with parabolic mirrors, You'll need a signal flair to coordinate things but its a contingency plan. If your boats not looking to good by say mid race, send up a flair.

 

(edit: see post #48 for link to actual course and rules. The actual race is not as described below)



Ok, lets say the race goes something like this. Start with full battery and do an endurance race in morning. Wait till 1 pm and do the slalom. Wait till 3 and do the sprint.
2 or three kids in the boat for each race.

In the above scenario, you need batteries with very good charge acceptance to efficiently use the available solar. AGM type if lead, or Lithium. You want a MPPT charge controller matched to your battery choice. You need to aim your panels at the sun, probably by moving the whole boat. Maybe have a way of aiming the panels as part of prerace setup.
you will also need some sort of battery monitor so you know where you're at.

I don't think this has been posted yet here at BDnet- http://photovoltaics.sandia.gov/docs/PDF/batpapsteve.pdf

some examples of stuff-

http://www.blueskyenergyinc.com/products/details/solar_boost_1524ix/

http://www.optimabatteries.com/_media/documents/specs/D34M.pdf

http://www.xantrex.com/power-products/power-accessories/linklite-battery-monitor.aspx

I've found Sun Electronics in Miami to be very good at making recommendation for integrating systems and their prices are pretty good too. (not affiliated in any way ...)

 

Do the rules say anything about reflectors?

 

The Rules

Ok all you. We have until May 18th to design a boat
Here are the rules for the Regetta to date.
1. One battery 100ah
2. Solar is the only source of energy
3. Boat maybe scatch or off the shelf
4. 4- MSX64 solarex panels only no mods
5. No shore charging of the battery
6. One DC motor of your choice
7. boat dims <20' long <8' wide <5'tall
8. Throttle must self return to zero position
9. must have kill switch
10. a power selector to switch between solar only and solar + battery
11. Slalom race (no definition yet) Solar only
12. Speed race ~200yards Solar only
13. Endurance Battery only 30 minutes

That is all I have at this point..

To all that have replied:
Thank you for all your input
Based on the time available we would like to purchase our boat and modify as needed to meet all of the specs. What is the best off the shelf boat for the application. Lightweight....
Drive: Definitely need help here all your input would be appreciated
Thanks
Jennifer

 

The Rules

14. One pilot (no weight min or max)

Thanks,
Jennifer

 

buy a used skull, like the race type multi person row boat. There long and thin and will make an efficient mover.

next is if mirrors to reflect more solar energy onto the one solar panel are considered a modification, I'd ask that question quietly of the race organizers.

find the lightest kids possible

No joke on that kids remark, weight will determine a lot in this event
speaking of which what exactly do they mean by "solar only"
are you expected to remove the battery for the 200 yard dash ?

 

No mirrors are allowed.
We will select the lightest kid in the class for the event.
the battery must remain in the boat but your motor must run off of solar cells only.

 

I see...so you need the most efficient method to keep the solar panels in line with the sun ,while presenting the least windage.


Hmmm....Im beginning to think that a small catamaran might be the best platform


What are the dimensions of the solar panels ?

 

the panels are 18"x40" and we will be using 4 of them @ 10 pounds ea.
Thanks

 

http://www.californiasolarcenter.org/newssh/pdfs/Solarex-MSX64.pdf

 

Good links, thanks.

 

(edit: the rules linked in post #48 now have single 12v 100Ah battery as maximum)


Just to be clear, you posted earlier that the batt would be 24 volt at 100Ah. I'm assuming the typical configuration would be 4 x 12V at 50Ah each arranged as 2 x 2 bank. 4 x 1 with 6V 100Ah would also work, as would 3 x 1 with 8V 100Ah. These last two are typical golfcart sizes. The standard rating condition for Ah is the C/20 rate. Not every battery on earth is rated this way, however. If you can find a 100Ah nameplate rating based on C/5, you will have a considerable advantage. Lithium cells will have a huge advantage since the batteries are now just dead weight for two of the races.

Option 1. Find a used two man scull and lop it at 20' carefully test the boat for trim. Moving the kid 6" could change drag by 3%. you will need to add a rudder from a kayak. They are available as kits. Because the boat will be going so slow, it will want to drift with the wind. You will want to put a wind surfer foil on the underside. These slide out for transport. You will need a PWM style throttle control. Stabilize the boat with small amas about 1 meter out from the hull. See the Pedalpowered boat thread for ideas. There is a free softwear for hull drag and power prediction that can automatically optomise the hull shape given weight and compute the required power. It is called Godzilla and was devised by one of our forum members. It is well suited to this problem but is a bit tricky to learn but worth the effort.

for the slalom, it would help to know how many gates, the gate spacing, and the gate's size (diameter) A single kayak rudder and a single windsurfer foil may not get you enough cornering.

Option 2. regarding the endurance race, 100Ah at @ 24V discharged in 30 min suggests 4800 Watts. If you use an AGM with a Peukert factor of 1.1 and assume 80% discharge, you get a revised calculation of about 120 amps at about a 22 volt average for 2640 Watts. In order to carry 120 amps with negligible loss, you need really really fat cables. Wires about the size of your thumb. Keep the runs under five feet for both supply and return. 2640 watts can easily put 500 pounds on plane at 10 knots in a 9' boat. If the boat weighs 80 and the kid weighs 100 and the drive weighs 325 you could plane with AGMs (just). Keeping it on plane for 30 minutes might be a trick though. You'd just have to try it. If you could get the peukert factor to 1.05 instead of 1.1, you should be home free. With lithium, no troubles at all. Might be able to average 15 knots in a totally tricked out boat. You will need to select the throttle controller for optimum efficiency at 110 - 130 amps. Figure a bit less than 10% loss in the throttle.
An old sunfish hull wouldn't be a bad place to start. You could probably cut two feet off the bow to save weight. A 20' scull would probably still have less drag even at ten knots, but it might really struggle in the slalom. I have also put a 17' aluminum canoe on a plane with a stock 2.5 hp johnson outboard, but minus the weight of the batteries. 2.5hp equals 1850 watts. I used an aftermarket 3 bladed aluminum prop to replace the plastic two bladed stock prop. So you could adapt an old three hp leg with an electric motor. I don't think too many trolling motors will pull 120 amps.

found this while looking for something else. Might be useful. You could drive the boat from shore and let the kids pretend, or at least get the kids back to shore

http://www.minnkotamotors.com/advantage/freshwater.aspx?sectionID=1

edit. you have to find and click on "ipilot" in the above link.

 

Opps...SOLAR POWER ONLY..no battery

 

I'm having a hard time envisioning a throttle system that would comply with the rules and also work from say 5 amps supply up to 150 amp supply. If the controller operates off the supply voltage and you hook it up to solar panels, won't it just drop out on low voltage at anything over idle. Are there controllers that have separate internal and control feeds so the controller can be powered by the battery and feed power only from the panels? Has the person writing the rules ever built an electric boat that will run his course? how about a "momentary on" 20A switch for the solar? A toe switch might be nice.

 

No battery for racing. To me this indicates that the race boat will be very low power.

It will need a system to keep all the solar panels perfctly aligned with the sun as the boat turns.

It might be worthwhile to see if you could store energy in capacitors for burst of speeds during times of low solar energy.