MPPT for a solar boat

rpinnint

I am Rakesh. I am working on a project for which we built a solar panel for a competition. The requirements of the solar panel are "maximum output
of the solar array under normal one sun conditions will be 480 watts and the minimum output under normal one sun conditions is 100 watts". Right now we are using a MX60 PV MPPT (Maximum Power Point Tracking) Charge Controller to charge the battery and we want to use a better one with less weight and more efficiency.
We want to built a new solar panel. Which way is the best to built to have min weight and max output.
And if want to use a MPPT, what specifications do we need to know to select a MPPT?
This information will be very helpful.

Thanks,
Rakesh.

BB.

Re: MPPT for a solar boat

I am not quite sure what you are asking for/about...

If you are looking for a good quality, light weight/small MPPT solar charge controller--I would look at using the MorningStar 15 amp MPPT driving a 24 volt battery bank:

• 15 amps * 29 volt charging lead acid bank * 1/0.77 derating = 565 watts

So, using a 24 volt battery bank, you can pretty efficiently operating upwards of 565 watts of solar panels on typical sunny days...

A person asked about DriveTek MPPT charge controllers... I know nothing about them but they do appear interesting (can step up voltage from solar panels to battery banks--a rare function right now). And they are used in solar powered vehicle races.

May be of interest to you...

-Bill

rpinnint

Re: MPPT for a solar boat

Hi Bill,
I have one more question. Can we drive a motor directly from the solar panel with the Maximum Power point tracker controlling.

rpinnint

MPPt to drive a motor

I have a doubt that can we run a motor directly with the output from a Solar panel and also using the Maximum Power Point Tracker(MPPT) controlling the output from solar panel.

Thanks,
Rakesh

AntronX

Re: MPPT for a solar boat

Use lithium-phosphate battery instead of lead-acid. For your application Li-FePO4 battery will weight about 5 Kg or 11 pounds. You can use these cells to make your own battery pack. You will also need to buy or build battery management system (BMS) for these cells. They do not tolerate overcharging and overdischarging, which leads to early failure.

mike95490

Re: MPPT for a solar boat

rpinnint wrote: »

Hi Bill,
I have one more question. Can we drive a motor directly from the solar panel with the Maximum Power point tracker controlling.

You would need a Linear Current Booster Driver which was designed to assist a pump motor, but a boat motor would be the same sort of principal. Other vendors have higher curent (amps) versions .

You would likely not use MPPT before the linear booster. MPPT circuits have been designed to work with recharging batteries.

BB.

Re: MPPt to drive a motor

Rakesh,

I moved your question to your current thread--I assume it is all related and usually is easier for us to follow with all of the information in one thread.

rpinnint wrote: »

I have a doubt that can we run a motor directly with the output from a Solar panel and also using the Maximum Power Point Tracker(MPPT) controlling the output from solar panel.

Thanks,
Rakesh

If you wish to run a DC motor directly from a solar panel, one way to do it with "off the shelf parts" is with a Linear current booster:

7 amp Linear Current Booster/Pump Driver

Used to control and power a DC motor from a solar panel. The unit prevents stalling of the motor under less than full sun condition. The power of the sun is transformed to the motor running conditions so as the sun goes down the motor slows down instead of stalling. Conversely, or as the sun comes up the motor starts running much earlier instead of staying stalled for hours when it could be running. This translates into more running time of the motor where it spends a lot of time working instead of stalled doing no work.

Basically, a DC motor is sort of a constant power device... If the voltage falls, it wants to make that up with more current... Very similar to how a MPPT type charge controller works.

In the case with a Linear Current Booster--For a solar panel it is, more or less, a constant current source. When a motor loads the panel down below its Vmp (for a particular watt per sq. meter of sunlight power), the output voltage falls, but the current remains the same.

Remembering that Power=Voltage*Current and Current is "fixed" for a solar panel, the useful power of V*I starts to collapse.

For a LCB, it will replace the drop in voltage by supplying more current--and help keep the motor from stalling.

-Bill

rpinnint

Re: MPPT for a solar boat

Hi All,
Thanks for all the information. We are building a solar panel. We are using a Aluminium board as the base for the panels, but since aluminium conducts electricity, we need a material or any foam which can come in between the aluminium base and the solar panels. Can anyone recommend a good intermediate substance.
Also, what will be the best material to cover the top of the solar panel. We don't want to use a glass because it's very heavy for the boat. We want to use any light weight material which can also allow max sunlight.
Can you all please help me. I really appreciate your help.

Thanks and Regards,
Rakesh.

AntronX

Re: MPPT for a solar boat

Instead of aluminum use fiberglass mat soaked in resin. Instead of glass to cover cells, super clear, UV stable, non yellowing Urethane resin may work. I have not tried this method myself, but planning to try soon.

BB.

Re: MPPT for a solar boat

Going to suggest that an aluminum base with silicon solar cells on a boat is about the worst possible combination... Thermal expansion differences between aluminum and silicon, corrosion from water (salt water?). Aluminum is not very stiff (still need cover "glass" of some sort for stiffness).

In the end, get a relatively stable material (like Lexan) and then bond a flexible material to the back to make a water/air tight seal. From a variety of sources (verify your material expansion coefficients--there can be a wide spread even in similar materials, and I have not double checked the values below):

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thexp.html
http://www.novawafers.com/resources-about-silicon.html
http://www.machinist-materials.com/comparison_table_for_plastics.htm

Material Fractional expansion per degree C x10^-6

• Glass, ordinary=9
• Glass, pyrex 4
• Quartz, fused=0.59
• Aluminum=24
• Silicon=2.6
• Lexan (polycarbonates)=22

But even Lexan is 10x the expansion of silicon--Still a poor choice (most plastics seem to be 10x worse than Lexans.

-Bill

rpinnint

Re: MPPT for a solar boat

Hi All,
How does a Acrylite UV stabilized transparent sheet work instead of the glass and also ABS white sheet as the base? I saw these online. Does these work fine?