Need help with a School Project

[TheCoachStone]

Hey guys,

I am the sponsor for my schools solar sprint team. It is a tiny solar panel, attached to a tiny DC motor which moves a car. The panel and motor pieces are set, but we were wondering if there would be a way to keep the voltage up higher and maybe increase speed. Not sure if this is possible, but I knew someone here would know.

Thanks,

 

[MTM98290]

What are the rules?

 

[upnorthandpersonal]

You won't get maximum power transfer from the panel to the motor by hooking them up directly. You likely need to do some matching, i.e., by PWM-ing the panel output over a capacitor (check out how PWM charge controllers work, and how electric resistors for water heaters are hooked up to solar PV).

 

[TheCoachStone]

What are the rules?

Pretty much that we just can't add any power storage except the two backup AA batteries - they only use the batteries if it is overcast.

 

[TheCoachStone]

You won't get maximum power transfer from the panel to the motor by hooking them up directly. You likely need to do some matching, i.e., by PWM-ing the panel output over a capacitor (check out how PWM charge controllers work, and how electric resistors for water heaters are hooked up to solar PV).

I know capacitors are banned. It's capacitors and anything that stores power can't be used.

 

[BackyardBandit]

Weight reduction and/or fiddling with gearing might be your only avenue given the aforementioned restrictions.

 

[TheCoachStone]

Weight reduction and/or fiddling with gearing might be your only avenue given the aforementioned restrictions.

We discussed both of those things, and that may be the only option.

We are CS and chemistry teachers, so electrical is a bit out of our field.

 

[Symbioquine]

Reducing rolling resistance, air resistance, and the rotating mass of the wheels should also be considered.

Possibly even with unconventional support and propulsion - depending on the surfaces this device needs to operate on (and the weather conditions it should operate in)...

* Very light vehicles have trouble with traction so a propeller might become more efficient than driving the wheels under some scenarios - and potentially avoids the need for heavy gearing.
* Fine spring wire (possibly teflon coated) skids might be orders of magnitude lighter than similar performing bearings on certain surfaces like smooth blacktop.

Weight reduction and/or fiddling with gearing might be your only avenue given the aforementioned restrictions.

Assuming mechanical power storage like springs or flywheels also also out, I think this is right.

 

[TheCoachStone]

Reducing rolling resistance, air resistance, and the rotating mass of the wheels should also be considered.

Possibly even with unconventional support and propulsion - depending on the surfaces this device needs to operate on...

* Very light vehicles have trouble with traction so a propeller might become more efficient than driving the wheels under some scenarios - and avoids the need for heavy gearing.
* Fine spring wire (possibly teflon coated) skids might be orders of magnitude lighter than similar performing bearings on certain surfaces like smooth blacktop.



Assuming mechanical power storage like springs or flywheels also also out, I think this is right.

This seems to be the consensus.

Would a boost converter help?

 

[Symbioquine]

This seems to be the consensus.

Would a boost converter help?

Pretty much all off-the-shelf converters will have capacitors inside so you need to really nail down what the rules actually mean and how they're enforced.

 

[MTM98290]

How about a fresnel lens above the solar panel?

 

[Symbioquine]

How about a fresnel lens above the solar panel?

Or, similarly, you might be able to avoid the superstructure/air-resistance necessary to support the lens, by instead pointing the solar panel down and making the body of the vehicle into a reflective collector that focuses a larger area of solar onto the panel. (Though you have to be careful not to melt the panel or exceed its output specifications by too much.)

 

[TheCoachStone]

How about a fresnel lens above the solar panel?

Never heard of it - I will look it up! Ty

 

[TheCoachStone]

Or, similarly, you might be able to avoid the superstructure/air-resistance necessary to support the lens, by instead pointing the solar panel down and making the body of the vehicle into a reflective collector that focuses a larger area of solar onto the panel. (Though you have to be careful not to melt the panel or exceed its output specifications by too much.)

I will pass this on to my team. TY!

 

[BackyardBandit]

Reducing rolling resistance, air resistance, and the rotating mass of the wheels should also be considered.

Possibly even with unconventional support and propulsion - depending on the surfaces this device needs to operate on (and the weather conditions it should operate in)...

* Very light vehicles have trouble with traction so a propeller might become more efficient than driving the wheels under some scenarios - and potentially avoids the need for heavy gearing.
* Fine spring wire (possibly teflon coated) skids might be orders of magnitude lighter than similar performing bearings on certain surfaces like smooth blacktop.



Assuming mechanical power storage like springs or flywheels also also out, I think this is right.

Hell yes! The "air-boat?" concept could work out very well if the motor spins fast enough to generate decent thrust from a propeller. No wheels required, just skids.

 

[bolhuijo]

Hell yes! The "air-boat?" concept could work out very well if the motor spins fast enough to generate decent thrust from a propeller. No wheels required, just skids.

and you could adjust the propeller so that the motor runs at the sweet spot nearest the maximum power point of the solar cell.

 

[MTM98290]

Maybe they could experiment with dry ice containier below solar cell for cooling to get max voltage, as well as offset any heat created by fresnell lens or mirrors. These two things are generally forbidden near solar panels, but this is a race, so I am guessing that the.panel won't need to be long lived. Frost could become an issue.

Is this a distance race? Or a drag race? Or?

 

[wme]

Dummy, read ALL the OP's statement

 

[bolhuijo]

Maybe they could experiment with dry ice containier below solar cell for cooling to get max voltage, as well as offset any heat created by fresnell lens or mirrors.

Put the dry ice inside a box so that the CO2 is forced out the bottom, air-hockey table style, voom you got a hovercraft!

 

[MTM98290]

... It is a tiny solar panel, attached to a tiny DC motor which moves a car. The panel and motor pieces are set, but we..."

do you mean that the panel and motor are physically attached to each other, or did you mean that the panel is electrically connected to the motor?