Paseo gets a solar sun roof

[MetroMPG]

I bet the panel will probably put out more than 36w... in perfect conditions (at noon, clean glass, clear sky, perfect orientation). But significantly less than that on average, since it will rarely be oriented toward the sun.

As a note: I did a simple test when I was playing with my solar powered boat this summer: just washing a light coat of pollen/dust off the glass improved power output by 5%.

Originally Posted by RobertSmalls

Since the graph starts at 0:15, the way I read it, half an hour will give you +30°F. Not huge, but it's something.

Good eye, Robert. That was a mistake on my part in the graph! I didn't start the x axis at 0:00, but should have - the axis was off by 0:15 relative to the points on the curve. Fixed.

PS: 30 mins gives my setup +30F. YMMV! Results will definitely vary depending on engine/coolant mass, heater type etc.

PPS: I wouldn't worry much about mppt or what to do with your dump load. First make it work! Then make it better. :P

[solarguy]

As noted by metro, your 36 watt figure is for ideal circumstances. That means:

1. oriented at 90 degrees to the sun at all times
2. cells are not hot. heat causes output to drop
3. no shading whatsoever
4. perfect soldering job/wiring/load/controller, with no or minimal losses

In reality, none of those conditions will apply to your installation. My biggest concern is with shading. For many panels, if you significantly shade even one cell, output can drop by 50-75%. Unless the cells are virtually in contact with the glass, you may shade some of the cells on the edge by the frame.

So, one of the consequences is that you may not need any charge controller at all if your battery is decent sized. Especially if it's flooded lead acid, as opposed to AGM (absorbed glass mat) or gell cells. FLA's appreciate a little controlled overcharge occasionally.

None of these issues should be a deal breaker.

HTH,

troy

[Christ]

Would you mind if your car wore a hat while parked?

I only ask because you could make a solar oven sort of thing that would fit onto your roof, which would help direct more of the light at your panels, making them more efficient, so that in perfect conditions, you could theoretically make as much as 50-55W, when parked in full sunlight.

What this means in reality, is that the actual output of your panels may be ~35W, as opposed to ~20 average.

Also - don't you normally park in the shade? What will parking in direct sunlight do for your commute during the hotter season? It's a Catch 22, there, since parking in the shade does nothing for your solar panels, but parking in the sun means you either open the windows or run a fan to cool you down on the commute home.. this might cancel each other out, no?

You could invest in reflective window treatments, basically cardboard plugs that fit into the window areas with aluminum foil on them.

If you really wanted to get fancy, you could make removable plugs for the windows that are on the same side as the sun will shine, and have solar panels on them as well. (Later project, obviously). If you park in an area that would have the sun on one side in the morning, but the other side in the afternoon/evening, you can switch them around at lunch time.

As for the SUNroof solar oven idea, you could use thermal convection to help cool the panels by raising the solar oven "hat" about an inch off the roof... as the heat rises, it will have to draw in cooler air from the area shaded by the "hat" surrounding the SUNroof.

[chuckm]

Well, could you take a 30W heating element from a soldering iron and immerse it into your coolant system?

[RobertSmalls]

Christ just reminded me what Toyota's solution to your problem was. The new Prius has a factory solar panel option. The solar panels run the blower motor at a low speed so your car is not an inferno when you park it in the shade. So even a Prius, with all its software and its huge traction battery, can't come up with a way to store the power of the sun.

I'd mount an alternator kill switch and a voltage gauge on the dash. If you have a handful of sunless days in a row, or a long road trip, you can turn the alternator on.

[Daox]

Thats quite true Robert. However, OEMs are unwilling to do certain things that we are. For example, my full grill block is serving me great. I did mention I'd probably do the fan blower mod. However, I don't need the fan blowing 6 days a week while the car is just sitting, and come winter I really would rather not have it operate that way. FYI, I do have an alternator switch.

I emailed a local EV club member and he said he could get me a used deep cycle for free. So, I will have a means to store energy to do something that requires a lot of juice every once in a while.

On the other side of things, I tried removing the black silkscreen shade last night. WOW is that stuff on there! I tried the carb cleaner, I tried the razor and it does not want to come off. I also looked at removing it and replacing it with lexan and that doesn't seem to be a possibility either. The guides for the sunroof are glued right to the window, so I don't have a means to remove it ATM. Ideas here would be really helpful.

[MetroMPG]

No luck with a blade? That's surprising. It's something painted / silkscreened on, right? Is it etched?

[MetroMPG]

Originally Posted by Daox

However, OEMs are unwilling to do certain things that we are. [....] However, I don't need the fan blowing 6 days a week while the car is just sitting

Just a matter of time before we see people ecomodding the Prius 3 solar roof to take advantage of the "excess" power it produces when running the cooling fan isn't needed.

[Daox]

I'm not sure exactly what it is. It is not etched. It does protrude above the glass.

[MetroMPG]

Know what? I just went and checked those dots around the edge of the windshield of another Toyota, and couldn't even scratch them with a razor blade.

It definitely seems physically part of the glass, not painted on. Have to wonder if it's some kind of hybrid etching/painting trick.