Sunday, August 7, 2016

A ceiling vent

For time immemorial there has been an unpowered vent in the roof of the bus at the front. Today out of interest I coupled that vent to a CPU fan and powered the fan from a battery. Nothing is permanently affixed yet but things are looking promising. I went on the roof with a plastic bag that I held over the vent and the bag did indeed fill with air from the vent.
It's all held in place with tape but if the results are good, a bigger fan could be installed and powered by a solar panel. As can be seen in the picture, my 88 cent white foam board is in place and is cutting down on heat. Looking at the top right, the hard to remove no guns sticker is slowly coming off though it's a case of picking a little off at a time.

Working outside the bus, I cut a section of 1/4 inch thick aluminum to go under the hole in the bedroom floor. That's about as far as I can go with that for the moment. The wasp nest means I can't really work under the bus for the moment.

Inside the bus, I installed a charge controller then installed some wiring together with a 10A fuse. I'd about finished the wiring but messed up with my last crimp connector and then visitors arrived. The bus battery, according to my meter is about 12.3 volts which means it's pretty flat. That doesn't surprise me, given the fact I've not driven the bus in probably 5 months.

The plan is to install solar panels on the front of the bus, where the destination board would normally reside. I'm thinking about four. There will probably be one dedicated to the bus battery, one dedicated to an extraction fan and two dedicated to battery charging. Of course, if I can fit five panels then so much the better.

The interior of the bus rose to 99F today. The window unit was unused. The front ventilation fan didn't seem to help, which was odd. One would assume that extracting hot air would allow cool air to rush in. At least, that's the theory of convection, take the hot air off the top and let cool air come in the bottom.
Finding a screw connector, I installed my charge controller. This is the one that arrived with a broken mount as can be seen. I've added a 10A fuse and the whole thing is switched on the console. I like being able to isolate my additions via switches. That means that if one misbehaves I can just flip it off!

The next stage will be to put a pair of rods down from the solar panel connections to which I can clip the alligator clips on my small solar panel. That allows me to use my 5W panel and to be able to remove it when not needed. I have no illusions that a 5W panel will achieve much, if anything.

Sometime the supplier will supply a charge controller that doesn't have broken parts. I look forward to that! Apparently this controller has a maximum limit of 20A. 5 of the 10W panels will produce an absolute maximum of 50W and that divided by 12 is a maximum of just over 4A.

If I can power some ventilation and possibly phone and tablet charging from solar power then I'll regard it as mission accomplished. A few months ago I had aspirations toward running everything off solar power. Given that my roof area is approximately 7 feet by 24 feet or 168 square feet, I doubt that would be possible. Indeed, since the current crop of panels seem to be $100 for 50W and 0.075W per square foot or $15 per square foot, assuming no space wastage on the roof then the theoretical maximum power would be a maximum of 2286 watts. That would cost $4500 - more than the bus cost, which would be crazy. Assuming a generous 10% power production that would be 300 watts or 1500 watt hours a day. My microwave used 10A. That's 1200 watts! If the microwave (which took 15 minutes to cook a plate of food from frozen) was used 4 times a day, that would be about the total production of the entire solar array.

It is my opinion that solar power has to be used sparingly. As can be seen from the fact two 10W panels barely power two CPU fans, the claims on solar panels about power production are total bullshit. In fact, the economics don't really work out either. My $60 spent on panels would have bought 120 D cells at the dollar store which would have powered my original 3V fans for about a year!

Thus, I'm stopping at panels on the rear for now. I will put extra insulation in the rear panels though as where I put insulation, the steel is less hot. I'll have to see if I can do better than the little cans of Great Stuff though!

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