Solar Elelctric supplementary power

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7,077
Location
Ontario, Canada
Cars use electricity, but the engine-alternator system is very inefficient, and costs a lot more than power from the grid. This is a potential place to apply photovoltaics. When you're driving on a sunny day, solar panels on the roof of your car could be taking some of the load off the alternator, saving fuel. If you have one the hybrid cars or, pickups that will be coming out soon, a couple of solar panels can charge your battery pack, so the engine doesn't have to run as much.
 
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43,658
Location
'Stralia
I remember a great article on a guy who put solar cells on the garage roof, and converted his electric lawn mower to solar power. It was a really cheap cell, a second hand mower with a bad charger, and a shed roof that sits there 24/7. Remember that everything that you get for free is free. Analyse what your situation is, and the capital you need to gain in operating costs. I think I might look for a Moke, and a half carport of cheap cells.
 

oilyriser

Thread starter
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7,077
Location
Ontario, Canada
I estimated a car burns about 0.8L of gas to make one kW-hr of electricity. You could also use a storage battery, and charge it on the grid. In Canada the cars have DRL's, which are lights up front running during the daytime. Instead of doing this by running the headlights at reduced voltage, making them incredibly inefficient at making light, you could use white LED's, which are about as efficient as fluorescent lights. The DRL's use maybe 80 watts of power whenever the car is in gear. That requires about 100W of mechanical power going into the alternator. If a car uses 15 hp to move, on average, 100 watts is 0.8% of the average engine power. If you cut that to 0.19% by using white LED's, that would save more fuel than switching from 5w30 to the more expensive 5w20 motor oil does, but at a cost of only about $20 per car over it's lifetime. Some cars use special small light bulbs for the DRL, which is more energy efficient than the headlights, but it's still not the best choice, economically, since even 50 watts over the 4000 hour life of a car will cause about 160 L of extra gasoline to be burned.
 
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1,979
Location
Houston
On a car, the weight added by the solar cells will more than negate any savings by reducing alternator load. The cigarette lighter trickle chargers were almost a total waste, it would take weeks of direct sunlight to get a dead battery to where it could possibly crank an engine. However, just for fun they can't be beat. I got a couple of bare arrays (~6"x8", 6v) about 15 years ago, they made a supply that powered a small fan (at about 80%) that I rigged to ventilate the car on those hot days. it was fun if not totally inefficient and a real bother. The main idea I was working on at the time was using a solar cell on the backside of a notebook computer display to stretch the battery life. Battery chemistry advances and the cost of the cell and it's frailty pretty well doomed it to a research and no development project but it did work.
 
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47,770
Location
Everson WA - Pacific NW USA
It just may work with the folks that add the supplemental batteries to Toyota Prius hybrids. These batteries do need to be plugged into the grid for trickle charging but add beaucoup MPG's. A solar charger may help!
 
Messages
709
Location
CT
quote:
Originally posted by labman: I already have an electric mower with a bad charger. Where do I find cheap solar cells?
I just read a recent article on a man that converted a Toro gas mower like Shannow mentioned. You can get the article by going to Solar Home and downloading the free issue #107 June/July 2005. The article starts on page 66. He used a 12volt Shell SP75 solar panel that retails for $300. You could probably find it for less since 24V and higher are more popular now. Also, you might be able to score a used panel since maximum output of the PV panel is not critical in this application. Here's an article on Used Panels. [ August 30, 2005, 09:58 AM: Message edited by: Razl ]
 

oilyriser

Thread starter
Messages
7,077
Location
Ontario, Canada
quote:
Originally posted by kenw: On a car, the weight added by the solar cells will more than negate any savings by reducing alternator load.
True. Conventional panels would weigh enough to offset the savings. We might have to wait for the thin film ones to be made with higher efficiency.
 
Messages
709
Location
CT
quote:
Originally posted by oilyriser:
quote:
Originally posted by kenw: On a car, the weight added by the solar cells will more than negate any savings by reducing alternator load.
True. Conventional panels would weigh enough to offset the savings. We might have to wait for the thin film ones to be made with higher efficiency.

What about the new roll-up panels that are light and thin. I think most are small because they are intended to be thrown in a backpack but I don't see why they couldn't be made bigger.  -
 

mjo

Messages
417
Location
Michigan
quote:
Originally posted by Pablo: It just may work with the folks that add the supplemental batteries to Toyota Prius hybrids. These batteries do need to be plugged into the grid for trickle charging but add beaucoup MPG's. A solar charger may help!
You're right. Here's an article you might find interesting about a toyota Prius. I use something like this on my car: http://cgi.ebay.com/ebaymotors/SOLAR-PANEL-12-V-ALL-PURPOSE-3-BOXES-ALL-NEW_W0QQitemZ7997274169QQcategoryZ63687QQrdZ1QQcmdZViewItem My battery is about 5 years old and still working.
 
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10,843
Location
Nokesville, VA
Going back to the case of taking load off the alternator by using solar cells..what about using a deep-cycle battery and taking the alternator completely out of the circuit? I looked at the wiring diagram for my 1988 Mustang and it appears that all one has to do to disable the alternator is to put a switch in the 12V wire which goes to the regulator. No 12V to the regulator, no power to the field coil and the alternator produces no output. To replace the output from the alternator, one could use a deep-cycle marine battery, maybe wired in parallel with the existing battery if not completely replacing it...These are available at Costco in capacities of either 75 amp-hours or 105 amp-hours. Then one could charge the deep-cycle battery when they get home.
 
Messages
709
Location
CT
[LOL!] So your conversion starts this weekend, right? Solar is not mainstream by far but it is catching on, especially in states that subsidize the cost. Another thing to keep in mind is that a solar PV is terribly inefficient to use for heating your home. For that, a solar water heater is cheaper and more practical. So a true 100% solar home would use systems, one to power the lights and appliances and one to heat the home. Maybe that’s another reason for your $328,000 estimation. I know of this guy in Charlestown, RI that installed a grid-tie PV system (he still uses oil to heat the house). Install price was about $20,000 but with the state's rebate and tax savings, the net cost was around $12,000. His payback is about 10 years, assuming the cost of electricity remains the same, which we know won't. $12,000 is still a lot, but if you plan to stay in your house a while, it can be worth it. Residence in other states like CA, have seen payback in less than 5 years. Recently, scientists have discovered a way to capture infrared light (before now, it was theorized as impossible!). This type of plastic solar cell is much smaller (utilizing nanotechnology), more efficient and cheaper to produce. A PV system is about 12% efficient but an infrared is about 30% efficient. And like paint, this plastic cell can be sprayed on a wide array of materials, creating a highly portable and flexible solar panel! Hopefully, it will be available to the public in less than 103 years [Big Grin]
 
Messages
659
Location
Minnesota
Three factors come to mind for me. The weight factor that could negate the gains, followed by the form factor that causes drag. The final factor is the efficiency of cost, how much will you pay for this, the lighter and thinner it is the more expensive so in the end it would be difficult to say you could ever be ahead. You would be better off converting a car to electric, find a large solar grid for your roof and use it to power your house in conjunction with your normal electric source. They have devices that will let you provide solar power in conjunction with your normal power and when you provide more power than you use it will turn your meter backwards. But most people would probably forget about the electric car to think they will make more money by spinning their meter backwards, but it probably isn't the case unless you don't use air conditioning and don't have a computer running all the time because most systems are usually set up to run just an appliance or two, including a refrigerator, a few lights, and a gas furnace in the winter.
 
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