Solar Electric Vehicles

<div class='quotetop'>QUOTE(phidauex @ Apr 20 2007, 02:37 PM) [snapback]427028[/snapback]</div>

Uncle! You know WAY more about this stuff than I do! My comments (which I should not have been so "absolute" about) are based on observed vehaviour of the sytems I'm familiar with. And of course I'm not measuring exact percentage of shade and production. I'm just seening *some* shade causing *some* loss of production. On a large array, you can take a few panels out and still be getting great production.

Great thing you've written here, and I'll go check out your link for sure.

Yup. I have a 2.5 system described here:
http://evnut.com/solar.htm
BP panels and Sunnyboy inverter

I do not yet have a monitoring system in place (beyond my eyeballs and the display) but have been considering it ever since it was installed! I just don't like the idea of keeping a computer powered 24/7 just to monitor my energy usage.

Thanks again for all your great info!

<div class='quotetop'>QUOTE(Tadashi @ Apr 20 2007, 02:59 PM) [snapback]427037[/snapback]</div>

You know as much as I do regarding that solar Prius biz. I just put it on my site since it was of interest to so many. Great on you for putting in a nice big system! I'd seriously skip the panels on the car, and use your roof-top system. It really just is not practical to install panels on the car yet.

 

Sorry, didn't mean to snowball anyone. I design residential and commercial solar systems for a living, AND, I'm a science teacher, so sometimes I get out of control with my explanations.

We use a lot of BP modules. I haven't done a lot with Sunnyboy's (tend to prefer Xantrex for a few reasons), but the newest line of Sunny Boy 6000 and 7000 watt inverters are really nice. I'm in the design phase right now for a 10kW system w/ two Sunnyboys. And I'm starting work on a 200kW system soon. We are considering using 30 Sunnyboy 7000s instead of one central inverter. More power point trackers means more power harvest. At least, that is what I'm hearing from the SMA people.

If you are considering a monitoring system, I'd really encourage you to look at the Fat Spaniel system. You don't need a whole computer running. In its simplest form, it is a small box (the "gateway") that plugs into the inverter, plugs in its little wall wart, and plugs into a Cat-5 cable with internet connectivity. It monitors your system, and uploads that to the Fat Spaniel servers (which are on all the time either way), which then compile the data, and make it available to you at any time, from any place. Our clients love them, and we are considering making them a standard part of our installation. I think all cars should have a MPG graph on them, since immediate feedback about the results of your actions is crucial. Look at all the people who hypermile in Priuses by using the MFD! If EVERY car had that, people could drive any car more efficiently. Same is true with a home. If you have instant feedback, you can make much better decisions.

Check out this Fat Spaniel public system for the Santa Clara water authority system. They've got a pretty slick flash graph made, and it runs on a touch-screen kiosk in their lobby. Very popular. http://view.fatspaniel.net/SCVWD/flash/index.swf

You should also look into SMA's own system, called the Web Box. Its similar, a little box that plugs into the inverter. It has its own web server built in, and can also upload data to the main SMA server. Its not as slick, but is a bit cheaper, and provides most of the same basic functionality.

Both can do things like email you or text message you if your inverter throws an error or has a problem, too.

Note, while I do sell these and other systems, I'm not actually involved with either company, and don't make anything if you buy them! Not trying to sound like an ad, i'm just genuinely excited about monitoring systems.

But enough industry talk!

Solar is good, but probably not there yet for direct power of cars. I've got a few clients who use their PV system to charge neighborhood EVs, like the Xebra, and in a year or three, when PHEV retrofit kits from Calcars are available, I'll be charging my Prius from a PV system.

It may never get there for direct power of cars... Modules are between 15% efficient for basic monocrystalline cells, to 17-18% efficient for hybrid modules like the Sanyo HIT line. But it can't get much higher without a fundemental change in technology, since the theoretical limit for conversion in a silicon junction is 30%. We are already more than half the theoretical limit, which is pretty darn good. I'm not worried about making more efficient modules (though I'm glad the technology is evolving). I'm more concerned about making existing modules cheaper. Our country has a limited amount of money, but a practically unlimited amount of roof space. The limiting reagent isn't surface area, its money. I'd rather install 100 15% efficient modules than 10 20% efficient modules. The world gets more energy with option one.

Peace,
Sam

 

<div class='quotetop'>QUOTE(phidauex @ Apr 20 2007, 07:33 PM) [snapback]427132[/snapback]</div>

Thanks again Sam! No harm, no foul. I sell systems, but certainly don't design them, or know as much as you do.

Are we going to see these using WiFi? If they did, I'd get one tomorrow. Running a cable to the inverter just doesn't make me happy!

I did just look at it after you pointed it out. Seems that it needs Cat5 as well? Give me WiFi, and I'm on board in an instant!

This is exactly what I tell people. So many customers want to "wait until they have better efficiency." Why? Efficiency doesn't matter except for surface area concerns. The only thing that really matters is dollars per watt. If you can buy super efficient panels for 10x the cost of less efficient ones - you are paying 10x as much per watt! Some folks refuse to grasp that. I do think that the next breakthrough will be in cost, and NOT in efficiency as most people seem to want.

 

Solar will become practical for cars when organic PV is practical and auto mfgs can build the PV into 80-90% of the car's surface area at a reasonable cost. Si bases solar will never make sense on vehicles for all of the reasons that people have already pointed out.

phidauex, nice post on modules. Shade can be a real bugger. That's why while we're looking for a new house the southern exposure will be a critical factor in what we decide to buy.

 

<div class='quotetop'>QUOTE(tripp @ Apr 20 2007, 11:11 PM) [snapback]427221[/snapback]</div>

Phidauex's explanation of shading shows why solar is unlikely to work on cars: Cover the entire car's surface with solar cells, and something like half of them will be in shade all the time, with no way to plan for which cells will be in shade at any given time.

And as darell pointed out, efficiency becomes a concern where area is limited, and on a car, area is very limited. Look at solar race cars: huge, super-lightweight things with enormous, flat tops for the solar arrays, all mounted on flimsy high-efficiency bicycle tires.

House roofs are the place for solar arrays, not car roofs.

 

hours of sunlight is a factor, but the angle, which has been mentioned plays a bigger factor. currently, my area enjoys 15½ hours of sunlight and that will increase to over 19 hours by summer, but i will never see the full power input simply because of the low angle of our sun "overhead". (more like over the shoulders here)

but the ability of a panel to collect that much power means that solar charging stations that sit out in the sun all the time, can store a lot of power in a relatively small space and with computer controls to angle the panels to collect the maximum amount of rays, i think even in the rainy Pacific Northwest, we can actually use them albeit more limited than maybe CA, but we now have solar powered traffic lights, so it can be done.

 

Another thing to consider is just the general 'cost to society' of various power generating applications.

Our world is moving away from a 'single source' energy culture, and moving into a multi-source diversified energy culture. This will actually be the first time our human civilization has had diversified energy since before the adoption of coal.

The current mindset is, "Fossil fuel provides all our energy. If we need energy somewhere, just bring fossil fuels along." But that doesn't work for renewable energy. You can't just say, "all our power will come from wind, so we'll put wind turbines everywhere we need power." The question now is, "What resources does this region have? What can take best advantage of them?" Put wind in windy places, solar in sunny places, geothermal in geologically active places, etc.

When you manufacture a solar cell, you know that it isn't going to 'wear out'. There are solar cells that are almost 100 years old that are still operating at more than 80% of their original power. What does happen is they get broken, dropped, lost, damaged, etc.

When a solar cell is born, you have damaged the Earth. You expended energy to make it, you created pollution to transport it, etc. The newborn solar module is a liability. So you ask, "Where can I put this, to allow it to redeem itself best?" If you put it in a marginal location, and it only creates 1/3rd of the energy it took to make it before it is damaged, then it hurt, more than it helped. But if you put it in a great place, and it makes 10 times the energy it took to make it, then it has redeemed itself, and begins to help the environment.

So if you built some very high efficiency modules at great prices, you would ask, "Where will I get maximum effect from these?" The answer will never be, "on a car". The only use for solar cars would be distant, remote locations where recharging isn't an option. In those cases, you need renewable energy, not as an environmental choice, but as an operational choice.

A solar powered car still needs a battery. So why not make the battery a little bigger, and then put the solar panels on a building, where they will produce many times more power. You sleep in the same place every night, and you park your car every night. Just let it recharge. You need good range to be practical, but if you can go 200 miles on a charge, you are in good shape. The world will be a cleaner place because you chose to maximize the effect of your power generating system.

So like I said, seek to utilize renewable energy sources in the most effective way possible. Vanity renewables don't do the planet any good, and make poor financial sense. It would be fun to have a car covered in solar panels, but it would not make the world a cleaner place to live, and it would cost you more in the long run.

Peace,
Sam

 

Sam -

That was such a good response that it inspired me to create a new FAQ entry on my EV site... since this really is a FAQ: Why not just put solar panels on the car so we don't have to plug it in?

Your answer is fantastic and well reasoned.

 

Yes, Si based cells don't make any sense on a vehicle, but what about organic, plastic based cells? They don't contain Si and are integrated into the body/windows of the car itself. We could do this today but it would cost a fortune and the ROI would probably be well beyond the effective life of the car (even an EV!). I don't know what these things cost. I know that the efficiency is still pretty low (< 8% I think). However, companies like Konarka are developing these technologies and they have the potential to have a huge impact. Who knows whether they will or not, but it's a distinct possibility.

So to say that solar cells will never be on cars is, perhaps, a little short sighted/narrow minded. Classic Si based mono/poly crystallines cells won't (more than likely) but they're not the only game in town.

 

That is too bad about car solar panels not being economically viable yet.

Actually, it was you (Darell) that piqued my interest in solar panels and much to the dismay of my wife when I just into something I leap in with both feet. I also got the "SMA monitoring card and software". I hope this is the webserver you are talking about. My system is not due for installation for a couple weeks.

So would it be worth the extra cost (BTW how much would it cost) to install a system that tracks the sun and tilts your panels towards the sun at the optimal angle? Or is this even available yet?

 

<div class='quotetop'>QUOTE(tripp @ Apr 21 2007, 05:50 PM) [snapback]427510[/snapback]</div>

Until you have covered the entire roof of your house with solar panels, putting them on your car is wasteful. Half your car is in shade even when the car is in full sunlight. All of your car is in shade all the time it's in the garage, and sometimes it's in the shade even when it's out of doors.

I'm not saying there'll never be solar cells on cars. I'm saying they are much more productive on your house.

 

They may be more productive on the house but if it costs about $5k on the car that is more attainable than trying to spend $20k for the house. I would rather see people do what they can then to not do anything.

If I had solar cells on the car I would not park it in the garage except for days when there is expected hail.

I thought I saw an article about a special paint that had been developed that acted like solar panels for odd contour sides and could have any color.

 

Tripp, I see what you are saying about low cost modules with future technologies, but I would still ask the question, if they are cheap enough to make that they will pay back their energy cost even on a car, then why not put them on a structure, where they will pay back their energy cost 5 times over? If we still have 'ideal' spaces for solar, it doesn't make a lot of sense to use it in non-ideal spaces. But you are probably right, if they get easy enough to make, and they can pay themselves back on a car, it might make sense in some situations.

If PV gets that cheap to make, I'd be so happy, that I'll gladly eat my words.

Tadashi, about the tracking system... They usually are not worth it. But sometimes they are. If you are mounting your system south facing on a roof 20-30 degrees in angle (4/12 to 6/12, in architectural terms), then you could gain maybe 4-5% more generation with a single axis tracker (up/down), or up to 30% more generation with a two axis tracker (side to side and up/down).

Here is the thing... All trackers require maintenance. And they break... And sometimes they do crazy things like point the wrong direction in the morning.

A two axis tracker needs to go up on a pole (costs more than a roof mount), and then has the extra expense of the tracker. If in a few years it breaks, and you can't afford to fix it, or a future owner of the home doesn't know how, then the system will produce much less than a fixed tilt.

This is even true with adjustable tilt systems that you adjust twice a year for optimal tilt. While you remember to do it you get a few percentage points of generation, but when you forget, or lose interest (not accusing you of this personally!) or a future owner loses interest, or does it wrong because they don't know what to do, then the system performs way under what it should.

So I guess, if you have a very limited amount of space and need as much generation as possible, and have the means and intent to provide continuing maintenance, and a willingness to outlay more captial at the beginning, then they make sense. But this isn't most people.

Peace,
Sam

 

<div class='quotetop'>QUOTE(Tadashi @ Apr 22 2007, 07:43 AM) [snapback]427750[/snapback]</div>

It's always going to cost LESS to install the same capacity on a house roof as on a car, because with a car you have irregular contours to match. If you can only afford to spend $5,000 on PVs, you are much better off putting those $5K worth of PVs on your house, than on your car.

 

<div class='quotetop'>QUOTE(phidauex @ Apr 22 2007, 03:39 PM) [snapback]427938[/snapback]</div>

What about apartment owners or renters. They can't just slap up an array where ever they want. What about traveling? Of course putting arrays on the house makes sense... it makes sense without a car. I'm looking further ahead to what I hope is a totally different kind of PV. Many of the nano/orgainic designs don't suffer from the shading problem so that's not even an issue. They're also vaporware (if they're even that far along) for the foreseeable future. However, should something like this become a reality it will be far cheaper to produce than current state of the art, use way less energy to produce, and be flexible. If they can every get anywhere with quantum dots then the efficiencies will also be considerably higher than what we have now (though Spectralabs has broken the 40% barrier, which is great news).

Anyway, the point is that there will likely be a time when it would be stupid NOT to integrate PV into cars. It's not around the corner but there's just too much free energy sitting around and I think the ROI will be a trivial afterthought. Again, This ain't gonna happen tomorrow, oh that it would.

 

<div class='quotetop'>QUOTE(Tadashi @ Apr 21 2007, 06:55 PM) [snapback]427535[/snapback]</div>

Ah... in the middle of replying, I see Sam already got to it. In general, it is not worth the extra expense and complication to add trackers. In some, few cases it can make sense, but rarely. Oh, and yes they do exist, and have for some time!

<div class='quotetop'>QUOTE(Tadashi @ Apr 22 2007, 07:43 AM) [snapback]427750[/snapback]</div>

And Daniel already got this one! If you can only afford $5k, then put that $5k to work for you. No sense in wasting the money just because it is limited! (that sounds odd, eh?)

So amzingly inefficient that it is hardly worth discussing at this point. But maybe some day!

<div class='quotetop'>QUOTE(tripp @ Apr 23 2007, 09:39 AM) [snapback]428404[/snapback]</div>

One point I'd like to make in this discussion (that sort of fits) is that while the future will be very different indeed - we have many examples in the past of poor energy use that we've been plenty satisfied with. Look at how we use gasoline in automobiles! There are so many better places to use that gasoline, but we happily dump it into our tanks and run around with it, throwing over 75% of it away to move our heavy machines

 

I dont know jack about what TH you guys are talking about, but I have been places that have no electric grid & depend completely on solar for everything, every day & use inverters @night. Is it not possible to charge the "BIG" Battery during the day while the PRIUS is parked????????????????????????. That just freaks me out that, that is not a viable option on this car. Not to mention the rear wheals dont do diddley squat Xcept roll, PUT them to use too! "I am no science teacher" but I am a very pragmaticly learned 122 IQ 10th grade educated, High school graduated, common sense, song writting genius. & I am not qualified to expect Logic? Probably not. However the fight between logic & unseen popular science will endeavor?.

Somebody please tell me there is a way to SOLAR charge my "BIG" Battery while my dashboard melts in the SO CAL SUN???????????

 

<div class='quotetop'>QUOTE(Jarhead 0311 @ May 26 2007, 05:27 PM) [snapback]450563[/snapback]</div>

As it comes from the factory it most definitely is not an option. Hang tough for a few more years, and we'll finally have what you're looking for.

You've got me stumped on this one. Maybe your brilliance went right over my head? You want the rear wheels to drive? Or do you want them to generate power? (please say it is the former, because if you mean the latter then we're talking about perpetual-motion machines).

Only if you spring for the ~$10k plug-in conversion first.

 

Ah, you guys are all missing the point of the Prius solar panel roof. It's the "next big thing" for the boys who want their car to look "cool". I love the look of solar panels, especially curved ones! I wouldn't pay $4000 for one though.

Grills, 21" wheels with "spreewells", suspension that moves to music, and solar panels on the roof! Hey, maybe even a solar heated hot tub. We'll have to have the Prius "stretched" though.

On a more serious note, I have a "recycled" tiny (one foot square) amorphous 12V panel (glass cracked so could no longer be used for remote weather stations outdoors). I'm hoping to use it to maintain the 12V battery charge in my Prius. If I can figure out a place to put it inside the car.

 

<div class='quotetop'>QUOTE(David Beale @ May 26 2007, 07:28 PM) [snapback]450619[/snapback]</div>

A PV panel inside the car isn't going to do much for you. The windshield is a pretty good UV filter - by design.