Whorled View

April 25, 2008

REALITY CHECK: Electric Vehicle Fueling Stations

I thought this wasn’t doable until I ran the numbers. See … it depends on how the Electric Vehicle (EV) is built. You can trickle charge them overnight, or you can rapid-charge them in a matter of minutes if you have enough juice, but the battery must be designed for one method or the other. Right now they’re all designed for trickle charging overnight.

The problem with rapid (5 minute) charging is the amount of energy throughput required. The electrical grid would need some massive restructuring to provide the kind of throughput needed, which is very very expensive. The other option, which is far more likely than to get the power companies to do anything, is to generate it onsite via wind power or solar power.

The wind power is a slam dunk. Just one of these windmills can easily generate enough to charge 6 cars at a time … assuming it’s windy enough. This would be a no-brainer in many places. The Windmill will be around $500,000. The whole thing (including infrastructure power conditioning, and storage) should cost around $1.5 M. Not bad. No wonder wind power is by far the fastest growing renewable.

Solar is a little trickier. Ideally you’d put your panels over a parking lot for a shopping center or supermarket. You could also put them directly on top of the shopping center or supermarket, but I think a covered parking lot would be desirable enough for the shoppers such that the owners would probably provide the parking lot solar space for free. To support rapid filling 6 cars simultaneously you’re going to need about 6 acres of panels. A large parking lot should provide this, assuming that the panels will only cover parked cars. If more space is needed, a patchwork could be put over the low-traffic areas.

That’s not bad (I expected the space requirements to be more demanding). How about cost? About $3.5 million just for the solar array. Add another $2M for infrastructure (including panel supports, wiring, energy storage, and power conditioning) and you’re into it about $5.5 million. Sounds like a lot (especially compared to wind power), but if you charge $0.05/mile, which is about 1/4 of what gas currently costs for most Americans right now, you can turn a profit.

How much profit? At $0.05/mile you’ll be selling energy at twice the rate that grid normally costs, or $0.17/kWh. Assuming that the cars will be charged at a rate of 500kW (167W/car), and that you’ll charge an average of 3 cars (a generous assumption, imo) at a time between the hours of 7am and 10pm (15 hours), you’ll gross about $465k/yr from motorists. Then you’ll sell the excess back to the grid generating an additional $150k/yr (remember you’ll be using some of this excess in the evening and in some seasons). That’s not bad, but it’s not spectacular considering your loan and the costs of running such a business. In fact, it’s not much better than what you’d make just selling all the electricity back to grid, which is what you’ll do with the excess anyway. If you sell it back to grid you’ll still make about 70% as much per kWh, without having to deal with the bother and costs of running an EV Fueling Station.

Here’s the kicker though … just about the time you’ll have the original loan paid off … say in 20 years, it will be time to replace all the solar panels, costing you another $1.8M in today’s dollars (assuming solar prices will have dropped in half), but at least after that your net will be higher than it was with the original loan.

Still every penny counts when you run a business, so it looks like a good deal, and you’ll be providing a service to the EV community. It is however contingent on three extremely critical things: 1) that it’s sunny, and 2) that they build cars for rapid charging 3) that people will rapid charge their car at 2X the cost of what it costs them to do it at home overnight.

This last point sinks the whole deal for me. If convenience and the mighty dollar is king (and I think it is) people would prefer to just plug in their car when they get home, saving them money over the cost of rapid charging at the supermarket. If someone forgets to plug in their car at night, they’ll just generate their electricity on the fly with a built-in gas-powered generator. That is, incidentally, how they’re making the next generation hybrids, and all future EV’s will likely have that feature so you’ll never be stranded.

So there you go. Conclusion: Based on my analysis EV’s will NEVER be rapid charging nor will Electric Vehicle Fueling Stations exist for rapid charging purposes. That is unless all the solar cell manufacturers are bought up by the oil companies who then will then get into bed with the auto manufacturers, who will then agree to only make rapid-charge EVs that can only be charged in EV fueling stations (not at home).

Now that’s a scary thought. If that happens (doubtful) then this is a viable business. Due to the high upfront costs it’s maybe twice as profitable as a normal gas station is today (based on my google research). But in this scenario where Automakers produce only rapid-charge EVs, which I think is unlikely, this would be a sure thing. Note that there will be limited places where this can be done: shopping centers and supermarkets where there is enough space to also put a gas-station-sized EV station.

PS- here’s the math for those who like math:

Solar Array Energy Generating capability:
Most of the EV cars over the next 10-15 years will likely have 15kWh storage capacity as Advanced Li-Ion batteries. These batteries can be made to completely charge in 5 minutes, but that’s like 15kWh in 5 minutes, and if you have 6 cars doing that simultaneously, that’s 90kWh in 5 minutes That requires a energy generation capability of 90000Wh *(60min/h)/(5 min) = 1MW (approx).

Solar Panel Space Requirements:
On average a good 3×8 panel will provide about 100 Watts, so you’ll need 10,000 of these panels (minimum) assuming it’s sunny all day (1M/100=10,00 panels). That will take up 6 acres of panels (3ftx8ft*10,000 = 240,000ft^2 = 6 acres).

Solar Panel Cost:
Today if you buy in bulk and if you’re lucky you can get solar panels at $3.5/Watt. This cost has not changed much in the last 10 years. It isn’t expected to drop much in the next 10-20 years even with an explosion of supply simply because demand is so high, and as soon as the price drops demand increases to stabilize the price. 1 Million W at 3.5/Watts = $3.5 Million just for the solar array (infrastructure not included).

Gross Annual Income:
($0.17/kWh which is what you’re charging) * (500kW used to charge 3 cars continuously) * (15 h/day) * (365days/yr) = $465k


April 14, 2008

Solar Cells on Cars … wouldn’t it be … lame?

Filed under: conservation,earth,ecology,economics,energy,environment,solar,Technology — lullabyman @ 6:31 am

“Solar cells on cars! Wouldn’t it be great?! I can’t wait to get mine and stick it to the man and never have to pay for gas ever again!”

This is probably one of the most common things I hear when I talk to most people about electric cars or solar technology (both subjects I know just a little about). I admit … it is a great dream. It is also a dream based on the assumption that solar cells are getting somewhat close to being about to provide the power to operate a car, which incidentally consumes a tremendous amount of energy to transport you from “A” to “B”. This is a concept that most people have no clue about: gasoline packs an amazing amount of punch. The energy density found in this liquid that you just pump out of the ground is phenomenal.

Then you have solar cells, the alternative. The sad fact is that the best commercially available solar cells only convert 20% of the sun’s energy to electricity. Try this: go outside when it’s sunny and notice how hot the sun feels on your face. Then stand behind some tall trees that filter out about 80% of the sun’s direct rays. Suddenly get cold? That’s about how much of that energy is available to you with the very best (ie. ugly) commercially available solar cells. Sexy solar cells (black and curvy) are at best half as efficient (less than 10%).

So the next question is: how far will that take you if you tile them all over you your Tesla Motor’s Roadster (a super efficient Electric Vehicle)? I’m thinking around 4 miles/day. Tesla Motor’s did the analysis though and said you don’t want to put them on the hood, so you’re looking at 2 miles/day. See the math for yourself (they did it so I don’t have to )<:).

So using the best commercial solar cells possible on a very efficient road-worthy EV you get a range of 1 mile per day from where you live (remember you have to drive both ways).

Hmmm … One mile? Why don’t you get a bicycle instead.

But what if …. what if some quantum-dot nano-particle super-ultraconducting-lattice PV solar cell was invented that was 80% efficient? Yeah, that would be cool… very cool. You’ll be able to drive 16 miles per day in your Tesla Roadster (up to 8 miles from your house)! Of course, you could only do this when it’s at least moderately sunny. Also, your car is going to be hot and muggy inside because it sat in the sun all day. Plus, your car would probably cost a million dollars and won’t be available for 50 years or more when just such efficient solar cells are invented (not being a pessimist … just a realist).

But hey … you’d get bragging rights. 😉

“My car is powered by solar. Neener-neener.”

“Oh is that right, Smarty pants?”

“Yeah, powered by solar, you knuckle dragging galoot.”

“Actually I’m more of a car-pounding galoot”. [smack!] “He he he … Now what is it powered by, Smarty pants?”

Yeah, Ouch! High efficiency solar cells are quite fragile. That’s also why you don’t want to put them on the hood of your car. Or on the trunk. Or … maybe anywhere on your car.

So what about the solar car challenges that schools compete in every year where they race their solar cars over 100 mph and travel like 100’s miles/day? Have you seen those things? They’re marvels of engineering.

They’re also very fragile, designed for one very cramped person with extremely limited visibility, maneuverability (designed to only go straight), no AC, no heat, no lights, and no safety (relatively speaking). Consider this … in 2004 Andrew Frow, (from U-of-Toronto) was driving the winner of the American Solar Challenge Safety Award when he unexpectedly swerved into oncoming traffic and was instantly killed. A tragedy for sure that should never be trivialized. What’s important though is that similar accidents happen at events like this on almost an annual basis (although that was the only one to collide with a car resulting in a death) and the racers and designers are indeed as careful as they can be but these cars are built only to win competitions, not save lives.

No, using the Solar Challenge Cars as justification for Solar powered commuter cars is kind of like jettisoning airplane passengers over destinations because people successfully sky dive. I’m thinking you probably want your car to be 1) comfortable, 2) fit multiple people, 3) have AC, heat, air, 4) windows, 5) good visibility, 6) maneuverability, 7) safety features, 8) survive a crash from any side, 9) have room for groceries, 10) look good, 11) be in your favorite color, and 12) be functional after a basketball bounces off it.

BUT YOU CAN HAVE THAT IN A SOLAR POWERED CAR TODAY! Just get an electric vehicle and charge it’s batteries with solar panels on your house. Go with the Toyota Prius (or hold out for the Chevy Volt if you want to look cool). Better yet, if you live near the Mojave desert in California then forget about solar panels because the electricity in your house is already solar powered.

A MUCH CHEAPER WAY TO DO IT: Yes, in fact, if you put solar panels on your house you can sell the electricity back to the grid at a 2:1 price. So why would you put solar panels on your car anyway? You save twice as much $ putting them on your house.

NEV: Now, admittedly I’ve been a curmudgeon about this issue, and I should at least throw the “pack your own solar” fans a bone. There is a viable “pack your own solar” Car in the form of a “NEV” (Neighborhood Electric Vehicle), but I’d be scared to drive it on any of our streets. Still, if you like electric golf carts and you live in a leisure neighborhood and you don’t like to walk it might be just what you’re looking for: http://www.sunnev.com. It’s cheap too!

They say it does 3 mi/day. The economics works because it’s so light, and it’s light because it’s a glorified golf cart. With increased weight the power requirements will go up porportionally. A comfortable sedan is about 10 times heavier and will additionally have a lot more friction (internal and against the road).

Don’t get me wrong. Solar is great. I personally think it will play a very major part in the future of the world’s energy solution, including mobility. Just not in the way that you probably envisioned it.

In fact, eventually some (may be all) cars will have solar cells embedded in their design but they just won’t really do anything other than keep your battery from going dead, or maybe power a fan that will keep your car cool on the hottest days while it’s parked in the sun (they’ll probably be integrated into your rear window). They already sell after-market window units that do this (you have to slightly unroll your window where the device is located).

In short, sometimes it’s good to remember that when you take the best of all technologies and mix it all together into a single unit, the sum is less than the parts. Solar is one of those things that sometimes acts that way. I’d gladly be proven wrong though by some genius who figures out how to cheaply squeeze a lot more energy out of the sun than our current commercially available solar cells do. Until then, have an extension cord ready, because EV’s will be giving internal combustion engines a run for their money within the next 5-10 years and you’re going to need a lot more juice for them than an affordable solar array will provide.

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