Featured Post

Plug In Drivers Not Missin' the Piston

This is the Kodak Moment for the Auto Industry. Electric vehicles are here to stay. Their market acceptance and growth will continue....

Sunday, June 17, 2018

Tesla Roadster Rocket Thrusters Explained By Tesla Patent


During the annual Tesla shareholder meeting, CEO Elon Musk announced that Roadster 2020 would have a SpaceX option package that will include rocket thrusters. Later Musk tweeted a few more details:  the thrusters won’t actually combust; instead, they will expel high-pressure air to give the Tesla an extra boost of acceleration.

Industry experts and the tranche of the internet that follows Elon Musk have been speculating and arguing about these rocket thrusters since their announcement. Will they be functional, whimsical and decorative (just there to signal your extravagance), or some combination of all of the above?

SpaceX’s Falcon 9 rockets use composite overwrapped pressure vessels (COPV). These tanks are made out of a thin metal liner wrapped in carbon fiber, and they’re fairly lightweight and a great way to store a lot of pressurized air in a very small space. This is what Tesla plans to use in the Roadster. Using COPVs in vehicles is not a new idea; some buses and trucks use them to store compressed natural gas, and fuel cell vehicles use COPVs to store hydrogen, but the gases in these tanks are used as fuel for the vehicles, not expelled as direct thrust.

Problems With Air As Thrust 

When someone talks about putting an air rocket thruster on a car, the easy assumption is that these "thrusters" would be used for thrust by ejecting air and propelling the car. The experts have brought up many problems that this could cause:
  • To accelerate a vehicle in the weight category of the new Tesla Roadster, the air would need to be expelled at super high speeds. Some have calculated that the air would need to exit at more than 1,500 MPH to accelerate the Roadster. Using this at a stoplight could propel debris into the windshield of another car or a nearby pedestrian. If implemented this way, this potential hazard could prevent the thrusters from being street legal. 
  • Expelling air at high speeds would be exceptionally loud.
  • Repressurizing the tank with the large volumes of air this would require would use a lot of energy from the battery pack. 
Sam Abuelsamid, a senior research analyst at Navigant, an advisory firm for the auto industry, told The Verge, “It’s the most ridiculous thing I’ve ever heard of.”

Perhaps Tesla engineers have discovered ways to avoid all of these issues or perhaps they have something else in mind. Patent number 9,272,595 B2, issued to Tesla, might give us a hint to the real intentions that Tesla have for these "rocket thrusters".

Tesla Patent

The patent is titled "Passive air bleed for improved cooling systems." Have you ever used a can of air spray to clean your keyboard or blow dust out of your computer? If you have, you might've noticed that the can gets cold and might even frost over. The can gets cold is due to a thermodynamics property known as adiabatic cooling. A gas, initially at high pressure, cools significantly when that pressure is released. Tesla's patent uses this property to make a better cooling system.
Figure 5 of Tesla's Patent - a radiator employing a passive air bleed device

Figure 7 of Tesla's Patent - a drive unit for an electric vehicle incorporating an external passive air bleed device

Hot Lap, Overheating At The Track

Tesla does not make slow cars. They are known for their impressive zero to 60 and quarter-mile times. The performance demands of a hot lap are, however, very different from those of a 0-60.

When attempting a hot lap in a Model S, Car and Driver found multiple problems with the car. At the Virginia International Raceway, the Model S went into reduced power mode in the middle of its first hot lap. In the Tesla racing community, it is common knowledge that the Model S has issues on extended runs at the race track. As Teslarati notes, the electric sedans have a tendency to overheat in one lap or less at most courses. One of the more well-known examples was when a Model S was unable to maintain full power through the mountainous "The Green Hell" Nordschleife section of the Nürburgring.

Unlike the Model S, the new Roadster will be a track car. It will be in the hypercar performance range. It will need better cooling of the high-power electronics and batteries.

Would Adiabatic Cooling Work?

Now that we know the problem the Roadster designers are trying to solve, let's look at this potential solution and see how it fits with Musk's rocket thrusters tweet.

The tweet says it will improve acceleration, top speed, braking, and cornering. Certainly, all of these things rely upon cooling. With acceleration and sustained top speed, the high voltage systems and batteries need to be cooled to prevent power reduction. With braking, the brake pads need to be cooled. In normal driving, an EV can use regenerative braking; this is not the case at the track. Hard braking when heading into a turn requires the friction brakes. Corner after corner can take its toll and really heat the brakes.

Cooling With a Side of Downforce 

If cooling, not thrust, really is the primary function, these thrusters would not, necessarily, be on the back of the car. But once you have them, they can supply some thrust, so how could it best be utilized? Since cornering and acceleration require traction, the most likely place to put them is over the tires. Here, a small amount of downforce could affect performance significantly. Allowing the tires to stick to the road allows the torque of the electric motors to be used to its fullest.

How this could help allow a Tesla to fly, I'm not sure, maybe a couple of the thrusters will point down. Maybe Musk meant figuratively flying, as in going fast. Maybe he was actually just joking. Musk did say there would be ten of the thrusters. Perhaps two over each wheel and two pointing at the ground. If there are some pointing at the ground, I just hope the button to activate the fly feature on the touchscreen looks like this:
500 points to the first commenter to identify this.

Recent Tesla Stories:

Tesla Competition: Culture Eats Strategy!


http://ts.la/patrick7819

Monday, June 11, 2018

The Rules Of EV Charging

Plug-in vehicles of all types are becoming more popular. The EV community is no longer just you and a few of your friends that meet up every so often to talk about the latest in battery management systems. As an EV community, this is what we want, a growing community of EV drivers.

As EVs become more mainstream, people are not defining themselves by the car they drive, they are just trying to get from point A to point B. Today, you are more likely than ever to run into someone at a charging station that you've never met.

These new drivers might have different ideas than your local community about charging etiquette. To help clarify things, here are some clear simple rules.

The rules are:
  1. First come first served, period.
  2. Move as soon as you have enough*.
  3. Always have a plan B for charging.
  4. You are only "entitled" to use a charging station if you own it. If one you need is in use, you can ask for a favor and appeal to their sense of charity, or try to negotiate/bribe your way to a solution, but don't be an entitled jerk about it.
Let's break each of these down to understand them.

Rule 1: First Come First Serve

There are some in the EV community (and even one city) that believe that certain types of plug-in cars have more rights to the charging infrastructure than others. There are three general classes of plug-in vehicles: Plug-in Hybrids, Short Range EVs, & Long Range EVs. For those that do believe there is a canonical ordering of access rights, they tend to put whichever type of vehicle they drive at the top of this list.

I have a different opinion. I refer to it as the 14th Amendment of Charging. The 14th Amendment of the US Constitution guarantees equal protection under the law. The "14th Amendment of Charging" provides equal access for all plug-in vehicles. If the car has a plug and they have a membership to the charging network, then they have an equal right to use it. Having a gas backup option does not diminish the right of access compared to a BEV.

Rule 2: Move As Soon As You Have Enough

When you buy gas, you might "Fill'er Up", but with EV charging, filling up to 100% is generally a waste of your time. If you're on public infrastructure, when your battery is charged enough that you can get to your next destination with a comfortable cushion, then it's time to unplug and free up the spot for some else that may need it.
Charging up with enough is what I call "Lagom charging". Not to be confused with legumes; Lagom is a Swedish word that means "just the right amount". The charge rate of an EV slows as the battery pack approach full. If you don't need the range, there is no need to tolerate the slower rate. Instead, you can avoid wasting time by continuing your trip. Or if you are staying in the area, you can avoid some battery degradation by unplugging before your pack is at 100%. If you have what you need, then the rest of the charging can be done at home, overnight, while you sleep.

Rule 3: Charging Plan B

Charging stations are occasionally blocked, occupied, or down for maintenance. You should have a backup plan. Apps like PlugShare are one good source to find charging locations. Some areas are flush with charging stations and you can find another location easily. In other areas, it is more difficult.

For those more difficult areas, if you have a portable level 2 EVSE, you can grab a few Watt-hours from a friends dryer outlet or even at an RV campground. In a pinch, a standard household level 1 outlet can fill in some small gaps when used overnight.

Rule 4: Don't Be "Entitled"

If you own the charging station, then you get to decide who can use it. Otherwise, it's a public station. Coming up to a person at a public charging and telling them to move because you need/deserve/want it more, is a jerk move.

Instead, try being friendly. You already have something in common and you might actually make a friend.

Bonus Rule 5: Be Friendly 

Since you've read this far, I give you a bonus item suggested by reader Brian H.

I’d add a #5, be friendly and encouraging to fellow EV drivers, regardless of type of vehicle they drive. We all in this together to make life better. ☺

Wednesday, June 6, 2018

1 Million EVs on US Roads Will Happen This Year!

As I write this, there are about 850,000 plug-in vehicles on US roadways. The month of May added about 25,000 of these. Assuming similar sales going forward, the 1 million mark would be hit around the end of the year.

Plug-in sales will likely be better than simply linear over the remainder of the year. EV sales are growing. March of this year had 42% more sales than March of last year. Similarly, April had 47% year-over-year growth and May had 48%. This is exceptional year-over-year growth.

New plug-in cars from nearly all makers are coming out and Tesla is ramping Model 3 manufacturing as fast as they can. With a long list of people waiting for these cars, demand will not be a problem in time into the foreseeable future.

US PEV Sales Actuals & Trend - Actuals data from InsideEVs.com

This is surprisingly in-line with the 2016 prediction we made here.

January 2016 Prediction of US PEV Sales

You can expect to see articles about "2018 To Be The Year of 1 Million EVs on US Roadways" starting to show up in the media in a few months when the trend becomes more assured to occur this year, but you can always say that you saw it here first (in 2016).

http://ts.la/patrick7819

Friday, June 1, 2018

Self Driving Cars: Unfortunately, Safer is Not Safe Enough



The technologist perspective is that once self-driving cars are better/safer drivers than humans, they should be adopted. Looking simply at the numbers, this is logical.

According to the Association for Safe International Road Travel, nearly 1.3 million people die due to traffic crashes each year. This is an average 3,287 deaths a day. Additionally there are 20-50 million people are injured or disabled annually.

If self-driving cars reduced these accidents by 10% then 130,000 fewer people would die and 200,000 to 500,000 fewer people would be injured annually. That sounds great, hundreds of thousands of deaths and injuries would be prevented each year. So logically, even 1% safer means lives saved and that we should all start letting an AI pilot our cars, right? It's not that simple.

It's About Emotions, Not Math

We are not purely logical beings. Even with a great autonomous drive system, crashes will occur. No one making a self-driving system claims that it will eliminate crashes. When crashes occur, people will be hurt and they will look for someone/something to blame. Parents and spouses of victims will demand justice.

If two human-driven vehicles are in a crash, blame will be assigned and justice will usually be metered out. When there is loss, there is someone to blame and target for anger.

When an AI-driven vehicle is in a crash, the same anger and blame emotions occur when there is injury or loss of life, but now the target is different.

Fewer Victims, but Not Necessarily From The Same Population

Say during a given period, there would have been 3000 crashes if humans were the sole drivers. Now place self-driving cars on the roads instead and say there were only 1500 crashes as a result. But the 1500 resulting crashes might not be a subset of the 3000 crashes that would have occurred. Some of them would be such as a tree falling that neither a human driver nor an AI could have avoided. But other crashes would occur that a human might have avoided.

If you are a passenger in an AI-driven car and you see an upcoming hazard but are powerless to prevent it, you will not be satisfied to know that in other locations at that same time there are self-driving cars avoiding accidents that you might not have been able to avoid. Said another way, if you are in the non-over lapping portion of the blue circle in the Venn diagram above, you are going to blame the AI for any injury or loss that occurs.

If there is an accident in the green overlapping section, you might still assume that you would have been able to avoid it since we all inflate our driving skills.

For these reasons and more, AI driving systems will be held to a near impossible driving safety standard by the public and the media. We already see this in the media today, whenever there is a crashing involving the likes of Waymo, Tesla, or Uber, the headlines make national news. The vehicles could have millions of crash-free miles, but they will be judged only by their failures. They could be performing 10X better than a human, but that is not the standard by which they will be judged.