Now that bike month is drawing to a close, it’s a great time to reflect on a few things that can be learned by riding our bikes more. In particular, what can cycling teach us about driving? It helps us learn two main things: how to drive more safely, and how to drive more efficiently. Cyclists must be the ultimate defensive drivers, and more frequent cycling can help us develop safer defensive driving habits. With respect to energy efficiency, the cyclist is his/her own power source, and so he or she is very aware of the energy requirements for different activities while riding. Recently I read through again the 100 tips for more efficient driving suggested by Ecomodder, and realized that many of these tips are learned naturally by riding a bike. Most cyclists tend to adjust their riding style to reduce their energy output; we get instant feedback on energy requirements, and have good motivation to minimize them. Here are some examples of things cyclists learn that transfer to efficient and safe driving of autos:
Momentum: It takes a lot of work to build up speed on a bike. Cyclists really appreciate their momentum. This gives you a sense of what might happen if you hit something with all that momentum, but it is also motivation to maintain your momentum. When you brake, all that kinetic energy is dissipated as heat from your brake pads, and then you have to redo all that hard work to get your momentum back up. When driving, you save energy by avoiding routes that require frequent starts and stops. This helps maintain your momentum. Alternate traffic control devices could also help. Replacing stop signs and traffic lights with yield (give way) signs and roundabouts helps drivers keep up their momentum, not to mention cutting down on wasteful idling and time lost sitting in traffic.
Gravitational Potential Energy: Pedaling up a hill can take a lot of work. It’s hard for a cyclist to let all that work go to waste by not maintaining speed developed by going back down the hill.
Anticipation: This is a key skill. We can tie together items 1 and 2 with the idea of anticipation. For example, if you are at the top of a hill, and there is a stoplight at the bottom, but you anticipate that it will turn red, then stop and wait at the top until the light turns (or time it so that you get to the light when it turns green) so that you can maintain your speed through the intersection. A cyclist also learns to keenly anticipate intentions of drivers as part of being a defensive rider. Cyclists learn how to look ahead, think ahead, and plan ahead. Drivers could benefit substantially from improved anticipation skill.
Small Profile: When you are riding fast or in windy conditions, the effect of air drag is very clear. Cyclists learn that crouching down and making yourself small cuts down significantly on drag force. Similarly, cars with a small profile, and fewer extra protrusions (like roof racks), have less drag. This can be especially important with cars since they generally travel much faster than cyclists. The power required to overcome drag force increases cubically with speed, that is, if you double your speed, it requires EIGHT times as much power to overcome drag force from air resistance.
Drafting: This is actually not so advisable for driving, but cyclists who have ridden in a pack understand the benefit of drafting. Basically, cyclists take turns in the lead position, and cyclists who follow behind benefit from lower air resistance. Average speed is noticeably higher when riding in a pack and drafting.
Good Tire Pressure: Anyone who has ridden with low tire pressure can attest that their bike is very sluggish compared to when their tires are fully inflated. It’s amazing to feel what a difference airing up your bike tires can make. It does make a difference with your car, but you don’t feel it the same as you do with a bike.
Well-tuned Drivetrain: A well-lubed chain and tuned shifters makes a bike a joy to ride. Otherwise it can be a struggle. Keeping your car in tune is also essential to efficient driving. Be sure to find out what the engineers who made your car recommend for maintenance, and stick to it. Back when I was an auto technician (clear back when there were a lot of carbureted cars still on the road), I found it very satisfying to take a poorly running car, tune it up, and see immediate big differences in how it drove, as well as big reductions in exhaust emissions.
Smooth Roads: Cyclists can sail over fresh, smooth roads so much more easily than rough terrain. Plowing through sand, mud, or snow takes a lot of extra effort. The same holds true for cars. Driving on dirt roads or through the snow burns more energy than driving on smooth asphalt.
Interaction and Courtesy: Cyclists are out in the open. Everyone can see our body language. We don’t have anything to hide behind, so it’s important to keep emotions in check. To be defensive riders, cyclists learn to interact and communicate with drivers as much as possible, to be sure each knows the other’s intention. Travelling in an interactive and courteous way can be much more pleasant (and safe) than driving in isolated bubbles.
The list above is far from comprehensive. Can you share with us things you have learned while cycling that helped you become a better driver?
By now most of you have probably heard about the Tesla Roadster, Fisker Karma, and other high performance electric cars that demonstrate we can make spectacular gains in energy efficiency AND enjoy amazing performance by designing cars in a new way. Improving efficiency and performance simultaneously is an impressive feat. These are competing objectives, that is, improving one objective normally involves degrading the other. We can design a car that is either high performance or highly efficient, but not both. We can visualize this kind of design tradeoff using a tradeoff curve usually called a Pareto curve or efficient frontier. The drawing below is a conceptual illustration of a Pareto curve in automotive design, showing the tradeoff between performance and efficiency.
We would like to maximize both performance (one aspect of performance is acceleration) and energy/fuel efficiency. Ideally we would like a design that is in the upper right corner of the plot above. Unfortunately, when a design tradeoff exists, this is not physically possible. We can’t focus on both performance and efficiency because they are competing objectives. If we focus on performance in vehicle design, we might end up with something like a Porsche 911 Turbo, which has a blistering fast 0-60 mph time as low as 3.2 seconds. Unfortunately this car doesn’t get great fuel economy. If we want to improve fuel economy we will need to sacrifice performance, that is, we will need to trade some performance for fuel efficiency (perhaps by reducing engine size, using smaller tires, reducing mass, etc.). If we focus on just fuel efficiency we might end up with something like a Geo Metro. The Pareto curve connecting these two points on the plot above represents what designs in between the Porsche and Geo are physically realizable. It’s not possible to create a vehicle to the upper right of the curve. Something on the interior of the curve is not Pareto optimal, meaning that it’s possible to improve both objectives simultaneously. Designs on the interior of this curve are to be avoided. Advanced design techniques, such as simulation and design optimization, can help engineers ensure that their designs are on the Pareto curve. It is up to the engineers and market analysts to determine where on the curve their product should be.
What if we changes the rules of vehicle design? What if instead of assuming powertrains had to include a conventional gasoline engine linked to a manual or automatic transmission, we allowed battery electric powertrains? The previously impenetrable Pareto curve shifts to the upper right if we can escape the inefficiencies of gasoline engines. New technology, and new ways of designing things, can push the Pareto curve to a new and better location, as shown in the diagram below. We can improve both performance and efficiency by introducing new technology. This is what’s going on with the Tesla and Fisker. The Aptera 2e places more emphasis on energy efficiency than performance, and solar cars are the ultimate in energy efficiency. The Prius uses a power split hybrid electric powertrain. It’s an improvement in efficiency over conventional powertrains, but it can’t compare in efficiency to pure electrics like the Aptera (that’s why it is a design on the interior of the Pareto curve). In fact, although my crude diagram doesn’t really depict this, the powerful Tesla gets better energy efficiency than the Prius.
The Tesla might be a fast EV, but have a look at the X1 Wrightspeed. It’s wicked fast. See where it’s positioned on the Pareto curve? The X1 is an Ariel Atom retrofitted with an all-electric powertrain created by AC Propulsion, makers of the eBox. Here is the X1 smoking both a Ferrari and a Porsche:
Now that’s what pushing out the Pareto curve looks like! Here is another race between the X1 and a Lamborghini, and then with a NASCAR racer:
The above analysis is admittedly simplified. The diagrams are conceptual and do not represent actual performance and efficiency numbers (if they did the solar car point would be way off to the right of your computer screen). In addition, there are many other competing objectives that need to be considered in vehicle design, such as range, safety, durability, utility, cost, and total lifecycle environmental impact. Nevertheless, Pareto curves are a helpful tool for visualizing and understanding design tradeoffs.
What emerging technologies do you think will expand the current Pareto curve for vehicle design (or other products)? Can you think of some additional tradeoffs important to vehicle design that I haven’t listed here? If we want to look at three, four, or more competing objectives, how do you think we can visualize the tradeoff relationships between them?
I usually write about better design of vehicles, renewable energy systems, or other engineered systems. We need to keep in mind the importance better design of other things. Here is a nice video I came across tonight that presents a vision for better urban design:
In engineering system design one must consider the interaction between all the subsystems. For example, in designing a car, the powertrain engineers need to work with the suspension designers to make sure the two systems work together well. Otherwise you could end up with great individual subsystems, but an unusable car. I view our plans for new transportation and energy systems in a similar way. There are a lot of interactions that we need to manage. Urban design is an issue that interconnects so many other aspects of life, and it deserves attention. We need to think about how our cities are laid out influences how people move, interact, and work. Better urban design and infrastructure could make transportation options viable that are not right now. For example, like cycling works in some situations right now (check out this bike move), but the right infrastructure (along with incentives, education, and availability of high-utility bicycles) could make it work for a large portion of our transportation needs.
Last week I had the opportunity to visit the MIT Solar Electric Vehicle Team. Several years ago I worked on a solar car as an undergraduate student, so it was a treat to glimpse the world of solar vehicle racing once again. One thing I have been impressed with about the solar racing community is its camaraderie, which has been an important element since the beginnings of solar racing. Existing teams are excited to see new ones start, and are typically very willing to share some insights into how to be successful in solar racing. The MIT team is planning to take this to a new level of transparency by becoming an open-source solar vehicle team. That is, their documentation and knowledge will be made open to everyone (although the software they use is not necessarily open-source).
While MIT has a very competitive team, education is a top priority for the group and takes precedence over race results. The team is composed of about 25 students, and is based in the MIT Edgerton Center, which is dedicated to hands-on learning experiences for undergraduate students. It’s not just the students designing and building the car who learn something, but sponsors, parents, peers, and the broader community as well. It’s fantastic to see what is possible when bright, creative engineers focus their efforts on energy efficiency. Solar race cars showcase what is possible, and help get us thinking about what we can do to improve current production vehicles. The current MIT solar car can maintain 55 mph on between 600 and 700 Watts of power. That is less than one horsepower! 700 Watts is less than what a hair dryer consumes, and much less than the power of a typical lawnmower. Why the focus on energy efficiency with solar cars? If a solar car is to drive continuously on solar power alone without depleting its batteries, it must use less power to drive than the power it can harvest from the sun. Solar power production is limited by the size of the solar array (which is limited by the size of the car), and the efficiency of the array. Here is a peek at the array on the MIT solar car:
The MIT array is made of monocrystalline silicon solar cells. Common photovoltaic (PV) cells are made from polycrystalline silicon. In these cells you can see lots of little crystals that make up each cell (the photo below is a polycrystalline PV cell). In the array above on the MIT car you can’t see any edges between crystals, because each cell is a single crystal. This makes the cells more efficient. They are also a little bit flexible so they can conform to the curves on the car. The MIT cells are 21% efficient, which is pretty amazing for silicon cells. This means that 21% of the sunlight energy hitting each cell is converted into electrical energy. Satellite-grade PV cells are made from different materials (like gallium arsenide), and can reach efficiencies as high as 40%, but are much more expensive than terrestrial grade silicon PV cells. Click here to learn more about how PV cells work.
The MIT car uses a lithium ion battery pack that is about the size of four regular car batteries. It is made of a large number of laptop batteries wired together with a power management system to keep things under control. Some teams use lithium polymer batteries because of their better power density (i.e., for the same size battery, lithium polymer batteries can output a lot of power), but these batteries have lower energy density than lithium ion batteries. To summarize, if you are comparing a lithium ion battery and a lithum polymer battery that are the same size, lithium ion can hold more energy, but lithium polymer can release its energy faster. The MIT team examined this tradeoff, and learned that for their car and the races they were competing in, lithium ion was the best choice. Tradeoffs like this can be analyzed using the modeling and optimization techniques that I’m addressing in articles throughout this blog. Using quantitative tools like these can help engineers explore design options and make the best choices for their design problems.
In upcoming posts I will describe some of the ways solar car designers squeeze every last bit of energy efficiency out of their cars, and discuss how lessons learned from solar racing can aid advancements in vehicle design for the rest of us.
What do you think about the MIT team’s open development approach, or solar vehicle racing in general?
The following is the second installment by Greg Kushmerek, a Design Impact guest blogger writing about cycling as a viable and sustainable form of transportation. Greg’s last post is available here.
What would it take to get Americans to adopt more cycling in their daily lives?
Perhaps a better question is: what prevents people from using the bike as a common mode of transportation?
Well, there’s a lot. Some people like to jump right into the societal norms discussion: it’s not cool, people look funny, Americans prefer comfortable vehicles with large carrying capacity. My response is that societal norms evolve and arguing from the point of view strictly over what people will accept isn’t a useful place to be. Don’t get me wrong: if you were coming to me with a business case that required some of my own cash, I’d be very mindful about those societal norms in determining whether the current market supported the expected cash flows.
So what prevents people from getting on the bike? As I mentioned previously, infrastructure is a big part of it and I argue that urban planning has a lot to do with it too. Someone who wants to ride a bike as a means to transportation is more motivated to ride on busy roads — they’re busy because they’re direct and go to useful places. These roads frequently
Do not have clear places for cyclists to be.
Do not tell cyclists when to wait their turns.
Do not have places to keep their bikes at the destinations.
Instead, a cyclist is expected to know the rules of the road, and an automobile driver is expected to know a cyclists rights. It often doesn’t work out. Last week, a woman who was angry that I went ahead on my green light and forced her to stop before she could make her left turn yelled at me “YOU ARE NOT A CAR!!” If I was a car, presumably she’d have given me the legal right of way as required as she made her left turn. Bikes, in her eyes, don’t have a right to be on the road regardless of what the law says.
Are bike lanes the answer? Certainly that’s part of it but only so long, in my opinion, that the bike lanes are consistent in traffic wherever there are roads. They also can’t be placed as they are so often done in the USA: set up so close to a parking lane that cyclists are inadvertently doored as someone pushes a car door open in front of an approaching cyclist. Cyclists need signage showing them where they are expected to be and when they are expected to truly stop. You can’t ignore the need for enforcement either: nothing would make me happier than seeing more police ticketing cyclists who don’t obey traffic laws (so long as they also ticket drivers who don’t respect a cyclist’s right too).
The last key is the place to put your bike when you arrive. Looking again at The Netherlands, you see civic bike stands everywhere. Just as you can drive somewhere in the USA and find on-street parking set up and maintained by the government, in The Netherlands you have bike stands all over the place: in front of stores, movie theaters, train stations, parks, schools, government buildings. In the USA, you’ll get some attempts to provide a place to lock up a bike, but they’re few and far between. Maybe the government shoudn’t invest in something that few people use right now, but if the government doesn’t invest at all, that becomes a self-fulfilling prophecy.
Government investment, a.k.a. urban/civic planning, is why I think you can ignore the societal norms argument. Look in places like Cambridge, MA, or Seattle, WA, and you’ll find lots of examples where the government has invested in cycling as a transportation option and you see more people doing it.
Government investment, of course, is a hard sell for many. Many people confuse government investment with business investment and think that the exact same rules apply. I disagree. The government often invests where we don’t expect to have a market in order to keep society livable. Otherwise, we might as well go to the Libertarian model and expect a profit-based market solution for all services: Fire, Police, roads, water, sewage, trash disposal, and so on. Yet we are where we are partly because the goverment invested in a high-speed, high-car capacity road system that lets people travel very far between work and home.
Where do we go next? What do you want the goverment to invest in for a sustainable environment?
Last year I read a book by Carl Honoré, In Praise of Slowness. In essence, Honoré advocates living a little more deliberately and less frenetically: doing (and enjoying) a few things well instead of obsessing over speed and quantity. Consider how life would be different if society was concerned more about Gross National Happiness than Gross National Product. Honoré provides insights into how to experience more depth in life and focus on things of greatest importance. He describes how Slow philosophy can be applied to a range of areas, including food, work, play, and raising children. I would like to suggest that Slow be extended to another area: design.
In proposing Slow Design, I’m not suggesting that we increase the time it takes to get products to market, but perhaps we can apply elements of the Slow philosophy and focus our creative efforts on issues of lasting value. We need to be working on the right things in the right way, and create more overall value. Slow Design engenders a new cultural perspective on design, more thoughtful consumption, and a shift in priorities.
Think of all the creative effort and resources devoted to developing products of convenience; items that make our lives just a little easier (or appear to make them easier, but actually make them more complicated). What is the real impact of all this effort? Is it genuine progress? Does it raise the standard of living for many people? It certainly generates profit for some, and employs manufacturing workers around the world. Perhaps this phenomenon is a natural result of a market (until recently) full of consumers eager to spend. But what about now? What should we shift out design efforts toward? The present is an ideal time to reflect and reprioritize.
Let’s focus on living with a purpose greater than consumption. Let’s pour our creativity into things of value, things of beauty that really enhance our lives, even improve the way we live. How much variety in injection-molded plastic do we really need? Our design priorities must include clean energy systems, better transportation, common sense agriculture systems, and cradle-to-cradle design, not consumer junk. So much of our creative capacity is wasted on wares worth so little.
What do you think of Slow Design? What past and present design priorities have been a hindrance? What do you think we should focus design efforts on, and how else might Slow philosphy enhance design?
One month has passed since Earth day 2009 (today is Design Impact’s one month anniversary). Many of us participated and made some changes on April 22nd. You may have been asked last month what you did to celebrate Earth Day. A better question might be to ask now what have you done since Earth Day. Have any of your changes stuck? You probably have heard some say that ‘every day should be earth day’, that sustainability should become a built-in way of life for each of us. Some even go so far as to say we should throw out Earth Day, which has become a ‘feel good token’. I’m not sure we should eliminate Earth Day, but after 40 years we need to move on to something that fosters bigger impact and faster progress. Our efforts should be continuous; perhaps Earth Day could become our date for annual review.
We need a more focused approach that goes beyond green choices one day per year, or even green daily choices year-round. We need to get familiar with the numbers that help us quantify and compare the impact our decisions make, and focus our efforts on things that will provide the most impact, particularly over the long term. As we learn more, it becomes clear that good individual choices can make a difference, but will not bring the large-scale change we need for our energy and agriculture systems. So instead of focusing all of our green efforts on whether we have unplugged our phone charger, or if we should skip beef for a day, let’s do as Joe Romm of Climate Progress advocates and ‘get political’. Let’s awaken the full power and creativity of our society and direct it toward changes that will lead to a sustainable future.
Perhaps the something we need is an ‘Earth Decade’. Have a look at the WE Campaign, which has issued a challenge to the U.S. to ‘commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years’. This is the kind of vision and plan we need—one that is on the the scale of other grand mobilizations or transitions (think WWII and the space race). In the words of Al Gore:
“our dangerous over-reliance on carbon-based fuels is at the core of all three of these challenges - the economic, environmental and national security crises. We’re borrowing money from China to buy oil from the Persian Gulf to burn it in ways that destroy the planet. … If we grab hold of that common thread and pull it hard, all of these complex problems begin to unravel and we will find that we’re holding the answer to all of them right in our hand. The answer is to end our reliance on carbon-based fuels. In my search for genuinely effective answers to the climate crisis, I have held a series of “solutions summits” with engineers, scientists, and CEOs. In those discussions, one thing has become abundantly clear: when you connect the dots, it turns out that the real solutions to the climate crisis are the very same measures needed to renew our economy and escape the trap of ever-rising energy prices. Moreover, they are also the very same solutions we need to guarantee our national security without having to go to war in the Persian Gulf.”
I believe we can solve this. Let’s declare an Earth Decade. Let’s unify and get moving.
Last week I wrote a post about cars powered by compressed air. I was fairly critical of the claims made by MDI, one company developing an air-powered car. Don’t get me wrong; it’s not the technology or innovative efforts that bother me. I think the idea of an air-powered car is pretty cool. Some of the claims made by MDI, on the other hand, do get me a little fired up. I watched the MDI video that I included in my last air car post again, and I am astounded at what it contains. First, MDI neglects (initially) the cost of compressing air and glosses over the energy loss of a compressed air system, but more importantly, they propose a ‘perpetual motion’ system for their car. I called this a red flag earlier. I want to explain why perpetual motion claims are a red flag. This drawing illustrates what they are talking about at about the 2:45 point in the video:
MDI suggests that they should use a compressed-air powered electric generator to power an electric air compressor to refill the air tank. They claim such a car will refuel itself and result in perpetual motion (perpetual motion violates the laws of physics). What do they think this system is going to accomplish? At every stage in the process energy is lost. Electric generators are not 100% efficient; energy is lost to heat and electromagnetic radiation. Air compressors put off a lot of heat, so again there is more energy loss. This system will recharge the air tank with far less compressed air than was used to compress it. The only purpose a system like this serves is to create waste heat! It will not extend the range of an air car, it will reduce it. It will increase overall energy consumption. Whoever proposed this does not understand basic thermodynamics. Does MDI not have any engineers on staff?
This reminds me of an April Fools post on Autobloggreen that describes a car that uses a miniature wind turbine to power the headlights. This is similarly impractical idea since the energy to turn the wind turbine comes indirectly from the engine that moves the car. Because wind turbines are not 100% efficient, this system would result in worse fuel economy, not better. At least the post about the wind turbine car was a satirical April Fools article, in contrast to MDI’s video.
I aim to keep most of my writing positive, but claims like this really need to be addressed and exposed for what they are. Either MDI really doesn’t know what it’s doing, or they intentionally are using a deceptive marketing approach.
I do want to point out that there are some cases where air-powered cars make a lot of sense. There is no local pollution with these powertrains, and the technology is very simple (and low cost). The video below describes another vehicle intended for use indoors, where zero pollution is important. Air cars on factory or warehouse floors may be an especially practical alternative since many of these buildings already have compressed air infrastructure.
The rotory air motor here is a more sophisticated design. It has smoother, more efficient operation than a reciprocating piston motor, like the one used by MDI. Keep in mind, however, that using compressed air to power a car involves a lot of energy loss. When the air is compressed to fill the tank, the air gets hot. This waste heat is lost energy, and is significant. Battery electric vehicles are a better alternative in terms of energy efficiency, but would likely cost more than air cars.
What do you think about air cars? Where else might they be practical transportation alternatives?
