I haven't posted here in a while because it seems like nobody is paying attention. I checked the counter today and noticed this blog is starting to show up on Google search in the top 10 of 37,000 for several searches and it is starting to get some good web traffic. Not bad!
I always chart my fuel economy in my car. For every tank of gas I record the amount of fuel used, cost of the fuel, approximate outdoor temperature, the miles driven, miles with the air conditioner on, highway miles, interstate miles, city miles, the weight I am carrying, and any other significant notes. I have a big Excel sheet with all of this information and I do many calculations with the data.
Last weekend I drove about 420 miles round trip to visit family and achieved my highest fuel economy ever: 46 mpg! The car is a Toyota Corolla S with manual transmission. It is rated with the old mpg rating system to have 32 city/41 highway mpg. The awesome thing about the high fuel economy is about 40% of the miles were on the interstate at higher speeds, and 70% of the miles required the air conditioner.
My lifetime average fuel economy with the car is about 36 mpg. Most of the miles I have driven between 3 and 5 mph over the speed limit. This past weekend was different, I never exceeded the speed limit on highways or the interstate.
The benefits of going slow was high fuel economy. The downside was mostly psychological. Driving 55 seemed like I was going very slow and I could be going faster. In reality, the difference was minimal. Driving just a few mph faster does very little for short trips, but for long trips a few mph can easily add up. I actually found the extra time required was negligible. It took me 3h 45min to make the drive one way at the posted speed. My previous trip was 5 mph over the speed limit for most of the time and it took me 3h 35min. I saved 10 minutes, but my fuel economy was about 8 mpg less.
In addition to driving slow, I do use mild hypermiling techniques that I have used regularly over the past several years. The main thing to do is just pay attention to driving, which you should be doing anyway. If you see a stop sign ahead, don't hold the gas pedal down until the last moment and then brake hard. You would be surprised how far your car can coast. For one highway stop sign on the route, I put my car in neutral 0.6 miles away from the sign and coasted in. When I hit my brakes as I neared the stop sign, my car was still doing 45 mph and had only dropped 10 mph from my previous speed. If there is a slight downhill grade, I can put the car in neutral even sooner. The extra time this added to my trip was very small, probably less than 5 seconds, but I was able to coast for 0.6 miles at probably 200 mpg or higher.
A similar technique can be used for stoplights. If one turns red, brake early to slow down, and then coast in. If you time it right, you will still be rolling and nearing the car in front of you as the light turns green. Slowing early will actually help you maintain a higher speed when the light turns green.
Two other things I do are slow acceleration and using my cruise control. These are simple things that will save you several mpg. I would not recommend drafting other vehicles as some others suggest. Drafting is unsafe and illegal.
The biggest time lost in the trip is not from the highway driving speed; city driving is the worst. As I travel through small towns, it is only 4% of the total trip miles but it takes 10% of the trip time. Doing the math, it only saves 12 minutes over the whole trip to drive 4 mph over the speed limit, which agrees with my observed results.
Changing interstate speeds back to 55 mph might not be such a bad idea. Even if people still go over the speed limit, the net effect will be lower overall speed and people using less fuel. For my 210 mile trip, the difference in time between current speed limits and if all roads were 55 mph is about 25 minutes. The benefits of increased safety and reduced foreign dependence on fuel are probably worth the extra time.
Wednesday, July 2, 2008
Sunday, March 16, 2008
26 vs 29er Mountain Bikes - an Engineering Analysis
When I was researching bikes last fall I ultimately settled on a 29er, which refers to the tire size. Instead of a traditional 26 inch wheel, a 29er has a 29 inch wheel. The idea is lower rolling resistance, better traction, and a ton of other benefits. The bigger wheels seem to be the trend of the future with mountain bikes.
There is a lot of differing opinions on the internet about the tire size, ranging from people hating 29ers to people who never ride a 26 inch wheel bike after changing. The one big argument against larger wheels is slower acceleration and heavier weight. The wheels weigh more due to the bigger size and more material, and with the larger diameter and resulting higher moment of inertia, it will take more energy to spin a 29er wheel up to speed. My initial reaction was the effect is probably minimal, but I never got around to calculating the difference until today.
The following is a comparison of energy required for acceleration of a 26 vs 29er bike based on calculations only. For the analysis, specifications from manufacturers are used. Both bikes will use Bontrager Rythm Elite Tubeless Disc wheels at 1,835g and 1,955g for the smaller and larger size respectively. Bontrager Jones ACX Aramid Clincher 2.2 width tires are used, with a weight of 520g and 650g respectively. Tubes are assumed to weigh 200g for each size tire. I am assuming the wheel has of its weight at the ISO bead seat diameter of 559 and 622 mm for the two different wheel sizes. This is not completely accurate, but I am not going to mathematically integrate the individual wheel parts to account for density gradients and variable geometry. The moment of inertia calculation should be within 10% using my approximation, and the comparison between the two bikes should be nearly identical with less than one percent error based on using the same assumption for both.
The wheels are on a bike frame that weighs 8,000g for both tire sizes. The total weight of the wheels with tubes and tires is 3,275 and 3,655 for the 26 inch and 29 inch wheels respectively. The total bike weight is therefore 11,275g (24.8 lbs) and 11,655g (25.6 lbs) with the bigger wheel bike being heavier. The moment of inertia of the wheels is 0.256 and 0.354 kg-meters squared. The small change in diameter is squared, which makes the seemingly small change in diameter have a large affect on the moment of inertia.
Now for the results. Lets assume both bikes start from a stop and accelerate to 8 meters per second (17.9 mph) on flat ground. The calculation is only for energy to bring the bike up to speed, and does not consider rolling resistance or other losses. It will take 436 Joules to bring the bike up to speed for the 26" wheels versus 457 Joules for the 29" wheels for an increase of about 4.9%. 29ers are claimed to have decreased rolling resistance. Assuming both tires have the same coefficient of rolling friction since they are using the same tire, the 29er should have a 10% lower rolling resistance due to the larger wheel diameter, which more than makes up for the losses due to weight and tire diameter.
This analysis isn't quite complete. In the calculation, a common error was made as I ignored the weight of the rider. Bicyclists, bicycle magazines, and other sources always talk about bike weight without including the rider effect on the performance. If one bike weighs 24 lbs and another weighs 25 lbs, the simple calculation would be one bike is 4% lighter than the other. If you include a 175 lb rider, the difference in weight of the complete bike and rider together is only 0.5%. Only considering bicycle weight exaggerates the performance enhancement.
If I recalculate the results again assuming a 155 lb rider (me) the difference is even smaller than before. The total energy required to bring the bike and rider to 8 meters per second velocity is 2,690 Joules for the 26" bike versus 2,711 Joules for a 29er bike, or about 0.8%. The rolling friction difference is for the most part not affected by rider weight. There will still be a 10% benefit of lower rolling resistance with the bigger wheels, therefore the losses from a heavier and larger diameter wheeled bike should be completely outweighed by lower rolling resistance.
If you are going to drag race the two bikes in real life, the 29er should win if both riders weigh the same, have the same energy output, and both bikes are built from similar quality components. The difference between the two is very small. The weight argument is certainly not valid.
NOTE: The calculations above do include the effect of rotating mass, which is the reason why I had to calculate the moment of inertia of the wheels. The larger diameter wheels spin slower, so the amount of energy required to spin the wheels only up to speed is only about 12% different. The amount of energy required to accelerate the wheels up to rotational speed is only about 17% of the total energy to accelerate the whole bike (ignoring rider). The majority of the energy to accelerate the bike is due to bike mass.
UPDATE 3/23/08: In response to a comment, I was asked to recalculate the numbers based on slightly heavier tubes for the 29er. A 29er wheel is about 11% bigger in circumference, so I am going to calculate the tube to have an 11% higher mass, or 222g versus 200g for the 26er. The results change by 2 Joules, or 459 Joules to accelerate the bike and wheels up to speed, or about 5.4% more than a 26er (versus 4.9% with the same mass tubes analysis). The rider and bike combined will require 0.87% more energy to accelerate than a 26er with the heavier tubes, with a roughly 10% lower rolling resistance.
There is a lot of differing opinions on the internet about the tire size, ranging from people hating 29ers to people who never ride a 26 inch wheel bike after changing. The one big argument against larger wheels is slower acceleration and heavier weight. The wheels weigh more due to the bigger size and more material, and with the larger diameter and resulting higher moment of inertia, it will take more energy to spin a 29er wheel up to speed. My initial reaction was the effect is probably minimal, but I never got around to calculating the difference until today.
The following is a comparison of energy required for acceleration of a 26 vs 29er bike based on calculations only. For the analysis, specifications from manufacturers are used. Both bikes will use Bontrager Rythm Elite Tubeless Disc wheels at 1,835g and 1,955g for the smaller and larger size respectively. Bontrager Jones ACX Aramid Clincher 2.2 width tires are used, with a weight of 520g and 650g respectively. Tubes are assumed to weigh 200g for each size tire. I am assuming the wheel has of its weight at the ISO bead seat diameter of 559 and 622 mm for the two different wheel sizes. This is not completely accurate, but I am not going to mathematically integrate the individual wheel parts to account for density gradients and variable geometry. The moment of inertia calculation should be within 10% using my approximation, and the comparison between the two bikes should be nearly identical with less than one percent error based on using the same assumption for both.
The wheels are on a bike frame that weighs 8,000g for both tire sizes. The total weight of the wheels with tubes and tires is 3,275 and 3,655 for the 26 inch and 29 inch wheels respectively. The total bike weight is therefore 11,275g (24.8 lbs) and 11,655g (25.6 lbs) with the bigger wheel bike being heavier. The moment of inertia of the wheels is 0.256 and 0.354 kg-meters squared. The small change in diameter is squared, which makes the seemingly small change in diameter have a large affect on the moment of inertia.
Now for the results. Lets assume both bikes start from a stop and accelerate to 8 meters per second (17.9 mph) on flat ground. The calculation is only for energy to bring the bike up to speed, and does not consider rolling resistance or other losses. It will take 436 Joules to bring the bike up to speed for the 26" wheels versus 457 Joules for the 29" wheels for an increase of about 4.9%. 29ers are claimed to have decreased rolling resistance. Assuming both tires have the same coefficient of rolling friction since they are using the same tire, the 29er should have a 10% lower rolling resistance due to the larger wheel diameter, which more than makes up for the losses due to weight and tire diameter.
This analysis isn't quite complete. In the calculation, a common error was made as I ignored the weight of the rider. Bicyclists, bicycle magazines, and other sources always talk about bike weight without including the rider effect on the performance. If one bike weighs 24 lbs and another weighs 25 lbs, the simple calculation would be one bike is 4% lighter than the other. If you include a 175 lb rider, the difference in weight of the complete bike and rider together is only 0.5%. Only considering bicycle weight exaggerates the performance enhancement.
If I recalculate the results again assuming a 155 lb rider (me) the difference is even smaller than before. The total energy required to bring the bike and rider to 8 meters per second velocity is 2,690 Joules for the 26" bike versus 2,711 Joules for a 29er bike, or about 0.8%. The rolling friction difference is for the most part not affected by rider weight. There will still be a 10% benefit of lower rolling resistance with the bigger wheels, therefore the losses from a heavier and larger diameter wheeled bike should be completely outweighed by lower rolling resistance.
If you are going to drag race the two bikes in real life, the 29er should win if both riders weigh the same, have the same energy output, and both bikes are built from similar quality components. The difference between the two is very small. The weight argument is certainly not valid.
NOTE: The calculations above do include the effect of rotating mass, which is the reason why I had to calculate the moment of inertia of the wheels. The larger diameter wheels spin slower, so the amount of energy required to spin the wheels only up to speed is only about 12% different. The amount of energy required to accelerate the wheels up to rotational speed is only about 17% of the total energy to accelerate the whole bike (ignoring rider). The majority of the energy to accelerate the bike is due to bike mass.
UPDATE 3/23/08: In response to a comment, I was asked to recalculate the numbers based on slightly heavier tubes for the 29er. A 29er wheel is about 11% bigger in circumference, so I am going to calculate the tube to have an 11% higher mass, or 222g versus 200g for the 26er. The results change by 2 Joules, or 459 Joules to accelerate the bike and wheels up to speed, or about 5.4% more than a 26er (versus 4.9% with the same mass tubes analysis). The rider and bike combined will require 0.87% more energy to accelerate than a 26er with the heavier tubes, with a roughly 10% lower rolling resistance.
Wednesday, March 5, 2008
The GT Lives!
Tonight I attended a bicycle maintenance class put on by the outdoor recreation program at Iowa State. The class was definitely worth it. For two hours, we talked about bikes and worked on our own. I already knew most of the topics we covered, and every adjustment talked about in the class I had already done to one of my bikes at some point, but it was good to learn a few new techniques.
We were told to bring our bikes to work on in the class. I brought the old mountain bike, a GT hardtail. My GT now works better than ever. I adjusted the derailleur so it shifts perfectly. I even did a little bit of truing of the rear wheel and some general cleaning.
I can now adjust a rear derailleur in about 1/3 the time it took me before, and with better results. Not bad, considering the class only cost $3.00!
We were told to bring our bikes to work on in the class. I brought the old mountain bike, a GT hardtail. My GT now works better than ever. I adjusted the derailleur so it shifts perfectly. I even did a little bit of truing of the rear wheel and some general cleaning.
I can now adjust a rear derailleur in about 1/3 the time it took me before, and with better results. Not bad, considering the class only cost $3.00!
Tuesday, February 26, 2008
First Ride
Snow has been on the ground here in Ames since the end of November, which is now about three months ago. We repeatedly get snowstorms and sub zero Fahrenheit weather resulting in very little snow melting. The roads have been a mess; they will still have a layer of ice and snow several days after the most recent snowstorm.
Finally, last weekend, we had a period of about a day where the sun cleared the roads and the ice and snow was gone. Of course, this didn't last long as another snowstorm arrived Monday with a slushy mix of three inches of snow. The latest snow left another layer of ice covering sidewalks, bike trails, and streets.
During the brief moment without ice on the roads, I took the new road bike out on the road. The bike is a Trek 1600 SLR. It has an aluminum frame, carbon fiber fork and seatpost, and Shimano 105 and Ultegra components with a 30 speed setup. I'm very impressed with its performance and ride. Power is transfered to the ground very efficiently. I was cruising between 22 and 27 mph while on flat or slightly uphill road. I'm excited to see the performance when I'm not sick and we have good weather (it was 15 degrees when I was riding).
The controls are awesome. New road bikes have shifters built into the brake levers requiring a simple sideways movement of one or two fingers for an indexed shift. Shifting is instant and precise. I added a Cateye Cadence cycle computer, which provides basic speedometer, odometer, and timing functions, and it also displays my cadence (pedaling rpm).
The bike weighs around 20 lbs, which is not super light for a race bike but within a few pounds of the lowest weight bikes available. The cost of removing a few more pounds of weight is spending about four times as much on a carbon fiber frame and other lighter components. Aluminum is fine with me. I'm not ready for carbon fiber due to cost and durability issues.
I will add more details once I get more miles on the bike.
Finally, last weekend, we had a period of about a day where the sun cleared the roads and the ice and snow was gone. Of course, this didn't last long as another snowstorm arrived Monday with a slushy mix of three inches of snow. The latest snow left another layer of ice covering sidewalks, bike trails, and streets.
During the brief moment without ice on the roads, I took the new road bike out on the road. The bike is a Trek 1600 SLR. It has an aluminum frame, carbon fiber fork and seatpost, and Shimano 105 and Ultegra components with a 30 speed setup. I'm very impressed with its performance and ride. Power is transfered to the ground very efficiently. I was cruising between 22 and 27 mph while on flat or slightly uphill road. I'm excited to see the performance when I'm not sick and we have good weather (it was 15 degrees when I was riding).
The controls are awesome. New road bikes have shifters built into the brake levers requiring a simple sideways movement of one or two fingers for an indexed shift. Shifting is instant and precise. I added a Cateye Cadence cycle computer, which provides basic speedometer, odometer, and timing functions, and it also displays my cadence (pedaling rpm).
The bike weighs around 20 lbs, which is not super light for a race bike but within a few pounds of the lowest weight bikes available. The cost of removing a few more pounds of weight is spending about four times as much on a carbon fiber frame and other lighter components. Aluminum is fine with me. I'm not ready for carbon fiber due to cost and durability issues.
I will add more details once I get more miles on the bike.
Thursday, February 21, 2008
Kiteboarding
I haven't posted here for a while again. I've been busy with a lot of work for my research project. I know all about coal gasification, ethanol land use, problems with ethanol, new solar projects, and other good stuff. I should have a paper done mid March.
I've also been going to the gym a lot this semester. I have been there about twice a week riding a stationary bike in a cycling class. I can really tell the difference in my performance. Just this week I noticed I can ride at a very high output for long periods of time. I wish they had power meters on the bikes so I could see my watt output, and how I've improved. This week I also started doing some weight lifting after the hour bike rides. I should be in very good shape by the time spring arrives (will it this year?).
Last fall I purchased a big 4 meter traction kite, which is basically a big powerful kite designed for a large amount of pull on the lines. I bought it for fun and exercise, and it meets my goal of entertainment requiring little or no fossil fuel. It looks like a parachute and is designed similarly. I measured its air speed with a video camera and the kite reaches speeds in excess of 100 mph during 18 mph wind gusts! The kite has the power to lift me off the ground in higher winds, and it easily drags me through grass even with slow 12-15 mph wind conditions. One day I was practicing "kitejumping" and I was lifted about 4 feet off the ground and thrown about 40 feet forward! It is a huge adrenaline rush to be thrown through the air!
I finally decided to take advantage of the constant winter precipitation known as snow and bought a snowboard about two weeks ago. I bought it (or pretty much stole it based on the price) used from a guy here at the University. Most people would go to a ski hill to test it out, but I had different plans.
My new winter sport is kiteboarding. It consists of using my kite to drag me on a snowboard. I start by setting up the traction kite in an open area and then do a test flight to evaluate the wind conditions. Then I land the kite and attach the brake lines to a rope attached to a post or fence. I normally use a 12" steel spike stabbed into the ground, but that doesn't work good this time of year. I then strap into the snowboard and attach the kite killers to my wrists (they provide somewhat of a safety by pulling the brake lines on the kite if I lose control). I unhook the rope from the brake lines, tilt the handles back, and the kite launches into the sky.
This is where it gets interesting. The kite requires a lot of practice to fly. There are four lines and two handles. Each handle has two lines attached. The main lines provide the pull, and the other two are the brake lines. You can do simple maneuvers by changing the relative line length between the left and right side of the kite, but you really need to know how to apply the brakes to partially depower the kite in high winds and to provide power assisted cornering using just one brake line to make the kite turn very sharp. Besides all the control, which requires constant arm movement for steering along with wrist movement to control brakes, you have to be aware of the power window. The kite has to fly downwind of you, and it provides the most power about 10 meters off the ground directly downwind. There are parabolic shapes of wind power, depending on how far to the side you are away from directly downwind and the height above the ground. In simple terms, it will rip your arms out when downwind, and it flies like a little plastic kite with hardly any pull when directly overhead or far to the side.
I've used the kite quite a bit, so I have most of the understanding of the wind and control figured out. Now add a snowboard. I have done some downhill skiing, so I am familiar with sliding on snow. Snowboards are different, and my past experiences have all involved a small kid-sized plastic board I used last year. The kid design was rated for about 50 lbs, and I have only gone down tiny sledding hills with it. Basically, I have no snowboarding experience. I figured being dragged by a kite will be a perfect time to learn.
It's not.
The wind has thrown most of the snow off of the field I fly at. I am left with an inch or two of powder with ice underneath. Snowboards don't grip wind swept ice at all, and I need the snowboard to grip so I can change direction and get going fast. I don't want to travel with the wind, or else I will end up a few hundred feet away from where I started and I won't be able to get back. Speed is also limited going downwind due to a decrease in relative wind speed as I go faster. The best way travel is across the wind, that way you can accelerate to speeds several times the wind speed.
Trying to control a snowboard without falling over while turning and maneuvering with no prior snowboarding experience is a big challenge. Now add in the fact that I am attached to a kite, with both of my hands busy. I am trying to pay attention to where I am going on the snowboard while controlling the kite to be at the right spot in the wind window to give me the amount of power I want pulling me in the correct direction. Throw a gust of wind at me and I accelerate really fast, and suddenly pay attention to the snowboard and lose track of the kite, and then the kite swings back to the center of the power window and tries to drag in a direction I don't want to go and knocks me over in the process. I can't use my hands for balance, and I have to use the snowboard to resist my movements. When the wind is strong or a gust hits the kite, it tries to pull me over forward and knock me down, so I have to lean back. While I'm leaning back, the wind will die and I will fall over backwards.
As you have probably figured out by now, there are a ton of things to pay attention to at a single time. I need more practice, but it is definitely fun. I have gone out three times now. The first time I only went a few hundred feet due to poor wind conditions (either barely blowing or gusts approaching 25 mph lifting me off the ground). The other time the wind was marginal but the snow was good, and I was able to travel at least 1000 meters across the snow. The last time the wind was somewhat gusty, and all the snow had blown off the field. I traveled probably 500 meters before the kite knocked me over knee first onto a patch of ice and I quit for the day.
What may be surprising to those of you reading this from the warmth of indoors is that kiteboarding in 30 below wind chill is not cold at all. I use about every muscle in my body when kiteboarding and I end up overheating and unzipping my coat after a short amount of time. Controlling the kite and snowboard works some weird muscles and I feel it the next day.
Maybe this weekend we will have a good combination of wind and snow and I will try again.
I've also been going to the gym a lot this semester. I have been there about twice a week riding a stationary bike in a cycling class. I can really tell the difference in my performance. Just this week I noticed I can ride at a very high output for long periods of time. I wish they had power meters on the bikes so I could see my watt output, and how I've improved. This week I also started doing some weight lifting after the hour bike rides. I should be in very good shape by the time spring arrives (will it this year?).
Last fall I purchased a big 4 meter traction kite, which is basically a big powerful kite designed for a large amount of pull on the lines. I bought it for fun and exercise, and it meets my goal of entertainment requiring little or no fossil fuel. It looks like a parachute and is designed similarly. I measured its air speed with a video camera and the kite reaches speeds in excess of 100 mph during 18 mph wind gusts! The kite has the power to lift me off the ground in higher winds, and it easily drags me through grass even with slow 12-15 mph wind conditions. One day I was practicing "kitejumping" and I was lifted about 4 feet off the ground and thrown about 40 feet forward! It is a huge adrenaline rush to be thrown through the air!
I finally decided to take advantage of the constant winter precipitation known as snow and bought a snowboard about two weeks ago. I bought it (or pretty much stole it based on the price) used from a guy here at the University. Most people would go to a ski hill to test it out, but I had different plans.
My new winter sport is kiteboarding. It consists of using my kite to drag me on a snowboard. I start by setting up the traction kite in an open area and then do a test flight to evaluate the wind conditions. Then I land the kite and attach the brake lines to a rope attached to a post or fence. I normally use a 12" steel spike stabbed into the ground, but that doesn't work good this time of year. I then strap into the snowboard and attach the kite killers to my wrists (they provide somewhat of a safety by pulling the brake lines on the kite if I lose control). I unhook the rope from the brake lines, tilt the handles back, and the kite launches into the sky.
This is where it gets interesting. The kite requires a lot of practice to fly. There are four lines and two handles. Each handle has two lines attached. The main lines provide the pull, and the other two are the brake lines. You can do simple maneuvers by changing the relative line length between the left and right side of the kite, but you really need to know how to apply the brakes to partially depower the kite in high winds and to provide power assisted cornering using just one brake line to make the kite turn very sharp. Besides all the control, which requires constant arm movement for steering along with wrist movement to control brakes, you have to be aware of the power window. The kite has to fly downwind of you, and it provides the most power about 10 meters off the ground directly downwind. There are parabolic shapes of wind power, depending on how far to the side you are away from directly downwind and the height above the ground. In simple terms, it will rip your arms out when downwind, and it flies like a little plastic kite with hardly any pull when directly overhead or far to the side.
I've used the kite quite a bit, so I have most of the understanding of the wind and control figured out. Now add a snowboard. I have done some downhill skiing, so I am familiar with sliding on snow. Snowboards are different, and my past experiences have all involved a small kid-sized plastic board I used last year. The kid design was rated for about 50 lbs, and I have only gone down tiny sledding hills with it. Basically, I have no snowboarding experience. I figured being dragged by a kite will be a perfect time to learn.
It's not.
The wind has thrown most of the snow off of the field I fly at. I am left with an inch or two of powder with ice underneath. Snowboards don't grip wind swept ice at all, and I need the snowboard to grip so I can change direction and get going fast. I don't want to travel with the wind, or else I will end up a few hundred feet away from where I started and I won't be able to get back. Speed is also limited going downwind due to a decrease in relative wind speed as I go faster. The best way travel is across the wind, that way you can accelerate to speeds several times the wind speed.
Trying to control a snowboard without falling over while turning and maneuvering with no prior snowboarding experience is a big challenge. Now add in the fact that I am attached to a kite, with both of my hands busy. I am trying to pay attention to where I am going on the snowboard while controlling the kite to be at the right spot in the wind window to give me the amount of power I want pulling me in the correct direction. Throw a gust of wind at me and I accelerate really fast, and suddenly pay attention to the snowboard and lose track of the kite, and then the kite swings back to the center of the power window and tries to drag in a direction I don't want to go and knocks me over in the process. I can't use my hands for balance, and I have to use the snowboard to resist my movements. When the wind is strong or a gust hits the kite, it tries to pull me over forward and knock me down, so I have to lean back. While I'm leaning back, the wind will die and I will fall over backwards.
As you have probably figured out by now, there are a ton of things to pay attention to at a single time. I need more practice, but it is definitely fun. I have gone out three times now. The first time I only went a few hundred feet due to poor wind conditions (either barely blowing or gusts approaching 25 mph lifting me off the ground). The other time the wind was marginal but the snow was good, and I was able to travel at least 1000 meters across the snow. The last time the wind was somewhat gusty, and all the snow had blown off the field. I traveled probably 500 meters before the kite knocked me over knee first onto a patch of ice and I quit for the day.
What may be surprising to those of you reading this from the warmth of indoors is that kiteboarding in 30 below wind chill is not cold at all. I use about every muscle in my body when kiteboarding and I end up overheating and unzipping my coat after a short amount of time. Controlling the kite and snowboard works some weird muscles and I feel it the next day.
Maybe this weekend we will have a good combination of wind and snow and I will try again.
Monday, January 28, 2008
Free GIMP
If you have wanted to try your hand (or pointer, electronic pen, etc) at more advanced image editing than just cropping and basic color enhancement, you should really try out The GIMP. It is available at http://www.gimp.org/. The software is freeware with no fees for use. It is just like the high end Photoshop software, but the cost is much more reasonable.
The software does have quite the learning curve, but it is similar to other advanced image manipulation programs. Once you learn the basics of working with layers and start experimenting with the different image effects, you will get the hang of it. There are tutorials online you can use that will teach you how to do specific things, but at the same time teach you shortcuts, methods, and easy navigation through the program. There are also books you can purchase to speed the process.
The software does have quite the learning curve, but it is similar to other advanced image manipulation programs. Once you learn the basics of working with layers and start experimenting with the different image effects, you will get the hang of it. There are tutorials online you can use that will teach you how to do specific things, but at the same time teach you shortcuts, methods, and easy navigation through the program. There are also books you can purchase to speed the process.
Thursday, January 24, 2008
Graphics
Now that I'm back to the blog, I hope to make it look a little sharper. I was playing around tonight learning some graphics tools and created the "Jeff's Blog" image shown here.
This is my first creation like that, and I'm surprised at the amount of work it takes. There are five layers of different colors, textures, and text to create what you see, including a shifted layer to make a shadow. I think it looks good. I will hopefully make another more detailed version soon to place at the top. Then I will update the photo on the side, or just include it in the main header.
This is my first creation like that, and I'm surprised at the amount of work it takes. There are five layers of different colors, textures, and text to create what you see, including a shifted layer to make a shadow. I think it looks good. I will hopefully make another more detailed version soon to place at the top. Then I will update the photo on the side, or just include it in the main header.
Wednesday, January 23, 2008
A number check on ethanol
I haven't posted on here for a while. I've been very busy over the past six weeks.
The grad school work has kept me busy. Recently I have been looking at biomass, which led me to do some interesting calculations.
Here is the question (when you get into engineering, all questions have multiple parts): If you have an acre of corn grown and converted to ethanol, how much energy do you get? How does it compare to the solar energy striking the ground? How does it compare to a single wind turbine?
From various sources, the amount of ethanol per acre comes out to about 450 gallons. The energy content is equivalent to about 40 GJ (gigajoules, it didn't take long for me to run away form the inferior US units). To put 40 GJ in perspective, that is equivalent to about 11,000 kilowatt hours. That is a deceiving number, because the energy is not available except as heat in that quantity. If the ethanol is used to drive an engine to power a car or produce electricity, the actual amount of energy available will be about 3,500 kWh.
Solar energy strikes the land at a year round average in Iowa of about 160 Watts per square meter. Working out the numbers, 5,650,000 kWh of solar energy strikes an acre annually. Once again, not all can be harvested. Lets figure a photovoltaic panel is used with 10% conversion efficiency, and they are placed to collect about half of the energy available. Even with these low numbers for efficiency, 282,500 kWh of electrical energy is produced. This is about 80 times the amount of energy gained from ethanol.
Wind energy varies, but typical wind turbines output between 4,500,000 and 6,000,000 kWh a year. Each one takes up 1/4 acre of land. They must be spaced apart or else the turbines will interfere with each other and disrupt the wind. Working out the numbers, it takes about 37 acres for a wind turbine. From a one acre plot of land, a wind turbine will output about 120,000 kWh of energy, or about 34 times the output of growing corn for ethanol.
To put the numbers in perspective, if fields were not cultivated at all and turned into a natural prairie with wind turbines covering the landscape, about the same amount of energy would be produced. If we covered 600 square feet of a house roof in solar panels, we would output the equivalent energy of an acre of corn (43,560 square feet).
None of this analysis takes into account the energy input for ethanol. A wind turbine must be constructed, and it typically pays back the amount of energy for construction in a few years. Photovoltaics are the same way, with payback of a few years. Very little fuel consumption goes into the annual upkeep of the wind and solar technologies, compared to the huge amount of fuel that goes into an acre of corn for ethanol.
The problem with any biocrop is the efficiency of photosynthesis. The efficiency is less than 0.5% at best. Corn is only growing for a few months out of the year, and the rest of the year the field is bare and not collecting energy, further reducing the amount of solar energy collected.
Does it require more fuel to make ethanol than we get from the fuel? I am not totally sure. A lot of the pro-ethanol studies are done by pro-ethanol groups. I did a calculation the other day showing that it takes about 1,000 kWh of energy to make the ammonia to feed an acre of corn. Considering we only get 3,500 kWh out of the crop, and I didn't account for transportation of ammonia, corn, ethanol, or the huge amount of natural gas used at the ethanol plant, the net energy gain is going to be very very small.
Keep in mind that the energy food energy consumption of a human is about 2.5 kWh per day. We can feed thousands of meals off of that acre of land if used for food. We can fuel an SUV for less than half a year on the corn energy from an acre of land. Which one should be our priority? Which method of land use (solar, wind, corn ethanol) is the most efficient and best use of our resources?
The grad school work has kept me busy. Recently I have been looking at biomass, which led me to do some interesting calculations.
Here is the question (when you get into engineering, all questions have multiple parts): If you have an acre of corn grown and converted to ethanol, how much energy do you get? How does it compare to the solar energy striking the ground? How does it compare to a single wind turbine?
From various sources, the amount of ethanol per acre comes out to about 450 gallons. The energy content is equivalent to about 40 GJ (gigajoules, it didn't take long for me to run away form the inferior US units). To put 40 GJ in perspective, that is equivalent to about 11,000 kilowatt hours. That is a deceiving number, because the energy is not available except as heat in that quantity. If the ethanol is used to drive an engine to power a car or produce electricity, the actual amount of energy available will be about 3,500 kWh.
Solar energy strikes the land at a year round average in Iowa of about 160 Watts per square meter. Working out the numbers, 5,650,000 kWh of solar energy strikes an acre annually. Once again, not all can be harvested. Lets figure a photovoltaic panel is used with 10% conversion efficiency, and they are placed to collect about half of the energy available. Even with these low numbers for efficiency, 282,500 kWh of electrical energy is produced. This is about 80 times the amount of energy gained from ethanol.
Wind energy varies, but typical wind turbines output between 4,500,000 and 6,000,000 kWh a year. Each one takes up 1/4 acre of land. They must be spaced apart or else the turbines will interfere with each other and disrupt the wind. Working out the numbers, it takes about 37 acres for a wind turbine. From a one acre plot of land, a wind turbine will output about 120,000 kWh of energy, or about 34 times the output of growing corn for ethanol.
To put the numbers in perspective, if fields were not cultivated at all and turned into a natural prairie with wind turbines covering the landscape, about the same amount of energy would be produced. If we covered 600 square feet of a house roof in solar panels, we would output the equivalent energy of an acre of corn (43,560 square feet).
None of this analysis takes into account the energy input for ethanol. A wind turbine must be constructed, and it typically pays back the amount of energy for construction in a few years. Photovoltaics are the same way, with payback of a few years. Very little fuel consumption goes into the annual upkeep of the wind and solar technologies, compared to the huge amount of fuel that goes into an acre of corn for ethanol.
The problem with any biocrop is the efficiency of photosynthesis. The efficiency is less than 0.5% at best. Corn is only growing for a few months out of the year, and the rest of the year the field is bare and not collecting energy, further reducing the amount of solar energy collected.
Does it require more fuel to make ethanol than we get from the fuel? I am not totally sure. A lot of the pro-ethanol studies are done by pro-ethanol groups. I did a calculation the other day showing that it takes about 1,000 kWh of energy to make the ammonia to feed an acre of corn. Considering we only get 3,500 kWh out of the crop, and I didn't account for transportation of ammonia, corn, ethanol, or the huge amount of natural gas used at the ethanol plant, the net energy gain is going to be very very small.
Keep in mind that the energy food energy consumption of a human is about 2.5 kWh per day. We can feed thousands of meals off of that acre of land if used for food. We can fuel an SUV for less than half a year on the corn energy from an acre of land. Which one should be our priority? Which method of land use (solar, wind, corn ethanol) is the most efficient and best use of our resources?
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