Come Dream With Me: Stirling Engines (Part 2)
Category: Come Dream With Me
The "Come Dream With Me" series is intended to make light of new and promising technologies through works of fiction or direct dictations about where the future might lead. Whenever possible, links are given to support the technology behind the concepts presented in this series.
When we arrived at the garage, Jameson opened the garage door and pointed me to a car inside. It was surrounded by a variety of workbenches loaded with tools. I didn't recognize the make and model, but it was obviously a fairly modern car.
"Here we are," said Jameson. "We got it all put back together for your tour. I'm afraid we like to tinker with it to see if we can improve the mileage."
"This is some sort of custom, high-mileage car?" I asked.
"Sort of. It's actually a modified GM EV-1. The EV-1 was GM's attempt at producing a 100% electric car. To the customers who leased the car, it was a complete success. GM, on the other hand, decided that they would never make any money off the idea and began scrapping the cars. We managed to acquire a few by appealing to GM as a research organization.
"This particular vehicle you see in front of you has been modified from its stock configuration. We've added a Stirling engine to charge the batteries and directly power the vehicle, along with an advanced fuel system that allows it to run on Gasoline, Diesel, Ethanol, Bio-Diesel, Kerosine, and just about anything else we can get to burn with sufficient energy. We can even run the engine on hydrogen or propane, but that would require a very different form of fuel system."
"Wow. So what kind of mileage does this vehicle get?"
"On regular gasoline, we can get 40 miles to the gallon and up. We haven't gotten a proper certification on it yet because we're still working, but it's definitely more fuel efficient than a regular car," he answered.
"That doesn't sound too much better than today's hybrids," I commented.
"True," Jameson responded. "We're working to improve the engine efficiency, and hope to significantly increase the mileage. However, the real key to this vehicle is that it can accept so many forms of fuel. Petroleum products are becoming far too expensive to maintain the economy. The problem is that hydrogen fuel cells are still a long way off, and existing vehicles need special conversion kits to use a fuel other than gasoline. Since it's unlikely that we can expect all the gas stations to start supplying new fuels tomorrow, we need a plan that can phase out gasoline and phase in the alternatives.
"At the moment, ethanol looks like our best bet. It's a little less energy dense than gasoline, but not significantly so. And its per-gallon cost is competitive with gasoline's current prices. If we can encourage car owners to move to ethanol while still supporting gasoline for when it's unavailable, then we may be able to significantly reduce the price of gas as well as the price of ethanol. And for the long term, ethanol is fully renewable. All we need to do is farm more land."
"But doesn't ethanol cost more energy to farm than it produces?" I inquired.
"No, that's old data. Ethanol became energy positive sometime in the 70's when diesel tractors and better farming methods replaced the old gasoline driven tractors. There are a few researchers who cling to the old figures, but the consensus is that ethanol produces a significant energy surplus." he replied.
"Interesting. So what is the performance on a car like this? You said before that this car doesn't have the same response problems as the engine in the plane. How does it compare?"
"Tell you what," he offered, "why don't you climb into the passenger seat and I'll show you?"
"Alright," I agreed.
Inside, the car looked much like any late model sedan. It had all the standard features one would expect, such as a CD Player, radio, air conditioning, heater, front bucket seats, etc. Other than a small computer readout above the radio, I couldn't tell that it was anything other than a normal car.
"What's that?" I asked, pointing to the digital readout.
"That's a debugging tool we use for development. It shows the charge of the whole battery pack, monitors individual battery cells, reports the power output of the engine, informs me of power distribution, and keeps logs of the mileage attained. I know, it looks like something out of Knight Rider," he said with a smile.
Jameson had no key in his hand to start the engine. Instead he merely depressed the "start" button located near the stearing wheel. I didn't hear anything, but several status lights came on and began reporting information. Jameson eased the car out of the garage and onto a test track that surrounded the runway we took off from.
"Ready?" he asked.
Before I could ask for what, Jameson slammed his foot on the pedal, and we took off like a shot! I looked over at the speedometer and watched it climb smoothly toward 60 with no apparent pauses from shifting. Within barely a few seconds, Jameson leveled the car out at 65 miles an hour as we raced around the test track.
"Wow," I mouthed as I let a breath out. "This thing can certainly take off!"
"Yes it can," he replied proudly. "All the power is shunted through electric motors. Unlike internal combustion engines which are tuned to key areas of torque and horsepower, electric motors can produce nearly the same amount of torque across their entire range of operation. Which means not only a fast zero to sixty acceleration, but also a fast sixty to one hundred acceleration. Now the two don't quite compare as greater wind resistance requires more horsepower to overcome at higher speeds, but electric motors certainly have a lot more kick than direct motive power transmission.
"The same technology is used in most Diesel engine trains. The diesel engine is capable of producing power output well above 400 kilowatts (ed note: that's 536 horsepower we're talking!), but gearboxes are unable to transmit that much power to the wheels without self-destructing. The solution was to convert the rotational energy into electricity, then feed the electricity directly to the wheels. This allows modern diesel engines to smoothly apply power to prevent wheel slippage, like you see in the old movies with steam locomotives, and allow fast acceleration. I don't know if you remember from the last train you took, but I think you'll find that they are quite zippy for massing hundreds of metric tons when pulling cars."
"So the torque is more important than the horsepower?" I asked.
"Sort of," he replied. "Torque is a measure of how much horsepower is applied to the rotational axis. In cars, the ability to accelerate quickly tends to be more important than the maximum horsepower that the engine can put out. For most drivers, 50 horsepower is plenty. The problem is that we put 250 to 300 horsepower engines in cars to make up for the slow torque build-up curve of internal combustion engines. A more powerful engine can apply more torque on demand. Still, that's pretty hard on an engine and seriously reduces its life-span. That's why most engines only run for 100,000 to 200,000 miles of the car's lifetime.
"Now for towing, the maximum horsepower can often be more important than how fast the torque can be ramped up. Or in other words, I purchase a pickup truck to haul a 20 ton vehicle, not win drag races. In those cases, the slower acceleration produced by the slower ramp up of torque is less bothersome.
"So in the end, the horsepower is important. What's more important, though, is whether it can be used when it's needed. For road cars the answer has been 'no'. Yet the automotive engineers have done a bang up job of making the public think the answer was 'yes'!"
"You mentioned that the average driver only needs about 50 kilowatts of power. How much power does the Stirling engine in this car put out?" I asked inquisitively.
"Well, up until a few moments ago it wasn't putting out any power! We were driving entirely from battery power. As the car sensed the battery levels dropping, it ignited the Stirling engine and brought it up to speed. Right now," he said as he glanced at the debugging display, "it's producing its optimal 55 kilowatts of power. About 22 kilowatts are being directed to maintain our speed, while the remaining power is being used to charge the batteries. I'm afraid that I put something of a strain on the battery packs with that acceleration stunt. It topped out at about 90 kilowatts of power. Had the Stirling engine been running, it could have provided further power. Unfortunately, the motors can't accept much more than about 100 kilowatts of power, so the acceleration wouldn't have been too much more impressive."
"That's really fascinating," I commented. "What does GM think of this concept?"
"GM is interested, but they're keeping to themselves on this one. They did a few hybrid conversions themselves and decided that it wasn't worth the effort," he replied.
"Could you expand on that?"
"Sure. In the early to mid 90's, GM attempted to build a Stirling hybrid car. Apparently the program met the cleaner exhaust goals they had laid out, but apparently it failed to reach the thermal efficiencies they were looking for. I'm still unclear on what efficiencies they were looking for, so it may be that their failure was simply that the Stirling engines they tested weren't significantly more efficient than the gasoline engines they produced.
"In my case, I'm unconcerned about far greater efficiencies. The primary goal I'm trying to reach is a car that can phase through the alternative fuels coming to the marketplace. As long as the car performs on par or slightly better than existing vehicles, I'm happy.
"To get back on topic, though, GM tried for another type of hybrid in the late 90's. They took one of the EV-1 cars they had, the same type that we're sitting in right now, and added a gas turbine to provide hybrid power. That's where I got the idea of using an EV-1 for my research.
"As far as I know, the program was a complete success. Not only did it produce significantly lower emissions, but it got 60 miles to the gallon. As a result, GM was able to fit the car with a mere 6.5 gallon tank, giving it a range of 350 miles.
"GM never produced a commercial model of the gas turbine hybrid despite its seeming advantages. I don't know for certain why GM abandoned the technology, but my guess is that the turbines were simply too expensive. Chrysler messed with the idea for 30 years, convinced they could find a materials technology that would bring down the price. As you can guess, they never found a solution and abandoned the tech in the 80's. I have my doubts about anyone ever reviving the idea except for special cases such as military HumVees. Perhaps even some busses could afford to fit the engines."
"Interesting," I said. "And you believe that you won't have the same materials problem with Stirling engines?"
"No, not really," he replied as he steered the car off the track and toward where I was parked. "Stirling engines don't really push the limits of materials in any significant way. In fact, it's quite possible that they would have replaced steam locomotives had useful steel been invented earlier. Sadly, the iron technologies of the late nineteenth century were unsuitable for a proper Striling engine, so the idea was shelved. The real pain with Stirling engines is designing a properly tuned engine. Internal Combustion Engines have seen billions of dollars poured into their development. As such, they've become incredibly efficient and responsive for such an otherwise poor technology. Stirling engines have seen very little development in comparison, so we're trying to jump the gap to produce an engine comparable with what the auto manufacturers produce today.
"Well, here's your stop. I hope you enjoyed your visit."
"I enjoyed it very much, thank you. You've given me quite a bit to write about."
As I got out of the EV-1, I couldn't help but think that Jameson's work may forever change the world as we know it. If his technology succeeds, the world will finally be free from the bondage of ever-disappearing oil and high gas prices. Even better, the adoption of the Stirling engine could result in research and development that could produce more efficient engines than ever before. A new, untapped road for automotive vehicles. I hope he does succeed.
The author can be reached for questions, comments, and suggestions at akaimbatman@gmail.com.
Links:
Wikipedia: Stirling Engine
Why Aviation Needs the Stirling Engine (Homepage)
STM Stirling Engine used in the GM HEV
Report on GM Stirling Vehicle
Ethanol Energy Balance (Homepage)
More Information on the Ethanol Energy Balance Debate
GM Turbine Car
Wikipedia: General Motors EV1
The "Come Dream With Me" series is intended to make light of new and promising technologies through works of fiction or direct dictations about where the future might lead. Whenever possible, links are given to support the technology behind the concepts presented in this series.
When we arrived at the garage, Jameson opened the garage door and pointed me to a car inside. It was surrounded by a variety of workbenches loaded with tools. I didn't recognize the make and model, but it was obviously a fairly modern car.
"Here we are," said Jameson. "We got it all put back together for your tour. I'm afraid we like to tinker with it to see if we can improve the mileage."
"This is some sort of custom, high-mileage car?" I asked.
"Sort of. It's actually a modified GM EV-1. The EV-1 was GM's attempt at producing a 100% electric car. To the customers who leased the car, it was a complete success. GM, on the other hand, decided that they would never make any money off the idea and began scrapping the cars. We managed to acquire a few by appealing to GM as a research organization.
"This particular vehicle you see in front of you has been modified from its stock configuration. We've added a Stirling engine to charge the batteries and directly power the vehicle, along with an advanced fuel system that allows it to run on Gasoline, Diesel, Ethanol, Bio-Diesel, Kerosine, and just about anything else we can get to burn with sufficient energy. We can even run the engine on hydrogen or propane, but that would require a very different form of fuel system."
"Wow. So what kind of mileage does this vehicle get?"
"On regular gasoline, we can get 40 miles to the gallon and up. We haven't gotten a proper certification on it yet because we're still working, but it's definitely more fuel efficient than a regular car," he answered.
"That doesn't sound too much better than today's hybrids," I commented.
"True," Jameson responded. "We're working to improve the engine efficiency, and hope to significantly increase the mileage. However, the real key to this vehicle is that it can accept so many forms of fuel. Petroleum products are becoming far too expensive to maintain the economy. The problem is that hydrogen fuel cells are still a long way off, and existing vehicles need special conversion kits to use a fuel other than gasoline. Since it's unlikely that we can expect all the gas stations to start supplying new fuels tomorrow, we need a plan that can phase out gasoline and phase in the alternatives.
"At the moment, ethanol looks like our best bet. It's a little less energy dense than gasoline, but not significantly so. And its per-gallon cost is competitive with gasoline's current prices. If we can encourage car owners to move to ethanol while still supporting gasoline for when it's unavailable, then we may be able to significantly reduce the price of gas as well as the price of ethanol. And for the long term, ethanol is fully renewable. All we need to do is farm more land."
"But doesn't ethanol cost more energy to farm than it produces?" I inquired.
"No, that's old data. Ethanol became energy positive sometime in the 70's when diesel tractors and better farming methods replaced the old gasoline driven tractors. There are a few researchers who cling to the old figures, but the consensus is that ethanol produces a significant energy surplus." he replied.
"Interesting. So what is the performance on a car like this? You said before that this car doesn't have the same response problems as the engine in the plane. How does it compare?"
"Tell you what," he offered, "why don't you climb into the passenger seat and I'll show you?"
"Alright," I agreed.
Inside, the car looked much like any late model sedan. It had all the standard features one would expect, such as a CD Player, radio, air conditioning, heater, front bucket seats, etc. Other than a small computer readout above the radio, I couldn't tell that it was anything other than a normal car.
"What's that?" I asked, pointing to the digital readout.
"That's a debugging tool we use for development. It shows the charge of the whole battery pack, monitors individual battery cells, reports the power output of the engine, informs me of power distribution, and keeps logs of the mileage attained. I know, it looks like something out of Knight Rider," he said with a smile.
Jameson had no key in his hand to start the engine. Instead he merely depressed the "start" button located near the stearing wheel. I didn't hear anything, but several status lights came on and began reporting information. Jameson eased the car out of the garage and onto a test track that surrounded the runway we took off from.
"Ready?" he asked.
Before I could ask for what, Jameson slammed his foot on the pedal, and we took off like a shot! I looked over at the speedometer and watched it climb smoothly toward 60 with no apparent pauses from shifting. Within barely a few seconds, Jameson leveled the car out at 65 miles an hour as we raced around the test track.
"Wow," I mouthed as I let a breath out. "This thing can certainly take off!"
"Yes it can," he replied proudly. "All the power is shunted through electric motors. Unlike internal combustion engines which are tuned to key areas of torque and horsepower, electric motors can produce nearly the same amount of torque across their entire range of operation. Which means not only a fast zero to sixty acceleration, but also a fast sixty to one hundred acceleration. Now the two don't quite compare as greater wind resistance requires more horsepower to overcome at higher speeds, but electric motors certainly have a lot more kick than direct motive power transmission.
"The same technology is used in most Diesel engine trains. The diesel engine is capable of producing power output well above 400 kilowatts (ed note: that's 536 horsepower we're talking!), but gearboxes are unable to transmit that much power to the wheels without self-destructing. The solution was to convert the rotational energy into electricity, then feed the electricity directly to the wheels. This allows modern diesel engines to smoothly apply power to prevent wheel slippage, like you see in the old movies with steam locomotives, and allow fast acceleration. I don't know if you remember from the last train you took, but I think you'll find that they are quite zippy for massing hundreds of metric tons when pulling cars."
"So the torque is more important than the horsepower?" I asked.
"Sort of," he replied. "Torque is a measure of how much horsepower is applied to the rotational axis. In cars, the ability to accelerate quickly tends to be more important than the maximum horsepower that the engine can put out. For most drivers, 50 horsepower is plenty. The problem is that we put 250 to 300 horsepower engines in cars to make up for the slow torque build-up curve of internal combustion engines. A more powerful engine can apply more torque on demand. Still, that's pretty hard on an engine and seriously reduces its life-span. That's why most engines only run for 100,000 to 200,000 miles of the car's lifetime.
"Now for towing, the maximum horsepower can often be more important than how fast the torque can be ramped up. Or in other words, I purchase a pickup truck to haul a 20 ton vehicle, not win drag races. In those cases, the slower acceleration produced by the slower ramp up of torque is less bothersome.
"So in the end, the horsepower is important. What's more important, though, is whether it can be used when it's needed. For road cars the answer has been 'no'. Yet the automotive engineers have done a bang up job of making the public think the answer was 'yes'!"
"You mentioned that the average driver only needs about 50 kilowatts of power. How much power does the Stirling engine in this car put out?" I asked inquisitively.
"Well, up until a few moments ago it wasn't putting out any power! We were driving entirely from battery power. As the car sensed the battery levels dropping, it ignited the Stirling engine and brought it up to speed. Right now," he said as he glanced at the debugging display, "it's producing its optimal 55 kilowatts of power. About 22 kilowatts are being directed to maintain our speed, while the remaining power is being used to charge the batteries. I'm afraid that I put something of a strain on the battery packs with that acceleration stunt. It topped out at about 90 kilowatts of power. Had the Stirling engine been running, it could have provided further power. Unfortunately, the motors can't accept much more than about 100 kilowatts of power, so the acceleration wouldn't have been too much more impressive."
"That's really fascinating," I commented. "What does GM think of this concept?"
"GM is interested, but they're keeping to themselves on this one. They did a few hybrid conversions themselves and decided that it wasn't worth the effort," he replied.
"Could you expand on that?"
"Sure. In the early to mid 90's, GM attempted to build a Stirling hybrid car. Apparently the program met the cleaner exhaust goals they had laid out, but apparently it failed to reach the thermal efficiencies they were looking for. I'm still unclear on what efficiencies they were looking for, so it may be that their failure was simply that the Stirling engines they tested weren't significantly more efficient than the gasoline engines they produced.
"In my case, I'm unconcerned about far greater efficiencies. The primary goal I'm trying to reach is a car that can phase through the alternative fuels coming to the marketplace. As long as the car performs on par or slightly better than existing vehicles, I'm happy.
"To get back on topic, though, GM tried for another type of hybrid in the late 90's. They took one of the EV-1 cars they had, the same type that we're sitting in right now, and added a gas turbine to provide hybrid power. That's where I got the idea of using an EV-1 for my research.
"As far as I know, the program was a complete success. Not only did it produce significantly lower emissions, but it got 60 miles to the gallon. As a result, GM was able to fit the car with a mere 6.5 gallon tank, giving it a range of 350 miles.
"GM never produced a commercial model of the gas turbine hybrid despite its seeming advantages. I don't know for certain why GM abandoned the technology, but my guess is that the turbines were simply too expensive. Chrysler messed with the idea for 30 years, convinced they could find a materials technology that would bring down the price. As you can guess, they never found a solution and abandoned the tech in the 80's. I have my doubts about anyone ever reviving the idea except for special cases such as military HumVees. Perhaps even some busses could afford to fit the engines."
"Interesting," I said. "And you believe that you won't have the same materials problem with Stirling engines?"
"No, not really," he replied as he steered the car off the track and toward where I was parked. "Stirling engines don't really push the limits of materials in any significant way. In fact, it's quite possible that they would have replaced steam locomotives had useful steel been invented earlier. Sadly, the iron technologies of the late nineteenth century were unsuitable for a proper Striling engine, so the idea was shelved. The real pain with Stirling engines is designing a properly tuned engine. Internal Combustion Engines have seen billions of dollars poured into their development. As such, they've become incredibly efficient and responsive for such an otherwise poor technology. Stirling engines have seen very little development in comparison, so we're trying to jump the gap to produce an engine comparable with what the auto manufacturers produce today.
"Well, here's your stop. I hope you enjoyed your visit."
"I enjoyed it very much, thank you. You've given me quite a bit to write about."
As I got out of the EV-1, I couldn't help but think that Jameson's work may forever change the world as we know it. If his technology succeeds, the world will finally be free from the bondage of ever-disappearing oil and high gas prices. Even better, the adoption of the Stirling engine could result in research and development that could produce more efficient engines than ever before. A new, untapped road for automotive vehicles. I hope he does succeed.
The author can be reached for questions, comments, and suggestions at akaimbatman@gmail.com.
Links:
Wikipedia: Stirling Engine
Why Aviation Needs the Stirling Engine (Homepage)
STM Stirling Engine used in the GM HEV
Report on GM Stirling Vehicle
Ethanol Energy Balance (Homepage)
More Information on the Ethanol Energy Balance Debate
GM Turbine Car
Wikipedia: General Motors EV1
posted by AKAImBatman | 9:00 PM
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