This 1968 Opel Kadett hybrid-drivetrain prototype was means forward of it’s time. It’s foremost difficulty was that it was utilizing off-the-shelf lead-acid batteries, and there was solely sufficient room for a small pack (The automobile within the header pic is only a random picture of a inventory German Opel Kadett)
As an electrical automobile in 1968, it was sluggish and had short-range. So far as efficiency, you could possibly have swapped-in a bigger motor and given it extra amps. So, what might we do to supply extra amps? A contemporary Lithium battery pack might simply present an enough quantity of amps for sufficient acceleration to equal the gasoline model. This prototype used 14 of the widespread 12V batteries, for a nominal voltage of 168V.
The highest-speed was close to 55-MPH, which is just too low for life like commuting. If we raised the voltage of the system, it will enhance the facility (for acceleration) and likewise the top-speed. Zero bikes use a nominal (common) voltage of 103V (roughly 117V when totally charged). Two of the Zero packs could possibly be utilized in collection for 206V nominal. The Zero packs are additionally recognized for with the ability to present very excessive amps.
Including roughly 40V to the unique 168V system would positively assist (about 25%), however the amps from a contemporary Zero bike pack would make a HUGE distinction. You is likely to be asking your self why a giant company like Normal Motors (who owns Opel, from Germany), would put any effort and time right into a hybrid the place their earlier expertise with electrics already advised them the electrical efficiency was going to be weak when utilizing 1,300 lbs of lead-acid batteries.
[*Stir-Lec was 3100-lb, and the stock gasoline-engine 1968 Opel Kadett was 1780-lb]
The brief reply is that, they weren’t testing how this is able to carry out as an electrical automobile…they have been testing out the back-up generator that ran by burning any flamable gasoline, and produced no smog.
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Stirling Engines
The “Stir” in Stir-Lec is for the Stirling engine. It took some digging, however I discovered that GM was determined to leverage the prevailing expertise that Philips had with creating Stirling engines (Philips was initially from the Netherlands). The actual Stirling engine that the Stir-Lec most resembles is a mannequin that makes use of the “Beta” configuration, and particularly, the one within the Philips transportable generator, the MP1002CA.
Philips had grown to an enormous world company based mostly on their design and manufacturing of radios within the 1930’s. There was a degree after they felt they might promote extra radios to clients in distant areas who had no grid electrical energy but, by additionally promoting them a generator the place the engine was a small and trendy model of the Stirling. It begins simply and runs very quietly.
The Philips MP1002CA Stirling Generator
Within the pic above, the Beta model Stirling engine is every part on the precise half of the machine. The horizonal cylinder on the highest/left is the gasoline tank which was usually crammed with kerosene. A fan belt and pulleys join the engine to the standard generator on the underside/left. The “cooler” part is merely a set of fan-cooled fins on the underside half of the vertical cylinder of the engine.
The essential operation of a Stirling engine may be very easy. First you utilize a cylinder that’s sizzling at one finish, and chilly on the different. You insert a loosely-fitting steel balloon into the middle, and this half is known as the “displacer”.
If you transfer the displacer to the recent finish, the gasoline contained in the cylinder is pressured into the chilly finish. The gasoline cools and the stress within the cylinder goes down. Then, you progress the displacer to the chilly finish of the cylinder, which forces the gasoline within the cylinder to maneuver to the recent finish. The gasoline then heats up, and the stress within the cylinder rises.
When you then set up a piston at one finish of the cylinder, the rise and fall of the inner stress will push the piston outwards, and a standard crankshaft and flywheel will push the piston again inwards when the working gasoline has is cooled.
Desktop toy Stirling engines can reveal how they work whereas utilizing air because the working gasoline. Nevertheless, hydrogen or helium work a lot better as they take up and shed warmth very effectively, in addition to them having no oxygen to trigger oxidation of sizzling inner components.
One other factor that may enhance the facility of a given Stirling engine is to pressurize the working gasoline. I’d counsel that helium is available at these volumes, and in the event you pressurize the inside of the Stirling engine (maybe to 3 atmospheres) it should cram further helium into it, and that added mass of helium will present further heat-expansion from the identical quantity of gasoline burned…
The pic above is the Philips Stirling generator within the Stir-Lec trunk. The chrome “espresso can” on prime is the heater. The “regenerator” within the pic beneath is a spongy mass that gasoline can simply stream by means of and was constructed from aluminum oxide. It absorbs and sheds warmth simply, and it will increase the effectivity and energy for a given measurement of engine.
The Stir-Lec Stirling engine, a Beta configuration designed and made by Philips.
Saying {that a} Stirling engine doesn’t have any air pollution in its exhaust is a daring assertion. Nevertheless, in 1968, that is the principle motive GM was within the first place. The Environmental Safety Company (EPA) was shaped in 1970, however…even in 1968, GM knew which means authorities laws have been headed.
The common 4-stroke engine is likely to be operating at 2,000-RPM’s because it cruises down the freeway. Because it has one “sparking occasion” at a frequency of as soon as in each 4 strokes (two revolutions), there’s a spark igniting some gasoline 1,000 occasions a minute. that’s 1,000/60= 16 occasions a second!
As a automobile engine will speed-up and slow-down, the excessive frequency of the spark attempting to correctly ignite the gasoline is a demanding atmosphere by which to supply clear exhaust. Nevertheless, the Stirling generator runs at a continuing RPM, and the recent finish is heated by a continuing flame that’s adjusted to supply a clear burn. Additionally, for the reason that sizzling finish doesn’t care the place the warmth on the surface of it’s coming from, a Stirling can use any gasoline from propane to kerosene. This model is known as “exterior combustion”, as a substitute of the gasoline being burned inside an enclosed cylinder, which is well-known as “inner combustion”.
A couple of years again, Jay Leno had certainly one of his classic steam-powered vehicles examined at a California smog station, and it handed all the trendy necessities for a clear exhaust. Steam vehicles additionally use an exterior combustion flame, and it’s utilized to the surface of a water-boiler.
With the previously-stated advantages, you could be questioning why Stirlings will not be utilized in extra functions. Their largest flaw is that they don’t seem to be very power-dense, that means you would wish a big Stirling engine to make a small quantity of energy. The Stirling within the Stir-Lec is a reasonably subtle unit, and but it is just rated for 8 Horse-Energy at 2800-RPM’s.
Street-testing the Stir-Lec confirmed that it’s “steady system state” velocity was 30-MPH. If the Stirling generator is operating and the automobile is touring at 30-MPH, the battery that they used was not draining or filling. This was a helpful baseline efficiency degree for this prototype. A short time later, GM was capable of get ahold of some “subsequent gen” Nickel-Steel Hydride batteries (NiMH) for a pure EV check, and that collection of checks did truly find yourself with them producing 100 of the “EV1” in 1996, however they didn’t return to testing a series-hybrid, which I believe was unlucky…
GM, Ford, Chrysler, and others all tried to make a automobile that ran straight from a Stirling engine (click on right here), however even when the engine was enlarged as a lot as doable, acceleration was too sluggish. That is the place a hybrid would shine. Top-of-the-line traits of electrical drive is how a lot torque they’ve from the primary RPM. Then, throughout the cruise-phase of driving, the vitality drawn from the battery is sort of low, so a back-up generator wouldn’t should be massive to easily maintain it topped off.
My favourite configuration is a “plug in” hybrid. I like Tesla’s, and their prolonged vary battery pack gives over 300 miles per cost. Nevertheless, the bigger battery pack is sort of heavy and really costly. For the overwhelming majority of my driving, I solely want about 100 miles of vary. Nevertheless, for any prolonged journey, a rarely-used generator might enable me to drive any distance I need.
On this situation, I’d cost up my automobile battery each night in my storage, and I’d drive it as an EV virtually day by day of the week. It could be very uncommon for me to ever want the generator to begin and maintain the hybrid operating, however…it will be there if I ever wanted it.
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Locomotives and Submarines
The submarines in WWII have been configured as a series-hybrid. The diesel engines didn’t run the propellers straight in any respect, they solely generated electrical energy to maintain the big battery pack charged up. Additionally, after WWII was over, virtually all of the steam locomotives had been changed by diesel trains, utilizing a series-hybrid drivetrain.
The diesel-electric locomotives have a tiny battery, and the traction motors are pushed straight from the turbines on the diesel engines, by means of a controller.
The previous submarines alternatively, had a really massive battery pack. They’d usually cruise on the floor with the diesel operating. If lookouts noticed an enemy ship on the horizon, they’d dive, flip off the diesels, and run silently on the battery throughout the assault.
The Stir-Lec was extra just like the Locomotives, the place the engine would wish to run on a regular basis, as a result of the battery was so small, however…trendy lithium batteries would have solved that.
The automobile I envision is extra just like the WWII submarines, the place it could possibly run a very long time as an electrical solely, however the engine can activate to cost up the pack if wanted. The truth that the Stirling runs clear and is a real multi-fuel engine is intriguing, however I’m open to any clean-running engine that may spin the generator if a Stirling that matches shouldn’t be highly effective sufficient.
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Gotland-Class Submarines
In 1992, Sweden launched a brand new class of submarine. It’s the ordinary classic hybrid design that depends on electrical batteries to run, and a snorkel that feeds air to a big and noisy diesel-generator to maintain the battery topped off. Nevertheless…
After they wish to run silently with out surfacing for an prolonged time, they’ve a big Stirling engine that additionally generates electrical energy to maintain the batteries topped off (click on right here). These engines burn a mixture of Liquid Oxygen (LOX) and diesel gasoline to create warmth, so they don’t want a snorkel to feed air to an engine. Their massive V4-275R Stirling engine would silently drive a 75 kW generator, and these submarines can run on the Stirling for roughly 14 days.
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Extra Stirling info
When steam engines have been invented, they have been instantly worthwhile for powering factories. Nevertheless, enterprise house owners would usually improve the stress to get extra energy, as a substitute of shopping for a bigger steam engine. This might result in horrific explosions, with demise and accidents. The Scottish minister Robert Stirling questioned if he might design an engine that was safer.
The Stirling engines largest profit was additionally its undoing. It operates at a decrease inner stress in comparison with steam, and there was nothing that enterprise house owners might do to extend the inventory energy. They reliably run practically silent, and so they have been very secure.
For a number of years, Stirling engines loved a substantial amount of success. Nevertheless this competitors spurred steam engine builders to institute coaching and licensing for steam engineers, which diminished the variety of steam explosions. As a result of steam engines run at a MUCH increased stress, you will get the identical energy from a smaller engine, so the steam engines of a given energy vary could possibly be purchased at a lower cost than the Stirlings.
A Swedish engineer named Ericsson seen that Stirlings could possibly be safely run by anybody, with out an costly steam engineers license. He licensed the patent and designed an “Alpha” configuration warmth engine in a number of sizes.
Accommodations and Railroads purchased 1000’s of them to pump water into elevated reservoirs. The railroads would gravity-fill steam locomotives with water from a tower, however there have been many places the place there was not sufficient wind to pump the water up with a typical windmill. The Rider-Ericsson Stirlings have been good for this job.
The accommodations used rooftop cisterns to supply gravity-feed water to their rooms. The water that was pumped would additionally cool the chilly finish of the Stirling, and in consequence, that water was heated within the course of.
I’ve been fascinated by Stirling engines as quickly as I first discovered about them. There have been Stirling turbines that use the warmth from a photo voltaic concentrating dish, with the cold-end being cooled by a easy air-fan and fins. Once more, you would need to make a big Stirling to supply a small quantity of energy, however a Stirling might truly be made by any moderately expert mechanic utilizing easy instruments.
On a plug-in hybrid automobile with an 80-mile electrical vary, the engine is never run, if in any respect. A critic “might say” that burning bio-diesel or ethanol in a Stirling generator nonetheless creates “some” air pollution, however the “PZEV” laws (click on right here) present that clean-burning engines ARE doable. By having a hybrid, you get the efficiency of an electrical car, with a clean-running back-up generator to get you dwelling on longer journeys.
Don’t get me improper, I LOVE electrical vehicles. However build up the grid infrastructure to produce tens of millions of EV’s will take time. We are going to get to a sustainable future finally, however…I additionally need to get to work right now. If I used to be shopping for an alternative-power car right now, it will be a Toyota RAV plug-in hybrid (click on right here).
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LINKS
Dec 1968 Well-liked Science journal, pg 116 (click on right here)
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Written by Ron/spinningmagnets, March 2024
