Some dreamer once wanted to use "super" capacitors to power a road EV but the energy density is still too low. By one calculation a 100 ton cap would be necessary to store the energy in a 15 gallon (100 lb) gas tank.
For electric farm tractors energy density is much less an issue than the lifetime cost of the energy storage device. With enough trolly wiring caps would work better than batteries.
A spread sheet would determine the economic advantage.
It would be interesting to know if capacitors have _ever_ been used in any machinery where the cap is mechanically disconnected and reconnected every few seconds or minutes.
I doubt that a farm, where most of the land is already used for food crops, could produce enough extra crops to supply its own biodiesel. With surging population, we will need most of our cropland to feed people, not tractors, cars, and trucks. We need to reduce consumption, increase efficiency, and live cooperatively. Perhaps enough electrical energy can be provided for our needs with nuclear power, but I'm not sure I want to trust the design, operation, maintenance, and security of these potentially dangerous installations to the latest crop of poorly educated, illiterate, and morally bankrupt people who will be filling positions of responsibility.
Why not use the energy to power the tractor directly? The more times you make it change form, the more you lose. Add to that the gearing losses, which would be considerable. A few hundred thousand rpm needs to be greatly reduced. Getting the flywheel up to speed isn't that easy either. Will you be using an electric motor to do this? Where is this motor located? How will it be wired? Does the tractor go back to the 'refill' site? It may be interesting to find out just how long it does take to get the flywheel back up to speed. Also, are there any weird effects from the gyroscopic action?
Supposedly you can store energy at the same density as liquid fuel simply by stretching the material like a long rubberband. Maybe that's an indication that it'll make a high energy density cap.
But that's far too expensive and I wouldn't want to be around either when it "failed."
Compressed air as well as flywheels may have higher energy density than caps. They present bigger coupling or transfer problems than a wire, however.
Have there have ever been any applications for short term [< few seconds] _completely_ disconnected caps? Up until now a switch, mechanical or electronic, always seems to be permanently connected to a "stationary" power source.
For example, small [low terminal velocity] cap - LED circuits can be designed to be recharged "on the bounce." Each assembly has fins on top to fall down upright into a two layer wire mesh. A short wire on the bottom is insulated except for the bottom tip which contacts the lower mesh. The other contact is the bottom of the assembly itself for the top mesh.
Air pulses upward through the mesh for safe indoor "fireworks."
A lot of easy money has been made where the only design point is whatever will do something visually new. The cost of small circuits is incredibly low with the high copy volume production runs unique to the Christmas light industry.
"The world revolves, not around the inventors of new noises, but around the inventors of new values. It revolves _inaudibly_."
The tech illiterate media have been running shows and articles on some sparsely populated Danish farm island in the N. Sea that is completely sustainable. They do indeed run their tractors off of biodiesel they recover from their farms.
Each farmer's carbon footprint is small but his _land_ foot print is massive -- off shore wind turbines, etc. -- that just isn't available to most Europeans, or, for that matter, most Americans or anyone else except maybe the Australians as a nation.
See the economist Henry George on land which will monkey wrench a lot of sustainability notions.
Geologists are fairly certain there will be a big earth quake in California in 30 years, less than the life time of a nuke. In fact, some of the nukes that are operating in CA today will probably be still operating when they get hit.
A cost-benefit risk analysis would be difficult enough without the politics of where to locate new nukes.
It's a lot easier in CA to just go geothermal, and solar, wind, PV, solar thermal or algae.
Flywheels can be quite dangerous when they are very massive and spinning at high RPMs. Also, I think there are problems with efficiency in the storage and retrieval of energy over a wide range of speeds. There is also the problem of angular inertia causing difficulties with movement of a mobile machine in certain directions. Small flywheels, and fairly small capacitors, are useful for providing short term storage and retrieval of energy.
I wonder how much energy can be stored and retrieved, and what efficiency could be obtained, by pumping water to a higher elevation (either a water tower or a lake on a hill), and then releasing it through hydroelectric generators when needed. This uses simple, inexpensive, and proven technology, and is certainly quite safe. It would not be practical for portable storage, but could possibly be used instead of storage batteries in permanent installations. And stored water is always a good thing to have in case of drought.
While looking for more specific information, I found the following interesting concept:
It was not exactly what I was looking for, but it seems like a worthwhile project to investigate for actually generating electricity by converting solar to wind and then electricity.
Here is a bit of discussion on harvesting energy from a water supply:
According to the data given, 1 square meter of water pumped up to a height of 30 meters weighs 1000 kg, and has a potential energy of 30 kJoules. This is enough energy to power a 30 watt lamp for 3.3 hours. But if you increased the volume stored, and/or could store it at a higher elevation, it might have some benefit. But apparently there is a lot of friction, and hence losses, in plumbing, so efficiency might be a problem.
When I lived in an apartment, we had free hot water. I (not really seriously) considered running the water through a radiator to extract heat, and then also operating a water wheel to run a small generator for lighting. I wonder how long before the maintenance people noticed?
More fool you. They already are, its just currently used as veg oil.
tractors, cars, and trucks.
Nope, we already know how much land is needed to produce the oils currently, and what was being discussed there was whats used to fuel TRACTORS, not the entire transport fleet. With gasoline engines it makes more sense to use LPG or CNG when the gasoline is too expensive to be viable and to use nukes to generate electricity to heat houses etc and stop wasting the LPG and CNG on heating.
Nope, just move away from gasoline and diesel when the price of those stay high enough for long enough.
No perhaps about it, France has been doing that for a long time now.
security of these potentially dangerous
bankrupt people who will be filling
Whatever you are neurotic about, it works fine in France.
All we really need is more work on nukes that cant be used to produce weapons so the countrys that dont already have nuke weapons can use those to produce electricity.
Pumped energy storage, as you say, is proven technology and is currently in use by number of major electric utilities. Unfortunately, this practically requires rather large resoluces, and I seriously doubt that it can easily be scaled down. Most of the white water rafters that run the Kennebec river are familiar with this drill. The Kenneback is fed by Moosehead lake Maine. At a place called "The Forks" it merges with the "Dead River" where a hyrdroelectric dam is located. White water rafters put in right beneath the base of the dam and wait for what is called a "turbine release" (it's a pretty scarey wait for first timers, some of whom actually expect to see water flowing over the top of the dam. These releases take place at the time of maximum electric power demand, and last for an hour or more. Actually, all that you see from your raft is the river level slowly rising, but when it hits its maximum, the rafts take off down river. What follow is the really scarey part, because in the sping this often results in Class 5 white water, something that seriously has to be experienced to grasp the magnitude, and it's definitely not for the faint hearted!
Now most of the turbine releases take place at night, but by agreement the power company reserves a few for daytime. The really big events are on special dates where the power generated turbines are stressed to their maximum capacity. This happens roughly 4 times each year, and the rafting companys charge higher rates for these dates, which attract only the the most serious of the experienced rafters, because during these events it is not uncommon for a raft to flip, and it occupants end up swimming the Kennebec at full flow...which is an experience you may want to skip. At any rate, here is the schedule and this years rates. For what it's worth, I prefer an outfit called Northern White Water, which operated out of The Forks, and has a campground that for their clients is (or was) free.
Just to warn eastern city dwellers, the remote parts of Maine are not quite like Boston, or New York City. Moosehead Lake and The Forks are typical of this region. To get there, you will have to travel lumbering roads, not highways, most of which are paved, but only barely. You will have to compete for road space with giant lumbering truck, which if you have a collision with, you will loose big time, which is to say you definitely don't have the right of way, and remember your defensive driving practices. This is where your SUV or
4x4 may become useful.
Now it is not a popular subject, but it is said that Moosehead Lake is used for pumped storage on a small scale. There are efforts to increase to increase this though siphoning off and stroring the excess energy capacity of Niagara-Mohawk in Moosehead Lake. Obviously this is a very sensitive subject with Moosehead Lake property owners. 'Nuff said.
Regardless of all the above, pumped storage of electrical energy is the best method yet perfected.
On a smaller, more practical scale, take a close look at the mill pond method that has been in practical use since even before the creation of the United States. With a properly situated mill pond, you can extract sufficent energy to power a small mill that can both grind grain and generate kilowatts of electrical power throughout most of the year, even here in New England where it gets cold in the winter. In fact, although I don't want to come across as a New England tourism promoter, you can actually visit a small scale system of this type that is still in current operation.
With this type of system you impound water collected from rainwater or small local streams, then release it as needed to supply your energy requirements. If you are in the Boston Area, and are interested in rather old technology like this, drive out to Sudbury and visit the Longfellow Wayside Inn which is in a turnoff from Route 20, just West of Sudbury. While the Wayside Inn is of historic significance, you should walk across the street to an old, restored Mill that still operates. Wade past the wedding partys that are having their photos taken along side of the mill, and see how it operates. Notice that a mere trickle of water is sufficient to spin the millstones. In fact, all of the milled products sold to tourists at the Wayside Inn are produced here, and the miller there can be very infomative if you catch him between tourist presentations.
Next, go down to the lower floor beneath the milling floor, and in the darkness there you can see 3 old dusty generators of some serious KW capacity. These were installed during the early days of WWII, for use in powering the entire Wayside Inn complex and nearby parts of Sudbury.
When you exit the mill building, go up hill and follow the millstream, and in less than 150-yards you will encounter the mill pond itself. It's won't be as large as some people would have expected, my guess is less than 2-acres, but it has provided sufficient energy to power the mill for the past 200 or so years.
One final stop to make when visiting this historic property is to walk to the extreme left side of the mill, go downhill, and follow the millstream runoff for about another 100-yards, and there cut into the side of the hill you will find the root cellars that have been in use for centuries for storing certain type of produce through the winter, and for all I know may be still in use today. Notice the modern padlocks on their doors.
Now here is the catch. The Longfellow Wayside Inn was purchase by Henry Ford in roughly the 1930s, just as he did Edisons Laboratory. In turn, he carted Edison's lab to Michigan and "restored" it. The old boy, being obsessed with American history, purchase the grounds surrounding the Wayside Inn at about the same time, and "restored" it as well. Perhaps because my wife worked for the National Archives, I am suspect to accept as fact any claimed restoration for its historical accuracy. Even our beloved Concord Bridge is a restoration, and nobody even knows what the orginal looked like.