For a change I am writing this about a non-railroad issue. It is the English translation of the German article Entwässerung mit Osmose.
Osmosis is described quite well in Wikipedia. In short, mixing of salt solutions with different concentrations sets free some energy. For example when mixing fresh water with sea water, this energy is equivalent to a falling height of 270 m (not 2.8!!!). By using a semi-permeable membrane between the two salt solutions, water molecules will diffuse through the membrane until the sea water side is about 270 m higher than the fresh water side, if dilution of sea water during this process is neglected.
About 30 years ago I have heard about the idea of building osmotic power plants at the mouths of rivers to the sea. They seem to have built a prototype of this recently in Norway and intend to produce 10% of the electricity demand of Norway by osmotic power. This indicates that the concept might become mature soon, even though few countries have as much precipation per inhabitant as Norway, so the achievable percentage will be much lower in most countries.
Another interesting use case of this technology could be draining land areas that are below sea level, like part of the Netherlands or New Orleans. I am sure that there are more of these. Today draining is mostly done by using electric pumps, which consume quite a significant amount of energy. As long as the height difference against the lower tide is less than 270 meters, draining could actually be achieved by using some kind of osmotic pumps without using electricity. Since the height difference is less, it would even be possible to produce some surplus electricity.
I expect that we will see this implemented in areas where applicable within the next ten years, since the osmotic power plant shows that the technology needed for this is becoming mature.
(translation of Ein Gleis alleine genügt nicht)
Building and maintenance of transportation routes is often considered to be a responsibility of the state. It is assumed that everybody can then use this routes.
For transportation of persons this is only partly true. A highway can be used by individually owned means of transportation, like bicycles or cars or motorcycles.
For using a railroad line as passenger, a scheduled operation is needed, because passengers do not have their own trains.
This operation works best, if the whole system is planned or at least coordinated centrally, with connection in major stations, maybe even with operation in consistent intervals and better usage of the track capacity. Such systems have been established in some countries, for example it has been done very well in Switzerland.
Now such a system works best, if the portion of the travelers using it is as large as possible, if only it can be assumed that railroad network capacities are expanded when congestion is getting too high. In many parts of the world the demand for expanding congested highways with tax money is considered self evident, even though planning, financing and building may take its time. So if railroad lines are subject to such expansion where high numbers of travelers cause congestion, then the system can work better with more travelers for the following reasons:
- Longer trains and bilevel trains can transport more people with only one railroad engineer (motor man) and one trains path. Less energy per passenger is used in this case.
- If trains operate more frequently, the system gets more attractive for travelers.
- If many trains are operated, more connections can be offered without transfer.
- If many trains are operated, some of them can skip part of the stops and still leave a high level of service for all stops. This can be used for shortening travel times and saving energy that would be needed for acceleration. An example are the New York subway lines 1, 2, 3 and 9. Lines 1 and 9 combined serve all stops, with about 1/3 of the stops only being served by line 1, 1/3 only by line 9 and the remaining 1/3 by both. Lines 2 and 3 are express lines that skip about 3/4 of the stops. All 4 lines are bundles throughout most of Manhattan.
- If many trains are operated, it is possible to provide stops closer to the real source and destination of the trip, this shortening the „last mile“ of the door-to-door connection.
To make full use of these advantages, the railroad operator must be well run, like for example in Japan or Switzerland.
I makes some sense to have a government controlled organization that does not only build and maintain railroad lines (or has them built and maintained by some companies), but that also provides a scheduled operation. This could be a well run federal railroad operator, like in Switzerland, but it could also be an organization that plans the whole system with all schedules and lets companies operate the trains as subcontractors.
It can be seen that this system works quite well in Switzerland, while the attempt to leave passenger traffic to private companies has generally failed in the United States.