When my son Pavlik is confronted by a difficult problem, he invites me to be his “co-author” and uses me as a consultant, information data bank and a live feed back.
The same happened that time. The day before, we were crossing the Dnieper along the causeway near Cherkassy and I was telling him about the work of Kremenchug hydroelectric station, about the cost of the energy it produced, and about flooded lands and dead villages. On the next day, he said, “Father, let us solve hydroelectric station problem with the aid of TRIZ, because nothing comes in”.

Since we did not have any ideas to start with, we decided to use ARIZ. We formulated conditions of the problem, identified a technical contradiction , formulated a mini-problem, determined an ideal final result , and made a sketch. We obtained something like this:
"There is a construction for converting the kinetic energy of water to electric energy. It produces necessary electric power but at the same it becomes impossible to use arable lands that are also valuable.
Technical contradiction:
“To produce a great amount of electric energy, a reservoir must contain as much water as possible, but to preserve arable lands, there must be as little water as possible; that is to say that water must be present in order to rotate turbines and water must not be present in order to prevent land flooding”.
A limitation was imposed on the harmful action, and the following IFR (ideal final result) was formulated:
“Water falls on turbines from a necessary height but does not flood lands.” An absurd idea came off: a layer of water is hovering over the ground and is rotating turbines, while people are cultivating land and cows are grazing in the fields under it.
Having not obtained anything intelligible, we made the next step of ARIZ – we identified operational zones of interaction. They were several, according to the number of turbines. Those zones split the entire layer of the hovering water into a number of small flows that just actuated the turbines. Water flows are normally enclosed in troughs and since they are over the ground, there must be supports under them. In short, already at the second step of ARIZ, a fundamentally new idea of problem solving occurred. To intensify the solution, we examined the resources available within the system and outside it. The most powerful resource under the circumstances is water. In the first place, it (several dozens of comparatively small flows of water) rotates the turbines, and in the next place, it serves as a natural support for those working flows by raising and supporting them at a necessary height. It is the second, auxiliary function that produces a huge negative side effect – floods rich land.
To remove that effect, it is enough to change the base of the working flow which now bears against water thickness, and to make the support not continuous, fortunately we have a wide choice – ferroconcrete columns, piles, masts, and the like. There are also finished water conduits – large-diameter pipes, troughs, etc.
Thus the final solution version will be determined already at the third step of ARIZ. It looks as follows:
Some long water conduits on firm supports supply water from the upper section of a river, in our case somewhere from Kanev, to the turbines placed near Kremenchug or Cherkassy. Not to hamper navigation, they go through shallow waters and sometimes even go out to the banks. In accordance with IFR, water rotates the turbines, but does not flood land, that is, there is no water reservoir as such any more.
Water conduits must run at the level of the upper water face of the existing reservoir, but with a little slope. For a natural flow of water it is enough to have a slope equal to fractions of a degree – that is just the minimal slope the conduit must have; the actual slope of the river is much greater, but due to this difference, a level differential of a few tens of meters occurs at a certain distance downstream.
All in all, the solution is quite acceptable for a training problem, though unexpected and unusual, which is characteristic of TRIZ, though. We gave our hydroelectric station the name of “Trestle”, because water conduits on supports form trestles for water to flow.
Some months passed and Pavlik asked me, “Daddy, why don't they build trestle hydroelectric stations anywhere?”
“Probably because the idea of solving a hydroelectric station problem with the aid of TRIZ has never burst upon anybody except you, because we alone know that it is possible to build such a power plant. Write promptly to your “Yuny Tekhnik” journal.”
Searching special literature and the patent collection proved that our principle of water intake at the upper levels of the river course and supply of this water to the turbines in the lower sections had been used for long. There is a special class of so-called derivational hydroelectric stations based on this principle, but… in our case there are important, critically important differences.
It is quite natural, that difficulties are inevitable in construction and operation of hydroelectric stations. But all those problems are solvable if one wishes to solve them.
Will there be a desire to solve them? Personally, I have no illusions on this point. Pavlik, on the contrary, is very optimistic.

Source: magazine “TRIZ”, 1992