Importance of Stirling Engines

[bfrobb]

As part of my science fair project I would like to know what, in
your opinions, would best answer the three following questions:

1) What is historically the most important use of Stirling Engines?
2) What is currently the most important use of Stirling Engines?
3) What will be the most important use of Stirling Engines in the
near future (10-50 years)?

I know it is hard to put one answer, but I just need the single most
important use.

[stan.hornbaker]

Two years too late for you project.
Historically the Stirling was intended to be a safe engine, free of dangerous steam explosions, to pump water out of underground mineworks.

Currently and near term the CHP, Combined Heat and Power, applications beginning to increase in number and a consequent decrease in unit costs.