The piece of the puzzle that you're missing is the dams at the far end of the road divert the Caniapiscau River into the La Grande River, which provides close to half the water that eventually feeds all of the generating stations downstream.
Additionally, the reservoirs formed are important for making the system provide reliable power to match demand - demand for power in Quebec peaks in the coldest parts of winter, and the natural peak of runoff/river flow....is not then.
So, the generation out there is useful but is not the primary reason why the road was built all the way out to there.
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No special insight on the difficulty/expense of constructing the transmission, but ~788MW of extremely cheap power forever for constructing/maintaining ~130mi of extra transmission doesn't seem completely improbable to work out financially, especially at the time.
I'll also note:
- Vegetation maintenance costs are probably low given how slow things grow out there.
- This was constructed long before the modern era of cheap(er) renewables.
- Even today, Quebec's location, weather, and time of year of peak demand make the calculation for solar's cost-effectiveness a lot harder.
Additionally, the reservoirs formed are important for making the system provide reliable power to match demand - demand for power in Quebec peaks in the coldest parts of winter, and the natural peak of runoff/river flow....is not then.
So, the generation out there is useful but is not the primary reason why the road was built all the way out to there.
--------
No special insight on the difficulty/expense of constructing the transmission, but ~788MW of extremely cheap power forever for constructing/maintaining ~130mi of extra transmission doesn't seem completely improbable to work out financially, especially at the time.
I'll also note:
- Vegetation maintenance costs are probably low given how slow things grow out there.
- This was constructed long before the modern era of cheap(er) renewables.
- Even today, Quebec's location, weather, and time of year of peak demand make the calculation for solar's cost-effectiveness a lot harder.