Explain why solar power is a poor alternative for people living in the north of sixty degree?

Solar power at any latitude is uncertain. It depends on insolation, which means the amount of sunlight that actually reaches the collector. That is affected by atmosphere, clouds, dust, trees, animal droppings, and anything that blocks sunlight. The farther north you go, the more atmosphere the light has to go through, so at some point the amount of light is just not worth the expense of collectors, even before you consider trees and dust. It is cheaper to haul fuel from somewhere else to run generators.