During winters the only natural source of warmth is the Sun light. In grassy field one will get a lot of Sun light while the forest will receive a lot less Sun light. In absence of winds the heat received from the Sun will be more in the grassy field as compared to a thick forest.
Thus, grassy field will be warmer in comparison with a thick forest.
I think it would be warmer in a grassy field with no wind on a winter day because you'll have sunlight hitting you. However, if you were in a thick forest, all sunlight would be blocked and you would have no warmth from the sun.
because solar enegry is a perpetual source of enegry and by using it non renewable sources of enegry can be preserved and also prevents from enegry crisis.
