Parking the van day or night is an important step in van-dwelling. There are things to consider. Are you in an area that is away from people? Is someone going to come knock on your door late at night to ask you to move? (I haven't had this happen). It might be quiet during the evening when you first park, and get very busy in the morning when you still want to sleep.
I have found what is also very important is where is the sun. In the summer, l want to park in a way that l will get as little sun into the van as possible. In the winter, the opposite is true.
It's not winter yet however, l am enjoing the morning sun. It has reached down to the low, low 40's in the night. I just bundle down in my blankets and pass out for the night. In the morning the sun has warmed the van up to a comfortable 65-70 when it is still only 50 degrees outside. How's that for passive solar?