Correct! Any heat source of sufficient temperature will work, but propane is convenient. I recently took a ferry in Idaho; before loading, people in RVs were to

Correct! Any heat source of sufficient temperature will work, but propane is convenient. I recently took a ferry in Idaho; before loading, people in RVs were told to turn off their refrigerator to reduce fire risk. Searching for "absorption refrigerator diagram" (or checking out the wikipedia page) should provide useful information.