Their use is traditional in Indonesia, said the fellow working the grill. They don't contribute to the flavor of the satay, but back home, he added, vendors compete to secure a coconut-shell supply as an inexpensive source of fuel.
This same fellow and his wife also sell satay at the periodic Masjid Al-Hikmah food bazaars, from the stall at the front right of the masjid parking lot. Those wonderful bazaars are held only during the warmer months. Through a post on Chowhound, however, I learned that the couple also operate their stall year-round (barring heavy snow) for the lunchtime convenience of men attending Friday afternoon prayers. This is an occasion for fellowship, literally; almost all the customers were men. Although most conversations were in Indonesian, English was also spoken freely, at least when comparing the relative merits of the Android and iPhone platforms.
On the day I visited, the husband was working solo; his wife was present only through the medium of her peanut sauce. Also shown below: cubes of ketupat, or pressed rice, and a plate of lamb satay with ketupat, peanut sauce, and hot sauce ($5). Chicken and beef are the other usual satay options.
Masjid Al-Hikmah satay stall
48-01 31st Ave. (at 48th St.), Astoria, Queens
Fridays, roughly 12:30-2:00