The boil has just gotten underway; the bittering hops are still mostly floating on top at this point. The three gadgets with power cords leading away are heatsticks; they’re basically water-heater elements at the end of pipes. Each dumps 1.5 kW into the pot; 4.5 kW proved to be sufficient to maintain a good boil for a 10-gallon batch. Another heatstick (to bring the total to 6 kW) would bring it to a boil a little more quickly.