250 volts, 150 watts across 10 meters? The first thing that comes to mind is a bunch of charged batteries, a trebuchet and a big net to catch them. Or, with good nozzle design, a firehose and a waterwheel 10 meters away. Maybe you can do microwaves in space, but it's not going to be practical/safe on earth. There's a reason wires have proven so successful for power transmission.