There are thousands upon thousands of different energy sources available to spirits, ghosts, etc. Why don't they take the sun's energy? Why not from electrical equipment or things like that? It's my personal belief that energy is much the same thing in different speeds and wave lengths. . . And, here's a comparison for ya. Ever tried to fill a bucket of water using a water fall? It's much more difficult than using a slow river current. You have to get to the waterfall, which is already difficult enough, and then, when you think the hard part is done, it's time to push the bucket under the water. Yap, it'll go right in... but now you're getting tired; the weight of the falling water is crashing dead-stop-and-rebound into the bucket, and once it's to the top, the water still crashing in splashes what's to the brim right back out. It's a lot of trouble, and then, in the end, you end up drinking what water you gathered because you're thirsty as hell after the strain. And THEN you have to PEE, so you go to find a ROCK to hide behind...

Okay, I'm kidding about the last part. You get my point, though. Electrical components like batteries and power lines, the sun, and things like that are all the wrong type of the same energy. I call it chaotic energy. Many energy workers take what they need from the sun, or from other such things. (Never heard of willful battery sapping) However, I don't believe 'feeding', as it may be, is a quick and easy process. (for us, anyway) Just like with the water, the type of life energy we need is taken in small amounts, steadily, over a short or long period of time. Maybe it's the same for ghosts and some spirits. Then again, there's a big difference between different energetic beings... I suppose they all have different tendencies.

Anyway, best I can come up with for psychic protection against malicious or seemingly harmful (parasitic) beings is simply to practice shielding and welcome the being. Now, I didn't say welcome it into your body... Last time I had to deal with any sort of ghost, I made an offering of earth-charged crystals, salts, and fresh peppermint leaves in a circle on the back lawn of my friend's house. (The problem was at his house.) It seemed to work, or else my friend had lied to me about the solution's effect. You just have to give them a little persuasion, sometimes, to leave you alone. I wouldn't think they would react well to a psychic retaliation.