What about flying a key from a kite or something and waiting for lightning to strike it? There’s a lot of power in lightning, apparently.
Or, I’m sure the A team did something with some old oil barrels and lengths of pipe when they were trapped and needed some power urgently. Can’t quite remember the details, but a quick run through their shows on DVD would probably reveal the answer?
Could you move the site to one where there are several leylines colliding and use the resulting forcefield to power everything?
Trust that helps.