Has anyone done the maths on this (I haven't RTF)..

Assuming this ONLY works on gravity the most force obtained by system is:
F = m x a (assume car is 1 ton and acceleration is 9.8)
F = 9800 N (say 10 kN)

Work produced by system from car travelling over hump:
W = 2 x F x D (assume D = 10 cm, which is a big hump note 2 x force as run over hump twice front and back wheels)
W = 2000 J

The power output for that one hour is:
P = W / t
P = 55.5 W

Assuming we only need 8 hours of light, so we have can say the power supplied is 160 W (Approx 0.2 KW not 10 KW as reported).

Someone can check my reasoning, but 10 KW as stated seems quite high for using gravity of the car.