Suppose I was designing an apparatus which needed to lift 250kg 5cm high, hold it there for a few seconds, and then lower the object back to the original height. Such a process would need to be repeated every certain time interval.
What kind of mechanism (pneumatic, hydraulic, electric, etc) is likely to have the least overall energy losses? Please also describe the type of energy reservoir for the solution you propose (e.g. for an electric motor, would you use a certain type of battery or capacitor etc.)
Update: it's impossible in my system to add any sort of counterweight due to the size and weight restrictions on the apparatus.