Lots of wasted energy using an entire bulky engine and all of the friction, lubrication, and electronics and sensor requirements (anything newer than 1985 is un

Lots of wasted energy using an entire bulky engine and all of the friction, lubrication, and electronics and sensor requirements (anything newer than 1985 is unsuitable) of it as a "generator". Taking the alternator out and converting it to hydroelectric or wind power is completely doable. That's all you need as the basis for generation. You don't need an entire car. One nice thing about alternators is they are constant voltage sources 14.4V DC over a wide range of RPM inputs after rectification by the trio from 3 phase AC and cleaned up with the VRM. This should be connected to a car battery with very short, very big leads because the voltage is low but the current is high (like a starter). From there, also use short/large leads to either use DC power directly or use a high efficiency inverter (smaller ones are cheap and ubiquitous). Congrats, that's your budget OTG setup. The current rating of the windings, VRM, and of the trio will determine maximum current output. Typically, 2-10 HP will max out an alternator with a rating in the range of 40-200A (560 - 2kW). This is another reason why using a whole automotive engine is pointless: because it's oversized by 2 orders of magnitude. The most difficult thing about powering an alternator non automotive use is increasing the gear enough and mounting it somewhere secure enough to put enough tension on the belt. Rarely will you ever direct drive an alternator. Hydroelectric power with a high head, even with a relatively small stream, contains an enormous amount of potential energy. A Pelton wheel in direct drive maybe possible, but it would probably need slight gear reduction (smaller pulley than the alternator's under high tension with quality bearings on both) for maximum efficiency because the wheel would could be spinning 8k+ RPM. https://www.energy.gov/energysaver/microhydropower-systems https://www.energy.gov/energysaver/microhydropower-systems You can remove the VRM and get ~28VDC but it's going to be ugly and un-regulated. A battery of some sort is required to energize the field coil or no power will be generated.