There are a number of current and emerging technologies for generating electricity. For the aspiring mad scientist you should consider the advantages or disadvantages of them first.
The most exciting ones so far are Liquid Thorium Reactors, and Plasma core generators. But there are various other older types - almost all of them basically little more than an old fashion steam engine. Gas, Geothermal, Coal, Oil, Nuclear, Plasma, Liquid Thorium, Solar reflector - etc.
Happily there are some more modern technologies, which all have limitations too - Solar, Wind, Wave, Atomic Decay, Fuel, Hydro, Thermal transfer, Resonant, Tesla Turbine
Basically burning gas to heat water to steam then spinning a turbine. Due to low emissions, popular with uninformed yuppies but expensive. You could also use it to turn a turbine directly; but not known to be used this way. Another adaption would be running an internal combustion engine to drive a dynamo.
Handy if your lair is on a volcano, but basically forcing water into the ground to be heated by mantle heat into steam, then.. spinning a turbine. Fairly Cheap; not very efficient, but not wasteful or toxic. Very easy to setup too if existing groundwater is venting as steam nearby anywhere.
Basically burning Coal to heat water into steam to spin.. a turbine. Been a lot of innovation here, including air filtration and fuel drying techniques; which permit biomass fuels like woodchip. Can easily be adapted to any other sort of steam based plant. Just replace the furnace. Pretty cheap but wasteful. Doubt any further innovation is possible however.
Rare and inefficient, burns oils, fuels hydrocarbons etc, heats water, spins turbine.. Cheap but highly polluting. Variation on this is diesel electric generators. Internal combustion spins a dynamo basically.
Makes radioactive materials heat up water into steam and spin a turbine; very little innovation here, particularly in the USA who primarily use weapon grade material.. as it is easy to make bombs under the guise of power station fuel, however minor tweaks in Canada created the “can-do” system which runs on non-military grade materials like normal uranium, and the Japanese system which slightly improves efficiency by using little ball pellets of fuel material. Dead end research branch. Expensive, toxic, dangerous, and highly inefficient.
The first real innovation in decades, although it is still basically a steam engine, it can be ran on anything you feed into it to keep the plasma burning. Even has useful waste products in the form of hydrocarbons and rubble for building materials. Better suited for smaller applications or space systems where consuming unlimited materials and ejecting waste is not a concern. Does require a significant “start up voltage” however. You will want big batteries; or some other backup source of short term power to run the microwave transducer to initially heat up to plasma.
Technically Nuclear, it shares very little in common, as this form has no military weapon applications. A major innovation from the USA in the 1950's it has languished in obscurity for decades as the military could not work out a way to weaponize it. See http://energyfromthorium.com for more details. Basically it creates a unique closed loop reaction; that simply requires occasional “top ups” of fuel to maintain the reaction. Works by using Thorium and Fluoride in liquid form instead of solid fuel rods. It then… heats water to spin a turbine. Waste products include very rare radioactive isotopes used by medical research and space research. So far only China and Pakistan has any plans to use it, and if they succeed - it could result in them becoming major world superpowers, without ever needing to fire a single bullet - as they will have a monopoly on the intellectual rights of technology and fuel. Not to mention virtually unlimited energy available to sell to other countries or use themselves.
Very easy to make, basically focus sunlight either with mirrors and/or lenses onto a water container, which then heats up into steam and turns a turbine. Fiddly but fairly cheap; wastes a lot of space however - and wont work at night. Would work best in orbit.
Converts heat or cold into electricity and vice-versa. Wikipedia Uses a principle sometimes nicknamed dantes inferno, distantly related to how refrigeration works, and a Peltier plate can be used as a heater, refrigerator, or power generator. See Thermal transfer.
Solar is basically a radiant technology. It could easily be adapted to run on other forms of radiation, however it does not appear to have occurred to anyone to try. Basically it converts solar/photon radiation directly into electrons and electricity. Efficiencies vary a lot, but it wastes a lot of space for a relatively trivial amount of power. Handy where you have a lot of wasted space like roofs.
Wind power replaces steam with wind to spin a turbine. Cheap, simple, and a bit nasty. Current designs are highly inefficient and wasteful. It would make more sense to have a number of blades linked to a common torque converter and have it spin a conventional power station dyno, but presumably it is more profitable to make more wasteful stand alone units with pitiful sized generator capacities instead. Another variant could be to use wind power to pump water into a geothermal system, and use the resulting steam to turn a conventional power station sized turbine too. Either way it has not occurred or been deemed not profiteering enough to use these variant configurations.
A real clever mad scientist idea this. You have a number of specially designed pontoons which go up and down with wave action and running a special dyno to generate power. Variants include underwater systems too which exploit underwater currents, or tidal action rip tides. Not particularly practical however.
Used by NASA, for the “mythical” atomic battery piles. Despite mainstream media denying the existence of real “atomic” batteries, (beyond TV shows like the million dollar man; the denials are probably more that if we had batteries that took centuries to go flat a lot of battery makers would go out of business) they have been used in various forms for decades by NASA, and Military as power supplies for space crafts to power their radios; and more recently to power the Ion propulsion system used officially by the last deep space probes, and unofficially by mysterious unnamed military vehicles for unknown purposes. Main issue with these is the fact it requires relatively rare radioactive materials, which have nearly all been used up on Earth, and can probably only be created in liquid Thorium reactors.
Home and Business grade generators, basically an internal combustion engine running on Petrol, Diesel, Oil or Kerosine, which spins the generator dyno.
Basically change the size of a steam turbines blades, jam it into a Dam, and then push water through it down a river instead to spin the turbine. Clever, and virtually no pollution. Doesn't do the fish much good tho.
A number of designs for this exist, most rely on the Peltier effect; although a number of test units have been built. They are not used in large scales facilities. These draw off electricity by passing hot air over a series of ceramic plates. Some crazy people have even suggested this is what the great pyramid is. Some rely on simply hot air, by creating a large tower, with a air turbine at the top, and a hole at both ends, as the air heats up it rises though the tower turning the turbine. In some configurations heat helps but is not essential, wind passing over can be enough. Another rare design is the solar water system. The sun heats up a series of pipes containing water, and when the hot water rises it turns a turbine.
Tesla's final project before he was bankrupted by Westinghouse (and/or Bell labs?); this works in 2 possible configurations. Basically it is the crystal radio effect. In the first configuration you have a receiver near a specially designed transmission tower. It draws power from the tower; in a reverse ground sort of setup; this is then fed into a transformer and fed to the appliance. In the second configuration, you used resonant “affinity” which is basically how radio and a crystal radio works, you tune the receiver to the frequency of the power you wish to draw on, then attach your receiver to its load. This generally doesn't need a transformer; unless you need regulating, just a grounded load. In theory a unit could be tuned to background cosmic radiation; but in practice it is more effective tuned to a regular signal, such as radio or 50/60hz radiation from power lines.
Basically a special sort of turbine that works a little like a Rotary RX7 motor, it can be driven by anything from Water/Air/Steam (like a normal turbine) or on fuels liquid, gas, OR powder. It is the only known engine where in a combustion configuration can run on a powdered fuel. Sadly most people don't understand it enough to implement the combustion configuration, but it works as a fairly efficient turbine on its own to drive a dyno with steam or water.
Polywell is the nearest thing to Ironmans arc reactor Wikipedia; presumably uses magnetic containment to form a plasma similar to the plasma system above, however it has other properties, for instance xrays and could be adapted to use direct thermal energy conversion, similar to the peltier effect - or due to the flow of ions, could perhaps be used to directly tap energy. As such this can be used with a conventional steam turbine - or omit that part entirely. Has certain limitations, which many researchers are attempting to deal with - mainly concerned with losses, and waste emissions.