Unlike most nuclear power sources which use nuclear radiation to generate heat which then is used to generate electricity, betavoltaic devices use a non-thermal conversion process, converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor.
[1] Early semiconducting materials weren't efficient at converting electrons from beta decay into usable current, so higher energy, more expensive—and potentially hazardous—isotopes were used.
The more efficient semiconducting materials used as of 2019[update][5] can be paired with relatively benign isotopes such as tritium, which produce less radiation.
Recent progress has prompted some to suggest using betavoltaics to trickle-charge conventional batteries in consumer devices, such as cell phones and laptop computers.
[4] In 2018 a Russian design based on 2-micron thick nickel-63 slabs sandwiched between 10 micron diamond layers was introduced.
Unlike traditional nuclear reactors, which generate heat and then convert it to electricity, betavoltaics offer non-thermal conversion.
[14] Unveiled in January 2024, it is allegedly generating 100 microwatts of power and a voltage of 3V and has a lifetime of 50 years without any need for charging or maintenance.
Liability connected with environmental laws and human exposure to tritium and its beta decay must also be taken into consideration in risk assessment and product development.
[15] As radioactive decay cannot be stopped, sped up or slowed down, there is no way to "switch off" the battery or regulate its power output.
[16] Although betavoltaics use a radioactive material as a power source, the beta particles are low energy and easily stopped by a few millimetres of shielding.
[17] Safety can be further increased by transforming the radioisotope used into a chemically inert and mechanically stable form, which reduces the risk of dispersal or bioaccumulation in case of leakage.
[18][19] By comparison thermal efficiency in the range of 30% is considered relatively low for new large scale thermal power plants and advanced combined cycle power plants achieve 60% and more efficiency if measured by electricity output per heat input.
[20] If the betavoltaic device doubles as a radioisotope heater unit it is in effect a cogeneration plant and achieves much higher total efficiencies as much of the waste heat is useful.