Electrons in a conductor react not only to voltage but also to temperature gradients. In their motion, they carry electric charge as well as energy. This makes it possible to think of devices that are absorb excess heat from their environment and convert it into useful power. This can be done in three terminal devices: Two terminals support the charge current with the third one serving as the heat source, enabling the separation of charge and heat flows.

Mesoscopic (nanoscale) systems are good candidates for this, because of their high degree of tunability and rich variety of different effects that allow for the mechanism of heat to power conversion: Coulomb interactions [1], resonant tunneling [2], entanglement [3], quantum interference, or the absence of thermalization [4].

I will review recent proposals and experimental implementations of three terminal energy harvesters.

[1] R. Sánchez, M. Büttiker, Phys. Rev. B 87, 075312 (2011); H.

Thierschmann et al., Nature Nanotech. 10, 854 (2015); B. Roche et al., Nature Comm. 6, 6738 (2015).

[2] A. N. Jordan, B. Sothmann, R. Sánchez and M. Büttiker, Phys. Rev.

B 87, 075312 (2013); G. Jaliel et al., Phys. Rev. Let. 123, 117701 (2019).

[3] R. Sánchez,P. Burset, and A. L. Yeyati, Phys. Rev. B 98, 241414 (2018).

[4] R. Sánchez, J. Splettstoesser and R. S. Whitney, Phys. Rev. Lett. 123, 216801 (2019)