Pyroelectricity could extract energy from heat sources below 100°C

"PMN–0.32PT thin films are shown to provide record-breaking pyroelectric energy con - version, including: first, the largest energy density of 1.06 J cm − 3 (at Δ T = 90 K, Δ E = 267 kV cm − 1 and f = 40 Hz; Fig. 4a), which is made possible because of the large field-induced value of π and the ability to apply large electric fields maximizing the electrical work ( ∮ ⋅ EP d ). Second, the largest power density of 526 Wcm − 3 (at Δ T = 56 K, Δ E = 267 kV cm − 1 and f = 1,000 Hz; Fig. 4b) that is real - ized because the power density scales directly with cycling fre - quency, which can be increased because the thermal time constant of the thin-film geometry is small."

Note the operational constraints. You have to apply a varying electic field and a varying temperature.

I think this only applies if we're constraining the temperatures to typical summer outdoor/indoor cooling applications. Different technologies are going to have different temperature ranges at which they are most efficient, so for something like steam power generation multi-stage systems are common.

But imho the real market for these will be in low-power environments. Or defense: submarines have near-unlimited heatsink potential and lots of <100 heat sources.