Starch Particles, Energy Harvesting, and the “Goldilocks Effect”

[Image: see text] This study reports on the unique water vapor adsorption properties of biomass-derived starch particles (SPs). SPs offer an alternative desiccant for air-to-air energy exchangers in heating, ventilation, and air conditioning systems because of their remarkable adsorption–desorption performance. SP(15) has a particle diameter (d(p)) of 15 μm with a surface area (SA) of 2.89 m(2)/g and a pore width (P(w)) of 80 Å. Microporous starch particles (SP(15)) were compared with high amylose starch (HAS(15); SA = 0.56 m(2)/g, d(p) = 15 μm, P(w) = 46 Å) and silica gel (SG(13); SA = 478 m(2)/g, d(p) = 13 μm, P(w) = 62 Å). Transient water vapor tests were performed using a customized small-scale energy exchanger coated with SP(15), HAS(15), and SG(13). The water swelling (%) for SP(15) was ca. 2 orders of magnitude greater with markedly higher (ca. three- and six-fold) water vapor uptake compared to HAS(15) and SG(13), respectively. At similar desiccant coating levels on the energy exchanger, the latent effectiveness of the SP(15) system was much improved (4–31%) over the HAS(15) and SG(13) systems at controlled operating conditions. SP(15) is a unique desiccant material with high affinity for water vapor and superior adsorption properties where ca. 98% regeneration was achieved under mild conditions. Therefore, SPs display unique adsorption–desorption properties, herein referred to as the “Goldilocks effect”. This contribution reports on the utility of SPs as promising desiccant coatings in air-to-air energy exchangers for ventilation systems or as advanced materials for potential water/energy harvesting applications.