Pulsed Power Agriculture; Design of Pulsed Power Generator and its Applications in Agriculture

This paper provides an overview of pulsed power applications in agriculture to contribute to a modern food supply chain, based on our research results. These applications are primarily based on the biological effects of spatially distributed electric fields and chemically active species in plasma driven by pulsed power generators (PPGs). For such applications, compact PPGs with moderate peak power and repetitive operation were designed and developed to control discharge plasmas and electric field distributions, thereby enabling the selective induction of desired bio-effects at different agricultural phases. A key issue for agro-applications using pulsed electric fields (PEFs) is the creation of multi-reaction fields of plasma and PEFs with precise spatial and temporal control, allowing adaptation across biological scales, i.e., matching the pulse width to the relaxation time. To achieve this, the power semiconductor switching devices such as SiC-MOSFETs were employed in the development of compact PPGs capable of repetitive operation with low energy loss. These compact PPGs were applied in various agricultural phases and optimized in terms of electrical parameters such as applied voltage pulse width, repetition rate, and circuit impedance. In the pre-harvest phase, two approaches were investigated for enhancing plant growth: (i) direct stimulation of plant tissues using PEFs and (ii) indirect stimulation by exposing cultivation media to PEFs or plasmas. The PEFs were applied to mushroom cultivation beds to promote fruit body formation. In hydroponic systems, nanosecond streamer discharges generated in air bubbles under the nutrient solution were used to inactivate pathogenic bacteria, and promote nitrogen fixation, thereby contributing to plant growth. In post-harvest phase, the compact PPGs were developed to drive the plasma reactors for to the rapid decomposition of C₂H₄ to maintain the quality agricultural products.