Issue link: http://palletcentral.uberflip.com/i/1194984
palletcentral.com PalletCentral • November-December 2019 31 negative) will move and vibrate as fast as the RF field is shifting, causing friction-based heat. The 6.78 MHz frequency means that the electric field will alternate and rotate water molecules 6.78 million times per second; imagine how much friction it creates! Similar to your microwave, RF efficiently heats material from the inside. However, unlike microwaves, RF penetrates at a greater depth allowing for packs of wood, and larger dimensional material such as dunnage, to be heat treated more effectively. Just like heating dinner in a microwave, RF is much faster and more energy efficient than heating using a conventional kitchen oven. RF Kilns are considered to be direct heating so when power is applied the wood begins to heat instantly throughout the whole volume. Conventional kilns are considered to be indirect heating which requires large volumes of heated air to transfer heat to the wood slowly from the outside to the core. Estimates show that conventional kiln systems are only about 10% efficient because they lose most of their energy from heating the wood from the exterior inward, whereas RF technology which heats from the core out provides approximately 70-80% energy use efficiency. Conventional kiln heat treating costs range from $1.25 to $0.25-0.50 per GMA pallet. Dry kiln energy costs alone fluctuate ºbetween $0.11-0.25 per GMA pallet depending on fossil fuel prices. Other approaches, such as methyl bromide (MeBr) fumigation have environmental implications, can be even more costly or are difficult to access. RF heating offers a potential alternative method for facilities to gain ISPM 15 treatment compliance. RF technology is not new to the wood industry. It is currently used in high value applications such as drying large timbers or valuable hardwoods. However, applying RF for the phytosanitary heat treatment of wood is considered to be a new application for this technology. Over the last 15 years our team of scientists have systematically developed a commercially viable RF system beginning with limited bench testing and then moving to a 1200 board foot pilot scale chamber on site at Penn State University's Forest Research Lab. Recently we completed full scale commercial trials with similar successful outcomes. The research team has conducted over 50 heating trials with a variety of commercial wood species and dimensions that are common in pallet manufacturing. Heat treatment schedules are being developed as a result of these trials which will lead to easier pallet manufacturer adoption of RF technology to comply with ISPM 15 standards. Current testing with feedback from several cooperating NWPCA manufacturers indicates significant savings for phytosanitation treatment. Savings are due to lower energy costs (~$0.05 for RF treatment vs conventional heat treatment at $0.11 -0.25/GMA pallet) and potential labor savings since inline placement of an RF cylinder is an option. In addition, RF chamber life is estimated to be 20 years, which is approximately twice as long as many standard dry kilns. Commercial scale RF heat treatment units are available at 8000 bdft capacity for an approximate installation cost of $281K. Typical dry kilns can cost from $90 to $150K depending on capacity and features. RF kilns have the ability to heat treat enough material in one charge to produce ~590 GMA pallets