"Pellet grills", sometimes referred to as pellet smokers, are backyard cookers that combine elements of charcoal smokers, gas grills, and kitchen ovens. Fueled by wood pellets, pellet grills infuse food with smoky flavor associated with charcoal grills and smokers, but offer the convenience of gas grills and the temperature control of an indoor oven. They have the ability to smoke as well as grill and bake using an electronic control panel to automatically feed fuel to the fire, regulate the grill's airflow, and maintain consistent cooking temperatures. The best pellet grills also utilize sophisticated sensors and advanced algorithms for precision temperature control.
Video Pellet grill
Early history
Pellet grills have their beginnings in pellet stoves. During the 1970s oil crisis, an increased demand for affordable home heating spearheaded a push toward alternative heat sources. One such alternative was wood pellets. Invented in the United States in the late 1970s, wood pellets are small eraser-sized capsules made of compressed sawdust. By the early 1980s, two men, Jerry Whitfield, a Boeing Aircraft engineer from Washington, and Joe Traeger, who ran a family-owned heating company in Oregon, were each experimenting with pellet-burning stoves. Although the stoves looked like traditional wood stoves, they worked much differently. Run by electricity, the pellet stoves utilized a motor-driven auger to deliver a specific amount of pellets from the storage hopper to a fire pot, where a fan aided combustion and blew the warm air from the stove.
Affordable and efficient, pellet stoves became popular in the colder climates of the Northwest and Northeast. While Jerry Whitfield would continue to make a name for himself in pellet stoves--founding Pyro Industries, the largest manufacturer of pellet stoves in the world--Joe Traeger would become synonymous with another pellet-burning product based on the same concept and design.
Maps Pellet grill
Traeger grills
Joe Traeger developed the Traeger pellet grill in 1985 and patented it in 1986. The first Traeger Grills began production in 1988. Traeger Grills have a side-mounted hopper where the firebox would typically be. The grills are electric and controlled by a simple three-position switch. Like the pellet stove, a rotating auger feeds pellets from the hopper to the fire pot, where they are lit by an igniter rod. A fan then stokes the fire and distributed heat and smoke throughout the grill. A metal plate, called the deflector plate, sits between the fire and the grill grate, keeping food and grease from coming in contact with the flames and preventing flare-ups.
This method of cooking, known as indirect (or convection) cooking is also used by traditional charcoal and wood smokers. That similarity, and the fact that wood pellets produce smoke that flavors food, resulted in many early adopters turning to pellet grills as an easy-to-use alternative to traditional smokers.
Cooking with wood pellets
Although pellet stoves and pellet grills both run on wood pellets, there are differences in the pellets they burn. In addition to hardwood, pellets used for home heating often contain softwood and biomass scrap (such as bark), both of which produce a bad taste and could be harmful if ingested. Pellet grills, on the other hand, use food-grade pellets that are made entirely from hardwood and contain no additives, although some manufacturers use soybean oil or vegetable oil as a lubricant during production.
A major benefit of pellet grills is that the pellets are both the fuel source for cooking and a flavor enhancer that infuses food with wood fired taste. Because of their small size and composition, food-grade pellets burn cleanly, producing a light smoky flavor that people associate with traditional BBQ and wood-fire ovens. Wood pellet varieties include oak, maple, apple, alder, mesquite, cherry, maple, hickory, and pecan that each impart their own distinct taste, and can complement and highlight the flavors of specific foods. For instance, fruit woods like apple and cherry pair well with fish and poultry, while hickory and mesquite go well with beef.
Manufacturers often recommend using their own special wood pellets for the best results - as one might assume this isn't exactly necessary. What this really means is that, for the absolute best results with your pellet grill, it's important to use 100% hardwood pellets.
Proponents of wood pellets often tout them as environmentally friendly or a "green" fuel source. That's because they're made from biomass that would otherwise go to waste. The sawdust used in wood pellets comes from sawmills, furniture manufacturers, and tree limbs trimmed during forest and orchard thinning. A sustainable and renewable resource, wood pellets are also considered carbon neutral because burning them produces less carbon than if the wood decomposed organically.
Competition
As a result of its patent, Traeger was the only name in pellet grills for twenty years. During that time, they remained a small family-run business that sold its pellet grills in a limited network of stores. Although the Traeger Grill developed a loyal following among BBQ enthusiasts, pellet grills remained relatively unknown to the average American. However, when the Traeger patent expired in 2006, the doors opened to competition and a wave of imitators and innovators, many of whom saw a product with great potential, as well as an untapped market poised for huge growth.
Temperature control
Like all grills, pellet grill temperatures are largely determined by the amount of fuel consumed by the fire and airflow regulation. However, unlike grills, pellet grills are automated--fuel and air delivery, as well as maintaining the desired temperature, via a button or dial on the control panel. Although this greatly reduces the amount of work done by the user, the process that makes it possible is more complex than traditional grills. For all pellet grills, the basic process by which temperatures are achieved and then maintained is fundamentally the same.
First, the desired temperature is programmed into the electronic control panel. A motor-driven auger then feeds a small amount of pellets from the hopper to the fire pot. Igniter rods light the pellets and prime the fire, raising the grill to an initial starting temperature (140 °F to 180 °F, depending on manufacturer). Once the fire is ready, the desired temperature is achieved via a repeated duty cycle, which represents a segment of time when the auger is active and idle. A single duty cycle starts when the auger turns on and begins feeding pellets then continues through the period when it shuts off and remains idle. The duty cycle ends when the auger turns on again. For example, a pellet grill set to 250 °F might have an auger-on period of 10 seconds followed by an auger-off period of 50 seconds. Duty cycles are typically stated as a percentage that represents the amount of time the auger is running--an auger that's always on has a 100% duty cycle, while one that is on half the time has a 50% duty cycle. Each temperature setting has a different duty cycle. However, regardless of that temperature setting, the auger-on portion of the duty cycle remains constant. The auger-off period is the variable. Lower temperatures have longer auger-off periods, while high temperatures have shorter.
Timing-based controllers (fixed duty cycle)
The simplest types of controllers are timing-based. They utilize fixed duty cycles that are predetermined for each temperature setting. The most affordable type of controller, timing-based controllers are usually found on bargain-priced and entry-level pellet grills.
Three-position LMH controllers
Early Traeger Grills, as well as many of the pellet grills first introduced after the expiration of the Traeger patent, used a simple three-position controller, sometimes called a LMH controller. As the name suggests, the control panel utilizes a knob with three settings, Low (or Smoke), Medium, and High, intended for smoking, baking, and grilling, respectively. Each setting approximates a temperature range, and those temperatures were achieved by means of a fixed, predetermined duty cycle*. For instance, on Medium the pellet grill reaches 300-325 °F by repeating a duty cycle in which the auger feeds pellets for two minutes then goes idle for two minutes. So long as the controller remains on that setting, the pellet grill continuously performs the same duty cycle. Although this type of controller can automatically reach and maintain a predetermined cooking range--give or take 25-50 °F--it has obvious shortcomings. Offering only three temperature settings, with large jumps in temperature between each, limits cooking options and prevents the user from cooking with precision. Furthermore, because the duty cycles are fixed, they don't account for weather conditions or the amount of food being cooked, both of which affect temperature. Thus, on a cold, windy day, a pellet grill with a three-position controller that is filled with meat will struggle to reach its set temperature. The duty cycles themselves are also problematic. The auger-on portion of the cycle is too long, allowing large amounts of pellets to pile up in the fire pot and ignite at once, causing sudden, sharp temperature swings.
Multi-position and digital controllers
The development of multi-position and digital controllers was a step forward for pellet grills, allowing the user more accurate temperature control.
On a multi-position controller, the knob has eight to ten settings, typically in 25 °F increments, from roughly 180-375 °F. The addition of RTD sensors (some manufacturers use thermocouple sensors) inside the pellet grill makes it possible to get an accurate reading of the actual cooking temperature, which can be tracked on an LED display. However, controllers are still limited in how tightly they can hold a temperature. And although they can make small corrections, those corrections are more of a temporary override to the predetermined duty cycle than an on-the-fly recalculation of it. That means that these pellet grills still struggle to reach and maintain a precise temperature in windy or cold weather, or with a larger cook load.
Rather than use multi-position controllers, some brands have switched to fully digital control panels that, in addition to a LED display, use a one-touch interface similar to a kitchen oven. Digital controllers utilize simple microprocessors that work in conjunction with the sensors to create a feedback loop, allowing the pellet grill to make small adjustments to auger activity. The sensor measures the grill temperature and sends the information to the controller, which initiates or halts the auger when the grill exceeds or falls below a specified threshold.
In addition to providing more temperature options, multi-position and digital controllers developed more refined auger duty cycles. The shorter auger-on period allows the pellet grill to achieve and maintain a wider range of temperatures. It also keeps large amounts of pellets from pilling up in the fire pot, helping to prevent those sudden, sharp temperature swings.
The shift from simple three-position controllers to digital controllers has also allowed pellet grills to adopt user-friendly technology like timers, alerts, and food monitoring. Many quality pellet grills allow for the integration of a food probe that allows the user to track the internal cooking temperature of their food on the LED display.
PID controllers (adjustable duty cycle)
With PID controllers, pellet grills moved beyond many of the limitations imposed by fixed duty cycles to become precision cookers with temperature control comparable to the best kitchen ovens. At a glance, PID controllers look no different than a standard digital control panel--both feature a digital display and a one-touch interface that allows you to program temperatures in 5 °F increments. However, although the two may look alike, they are miles apart technologically. A PID controller relies on a continuous feedback loop between sensors in the grill and a sophisticated microprocessor housed in the digital controller. Unlike timing-based controllers, the duty cycles of PID controllers are not fixed or predetermined. They are variable, allowing them to account for changes in weather and cook load, as well as make constant in-cook adjustments to bring the cooking temperature within mere degrees of the set temperature.
Similar to other controllers, when the desired temperature is programmed into a PID controller, the pellet grill ignites the pellets and begins an initial warm-up to a predetermined temperature. Once that has been reached, the pellet grill begins climbing toward the programmed temperature. As it does, the PID controller undergoes a process of trial and error, fine tuning the rate at which pellets are fed by learning how long and how much fuel it takes to raise the pellet grill's temperature under the current conditions. Using an advanced algorithm, the PID controller applies this data to calculate a duty cycle that will achieve the desired temperature. As the pellet grill rises toward the programmed temperature, it will continuously take readings and adjust the duty cycle as necessary. Even after the target temperature has been met, these adjustments continue throughout the duration of the cook. The constant monitoring of temperatures and recalculation of the duty cycle enables pellet grills that use PID controllers to hit the target temperature and maintain it for hours. It doesn't matter if the outside temperature drops twenty degrees mid-cook, the PID controller will correct for the change and recalculate the duty cycle on-the-fly.
In addition to enabling precise temperature control, PID controllers have allowed manufacturers to integrate more advanced meat probes into their pellet grills. More than just a useful monitoring feature, programmable meat probes help the user take even more control of their cook. Once the finishing temperature is programmed into the controller, the pellet grill will continuously monitor the meat's internal temperature then lower the heat when it's done, preventing overcooking. This type of smart technology has transformed pellet grills into true "set it and forget it" cookers that require little effort or attention.
Induction fans
A significant factor in pellet grill temperature control is the ability to regulate airflow to the fire. The improvement in induction fans has paralleled the advancement in controllers. Early pellet grills had fans that ran continuously once the power was turned on. That meant oxygen was constantly being fed to the fire, making it harder to control temperatures. Eventually, continuous fans were replaced by ones that ran in conjunction with the auger-on cycle. However, that still meant that every time pellets were being fed to the fire, so was oxygen. As a result, some manufacturers have incorporated intermittent fans into pellet grills. These fans work independent of the auger and can turn on and off to feed oxygen to the fire only when necessary. Still, intermittent fans blow at 100% strength all the time. For more refined temperature control, a few manufacturers started utilizing variable speed fans, which not only blow intermittently, but can blow at a strength between 0% and 100%, some larger models use two fans.
Open-flame grilling
Like most traditional smokers, early pellet grills were limited to indirect cooking methods such as smoking, roasting, and baking. However, thanks to improvements in construction and advancements in digital controllers, modern pellet grills can produce higher temperatures. Whereas early units struggled to reach 450 °F, some pellet grills can now easily achieve temperatures in excess of 550 °F. Some pellet grills can reach 600-700 °F, depending on the model. The ability to achieve high temperatures has enabled some manufacturers to design pellet grills that can handle both indirect and direct cooking, some models offer the option of open fire grilling. This is usually accomplished through a removable or adjustable plate that allows flames through a portion of the pellet grill's deflector plate.
Differentiation in a growing market
When the Traeger patent expired in 2006, the emergence of new brands helped advance pellet grill design and performance. It also expanded the pellet grill market, providing consumers with more options to choose from. In 2008, two years after the expiration of Traeger's patent, only a few brands were manufacturing pellet grills. By 2014 there were 27 manufacturers and more brands emerging every month. By 2015, pellet grills had made their way to big box retail stores and an even wider audience, causing manufacturers to seek out ways to differentiate their brand from the ever-growing field of competitors.
Strategic partnerships and celebrity endorsements
In an effort to separate their pellet grill from every other one on the market, some brands have partnered with competitive BBQ teams, bringing credibility to their grill and raising the profile of their brand.
Constant evolution
Some pellet grill manufacturers have developed WiFi controls that allows monitoring and customizing cooks through a smartphone or tablet at home or in server mode from anywhere. The pellet grill technology is being integrated into other cooking devices, such as traditional ceramic Kamado style grills, and pizza ovens.
References
External links
- http://barbecuebible.com/2015/02/20/new-pellet-grills/ - pellet grills, general
- http://www.forbes.com/sites/larryolmsted/2014/08/15/the-one-grill-solution-for-backyard-bbq-a-pellet-grill/#60b4bcb1141e
- http://www.woodpellets.com/environment.aspx
- http://www.firecraft.com/history-of-pellet-grills
Source of the article : Wikipedia
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