Meet the Contestants; Intercontinental

With the first Wood Stove Decathlon only a few months away, the Alliance for Green Heat is doing a weekly blog to showcase the Decathlon competitors. Take this opportunity to learn more about the teams and their stove’s innovative features.

Rod Zander of New England Hearth and Soapstone, has worked with masonry stoves for decades. He gained experienced in the interior mechanics of masonry stoves through several international apprenticeships. Among the nation’s foremost experts on masonry heat, Zander has taken this knowledge to develop a very unique stove that will compete in the Wood Stove Decathlon.

Perhaps aspiring to reach the international marketplace, the competing stove has been named Intercontinental 2B4W. Surely, its innovative features make the stove appealing regardless of which continent you’re on. The stove is an exciting new type of masonry stove that can be created from recycled materials. The recycled materials not only help reduce waste, but save both the manufacturer and consumer money. These readily available materials can easily be assembled with local labor cutting costs even more. It is hoped that these stoves will have a real application in developing countries, where other fuel sources are too expensive and current stoves are too polluting.

The form of the stove is composed of two used steel oil drums stacked on top of each other. The symbolism of the oil drums is not lost on the stove designers. The use of an antiquated fuel source’s containers expresses the continual shift towards renewable energy.

The heat is stored in high-density firebrick, which then radiates from 12-24 hours from 22 pounds of wood, fired two times a day at a high burn rate. This slow radiating heat follows the design concept of many masonry stoves.  

With a computer combustion control system from sponsor ClearStak LLC and an oxygen lambda sensor from ETAS, operator error decreases so that the owner uses less wood for more heat. This increase in efficiency helps lower the emissions of smoke particulates.

We are looking forward to seeing Intercontinental in action at the Wood Stove Decathlon November 16-19, 2013. Vote for your favorite stove at Popular Mechanics.

“Hello, iStove”: How much can lambda sensor technology improve burning efficiency?

Lambda sensor system (Reprinted from Widmann-Heizungen.it)

The introduction of innovative emissions control technology revolutionized the automobile industry, making cars safer, greener, and more efficient. Now, some boiler manufacturers are saying goodbye to the clunky, soot-filled burners of the past, and are integrating the same lambda sensor devices used in automobile engines into new state-of-the-art clean-burning wood boiler. Economical and carbon-neutral, these eco-friendly lambda heaters could help make wood-burning cool again. Goodbye low efficiency – Hello, iStove.

What is a lambda sensor?
A lambda sensor is a small electronic device that measures how much oxygen is in a gas or liquid. Lambda sensors have been used in a variety of applications since their development in the 1960s – from monitoring breathing in scuba diving to measuring soil oxygen content – but they are most well-known for their use in car emissions control technology. Lambda sensors help cars optimize the fuel combustion process, allowing engines to work as efficiently as possible with the least emissions. In lambda wood heaters, the sensors are used in a similar way to reduce fuel waste and minimize emissions during burning.

How does lambda sensor control work? 
Lambda sensors are key components in the feedback control systems that regulate combustion. Like car engines, wood stoves burn fuel (biomass) in the presence of oxygen. The ratio of air to biomass fuel (“air-to-fuel ratio”) in the stove’s combustion chamber determines how efficient the burning will be. If there is too much air in the chamber, burning will produce high levels of noxious nitrous oxide pollutants. If there is too little air, combustion will be incomplete and the stove will release wasted fuel in the form of hydrocarbon particulates and harmful carbon monoxide gas.

Feedback control fine-tunes the combustion process by varying the air-to-fuel ratio in the chamber so that burning is optimized. A lambda sensor measures the oxygen concentration of the exhaust stream leaving the stove (a measure of how much excess air is in the combustion chamber) and sends the information to a controller or micro-processor, usually as a voltage signal. The controller calculates the current air-to-fuel ratio and varies the amount of air fed into the chamber based on the real-time data from the sensor. These two components working together keep the stove running continuously at near-optimum efficiency, regardless of the species and moisture content of the fuel wood or the boiler temperature.

Lambda boiler manufacturers
Lambda boilers have been on the market since the 1980s, but in recent years more companies are focusing on the residential market and have released newer models featuring upgraded technology and a cleaner aesthetic, including British manufacturers Pevex and Attack, Swedish manufacturer Effecta, and Austria’s Fröling (Effecta and Fröling also distribute to the US). These boilers all boast improved designs and smokeless operation, with running efficiencies often over 90% LHV (normal wood stoves have efficiencies ranging from 60-90%). If lambda control is turned off or is defective, the boilers operate as conventional boilers without the increased efficiency. Prices for the boilers can average about 20% more than non-lambda boilers, typically ranging from $8,000 to $14,000, but often more, depending on model, market and desired energy output. To our knowledge, no wood stove is yet using a Lambda sensor, but it is likely just a matter of time until we see these higher efficiency stoves on the market.