With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
Equipment and products that enable us to use renewable energy instead of fossil fuels and conventional electricity are highly beneficial. Examples include solar thermal systems, solar electric (photovoltaic) systems, and wind turbines. Other power generation equipment, such as fuel cells and some energy storage systems (like batteries) are included here because they help us accommodate varied energy sources so that we may eventually move beyond fossil-fuel dependence.
Travis Industries offers a number of low-emitting pellet stoves under its Avalon and Lopi lines, including the Avalon Arbor and Astoria, and the Lopi AGP and Leyden. These stoves have heating capacities from 800 to 2,200 ft2 areas, and outputs up to 45,000 Btu. The AGP stoves incorporates a Horizontal Rotary Disc pellet delivery system that increases the lifespan of the auger motor and decreases maintenance and the chance of burnback, according to the company. Travis stoves are available with outside air kits, which can improve overall heating efficiency.
Small biomass-burning heating stoves offer environmental pros and cons. Burning locally and sustainably harvested wood or waste biomass, such as sawdust or agricultural-waste pellets, reduces dependence on fossil fuels, but the smoke contains fine particulates (which are lung irritants and asthmagens), as well as polycyclic aromatic hydrocarbons (PACs), dioxins, and other pollutants. When selecting a biomass-burning stove, these emissions are a key consideration.
The most efficient and clean-burning technologies available are catalytic and non-catalytic wood stoves and pellet stoves. Particulate emissions are the primary concern from these heating stoves. The current EPA standards of 7.5 grams per hour (g/hr) for non-catalytic and 4.1 g/hr for catalytic wood stoves have been in place since 1988 and are considered out of date. Even the State of Washington’s 4.5 and 2.4 g/hr standards for these respective stoves are easy for the industry to attain.
The most efficient wood stoves now either use two combustion chambers that create intense heat and fully burn the wood, or use catalytic converters that burn at a lower temperature, eliminate most particulates, and transform combustion gases into water and CO2. Catalytic models create fewer emissions but require platinum or palladium converters that need to be replaced over time; non-catalytic units are relatively simple to operate but are not quite as efficient. Hybrid models combine the best of these technologies.
Pellet stoves burn compressed wood pellets and some can burn other biomass, such as corn. These units typically require electricity for controls, heating elements that ignite the pellets, fans that improve combustion and circulate the heat, and augers that deliver pellets. Some use electronically commutated motors and come with battery backup options for use during power outages. Pellet stoves usually have the lowest emissions of any wood-burning technology, but their use of electricity and noisy fans are downsides.
GreenSpec lists wood stoves that emit less than 1.5 g/hr and pellet stoves that emit less than 1.0 g/hr. Due to their advantages in making our buildings more resilient, we also list pellet stoves that do not require power or come with a battery backup.
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