by Ken Adler, Senior Technical Advisor at the Alliance for Green Heat
Some of you may be wondering about thermoelectric wood stoves and why we decided to include them in the 2018 Wood Stove DesignChallenge
, which will be held in November 2018 on the Washington Mall.
Our goal of this competition is to support development and commercialization of a revolutionary thermoelectric wood stove that produces electricity equal to 50 percent or more of the winter time output of a residential solar photovoltaic system. By combining a thermoelectric wood stove and a residential solar PV system and home battery, like the TESLA Powerwall, we can support residential and grid-based distributive power goals, and incentivize greater investment in solar power.
Specifically, thermoelectric wood stoves can help solve the problem of low winter time solar PV output in northern climates, where useful solar radiation is limited to 2 – 4 hours per day.
While a thermoelectric wood stove may sound revolutionary, the technology behind the stove has been used since the 1980s in oil and gas field operations, where methane gas provides a low-cost source of heat to power the thermoelectric generator. Wood stoves, like waste methane gas, can provide a free source of heat for the thermoelectric generator.
|Alphabet Energy Thermoelectric Generator
Thermoelectric generators are like solar panels, however, instead of turning light into electricity they turn heat into electricity. To generate electricity, one side of a thermoelectric module is heated by the wood stove while the other side is cooled with either an air or water-cooled heat sink. For applications above 100-watts, water-cooled heat sinks are the most common approach because of their ability to extract greater amounts of heat from the thermoelectric module.
|60-Watt Water Cooled Thermoelectric Generator
In northern climates like New England, Canada and northern Europe, low winter time solar radiation increases the cost and reduces the efficiency of solar PV systems, and the cost-effectiveness of battery storage systems like the Tesla Powerwall.
According to NREL, solar radiation in northern areas like Vermont peaks at 6.0kWh/m2 in June and declines to 1.7kWh/m2 in December. This means that an average 4,000-watt residential solar system will go from producing 571kWh in June to 191kWh in December–a 66% reduction is solar power output.
This project will demonstrate how a thermoelectric wood stove can cost-effectively supplement a solar PV system.
Building on our experience from 3 previous Design Challenges, we will work with wood stove manufacturers, universities and others to build and test 100 to 200-watt thermoelectric wood stoves that could effectively increase by 50% the winter time output of a 4,000-watt residential solar PV system.
Thermoelectric generators are currently sold as accessories for wood stoves; however, these accessories are limited in size and efficiency. By integrating a thermoelectric generator into a wood stove we can achieve far greater power output, efficiency, and lower cost. For example, a wood stove with a 150 to 200-watt thermoelectric generator operating 20 hours per day could generate 93 to 124kWh of electricity per month, which compares favorably with the December solar PV output of 191kWh in Vermont.
Russian Thermoelectric Wood Stove
(not certified for sale in the U.S.)
There are several reasons why now is the time to consider thermoelectric wood stoves. First, the price of the thermoelectric modules, which are a component of the TEG, has dropped substantially because they are now being mass produced in China.
Second, the EPA’s recent wood stove NSPS regulation is helping to make new wood stoves cleaner and more efficient and, coupled with cordwood testing and automated features, a new generation of cleaner stoves could also generate electricity. Third, thermoelectric wood stoves can produce electricity up to 24 hours per day eliminating load management concerns common with solar and wind power. Lastly, the stoves are powered by local wood supplies, making their fuel low carbon and locally sourced.
The 2018 competition
on the Mall will demonstrate the role thermoelectric wood stoves can play in promoting solar power, energy storage systems and biomass energy, while also reducing energy costs, supporting climate change goals, and increasing distributive power.
This site contains excerpts from a very crucial and readable report released by the Planet Health Organization (WHO) in 2015.  It is mainly from a wellness and policy perspective and is extremely useful for North American as it provides more of a European point of view and is balanced in its technique. The complete 58-page report can be downloaded listed here.
The report is notably interesting as it hits on a lot of themes that were considered or provided in the 2015 EPA wood heater laws, some of which will be litigated in 2017. It addresses greatest available technologies, indoor air quality, effectiveness specifications, stove changeout programs, black carbon, carbon neutrality, HEPA filters and a lot of other troubles. One of the overarching conclusions is that nationwide policy ought to strongly favor pellet above cord wooden appliances, a changeover that has already happened in elements of Europe, but not in the US.
Authors consist of authorities from the US, Austria, Canada, Finland and Germany.  This publication was prepared by the Joint WHO/United Nations Financial Fee for Europe (UNECE).
The report describes the overall health consequences of and coverage possibilities for working with household heating with wooden and coal in Europe and the United States. The benefits introduced indicate that it will be tough to deal with difficulties with outside air pollution in numerous parts of the globe with out addressing this resource sector. National, regional and nearby administrations, politicians and the community at huge need to have a far better knowing of the position of wood biomass heating as a main resource of harmful outdoor air pollutants (specifically good particles). This report is meant to aid boost these kinds of an comprehending.
Actions are offered to minimize emissions of solid fuels for household heating in most locations. Encouraging gas switching (away from coal and other strong fuels) and use of far more effective heating systems (this kind of as qualified fireplaces or pellet stoves) can lessen the emissions from residential wooden and coal heating gadgets. Educational strategies might also be beneficial equipment to decrease emissions from residential reliable gasoline heaters.
In addition, filters may possibly reduce well being results from indoor air pollution. Present regulatory measures include ecodesign regulations and labels in the European Union (EU) and technological innovation based emission boundaries in the United States of The united states and Canada. Fiscal gas switching and technological innovation changeout incentives – as well as specific “no burn” times and ecolabelling – are other equipment accessible to plan-makers.
p. two. Household heating with wood is a sector in which PM2.5 and BC emissions can potentially be decreased with higher cost– efficiency than several other emission reduction possibilities. Even so, in Europe and North The usa only a handful of nations or states have established legal boundaries for minimal combustion effectiveness or greatest emissions of PM and damaging gaseous compounds like CO and gaseous natural compounds (see part six).
p. eight. In the United states fifty five% of properties employed coal/coke for room heating in 1940, but this fell to 12% in 1960, beneath five% in the early seventies and below one% from the early nineteen eighties (Schipper et al., 1985 United States Census Bureau, 2011).
A single review estimates that reductions in the use of bituminous coal for heating in the United states of america from 1945–1960 reduced winter all-age mortality by one% and wintertime infant mortality by 3%, preserving virtually 2000 life for each wintertime month, including 310 toddler lives (Barreca et al., 2014).
Primarily based on this and proof that indoor emissions from family combustion of coal are carcinogenic to human beings, the latest WHO indoor air top quality tips strongly advise in opposition to the household use of unprocessed or uncooked coal, such as for heating (WHO, 2014a).
Infiltration of smoke into homes
p. 10. A home with wood-burning appliances is likely to be surrounded by other homes with wood-burning appliances, and wooden burning also tends to combination temporally as a result, on cold evenings and evenings most residences in the region may possibly be burning wood.
Presented that most wooden burning occurs in cold places exactly where homes are properly insulated, properties are predicted to have lower infiltration (which means that comparatively modest quantities of out of doors air pollution, such as wooden-burning smoke, enter the property and contribute to indoor air pollution), specially in the course of the heating year.
In North The usa heating-time outside temperature is an critical determinant of infiltration, and infiltration ranges are usually lower in the heating than the non-heating time, when doorways and windows are probably to be open a lot more (Allen et al., 2012). In British Columbia the mean infiltration portion of PM2.5 in winter was located to be .28, when compared to .61 in summer, although infiltration factors for person properties in winter season ranged from .1–0.6 (Barn et al., 2008) yet another research reported in the same way reduced mean infiltration stages of .32 Å}.17 throughout the winter season (Allen et al., 2009). Combustion of wood in residential areas and frequently beneath cold, calm meteorological circumstances can even so lead to substantial publicity compared to other air pollution sources, owing to the principle of ingestion fraction.
Modern wooden stoves and fireplaces, when operated according to the manufacturers’ directions, release some PM and gaseous pollutants directly into indoor air, although in most instances the proof for considerable indoor emissions from these modern day stoves is quite minimal. With poor procedure, very poor air flow or backdrafting, even so, elevated concentrations of combustion items (such as PM, CO, VOCs, NOx and aldehydes) may possibly consequence indoors. Acute CO poisoning, which can at times even be fatal, may possibly happen thanks to indoor wood burning and infiltration of filthy ambient air), specifically when air flow of the wood-burning appliance is not managed effectively.
p. 21. This sort of modify-out initiatives have likely constraints. The Canadian Council of Ministers of the Surroundings (CCME) – the association of atmosphere ministers from the federal, provincial and territorial governments – evaluated twelve stove exchange and instructional initiatives carried out in Canada and concluded that exchange programmes could have limits relating to equally the expense of new technologies and the lengthy services existence of appliances when set up. The evaluation supported the use of regulation effectively to curb the sale of large-emission appliances. This method is utilised in a quantity of Canadian provinces and American states.
The Canadian National Collaborating Centre for Environmental Well being discovered that emissions standards (based mostly on greatest offered systems) are essential to ensure that the newer units put in by way of alter-out programmes are amid the cleanest offered in the marketplace. Without these requirements, alter-out programmes may, in truth, be dropped possibilities to set up the cleanest obtainable wooden-burning units, which will be in use for a long time to come.
The examine also located that removal of traditional noncertified appliances (through exchanges, time limits or prior to the sale or transfer of a house) was the most powerful approach provided in a model municipal by-law for mitigation of household wood smoke (Setting Canada, 2006) (see “Other rules and voluntary measures” in area 6). [Click for much more on stove alter out packages – editor.]
Although family or individual-amount methods are not typically element of air good quality administration programmes, two studies from Canada show that inhome HEPA filtration might lessen overall health impacts from wooden smoke. An first solitary-blind randomized crossover study of 21 homes during winter season, in an location afflicted by household wood combustion as properly as site visitors and industrial sources, reported a suggest 55% (normal deviation = 38%) reduction in indoor PM stages when HEPA filters were operated (Barn et al., 2008). Use of the HEPA filters reduced indoor PM2.5 and levoglucosan concentrations by 60% and seventy five%, respectively. [Click for much more on HEPA filters – editor.]
Regulatory Emission Limitations
p. 26. Over the past 10 years, the European Commission has worked in the direction of the possibility of regulating strong fuel local space heaters and boilers, especially individuals that use different types of woody biomass gas (wood logs, pellets and biomass bricks), to produce proposed ecodesign emissions restrictions.
According to the Commission proposals, implementation of ecodesign specifications would lead to significant reductions of PM2.5 emissions from solid gas regional place heaters and boilers compared to baseline projections. The draft regulation for sound fuel local room heaters2 states that in 2030 the proposed demands for individuals merchandise, combined with the influence of the energy labelling, are anticipated to conserve about forty one petajoules (.nine million tonnes of oil equivalent (Mtoe)) per yr, corresponding to .four million tonnes of CO2. They are also envisioned to reduce
PM emissions by 27 kilotonnes per yr,
p. thirty. The Wood Stove Decathlon, an initiative of the Alliance for Environmentally friendly Heat, was structured in 2013 to emphasis creativeness and methods on planning subsequent generation wood stoves. The principal purpose was to problem groups of combustion engineers, engineering pupils, inventors and stove makers to construct wooden stoves that are low-emission, large-efficiency, revolutionary and inexpensive, in a common approach that may possibly position to commercially desirable up coming generation stove manufacturing (Alliance for Environmentally friendly Heat, 2013).
p. 31 Any renewable power or local weather modify relevant policies that assist combustion of wooden for residential heating want to take into account the local and global ambient air pollution impacts and quickly advertise the use of only the most affordable emission or ideal obtainable combustion technologies.
Lawful rules for wood combustion effectiveness in new heating appliances are urgently necessary during the globe. These will each sluggish down the present quick pace of worldwide warming (relating to BC in good particles and VOCs that market ozone formation) and minimize the great load of condition triggered by wood combustion-derived particles (especially organic compounds carried by BC). Such rules ought to incorporate tight – but technically achievable – boundaries in distinct for the main emissions of particulate mass, gaseous hydrocarbons and CO from new boilers and heaters.
p. 32. As new wood-burning units turn out to be far more vitality effective and emit less air pollution (specifically PM), nationwide governments require to prepare heater exchange regulations or voluntary programmes. Municipalities, counties and states need to take into account demanding heater exchanges at the time of residence remodels or product sales. In many instances, these laws will be most profitable if monetary compensation is provided to support with the cost of changing aged heaters with these assembly restricted strength effectiveness or emission boundaries regulations.
“No burn” regions are necessary. Particularly with recent combustion technologies, it is crucial to determine urban places with dense populations and/or geographical features (such as valleys amongst mountains) where household heating or cooking with tiny-scale appliances burning reliable fuels (wood and coal) is not permitted at all or is at the very least minimal to registered versions of reduced-emission wood combustion devices. Residential heating with coal in little-scale appliances must also be completely prohibited, at least in communities of developed international locations, as need to the use of wood log burners for central heating with out a sufficiently large water tank (which or else qualified prospects to poorly incomplete combustion and extremely huge emissions).
Co-rewards for health and local climate
As wood is burned … carbon is unveiled back to the ambiance, not only as CO2 but in most household combustion also in the kind of quick-lived greenhouse pollutants this sort of as BC, CO and VOCs like CH4. Thus, to be completely “carbon neutral”, wooden gas has to be not only harvested renewably but also combusted completely to CO2. For both local weather and wellness needs, the type these fuels’ carbon requires when it is introduced matters greatly, given that BC and CH4 are both strongly local weather-warming.
p. 34. A Planet Lender review located that changing recent wooden stoves and household boilers used for heating with pellet stoves and boilers and replacing chunk coal fuel with coal briquettes (mainly in jap Europe and China) could supply significant local climate positive aspects.
One more study coordinated by the United Nations Surroundings Programme and the Entire world Meteorological Group identified that prevalent dissemination of pellet stoves (in industrialized nations) could increase overall health, since these interventions lead to reductions in PM2.5.
If Arctic weather change turns into a emphasis of specific mitigation action (due to the fact of threats from climbing sea amounts, for case in point), popular dissemination of pellet stoves and coal briquettes may possibly warrant further thought simply because of their disproportional reward to mitigating warming from BC deposition in the Arctic (UNEP & WMO, 2011). The World Bank found that substitute of wood logs with pellets in European stoves could direct to a fifteen% better cooling in the Arctic (about .1 ÅãC). For Arctic nations the modeling strongly suggests that the most successful
BC reduction actions would target regional heating stoves for equally local weather and well being advantages (Pearson et al., 2013).
p. 35. Given that household wood combustion for heating will continue in a lot of areas of the planet simply because of financial concerns and availability of other fuels, an urgent want exists to build and encourage the use of the lowest emission or ideal accessible combustion systems.
It might be preferable in a lot of cases to target on making biomass-based residence heating much more successful and significantly less polluting rather than transitioning away from biomass to fossil fuels, presented the weather change implications of using fossil gas for heating.
The 2014 Winter Fuel Outlook released by the US Energy Information Agency on Oct. 7, predicted that wood and pellet heating would continue the trend of being the nation’s fasting growing heat source. Overall, wood and pellet heating grew 38% from 2004 to 2013, and now accounts for 2.5% of all home primary heating. The […]