West Penn Power Energy Fund to support a design competition that pairs automated, electricity producing wood stoves with solar PV

For immediate release

June 27, 2018- The Alliance for Green Heat received a $5,000 grant from West Penn Power Sustainable Energy Fund (WPPSEF) to support the 2018  Wood Stove Design Challenge, a competition to automate and make electricity from wood stoves from November 9 - 13.

The grant funds will be used to test and promote stoves that are automated and produce electricity, both of which could be popular in Western Pennsylvania as they become more commercially available in the next few years. Twelve teams are competing and they will be rigorously tested for emissions, efficiency, electricity output and other qualities.,

Automated wood stoves can enable consumers to “load and leave” and get a high efficiency clean burn through sensors that can adjust by the minute and are far more effective than a human operator. Electricity producing stoves can recharge cell phones, power light bulbs in the event of a short or longer power outage caused by storms, grid failure or any other reason.  Within 3 – 5 years, electricity producing wood stoves may also be a more common option in the northern US to complement low wintertime solar PV output. In the future, thermoelectric wood stoves may be able to produce half as much electricity as a residential solar PV installation in December and January in northern states.

Wood is a popular residential heating source in Pennsylvania. According to the latest Census figures, Pennsylvania has the highest number of households heating with wood outside New York and California. Approximately 3% of all homes in the Commonwealth use wood as a primary heating source, but in 16 counties, 10% or more of households use wood or pellets as a primary heat source according to the US Census: Fulton (20%), Sullivan (20%), Juniata  (19%), Forest (16%),  Potter (16%), Tioga (15%), Susquehanna (15%) and Bradford (14%), Bedford, (13%), Huntington (13%), Mifflin (13%), Perry (13%), Crawford (11%),Wayne (11%) and Warren (10%).  More than half a million Pennsylvanians use it as a primary or secondary heat source.  

“Woody biomass is an abundant renewable heat feedstock which has been used by generations to provide low-cost heating for homes across Pennsylvania.  WPPSEF seeks to better understand how modern, innovative wood stoves can affordably help meet energy needs while operating far more cleanly than traditional wood stoves,” says Joel Morrison, Director of the WPPSEF.

The Alliance for Green Heat promotes modern wood and pellet heating systems as a low-carbon, sustainable and affordable energy solution. The Alliance works to advance cleaner and more efficient residential heating technology. The Wood Stove Design Challenge in November 2018 will the fourth Design Challenge hosted by the Alliance for Green Heat. Founded in 2009, the Alliance is an independent non-profit organization and is tax-exempt under section 501c3 of the tax code. 

The West Penn Power Sustainable Energy Fund (WPPSEF) is a 501(c)(3) nonprofit organization that invests in the deployment of sustainable energy technologies that benefit West Penn Power ratepayers in Pennsylvania. WPPSEF investments are focused in three broad categories:

✓     Deployment of sustainable and clean energy technologies; 

✓     Deployment of energy efficiency and conservation technologies; and 

✓     Facilitating economic development, environmental betterment, and public education as they relate to sustainable energy deployment in the WPP service region.

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Visit http://www.wppsef.orgfor further information.

Contact John Ackerly, 

Alliance for Green Heat, 301-204-9562
jackerly@forgreenheat.org

Contact Barbara Robuck, 

West Penn Power Sustainable
Energy Fund, 814-865-7380
wppsef@ems.psu.edu

Bill McGrath: A pioneer in making electricity from a pellet boiler

Bill McGrath

In 2007, Bill McGrath built a thermoelectric pellet boiler that heated his home for almost 10 years. The story, however, starts in 1998, when Bill and a group of other students at Vermont Technical College entered the “American Tour de Sol” Solar Challenge, a solar car competition sponsored by DOE, not unlike the Wood Stove Design Challenge. The competition taught him about solid state technologies and the important role DOE competitions can play in promoting innovation. 

Building on his own experience and Shuji Nakamura’s discovery of commercially viable LED lighting, Bill helped start LEDdynamics in 2000, an LED circuit and lighting manufacturer. However, in the back of his mind he was also thinking about how thermoelectric generators (TEGs--pronounced T-E-G, like L-E-D) could solve a major problem with pellet stoves and boilers: when the electricity goes out, unless you have a big battery or generator, the pellet stove stops operating.

Bill and his colleagues made the TEG powered pellet boiler from an old oil boiler, a washing machine and other various knickknacks. McGrath recalls turning the fire chamber of the old oil burner into a pellet stove, using metal cat food dishes from the dollar store as burn pans, and using an old washing machine as the hopper by shaping it into a funnel that connected to a DC auger that fed the pellets into the burn pans. The hot water coming from the boiler heated one side of the thermoelectric modules, while the cool water that circulated through the home’s radiator system cooled the other side of the modules. This temperature differential (known as the Seebeck effect) generated the electricity to power the auger, blowers and water pump for the heating system.  The thermoelectric pellet boiler produced up to 60 watts and kept him and his family warm for over 9 years, even during power outages. One goal of the Design Challenge is to improve on Bill’s TEG boiler so that a thermoelectric wood stove or boiler can produce substantially more electricity to help power lights, recharge batteries and augment solar power.

After 9 years of heating Bill's home and
making its own electricity, the home-
made boiler came out of the basement.

In 2013, Bill and his team created a thermoelectric energy generation division at LEDdynamics called TEGpro to share their expertise with everyone from large multinational corporations to small inventors. Surprisingly, the division has found many opportunities for their thermoelectric technologies’ in the petroleum and gas industry. With miles of piping, this industry has a large demand for TEG powered pressure sensors and wireless devices that measure liquid and gaseous chemicals and fuels as they move through the pipeline.  TEGpro is working with the petroleum and gas industry as an “intermediate step” until they can fund projects that hold larger implications for growth in thermoelectric wood and pellet stoves and boilers. 

TEGpro’s customers are already demonstrating the advantages of thermoelectric technology in residential applications across the world. For example, Bill references many instances of users in Alaska and Canada transferring wood stove heat through their cabins by putting TEGs on their central boiler systems, providing them a critical source of electricity without having to use a generator. 

Bill expects TEGs’ trajectory to be like what he experienced with the rise of LEDs since his start at LEDdynamics. Today’s modern LED light was discovered by Shuji Nakamura in 1994, who received the 2014 Nobel prize in physics for his work. Like the pre-Nakamura LEDs, Bill recognizes that the cost and efficiency of thermoelectric generators remains a challenge, but he believes that thermoelectrics will become as commonplace as LEDs.  With events like the Wood Stove Design Challenge, he is optimistic for the future of TEG power generation. However, commercializing energy alternatives like LED lights and solar power needs support from government agencies like DOE to fund the university research and competitions that can make TEGs as common as LEDs.

Could a Thermoelectric Wood Stove Pay for Itself?

By Ken Adler, AGH Senior Technical Advisor

Payback calculations are common in the residential solar photovoltaic industry where homeowners want to know how long it will take for them to recoup their initial investment. If you purchase panels outright, payback periods depend on a variety of factors including a utility’s price for electricity, tax incentives, and amount of daily sunlight hours. A range of 5 to 8 years is possible however, it can be as wide as 3 to 15 years.[1]

Answering the payback question for thermoelectric wood stoves is one of the objectives for the 2018 Wood Stove Design Challenge. In the meantime, there are several ways to begin answering this question with information already available. It is also useful to look at how use of a thermoelectric wood stove in combination with another energy-saving system, i.e., solar, could prove beneficial to the homeowner and thus both industries as well. For example, in northern states and Canada, a thermoelectric wood stove could reduce the number of residential panels needed and thereby save the homeowner thousands of dollars in panel costs.

Early Thoughts on Payback

The retail price of a thermoelectric module is around $57.50 for a 22-watt module, or $2.61 per watt.[2] One critical point to make here is that the power output of our 22-watt module assumes an optimal hot-side temperature of 300 C (572 F) and cool-side temperature of 30 C (86 F). This ideal temperature differential is very difficult to achieve in real world conditions, so the real-world cost per watt for thermoelectric modules will be higher. However, cost should decrease and efficiency improve with widespread adoption of thermoelectric modules, similar to what happened in the solar industry. For example, DOE estimated that the installed cost of a solar panel declined from $7.06 per watt in 2009 to $2.93 in 2016, a reduction of 60 percent.[3] If we go back to 1977, the cost of a solar panel was $77 per watt. It is not unreasonable to expect a decline for the cost of thermoelectric modules as economies of scale reduce production costs.

Of course, when a thermoelectric module is placed into a wood stove there are other associated costs. The primary cost by far is the heat exchange system. As I’ve discussed in a previous post, to generate at least 100 watts of power, it’s likely that a water-cooled heat exchange will be needed. The current retail price for a 100-watt water cooled thermoelectric generator, which includes eight thermoelectric modules, is $599, or $5.99 per watt. One question the competition will attempt to answer is how much this heat exchange will cost when it is integrated into the design of the wood stove.

Secondary cost considerations include the price of the wood stove, its installation, and fuel costs. The price for a larger size 50,000 BTU wood stove can range from $900 to over $4000, and the average consumer spends about $2,500. Since a thermoelectric wood stove would be providing both heat and electricity, it is difficult to separate out how much of the cost of the stove is for each function. The more crucial point for now is that many larger size stoves, which can generate up to 50,000 BTUs and meet the 2020 EPA NSPS standard, are available for as little as $1,300. While this does not include the cost of installation, it does suggest that the wood stove portion of the costs should not be a major obstacle.

The cost of installing a thermoelectric wood stove into a home should not necessarily be that much greater than the cost of installing a traditional wood stove. One additional cost will be attaching the power outputs from the thermoelectric wood stove to an inverter. However, if we assume that early adopters will already have or are planning to get a solar PV system (more on this below) the cost of the inverter would not be a major obstacle.

Finally, one can assume that the fuel cost for a thermoelectric wood stove is essentially zero because the wood stove is already being used to heat the home. A thermoelectric module will convert only 3 to 6 percent of the heat from a woodstove into electricity, while the remaining 94 to 97 percent passes through the module and is released as heat into the home. In other words, the module is only using a very small percentage of the heat generated by the stove to produce electricity.

Value in Combining Technologies

While more in-depth analysis is needed, it’s possible that a thermoelectric wood stove could help reduce the size and cost of solar PV systems in northern climates that have limited sunlight/solar radiation in winter. For example, a typical 5000 watt solar PV system in Vermont produces 6,280 kWh of electricity per year, while the same system produces 7,913 kWh in Los Angeles.[4] Most of this difference is due to the low winter time output in Vermont between October and February: For example, the Vermont system produces 239 kWh in December, as compared to the Los Angeles system’s 473 kWh. If the Vermont resident wanted to generate the same amount of power as in Los Angeles, they would need to increase the size of their solar PV system from 5000 watts to approximately 6300 watts. At the current cost of approximately $3.36[5] per watt installed for residential solar, this could cost the Vermont resident an additional $4,368 for additional solar panels.

Alternatively, instead of purchasing extra solar panels, the Vermont resident could invest in a thermoelectric wood stove to boost their winter time power output. As we mentioned in our previous blog, a wood stove with a 150 to 200-watt thermoelectric generator operating 16 - 20 hours per day could generate 93 to 124kWh of electricity per month, which would be a good boost to the Vermont output of 239 kWh in December. And, at 0.16 $/kWh for electricity in Vermont, the thermoelectric wood stove could save the homeowner an additional $15 to $20 per month.

While a real payback calculation for a thermoelectric wood stove will need to wait until prototypes go through more testing and we get results from the 2018 Wood Stove Design Challenge, the available information suggests thermoelectric wood stoves could help reduce the cost of residential solar installations, and potentially save homeowners thousands of dollars.


[1] http://solar-power-now.com/the-typical-solar-panel-payback-period/
[2] See our Resources page for a list of thermoelectric retailers.
[3] NREL. U.S. Solar Photovoltaic System Cost Benchmark. September 2016. In 1977, solar panels cost $77 per watt.
[4] NREL PVWatts Calculator
[5] EnergySage. Solar Marketplace Intel Report. April 2017.

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Hybrid Residential Solar and Thermoelectric Power Generation

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.[1]  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.   

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[1] The cost of a thermoelectric module has fallen below $2 per watt (uninstalled), compared with $3.50 per watt for solar panels (installed).