|Glenn Robinson is one
of many retailers struggling
to help consumers avoid
relying on manufacturer
claims about BTU output.
|AGH tested six popular pellet stoves.
Almost all performed well during
intensive 30 day testing, but did not
live up to some manufacturer claims.
Guest Blog: We are reposting a 2012 blog from Instructables by Tecwyn Twmffatt at Goat Industries. It describes an early effort to build a thermoelectric wood stove. This blog is part of a series of blogs providing information for the 2018 Wood Stove Design Challenge.
Introduction: Thermoelectric Power Generation (TEG)
Step 1: Part 2 of 3
A ten unit Thermoelectric generator system is shown being constructed and then fitted to a wood burner. The theoretical maximum output is 200 watts. The video shows how the generator was put together and how the wood burner was modified to get maximum heat through the TEGs. The TEGs themselves are able to withstand a constant 325 degrees C on the hot side and require plenty of heat to get the 20 watts that each of them are capable of producing.
Step 2: Part 3 of 3
In part 3 we successfully generate a significant amount of energy from the woodburning stove. In the first session, a circulation pump, a fan and 10 x 10 watt flood lights are powered up. In the second session, we attempt to get a more balanced load wired up to the tegs and measure a noticable increase in power output. The 10 tegs are wired up in 2 parallel strings and, from the manufacturer's specification, the optimum output voltage is 14.4v . The nearest that we manage is 13.8v, at which we generate 120 watts. The specifications suggest that 200 watts is possible when the load is matched.
Step 3: Full Playlist
31 Minutes of Thermoelectric video heaven!
Step 4: Creating the 1 TEG Generator
Here we are going to build the single TEG generator shown in the first video.
Step 5: Tools and Equipment
Parts: Thermoelectric power generator TEG module (GM250 449 )
...... buy direct from China at: www.thermonamic.com/
Aluminium block 102 x 115 x 20 mm
Steel block 102 x 115 x 10 mm
1/4" BSP blanks x 6 of
1/4" BSP male stud push fit pneumatic fittings for 10 mm pipe x 2 of (See photo above)
5 mm Hex bolts x 40 mm x 2 of
25 litre water butt
OD 10 mm ID 8 mm nylon pneumatic pipe
12V water pump
12V LEDs, 1 watt x 20 of Tools: 1/4" threading tap
5 mm metric coarse threading tap
Drill 11.5 mm
Drill 5.5 mm
Drill 4.2 mm
Plasma cutter / Grinder with cutting discs
Step 6: Drilling and Tapping the Cooling Block
Use the engineering drawing to produce internal coolant passage ways in the aluminium block. I ended up drilling all the way through to the other side and using more of the 1/4" blanks. Connect the 1/4" pipe fittings to the block and plumb in the pump. Add antifreeze to the water in the water butt if it's likely to get cold at all. To create a 'sandwich' with the hot block (steel block), the TEG and the cooling block, drill and tap holes in the steel block for the 5mm bolts. Weld the hot block into the side of the wood burner and recreate the TEG sandwich, tightening the bolts up with a torque wrench (see attached file). Connect up LEDs on the TEG, turn on the pump, light the wood burner and off you go!
Step 7: 10 TEG Layout
If you really must build the 10 TEG generator, the photo above shows what is involved. I have got CAD drawings, PCB drawings etc. If anybody is interested. Not for the faint hearted! PCB 03.pcb
CAD files 02.zip Heated Up!
Left to right: Mark Champion (in his
VT test lab), Boris Kukolj (Tulikivi),
Chris Prior (MHA President), Norbert
Senf (blog author) and Jean Francois
Vachon (soapstone supplier).
Photo credit: Mark Seymour.
EPA started regulating wood burning stoves for particulate (PM) emissions in 1988. Regulation was limited to airtight heating stoves. Masonry heaters were not regulated, the stated reason being that they were likely to be clean burning.
|The late Paul Tiegs, one of the
greatest authorities on wood
stoves, conducted the
interviews for the EPA.
|John Crouch, HPBA’s
foremost wood stove expert.
John Crouch, HPBA: I wouldn’t use the term “close the loop-hole”. I would say, “is the proper place to cut off the definition of a wood heater?” We all know the whole discussion during the Reg-Neg ignored this emerging category of pellet stoves. So this gets back into my other broader comment, which is, instead of going back in and changing the NSPS in a piecemeal fashion, there needs to be a true revision of the whole thing that deals with the category of pellets and masonry heaters and outdoor furnaces.
Rick Curkeet, Intertek: Yes. The way to amend the regulation is to simply remove the 35:1 air/fuel ratio exemption. This has never been required by fireplaces (they meet the 5 kg/hr minimum burn rate exemption criterion anyway). Pellet units are readily able to meet emissions requirements and the exemption only encourages making these units less efficient to avoid the regulation.
Bob Ferguson, Consultant: The 35:1 cutoff was intended for fireplaces. However, pellet stoves are the only product that even take advantage of the air-fuel exemptions. Fireplaces generally use the burn rate exemption. Pellet stoves probably don’t need to be regulated at all. They are all quite clean burning. Let the marketplace decide if exempt stoves are acceptable. If pellet stove users demand products that use fewer pellets (more efficient), the manufacturers will respond.
Skip Hayden, Researcher: Yes. In Canada, we recommend that people buy only EPA-approved pellet stoves. We have developed a high ash pellet stove that’s operating around 85% and its emissions are about 0.3 g/hr or less.
|Dan Henry, a founder of Quadrafire
stoves is one of industry’s most
Dan Henry, Aladdin: There is no data that indicates that even a poorly operating stove is a dirty burning appliance. They are inherently clean, becoming more and more reliable, and don’t fix them if they aren’t broken.
Dennis Jaasma, University of VA: Pellet stoves are inherently clean burning unless there is something very bad about their design. I am not concerned about regulating the currently uncertified units unless their field emissions are bad compared to certified stoves.
Robert C. McCrillis, EPA: Yes, all pellet stoves should be affected facilities and not subjected to that 35:1.
|Ben Myren one of Amreica’s most
thoughtful and experienced stove tester.
Ben Myren, Myren Labs: I agree, no more loop-holes. The new technology stoves that are coming on the market are going to be totally new critters. I don’t think that turning down the air- to-fuel ratio, to make it whatever it is, should get you out of the loop. Some of those suckers have got to be just filthy. I mean you look at the flame. I’ve seen them burn at the trade show; you know, the glass is sooting up on the edges. You can just see it.
|Michael van Buren was a technical
expert with The Hearth Products
Association, now HPBA
Michael Van Buren, HPBA: I don’t know what that loop-hole does, whether it really affects the operation of the stove and the efficiency of the stove.
Question: According to a Department of Energy survey out of the 20.4 million households that used a wood burning appliance in 1993, less than 0.3 million used a wood burning furnace as their primary source of heat. Are there enough wood-fired central heating furnaces in use to merit their closer evaluation? How many commercially available models are there? Are there emissions data for them? Should they be certified?
John Crouch: The  EPA New Source Performance Standards killed the indoor furnace industry and created this little loop-hole which the outdoor furnace industry is beginning to exploit and kind of underscores the need for a more comprehensive wood burning regulation which sets out over a several year period to codify all forms of wood burning technology.
|Rick Curkeet tested stoves for Intertek
labs and is one of industry’s top experts.
Rick Curkeet: I don’t know how many new units are being produced but I’m sure it’s a very small number. Still, one really poor unit can be a significant problem if it’s in your neighborhood. There have never been any standards for testing this type of product for emissions and efficiency. However, we have adapted existing methods and can say that the performance range is very wide. Poor designs may be 30% or less efficient and produce nearly 100 grams/hr emissions rates. Good designs are able to approach certified wood stove performance levels.
Bob Ferguson: I don’t feel there are enough units being sold to merit any activity what-so-ever. There are only a handful of manufacturers. I don’t think there has been anything published–so if testing has been conducted, it is probably a good assumption that the numbers aren’t that good. They shouldn’t be certified, as you would have to develop test methods and standards. The country would be better off using the money to pay manufacturers to phase out of production, sort of like the agricultural method of paying farmers not to grow certain crops.
|The late Skip Hayden, one of the main
wood stove authorities during the 1980s
Skip Hayden: The number of central wood furnaces in Canada, certainly in comparison to the United States, would be higher. In our Eastern provinces, it’s a relatively common add-on to existing oil furnaces. Generally, they are as dirty as can be.
Dan Henry: I think a lot of these are used in rural areas and considering the fuels that are out there, I don’t think they should be regulated. Maybe just a spot check of some sort. I think the only thing that would benefit would be the testing laboratories. If it emits particulate into an air shed where it can have an adverse effect on the industry (my ability to make a living), then yes.
also ran a research
test lab at the
University of VA.
Dennis Jaasma: Yes, central heaters merit further evaluation. I don’t know how many models are available. I think EPA has done some work on them, but I do not know any results. Yes, they should be certified. They are in danger of becoming extinct if they don’t wind up with a certification program.
Robert C. McCrillis: In some localities I think these furnaces are a problem; I don’t know how many are commercially available. I think I can name off six or eight companies and each one makes several models, but I don’t know what the total market is, maybe 10,000 – 15,000 a year. The little bit of testing that we did here, says that they are probably on a par with a conventional wood stove. The way those things work, they have a thermostatically operated draft and when the thermostat shuts off the draft closes, so you get this real smoldering burning situation. Secondary combustion technology probably wouldn’t work. Possibly a catalytic technology would, but I just don’t think it stays hot enough in there. I guess that really depends on the impact.
Ben Myren: I don’t think they should be exempt for any reason. As to the rest of it–are there emissions data for them? I suspect there are. Should they be certified? Yes they should be certified. Nobody should be exempt from the process.
Michael van Buren: I think there should be some type of testing on them.
- 1.1 Are in-home emission reductions as compared to conventional stoves shown in Table 1 for catalytic and non-catalytic certified stoves reasonable?
- 1.2 Are efficiencies shown in Table 2 for catalytic and non-catalytic certified stoves reasonable?
- 1.3 Can catalytic technology for use in wood stoves be fundamentally improved?
- 1.4 Is the use of manufactured fuel (densified and wax logs) a credible emission
- 1.5 For non-catalytic stoves the heat retention adjustment with refractory material of various densities can reduce particulate emissions. How big an effect can this have?
- 1.6 Approximately one half of the particulate emissions occur during the kindling phase for non-catalytic wood stoves and more than half for catalytic wood stoves. Are there improvements in technology that can mitigate this problem? Can specially designed high BTU wax logs be used to achieve a fast start and reduce kindling phase emissions?
- 1.7 Should masonry heaters with tight fitting doors and draft control be classified as a wood stove and be subject to some type of certification even though most weigh more than 800 kg?
- 1.8 Are the emissions and efficiencies for masonry heaters, based on in-home tests, shown in Tables 1 and 2 reasonable?
- 1.9 The OMNI staff feels the emissions per unit of heat delivered (e.g., lb/MBTU or g/MJ) is a more appropriate way to rank the performance of wood burning appliances than emission factors (lb/ton or g/kg) or emission rates (g/hr). — Comments?
- 1.10 Default efficiency values are used for wood stoves. This coupled with the fact that emission factors or rates (not g/MJ) are used to rank wood stoves does not provide an incentive for manufacturers to increase the efficiency of their stoves. — Comments? Should an efficiency test method as described (FR v. 55, n 161, p. 33925, Aug. 20,1990) be required to be used and the results listed?
- 1.11 Have certified stove design and performance improved since the first certified stoves? If so, how?
- State-of-the-art of fireplace emission control technology.
- 2.1 Are the emission factors and efficiencies for the in-home use of fireplaces and inserts shown in Tables 3 and 4 reasonable?
- 2.2 There appear to be only a few practical design or technology options for fireplaces that will potentially mitigate particulate emissions. — What designs and technologies are available? What retrofit options are there?
- 2.3 The use of wax fire logs reduces emissions over the use of cordwood. Can the formulation of wax logs be changed to produce even less emissions?
- 2.4 What are the distinctions between a masonry fireplace and a masonry heater?
- 2.5 As with wood stoves, the OMNI staff believe that the mass of emissions per unit of heat delivered is a better way to rank the performance of fireplaces than emission factors or emission rates.
- State-of-the-art of wood-fired central heating furnace emission control technology.
- 4.1 Are the emissions and efficiencies for the in-home use of pellet stoves shown in Tables 1 and 2 reasonable?
- 4.2 The 35:1 air-to-fuel ratio cut-off for certification has produced two classes of pellet stoves — those that are certified and those that are not. The latter class may have models that are less efficient and have higher emissions than the former. Should the regulations be amended to close the loop-hole and discourage the practice of intentionally designing models with a higher air-to-fuel ratio to avoid certification?
- 4.3 Have pellet stove design and performance improved since the first models were introduced? If so, how?
- Correspondence between in-home and laboratory emission test results.
- 6.1 How accurately do certification tests predict in-home performance?
- 6.2 How would you design research testing in the laboratory to simulate in-home use?
- EPA Method 28 strengths and weaknesses.
- 7.1 Method 28 is in part an “art”. Fuel loading density, fuel moisture, fuel characteristics (old vs new growth, grain spacing, wood density) and coal bed conditioning can be adjusted within the specification range of the method to influence results. In your experience what things have the most effect on particulate emissions? How much influence can they have?
- 7.2 Burn rate weighting is based on very limited data and the cities from where the data were obtained are not very representative of wood use nationwide (see Table 6). How can the weighting scheme be improved to be more representative of the nation as a whole?
- 7.3 The equation for the calculation of the air-to-fuel ratio as in Method 28A is in error. The error produces a small but significant difference in the calculated air-to-fuel ratio. Should the method be corrected or should it be left as a “predictor” of the air-to-fuel ratio?
- Performance deterioration of EPA-certified wood stoves in the field.
- 9.1 It is the opinion of many in the wood stove industry that catalysts last only five years and that a stove designed for a catalyst operated without a functioning catalyst can produce as much emissions as a conventional stove. — Comments?
- 9.2 Field studies in Glens Falls, NY, Medford, OR, Klamath Falls, OR and Crested Butte, CO showed that emissions from some catalytic stoves became appreciably worse even after two to three years of use. Inspection of stoves in Glens Falls showed that catalyst deterioration and leaky bypass systems were responsible. Have improvements been made in the design of catalytic stoves to minimize these problems? Is it reasonable to require homeowner training on the proper use of catalytic stoves and/or to incorporate into their costs an inspection and catalyst replacement program?
- Stress test pros and cons.
- 10.1 A short-term laboratory woodstove durability testing protocol was developed to predict the long-term durability of stoves under conditions characteristic of in- home use (see EPA-600/R-94-193). It was concluded in that study that damage occurs during those occasional times when a woodstove is operated in the home at exceptionally high temperatures. The laboratory stress test was designed to operate a woodstove at very high temperatures over a one to two week period to predict long-term durability under in-home use. Is this a reasonable approach?
- 10.2 Should a stress test be made part of the certification process?
- Feasibility of developing separate emission factors for dry and wet wood and for
- 11.1 Optimum wood moisture for low particulate emissions seems to be in the 18% to 20% range. Are you aware of any data that will allow the impact of wood moisture to be isolated from other variables? Could it be different for wood from different tree species?
- 11.2 Wood from different tree species clearly burns differently. The chemical make-up and density of wood from different tree species is different. For example wood from coniferous trees has more resin than wood from deciduous trees. It is believed that particulate emission factors will be different for wood from different tree species. If this is true different parts of the country may have different emissions factors for residential wood combustion. Are you aware of any data that document different emission factors for wood from different tree species?
- 12.2 Should the home owner be provided with a maintenance manual or a training course at the time of purchase? Should a maintenance program be part of the purchase price particularly for catalytic stoves?
- 12.3 What would the key elements of routine maintenance be?
Rod Tinnemore became an Environmental Planner at the Department of Ecology in 2008, years after the state was pummeled by industry for the audacious move of requiring all heaters to meet a standard of 4.5 grams of particulate per hour. Rod became the guy who enforced that decision, and it was one he was happy to enforce, because he felt stoves could and should be required to burn cleaner than the federal standard of 7.5 grams an hour.
Washington State also required that all stoves sold and installed in the state be EPA certified. To enforce this, Rod regularly emailed residents residents trying to sell old, uncertified stoves on Craigslist. “Most people didn’t know the regulations and were happy to discard the stove instead, but some just sold it another way. Periodically, we found big box stores selling new, uncertified stoves and had to send them overnight certified letters as well,” Rod recalled.
Rod’s retirement leaves a vacuum among the regulator community, as there are very few non-federal stove regulators who have the depth of experience and expertise that Rod had. He influenced policies in change out programs in Washington State and beyond and was one of the most influential state regulators in the EPA’s process to develop the New Source Performance Standards (NSPSP).
“Rod was able to build bridges between different factions and he was a diplomat – but he also knew when to take a stand,” said Lisa Rector, a Senior Policy Analyst at the Northeast States for Coordinated Air use Management (NESCAUM).
Many key figures in the wood stove industry thought highly of Rod, in part because he was accessible, responsive and practical. “Rod had a healthy appetite for knowledge and was a great listener with no preconceived bias. He was always asking great questions so as expand his knowledge base,” said Chris Neufeld, a vice president at Blaze King and Co-chair of the solid fuel section of the Hearth, Patio and Barbecue Association (HPBA).
Some in industry butted heads with Rod because Washington State regulations prevented almost all outdoor and indoor wood boilers from being sold and installed in Washington. But even companies representing those appliances often said that they he dealt with them fairly.
At least once, in 2013 when HPBA did not like an initiative Rod was spearheading, they had a lobbyist go to the legislature to send a message that Rod’s department’s funding could be in jeopardy if he pursued the initiative. Rod ultimately had to back off, ending his exploratory work to start a consumer green label for wood stoves.
Rod was also considered one of the insiders of a small group of regulators in the United States who really knew what he was talking about. Rachel Sakata, who did similar work for the State of Oregon as an Air Quality Planner, said that she continually relied on Rod’s expertise. “Rod also was a champion for pushing for cleaner devices and thanks in part to him, we now have stricter regulations for wood heating devices that help protect the public,” said Ms. Sakata. “And he continued to push for developing testing protocols that mimic real world conditions,” she said.
The Alliance for Green Heat also worked closely with Rod, recruiting him to serve as a convener and a judge for our Wood Stove Design Challenge events in 2013 and 2014. He also served on a committee that we pulled together to integrate stoves into energy audits, leading to BPI adopting them in 2015. The Alliance was also one of the stakeholders urging Rod to develop a consumer green label for stoves.
After Rod left office, the Alliance for Green Heat interviewed him, in between various trips and activities, for this blog.
Q. What do you consider one of your successes?
A. Working on and helping to fund a new cordwood test protocol that someday could become a Federal Reference Method (pdf) or possibly a state sanctioned cordwood protocol. We focused on testing various tree species to see which ones produced more PM, but most importantly we tried to get a protocol that resembled how homeowners start and use their stoves – which Method 28 did not. This initiative is now being managed by NESCAUM using Mark Champion’s lab in Vermont and I am very pleased with how it’s progressing.
Q. What was something that you did not succeed at?
A. Not being able to continue working on a consumer green label for wood stoves. This country needed a label to recognize high performing stoves and we still don’t have one that is robust and well recognized.
Q. Who were your closest colleagues?
A. Decades ago, West Coast regulators led the efforts to reduce wood smoke, but more recently, its shifted to the East Coast. California is very progressive but not influential on wood smoke issues because it is so fragmented into so many air districts. Other than Oregon, it was more fruitful for me to work with NESCAUM, NYSERDA, Brookhaven National Lab and the Wood Stove Design Challenge events.
Q. What was the best advice your boss ever gave you?
A. He told me early on that my job could be whatever I made of it.
Q. What was best guidance from your department?
A. The Department of Ecology had a policy of returning phone calls within 24 hours and emails within 48 hours. I thought that was good policy and I tried to live up to it every day.
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.
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. 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. 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. 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 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.
 See our Resources page for a list of thermoelectric retailers.
 NREL. U.S. Solar Photovoltaic System Cost Benchmark. September 2016. In 1977, solar panels cost $ 77 per watt.
 NREL PVWatts Calculator
 EnergySage. Solar Marketplace Intel Report. April 2017.
Living off the grid has its challenges, but having an alternative power sources has made our winters much brighter (pun intended). Do you generate power? What are some of the solutions that have worked for you? — Margy
Congratulations to Wayne and Margy on their thermoelectric wood stove. In a follow-up communication with Wayne, he reported that they are no longer using the system because the thermoelectric modules failed. Wayne doesn’t know why they failed, however, the most common reason for failure is overheating. The modules can also fail if Bellville washers are not used to allow the module to expand and contract during heating and cooling. Wayne also reports,