>If a module is only 5% efficient in converting heat into electricity, the other 95% comes out as heat again. If the stove is used for space heating, this heat cannot be considered an energy loss, because it still contributes to its original purpose. Total system efficiency (heat + electricity) is close to 100% – no energy is lost.
So if you need a ton of heat and a tiny bit of electricity, this is perfect for you. Otherwise, it doesn't sound like a replacement for solar panels as much as a complementary technology for certain situations.
I think Seebeck junctions are neat. A friend has one sitting on his wood stove powering a little fan. But you're not going replace a solar system. Example systems in the article produce 10s of watts. If you're running your stove all day (ie winter) that's replacing the output of maybe one 100W solar panel. In the summer when you want to use your stove as little as possible solar will be a much better proposition.
Now if you convert your wood stove into a gasifier and drive a converted diesel generator... That be would something viable, a ton more complexity and maintenance but at least you'd have abundant power.
The forests and fields are supposed to burn in the dry season, and judging from the wildfires plaguing CA they're going to whether you like it or not. Maybe the sensible thing is actually to cull the fuel regularly and burn it to heat homes/generate energy, and solve the particulates problem head-on which sounds like a relatively minor engineering challenge.
It's sustainable in the sense that it all grows back quickly.
> Calling that "sustainable" is... maybe a sign how meaningless the word sustainable is.
There's a huge difference between burning fossil fuels, with all the logistics that involves, and burning whatever trimmings you're getting from your surroundings.
> Yes, a huge difference. The latter is orders of magnitude worse.
Do you base your personal assertion on any evidence? I'd love to see the basis for this line of reasoning. I mean, carbon emissions-wise the difference between biomass and burning oil/coal is already undisputed.
Net CO2 is one measure of badness, but damage to human health is likely a more relevant one personally. Wood is much worse for locals and better for people on the other side of the planet. Natural gas is almost clean by comparison, fuel oil is worse, and coal is terrible but still better than wood.
> Net CO2 is one measure of badness, but damage to human health is likely a more relevant one personally.
This thread is about deploying thermoelectric generators on stoves which are already in use. Smoke is already been emitted since ever. The value proposition is to seep a bit of the thermal energy already being produced to generate electricity. Thus the options on the table are a) keep a stove burning and use that to generate electricity, b) keep the same stove burning and run a fossil fuel generator on the side.
How can option b) be assumed to be cleaner?
> Natural gas is almost clean by comparison
Does this assumption take into account the environmental impact of bottling and shipping natural gas to these small villages?
Thermoelectric generators convert heat to electricity, but heat is generally the point of these stoves. In the end it’s almost guaranteed to burn more wood either because you get less heat or because you want more electricity. “b)” is therefore cleaner because of thermodynamics Aka a lack of free energy
“environmental impact” is just one of many impacts. If burning wood means you die 20 years sooner that’s likely more relevant to you than just about anything else. Of course other people you don’t know dying 20 years sooner is rarely a concern, thus different priorities.
We have internationally coordinated programmes of work to get people to move away from burnt fuel stoves to just about anything else, because so many people's lives are cut short by indoor air pollution.
In the US there is a lot of talk of "rocket stoves". In theory these should be better because the design causes higher temperatures to burn the wood gases too. Unfortunately, looking around on sites like Youtube (which is where many people get their information from) we see a bunch of things that are called rocket stoves which probably aren't. These are just small pipe stoves that are fed from the base of the fire.
Any CO2 calculation is complicated because the materials used to build stoves, and the way wood is grown and harvested and transported, all make significant differences.
> We have internationally coordinated programmes of work to get people to move away from burnt fuel stoves to just about anything else, because so many people's lives are cut short by indoor air pollution.
I'm not sure you read the doc you quoted.
I mean, it's recommendations are to ditch unprocessed coal and kerosene stoves, not biomass. On solid fuel (wood and biomass) the recommendations are to use better insulated stoves instead of open fires.
Thus, I fail to see the relevance of this in this discussion, given that the use of thermoelectric generators that served as a basis for the proposal already implies that your WHO recommendations are already been followed.
The aim is to eliminate use of these fuels. That's not practical in many areas. Moving from open fires to more efficient enclosed fires is the first step toward elimination, used only in places where cleaner fuels are not available.
Here they're clearly talk about reducing all use of these fuels.
"It is recognized that other types of intervention, including improved ventilation and behaviour changes, may contribute to reducing levels of HAP, or exposure, or both, and are an important part of all interventions. However, reducing emission rates remains central to achieving AQGs because pollutants generated in the home enter the ambient environment, contributing to outdoor air pollution exposures, and re-enter homes, exacerbating indoor pollution. Furthermore, it is important that information, training, support and other measures to ensure best use of new technologies and fuels will be an integral part of any promotion effort, whether these are delivered through public, NGO or private sector initiatives, or – as is often likely to be the case – a mix of these."
This step-wise approach is more clearly defined here:
− behavioural modifications to reduce exposure (e.g. encouraging mothers to keep their young babies away from the fire);
− household changes to improve ventilation (e.g. increasing the number of window openings in the kitchen, providing gaps between the roof and walls, or moving the stove out of the living area);
− improvements to cooking stoves (e.g. ventilation by flues, hoods or chimneys, or increases in combustion efficiency - nearly all pollutants damaging to health are products of incomplete combustion);
− interventions to enable people to use higher-quality, lower-emission liquid or gaseous fuels (e.g. petroleum-based kerosene and liquid petroleum gas, or biomass-based alcohol and bio-gas).
> Programmes can be designed to encourage urban and periurban households that use solid fuels to move up the “energy ladder” to cleaner fuels (such as kerosene or liquid petroleum gas), and do so at lower income levels (i.e. sooner) than would occur without intervention. This approach requires that the availability and affordability of cleaner fuels be enhanced. On the other hand, the poorest rural populations with nearly no cash income, but access to wood and/or agricultural wastes, are unlikely to acquire improved cooking stoves – let alone cleaner fuels – without large subsidies, which are often unsustainable in the long term. There do seem to be large populations between these extremes, however, that can be effectively targeted by efforts to disseminate improved stoves.
When you're talking about people living in an area of medium or high population density, burning tree trimmings for energy is an impractical solution which is grossly inefficient and has multiple disastrous externalities for the environment, even if it's technically carbon neutral.
It's better for the environment to sequester biomass inputs (e.g. tree trimmings) back into the soil and burn more efficient fossil fuels instead. Far from being merely carbon neutral, use of fossil fuels combined with sequestration of biomass could easily be carbon positive.
In the carbon cycle, the impact is obvious. Think about it: one just recycles carbon through photosynthesis with at worse no net change in the amount of carbon in the system, while the other is based on literally digging industrial amounts of carbon out of the ground to introduce it into the system.
I think that the intended meaning of "sustainable" in this case is that it is a form of fuel which is not fossil but renewable, and that it has neutral carbon balance.
Try plugging a modern smartphone in to an old 5 watt USB socket, the charge indicator will probably indicate charging, but it probably won’t do much unless the phone is completely off.
The energy from this type of system is far to low for what the author describes. Instead I have a coil on my stove and it is connected to a thermostat to know when the stove is hot and a hot water pump and 2 hot water tanks. Cold city water enters the first tank and circulated through the coil on top my stove. This does a great job of heating a lot of water during a day. Then the second tank pulls from the first one and it is already heated saving lots of money. The first tank is not plugged in just runs off the stove.
If you could take a lot of energy from the stove (my hot water set up can do that) you also have to worry about creosote build up. It is important to have a high air hot fire occasionally to get rid of it and to also clean your chimney yearly.
PV solar panels might not be the most efficient system overall, but they’re modular, easy to maintain, safe to DIY (for low voltage off grid systems), keep getting cheaper per watt due to economies of scale, and have lots of easily available information on how to make the best use of them.
I’ve played a lot with thermoelectric generators and experimented with lots of proposed devices such as this. The simple reality is that thermoelectric generators are just not well suited for drawing significant amounts of power.
> However, in combination with a stove, the electrical efficiency of a thermoelectric module doesn’t matter that much. If a module is only 5% efficient in converting heat into electricity, the other 95% comes out as heat again. If the stove is used for space heating, this heat cannot be considered an energy loss, because it still contributes to its original purpose. Total system efficiency (heat + electricity) is close to 100% – no energy is lost. With appropriate stove design, the heat from electricity conversion can also be re-used for cooking or domestic water heating.
Doesn't this imply that you can just keep recirculating the heat back into the module until it's converted 100% of the energy? I suppose you would need to power the recirculator somehow, but you can do that using the output of the module, so you're back to 100% efficiency again. What's the catch?
The waste heat flows out the cold side of the junction, through the heat sink, and is lost into the ambient air.
You can't feed that heat back into the hot side because it's been diluted into the air, and thus it's a lower temperature.
You can't concentrate the waste heat by enclosing the heat sink in a small volume because that would eliminate the temperature differential across the junction.
You won't gain much by making a stack of junctions with each one passing its waste heat to the next one. They effectively insulate each other, reducing the temperature differential across each one. There's an optimization opportunity here, but commercial junctions are usually already sold as a stack. Adding more layers gives rapidly diminishing returns at best.
Efficiency drops as the temperature delta goes down. The trick is maintaining that difference.
That section of the article is a bit misleading. Even really expensive stoves are only about 95% efficient. You need some heat loss out the chimney for the thing to work. I'd guess that stoves typically in use in the rural global south are much less
You can’t just recirculate heat like that. The TEG requires a temperature difference to generate voltage and power. Any recirculated hot air is not going to be any hotter than the air on the other side of the TEG.
OP doesn't comment on the air pollution from wood stoves, except to say it can be "cut in half". Half the pollution from wood stoves is still a lot of pollution. I'm reminded of this essay by Sam Harris https://www.samharris.org/blog/the-fireplace-delusion
I like Sam. I've noticed several instances of him speaking/writing as if rural areas don't exist though. The sentence "If you are burning wood in the United States, Europe, Australia, or any other developed nation, you are most likely doing so recreationally" is just monumentally silly. It's also odd to reference the WHO on the harms of burning solid fuel (not just wood) for heat in an essay condemning recreational fire-burning.
Anyway, it's all just an analogy for religion here. Not a serious treatment of the problem of air pollution.
Entertaining but also a lot of nonsense. I stopped watching after he made a show of wandering around aiming a pair of cheap folding solar panels at the sky. "These tiny solar panels won't charge my phone on a cloudy day!"
1)He compares $30 worth of solar panel to a device that probably cost several hundred dollars to build (each of those heatsinks he used cost as much as the solar panel he was waving about.) A $100 (~100W) solar panel would, even on an overcast day, produce 5-10W pretty easily.
2)You don't just use solar for power. You use solar with batteries. The panels are sized based on solar equivalent hours. There are charts that tell you what areas get in terms of "full hours of sun" each day, in summer and winter. You then figure out your typical load, how much battery capacity you want (ie how many days of zero solar output can you tolerate), and how long you want your system to recover from being completely drained while powering your typical load.
I feel there is a certain irony in Deckers hate of solar cells. Because they're pretty low tech functionally. And it's not like every other material you can acquire isn't tied to some complex industrial infrastructure.
what is the "big" version of those peltier 12v modules called? if i had to find a say 50Watt model, am i stuck with chaiming those tiny toy hobby grade stuff?
lets say i live in a place where people have lots of wood burning going during winters and this can be a nice experiment if it gives something substantial
So if you need a ton of heat and a tiny bit of electricity, this is perfect for you. Otherwise, it doesn't sound like a replacement for solar panels as much as a complementary technology for certain situations.