I wish to comply with energy-harvesting analysis developments and precise installations, as there are various inventive approaches and helpful purposes. In lots of circumstances, harvesting has solved a power-source drawback successfully and with cheap price versus profit.

On the similar time, nevertheless, I see power harvesting as typically being oversold at greatest and overhyped at worst. There’s an actual glow with the idea of getting one thing for (virtually) nothing that’s typically related to it, when the cruel actuality is chances are you’ll be getting little or no power for a a lot larger price and complexity than what was promoted. That tradeoff could also be acceptable if you’re determined or don’t have any viable various, however typically that isn’t the case.

Maybe the strangest non-conventional harvesting scheme I noticed was a specialised coating that could possibly be utilized as wall paint (see References 1 and a pair of). That coating used humidity within the air to reap power, with the speculative projections that perhaps you may energy a home utilizing this paint. In fact, past the apparent problems with physical-connection wiring, there was the near-trivial precise obtainable output. The ability density output of 0.0001-0.05 watts/meter² was fairly modest (to be well mannered) in each absolute and relative phrases and positively wouldn’t energy your home or perhaps a smartphone.

Tailpipe TEG

instance of a extra sensible harvesting association is a current thermoelectric generator (TEG) story I noticed within the Wall Avenue Journal, of all locations (Reference 3). A analysis crew at Pennsylvania State College developed a TEG that matches into the exhaust tailpipe of an inside combustion engine (ICE) automobile and makes use of the exhaust waste warmth to generate as much as about 40 watts (Determine 1).

Determine 1 (a) 3D schematic diagram of the TEG system. The geometry of the exhaust fuel pipeline can fluctuate. (b) Energy (P) and (c) energy density (ω) for car and high-speed object situations. Supply: Pennsylvania State College

Whereas that’s sufficient to energy or recharge a small digital gadget, it’s a reasonably modest quantity of energy within the context of the facility of the engine of a automobile, small airplane, or helicopter. Certainly one of their claimed improvements on this implementation is that it’s optimized to work higher when there’s cooling airflow across the shifting tailpipe, yielding a bigger temperature differential and thus higher output. The design has been modeled, a prototype constructed and examined, and the collected information is consistent with the expectations (Reference 4).

Up to now, so good. However then it the storyline goes into what I name extrapolation mode, because the “free power” and “one thing for nearly nothing” points begin to overtake actuality. How a lot does this harvester price as a single unit, or maybe as a mass-produced merchandise? How lengthy will it final within the tailpipe, which is a harsh atmosphere? What’s the impact on engine exhaust movement and again strain? What’s the developed power density, by weight and quantity?

The WSJ reporter protecting this story gave the impression to be a non-technical journalist who principally repeated what the researchers stated—which is definitely a sound place to begin—however didn’t ask any follow-up questions. That’s the issue with most energy-harvesting tales, particularly the free-heat TEG ones: they’re so engaging and feel-good in idea that the realities of the design and set up should not introduced up in well mannered dialog whereas the advantages are touted.

I’m not saying that this TEG harvesting scheme is of no worth. It could, actually, be helpful in particular and well-defined conditions. There are various examples of viable waste-heat restoration installations in industrial, business, and residential settings to show that time. However as will all designs, there are arduous and tender prices in addition to short- and long-term implications that shouldn’t be ignored.

Small-scale TEG

There are additionally smaller-scale TEG-type harvesting success tales on the market. For instance, for a lot of a long time, gas-fired house water heaters used their very own always-pilot gentle (not allowed in lots of locations as a result of power mandates) to warmth an array of thermocouples. This array then supplied energy to activate and activate the fuel valve and ignite the fuel to warmth the water within the tank (Determine 2).

If the pilot gentle was out for any cause, turning on the fuel valve to warmth that water could be extraordinarily harmful. Nonetheless, the gas-heated thermocouple system is self-protecting and fail-safe: within the absence of that pilot gentle that ignites the fuel and heats the thermocouples, there is no such thing as a energy to actuate the valve, thus the fuel movement could be shut off. As a further profit, no electrical wiring of any sort was wanted by the water heater. It was a plumbing-only (water and fuel) set up with no exterior electrical energy wanted.

Determine 2 This schematic of a gas-fired water heater reveals the underside thermocouple meeting whose electrical output controls fail-safe actuation for the gas-flow valve. Supply: All Trades Las Vegas

Harvesting hubbub

My sense is that harvesting will get a lot favorable consideration as a result of it’s so relatable and seems to supply no/low-cost advantages with little draw back, no less than at first look. There’s little doubt that the multifaceted attraction of TEG and different energy-harvesting approaches attracts lots of optimistic consideration and media protection, as this one did. That’s a giant plus for these researchers as they search for that subsequent grant.

Engineers know that actuality is often totally different. With regards to producing, capturing, and utilizing power and energy, the outdated cliché that “there’s no such factor as a free lunch” often applies. The true query is the price of that lunch.

Have you ever used TEG-based harvesting in any challenge? What have been the anticipated and surprising points and advantages? Did you keep it up, or do you need to go along with one other strategy?

Invoice Schweber is an EE who has written three textbooks, lots of of technical articles, opinion columns, and product options.

Associated Content material

• Area of interest Vitality Harvesting: Intriguing, Progressive, Most likely Impractical
• Underwater Vitality Harvesting with a Information-Hyperlink Twist
• Intelligent harvesting scheme takes a deep dive, actually
• Is triboelectricity the subsequent harvesting supply?
• Tilting at MEMS Windmills for Vitality Harvesting?
• Vitality harvesting will get actually private
• Lightning as an power harvesting supply?

References

1. Nature, “Generic Air-Gen Impact in Nanoporous Supplies for Sustainable Vitality Harvesting from Air Humidity”
2. Nature, Complement to “Generic Air-Gen Impact in Nanoporous Supplies for Sustainable Vitality Harvesting from Air Humidity”
3. The Wall Avenue Journal, April 18, 2025, “The Warmth Coming Out of Your Automotive’s Tailpipe? Some Can Be Turned Into Electrical energy”
4. ACS Utilized Supplies & Interfaces, January 7, 2025, “Thermoelectric Vitality Harvesting for Exhaust Waste Warmth Restoration: A System Design” (behind paywall, however additionally it is posted right here at ResearchGate)

The submit TEG power harvesting: hype or hope? appeared first on EDN.