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How to Use an Exhaust Heat Recovery System to Charge up your Phone



Although the world is constantly moving towards cleaner and greener means of transportation, a complete transition to these kinds of transport is still years away. So in the meantime, here’s one small technological device that improves the efficiency of conventional engines everywhere.

Modern versions of the internal combustion engine found in a typical motor vehicle have an efficiency rating of only 18-20%, meaning roughly 80% of the energy is lost to the surrounding environment, escaping mainly in the form of heat. What this device does is it traps this wasted energy and makes use of it by relying on a thermoelectric element known as a Seebeck module. Put simply, these modules generate electricity through manipulating differences in temperature.

The efficiency rate of this device is around 3%, and while this may strike some as being insignificant, don’t be naive. The current version needs to be attached to the exhaust pipe of a motorcycle, but it’s easy to adapt it for cars and other vehicles. As exhaust heat represents 60% of total heat energy loss, this device effectively increases engine efficiency by roughly 1.3%.

Attaching the heat-harvesting device to the exhaust will fuel a battery that can be used to charge a cell phone. Think of the possibilities if everyone had this device attached to their vehicle. It’s possible to make green energy simply right now, so what are you waiting for? Here’s how:

Step 1: Build a heat transfer block


This block is what attaches the device to your vehicle’s exhaust pipe. It’s important to optimize the heat transfer so measure the exhaust’s diameter. In this case it was 2.2 cm, but that can vary. Total area: 12×4 cm for 3 Seebeck modules. Pushan used a 12×4 cm aluminum block cut in half.

Step 2: Wire up the electronics


Well, the electronics for a heat harvesting module consist of three thermoelectric (Seebeck) units linked in series. Thermoelectrics are semiconductors that use the difference in temperature between their two sides and turn it into electricity.

Step 3: Model and build the heat sink

While heat sinks don’t have a particular standard, you can build them according to your own needs. After hours of work, here’s what came out:


Next, Pushan mounted the entire assembly onto his motoscooter’s exhaust and hit the road. He says he was able to charge up two phones during their commute to work.

While this experiment may be successful, it’s only a drop in the ocean compared to what a research institute can do in this field. Finding out better “recipes” for thermoelectric materials could mean our combustion engines could generally become more efficient and car-originated pollution would drop.

To see more details and follow the project or to build it yourself, check out the original page of Pushan Panda on Instructables.

pictures (c) Pushan Panda/Instructables

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