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Low Temperature Waste Energy Harvesting by Shape Memory Alloy Actuator

Hegana, Ashenafi B
http://rave.ohiolink.edu/etdc/view?acc_num=akron1461631046

Abstract Details

2016, Doctor of Philosophy, University of Akron, Mechanical Engineering.
Waste heat energy harvesting has been one of the techniques used to reduce emission of CO2 and improve efficiency of power generation, oil mining and different industrial processes. Nearly 90% of waste heat is considered low-grade (< 230OC) and is unsuitable for traditional waste heat recovery techniques. Thus, a non-continuous SMA Energy Harvesting prototype (EHP) to convert low-grade heat into electricity is presented in this research. We first demonstrate the feasibility of EHP using non-continuous shape memory alloy actuators (SMA) to convert waste heat energy to electricity. Both linear and spring shaped SMA wires made of NiTi alloy have been used to evaluate the energy harvesting capability of EHP. The experimental results proved that the EHP can generate oscillatory shaft rotation. The EHP test where the generator was connected to the main shaft through gear-box provided nearly 10V and 2.5rads shaft rotation in 0.3s. It was also found that the helical spring SMA actuator energy conversion factor was higher than that of the linear SMA actuator. Next, energy storage on both super-capacitors and micro-capacitors by the EHP with the helical spring SMA wire was explored. Using full-wave rectifier circuit, the average steady state energy stored across 6F capacitor per 2.5s of operation was 7.4mJ that is greater by factors of 4, 2 &1.2 from the stored energy across 1.4mF, 2.2mF & 3.3mF capacitors, respectively. The SMA cyclic heating and cooling experiment was developed to evaluate the relationship between SMA stress and SMA temperature, and to validate the hysteretic behavior of SMA actuator upon thermal loading. Sigmoidal-Weibull 4 parameter model was obtained as the best curve fitted model to the experimental SMA stress-temperature data. The test results also disclosed the hysteretic characteristic of SMA wires induced by cyclic thermal loading This confirmed the functionality of presented energy harvesting device using SMA actuators. Then, Heat transfer equations for annular flow were modeled. The relationship between SMA temperature and shaft angular rotation was derived from a semi-empirical SMA stress-temperature model and 2nd order Ozdemir’s SMA stress-strain equations. The simulated generator shaft rotation and generator voltage are in close agreement with the corresponding experimental results. Computational fluid dynamics simulation of EHP was performed in the 1112mm long 1/2” stainless steel and Chlorinated Polyvinyl Chloride (CPVC) pipes with linear SMA actuators centered at the pipe axis. The simulation results exhibited that there is turbulent water flow near to the entrance and then the flow becomes laminar. SMA actuator heating times inside the CPVC pipe was faster than that of stainless steel pipe. The simplified energy harvesting prototype (SEHP) was built with linear generator to optimize energy conversion factor of the EHP. The 12.7mm, 15.9mm and 19mm spring diameters of 1.9mm wire diameter SMA actuator were produced in the lab and tested in 3/4” stainless steel pipe, in 3/4” CPVC pipe, and in 1.25” Polycarbonate (PolyC) pipe. The 15.9mm and CPVC pipe were obtained as optimal spring diameter and pipe material, respectively. 5s was determined as optimal SMA heating and cooling cycle times for the optimal SMA actuators in the 3/4” CPVC pipe. The optimal spring SMA in the CPVC was tested for 60s and generated near to 8000mJ energy. Based on experimental results and analysis, EHP has a strong potential to recuperate low temperature wasted heat. At the end, novel self-sufficient flow valve was designed to alternately switch the hot and the cold water flow in the EHP so that SMA actuators can be heated and cooled without external energy supply.
Erik Engeberg, Dr. (Advisor)
Celal Batur, Dr. (Committee Co-Chair)
D. Dane Quinn, Dr. (Committee Member)
Hariharan Subramaniya I, Dr. (Committee Member)
Alper Buldum, Dr. (Committee Member)
193 p.
Automotive Engineering; Energy; Engineering; Materials Science; Mechanical Engineering; Mechanics
Energy harvesting; shape memory alloy actuator; autonomous flow valve design; linear SMA; heat engine; helical spring SMA; alternative Energy; waste heat recovery; SMA stress-Temperature; Joule heating; CFD; spring FEM; optimal design

Recommended Citations

Citations

  • Hegana, A. B. (2016). Low Temperature Waste Energy Harvesting by Shape Memory Alloy Actuator [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461631046

    APA Style (7th edition)

  • Hegana, Ashenafi. Low Temperature Waste Energy Harvesting by Shape Memory Alloy Actuator. 2016. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1461631046.

    MLA Style (8th edition)

  • Hegana, Ashenafi. "Low Temperature Waste Energy Harvesting by Shape Memory Alloy Actuator." Doctoral dissertation, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461631046

    Chicago Manual of Style (17th edition)

akron1461631046
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This open access ETD is published by University of Akron and OhioLINK.