|Acquisition Program: || Objective: ||To develop a high performance milliwatt power generating source by integrating an very low weight thermoelectric (TE) energy generator with the power management architecture to recharge battery on the body while the users are on the move. The milli-power source will be based on an energy harvesting system using state-of-the-art thermoelectric technology that allows one to generate more than 2mW per cm2 of surface area, with only a 2-degree temperature difference between the body surface temperature and the outside body temperature (outside clothing or uniform). It will include an efficient boost circuit to convert the low voltages of the thermoelectric power generator to levels that are useful for recharging the battery on the body. In addition, it will provide a cooling or heating effect on the body. The system will require power management control at the transistor and circuit level to minimize overall power consumption, while providing maximax power to recharge the battery when needed.
|| Description: ||Energy can be harvested from many sources such as wind, solar, vibrations, temperature differentials, etc. The challenge is that the amount of energy available at any one time from some of these sources is quite small, and thus a method for capturing and storing the power for later use is required. The devices must also have low signature for covert surveillance missions. Furthermore, to maximize power generation, an approach is needed that can harvest energy over the broad operating conditions. This limits the use of solar approaches that don’t work at night and vibration approaches that have very limited operating environments. Thermal gradients, however, are available between the skin body temperature and ambient air year round both during the day and at night. Estimates of absolute average daily temperature gradients between the body skin temperature and air temperature range from 4.5 to 5.8°C in the field environment throughout the year. This makes thermoelectric energy harvesting an ideal approach over broad operating conditions.
|| ||PHASE I: This phase of the program is to demonstrate the validity of the technical approach by analysis, modeling and simulation, and verification with some use of off-the shelf hardware. In particular Phase I needs to define body temperature and power available, research methods for boosting low VDC, design voltage booster unit, design power storage and control unit, develop power source architecture and establish form factor for product.
|| ||PHASE II: Based on the results of phase I, the designs of all of the parts of the system will be optimized and developed. Study the feasibility of processes allowing to make these materials on a large scale - to make the low cost production possible. Bench prototypes will be built and their performance verified. prototype will be delivered for testing and demonstration purposes.
|| ||PHASE III: A development of autonomous unattended power generating sources where they can be recharged by the Land warrior battery and/or BB-2590 lithium ion battery. A pilot line and small scale production will be set-up, with large manufacturing and low cost in focus. A sufficient number of small production prototypes will be delivered for testing and demonstration purposes.
|| References: ||.Technological Frontiers in Portable Energy, Deshpande Center for Technological Innovation, Massachusetts Institute of Technology, IdeaStream Symposium 2003, May 14, 2003, http://web.mit.edu/deshpandecenter/downloads/presos/ideastream2003_portable.pdf|
|Keywords: ||thermoelectric, micro-power, energy harvesting, low voltage electronics|
Questions and Answers:
Q: The solicitation lists two different delta T ranges for this topic; a 2 degree (C?) dt and a 4.5 - 5.8 degree C dt. Which dt should we be designing the system to operate at to produce the desired 2+ mW per cm2?
A: The 2 degree should be the right one. If you have higher delta, you should higher output as well.
Q: 1. Whose "state-of-the art thermoelectric technology" do we use?
2. Where can I find technical specifications and size data?
A: 1. We are looking the state of art of thermoelectric technology.
2. It is up to you to propose the size and weight to recharge our standard battery such as BB-2590 or Li-145 lithium ion battery which they have 200 Wh or 145Wh.
Q: On this SBIR topic, does the Army prefer power electronics and integration solutions using existing TE technology?
Or is there more interest in progressing the TE technology?
A: Army is interest in the package that deliver the power to recharge the battery as well as the capability to cool the soldier down. We are looking for the whole package.