Device Turns Stray Microwaves into Energy
VOA News
November 12, 2013
Scientists have built a device they say can capture stray microwave signals and convert them into electrical power capable of recharging a cell phone or other small electronic device.
Researchers at Duke University’s Pratt School of Engineering in North Carolina say the device is similar to a solar panel and has a similar efficiency, and while it harvests microwaves, the researchers think the harvester could be tuned to harvest the signal from other energy sources, including satellite signals, sound signals or Wi-Fi signals.
The harvester uses something called “metamaterials,” which are “engineered structures that can capture various forms of wave energy and tune them for useful applications.”
“Until now, a lot of work with metamaterials has been theoretical,” said graduate student Alexander Katko. “We are showing that with a little work, these materials can be useful for consumer applications.”
Researchers used a series of five fiberglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electricity. By comparison, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V.
“We were aiming for the highest energy efficiency we could achieve,” said engineering student Allen Hawkes. “We had been getting energy efficiency around 6 to 10 percent, but with this design we were able to dramatically improve energy conversion to 37 percent, which is comparable to what is achieved in solar cells.”
With additional modifications, the researchers said the power-harvesting metamaterial could potentially be built into a cell phone, allowing the phone to recharge wirelessly while not in use. This feature could, in principle, allow people living in locations without ready access to a conventional power outlet to harvest energy from a nearby cell phone tower instead.
“Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting,” said lead investigator Steven Cummer.“The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power.”
The Duke study appears in the journal Applied Physics Letters in December 2013.
Language Notes 
stray (a) 流散的，漫步的
convert (v) 轉換；轉變XXXXX*後接 into：convert . . . into . . .
harvest (v) 獲得,得到
tune (v) 調整 . . . 的頻率；使協調XXXXX*tune做這個用法時，可以加上 fine 成為複合字：fine-tune，表示「微調」
科學家們製作了把空間中散佈的 (stray) 微波訊號 (microwave signals) 轉換 (convert . . . into . . .) 成電能的裝置，可以替手機或其他小型的電子裝置充電。杜克大學 (Duke University) 的研究人員表示，這個裝置跟太陽能板 (solar panel) 一樣，也有差不多的轉換效率 (efficiency)，除了收集微波之外，經過調整 (tune) 後，也能收集其他能量源，像是衛星、聲音，或是Wi-Fi的訊號。
這個收集器使用所謂的「超材料」(metamaterials)，透過特殊設計後的構造，可以捕捉多種形式的波能量 (wave energy)，再經過調整後能被有效運用 (applications)。
theoretical (a) 理論的;非應用的
conductor (n) 導體
comparable (a) 比得上XXXXX *後接 to
研究人員把一列五個材質為玻璃纖維 (fiberglass) 與銅的能量傳導體 (conductor) 接線到電路板上 (circuit board)，成功將微波轉換成 7.3 福特的電力；比較起來 (by comparison)，USB充電座給小型電子裝置提供的電力約是5福特。參與設計的學生說：「之前能源轉換的效率大概是 6~10%，但現在的設計可以大幅度 (dramatically) 提升能源轉換率 (energy conversion) 到37%，這樣就比得上 (comparable to) 太陽能電板了。」
in principle (phr) 原則上；大體上
power outlet (n) 插座
self-contained (a) 整套的完備的
scavenge (v) 從垃圾中收集（有用物品）
研究人員認為，這個收集能量的超物質經過些改造後，可以內建於 (be built into ) 手機，沒有在使用手機時能將無線充電 (recharge wirelessly)。這樣特別的功能，原則上 (in principle) 還可以讓居住地點無法取得一般電力座供電的人，透過附近的 (nearby) 手機基地台 (cell phone tower) 來汲取電力。
研究主持人 (lead investigator) 表示，這個設計的優點在於每個基本的構成方塊都是各自獨立的 (self-contained)、可增添的 (additive)，只要將更多的方塊組裝一起 (assemble) 就能增加收集來的 (scavenged) 電力。
Check your vocabulary!
Fill in the blanks with a word or phrase from the list above. Make necessary changes. After you finish, select the text below to reveal the hidden answers.
1. There are people who live in the dump and scavenge garbage for a living.
2. They converted the spare bedroom into an office.
3. The size of a dolphin's brain is comparable to a human's.
4. In principle, the new software should make the accounting system a lot simpler.
5. If the engine needs to be tuned, Dad can do it.
Source：http://www.voanews.com/content/device-turns-stray-microwaves-into-energy/1788608.html
編譯：簡嘉呈
館藏介紹
英語宅急便 
