A garden hose, a tin can, duct tape, metal piping, kitchen cleaner, and gasoline: That is all television icon MacGyver needed to make a flame-thrower to ward off a swarm of killer ants. In the real world, technologies that are affordable and practical are not so simple to create, but they can make a huge impact on people's lives. Instead of calling on complex solutions (reliant on engines and imported resources) for low-tech problems (such as cooking and lighting), some researchers are now developing what they call "confluent" technologies—ones that are effective, affordable, and sustainable for use in the developing world. Here's a look at the latest breakthroughs:

1 Energy in a Bucket of Dirt
Who needs nickel cadmium batteries or coal plants for electricity when you have soil? A Harvard team of faculty and African students have tapped into soil-dwelling microbes in order to provide electricity for families in Tanzania. When the microbes found in the soil digest organic materials, they naturally produce a small current, which can be harnessed with a simple device consisting of two electrodes and a small circuit board. One trash-barrel-sized unit filled with soil can produce enough electricity to light two bedrooms for a decade or more, says Harvard biology professor Peter Girguis. While each unit currently costs about $50, the team is testing new materials that would drive the price down to $7.

2 Micro-Hydroelectric Power
Hilly land streaked with small streams makes an ideal spot for micro-hydroelectric power generators, each of which requires a meager water flow of just three gallons per second to turn. (To put this in perspective, the Mississippi's average flow at New Orleans is about 4.4 million gallons per second.) The Appropriate Infrastructure Development Group (AIDG) has helped to build three systems in Guatemala, and more communities are now saving up money for local installations.

3 Biodigesters
At the end of Back to the Future, a little bit of garbage is all Doc Brown needs to fuel his DeLorean time machine. Biodigesters won’t quite generate "1.21 jigawatts" of power (as Doc's Mr. Fusion device seemed to), but they can create fuel for heating, cooking, and electricity while reducing waste and water contamination. In the salchicha-type biodigester (salchicha means "sausage" in Spanish), bacteria break down waste in a 15-to-30-foot-long polyethylene tube and release methane, which is captured and piped to a stove. The digested waste can then be used as a fertilizer. Biodigesters have been around since the 1870s, but current efforts focus on producing them on a larger scale. An award-winning system installed in Rwandan prisons reduced the need for firewood by half.

4 Wind Power on $2 a Day
Who said wind turbines have to spin? Shawn Frayne, founder of Humdinger Wind Energy, developed a turbine-less generator that harnesses energy from the rapid wind-induced vibration (50 cycles per second) of a seven-to-ten-foot flap of taffeta fabric. This is the same phenomenon—aeroelastic flutter—that civil engineers try to eliminate so bridges don’t sway in the wind, and on a small scale, it greatly increases the efficiency of capturing power from wind for a very small cost, says Frayne. "For people making a dollar or two a day, it could be in the realm of possibility to have electricity," says Peter Haas of AIDG, who is helping Frayne test the generators in Guatemala. Depending on wind conditions, the generators can be positioned to power efficient lights in a few rooms on small electrical grids. Frayne hopes to make the product available within a few years.

5 Sunlight Stored in LEDs
In rural Indian Homes, kerosene lamps are ubiquitous, posing health concerns from fumes as well as a fire risk. Solar-charged lights designed by Patrick Walsh, founder of Greenlight Planet, are one solution to this problem. The lights run for four hours on their brightest setting after charging in the sun all day. The lights also reduce fuel costs for families and pay for themselves in just one year. After testing the market with 20 lamps, Walsh is now scaling up production.

6 Solar Water Heater
Solar water heaters are generally expensive (they can cost $400–$1,000), barring easy access to hot water for many who are far from an electric grid. But engineer Ashok Gadgil at the University of California, Berkeley, working with AIDG, cut back on materials and came up with a solar heater that costs $100. It can produce 26 gallons of water warmed to 104 degrees Fahrenheit by 4 p.m. each day—enough for four showers. Tests are ongoing in Guatemala, after which the team plans to fine-tune the design and begin distribution.

7 Pedal-Powered Grid
People who live off the grid in rural corners of the world may soon have a new source of energy: 12-volt batteries charged by pedaling. Using a simple alternator, six hours of pedaling can create and store enough electrical energy in batteries to light about six Homes for 30 days (in areas where people use less electricity than in the U.S.). Dissigno, the San Francisco–based company that distributes the devices, has one prototype up and running in Haiti and next hopes to install a "grid" in Tanzania connected by a network of pedalers instead of power lines.

8 Sugarcane Charcoal
In Haiti, most people cook using charcoal made from wood, but the country is now 98 percent deforested due largely to mismanagement of resources. MIT students and lecturer Amy Smith turned to widely available bagasse, the stalks of sugarcane plants left after squeezing the sugar out, and created a charcoal replacement by burning, compressing, and mixing the material with a binding agent. The team is currently looking to train prospective entrepreneurs interested in producing and distributing the product.

9 Irrigation by Foot
Most African farmers rely on seasonal rainfall, having no other means of irrigation for crops. So Martin Fisher, the CEO of KickStart International, came up with a device you can pump with your feet that pulls water from 30 feet underground with enough pressure to irrigate up to two acres of land. This enables more frequent harvests of high-value crops like vegetables rather than grains. In Africa, more than 65,000 such pumps are currently in use. Fisher won the 2008 Lemelson-MIT Award for Sustainability for the invention.

10 Chlorine from Salt
For the roughly 1.2 billion people lacking clean water, a bit of chlorine could go a long way toward providing it. Using two ounces of salt water and some muscle, University of Iowa engineering professor Craig Just can make enough bleach to kill the disease-causing microorganisms in five gallons of water. His trick: a hand-cranked device that generates electricity to zap water molecules, splitting them and joining them with chlorine atoms from salt. Just and his students plan to test a prototype in Ghana and Honduras next year.

一個澆花膠皮管，錫制罐子，膠帶，金屬管，廚房清潔劑和汽油：那是按電視圖像百戰天龍所需而制的火焰噴射器來抵擋蟲子和螞蟻殺手。在現實世界中，所普及的和實際應用的科學技術并不是這么簡單就能創造的，但他們卻能給人們的生活帶來巨大的影響。代替那些解決低科技含量問題(像做飯點火和照明)而用復雜解決辦法（依靠發動機和進口材料）的行業，一些發明家現在正在發明一種他們所謂的“混合”技術—一種高效的，能普及的，實用的技術來應用到發展中的世界。下面就來看這些最新的突破：

1  垃圾桶中的能源

當你有污物時誰會想到利用鎳鎘電池和煤炭工廠來進行發電？一個來自哈佛的學院隊伍和來自非洲的學生們正鉆研于污物分解微生物的研究中來為坦桑尼亞的居民提供能源。當發現于土壤中的微生物分解有機物質時，它們會自然產生一股小額電流，可以被一個由兩個電極組成的簡單裝置和一個小型電路板所利用。一個裝滿污物的有尺寸大小的垃圾桶裝置能產生足夠可以用來為兩間臥室照明長達十年或更長的時間的能源，哈佛生物教授Peter Girguis這樣說。而每一套裝置目前要花費大概五十美元，這個團隊正在研究新型材料使價格能降到7美元。

2 微型水力發電廠
帶有小溪的多丘的山地是安裝微型水利發電設備的理想之地，每個僅需每秒三加侖水量的微弱水流即可運轉。(從投入的角度看，密西西比河在新奧爾良的平均水流量大約為每秒4.4百萬加侖。適當的基礎設施發展集團已經幫助在危地馬拉建立了三套系統，更多社區正節省錢財來用于當地的設施安裝。

 3 生物降解
在影片回到未來的結尾, Doc Brown所需的就是一點垃圾來給他的德羅寧時光機提供燃料.生物降解不會產生＂1.21瓦＂的動力(如Doc's Mr熔解裝置所示),但它們能生成燃料來加熱,做飯并且能發電同時還減少廢物排放和水污染.在這個salchicha型的生物降解中(salchicha在西班牙語中的意思是香腸),細菌在一個15-30英尺長的聚乙烯試管中分解廢物并且釋放甲烷,獲取后并將其通過管子送到爐子中.分解后的廢物可以被用作肥料.生物降解技術自從19世紀70年代就被廣泛使用,但目前的努力正致力于大規模的生產.一個屢獲殊榮的裝置被安放在盧安達監獄中從而減少了一半對木柴的需求.

4 每天2美元的風力
誰說風渦輪機就得自轉? Humdinger風動能的創始人Shawn Frayne,發明了一個無風渦輪發動機,能從一個利用7-10英尺的塔夫綢織物拍打的快速風感應裝置的震動中(每秒50轉)獲取能量.這和氣動彈性顫震是同一種現象—國內的工程師們正試著消除在風中不擺動的橋接器,并且在一個較小的程度上,它逐漸提高了用低成本獲取風能的效率, Frayne說.“人們一天花1-2美元，就有用電的可能性，” AIDG的彼得哈斯這樣說，他為在危地馬拉做發動機實驗的Frayne提供了幫助。依靠風自身的條件，發動機可以被安置在小的電網上為數間屋子提供照明。Frayne希望這個產品幾年之內就可為人們使用。

5  用發光二極管儲存陽光
在偏遠的印第安人家庭中,煤油燈無處不在,煤煙對人的健康帶來威脅并且有火災隱患.由綠光星球的創始人派屈克沃爾什設計的太陽能充電燈,對此問題是一種解決的辦法.這種燈在一整天的陽光下充足電后可以在最亮的設置下連續點四個小時.這種燈也能減少家庭用煤的成本并且一年后就可以買到它們.在市場上投放了20盞燈作為實驗后,沃爾什正按比例加大生產量.

6 太陽能熱水器
太陽能熱水器通常來講很貴（要花費400美元至1000美元），除了那些沒有電網還能輕易獲得熱水的人。但位于伯克萊的加州大學工程師Ashok Gadgil，和AIDG合作，消減材料的成本費用并制造出只需100美元的太陽能熱水器．它能在每天下午四點之前加熱26加侖的水至華氏溫度104度－足夠淋浴四個小時.實驗正在危地馬拉開展,隨后團隊將對設計進行微調并開始經售.

7 踏板電網
住在世界偏遠地區遠離電網的居民不久將會擁有一種新型能源：用腳踏板來充電的12瓦特的電池。使用這個操作簡單的替代品，六個小時的腳踏即可產生并能儲存供六個家庭使用三十天的電（這些地方的居民比起美國居民用電量更少）。Dissigno，這家舊金山的公司經售這些裝置，有一套原型并在海地運作并且下一步希望在坦桑尼亞安裝一個＂電網＂用腳踏裝置來代替電線來連接.

8  甘蔗木炭
在海地，大部分居民用木頭制成的木炭來做飯，但是這個國家現在98%的森林由于對資源的管理不善而遭到破壞。麻省理工學院的學生和講師艾米史密斯將研究轉向了廣泛種植的甘蔗。甘蔗的莖能在榨干糖分后經過烘烤，擠壓，用一種粘合劑混合其它物質然后成為木炭的替代品。這個團隊目前正在尋找培養有前景的企業來生產并推廣這種產品。

9用腳來灌溉
大部分非洲的農民都依賴季節性的降雨，沒有其他灌溉農作物的手段。所以馬丁菲斯而，KickStart國際的首席執行官，發明了一種裝置可以用腳施加足夠的壓力把離地30尺的地下水抽上來灌溉兩英畝地。這使得許多像蔬菜這樣的高產農作物比谷物類收成更多。在非洲，大約有65000多這樣的抽水機正在使用。菲斯而贏得了由麻省理工學院頒發的發明可持續大獎。

10  鹽中的氯
 大約有12億的人缺少干凈的水，到能提供足夠的氯還要花很長的時間。用兩盎司的鹽水和一些壓力，衣阿華州大學的動力專家克萊格就能用足夠的漂白劑來殺死五加侖水中的致病微生物。他的辦法是：用一個手動曲柄裝置來產生電流快速震擊水分子，分解它們同時用鹽中的氯分子來連接它們。他和他的學生們打算明年在加納和洪都拉斯做一個實驗模型。