African Lights: Microgrids Are Bringing Power to Rural Kenya

Plugging into electricity for the first time is a big deal. Ask Peter Okoth. Until late last year, he struggled to make a go of his bar on the main street in Entasopia, a small, dusty town in Kenya’s Rift Valley, five hours from the capital Nairobi and 30 miles from the nearest grid power line. Then, he hooked up to a new solar-powered microgrid that serves local homes and businesses. 

Now Okoth has eleven light bulbs, he says proudly — and enough power to run a TV and a sound system for his customers. Seventy people show up some evenings to watch, listen and buy his food and drink. His profits will  

Soon buy a refrigerator to  keep the beer cold in the searing desert heat, and a big screen to show satellite sports channels. “We will be staying open till midnight,” he says. And he has just bought construction materials for ten guest rooms. “When you next come, you must stay here.” Most settlements in rural Kenya are dark at night. Only a third of the East African country’s residents have access to the national power grid. Harvesting the sun makes obvious sense in places like Entasopia. Hundred-dollar photovoltaic (PV) panels for installation on home roofs have been on sale for years. But the meager five watts that most such systems provide is only enough to power a couple of LED lamps each evening and a mobile phone charging point, and the batteries constantly need replacing. The country is full of discarded PV cells, defunct batteries, and disappointed customers. 

But now, larger central village PV units linked by underground cable to dozens of houses and business are starting to transform lives. For a ten-dollar installation fee, the people of Entasopia can connect to a village microgrid and buy a share of a thousand times as much power. Village homes are filling with household appliances like refrigerators and washing machines, and the businesses on the main street are powering everything from welding equipment and fuel pumps to hair driers. 

Microgrids are small electricity generation and distribution systems that operate independently of larger grids. Typically they rely on local sources of renewable energy, such as river flows, wind, biomass, or, most widely, the power of the sun. There are no official statistics on how many there are, or what their total power output is. But a recent study by U.S.-based Navigant Research, which studies new energy technologies, suggested that their combined generating capacity might now exceed 750 megawatts worldwide. They are, says Daniel Kammen, of the University of California,Berkeley, “a true hot-bed of innovation popping up all over the world.”

Source by: https://e360.yale.edu/feature/african_lights_microgrids_are_bringing_power_to_rural_kenya/2924/

The War of the Currents: AC vs. DC Power

Electrical transmission lines cross a snow-covered field in Dallas Dam, Oregon. | Photo courtesy of the Energy Department

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Starting in the late 1880s, Thomas Edison and Nikola Tesla were embroiled in a battle now known as the War of the Currents.

Edison developed direct current -- current that runs continually in a single direction, like in a battery or a fuel cell. During the early years of electricity, direct current (shorthanded as DC) was the standard in the U.S.

But there was one problem. Direct current is not easily converted to higher or lower voltages.

Tesla believed that alternating current (or AC) was the solution to this problem. Alternating current reverses direction a certain number of times per second -- 60 in the U.S. -- and can be converted to different voltages relatively easily using a transformer.

Edison, not wanting to lose the royalties he was earning from his direct current patents, began a campaign to discredit alternating current. He spread misinformation saying that alternating current was more dangerous, even going so far as to publicly electrocute stray animals using alternating current to prove his point.

The Chicago World’s Fair -- also known as the World’s Columbian Exposition -- took place in 1893, at the height of the Current War.

General Electric bid to electrify the fair using Edison’s direct current for $554,000, but lost to George Westinghouse, who said he could power the fair for only $399,000 using Tesla’s alternating current.

That same year, the Niagara Falls Power Company decided to award Westinghouse -- who had licensed Tesla’s polyphase AC induction motor patent -- the contract to generate power from Niagara Falls. Although some doubted that the falls could power all of Buffalo, New York, Tesla was convinced it could power not only Buffalo, but also the entire Eastern United States.

On Nov. 16, 1896, Buffalo was lit up by the alternating current from Niagara Falls. By this time General Electric had decided to jump on the alternating current train, too.

It would appear that alternating current had all but obliterated direct current, but in recent years direct current has seen a bit of a renaissance.

Today our electricity is still predominantly powered by alternating current, but computers, LEDs, solar cells and electric vehicles all run on DC power. And methods are now available for converting direct current to higher and lower voltages. Since direct current is more stable, companies are finding ways of using high voltage direct current (HVDC) to transport electricity long distances with less electricity loss.

So it appears the War of the Currents may not be over yet. But instead of continuing in a heated AC vs. DC battle, it looks like the two currents will end up working parallel to each other in a sort of hybrid armistice.

And none of that would be possible without the genius of both Tesla and Edison.

Source by:http://energy.gov/articles/war-currents-ac-vs-dc-power