비행 풍력 발전기 - 마카니 Makani

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비행 풍력 발전 - 마카니 Makani

2013년에 구글의 비밀 연구조직인 구글[X]에 인수되어 화제가 되었던 마카니^[각주:1]는 고공풍력발전(Airbone Wind Turbine), 에너지 연(Energy kite)의 한 일종이다. 

마카니의 구성 및 사양

마카니 고공풍력 발전 시스템은  

하늘을 나는 비행체와 땅에 고정된 기지(Ground Station) 그리고 이 둘을 연결하는 연결선(tether)이 있다. 

마카니의 발전능력은 600 kW이다. 

마카니는 가벼운 탄소섬유 기체로 이뤄져 있으면 발전용 프로펠러 8기를 갖추고 있다. 

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마카니의 구동 방법 

처음 하늘로 올라갈 때는 비행체의 날개에 있는 프로펠러 4개를 이용하여, 헬리콥터처럼 고도를 높인다. 

고도 140∼300m정도 올라가면 발전을 위한 비행을 시작한다.

하늘에서 한 곳에 머물러 있는 것이 아니라 원을 그리듯 회전하는데, 

효율성을 높이려는 것으로 최적의 비행 패턴을 그리는 것이다. 

비행을 하면서 날개에 있는 로터(rotor)가 돌면서, 전기가 생산된다. 

생산된 전기는 연결선(tether)를 통해서 기지(ground station)으로 송전된다. 

비행체 내부 컴퓨터가 

GPS와 다양한 센서들을 이용하여 수천가지의 계산식을 풀어서, 

비행체가 하늘에서 계속 비행할 수 있도록 한다. 

기상 악화 등으로 운영하지 않을 경우, 

비행체와 연결된 연결선을 다시 감아서 

비행체를 그라운드 스테이션에 묶어둔다. 

마카니의 발전 원리 

풍력 발전기는 바람이 일정한 방향으로 빠를 수록, 발전량이 많아 진다. 고도가 높을수록, 지표면의 영향을 덜 받으므로 바람이 균일하면서 빠르다. 지상 80m 상공에서는 일반적으로 초속 4.6m의 세기로 바람이 불며, 800m 상공에서는 초속7.2m로 바람이 2배 정도 빨라진다. 풍력 발전의 발전량은 풍속의 세제곱에 비례하기 때문에 고도 80m에 비해 1 km에서는 약 8배가 많은 전력을 생산할 수 있게 된다. 

마카니는 풍차형태의 기존 풍력발전에 비해 더 높은 곳에서 풍력발전기를 운영할 수 있다.   

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How It Works

The Makani energy kite system consists of four parts: the energy kite, the tether, the ground station, and the computer system.

The Energy Kite

The energy kite simulates the tip of a wind turbine blade, which is the part of a turbine that makes most of the energy. The kite is launched from the ground station by the rotors, which act like propellers on a helicopter. Once in the air, the kite generates power by flying in large circles where the wind is strong and consistent. Air moving across rotors mounted on the kite forces them to rotate, driving a generator to produce electricity, which travels down the tether to the grid.

The Tether

The tether looks like the string of the kite, but is made of conductive wires surrounding a high strength core. The tether carries energy from the kite to the grid, and connects the kite to the ground station.

The Ground Station

The ground station holds onto the tether, and is used as a resting place for the energy kite when not in flight. The ground station occupies less ground space and is significantly smaller than conventional wind turbines.

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마카니의 장점

기존 풍차형태의 풍력발전기처럼 거대한 타워나 큰 날개가 필요하지 않기 때문에, 자재를 90% 절감할 수 있다.

그라운드 스테이션은 콤팩트한 크기로 공간 활용도가 높고 이동성도 뛰어나다. 

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마카니의 역사

공동 설립자 중 한명인 Corwin Hardham이 카이트 서핑에서 영감을 받아

2006년, Corwin Hardham, Don Montague, Saul Griffith가 마카니 파워사를 설립하였다. 연 기술(kite technology)을 이용하여 저렴한 재생에너지 발전을 개발하는 것이 목표였다. 구글 재단(google.org)의 RE<C 프로그램 중 하나로 1000만 달러를 초기 투자받았다. 이 후 미국 에너지부(DOE, U.S. Department of energy)가 지원하기도 하였다.  

2013년, 구글글라스와 자동운전차량 등을 연구하는 구글 내 연구기간이 구글[X]가 마카니 파워를 인수하였다.  

Makani was founded in 2006 by Corwin Hardham, Don Montague and Saul Griffith with the goal of developing a low-cost renewable energy solution using kite technology. Initial funding came from Google.org as part of our RE<C program. Makani joined Google[x] in 2013.

마카니 홈페이지

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What is Makani’s mission?

Makani hopes to accelerate the shift to clean, renewable energy by developing energy kites, a new type of wind turbine. Makani is developing an energy kite that can generate 50% more energy while eliminating 90% of the materials used and at lower cost than conventional wind turbines.

How did Makani get started?

Makani was founded in 2006 by Corwin Hardham, Don Montague and Saul Griffith with the goal of developing a low-cost renewable energy solution using kite technology. Initial funding came from Google.org as part of our RE<C program. Makani joined Google[x] in 2013.

How is Makani’s energy kite different?

Makani’s energy kite actually operates on the same aerodynamic principles as a conventional wind turbine, but is able to replace tons of steel with lightweight electronics, advanced materials, and smart software. By using a flexible tether, energy kites eliminate 90% of the materials used in conventional wind turbines, resulting in lower costs. Because energy kites are more aerodynamic and able to access stronger, more consistent wind at higher altitudes, they’re able to generate 50% more energy.

How is an energy kite able to access winds in more locations than a conventional wind turbine?

Wind power systems are only viable in places that can generate enough power to offset costs. For conventional wind turbines, less than 15% of all the land in the world is suitable. Energy kites, on the other hand, can be economically sited in a wide array of locations, including sites that are too remote from roads, too hilly, or not windy enough for conventional turbines. In the continental United States alone, energy kites can generate wind power economically in over 66% of the landmass, more than four times the area available to conventional wind turbines.

How does the energy kite work?

The energy kite is launched from the ground station by the rotors, which act like propellers on a helicopter taking off. Once in the air, the energy kite generates power by flying in large circles where the wind is strong and consistent. Air moving across small rotors mounted on the energy kite forces them to rotate, driving a generator to produce electricity, which travels down the tether to the grid. The energy kite’s path is guided by the flight computer, which will use GPS and other sensors to make many thousands of calculations and adjustments to fly the kite in strong and steady winds.

How is the energy kite maintained?

The energy kite can land on the ground station, making large cranes or helicopters (two ways that conventional wind turbines are typically repaired) unnecessary. As a result, energy kites are easier, safer, and less expensive to maintain.

Where will the energy kites eventually be installed?

It makes most economic sense for energy kites to be installed in wind farms similar to large, conventional wind turbines. However, since energy kites require less wind to make power and can reach stronger winds at higher altitudes, the wind farms can be sited in many more locations. Additionally, energy kites fly above topography that is typically unsuitable for conventional wind turbines, such as valleys.

How safe is the Makani energy kite?

Makani uses advanced technology and rigorous testing to ensure that the energy kite is safe. There are multiple redundant computers, rotors and other components on the kite to ensure it can keep flying in the unlikely event that something stops working. The kite is also able to land on the ground for maintenance. Energy kites are also tested on sites that are far away from people, infrastructure and airplane flight paths.

How does the energy kite handle changes in wind and weather conditions?

If the wind slows down temporarily, the rotors that generate energy can become propellers to keep the kite aloft until the wind picks up again. If the wind stops altogether, the energy kite can be brought safely back to the ground station by the rotors, which act as propellers. During particularly extreme weather, the energy kite can land until conditions normalize, unlike conventional wind turbines which must be built robustly to withstand gale force winds. In simulation, the Makani energy kite has been shown to operate in hurricane conditions.

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2015. 04. 02 작성

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