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From the world's largest solar furnace to a still that turns salt water into drinking water, the range of devices that harness the sun's energy is breathtaking. Here are some of our favourites
Making hay while the sun shines
With more energy from the sun reaching Earth in an hour than we humans use in a year, it's no wonder that people have come up with myriad ways to use that power -- including a recent project announced by Google X for using solar-powered balloons to bring Internet access around the world.
Here are 11 other solar projects that are either in use today or in development. Some have humanitarian aims, such as a solar-powered toilet and waste treatment system meant for areas of the world that lack adequate sanitary facilities. Others, like a racecar powered by 2,000 solar cells, are just plain cool. All will make you sit up and take notice.
Solar-powered, but not slow
The Tokai Challenger solar racecar made its debut in 2009's World Solar Challenge, a biannual solar race across Australia. Designed and built by a team from Japan's Tokai University, the Tokai Challenger won the race that year and again in 2011.
The World Solar Challenge stretches 1,877 miles across the Australian Outback. The Tokai Challenger covered that distance in 29 hours and 49 minutes in 2009, then in a slightly slower 32 hours and 45 minutes in 2011. The car, covered in 2,176 solar cells that were originally designed by Sharp to be used in satellites, reached a top speed of 93 mph and averaged 60 mph.
Up, up and away
The Solar Impulse, a solar-powered plane that can fly both day and night using power stored in its lithium-ion batteries, made its maiden voyage in 2009, traveling 1,150 feet at an altitude of just over 3 feet. It has since completed much farther (and higher) flights, has flown overnight, internationally and even intercontinentally.
The plane harnesses the sun's energy using 11,628 photovoltaic cells. Its 208-foot wingspan is roughly that of a jumbo jet, but it weighs only as much as a car. It has a cruising speed of 44 mph and carries one person at a time.
The Solar Impulse recently completed a journey across the U.S. in stages, and it's set to fly around the world in 2015.
Solar on the high seas
The MS Tûranor PlanetSolar is the largest solar boat in the world. First launched in Germany in 2010, the catamaran spent the next two years circumnavigating the world, stopping in 28 countries along the way.
This 101-foot-long ship, which averages 5 knots (5.75 mph), travels with a four-person crew but can hold up to 60. The surface of the boat is covered with 5,554 square feet of solar cells.
Plans for the future include being used as a scientific platform for a deepwater expedition in the Gulf Stream, called PlanetSolar DeepWater. Because PlanetSolar does not release any pollutants into the water, the data gathered by the scientific team will not be skewed by gases, which can be emitted by non-solar boats.
Now you're cooking with solar
The SolSource solar cooker, which focuses solar energy onto a small area, can be used to cook meat, vegetables and grains. It reaches temperatures of up to 1,800 degrees Fahrenheit and boils water in 10 minutes.
One Earth Designs developed the solar cooker with input from rural villagers in western China so it would meet their needs and provide a safe, clean alternative to burning coal, wood or dung for cooking. The local government in Qinghai has partnered with One Earth Designs to distribute the first 800 units of the SolSource.
The Kickstarter-funded company also plans to sell the SolSource in Western markets for backyard barbequing to offset some of the costs of distributing the units to rural areas.
Hot enough for ya?
Solar cookers are based on their much larger brethren, solar furnaces -- massive solar structures that focus heat from the sun onto a small area, creating extraordinarily high temperatures. This heat can be used for a variety of purposes, such as hydrogen fuel production, for research that requires high temperatures, even to make nanomaterials.
This solar furnace, located in sun-drenched Odeillo in the French Pyrenees, is the largest in the world. It has been around since 1970 and uses 63 heliostats to reflect the sun's rays onto a 21,500-square-foot parabolic mirror, which concentrates the energy onto a focal point. The furnace can heat up an area roughly the size of a teakettle to over 6,000 degrees Fahrenheit.
Clean water from clean tech
Eliodomestico, a solar household still, was designed by industrial designer Gabriele Diamanti to provide people in developing countries with fresh drinking water. The still, which converts salt water into drinking water, works like an upside-down coffee maker. You pour water into the still through the top, and as the sun heats up the water, steam is forced down through a nozzle into the container below.
The simple yet elegant device can provide 5 litres of fresh drinking water each day and is made from widely available, inexpensive materials. A thoughtful touch: The bowl that the steam condenses into is made to carry easily on the user's head.
Solar spreads its wings
The Solar Ark, located in Gifu, Japan, is a power generation facility with 5,046 solar panels spread over its unique 1,033-foot-wide by 121-foot-tall frame. Built by electronics giant Sanyo, which has since merged with Panasonic, the winglike structure is supported by just four columns. Annually, this building can generate 530,000 kilowatts of energy, enough to power more than 200 homes.
In a different building, this site also hosts the Solar Lab, a museum about solar energy. The museum has 10 zones, including a solar library and solar community garden, which houses a solar-powered robot.
Pooling solar power
The Drake Landing Solar Community in Okotoks, Alberta, Canada is a planned neighborhood built with green energy in mind. The 52-home community gathers energy from 800 solar panels located on garage roofs; collectively it can gather 1.5 megawatts of thermal power during a summer day.
Through the solar panels, the sun heats up a glycol solution, which travels through connected piping to the community's energy center. Once there, the heat is transferred to water in the short-term storage tanks or stored underground for winter in borehole thermal energy storage. This system provides 90% of Drake Landing's space heating.
Two separate solar panels on each house's roof supply up to 60% of that house's hot water heating.
Credit: "Aerial photo of completed solar community: homes, garages and Energy Centre, September 2007." Natural Resources Canada, 2007. Reproduced with the permission of the Minister of Natural Resources of Canada, 2013.
This project, dubbed SunHope, proposes to cover 10-ft. helium balloons with low-cost photovoltaic arrays. The balloons, designed by Joseph Cory of Geotectura along with Dr. Pini Gurfil, are not yet in use but have been tested. The idea is to collect and provide energy to areas where large solar panels are not practical or possible, like crowded cities or rural areas.
Each balloon has the potential to provide one kilowatt of energy -- roughly equivalent to 25 square meters of solar panels. Cory and Gurfil estimate that one balloon would cost around US$4,000, as opposed to US$10,000 for comparable solar panels. One or two balloons linked together can potentially power one home; attach more to power entire communities.
Hot sun, cool shade
Though not actually in use, the VEIL solar shade concept, designed by Büro North, is a government-funded initiative to harvest solar power in Australian schoolyards. The structures, which provide shade while absorbing and storing solar energy via photovoltaic cells, can be manually rotated throughout the day to best take advantage of the sun's energy.
An LED panel on the underside of the shade shows how much energy it is absorbing, indicating that the shade should be turned if it is not at an optimal angle.