ExtremeTech explains: How do solar cells work?

By Graham Templeton

There are really only two possible endpoints for human energy production, and they’re both fusion. Either we find a way to create tiny, controlled fusion reactions here on Earth (fusion power) or we find a way to usefully collect a good portion of the energy already being released form the enormous fusion reactor our solar system has built right in (solar power). The nice thing about the solar option is that it can come about incrementally, giving us partial utility while inching ever-closer to the tipping point, when it could provide for the majority of our electrical needs. But what is a solar cell, the centrally important component of solar power, and how does it work?

A solar cell, also called a photovoltaic cell, is defined as any device that can capture some of the energy of a photon of light, and pass that energy on to a device or storage medium in the form of electricity. Not all solar power is photovoltaic in nature, as some solar technologies collect the heat of absorbed photons, rather than their energy, directly. Still, with such a general definition, the term photovoltaics encompasses a wide variety of different technologies.

All of them have one thing in common, however: they use the energy of a photon to excite electrons in the cell’s semi-conducting material from a non-conductive energy level to a conductive one. What makes this complex is that not all photons are created equal. Light arrives as an unhelpful amalgamation of wavelengths and energy levels, and no one semi-conducting material is capable of properly absorbing all of them. This means that to increase the efficiency of capture of solar radiation, we have to make hybrid (“multi-junction”) cells that use more than one absorbing material.

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A Paper-Thin Solar Panel Can Charge Your Phone on the Go

By: Bryan Lufkin

Solar panels keep getting lighter and tinier—good news for rugged on-the-go types who can charge their devices on the trail with sun-fueled chargers. And this particular solar charger on Kickstarter is so thin, you can slip it in your Lonely Planet while it feeds your phone battery.

It’s called Solar Paper: 7.5 inches long, 3.5 wide, and .15 thin. There’s a .45-inch thick USB charging port at the top, which sticks out of your book like a bookmark that sucks in that precious sunlight.

One of these panels weights 4.5 ounces and equals 2.5 watts, and you can connect more panels with magnets for more power. In good weather, two connected panels can fully juice an iPhone 6 in about two-and-a-half hours. You can connect up to four foldable units for a total of 10 watts, capable of charging an iPad Air 2 to 100% in four hours.

A nifty feature is Solar Panel’s auto restart. With similar gadgets, a passing cloud or sudden shadow shuts the charger down, forcing manual reboot. But Solar Panel resets that automatically. You can use it to charge anything that connects with USB: GoPro, external batteries, Bluetooth speakers, digital cameras, and so on.

Developed by solar company Yolk, the project’s raked in over $320,000, way past its modest $50K goal. A month left of funding still remains. The team hopes to have the first batch deliverable by September.

The past couple years have welcomed a whole rucksack’s full of portable, solar-powered gear built for the outdoors: like flashlights, watches, and bikes. May as well put the giant star to good use.

Courtesy: http://gizmodo.com/

Unexpected Roof Design for Solar Panels in this Net Zero Home

Wow – what an unexpected roof design for the solar panels in this Net Zero home. Built in Seattle’s Columbia City neighborhood, this eco-friendly home is a combination of energy efficiency and pragmatic design. The rainy Pacific Northwest is not the easiest place to build a solar home. You can pretty much put your panels anywhere your heart desires in Phoenix, or Palm Springs, where the sun shines most days. But this is a real accomplishment – built by Dwell Development to maximize solar energy collection. The home is constructed with salvaged wood and corrugated metal. Practicing the Dwell Development philosophy, no material is wasted. Windows are triple pane and a Heat Recovery Ventilator provides constant fresh air. A modern home from reclaimed materials, with Net Zero impact. Everything old is new again – but this time, with staying power.

Courtesy: http://snip.ly/7U7B

Wind power generates 140% of Denmark’s electricity demand

Unusually high winds allowed Denmark to meet all of its electricity needs – with plenty to spare for Germany, Norway and Sweden too

The Conservative UK government has announced a withdrawal of support for onshore windfarms. Denmark’s windfarms have strong government backing. Photograph: Max Mudie/Alamy

By: Arthur Neslen

So much power was produced by Denmark’s windfarms on Thursday that the country was able to meet its domestic electricity demand and export power to Norway, Germany and Sweden.

On an unusually windy day, Denmark found itself producing 116% of its national electricity needs from wind turbines yesterday evening. By 3am on Friday, when electricity demand dropped, that figure had risen to 140%.

Interconnectors allowed 80% of the power surplus to be shared equally between Germany and Norway, which can store it in hydropower systems for use later. Sweden took the remaining fifth of excess power.

“It shows that a world powered 100% by renewable energy is no fantasy,” said Oliver Joy, a spokesman for trade body the European Wind Energy Association. “Wind energy and renewables can be a solution to decarbonisation – and also security of supply at times of high demand.”

The figures emerged on the website of the Danish transmission systems operator, energinet.dk, which provides a minute-by-minute account of renewable power in the national grid. The site shows that Denmark’s windfarms were not even operating at their full 4.8GW capacity at the time of yesterday’s peaks.

Wind surplus in Denmark

A surge in windfarm installations means Denmark could be producing half of its electricity from renewable sources well before a target date of 2020, according to Kees van der Leun, the chief commercial officer of the Ecofys energy consultancy.

“They have a strong new builds programme with a net gain of 0.5GW in new onshore windfarms due before the end of the decade,” he said. “Some 1.5GW from new offshore windfarms will also be built, more than doubling the present capacity. We’re seeing a year-on-year 18% growth in wind electricity, so there really is a lot of momentum.”

The British wind industry may view the Danish achievement with envy, after David Cameron’s government announced a withdrawal of support for onshore windfarms from next year, and planning obstacles for onshore wind builds.

Joy said: “If we want to see this happening on a European scale, it is essential that we upgrade the continent’s ageing grid infrastructure, ensure that countries open up borders, increase interconnection and trade electricity on a single market.”

Around three-quarters of Denmark’s wind capacity comes from onshore windfarms, which have strong government backing.

Courtesy: http://www.theguardian.com/

Solar Powered Family Car Generates More Energy Than It Uses

By Evan Ackerman

Photo: Bart van Overbeeke/TU Eindhoven

Solar powered vehicles, whether we’re talking about cars or airplanes, usually share the characteristic of perpetually almost falling apart. What I mean is, solar power is so close to not being usable that vehicles must be as light as possible, or they will not fly (or drive). Technology is improving, though, and it’s at the point where a team from the Eindhoven University of Technology has been able to create a solar powered car that manages to seat four while generating more energy over the course of the year than it uses to drive.

“Stella Lux” is an upgrade of Solar Team Eindhoven’s “Stella” solar powered family car, originally developed in 2013. Stella Lux is made primarily of carbon fiber and aluminum for a total weight of just 375 kg, and features a tunnel that runs through the bottom center of the car to improve aerodynamic efficiency. On the roof is a 5.8 square meter array of solar panels to feed the car and charge 15 kWh of onboard batteries, giving the car a fully charged range of about 1,100 km where it’s sunny (like in Australia) and 1,000 km where it’s not (the Netherlands). This range almost certainly goes down if you’re carting around three American-sized passengers, or if you push the car to its top speed of 125 km/h.

Photo: Bart van Overbeeke/TU Eindhoven

Inside, the car actually looks pretty comfy, despite the big tunnel down the middle. The seats and doors are integrated with each other to save weight while increasing interior space, and there’s some sort of mood lightning. The driver has access to a whole bunch of tactile controls with haptic feedback, and the navigation system is weather aware, able to plan the most efficient route by taking into account where the most sunlight can be found.

What might be most impressive about Stella Lux is that it’s energy positive: on average, the car uses less energy driving than it produces during the day, even in a place like the Netherlands where it’s not constantly sunny. Depending on weather, the daily range of the car on solar power alone varies between about 50 km and 300 km, and driving any less than the daily max solar range results in a surplus of energy that can be returned to the grid.

Photo: Bart van Overbeeke/TU Eindhoven

This October, Stella Lux will be competing in the the Cruiser Class of the Bridgestone World Solar Challenge, a 3,000 km race through the Australian Outback. And for a mere 10,000 Euro pledge to the team’s crowdfunding campaign, they’ll fly you to Australia to ride in Stella Lux yourself.

Courtesy: http://spectrum.ieee.org