Are Perovskites the Future of Solar PV?

By Sam Stranks

Perovskite-based solar cells. Image courtesy of Oxford University.
Perovskite-based solar cells. Image courtesy of Oxford University.

A new material has entered the emerging low-cost photovoltaics arena and is threatening to blow much of the existing competition away. Power conversion efficiencies (how efficiently incident sunlight is converted to electrical power) in perovskite-based solar cells have increased from a starting point of 3.8% in 2009 to a staggering 19.3% by May 2014. Such rapid improvement is unprecedented, and signs are promising for perovskite solar cells to very shortly exceed the efficiencies of established thin film technologies such as cadmium telluride (record certified efficiency 20.4%), CIGS (20.8%), and, more pertinently, to approach those of the market-dominating crystalline silicon solar cells (25%), all at a fraction of the cost. This breakthrough is a useful spark for the emerging PV field, and the excitement is widespread – so much so that the editors of the journal Science selected perovskite-based solar cells as runner-up for Breakthrough of the Year 2013, and the journal Nature highlighted these materials in their summary of what’s in store for science in 2014.

The perovskite family of materials is itself not new. Perovskite, named after Russian mineralogist Lev Perovski, refers to any material sharing the crystal structure of calcium titanate (CaTiO3), based on the general formula ABX3. When used in solar cells, A is typically a small carbon-based (organic) molecular cation, B is a metal ion such as lead, and X is a halide such as iodide, bromide or chloride. These “organo-metal halide” perovskites were studied extensively throughout the 1990s but were overlooked for solar cells until 2009, when researchers at the Toin University of Yokohama used these materials in liquid electrolyte dye-sensitised solar cells. However, the liquid electrolyte dissolved the perovskite, rendering the solar cells highly unstable. In 2012, our group in Oxford, at the same time as researchers at École polytechnique fédérale de Lausanne (EPFL) in Switzerland and Sungkyunkwan University in Korea, replaced the problematic liquid component with a stable solid-state version, paving the way for dramatic improvements in efficiency.

Organo-metal halide perovskites have several key advantages over traditional solar cell materials such as crystalline silicon, which generally require intensive, high-temperature processing. Firstly, these perovskites can be processed using very simple, low-cost methods – the perovskite precursor solution, containing a mixture of inexpensive salts, is simply cast onto the bottom electrode of the solar cell, heated gently to form the crystalline perovskite material, and sandwiched with a top electrode. This allows ‘printing’ of these solar cells using a large inkjet-style printer. We can also process them on flexible substrates, such as plastic or fabric, opening up a number of portable electronics applications. Using some tricks, we can make the solar cells semi-transparent enough to be used on window panes. Secondly, the constituent elements in the ABX3 crystal structure can be widely tuned to give a range of desired optical and electrical properties. Tweaking the halide composition, for example, allows the solar cell color to be tuned to any color of the rainbow. This gives them the huge advantage of being able to be fabricated in aesthetically-pleasing ways. This means consumers may be more willing to put them on their roofs, and building-integrated PV applications become attractive. They can even be processed as additional layers on top of established technologies such as silicon, where we can use their color tunability to harvest more of the solar spectrum and improve the current state-of-the-art panels.

While the applications are promising, there are a number of challenges these materials need to overcome before we see widespread deployment. We need to prove that these solar cells, assembled as modules, can last for several years under illumination and in the elements – the silicon industry standard is currently 20-30 years. These perovskites are particularly sensitive to moisture, so they need to be very well sealed from the atmosphere to prevent premature degradation. Presently there is insufficient stability data to indicate how long they will last, but ongoing laboratory tests on well-sealed devices under simulated sunlight over 1000s of hours are very encouraging. Another issue is the presence of trace amounts of lead in these materials. While it is perfectly possible to contain the lead throughout the entire life cycle of the panel, this low toxicological risk could still be problematic for the technology, particularly if policy stipulates against it. However, just last month both our group and researchers at Northwestern University reported the first lead-free (tin-based) perovskite solar cells, albeit with much lower stability and efficiency than their lead-based counterparts. These results are particularly promising for the technology, and with optimisation to improve stability and performance, we could see the tin analogues surpassing the lead-based materials.

With such an unprecedented increase in solar cell efficiency after only a few years of academic research, the future is certainly looking bright for these materials. The sky really does seem to be the limit – recent reports have shown that these perovskites can emit light very efficiently, also opening up light-emitting diodes (LEDs) and lasers as potential applications. By further exploiting their remarkable properties and improving their stability, we could see perovskites playing a major role in an electrified future world.

Dr Sam Stranks is a Junior Research Fellow at Worcester College, Oxford, and a Lecturer in Physics at Corpus Christi College, Oxford. He is currently working with Prof. Henry Snaith in the Department of Physics at the University of Oxford, and will commence a Marie Curie Fellowship at MIT in October 2014.

Image Credit: Oxford PV

This article, Perovskites: The Future of PV?, is syndicated from Clean Technica and is posted here with permission.

Indian Govt replacing 26 Mn Diesel Water Pumps with Solar Pumps

by Guest Contributor Jeff Spross.

Renewable Energy pumps water. The Indian government is aiming to swap out 26 million fossil-fuel-powered groundwater pumps for solar-powered ones.
Renewable Energy pumps water. The Indian government is aiming to swap out 26 million fossil-fuel-powered groundwater pumps for solar-powered ones. Image by Shutterstock

Originally published on ThinkProgress.

The pumps are used by farmers throughout the country to pull in water for irrigation, and currently rely on diesel generators or India’s fossil-fuel-reliant electrical grid for power.

Pashupathy Gopalan, the regional head of SunEdison, told Bloomberg that 8 million diesel pumps already in use could be replaced right now. And India’s Ministry of New and Renewable Energy estimates another 700,000 diesel pumps that could be replaced are bought in India every year.

“The potential is huge,” said Tarun Kapoor, the joint secretary at the ministry. “Irrigation pumps may be the single largest application for solar in the country.”

The program works by subsidizing the swap, and operates in different capacities in India’s various states, sometimes subsidizing the solar pumps up to 86 percent. Thanks to that aid, and the dramatic collapse in prices for solar power, the pumps pay themselves off in one to four years, according to Ajay Goel, the chief executive officer of Tata Power Solar Systems Ltd., a panel maker and contractor. And Stephan Grinzinger, the head of sales for a German solar water pump maker, told Bloomberg the economics will only get better: diesel prices will rise and spike during farming season, and economies of scale will help the swap program.

Two-thirds of India’s electricity is generated by coal, with natural gas and hydroelectric making up most of the rest. But the monsoon season is growing more erratic — likely due to climate change — making power from the hydroelectric dams less reliable as well. Coal is growing in economic cost for India, so power plants often sit idle, and the coal that is easy to reach would require displacing major population centers.

The national grid that relies on those fuels has seen few updates since it was constructed in they 1960s. It’s also under growing stress from India’s rising middle class, which is adopting air conditioning and running water in massive numbers — all in a country prone to heat waves, again thanks in part to climate change. As backup, many Indian residents and businesses rely on diesel generators, which leaves them vulnerable to the fuel market and contributes to fossil fuel emissions.

Even when the grid is working, around 300 million of India’s 1.2 billion inhabitants don’t have access to it. When it’s not, rolling blackouts are common. Many farmers are able to draw only four hours of power a day from the grid, and that often at night. Heat waves in 2013 were accompanied by widespread blackouts, and a two-day grid failure in 2012 left over 600 million Indians without power.

Ironically, thanks to the kind of distributed and sustainable generation the swap program represents, many of India’s rural poor actually faired much better during the blackout than the grid-dependent middle-class. It’s one of the strengths of solar in particular, even before climate change is considered: a more decentralized power system, based around “microgrids” and individual power generation, rather than a centralized system reliant on the good function of large, singular power providers. In India in particular, sunlight is most plentiful at the times when demand tends to peak. That leaves the power system more adaptable, less prone to central failures, and thus more hospitable to those still struggling to overcome poverty in particular.

Beyond India’s pump swap program, other efforts in south Asia and northern Africa are already underway to bypass grid expansion entirely, and bring solar power and microgrids directly to poor people.

Image Credit: solar water pump via Shutterstock

This article, Indian Government Aims For 26 Million Solar Water Pumps, is syndicated from Clean Technica and is posted here with permission.

Kyocera Stadium Goes Solar, Assists The Hague’s CO2 Neutral Goal

by Cynthia Shahan.

Renewable Energy at The KYOCERA Stadium in The Hague, Netherlands will come in the form of thousands of solar panels on the roof area of the stadium.
Renewable Energy at The KYOCERA Stadium in The Hague, Netherlands will come in the form of 2900 solar panels on the roof area of the stadium, giving an assist to The Hague’s goal of carbon neutrality by 2040.

Sports are thriving businesses for many communities and countries. Soccer is our family’s personal favorite. We are not alone — the game is the most popular in the world. The World Cup creates an influx of business for any country where it is held — this sport is the heart of many families and countries. It is important, of course, that such a large business move towards much greater use renewable energy and energy efficiency. Luckily, we’re seeing movements in that direction.

As we know, KYOCERA has been actively engaged in supplying solar modules to businesses, homes, and sports facilities around the world. According to a recent press release, it reports that the latest on a list of sports facilities around the world utilizing Kyocera solar modules is a soccer stadium in The Hague, Netherlands:

[T]he Kyocera Group announced that it is supplying 725 kilowatts of solar modules for the KYOCERA Stadium in The Hague, Netherlands. On January 22, the signing of a letter of intent in The Hague signaled the start of another major Kyocera solar project in connection with professional sports in Europe — after the Stade de Suisse in Bern, Switzerland. The roof of The Hague’s soccer stadium is to be equipped with 2,900 high-quality Kyocera solar modules.

This will of course help to lower greenhouse gas emissions, and it will contribute to The Hague’s plan to become carbon neutral by 2040. It will also help encourage residents and visitors to go solar themselves, an unquantifiable but important benefit. Here’s more on the news from KYOCERA:

Furthermore, the plans of the signatories, namely the city of The Hague, Kyocera Fineceramics GmbH, NV ADO Den Haag soccer club, Croon Elektrotechniek, Oskomera solar power solutions, Rabobank, Steeds and Vrolijk Technical Services, go further than just equipping the stadium roof with solar power: The system will become one of the largest building-based photovoltaic projects in the Netherlands — allowing CO2 emissions to be reduced by up to 272 tons a year and providing the equivalent electricity required by around 200 typical homes. That means the project will make a valuable contribution to The Hague’s plans to become carbon neutral by 2040.

The stadium is the home of the first-division Dutch soccer team ADO Den Haag and has a capacity of 15,000. In addition to soccer, the stadium is used for field hockey games. The construction work is set to take place this summer, immediately following the Hockey World Cup, which will use the stadium as a venue.

Kyocera set the standard for the use of solar technology in the sporting world in 2004 when it supplied 1.3 megawatts of solar modules for what was at the time the world’s largest stadium-based solar power generating system at the Stade de Suisse (home of the Swiss soccer team BSC Young Boys, and a venue for Euro 2008). The 8,000 solar modules installed there have since been producing an annual output of 1,124,045 kWh. The company has also supplied its solar modules to other sports facilities around the world, including the Townsville RSL Stadium in North Queensland, Australia; and the MAZDA Stadium in Hiroshima, Japan.

Read more KYOCERA news on CleanTechnica here:

Largest Solar Power Station In Japan Opened By Kyocera

Kyocera Supplies Solar Powered Generators to Medical Facility in Tajikistan

Kyocera Solar Modules Show Only 8.3% Performance Degradation After 20 Years

Kyocera Invests in Smart Home & Energy Technology Research

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This article, Kyocera Soccer Stadium In The Hague Goes Solar, Helps The Hague’s Goal Of Being Carbon Neutral By 2040, is syndicated from Clean Technica and is posted here with permission.

About the Author

Cynthia ShahanCynthia Shahan is an Organic Farmer, Classical Homeopath, Art Teacher, Creative Writer, Anthropologist, Natural Medicine Activist, Journalist, and mother of four unconditionally loving spirits, teachers, and environmentally conscious beings who have lit the way for me for decades.

13 Brilliant Energy Breakthroughs of 2013

by Guest Contributor Kiley Kroh.

Originally published on ThinkProgress.

While the news about climate change seems to get worse every day, the rapidly improving technology, declining costs, and increasing accessibility of clean energy are the true bright spots in the march towards a zero-carbon future. 2013 had more clean energy milestones than we could fit on one page, but here are thirteen of the key breakthroughs that happened this year.

1. Using salt to keep producing solar power even when the sun goes down. Helped along by the Department of Energy’s loan program, Solana’s massive 280 megawatt (MW) solar plant came online in Arizona this October, with one unique distinction: the plant will use a ‘salt battery’ that will allow it to keep generating electricity even when the sun isn’t shining. Not only is this a first for the United States in terms of thermal energy storage, the Solana plant is also the largest in the world to use to use parabolic trough mirrors to concentrate solar energy.

2. Electric vehicle batteries that can also power buildings.

Nissan Leaf shows Vehicle to Grid technology testing
Nissan’s groundbreaking ‘Vehicle-To-Building‘ technology will enable companies to regulate electricity by tapping into EV’s plugged into their parking areas. Image Credit: Nissan Leaf via Shutterstock.

Nissan’s groundbreaking ‘Vehicle-To-Building‘ technology will enable companies to regulate their electricity needs by tapping into EV’s plugged into their garages during times of peak demand. Then, when demand is low, electricity flows back to the vehicles, ensuring they’re charged for the drive home. With Nissan’s system, up to six electric vehicles can be plugged into a building at one time. As more forms renewable energy is added to the grid, storage innovations like this will help them all work together to provide reliable power.

3. The next generation of wind turbines is a game changer. May of 2013 brought the arrival of GE’s Brilliant line of wind turbines, which bring two technologies within the turbines to address storage and intermittency concerns. An “industrial internet” communicates with grid operators, to predict wind availability and power needs, and to optimally position the turbine. Grid-scale batteries built into the turbines store power when the wind is blowing but the electricity isn’t needed — then feed it into the grid as demand comes along, smoothing out fluctuations in electricity supply. It’s a more efficient solution to demand peaks than fossil fuel plants, making it attractive even from a purely business aspect. Fifty-nine of the turbines are headed for Michigan, and two more will arrive in Texas.

4. Solar electricity hits grid parity with coal. A single solar photovoltaic (PV) cell cost $76.67 per watt back in 1977, then fell off a cliff. Bloomberg Energy Finance forecast the price would reach $0.74 per watt in 2013 and as of the first quarter of this year, they were actually selling for $0.64 per watt. That cuts down on solar’s installation costs — and since the sunlight is free, lower installation costs mean lower electricity prices. And in 2013, they hit grid parity with coal: in February, a southwestern utility, agreed to purchase electricity from a New Mexico solar project for less than the going rate for a new coal plant. Unsubsidized solar power reached grid parity in countries such as Italy and India. And solar installations have boomed worldwide and here in America, as the lower module costs have drivendown installation prices.

5. Advancing renewable energy from ocean waves. With the nation’s first commercial, grid-connected underwater tidal turbine successfully generating renewable energy off the coast of Maine for a year, the Ocean Renewable Power Company (ORPC) has its sights set on big growth. The project has invested more than $21 million into the Maine economy and an environmental assessment in March found no detrimental impact on the marine environment. With help from the Department of Energy, the project is set to deploy two more devices in 2014. In November, ORPC was chosen to manage a wave-energy conversion project in remote Yakutat, Alaska. And a Japanese delegation visited the project this year as the country seeks to produce 30 percent of its total power offshore by 2030.

6. Harnessing ocean waves to produce fresh water.

This year saw the announcement of Carnegie Wave Energy’s upcoming desalination plant near Perth, Australia. It will use the company’s underwater buoy technology to harness ocean wave force to pressurize the water, cutting out the fossil-fuel-powered electric pumps that usually force water through the membrane in the desalination process. The resulting system — “a world first” — will be carbon-free, and efficient in terms of both energy and cost. Plan details were completed in October, the manufacturing contract was awarded in November, and when it’s done, the plant will supply 55 billion litters of fresh drinking water per year.

7. Ultra-thin solar cells that break efficiency records. Conversion efficiency is the amount of light hitting the solar cell that’s actually changed into electricity, and it’s typically 18.7 percent and 24 percent. But Alta Devices, a Silicon Valley solar manufacturer, set a new record of 30.8 percent conversion efficiency this year. Its method is more expensive, but the result is a durable and extremely thin solar cell that can generate a lot of electricity from a small surface area. That makes Alta’s cells perfect for small and portable electronic devices like smartphones and tablets, and the company is in discussions to apply them to mobile phones, smoke detectors, door alarms, computer watches, remote controls, and more.

8. Batteries that are safer, lighter, and store more power. Abundant and cost-effective storage technology will be crucial for a clean energy economy — no where more so than with electric cars. But right now batteries don’t always hold enough charge to power automobiles for extended periods, and they add significantly to bulk and cost. But at the start of 2013, researchers at Oak Ridge National Laboratory successfully demonstrated a new lithium-ion battery technology that can store far more power in a much smaller size, and that’s safer and less prone to shorts. They used nanotechnology to create an electrolyte that’s solid, ultra-thin, and porous, and they also combined the approach with lithium-sulfur battery technology, which could further enhance cost-effectiveness.

9. New age offshore wind turbines that float. Offshore areas are prime real estate for wind farms, but standard turbines require lots of construction and are limited to waters 60 meters deep or less. But Statoil, the Norwegian-based oil and gas company, began work this year on a hub of floating wind turbines off the coast of Scotland. The turbines merely require a few cables to keep them anchored, and can be placed in water up to 700 meters. That could vastly expand the amount of economically practical offshore wind power. The hub off Scotland will be the largest floating wind farm in the world — and two floating turbines are planned off the coast of Fukushima, Japan, along with the world’s first floating electrical substation.

10. Cutting electricity bills with direct current power.

New USB technology
New USB technology will be able to deliver 100 watts of power, spreading DC power to more low voltage personal electronics.

Alternating current (AC), rather than direct current (DC) is the dominant standard for electricity use. But DC current has its own advantages: its cheap, efficient, works better with solar panels and wind turbines, and doesn’t require adapters that waste energy as heat. Facebook, JPMorgan, Sprint, Boeing, and Bank of America have all built datacenters that rely on DC power, since DC-powered datacenters are 20 percent more efficient, cost 30 percent less, and require 25 to 40 percent less floorspace. On the residential level, new USB technology will soon be able to deliver 100 watts of power, spreading DC power to ever more low voltage personal electronics, and saving homes in efficiency costs in their electricity bill.

11. Commercial production of clean energy from plant waste is finally here. Ethanol derived from corn, once held up as a climate-friendly alternative to gasoline, is under increasing fire. Many experts believe it drives up food prices, and studies disagree on whether it actually releases any less carbon dioxide when its full life cycle is accounted for. Cellulosic biofuels, promise to get around those hurdles, and 2013 may be when the industry finally turned the corner. INOES Bio’s cellulosic ethanol plant in Florida and KiOR’s cellulosic plant in Mississippi began commercial production this year. Two more cellulosic plants are headed for Iowa, and yet another’s being constructed in Kansas. The industry says 2014′s proposed cellulosic fuel mandate of 17 million gallons will be easily met.

12. Innovative financing bringing clean energy to more people. In DC, the first ever property-assessed clean energy (PACE) project allows investments in efficiency and renewables to be repaid through a special tax levied on the property, which lowers the risk for owners. Crowdfunding for clean energy projects made major strides bringing decentralized renewable energy to more people — particularly the world’s poor — and Solar Mosaic is pioneering crowdfunding to pool community investments in solar in the United States. California figured out how to allow customers who aren’t property owners or who don’t have a suitable roof for solar — that’s 75 percent of the state — to nonetheless purchase up to 100 percent clean energy for their home or business. Minnesota advanced its community solar gardens program, modeled after Colorado’s successful initiative. And Washington, DC voted to bring in virtual net metering, which allows people to buy a portion of a larger solar or wind project, and then have their portion of the electricity sold or credited back to the grid on their behalf, reducing the bill.

13. Wind power is now competitive with fossil fuels. “We’re now seeing power agreements being signed with wind farms at as low as $25 per megawatt-hour,” Stephen Byrd, Morgan Stanley’s Head of North American Equity Research for Power & Utilities and Clean Energy, told the Columbia Energy Symposium in late November. Byrd explained that wind’s ongoing variable costs are negligible, which means an owner can bring down the cost of power purchase agreements by spreading the up-front investment over as many units as possible. As a result, larger wind farms in the Midwest are confronting coal plants in the Powder River Basin with “fairly vicious competition.” And even without the production tax credit, wind can still undercut many natural gas plants. A clear sign of its viability, wind power currently meets 25 percent of Iowa’s energy needs and is projected to reach a whopping 50 percent by 2018.

This article, 13 Huge Clean Energy Breakthroughs Of 2013, is syndicated from Clean Technica and is posted here with permission.

Natcore Will Make Black Silicon Solar Cells Cheaper

by Tina Casey.

Natcore Technology solar cells
Prices for renewable energy in 2013 continue to fall. Natcore Technologies creates new wafers at lower cost which will help to lower renewable energy costs in the near future.

The solar company Natcore Technologies is set to take a huge bite out of the cost of producing solar cells while reducing the amount of manufacturing-related hazardous effluents. The key is a new low temperature laser process that Natcore plans to introduce, which will eliminate the need for a high temperature diffusion furnace.

Natcore has been working with the National Renewable Energy Laboratory and other partners to perfect its black silicon technology. Just around this time last year it announced that it completed the design of a complete low-cost black silicon solar cell production system at its New York facility, resulting in the potential for a 23.5 percent cut production costs according to an independent study cited by Natcore.

The Road To Super Cheap Black Silicon Wafers

The laser system could result in even greater savings.

In conventional solar cell manufacturing, materials are added to the surface of the cell (a process called doping) by melting them on in a furnace, which involves a considerable amount of waste heat. Typically, the furnace reaches temperatures of up to 900 degrees centigrade.

In contrast, laser doping focuses all of its energy on localized points. It takes less than a millisecond, wasting far less energy and minimizing the risk of damaging the solar cell.

According to Natcore officials, the process will also eliminate hazardous materials used in the conventional production process, including silane and phosphorous oxychloride.

Natcore isn’t saying what laser it is using, but it has identified a company that it is working with to custom-make a system for their R&D facility.

Don’t Forget Black Metals!

Black silicon refers to silicon wafers etched with billions of nano-sized holes per square inch. That creates a new level of efficiency, as described by NREL:

The holes and silicon walls are smaller than the light wavelengths hitting them, so the light doesn’t recognize any sudden change in density at the surface and, thus, don’t reflect back into the atmosphere as wasted energy. The researchers controlled the nanoshapes and the chemical composition of the surface to reach record solar cell efficiencies for this ‘black silicon’ material.

The wafer is not actually colored black, but the nanoholes make it appear darker. It’s worth noting, by the way, that Natcore has some competition in this area, for example from Germany’s Fraunhofer-Gesellschaft institute.

Meanwhile, researchers at Lawrence Livermore National Laboratory have been working on a “black metals” process that deploys the plasmonic effect to harvest energy from a greater span of the solar spectrum.

The basic concept is similar to black silicon, but instead of using nanoholes, the structures in black metal are pillar-like nanofilaments.

Projects like these demonstrate that solar tech has yet to find its bottom cost, as efficiencies continue to rise and production costs fall.

As for the “soft costs” of a solar installation including labor and third-party financing, those are also being addressed by new Department of Energy initiatives such as the Most Affordable Rooftop Solar Prize.

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This article, Natcore Aims To Make Black Silicon Solar Cells Even Cheaper, is syndicated from Clean Technica and is posted here with permission.

About the Author

Tina CaseyTina Casey Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. You can also follow her on Twitter @TinaMCasey and Google+.