Indian Scientists Could Have Just Developed the Building Block of Optical Computing

By: Dinesh C Sharma

In a development that could boost optical or light-based computing, a group of Indian scientists has developed a photodetector device by integrating sheets of nanomaterials with silicon. The device could be used to develop a switch for optical computing and could also make silicon solar cells more efficient.

Computers, at present, use electronic circuits consisting of transistors – tiny devices which act like an on/off switch for streams of electrons. This is called binary switching. In the same way, optical computing works on switches that get activated with light or beams of photons. Developing a photodetector that works with a wide range of light has engaged scientists in recent years.

Representative Image.

Scientists at the CSIR-National Physical Laboratory (NPL) in New Delhi have now developed a photodetector that can operate over a broadband range of light (250 to 1650 nanometers) and displays binary photoswitching behavior over a similar range 250 to 1350 nanometers. Such high-performance level for a multifunctional photodetector has been achieved for the first time, researchers have claimed in their study published in journal Advanced Optical Materials.

At the core of the photodetector is a new class of semiconducting material called graphitic carbon-nitride. Scientists at NPL integrated ultrathin nanosheets of graphitic carbon-nitride with silicon. Though graphitic carbon-nitride is projected as next-generation material for energy harvesting devices, storage, photo-catalyst and optoelectronic applications, its full understanding and its integration with silicon are in its infancy.

“We have tried to overcome this bottleneck by ultra-thinning graphitic carbon-nitride using a versatile and low-cost technique of ultrasonic exfoliation. The ultrathin graphitic carbon-nitride was then integrated with surface modified silicon substrate via two-stage etching process,” explained Dr Prabir Pal and Dr Suraj P. Khanna, who jointly led the research team, while speaking to India Science Wire.

The process involved using ultrasonication to achieve critical structural rearrangement with a high degree of exfoliation in graphitic carbon-nitride nanosheets. This enhanced light absorption capabilities of the material added by Dr Surinder P. Singh and Dr H. K. Singh, members of the research team.

The light absorption was significant over a broad range of spectrum due to reduced dimensionality and large specific area of graphitic carbon-nitride. The overall result was a detector with high photosensitivity as compared to the commercially available counterparts. The device also displayed a novel binary photoswitching (change in current from positive to negative) in response to off/on light illumination. Researchers said the device could be further modified for integration in light-based processors.

“The seamless integration of graphitic carbon-nitride with silicon means it can also be utilized for enhancing the performance of existing energy harvesting devices,” said Dr Khanna.

The research team included Nisha Prakash, Gaurav Kumar, Manjri Singh, Arun Barvat, Prabir Pal, Surinder P. Singh, H. K. Singh, and Suraj P. Khanna. The research work was supported by NPL, University Grants Commission and Department of Science and Technology (DST) Start-Up Research Grant (Young Scientists) of Science and Engineering Research Board (SERB).


Tiny Wolfhagen, Germany Leads The Country’s Green Energy Transition

By: Austin Davis

Because of renewable energy sources, Wolfhagen, Germany, with 14,000 inhabitants, is able to generate about 106 percent of the its electricity needs throughout the year. The surplus is sold to neighborhing communities, and Wolfhagen’s residents receive dividends from the sale of the electricity. Credit: Austin Davis/PRI

With its centuries-old timber-framed houses and cobblestone lanes, Wolfhagen could easily illustrate a Grimm Brothers’ fable.

But for all of its medieval charm and pastoral feel, this town of 14,000 near Frankfurt has taken a big step into the future over the past few years. It has embraced Germany’s push to get rid of most fossil fuels and use 100 percent green energy instead — ahead of almost everyone else in the country.

Wolfhagen is an example of a community that took its energy future into its own hands and did what many other communities in Germany and around the world are struggling to do: be self-reliant and sustainable.

“We’re definitely further along than others,” said Reinhard Schaake, the mayor of Wolfhagen since 1999. “But I think that Wolfhagen shows that this energy transition can actually work.”

In the 1970s and 1980s, the global gas crisis and the disaster at the Chernobyl nuclear reactor caused a rethink in Germany and elsewhere regarding reliance on gas and nuclear power. The seeds of an idea to go fully renewable took hold and eventually became known as the Energiewende, or “energy transition.”

In this period, calls to phase out nuclear energy grew — Germany stopped building nuclear reactors and the first quasi-subsidies for solar and wind energy were introduced. A decade later, the country enshrined firm goals into law for how much green energy should make up the total percentage of energy used: By 2050, for example, Germany must get at least 80 percent of its electricity from solar, wind and other renewables. It must also decrease greenhouse gas emissions by at least 85 percent by 2050 from 1990 levels.

In 2003, Wolfhagen started taking those goals to heart.

Wolfhagen boasts four windmills, a 42,000-panel solar farm and two biogas facilities that turn waste into energy. Credit: Austin Davis/PRI

Town officials say they wanted residents to become directly involved in producing their own electricity. They also wanted the profits from electricity sales not to flow to a big energy company but rather to be reinvested into local schools, sports halls and other city works.

The plan was to be self-sufficient — and 100 percent green in a decade or so.

“We all developed the philosophy that we don’t just want to maximize profits as an energy producer selling electricity,” said Alexander Rohrssen, the chief executive of Stadtwerke Wolfhagen, the town-owned power plant. “Rather, we want to offer residents and customers the opportunity to get involved in the economics of the operation, all while saving energy.”

Town officials therefore jumped at the opportunity to Read more »

Newcastle Says Summerhill Solar Farm Will Save It Millions

By: Ian Kirkwood

SUNNY DAYS: An artist’s impression of Newcastle council’s Summerhill solar array, with an Ausgrid electrical substation in the right foreground.

When Newcastle City Council announced its Summerhill solar array, I initially wondered whether it was core business for a council to operate a power station, whether it was solar or not.

I knew that household solar panels were financially viable, meaning that larger ones should be just as cost-effective, given economies of scale. But I still wondered if the council would really save the claimed $250,000 to $350,000 a year on power bills, given a capital cost of $8 million, including $6.5 million borrowed from the federal government’s Clean Energy Finance Corporation, admittedly at an (undisclosed) low interest rate.

It seemed a bit too good to be true, and I was not the only one to think this way. Non-Labor councillors Brad Luke, Kath Elliott and John Church all had doubts about the project, which were expressed in council and covered in an article I wrote in March.

But after meeting with the council expert in charge of the project, Adam Clarke, and having as many questions as I could think of answered, it seems as though the council’s money is being well spent.

Of course there are no guarantees in life – or business – but if the predictions at the heart of a final, independent business case prove correct, then the council will indeed make its promised savings, and produce clean, green electricity along the way.

Clarke acknowledges there was scepticism within some parts of the council when work on the project began three years ago. He said an internal business case done in late 2015 looked promising, so a feasibility study was done after that, followed by the final independent business case in May 2017 and a follow-up version in November, which found an even stronger financial basis for going ahead.

The council’s consultants are a Brisbane firm called Resource Analytics, which describes itself as specialising in financial modelling for local government.

Resource Analytics’ website says: “Resource Analytics assisted in undertaking the financial feasibility study for a 5 megawatt photo-voltaic system for the City of Newcastle located at their Summerhill landfill site. This includes the preparation of financial assessment models, contribution to the expression of interest procurement process, and the evaluation of market information to determine project viability.”

The 14,500-plus panels in the Summerhill solar array (covering five hectares) are predicted to produce about half of the council’s electricity needs.

 But don’t solar arrays only work when the sun is shining? And what about the council’s night time power needs, which are apparently larger than in daytime, thanks to more than 14,000 street lights?

Well, this is where electricity trading comes in. Modelling predicts the solar array will produce more power during the day than the council consumes. This extra power will be sold into the grid, making money as well as removing the need to pay that day-time power bill. And as the streetlights are on during the night, the council already gets this power at mostly off-peak rates, which are cheaper than peak or shoulder power prices.

All up, the council consumed 14.1 gigawatt-hours of electricity in the 2015-16 year used in the report. Half of this amount, or 7.1 gigawatt-hours, was used by streetlights.  By time of use, peak and shoulder periods accounted for about 3.1 gigawatt-hours each, with 7.9 gigawatt-hours consumed off-peak.

The power output characteristics of solar cells are now well known, and detailed estimates provided by companies bidding for the job (won by Carnegie Clean Energy and Lendlease) indicate Summerhill will initially produce more than 7.1 gigawatt-hours a year of electricity, mostly in peak or shoulder periods.

Solar cells, like anything else left out in the wind and rain, will tend to deteriorate, but the report says all major manufacturers guarantee the output of their panels will be 80 per cent or more after 25 years and “typically higher, closer to 90 per cent in some cases”.

Anyone who’s ever tried to claim a warranty on something 25 years old might question that assumption but the report points out that the plant can be sold at “any point in its lifespan” and that there is a ready market for solar plants with reliable cash flows from pension funds and other asset managers.

As is standard practice for infrastructure projects, the consultants use “net present value” (NPV) methodology to calculate costs and benefits. NPV is a theoretical measure, as the consultants note: “This approach sets out the cash flow of capital and operating costs in 2017 dollars for each option over the modelled period (of 25 years) and then, utilising the principles of discounting and allowing for inflation, reduces the cost to a single present value to represent the whole-of-life cost.”

The May report said the council would save $5.9 million over 25 years “compared to a continuation of existing electricity supply arrangements (‘business as usual’)”. This saving is “after council has recouped all costs associated with construction, operation and financing of the project”. This amount is the saving that comes up the most when a “simulation analysis” is done on the project by putting it and the other parameters involved through 10,000 runs of a computer program. The “mean” or middle saving produced by this program was $7.1 million.

When the figures were re-run in November, using updated parameters, the new most likely saving was $7.8 million and the mean saving $8.9 million over 25 years.

The analysts say cash flow analysis “underpins the view” that the project was “self financing”, although that assumption was based on “any excess cash generated versus business-as-usual” is placed in reserve”.

A “summary analysis” shows how the original $5.9 million saving was arrived it. The cost of 25 years of power, without the project, is put at $20.1 million. If the project was built, the council would still pay $10.8 million (because the plant only generates half the council’s needs). When the sale of excess electricity, revenue from carbon certificates and an end-of-life sale price are added in, and the cost of building, operating and maintaining the plant and the costs of electricity trading are subtracted, the total costs come to $14.2 million, which is $5.9 million less than the $20.1 million business as usual figure.

As I noted, these are not actual dollar amounts. They are estimates obtained by using a number of theoretical variables, from the weather (sunshine or “irradiance” data to help calculate electricity output), historical electricity usage, power prices (peak, shoulder, off-peak, as well as spot and pool prices) and carbon certificate prices: and not just now, but for the next 25 years.

Time will tell whether the predicted savings eventuate.

The analysts say their work “does not price any additional economic, social or environmental benefit” that could flow from the project but they note that Summerhill helps the council reach its target of 30 per cent low-carbon electricity by 2020, and to cut its carbon footprint by 30 per cent on 2008/09 levels.

Work will start on site shortly.




Solar Powered Desalination Plant Brings Relief To Muni

Image: Stock

By: Nicolette Pombo-van Zyl

South Africa is set to commission its first solar powered desalination plant at the end of October 2018 in Witsand, Hessequa Municipality in the Western Cape.

The project, initiated by Prof Erwin Schwella, Professor of Public Leadership at Stellenbosch and Tilburg Universities together with the municipality, is co-funded by the Western Cape Government through the drought relief fund, and by the French Treasury, through a fund dedicated to the implementation of innovative green technologies.

In this municipality 250km east of drought-stricken Cape Town, several coastal villages are suffering from a structural water deficit, even outside of drought periods.

The plant will produce 100kl of fresh water per day powered solely by solar energy to address the normal local water requirement. The plant offers the possibility to supply drinking water besides sunlight hours through the connection to the local electricity grid.

The desalination plant will be specifically used to address the December holiday peak period with a daily production capacity increased to 300kl.

Zero Emissions for Desalination Plant

The technology, OSMOSUN, is developed by French-based Mascara Renewable Water and brought to South Africa by their local partner TWS-Turnkey Water Solutions. It is the world’s first reverse osmosis desalination technology coupled with photovoltaic solar energy without batteries, designed to supply coastal or borehole-dependent communities, with drinking water at a competitive price and without CO2 emissions.

An intelligent system of membranes enables the plant to cope with variations in solar power availability: all parameters are instantly optimised to ensure the best energy performance and simultaneously to guarantee the maximum lifetime of both installation and membranes.

Hessequa municipality’s Executive Mayor, Grant Riddles, said: “The shortage of water in the Western Cape is a harsh reality and only by implementing preventative measures, Hessequa municipality will be able to create water resource stability in our region.

“The Municipality is utilising innovative ideas in combating the effects of climate change, by taking the frontrunner approach in establishing public-private intergovernmental relationships and joint ventures. These partnerships will ensure a green economy that aims at reducing environmental risks and ecological scarcities.”

The project not only constitutes a highly innovative model in terms of Franco-South African cooperation, but its sustainable and decentralised production of drinkable water could be replicated in a highly cost-effective manner for communities along the South African coastline, as well as inland, anywhere with sufficient brackish water available.


‘Green’ Concrete Could Be Game-Changer For Construction Industry

Microscopic flakes of graphene add strength and durability — but also raise cost and safety concerns.


By: Kate Baggaley

Adding graphene to concrete makes it stronger and greenerDimitar Dimov (University of Exeter and Cast)

Scientists have been tinkering with concrete in an effort to improve upon the world’s most widely used construction material — and they’ve notched some notable successes.

New forms of concrete can trap and store the greenhouse gas carbon dioxide, break down pollutants from exhaust fumes, and help protect aging infrastructure by sealing cracks as they form. And now scientists in the U.K. have developed a “green” concrete that they say is more environmentally friendly than the ordinary stuff, as well as more durable and more than twice as strong.

“We were not expecting it to be that strong,” said Prof. Monica Craciun, a professor of nanoengineering at the University of Exeter and a member of the research team responsible for the new material. She called the material an “absolute game-changer” in a written statement and said a university-affiliated startup to sell it could be launched by year-end — although other experts gave a more measured assessment of the material’s immediate commercial potential.

The new form of concrete looks like ordinary concrete but gets its special properties from the addition of microscopic flakes of graphene, a form of carbon that is one of the world’s strongest materials. Greater strength means less of the stuff would be needed to construct walls and other structures. That’s significant since making cement — concrete’s principal ingredient — accounts for 5 percent of global emissions of the greenhouse gas carbon dioxide.

And if walls and other components of buildings can be made thinner, new design possibilities open up for architects and builders who work with concrete.

Craciun said the concrete-graphene composite is four times more resistant to water infiltration than ordinary concrete — suggesting that buildings and infrastructure made of it might stand up better over time, especially in flood zones. The composite material is also more elastic than ordinary concrete, meaning it might be a better choice for construction projects in areas prone to earthquakes.

And as a better conductor of electricity than its conventional counterpart, the composite material might find surprising new applications. Craciun envisions roadways whose surfaces could be electrified so they heat up to melt snow and ice.

Dr. Franz-Josef Ulm, faculty director of the Concrete Sustainability Hub at MIT, thinks walls made of electrically conductive concrete could serve as batteries to store electrical energy captured by solar panels. “Concrete is everywhere in your wall systems and floors,” he said. “Why not use that as an active battery?”

But Ulm expressed doubts about the commercial viability of the concrete-graphene composite, predicting that because of the high cost of graphene it was more of a “concept material” than one that would soon come to market.

Dr. Rackel San Nicolas, a civil engineer at the University of Melbourne in Australia and an expert on advanced construction materials, echoed Ulm’s assessment. “I don’t believe it is something that is ready to go right now,” she said of the new material in an email to NBC News MACH. Additional research is needed, she said, including studies to determine whether the tiny graphene particles would pose any health or environmental risks.