Six-hundred million people in Sub-Saharan Africa lack access to electricity. To meet these power needs, a mix of large public-run utility grids and standalone systems will be necessary for universal access in the region. Governments, aid organizations, and scientists are working to understand which electricity grid solution would be most cost-effective and reliable across urban, peri-urban, and rural areas.

Standalone, or “decentralized” electricity systems—most often solar power with battery storage—are usually thought to be too expensive compared to large state-run grids in all but the most remote locations. However, declining costs of solar and new battery technologies are changing the best pathways to deliver reliable power to people that currently lack access to electricity. New UC Berkeley research published today in Nature Energy finds that decentralized electricity systems in sub-saharan Africa can be designed for extremely high reliability, and that this may come at remarkably low costs in the future.

Jonathan Lee, a Ph.D. candidate in the Energy and Resources Group (ERG) and Associate Professor Duncan Callaway worked with more than 10 years of solar data from NASA and developed an optimization model that determines the lowest cost way to build a standalone system given component costs and a target reliability. At current costs, their model indicates that most regions in Sub-Saharan Africa can get 95% reliable power—meaning customers can use electricity from some combination of solar panels and batteries 95% of the time—for roughly USD$0.40 per kWh. Though that cost is high relative to current grid costs, their model indicates that with aggressive but plausible future cost declines in decentralized system costs, largely in batteries, these costs would drop to levels competitive with the grid in many parts of the continent in less than a decade.

Solar energy has long been considered the most sustainable option for replacing our dependence on fossil fuels, but technologies for converting solar energy into electricity must be both efficient and inexpensive.

Scientists from the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) believe they’ve found a winning formula in a new method to fabricate low-cost high-efficiency solar cells. Prof. Yabing Qi and his team from OIST in collaboration with Prof. Shengzhong Liu from Shaanxi Normal University, China, developed the cells using the materials and compounds that mimic the crystalline structure of the naturally occurring mineral perovskite. They describe their technique in a study published in the journal Nature Communications.

In what Prof. Qi refers to as “the golden triangle,” solar cell technologies need to fulfill three conditions to be worth commercializing: their conversion rate of sunlight into electricity must be high, they must be inexpensive to produce, and they must have a long lifespan. Today, most commercial solar cells are made from crystalline silicon, which has a relatively high efficiency of around 22%. Though silicon, the raw material for these solar cells, is abundant, processing it tends to be complex and shoots up the manufacturing costs, making the finished product expensive.

New insight into how a certain class of photovoltaic materials allows efficient conversion of sunlight into electricity could set up these materials to replace traditional silicon solar cells. A study by researchers at Penn State reveals the unique properties of these inexpensive and quick-to-produce halide perovskites, information that will guide the development of next generation solar cells. The study appears September 27 in the journal Chem.

“Since the development of silicon solar cells, which today can be found on rooftops and roadsides, researchers have sought new types of photovoltaic materials that are easier to process into solar cells,” said John Asbury, associate professor of chemistry at Penn State and senior author of the study. “This is because construction of silicon solar cells is complex and hard to scale-up to the level that would be needed for them to generate even 10 percent of our total demand for electricity.”

Because of these complications, researchers have been searching for less expensive alternatives to silicon solar cells that can be processed more quickly. They are particularly interested in materials that can be processed using a technique called roll-to-roll manufacturing, a technique similar to those used to print newspapers that enables low-cost, high-volume production. Such materials must be processed from solution, like ink printed on a page.

Scientists in the United States and Saudi Arabia have harnessed the abilities of both a solar cell and a battery in one device—a “solar flow battery” that soaks up sunlight and efficiently stores it as chemical energy for later on-demand use. Their research, published September 27 in the journal Chem, could make electricity more accessible in remote regions of the world.

While sunlight has increasingly gained appeal as a clean and abundant energy source, it has one obvious limitation—there is only so much sunlight per day, and some days are a lot sunnier than others. In order to keep solar energy practical, this means that after sunlight is converted to electrical energy, it must be stored. Normally this takes two devices—a solar cell and a battery—but the solar flow battery is designed to perform like both.

“Compared with separated solar energy conversion and electrochemical energy storage devices, combining the functions of separated devices into a single, integrated device could be a more efficient, scalable, compact, and cost-effective approach to utilizing solar energy,” says Song Jin, a professor of chemistry at the University of Wisconsin-Madison. Jin and his team developed the device in collaboration with Jr-Hau He, a professor of electrical engineering at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

At today’s EU PVSEC conference, imec—the world-leading research and innovation hub in nanoelectronics, energy and digital technology and partner in EnergyVille—announced that its latest generation of large-area monofacial screen-printed rear-emitter nPERT cells feature a conversion efficiency of 23.03 percent, certified by Fraunhofer ISE CalLab. The nPERT (n-type Passivated Emitter and Rear Totally diffused) solar cells are made using an industry-compatible screen-printing process that has been designed as an upgrade of conventional pPERC (p-type Passivated Emitter and Rear Cell) processes. According to imec, its nPERT technology is projected to reach 23.5 percent efficiency by the end of this year, and there is a clear technology roadmap to eventually surpass 24 percent.

While p-type PERC solar cells are becoming mainstream in the PV industry, n-type PERT technology is being developed as a cost-effective contender that has a number of inherent advantages: Due to the absence of B-O complexes, n-type cells don’t suffer from light induced degradation (LID) and are less sensitive to metal impurities. That makes for cells that have the potential for a longer-term stability and a higher efficiency. Imec fabricated the M2-sized cells (area: 244.3 cm²) on its pilot line with industry-compatible tools and recipes, in a process that is an upgrade of the pPERC fabrication process, using a similar layout of an n+ region (Front Surface Field) on the illuminated side and a p+ region (as rear emitter) on the opposite side and adding a cost-effective boron diffusion.

“Until now, nPERT solar technology has not yet found the traction it deserves in the industry,” says Loic Tous, senior researcher at imec. “With these ever-improving results, which we achieved by applying knowledge gained from our bifacial nPERT project, we are now demonstrating the potential of nPERT technology. The advantages in stability and efficiency potential over p-type PERC cells, while using the same equipment with the addition of a Boron diffusion, make this a very promising technology for future manufacturing lines.”

Ready-made snap-together solar panels that turn waste heat into hot water are being developed at Brunel University London in a £10 million sustainable energy scheme starting next month.

With energy use in buildings predicted to double or even triple by 2050, and most home energy used to heat water, project PVadapt promises to crack several sustainable energy problems at once.

Funded by Horizon 2020, the three and a half-year multi-disciplinary project aims to perfect a flexible solar powered renewable energy system that generates both heat from hot water and electricity.