Photovoltaics

A solar redox flow cell (SRFC). Image: University of Porto

Scientists in China evaluated the prospects for various approaches to integrating both solar generation and energy storage in a single device. Their work outlines several ways this could increase the efficiency of solar energy storage, and recommends that future research on this area should focus on integration of materials with the highest specific capacity for energy storage, alongside the dual function of solar energy harvesting.

From pv magazine

Maximizing the efficiency of energy storage, to make good use of every electron generated from intermittent renewables, will be an ongoing challenge for scientists over the coming decades, and one that will likely see a whole host of new technologies and materials introduced to increasingly specialized markets.

Among the less explored approaches here is single-device integrated solar generation and energy storage, or solar-powered redox batteries (SPRBs). These promise to eliminate much of the additional power electronics and other equipment needed to shuttle energy from a PV system to a battery, meaning both cheaper and more efficient energy storage. So far, a few different approaches to fabricating such a device have emerged, and while progress has been made, none has yet achieved the type of performance that would bring interest from commercial developers.

Scientists led by China’s Nanjing University of Information Science and Technology conducted an extensive review of recent progress with SPRBs, focusing on the development of high-performance dye sensitizer materials, the photoelectrochemical performance of different electrode materials, and the mechanism and structure of such devices. Their review and recommendations can be found in the paper Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future, published in Small.

The paper notes that dye sensitizer materials and semiconductor photocatalysts have shown the most promising results so far, and recommend a range of strategies focused on enhanced light absorption, charge separation, energy matching and overall device optimization. It also states that working with materials that exhibit a high specific capacity for energy storage will be key in developing commercially relevant types. If this potential can be realized, the review finds multiple applications including capacitors, solid-state batteries, microdevices, and smart wearables that could all benefit from such integrated technology.

Author: MARK HUTCHINS

Image: Doinkster, pixabay

In October there will be a partial solar eclipse in Central Europe. The Fraunhofer IEE has developed a solution that reportedly enables the most accurate forecast possible of the photovoltaic feed-in power during the extreme event.

From pv magazine

The more photovoltaic systems are installed, the more relevant are precise forecasts of how their feed-in will develop in the event of weather events such as solar eclipses. Extreme meteorological events in particular pose major challenges to secure network operation.

Researchers at the Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) in Germany have addressed this issue by developing a new forecast methodology that will soon be tested under real conditions. On October 25, in fact, there will be a partial solar eclipse in Central Europe, which will significantly reduce the photovoltaic feed-in. So far, such rare extreme events have not been routinely included in weather forecasts.

The scientists claim their solution is able to combine the degree of coverage specifically for location and time with all important weather forecasts. This would allow regional and local PV feed-in forecasts to be optimally adjusted in the future, with minimal errors.

Although the effect of the solar eclipse is slower and smaller than the influence of changing clouds, it still plays a significant role in the result. Volatile self-consumption also has a massive effect on the feed-in profile of photovoltaic systems, which can be forecast separately, according to the researchers.

Fraunhofer IEE validated its results with the data from the eclipse that occurred in Central Europe on June 10, 2021, in two steps: through ground-based measurement of global radiation based on data from German weather service DWD and feed-in measurements from thousands of photovoltaic power plants that are used for extrapolation and forecasting processes. The simulation also included weather forecasts and performance data from Fraunhofer IEE. The solution is also available as an algorithm or software for direct integration with the user.

The researchers are considering the proposed methodology as a tool to further strengthen the grid integration of renewable energy sources in Germany. For new locations or regions that have not yet been measured, an extrapolation process is possible by using current measurements from comparable areas and systems.

The October solar eclipse, with a 25% degree of coverage, will be about twice as strong as the result in June 2021, according to the researchers. Weather forecasts a few days beforehand are expected to provide information about cloud density and the effects the solar eclipse may ultimately have.

“In addition to the already good forecast models for the feed-in of individual photovoltaic parks or entire portfolios — including self-consumption — an important contribution can be made to avoiding or reducing errors,” said Rafael Fritz of Fraunhofer IEE.

Author: SANDRA ENKHARDT