Energy from the sun, stored in a liquid – and released on demand OR … Solar to Hydrogen Fuel … And the Winner Is?

“The solar energy business has been trying to overcome … challenge for years. The cost of installing solar panels has fallen dramatically but storing the energy produced for later use has been problematic.”

“In a single hour, the amount of power from the sun that strikes the Earth is more than the entire world consumes in an year.” To put that in numbers, from the US Department of Energy 

 

 

Each hour 430 quintillion Joules of energy from the sun hits the Earth. That’s 430 with 18 zeroes after it! In comparison, the total amount of energy that all humans use in a year is 410 quintillion Joules. For context, the average American home used 39 billion Joules of electricity in 2013.

Read About: What are the Most Efficient Solar Panels on the Market?

 

Clearly, we have in our sun “a source of unlimited renewable energy”. But how can we best harness this resource? How can we convert and  “store” this energy resource on for sun-less days or at night time … when we also have energy needs?

Now therein lies the challenge!

Would you buy a smartphone that only worked when the sun was shining? Probably not. What it if was only half the cost of your current model: surely an upgrade would be tempting? No, thought not.

The solar energy business has been trying to overcome a similar challenge for years. The cost of installing solar panels has fallen dramatically but storing the energy produced for later use has been problematic.

 

Now scientists in Sweden have found a new way to store solar energy in chemical liquids. Although still in an early phase, with niche applications, the discovery has the potential to make solar power more practical and widespread.

Until now, solar energy storage has relied on batteries, which have improved in recent years. However, they are still bulky and expensive, and they degrade over time.

Image: Energy and Environmental Science

Trap and release solar power on demand

A research team from Chalmers University of Technology in Gothenburg made a prototype hybrid device with two parts. It’s made from silica and quartz with tiny fluid channels cut into both sections.

 

The top part is filled with a liquid that stores solar energy in the chemical bonds of a molecule. This method of storing solar energy remains stable for several months. The energy can be released as heat whenever it is required.

The lower section of the device uses sunlight to heat water which can be used immediately. This combination of storage and water heating means that over 80% of incoming sunlight is converted into usable energy.

Suddenly, solar power looks a lot more practical. Compared to traditional battery storage, the new system is more compact and should prove relatively inexpensive, according to the researchers. The technology is in the early stages of development and may not be ready for domestic and business use for some time.

 

From the lab to off-grid power stations or satellites?

The researchers wrote in the journal Energy & Environmental Science: “This energy can be transported, and delivered in very precise amounts with high reliability(…) As is the case with any new technology, initial applications will be in niches where [molecular storage] offers unique technical properties and where cost-per-joule is of lesser importance.”

Image: REUTERS: Kessler

The team now plans to test the real-world performance of the technology and estimate how much it will cost. Initially, the device could be used in off-grid power stations, extreme environments, and satellite thermal control systems.

 

Editor’s Note: As Solomon wrote in  Ecclesiastes 1:9: “What has been will be again, what has been done will be done again; there is nothing new under the sun.”

Storing Solar Energy chemically and converting ‘waste heat’ has and is the subject of many research and implementation Projects around the globe. Will this method prove to be “the one?” This writer (IMHO) sees limited application, but not a broadly accepted and integrated solution.

Solar Energy to Hydrogen Fuel

So where does that leave us? We have been following the efforts of a number of Researchers/ Universities who are exploring and developing “Sunlight to Hydrogen Fuel” technologies to harness the enormous and almost inexhaustible energy source power-house … our sun! What do you think? Please leave us your Comments and we will share the results with our readers!

Read More

We have written and posted extensively about ‘Solar to Hydrogen Renewable Energy’ – here are some of our previous Posts:

Scientists using sunlight, water to produce renewable hydrogen power

 

 

Solar-Powered Hydrogen Fuel Cells

Researchers at Rice University are on to a relatively simple, low-cost way to pry hydrogen loose from water, using the sun as an energy source. The new system involves channeling high-energy “hot” electrons into a useful purpose before they get a chance to cool down. If the research progresses, that’s great news for the hydrogen […]

HyperSolar reaches new milestone in commercial hydrogen fuel production

HyperSolar has achieved a major milestone with its hybrid technology HyperSolar, a company that specializes in combining hydrogen fuel cells with solar energy, has reached a significant milestone in terms of hydrogen production. The company harnesses the power of the sun in order to generate the electrical power needed to produce hydrogen fuel. This is […]

Rice University Research Team Demonstrates Solar Water-Splitting Technology: Renewable Solar Energy + Clean – Low Cost Hydrogen Fuel

Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules. The technology, which is described online in the American Chemical Society journal Nano Letters, relies on a configuration of light-activated gold nanoparticles that harvest sunlight and transfer solar energy […]

NREL Establishes World Record for Solar Hydrogen Production

NREL researchers Myles Steiner (left), John Turner, Todd Deutsch and James Young stand in front of an atmospheric pressure MDCVD reactor used to grow crystalline semiconductor structures. They are co-authors of the paper “Direct Solar-to-Hydrogen Conversion via Inverted Metamorphic Multijunction Semiconductor Architectures” published in Nature Energy. Photo by Dennis Schroeder.   Scientists at the U.S. […]

NREL & Colorado School of Mines Researchers Capture Excess Photon Energy to Produce Solar Fuels

Photo shows a lead sulfide quantum dot solar cell. A lead sulfide quantum dot solar cell developed by researchers at NREL. Photo by Dennis Schroeder.

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a proof-of-principle photo-electro-chemical cell capable of capturing excess photon energy normally lost to generating heat. Using quantum […]

NREL & Colorado School of Mines Researchers Capture Excess Photon Energy to Produce Solar Fuels

Photo shows a lead sulfide quantum dot solar cell. A lead sulfide quantum dot solar cell developed by researchers at NREL. Photo by Dennis Schroeder.

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a proof-of-principle photoelectrochemical cell capable of capturing excess photon energy normally lost to generating heat.

Using quantum dots (QD) and a process called Multiple Exciton Generation (MEG), the NREL researchers were able to push the peak external quantum efficiency for hydrogen generation to 114 percent.

The advancement could significantly boost the production of hydrogen from sunlight by using the cell to split water at a higher efficiency and lower cost than current photoelectrochemical approaches.

Details of the research are outlined in the Nature Energy paper Multiple exciton generation for photoelectrochemical hydrogen evolution reactions with quantum yields exceeding 100%, co-authored by Matthew Beard, Yong Yan, Ryan Crisp, Jing Gu, Boris Chernomordik, Gregory Pach, Ashley Marshall, and John Turner.

All are from NREL; Crisp also is affiliated with the Colorado School of Mines, and Pach and Marshall are affiliated with the University of Colorado, Boulder.

Beard and other NREL scientists in 2011 published a paper in Science that showed for the first time how MEG allowed a solar cell to exceed 100 percent quantum efficiency by producing more electrons in the electrical current than the amount of photons entering the solar cell.

“The major difference here is that we captured that MEG enhancement in a chemical bond rather than just in the electrical current,” Beard said.

“We demonstrated that the same process that produces extra current in a solar cell can also be applied to produce extra chemical reactions or stored energy in chemical bonds.”

The maximum theoretical efficiency of a solar cell is limited by how much photon energy can be converted into usable electrical energy, with photon energy in excess of the semiconductor absorption bandedge lost to heat.

The MEG process takes advantages of the additional photon energy to generate more electrons and thus additional chemical or electrical potential, rather than generating heat. QDs, which are spherical semiconductor nanocrystals (2-10 nm in diameter), enhance the MEG process.

In current report, the multiple electrons, or charge carriers, that are generated through the MEG process within the QDs are captured and stored within the chemical bonds of a H2 molecule.

NREL researchers devised a cell based upon a lead sulfide (PbS) QD photoanode. The photoanode involves a layer of PbS quantum dots deposited on top of a titanium dioxide/fluorine-doped tin oxide dielectric stack.

The chemical reaction driven by the extra electrons demonstrated a new direction in exploring high-efficiency approaches for solar fuels.

Funds for the research came from the Department of Energy’s Office of Science.

NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

NREL: Nanoscale confinement leads to new all-inorganic perovskite with exceptional solar cell properties – Using Quantum Dots to Create Increased Solar Cell Efficiency: Colorado School of Mines

Ashley Marshall, Erin Sanehira and Joey Luther with solutions of all-inorganic perovskite quantum dots, showing intense photoluminescence when illuminated with UV light. Credit: National Renewable Energy Laboratory

Scientists with the Energy Department’s National Renewable Energy Laboratory (NREL) for the first time discovered how to make perovskite solar cells out of quantum dots and used the new material to convert sunlight to electricity with 10.77 percent efficiency.

The research, Quantum dot-induced phase stabilization of a-CsPbI₃ perovskite for high-efficiency photovoltaics, appears in the journal Science. The authors are Abhishek Swarnkar, Ashley Marshall, Erin Sanehira, Boris Chernomordik, David Moore, Jeffrey Christians, and Joseph Luther from NREL. Tamoghna Chakrabarti from the Colorado School of Mines also is a co-author.

In addition to developing quantum dot perovskite solar cells, the researchers discovered a method to stabilize a crystal structure in an all-inorganic perovskite material at room temperature that was previously only favorable at high temperatures. The crystal phase of the inorganic material is more stable in quantum dots.

Most research into perovskites has centered on a hybrid organic-inorganic structure. Since research into perovskites for photovoltaics began in 2009, their efficiency of converting sunlight into electricity has climbed steadily and now shows greater than 22 percent power conversion efficiency. However, the organic component hasn’t been durable enough for the long-term use of perovskites as a solar cell.

NREL scientists turned to quantum dots-which are essentially nanocrystals-of cesium lead iodide (CsPbI₃) to remove the unstable organic component and open the door to high-efficiency quantum dot optoelectronics that can be used in LED lights and photovoltaics. 

The nanocrystals of CsPbI₃ were synthesized through the addition of a Cs-oleate solution to a flask containing PbI₂ precursor. The NREL researchers purified the nanocrystals using methyl acetate as an anti-solvent that removed excess unreacted precursors. This step turned out to be critical to increasing their stability.

Contrary to the bulk version of CsPbI₃, the nanocrystals were found to be stable not only at temperatures exceeding 600 degrees Fahrenheit but also at room temperatures and at hundreds of degrees below zero. The bulk version of this material is unstable at room temperature, where photovoltaics normally operate and convert very quickly to an undesired crystal structure.

NREL scientists were able to transform the nanocrystals into a thin film by repeatedly dipping them into a methyl acetate solution, yielding a thickness between 100 and 400 nanometers. Used in a solar cell, the CsPbI₃ nanocrystal film proved efficient at converting 10.77 percent of sunlight into electricity at an extraordinary high open circuit voltage. The efficiency is similar to record quantum dot solar cells of other materials and surpasses other reported all-inorganic perovskite solar cells.

Explore further: Rubidium pushes perovskite solar cells to 21.6 percent efficiency

More information: A. Swarnkar et al. Quantum dot-induced phase stabilization of -CsPbI3 perovskite for high-efficiency photovoltaics, Science (2016). DOI: 10.1126/science.aag2700

Journal reference: Science

Provided by: National Renewable Energy Laboratory