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A German research team has developed a tandem solar cell that reaches 24 percent efficiency – measured according to the fraction of photons converted into electricity (i.e. electrons). This sets a new world record as the highest efficiency achieved so far with this combination of organic and perovskite-based absorbers. The solar cell was developed by Professor Dr. Thomas Riedl’s group at the University of Wuppertal together with researchers from the Institute of Physical Chemistry at the University of Cologne and other project partners from the Universities of Potsdam and Tübingen as well as the Helmholtz-Zentrum Berlin and the Max-Planck-Institut für Eisenforschng in Düsseldorf. The results have been published today (April 13, 2022) in Nature under the title “Perovskite/organic tandem solar cells with indium oxide interconnect.”

Conventional solar cell technologies are predominantly based on the semiconductor silicon and are now considered to be “as good as it gets.” Significant improvements in their efficiency – i.e., more watts of electrical power per watt of solar radiation collected – can hardly be expected. That makes it all the more necessary to develop new solar technologies that can make a decisive contribution to the energy transition. Two such alternative absorber materials have been combined in this work. Here, organic semiconductors were used, which are carbon-based compounds that can conduct electricity under certain conditions. These were paired with a perovskite, based on a lead-halogen compound, with excellent semiconducting properties. Both of these technologies require significantly less material and energy for their production compared to conventional silicon cells, making it possible to make solar cells even more sustainable.

Engineers at MIT and the National Renewable Energy Laboratory (NREL) have designed a heat engine with no moving parts. Their new demonstrations show that it converts heat to electricity with over 40 percent efficiency—a performance better than that of traditional steam turbines.

The heat engine is a thermophotovoltaic (TPV) cell, similar to a solar panel’s photovoltaic cells, that passively captures high-energy photons from a white-hot heat source and converts them into electricity. The team’s design can generate electricity from a heat source of between 1,900 to 2,400 degrees Celsius, or up to about 4,300 degrees Fahrenheit.

The researchers plan to incorporate the TPV cell into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the sun and store that energy in heavily insulated banks of hot graphite. When the energy is needed, such as on overcast days, TPV cells would convert the heat into electricity, and dispatch the energy to a power grid.

Perovskites are a family of materials that are currently the leading contender to potentially replace today’s silicon-based solar photovoltaics. They hold the promise of panels that are far thinner and lighter, that could be made with ultra-high throughput at room temperature instead of at hundreds of degrees, and that are cheaper and easier to transport and install. But bringing these materials from controlled laboratory experiments into a product that can be manufactured competitively has been a long struggle.

Manufacturing perovskite-based solar cells involves optimizing at least a dozen or so variables at once, even within one particular manufacturing approach among many possibilities. But a new system based on a novel approach to machine learning could speed up the development of optimized production methods and help make the next generation of solar power a reality.

The system, developed by researchers at MIT and Stanford University over the last few years, makes it possible to integrate data from prior experiments, and information based on personal observations by experienced workers, into the machine learning process. This makes the outcomes more accurate and has already led to the manufacturing of perovskite cells with an energy conversion efficiency of 18.5 percent, a competitive level for today’s market.

Researchers used radiative cooling to generate enough to power LEDs or charge a cell phone.

NASA has agreed to test startup SpinLaunch’s kinetic launcher, a giant circular accelerator that aims to shoot 200 kilogram satellites into space.

The California-based SpinLaunch’s launcher is located at the Spaceport America facility in New Mexico where it will carry out a test flight with NASA later this year, according to the firm.

Continue reading “These Solar Cells Produce Electricity at Night” »

A new PV module makes electricity from thermal radiation. Imagine that.

The electromagnetic spectrum is comprised of thousands upon thousands of frequencies. Sound and light are all part of the spectrum, as are the frequencies that make radio and television broadcasts possible. Today’s solar panels harvest light waves from a small part of the EM spectrum and turn them into electricity, but there are many other frequencies like thermal radiation that could someday stimulate new kinds of photovoltaic cells to generate electricity as well.

Researchers at Stanford have recently published a study in the journal Applied Physics Letters that describes a new type of cell that converts thermal radiation into electricity. When the sun goes down, living organisms and physical structures like buildings, road, and sidewalks radiate heat back into the atmosphere. We call this radiational cooling and it is those electromagnetic waves the Stanford researchers say can be put to work making electricity.

Continue reading “New Photovoltaic Cell Makes Electricity From Thermal Radiation” »

Agricultural PV (or agrivoltaics) is the simultaneous use of land for both agriculture and solar power generation. This year‘s Intersolar Europe in Munich will put a major focus on this topic.

About 750 million people in the world do not have access to electricity at night. Solar cells provide power during the day, but saving energy for later use requires substantial battery storage.

In Applied Physics Letters, researchers from Stanford University constructed a photovoltaic cell that harvests energy from the environment during the day and night, avoiding the need for batteries altogether. The device makes use of the heat leaking from Earth back into space—energy that is on the same order of magnitude as incoming solar radiation.

At night, solar cells radiate and lose heat to the sky, reaching temperatures a few degrees below the ambient air. The device under development uses a thermoelectric module to generate voltage and current from the temperature gradient between the cell and the air. This process depends on the thermal design of the system, which includes a hot side and a cold side.

My sister is in the process of building a house in Ohio, and I’ve been having conversations with her about how to make it green. She and my brother-in-law both consider me to be eco-crazed (arguably rightly so given the climactic and political stakes) and so tend to raise eyebrows when I make one of my many helpful suggestions.

For example, I suggested they install a central heat pump instead of inefficient electric resistance heating, but only after consulting their HVAC guy, who is a fan of heat pumps, did they decide to install one (Woo-hoo! They’ll save thousands of dollars and pounds of CO₂ with that choice). They are also making their home solar-ready and plan to install panels in the next couple of years — this is mostly because solar offers a sense of self-reliance that is perennially popular across political and geographic boundaries.

However, when I tried to talk them into installing a heat pump water heater, I ran into serious resistance. If you haven’t heard about heat pump water heaters, they are an enormously powerful energy/CO2 reduction technology lying hidden in plain sight in the most humble of appliances — the water heater.