The Envelope Is Pushing Back in Renewable Energy Efficiency

The Envelope Is Pushing Back in Renewable Energy Efficiency

by | published June 12th, 2019

Periodically, I evaluate progress in some new developments in renewable energy such as solar and wind power.

Part of this is due to the fascination I have had since my youth in what folks have been able to do in laboratories. Pushing the envelope has always been a hallmark of progress.

But sometimes the envelope pushes back.

Take the apparent limitations in harnessing renewable energy from nature.

To be sure, solar and wind are a major ingredient in the emergence of a new global energy balance. Despite its position in that overall balance, the solar-wind-biofuel component will comprise the largest single increase.

In public briefings, I usually illustrate forward changes in the balance in the following way…

It’s No “Silver Bullet”

Such a balance still relies upon traditional sources like crude oil, natural gas, and even coal.

Despite all the debate surrounding “green” energy advances in Europe and the Western Hemisphere, the energy focus has shifted to Asia, where demand will progressively dictate usage and price. There, coal remains a major course of energy for decades to come, and the reliance upon oil and gas will even increase.

The place occupied by renewables, therefore, is not as a “silver bullet” to wean the world from dependence upon hydrocarbons. Rather, sources like solar and wind will be an increasingly important part of the aggregate picture moving forward.

The main impediment to how fast that part of the energy sector expands remains a vexing efficiency problem.

The One Problem with Renewable Energy

Now, both solar and wind have had significant improvements in performance that have reduced the cost of power generation.

The discussion of what has been termed “grid parity” (the effective equivalence in how much it costs to generate electricity from different sources) has decidedly favored solar and wind in the past several years.

But one vexing problem persists. An ability to offset this one could be a veritable game changer.

In solar and wind applications, the power is harvested as direct current but must be transferred into alternating current for transmission on the grid. This is referred to as the inversion problem.

When first introduced, solar had an inversion problem that sacrificed well over half of all power produced. A retention of any of that electricity would improve efficiency significantly. It would also lessen the need for public finance or subsidies, thereby removing the primary political argument against renewables in just about any jurisdiction worldwide.


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For the past several years, an international research team has been experimenting with a potential breakthrough. Unlike most other approaches – that regard generating and inversion as separate problems – this one examines the efficiency issue in a more holistic way.

A description of this potential breakthrough first appeared several years ago in the journal Science (click here to read it).

More recently, the following is how Dexter Johnson described it for IEEE Spectrum. The text in bold and italics is what I consider the single most important efficiency advance in the process.

According to Dexter Johnson:

“An international team of researchers has developed a photovoltaic cell based on a combination of magnetic electrodes and C60 fullerenes– sometimes referred to as Buckyballs – that increases the photovoltaic efficiency of their device by 14 percent over photovoltaics using ordinary materials and architecture.

Scientists from China, Germany, and Spain have taken spin valves-devices based on giant magnetoresistance and used in magnetic memory and sensors-and combined them with photovoltaic materials. The result offers a new way for solar cells to convert light into electricity.

“The device is simply a photovoltaic cell,” says Luis Hueso, research professor and leader of the Nanodevices Group at CIC nanoGUNE in Spain, in an e-mail interview with IEEE Spectrum. “However, we are using magnetic electrodes (cobalt and nickel-iron) rather than standard indium tin oxide (ITO) and aluminum as commonly used in organic photovoltaics.” The magnetic electrodes provide electrons with a certain orientation of their spin, creating what’s called a spin polarized current. Using these electrodes increased the photovoltaic efficiency by 14 percent compared to using ordinary electrodes, he says.

In order to achieve these results, the researchers needed the device to have both a photovoltaic effect and a spin transport effect. That is, the electrons keep their spin orientation as they cross the device, according to Hueso. “These two effects have not been observed before in the same device, only separately,” Hueso adds.

One of the byproducts of these simultaneous photovoltaic and spin-polarized effects is that the device they have developed has the added functionality of serving as an inverter, which is used to convert the direct current (DC) produced by solar cells into alternating current (AC).

Hueso explains that the current inversion is created by an external magnetic field. As the magnetic field changes, the current changes direction. The reason this works is that the current inside the device has two sources: one is the current generated by the light and the other is the current coming from the magnetic electrodes.

The current generated by the light can be changed by the amount of light irradiation. The current coming from the electrodes can be changed by the magnetic field. Balancing both contributions means the flow direction of the overall current can be modified.

The key to the functioning of the device is the C60 fullerene. The C60 is both a photovoltaic material and one that can sustain the spin polarization of the electronic carriers. “Since both effects had been demonstrated in the past-the spin one by our group-we decided to use it for a proof-of-principle experiment,” says Hueso.

The actual current output in the device is fairly small, mainly due to the fact that the C60 is not a great material for photovoltaics. To address this the researchers are currently working on building a similar device using better performing materials.

While Hueso recognizes more engineering would need to be done with the device they have produced, he believes that an actual device that acts as both a photovoltaic and an inverter could indeed be possible.”

We’re Headed into Exciting Territory

Well, according to sources involved in analyzing a range of results from the process, there have been recent advances in this approach.

What is emerging is a new hybrid PV cell design that reduces the inversion problem even further. Early indications is that less than 20% of electricity harvested is being lost in what is now a more seamless generating-inversion-transmission process.

If this can be expanded in application (always the main problem in new possible breakthroughs), we may really have something significant here.



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  1. Carl
    June 20th, 2019 at 04:17 | #1

    Yes if only renewables could get just half of all the subsidies that oil actually got why we might not have created the freedom fighters of 9/11.

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