Dark Absorbing Diodes Are No DAD Joke

We will confess that the authors of the Applied Physics Letters article “Experimental Demonstration of Energy Harvesting from the Sky using the Negative Illumination Effect of a Semiconductor Photodiode” never used the acronym DAD or the phrase “dark absorbing diode.” But we thought it was too good to pass up. The research work uses a type of diode to generate small amounts of power from darkness. Admittedly, the amount of power is small, but it is still an important result and could result in — another coined phrase — negative solar cells providing energy by taking advantage of the temperature differential between the cell and the night sky.

In theory — and with no atmosphere — the technique could only result in about 4 watts per square meter. Not only is this low compared to a solar panel’s 100 to 200 watts per square meter, but it is also far from the prototype’s 64 nanowatts per square meter. Clearly, this technology has a ways to go to become practical.

To make matters worse, the experimental setup used apparatus that surely drew more than the power generated, so we couldn’t help but wonder if this was real power generation as much as just capturing power that was otherwise wasted as heat. However, it wasn’t clear to us at a cursory glance how much of the power used was for performing measurements versus actually providing energy to the diode.

We will let you decide if this is a breakthrough or a fancy free energy device with some math obscuring where the energy is really coming from. If it is workable, we’ll admit it isn’t impressive today, but neither were 1907-vintage silicon carbide light emitting diodes and those turned out well after some technological advances.

18 thoughts on “Dark Absorbing Diodes Are No DAD Joke

  1. I grok the basics, use the ~4K cosmic background as a cold sink, but kinda lost as to how not just directing it at the peltier cold side should give a little. Will have to go over it in the AM after coffee…

    However, could be a neat thing to try with 3D printing a load of micro black body bolometers with thermocouple ends stuffed in the back, and “hot” sided to a big sink for ambient… Wonder if a square foot of them would run an ATTiny or something.

  2. Uhm… inspiration to improve someones design or focus on other methods? Shit, I was thinking ultra low intensity emissions detector to harvest energy as a goal to improve existing system performance from the email abstract I could read.

    Then again… I’m surprised at how little goes into heat exchangers on the backs of solar panels which might be able to be used directly or indirectly to create some power via thermoelectric devices to somewhat increase the theoretical limits of those systems which like most systems have a 2D or really 3D printing or manufacturing limit threshold until a new technology or material needs to be used. That is… if I’m comprehending correctly… I just received the right angle plate and am waiting on the new tapered bearings for the 7×10 mini-lathe I’m going to upgrade and turn into a mini-mill plus have a HP Z3801A GPSDO on the way which is a little tangent to this tech which isn’t helping me being the world of studying microwaves too. Hell, come up with a feedback loop system to trigger all the fucking microwave sources for free energy.

    I’ll have to read into this some more.

    1. Those heat exchangers are probably going to be expensive and inefficient. I think a solution would always be make the solar panel 10% bigger for more power rather than add the whole complexity of another system.

      1. “Those heat exchangers are probably going to be expensive and inefficient. ”

        Yeah, makes sense more for a direct conversion of thermal energy to an open or closed loop system for water or radiant heating…. doesn’t make sense to convert the thermal energy to electrical power since the efficiencies are even worse with a heat exchanger that isn’t directly integrated on the solar panel annnddd the efficiencies of the thermoelectric devices are so low compared to solar panels.

        Wondering what the price per Watt per Surface area or Volume is for PV and TEG with the range of consumer available devices?

        Now, if the price points of high temperature photovoltaics comes down ever… then this paper inspires me to think is more just demonstrating a method… then the concentrating solar on the PV might be something more practical if the efficiencies and size along with price warrants that method. Like say Fresnel lens coating on solar panels off hand that wouldn’t impact performance over time.

        Thinking I need to read into materials properties and physical characteristics to determine theoretical limits and then scale to feasible production methods that is/are cost effective for system effectiveness enhancements.

        Where this system is a newer method or just a way to envision solar panels producing at night or dark conditions seems.

        1. I don’t think a fresnel lens coating will do much of anything, except block some of the light. My bet is any benefit you get from redirecting the light for a better angle of incidence will be outweighed by blocking the light which is already ideal. For lenses to accomplish anything, they need to be larger than the cells. Most likely mirror arrays would be a lot more effective.

          1. I’m not sure the Fresnel lens coating theory is right or wrong based on the regions on the solar panel surface area/volume that can use more or less intensity. The outer surface of the lens would be larger focusing to the inner surface of the optimal regions of the PV. I don’t really know in detail and just muse’n. I’m thinking you’re correct most likely since would be factored into the PV design already regarding materials performance characteristics.

            In regards to higher temperature PV’s seems concentrating is smarter maybe even on the panel itself… though in large systems seems using the direct conversion to a fluid medium or a heat exchanger to make a closed loop system would be better and is for TEG methods.

            I thought the concentrating trough arrays are the most efficient last I read into… so maybe a solar panel nano (just sounds cool for branding) concentrating trough PV design using that method would be more efficient if the material science and fabrication is efficient enough or the infrastructure is subsidized/invested to make happen.

  3. Isn’t the peltier device the thing generating the electricity. More interesting to me would be if the system could “harvest” cold from space by letting an insulated chamber radiate into space.

  4. I think this falls under the category of basic research. I think it’s described as a way of generating power to make it more interesting and attention-gathering than just studying a phenomenon for it’s own sake, but I’m pretty sure the people doing the work aren’t ever expecting it to be a way of gathering energy for use.

    Just some ballpark numbers to indicate the feasibility of energy gathering this way.

    The sun’s irradiance of the earth’s surface is around 1000W/m^2, so that’s an upper theoretical limit for direct solar PV cells (without additional mirrors/lenses, etc). The most power possible from a directly illuminated 1m^2 PV panel is 1kW AFAIK, the best PV cells around now give around 200W/m^2

    The theoretical maximum they’re describing by this method is 4W/m^2, and they’re only getting nanowatts now. They would be a very very long way from getting even reasonable efficiency, and even if they reached the theoretical maximum, a 1m^2 panel is going to generate around 48Wh in 12 hours of darkness. Keep in mind that in real world conditions this will never happen (In a darkness absorbing panel on the roof of your house kind of way).

    Even if it were possible to get the 100% efficiency, you could, instead, take a present day 10% efficient solar panel, and make it 5% larger and feed the excess into a small battery (which would cost _far_ less in materials and energy to produce).

    This will never be used to gather energy on any significant scale. There may be some very niche applications where extremely small amounts of power are needed in the absence of any better source but even that seems unlikely.

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