🌞 The problem with renewables

Electrical engineers will know what this subtitle is all about, and if I’m not mistaken, a sly grin will be spreading across their faces as they realize that they alone hold the truth to this knowledge. However, this article is for the average joe who doesn’t know a word about electricity.

As with most things, what comes into a system has to come out. If this rule is not obeyed then the system either implodes or explodes. So it is as well for electricity. National grid regulators need to ensure that the grid is balanced, that supply and demand are continually matched. If this is not the case, infrastructure and equipment could become damaged. So how do grid regulators balance the grid? Well, this is where frequency comes in.

However, it is first necessary to understand how power is generated. Generators turn kinetic/chemical energy into electrical energy. Traditional steam-turbine generators use fossil fuels to create steam, this steam then rotates a turbine which rotates a rotor mounted to a stator. Copper wire is wound around the rotor and is energized with electricity. Now if you remember faraday’s first law, you’ll know that this will subsequently cause a magnetic field. The stator consists of copper bars, and as the rotor turns, its magnetic field passes through the copper bars and induces an electric current. This current is subsequently sent out onto the transmission system.

The magnetic field which is created has a north and a south pole, which causes the current to change direction each time the rotor completes a rotation, hence the name alternating current (AC) for the electricity being produced. Now frequency is the measure of the rate of that oscillation (the change in direction) and is measured in the number of changes per second – also called hertz (Hz).

Okay, back to planet earth. So why is frequency is important for grid regulators? Essentially, regulators use the frequency to control the balance of the grid. If more electricity is being generated than the grid is consuming, then the frequency will change, which inform regulators that generation should be cooled down. Thus, frequency is the main signal informing regulators of what’s going on in the grid.

Bad day Joe, the Sun ain’t shining. Well at least the wind isn’t blowing

Renewables cause a problem for grid regulators because they are intermittent. Using renewable energy to balance the grid is too risky and too unpredictable. Even most nuclear power stations can’t be used for grid regulation, as most of them were designed to consistently operate at a single ‘baseload’.

Consequently, when using renewable energy, a need is created for a stabilizer. A power generation method which can easily and efficiently scale up/down it’s power generation. Traditional power stations can do this easily, and France’s new nuclear energy stations can also do this, but no renewable power generation can currently act as a stabilizer. Thus, frequency control in grid systems is one of the most important aspects of the green transition, and should definitely be a part of every conversation of how to decarbonize.

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🔭 The development of the ultrasound probe

Researchers at the Massachusetts Institute of Technology have shrunk the handheld ultrasound probe down to the size of a postage stamp, and made it stick to the skin with a special bioadhesive. This new device can record high-resolution videos for two days at a stretch, allowing doctors to diagnose heart attacks and malignant tumors, test the effectiveness of medications, and assess general heart, lung, or muscle health.

According to Xuanhe Zhao, a mechanical engineer at MIT and co-author of a paper describing the new device, "The beauty of this is, suddenly, you can adhere this ultrasound probe, this thin ultrasound speaker, to the body over 48 hours". This can change the paradigm of medical imaging by empowering long-term continuous imaging, and it can change the paradigm of the field of wearable devices.

Traditional ultrasound scans are great at peering beneath the skin without causing damage to the body, but access to such scans is limited. "The conventional handheld ultrasound requires well-trained technicians to put the probe properly on the skin and apply some liquid gel between the probe and skin," says Nanshu Lu, a mechanical engineer at the University of Texas at Austin. "And as you can imagine, it’s quite tedious and very short-term, very constrained."

Thanks to their potential versatility, other researchers have attempted to make stick-on ultrasound patches. But in order to adhere to soft, stretchy skin, earlier devices were designed to be stretchable themselves. This form factor weakened image quality because it could not accommodate as many transducers.

Instead of making the device itself stretchy, Zhao and his team attached a rigid probe, just three millimeters thick, to a flexible layer of adhesive. This adhesive replaces the gooey liquid placed between a traditional ultrasound wand and the skin, and it is a hybrid of a water-rich polymer called a hydrogel and a rubberlike material called an elastomer.

With this new technology, doctors will be able to diagnose illnesses at an earlier stage, and with more accuracy, which will save lives. Now, if only they can figure out a way to make the ultrasound gel taste like ice cream, then we'll really be in business.