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11

Any high slew rate (fast rate of change of power) stresses the grid. Lots of things cause high slew rates. People getting ready for work in the morning, having showers, turning lights and appliances on. Factories starting up at the same time. Faults on major international HVDC transmission lines. Safety shutdowns at nuclear reactors. Lots of people turning ...


6

The principle of conservation of energy is your friend. The wind turbine generates electricity. That energy has to come from somewhere. The other energy in the system is the kinetic energy of the wind. Therefore, the wind turbines convert the kinetic energy of the wind into electricity, and the kinetic energy of the air downwind of the rotor is less than ...


4

I didn't read every word but I'll address what I believe are three of the most important parts of the patent. (1) One of the ideas for reducing radiative heat loss is reasonable In solar thermal systems, the hot object can lose heat by emitting IR thermal radiation, and you want to stop that process. This is a big field but the approach most people use is ...


3

I think EnergyNumbers's Answer is an excellent one, but could leave some people a bit mystified by what exactly a "direct ray" is and what exactly its relevance is. The essential idea here is that a Fresnel lens is an imaging machine: it puts a curvature on a low aberration wavefront so that that wavefront converges. Its working depends on there being ...


3

You're right that the rod would keep swinging under ideal physical circumstances, but this wouldn't be due to gravity. If you imagine the rod at the horizontal point of its rotation, there is a gravitational force on one side pulling on one weight, trying to speed up its rotation, and a gravitational force on the other side pulling on the other weight, ...


2

The energy is converted to heat. The friction of the water with the river bed, and with itself, converts the energy to heat.


1

The answer to this question is very much analogous to the answer to how aeroplanes fly. See Physics SE Question "What Really Allows Airplanes to Fly?" and the best (IMO) answer is this one here. But basically the airfoils, sails or vanes - whatever they may be called - deflect the flow of air. They do this by pushing on the air and changing the latter's ...


1

First, it's not only drag that slows down the air, every force has to be matched by an equal and opposite force including lift. Second, friction is not the sole cause of drag, indeed there's drag on an airfoil in an inviscid fluid due to pressure. So why we need sophisticated airfoil design when traditional windmills can work and how modern wind turbines ...


1

The system you describe, a water tower with pumps and turbines, is a version of a pumped hydro storage system. The amount of energy stored in a pumped hydro storage system is defined by the elevation, i.e. the height that the water is lifted; multiplied by the volume of water that is lifted (assuming that the height the water will fall, is the same as the ...


1

Rare earth elements aren't really used much in PV at all. The market is dominated by silicon cells (~95% of the market). The next big player is Cadmium Telluride (~5% of the market). The rest are pretty insignificant. Also, note that rare-earth elements are (with the exception of Promethium) not particularly rare.


1

The solar spectrum hitting the earth corresponds to black body radiation (apart from some absorption lines due to gasses in our atmosphere and inherent to the sun). In principle, one wants to harvest an as large as possible fraction of this spectrum. Solar cells can be optimized by increasing the absorption at a certain wavelength (which mostly depends on ...



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