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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 ...


5

Betz' limit arises from the fact that if the turbine tries to take too much energy out of the flow, the wind will divert and go around the turbine instead of through it. With a hydrothermal system the water is typically behind a dam, so the water has nowhere else to go. The turbines effectively convert gravitational potential energy into work, which can be ...


5

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 ...


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 basic energy requirements of homes, industries etc are measured in watts. It may be sometimes seen how much energy each sector utilizes over a span of time, but generally we see how many watts are used in homes, industries then further in colonies, cities etc. Atleast here in India (and I think it would be similar everywhere) we get our home supplies ...


2

Some PV modules are indeed one single large area: thin-film modules and polycrystalline silicon modules can be done as one single large area, or as arrays of rectangular cells. The design in this case is driven by economics. Monorystalline silicon modules always consist of an array of connected cells: and the reason for that is primarily about the science, ...


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

First off, I would be cautious about interpreting the parameter that press releases focus on as being the "most important" - it's just as likely to be the one that a press officer happened to pick because it seemed like a Nice Big Number, or possibly the one that they understood. Think yourself lucky if the units actually made sense! However, there is a ...


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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