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A climatization using DC current from capacitors charged with solar panels might be more interesting in mild hot regions.

If I understood well AC is optimized for carrying current on long distance with minimal loss. But most electric devices use DC. They need an AC to DC convertor with some energy loss.

Solar panels produce DC and is usualy converted to AC with some loss. Then, in most electronic devices, this AC is converted back into DC in the device power transformator.

What waste of energy. Shouldn't we do something about this ?




> What waste of energy. Shouldn't we do something about this ?

Most devices which operate on DC (e.g. computers, TV) have a switching power supply, which is around 90% efficient. So for a computer drawing 100W, only about 10W is lost in the conversion of AC to DC.

Larger appliances such as microwaves, ovens, and air conditioners will use AC directly without conversion to DC (except maybe to power the control electronics).

> But most electric devices use DC.

Yes, but no national grids are DC. There is a lot of interest in using high voltage DC (HVDC) for long distance transmission (and wind farms), since you don't have to expend energy to generate and maintain the sine wave (and your collector field electronics are simpler), but the customer connection is always AC.

With the insane amount of money invested in delivery to homes as 110/220VAC, no one is going to start selling DC devices. Even in regions where this is no electricity and people use off-grid systems, the economies of scale mean that DC appliances such as refrigerators are often 200-400% more expensive than their AC counterparts.

A lot of research has been put into DC distribution, but the main issues are:

- Devices still require a DC/DC converter to step up or down the distribution voltage to their operating voltage. This converter is again not 100% efficient

- High voltage DC is deadly (your muscles will contract instead of releasing, so if you touch a cable you're dead)

- Low voltage DC requires thicker wires, meaning higher cost for distribution

Source: work for a utility company


Another factor is that high voltage DC step-down is significantly harder than AC step-down, especially once you get into the 100's of KV. With AC that's relatively easy, transformers are passive components, very well understood and can be made for extremely large power levels without getting into exotic engineering.




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