Wednesday, 6 May 2020

energy conservation - Where does the electricity, generated by a solar panel, go if you don't use the electricity?



I'm sorry if this question is too trivial for this Q&A forum. I am a layman when it comes to physics (though I did cover the high-school physics courses).


I was wondering what happens to the electricity, that is generated by your own solar panel, in case you don't use any electricity in your home. Does it turn from electrical energy into heat? Or does something else happen? Is the energy "lost" for practical purposes?


A follow-up question: In case the energy is "lost" for practical purposes, wouldn't that be an enormous waste of energy? Is this what the "Smart Grid" network is intended for? To distribute the energy to other places where it is needed, thereby minimizing the energy loss and CO_2 emissions?



Answer



There are several ways to design the circuit.


If it's a Smart system, then when there's surplus power, additional devices will get turned on, to use it: dishwashers, washing machines, or immersion heaters in hot-water storage tanks. If there's still surplus after that, then it's as below.


If it's grid-connected, with an inverter, then it's usually designed to export surplus power to the grid. There's typically either an export meter, or the property's main electricity meter runs backwards during those times, to ensure that payment is made for the exports.


If it's designed as standalone, then it might have a battery where surplus power is initially sent. When the battery's full, then it's as below.


In the absence of other uses of the surplus, there's a resistance heater and heat sink where the generated power is dumped.


And in general, the economics tends to ensure that enormous amounts of energy are not wasted. If there's going to be a large surplus, that will be enough to justify expenditure on one or more of: a Smart system, a grid export connection, local storage.



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