Electricity From Solar Cells - By MITK12Videos
Transcript
| 00:19 | Oh man , not again . My battery died . | |
| 00:23 | Where am I going to get power now ? There's | |
| 00:25 | no way I can get power around here , but | |
| 00:27 | it's such a sunny day . Maybe I can get | |
| 00:29 | power from the sun . Indeed , the sun is | |
| 00:32 | a huge and reliable source of energy . But how | |
| 00:34 | can we convey this energy into electricity ? You must | |
| 00:37 | have heard about solar cells . But do you know | |
| 00:39 | how they work ? And how many of them would | |
| 00:41 | we need to pour ? Mike's laptop so that he | |
| 00:43 | can keep playing this awesome game first . Let's take | |
| 00:46 | a look at the salsa , wow , that's really | |
| 00:48 | thin . And in fact , there are even two | |
| 00:50 | super thin layers in there . When the sunlight hits | |
| 00:53 | the sell , it gives enough energy for electrons to | |
| 00:55 | break free and travel for an external secret generating electricity | |
| 00:59 | . But let's have a closer look at the cell | |
| 01:00 | to understand how it really works . Most of the | |
| 01:04 | cells are made of silicon by themselves . The atoms | |
| 01:07 | of silicon would be organized in a very stable structure | |
| 01:10 | . However , when phosphorus atoms are added to the | |
| 01:13 | silicon structure , they disrupt the nice arrangement because they | |
| 01:16 | have one extra electron compared to silicon . This electron | |
| 01:19 | cannot bound to the neighboring atoms and it becomes a | |
| 01:21 | free electron . If we had a lot of phosphorus | |
| 01:24 | in the silicon , we end up with a lot | |
| 01:25 | of free electrons in the structure . This arrangement is | |
| 01:28 | called anti because it's going to be on the negative | |
| 01:30 | side . We can also add born instead of phosphorus | |
| 01:33 | to the silicon . This time the burn atoms have | |
| 01:35 | one less electron that would be necessary for nice day | |
| 01:38 | out . You can think of the lack of electron | |
| 01:40 | as a hope that would be free to travel through | |
| 01:42 | the structure . Therefore adding a lot of bone atoms | |
| 01:45 | to the silicon will result in a lot of free | |
| 01:47 | holes in the structure . This arrangement is called P | |
| 01:49 | Type as it's going to be on the positive side | |
| 01:52 | . To form a soil sell you first need to | |
| 01:54 | bring these two types together at the region of contact | |
| 01:57 | . The extra electrons of the anti would love to | |
| 01:59 | combine with the extra holes of the P . Type | |
| 02:01 | . However , since the electrons are negative charges , | |
| 02:04 | the items they left now become positive ions . Conversely | |
| 02:07 | , the holes that , combined with the electrons , | |
| 02:09 | left negative ions on the P side . This difference | |
| 02:12 | of charges results into an electrical field between the two | |
| 02:14 | sides , which prevents more electrons and holes from combining | |
| 02:17 | with travel . In fact , new electrons trying to | |
| 02:19 | reach the junction are pushed back by the negative charges | |
| 02:22 | of the P . Type , while new holes reports | |
| 02:24 | by the positive charges of the anti overall , the | |
| 02:27 | field acts as some kind of wall that keeps the | |
| 02:30 | electrons to the inside and the holes to the P | |
| 02:32 | side . So what happens with the sun ? Well | |
| 02:35 | , when the light reaches the junction , it may | |
| 02:37 | have enough energy to break a whole electronic combination . | |
| 02:40 | However , because of the field that has been created | |
| 02:42 | before , the electron is sent away towards the inside | |
| 02:45 | . While the whole is sent towards the P side | |
| 02:48 | , They can only recombine if this extra electron is | |
| 02:50 | collected by an external secret connected to the P side | |
| 02:53 | . In that case the electron will run for whatever | |
| 02:55 | electrical device that would be underway before going back to | |
| 02:58 | the cell and finally recombine with the whole . Now | |
| 03:01 | one cell like this only provides 1.5 watt of electrical | |
| 03:04 | power , which is fairly limited . So if we | |
| 03:07 | need more power , well , we simply have to | |
| 03:09 | use more sales . Hey , Mike , here's a | |
| 03:12 | solar panel for you . It has 36 cells . | |
| 03:15 | That's enough to charge your laptop awesome . I can | |
| 03:18 | play again and all I need is energy from the | |
| 03:20 | sun , isn't it ? Great , great indeed . | |
| 03:26 | And in fact we can even bore more than a | |
| 03:28 | laptop with solar panels . If we use a lot | |
| 03:29 | of them . For example , this solar farm can | |
| 03:32 | pour 600 average us homes , wow , that's pretty | |
| 03:35 | big isn't it ? Alison , so couldn't we just | |
| 03:38 | power the whole country with ourselves ? How big would | |
| 03:41 | that penalty ? Let's do simple estimation . Over one | |
| 03:44 | year , this fund provides about 8:00 of electrical energy | |
| 03:48 | for the year of 2000 and 10 . The total | |
| 03:50 | electricity production in the U . S . Summed up | |
| 03:53 | to four million gigawatt hours . The equivalent of 500,000 | |
| 03:56 | southern farms like this one . The area you will | |
| 03:59 | need for these farms would be about 1/9 the size | |
| 04:01 | of California . Hey , that's all the area requires | |
| 04:04 | . Why don't we have solar panels powering everything yet | |
| 04:07 | ? Well as of today , there are two main | |
| 04:10 | limiting factors to sell panels cast and electricity storage . | |
| 04:14 | Well wait , you said cast don't you just get | |
| 04:16 | energy from the center for free . That's correct . | |
| 04:19 | But the construction of solar cells is so expensive that | |
| 04:21 | even if we use them during 30 years it would | |
| 04:23 | be cheaper to get electricity from coal . However , | |
| 04:26 | improvements in technology and in materials will probably make solar | |
| 04:30 | cells more affordable in the future . Also the electricity | |
| 04:33 | provided by solar cells is not available all the time | |
| 04:36 | . We could theoretically stole the circus of electricity during | |
| 04:38 | the day and use it at night . But during | |
| 04:40 | these huge amounts of electricity is still complicated and expensive | |
| 04:44 | . These two reasons mainly explained why today only .4% | |
| 04:47 | of US electricity comes from solar cells . However , | |
| 04:51 | solar energy is very valuable because it is sustainable . | |
| 04:54 | The sun will still be shining and sending its energy | |
| 04:56 | to the earth for billions of years . As new | |
| 04:59 | technologies appear , we will most likely be able to | |
| 05:01 | convert this energy into electricity forecast that will compete with | |
| 05:04 | other resources anyway . If anything , the solar cells | |
| 05:08 | technology enabled my to keep playing this game . |
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Electricity From Solar Cells is a free educational video by MITK12Videos.
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