here once again is our classification of resources into three Perpetual or inexhaustible renewable or potentially renewable and non-renewable let's get started talking about the perpetual resources and the first one that we come to direct solar energy every day the sun sends us huge amounts of heat and light mostly we don't really do anything with it we just enjoy when you walk outside you don't need a flashlight everywhere you want to go is well lighted free of charge it's just there the air the weather the climate is warm and comfortable you don't need to bundle up to provide heat it's just there nature provides it we do however collect a small amount of the sun's energy transform it into other forms of energy that we can buy and sell and ship from one place to another how do we do that your immediate answer I'm sure was solar panels but wait there are two entirely different classes of devices that we carelessly call solar panels they do two entirely different things the first kind of solar panel collects the Sun's light and transforms it into electricity properly we should call these things photo voltaics photo light volts electricity light into electricity yeah we normally just call them solar panels okay photovoltaic panels they are the ones with that crosat pattern they exist in all shapes and sizes you probably have some about this big running your pocket calculator so that it doesn't have to draw power from batteries as long as there's adequate light slightly bigger ones about this size are found on the top of the poles holding the emergency phones alongside the freeway first one about this size on the bus stop in front of the D building on the city college campus it provides the power to run the display that tells you when the next bus is supposed to be coming bigger ones are on the roofs of your neighbor homes like these houses in Lakewood just a few blocks from the campus and huge installations of solar panels of photovoltaic panels sorry hug installations also exist much bigger than rooftop of your home one example would be on top of the parking structure on the south side of Carson on the Lac campus for those of you who've come up through the Long Beach Unified School District you've probably noticed that the parking lots at your high schools have in the past two years been roofed over with photovoltaic panels here for example is milikan high school only a few blocks away on pal Verdi between Willow and spring those solar installations covering parking lots like at high schools like at Cal State are a win-win situation the car cars are protected from the sun which means they don't get so hot it also means that the ultraviolet light from the sun that would fade the upholstery D nature and crack the plastic rot the rubber isn't getting to the cars they last better and the land that's paved over for the parking lot can't be used for anything else now it's providing the parking and electric power as well a lot of large buildings shopping malls big stores you can't really see from the ground but they also their roofs are covered with photovoltaic panels here for example is the Target store in Seal Beach let's address one important area of confusion photovoltaic panels do not store energy they transform energy from one form to another light in electricity out no light in nothing comes out if you have one of those toys that are powered by solar panels put it in the sunlight the toy Works put your hand over it block the sunlight it stops instantaneous so the photo voltaic panels on the roof of your neighbor's homes generate electricity during the day they do nothing at night of course nighttime is when we need a lot of our electricity that's when we need lighting and for most of us when we're out at work or school during the day nighttime is when we turn on our appliances so how do we make photovoltaic panels a practical proposition if you live way out in the sticks Off the Grid like you have a cabin in a canyon way out in the mountains and solar is your only source you need storage how do we store electricity batteries you need a huge Bank of batteries which will probably cost at least as much if not more than the solar installation itself a bank of batter is the size of a large desk would allow you to run lights a TV maybe some small appliances through the evening don't even think of it using any large appliances that's it if you live in the city however you have another excellent option your neighbors typically have the photoal take panels on the roof generating power during the day they're also connected to the city power which provides what they need at night we have a great law in place which says that if you generate more power than you need you can sell it to the power company and they're obliged to take it and pay pay you Market rates so the way that works the solar panels and power company electricity go to a control panel which handles the switching during the day if you're out at work or school and your home isn't using scarcely any electricity your photovoltaic panels will be creating more electricity than you need and that control panel is routing that electricity out of your home and back to the power company at night the solar panels aren't contributing anything and all the power from the power company is coming in to supply your home the whole thing actually works through your meter you know your electric meter that little wheel that goes round and round and round slowly if you're not using much and spinning fast when you're using a lot of power well when you're exporting power when your solar panels are sending power out of the house it spins in Reverse counts down so at the end of the month you could receive a check from the electric company instead of a bill reality most homes receive a reduced bill because you take more from the power company than you send out from a photovoltaic PS that's how it works I don't know if you ever really been aware of this but for many years there were like one or two homes in your neighborhood that had photovoltaic panels on the roof and nobody else and then in just the last few years the number of a number of these panels has increased and increased and increased and increased right now photovoltaic panels is a boom industry if you have a landline phone at your home you're probably receiving advertising calls every week from folk trying to sell you photovoltaic panels why are the change photov voltaic panels are expensive they're also very inefficient 10 years ago solar panels at best gathered maybe 10% of the sun's energy falling on and that along with their price meant that if you paid to put solar panels on your roof you would not expect to see any Financial return for at least 10 years you pay up front to put the panels there then uh they return money to you in terms of a reduced electricity bill and if you calculate out the reduction of your electric bill yeah it would take 10 years of reduced electric bills before You' paid off your investment most people couldn't see the sense in that I mean many people aren't even going to be in the same home 10 years from now but as the years have gone by the panels have got better many of them are up at 15 to maybe even 20% efficiency today still pretty poor but a lot better than they were and the price has come down and those folks out there trying to sell you photovoltaic panels will tell you that today you can pay off the installation and start to see yourself making real money within five to seven years and lots more people can see the sense in that and that's why they're now becoming so much more popular by the way if you are considering having an installer come and put photo volting panels on the roof of your [Music] home be cautious there are all kinds of financial deals being offered and if they seem too good to be true they just might be there are times when you might actually want to consult a financial profession one approach hey we'll install your panels for free the installation won't cost you a thing interesting but one way of doing that is with financing but here's an approach that some companies are using yes they will put the panels onto your roof for free they own the panels you are providing the space on your roof but they own the panels you don't and you never will they will pay you you could consider it rent for your roof space they will pay you a percentage of the money made by the electricity sold through those panels but you'll never pay it off you'll never own the panels just be cautious okay with all the rooftop installations how much power are we generating let me give you an idea of scale that photovoltaic installation on the top of the parking structure at Lac at noon on a sunny day gener Ates almost half a megawatt of electricity that's a significant percentage of the electricity that the campus uses of course it generates Less on cloudy days generates less as you go on towards Sunset and doesn't generate anything these panels have been proliferating all over the city all over Southern California and two years ago I read a report that on certain sunny summer days at around noon Southern California was generating all the electricity it needed and more from solar power the conventional power plants could shut down completely and we were exporting giving away electricity through the grid system other states that doesn't mean we've got enough and now we can stop installing that was an hour or two either side of noon on particularly sunny days we're still using massive amounts of conventionally generated electricity all through the night but we're getting there solar power is ramping up nicely