hello everyone welcome back to public health for 16 this is topic 9 clean energy alternatives today we'll talk about this need for energy efficiency and conservation and then we'll start talking about different kinds of renewable energy or a clean energy alternative we'll begin our lecture with solar energy we have different kinds of renewable energy that uses Sun as source of energy then we'll talk about wind hydro power and different biomass renewable fuels and lastly we'll talk about hydrogen as energy source we've learned from the last lecture that globally speaking as well as here in the United States we don't use a lot of renewable energy in fact close to 80 percent of energy that we use in the United States and also in the world basically comes from fossil fuels so when we talk about fossil fuel we are really referring to these three energy sources that we discussed in the last topic although nuclear energy is a non-renewable energy however it is slightly different than fossil fuel you know fossil fuel really comes from the breakdown of living organisms whereas in nuclear power the uranium just comes from the earth itself but you can say that about 89% of our energy comes from non-renewable energy and only about 11% that we use comes from renewable energy source and and these include geothermal solar there is a lot of wind energy and biomass fuels which are not as good as some of the other renewable energy they're a little bit more dirty and also hydroelectric the UN wants 80% reduction in fossil fuel used by 2050 and it's going to take a lot of work for us to get there in order for us to ensure the survival of humankind and have a long sustainable resources available we have to encourage more energy efficiency and energy conservation they have to go hand-in-hand energy efficiency is maximizing output from current technologies and energy conservation is car telling activities to reduce the consumption of oil gas and coal supplies effective energy conservation could save us 6 million barrels of oil a day and this is a known fact that conserving energy is much better than finding a new source of energy let's talk about energy efficiency of different kinds of light some of you guys might be really familiar with these different types of light bulbs compact fluorescent light bulbs use 75% less energy and last 10 times longer than standard incandescent light bulbs some of you guys may not know in what incandescent light bulbs are we I used to use it growing up this is what incandescent light bulb looks like it has these filaments of wire as electricity runs through this very thin filament it gets very very hot and as it gets really hot it starts to glow which provides the lighting because these wires are very thin after prolonged use they will break and then you have to replace since the lifespan of incandescent light bulb is not very long on the other hand CFL light bulbs use different technology in fact our mercury vapors inside the light bulb that allows the radiance of light in fact it actually produces a lot of UV light and the white phosphor --that covers the bulb itself it will absorb the UV light and turn that into visible light lastly LED lights are the most efficient and have the longest lifespan and it uses diodes which produces light what are some ways in which you can reduce your consumption or conserve electricity at home Energy Star label electronic products assures that the product sees a fishin C standards by 10 to 50 percent and at home it's always better to use natural gas rather than electricity whenever possible and that's because if you remember electricity is secondary energy source words in natural gas is primary when there's a conversion of gas or natural gas into electricity we know from the second law of thermodynamics that we are going to lose some of the usable energy through heat washing your clothes in tap water or pool water will save a lot of energy because one of the highest cost of energy in Washington clothes is that if you were to wash your clothing in hot water it takes tremendous amount of energy to heat that water microwaves are more efficient than conventional oven so looking at all of the different ways we use electricity or on the house air conditioning is a big user 17% heating about 15% water heating 14% refrigerators is not as big consumer of feel compared to some of the other ones that we just mentioned lighting about 10% TVs and related products about 7% although fossil fuel use is still the main source of energy for us today we project that renewable energy sources will climb in the future let's talk about solar energy solar energy is the energy that we receive from the Sun it comes to us in the form of ultraviolet light visible and infrared light and we learned that Sun is a blackbody the amount of solar energy that reaches the earth is tremendous full sunlight delivers about 700 watts per square meters to Earth's surface 700 megawatt power plant is equivalent to having sunlight fall on about 390 square miles Orange County is about 950 square miles the Sun gives 10,000 times the energy that we use here's a first solar renewable energy we are going to talk about it's called flat plate collector it is a thin broad box which allows sunlight to heat the water there are two different kinds of flat plate collectors one is an active system and the other is a passive system an active system actually has a pump pump that continuously move hold water and inside his flat plate collector the Sun shines upon it and he heats up the water and then the hot water goes into a water tank and is stored there there's an active pump that uses electricity to continuously move that water so that it can maximize the amount of energy that is absorbed from the Sun in a passive system he uses gravity and convection to move the water from the collector plate to the tank you can see that as water heats up it becomes lighter right it is going to cause a convection flow that will push the water into the water tank and that will allow the cold water to move so this is not an active system so this will only circulate the water when the Sun is up there are about 60 million solar hot water systems and many of them are actually in China we don't so use we don't actually use a lot of flat plate collectors here in the United States but we should flat plate collectors can also be used for space heating now you don't have any water running through the flat plate collectors but here the sunlight is going to heat the air inside the flat plate collectors and this will allow the circulation of warm air and will heat the home you probably heard of green buildings and these are the homes that use energy much more efficiently for example these type of homes will have white or light colored roofs that will reduce overheating they tend to have windows that are very very efficient I call them super windows they also have stone floors walls to store the heat that is absorbed by the earth these type of houses also have these roof eaves that are elongated to prevent the Summer Sun from reaching the window but during wintertime when the Sun is actually lower it will allow more sunlight to enter the most familiar product that's related to solar energy is the photovoltaic cells and they are also known as solar panels you can see solar panels on top of the KHS building on top of our garage structures the good thing about these photovoltaic cells is that they can transfer directly to sunlight into electrical energy so these solar panels are made up of these tiny photovoltaic cells which are in the form of modules and many modules make up the panels and there are array of panels I can use to generate electricity really the idea behind the solar panels or photovoltaic cells are that there are two to kinds of material on these photovoltaic cells and when Sun hits on top of the photovoltaic cells it is able to separate the electrons from cations or positive ions the n-type layer is phosphorus rich and the p-type layer is boron rich n-type layers are what we call donor layer in which it provides extra electrons whereas in p-type layer a boron rich material has these holes in which it can accept electrons once the sunlight falls on the photovoltaic cell it separates electrons from the hole and allows the flow of the electrons solar cells convert light energy directly to electrical power with about 15 to 20 percent efficiency and these are the typical solar panels but some of the newer panels may have about 40 percent efficiency one of the great things about solar panels that they have no moving parts and they will last a very long time it is used in many different kinds of electronic equipment now one of the additional equipment needed for the solar panels to be applicable and utilizable is having an inverter and that's because the type of energy that's generated by the solar panels is the DC current and we talked about AC and DC current well the kinds of current that we use at home is alternating current so there has to be an inverter that converts direct current which is generated from solar panels into alternating current so that you could be put into the electronic grid costs have declined but are still relatively expensive average cost of photovoltaic power or solar panels about is about twelve cents per kilowatt-hour other sources some the cheaper fossil fuels will be less than twelve cents per kilowatt-hour so we have not reached the equivalent efficiency for solar panels hence people are still using fossil fuels because it's still cheaper but more efficient cells are being introduced and they are becoming less expensive which creates incentives for more people to use solar panels you can see in this graph that especially in Europe not as much in North and South America have been using more solar panels and hopefully we can increase our use as well not only can we have solar panels at home we can also have solar panel power plants it's just basically a huge array of these solar panels to generate enough electricity that would be equivalent to for example coal power plants or natural gas power plants there are about 40 plants worldwide each generates about 20 megawatts of energy here's one in the Solar star in Kern County in California solar power is a growing industry so we are utilizing more and more because it's efficient it's becoming more cost effective some of the disadvantages of solar energy is that the technology itself is more expensive at the same time depending on what source you use what technology you use you may still need backup energy source for example at night time you still need some kind of energy source right so it needs to be connected to a grid that will supply energy when the Sun Goes Down and of course many areas are not sunny in wintertime and can we still generate enough electricity to be efficient in this picture you can see the summertime Sun is very high up and it directly shines on the surface of the earth and you'd have more concentrated sunlight whereas the wintertime it's a little bit off to an angle and the concentration of sunlight is less so that less energy is produce in wintertime another renewable solar energy is concentrated solar power which intensifies a solar energy to generate huge amount of heat there are four methods of concentrating solar power there are curved reflectors that can heat liquid in these horizontal tubes I'll talk about them you also have the curved reflectors that will focus the light in a smaller area here is an example of solar cooker that you can use basically concentrating a lot of sunlight in a small area so that you can cook you can also use current mirror reflect light into absorbing tube and lastly you can use fill the mirrors to focus the light into a central power tower and we'll talk about that as well here's a parabolic or Solar troughs and the troughs uses curved mirrors to concentrate the sunlight in a small area that runs along these curved mirrors these usually contain very oily substances that can absorb a lot of heat energy and they are actively pumped as it moves across these curved mirrors the sunlight will fall on them and will heat them up so oil heats the temperature as high as about 400 degrees Celsius or 1750 degree Fahrenheit so he does get very very hot power towers use the Sun tracking mirrors to focus its energy into a receiving tower and I'm sure if you have driven to Las Vegas recently you may have seen this so this is 15 and that Las Vegas is on this side and California is down here as you move on the left-hand side you probably have seen these huge towers with these mirrors and the idea is you're focusing the sunlight to that Tower and you're heating up this tower and has oil in it that can absorb a lot of energy and these high-pressure high-temperature oil can be used to generate electricity now let's talk about wind power wind power is a very promising renewable energy in fact the price of the wind power is decreasing the capacity has risen as well the price has gone down and the production has increased there are many countries that are utilizing the wind power China is one of the largest producer of electricity using wind power the United States Germany and some other countries there is a wind energy power plant in Texas that is the world's largest wind farm they have about three hundred four turbines in 47,000 acres they produce enough electricity to power 20 60,000 homes and the capacity for wind power has increased dramatically within the last few decades the way the wind power works is that as wind blows into a turbine which turns the blade the movement of blade turns the turbo generator this is exactly the same way in which power plants produce electricity this physical movement turns a generator and produces electricity and the wind could provide 20% of us electricity by 2030 there's a map of us wind Jenner in capacity so depending on the color it tells you the different wind speed when you're a bluish purplish color it means that there is a high capacity to utilize the wind to generate electricity so once again here we are in California right and also not just in California near Palm Spring in these areas these Shore has much capacity much capacity for collecting the wind energy and turning that wind into electricity some of the drawbacks related to wind energy is the fact that to win isn't always consistent it's intermittent so that it requires some kind of backup energy and for many people the fact that wind farms are really big and they're not very visually appealing and that is an issue for people who live near the ocean where offshore wind farms are being built hydropower uses the weight of the water to turn to generator and we already talked about this in the previous topic as this very heavy water falls down it turns the turbo generator so we can actually utilize this in dams where hydroelectric dams can use a flow of the water to turn the generator to generate electricity in the United States it generates about 6.6 percent of electrical power there are about 300 large dams mostly in the northwest and southeast unfortunately people are realizing that the drawbacks of dams are becoming greater than the benefits so that there is a trend in which people are trying to or the government are trying to tear down the dams and let the natural flow of water in these rivers what are some the benefits of dams dams eliminate costs environmental impacts of fossil fuels in nuclear power because it generates electricity using renewable energy dams also provide flood control in irrigation water and there is a lot of water a lot of rain it can hold out water and release out water little by little so that it prevents flooding reservoirs can also provide recreation and tourist opportunities one of the disadvantages of dams is the fact that once when you build the dams behind the dams water needs to be collected there are often farmland and wildlife habitats and towns that are built along the river now when the dams are built it needs to have greater area to store all of that water so some of those area will be drowned as a result and will displace people dams also impede or prevent migration of fish can we build more dams sure we can and most of the large rivers are already dammed in the United States there has about 87,000 dams are 6 feet or higher and people are beginning to realize that the benefits may not justify the ecological and sociological impacts of these dams the largest dam in the world is a Three Gorges Dam in China on the Yangtze River it was completed in 2006 its length it's about 1.4 miles does anyone know how long it takes to walk 1.4 miles it takes a long time right it has displaced about 1.2 million people in order to store all of that water behind the dam and it does generate a huge amount of energy similar to dams water in the ocean can be used to generate renewable energy there are two ways to utilize this ocean energy one is called wave energy in which as the waves come in here in this picture as waves come in air on top of this column gets concentrated and it will exit out through this vent and this vent is connected to the generator to turn that generator to to make electricity in coastal areas we can use the difference in height between the high and low tides to generate electricity here in this picture at high tide when there's more water on one side compared to the other the movement of water from higher tide to the Lord tide will allow the rotation of the generators to generate electricity when you talk about renewable energy people don't actually talk about biomass energy and that's because biomass energy although it's renewable it's not as clean as some of the other renewable energy so biomass energy is energy derived from present day photosynthesis so anything that grows can be used as biomass energy it's most used for heating it's produced by burning wood municipal waste generating methane or producing alcohol by growing your plants to burn later that would be a biomass energy or growing your corn to produce alcohol that would be biomass energy so some of the examples of biomass energy includes wood biogas biofuels such as ethanol and biodiesel we can use palletized wood to burn and generate heat inside a home because they are compacted palletized wood they tend to burn for longer periods of time and they do contain a lot of energy 2.5 million US homes use only wood stove for heat well the wood stove itself may be dirty it is nevertheless a renewable energy source facilities can also generate electricity by burning municipal waste wood and agricultural waste another form of biomass fuel is biogas an example of biogas is methane gas biogas is a mixture of different energy produced by breakdown of organic matter in the absence of oxygen or in an N aerobic condition this is utilized more in some of the rural areas in India and China even here in the United States are our large facilities that uses digestion chambers to efficiently digest and aerobically to generate biogas which in turn can be used to generate electricity so anaerobic digestion of sewage sludge can produce methane gas here in this picture animal waste is put into these underground chambers to decompose and aerobically to generate biogas on the other hand biofuels are similar to gasoline except that they are produced from organic matter either from plant and animal waste an example of biofuels is at the Arco or ethanol or biodiesel both fuels produce only 2.5 percent of global transportation fuel but this is just the beginning we are using more of our crops to generate more biofuels ethanol is produced by fermentation of starches or sugar that uses either corn sugar cane or other grains production costs make it more expensive than oil but if the crude oil price goes up biofuels can match petroleum fuels about 1/3 of u.s. corn is dedicated to producing ethanol now is this good wise it's hard to say biodiesels are largely made from soybean oil so you have to grow a lot of soybean and instead of using as feed or to feed people you're turning the soybean into oil instead it is competitive with petroleum diesel fuel what would be another promising renewable energy that is recently being more cost-effective hydrogen energy is one of those cars can be adapted to run on a hydrogen gas hydrogen like electricity is not a fuel itself it is a secondary source of energy it is an energy carrier just like electricity the only major byproducts of burning hydrogen gas is water so it's very very clean when you have two hydrogen gases react with oxygen gas you produce water and lots of energy but there's almost no hydrogen gas on earth so you have to produce hydrogen gas by using electricity how do we do it we call this electrolysis it extracts hydrogen from water which requires large amount of electric current once again hydrogen although in itself is very clean and renewable in order to produce hydrogen gas you're gonna have to use electricity and to generate electricity you're gonna have to unless you're using photovoltaic cells you're going to have to use primary source of energy to make electricity to generate hydrogen gas and remember the second law of thermodynamics in every transition of energy there is loss of usable energy now one way to utilize hydrogen gas into more practical energy is called fuel cells one of the benefits of fuel cells is that it can convert hydrogen gas into electricity almost immediately when the electricity is needed fuel cells are forty-five to sixty percent efficient and it produces less heat but of course to get hydrogen gas you're gonna have to use a lot electricity right the way the fuel cells work is once hydrogen gas enters in to a chamber you will go through a membrane and this membrane will strip an electron from the hydrogen gas and the electrons will flow out and basically this is your electricity the hydrogen gas that is stripped off its electron becomes hydronium ions and these hydronium ions will enter into another chamber in which it will bind to oxygen gas to make water so this electricity can be used to run an electric motor just like any other electrical vehicle doubt you've heard of like Tesla or Prius I know that octa has at least one hydrogen fuel cell bus once again the difference between a battery-operated transportation vehicle and hydrogen fuel cell vehicle is the fact that electricity is stored in these hydrogen molecules or as in other electrical vehicles electricity is stored in the battery in itself the levelized cost of energy is a measure of a power source that allows comparison of different methods of electricity generation on a consistent basis this is a way for us to compare different sources of energy and looking at the cost effectiveness in the long term it is an economic assessment of the average total cost to build and operate a power generating asset over its lifetime that's divided by the total energy output of the asset over that lifetime so this gives you an average energy generated by a power plan factory in its lifetime so higher the cost per megawatt of energy it means that it's less cost-effective so what is the most expensive form of energy well solar thermal energy is probably the most expensive it goes anywhere from 200 megawatts $200 per megawatt-hour to all the way to $380 per megawatt-hour we've talked about two ways to utilize wind energy one is offshore and onshore offshore wind energy is still high or expensive than onshore when energy the price of onshore wind energy really has gone down and it's becoming one of the most efficient way to generate energy solar panels are still relatively expensive compared to other sources of renewable energy as well as non renewable energy advanced nuclear energy is still more expensive than conventional coal hydro power is more efficient the most inexpensive source of energy is geothermal meaning using the heat of the earth to collect heat or generate electricity however in terms of more utilized form of powerplant natural gas that uses advanced combined cycle is one of the cheaper form of energy so here in California more than 50% of electricity is generated using natural gas advanced combined cycle but you can see when energy is being utilized more now and as solar panels becomes less expensive that will be also vastly utilized alright that's it for this lecture if you have any questions make sure to go over the lecture slides and perhaps you might want to re-watch this video and if you still have questions send me an email make sure to complete your online quiz and that's it take care