Loading

Alison's New App is now available on iOS and Android! Download Now

Study Reminders
Support
Text Version

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

So to conclude our discussion on the magnetohydrodynamic power generation process so, the magnetohydrodynamic power generation process enables us to generate power from hot gases without moving parts. So, I think that’s something that we have to emphasize here, normally we are looking at you know in any thermal power plant and so on, you are looking at some moving part. So, that there has to be a moving part eventually, eventually you will have to have turbines that are running that turbine rotating and that turbine has to be connected using a shaft and some gear system to a generator, and there you will have you know you will have conductors which are moving relative to a magnetic field and generating electricity right. So, at the end of the day, there is a lot of moving parts there which are required to convert the thermal energy that’s available in your incoming stream to electricity in your you know coming out of the generator. So, typically we require that, but the magnetohydrodynamic method of generating power creates a situation, where you can get electric power from thermal energy in an incoming stream without having any moving parts. So, we are not talking of the electrons and ions as parts, where they basically part of a gas stream which is moving, and so we don’t have any physical parts the solid objects that are moving. So, that is the thing it requires high temperatures, and here we are trying to our best to get away with the most reasonable amount of temperature we can go to without going too high, normally you are looking at you know if you are looking at many other many of the materials that we would know which we can ionize you are looking at few 1000 degrees centigrade requirements to ionize, and create plasma. Here you can get away with a little lower temperatures because you are using caesium and potassium. So, hopefully, you can get away with a relatively lower amount of temperature in the scheme of ionization so, but it is still a high temperature in the overall scheme of things. As I said it is usually not done in isolation it is usually combined with a regular thermal power plant. But and it appears at the top end of that stream it appears at the earlier part of that stream, and that is how we first pick up some energy from this the incoming stream, using a non I mean; non-moving part process, and without using this heat engine in the conventional sense, we just get electricity straight out of this stream, and then we send it to the thermal power plant. Of course, the; I mean the only other issue that we have to keep in mind is that it can have implications that are related to toxicity because you will have some of these ions which will show up in your exit stream, they will be present in the waste material that you generate from this stream, and the ash that will that comes out will have caesium potassium etcetera. So, you may need to do some cleaning process to get these out of the stream before you throw it out throw out the waste so to speak, and so that is an aspect of this technology that you have to pay attention to in the form of during the implementation process.
So, that is something that you have to keep in mind. So, that then is our you know summary of what the magnitude of the hydrodynamic power generation process is. And as I said it is not a very common kind of you know power generation process that we will be hearing about a lot, and that is the reason why most of us have not heard about it;
however, it is something that people are definitely interested in and very keen and on looking at, because it increases the efficiency of existing power plants. So, existing power plants efficiencies can go up; however, you are putting in an additional part of the plant. So, there is some cost involved in it and you may also need additional parts to do the cleanup of the ash after it has been generated. So, you may need additional parts. So, there is some you know infrastructure that is required some cost involved with that that is present here. So, it is not without cost implications and that is the reason why it is not really caught on because people look at other ways in which they can you know in improving efficiencies of power plants. And in and given that there are competing technologies you have to look at the overall cost implication before you can really consider this as something that you really want to push, and that is the reason why it is still not as widely prevalent as I know many of the other technologies that we have spoken about ok. So, that’s our summary of the magnetohydrodynamic power generation, and an overview of how it works, and an in what is the context in which we look at this generation process. So, now to this concludes the range of you know power generation activities and non-conventional energy sources activities that we discussed through this course. (Refer Slide Time: 39:50) So, I would like to spend a few minutes just to summarize what we have done in this course. So, we started you know with this 1 number we did some initial introduction where we looked at the usage of energy around the world, in particular, we looked in great detail at you know how it varies from nation to nation, how it varies per capita from nation to nation, and also we looked at various things like you know how does it vary by sector. So, how does the industrial sector use energy how do you know residential sector use energy, how does the automotive sector use energy, which nations use energy more, which you nations use energy less, in the nation donation what is the difference in the mix of energy that they use the sectors which use more energy in specific nations and so on? So, lot of detailing we looked at of this kind of you know pieces of information, and we also you know pulled all this information together by saying that human beings on average are using 500 exajoules of energy each year right. So, this is the thing that we saw we also looked at it is the impact on the environment we saw you know that this idea that we don’t make a difference to the environment is actually very misleading that even in the space of 50 to 100 years you can easily double the amount of CO2 in the environment, if you do nothing different, if we just continue in a current manner you will increase the CO2 content 100 per cent in just 50 to 80 years which is well within our lifetime, and the fact that you know there is very strong evidence that suggests that if CO2 per cent goes up in the atmosphere temperature goes up. So in fact, we also looked at the idea that you know the information that you know a planet like Venus is so hot because of the amount of CO2 that is present. So, there is overwhelming evidence that carbon dioxide in the atmosphere raises the temperature, and this overwhelming you know is even simple calculation shows you that when you burn fossil fuels at the rate at which we are presently burning fossil fuels, you can double the amount of CO2 in the atmosphere in you know 50 to 80 years. And also the fact that we already are at a level of CO2 which is higher than what has existed in the planet in 100s of 1000s of years ok. So, we have already in the last 50 to 100 years we have reached a very unique situation concerning the amount of CO2 in the atmosphere, and we are likely to double that in then the next 50 to 80 years. So, that’s the context in which we looked at this all the technologies that we have discussed in this course keeping in mind that there is a major environmental implication here, and therefore we need to do something about it. And non-conventional sources of energy offer us many options which are cleaner and therefore, we should look at them in this context we spend a lot of time looking at solar energy because as we said you know it just comes down on earth we are doing nothing it is already falling on us most of the time we are complaining about it saying it is, so hot and so on and but that is the energy that we can tap, and if you can tap it nicely, then it is very convenient to us we have solar thermal energy that we can tap we have solar photovoltaic energy, that we can tap and this energy is coming down to us roughly at about 1-kilo watt per meter squared that’s following on us. And in fact, every hour we are getting enough energy from the sun that more than exceeds this that matches or exceeds this 500 exajoules of energy that we require for the entire year. So, even with a lot of inefficiencies if you just knew how to tap solar energy properly all our energy requirements are taken care of in a very nice manner. We then looked at wind energy we looked at different forms of wind turbines horizontal axis, wind turbines vertical axis, wind turbines we looked at the limits of efficiency of the wind turbine the bits limit so to speak, and we try to understand what we can do in this context how much I mean, and also the fact that it is a very benign form of capturing the energy, it is indirectly a solar energy-based system because the solar energy is what creates the temperature variations, which results in this movement of wind across the globe. We looked at the ocean thermal energy conversion, where we basically looked at the difference in temperature between the top surface of the ocean, and water which is about a kilometre down, and there is enough difference there off the order of about 25 degrees centigrade, and that is there in with large thermal mass this large thermal mass that is sitting with this temperature difference, and then even though the temperature difference is not much and that you are going to get only some small amount of energy out of it the efficiencies are low. Still, because it is just there sitting there and there is nothing else that is it is a very benign way of in which you can capture this energy, you can keep on doing this and you can easily set this up; so, that you can get a lot of energy to augment your energy sources. We also looked at geothermal energy. So, while OTEC is something that is now really relevant only for people who are in the coastal area. Geothermal energy is really relevant to people anywhere in the world I mean anyway I mean the world people could use this, of course, traditionally the use has been closer to regions where there are faults underground. So, that you can reach this hot temperature much sooner, in with much at much lower depths, and then using that higher temperature you can you know convert water to steam, and then use that energy to run a turbine. So, it’s very clean because you are not really burning any coal you are simply using the heat from under the ground. So, that is geothermal energy we looked at biomass basically implies that you are burning plants, and trees and some product of plants and trees to generate your electricity or converting them to some you know converting corn to some form of liquid fuel and then using it, it has pros and cons because as I said on the 1 hand it is considered clean. After all, you are only reducing carbon that was already captured by the plant.
But on the other hand, you have issues such as you may be releasing a lot of other gases or environmentally hazardous gases also out into the atmosphere, and the efficiency with which this the plants will give out the energy or the wood will give out energy calorific value may be less, and so you may end up burning more of those plants. And also you have to keep in mind that you know a tree takes anywhere from 50 to a 1000 years to grow and that is how long it has taken to capture all that carbon, and I know you know sort of sequester that carbon so to speak and, but when you burn it the same tree can be burnt in 5 minutes based on which plant you are putting it to use in. So, you are releasing the same carbon dioxide in 5 minutes what was captured in you know to say a few 100 years well has been released in 5 minutes, and that is exactly the problem that we have now I mean it’s not that we are suddenly creating this carbon from somewhere, but all this carbon that was captured by the environment by the earth over millions of years is being released very fast, and that rate of release is just not accepted we are not capturing it back at the rate at which we are releasing it. So, in that context, this is not you know very good energy to form of energy to look at today even though people will argue that it is you know 0 carbon footprint and all that they will argue, but this is the problem that time scale is just not the same, if you want to capture all the carbon back in 5 minutes you have to capture you know to plant a huge number of trees you may have to know they will fill the planet with trees to just capture the same amount of carbon back in 5 minutes. So, that is something that you have to keep in mind then we also looked at batteries, and fuel cells which are interesting ways in which we get electrical energy using from the chemical energy, and both batteries and fuel cells are essential in the grand scheme of non-conventional sources of energy because most of them require some most of the other forms of non-conventional sources of energy require some energy storage require some you know flexibility, and how that energy can be used with time and batteries, and fuel cells play a very unique and you know important role in that scheme. We also looked at supercapacitors and flywheels, mainly because they offer a different combination of specific energy, and specific power relative to say just batteries or plain capacitors. And so they fill in the sort of fill in the blanks between batteries and capacitors in terms of serving an energy requirement, and usually, they deal with situations where the transition in energy is high. So, you are going from you know you are suddenly accelerating a vehicle, suddenly applying brakes to a vehicle, and so you want to capture the energy very fast you want to release the energy very fast, then batteries are unable to do that capacitors are capacitors can do that, but only for an extremely small fraction of time. So, supercapacitors and flywheels bridge that gap, they give you a significant amount of energy released over a period of a few minutes, and that is really what is a few seconds; to a few minutes which is what is necessary for several applications where the transition is the important thing that we are trying to cover ok. So that is the context and finally, today we looked at magnetohydrodynamic power generation, which I told you is an interesting way in which you can increase the efficiency of plants that generate the power plants that generate electricity. And but it is still not a very common way of an in which it is utilized, but it is something interesting that people are looking at, and it’s at least 1 of those things that we should be aware of because that gives you ideas maybe of other ways in which people can try and look at the improvement of efficiencies of plants ok. So, with that we conclude this course I hope you enjoyed it, I hope you found it beneficial, and I hope it gave you a very good perspective of non-conventional sources of energy. Thank you.