"Smart" Energy – Future Energy Infrastructure – LEAP Links Video Conference

My name’s Graham Town, I’m from the department of engineering here at Macquarie uni I’m a member of the Sustainable Energy Systems Engineering Group My current focus in research is on energy and in particular electric vehicles And today I was going to talk about energy in general and then move towards energy infrastructure And we’ll finish with a little bit about electric vehicles in that Just a bit of background about me, I’ve done a whole range of things in my career, I was an engineering trainee with AWA for eight years where I worked on electronics and communications stuff I did a PhD in medical imaging I then did a lot of research in photonics But the last five years I’ve really been concentrating on energy technology in systems because I think this is a big problem for all of us over the next couple of decades I’ve got a mandatory bad joke to get your attention and get things going So what’s another name for a silly old man or woman? One, two, three, a fossil fool Good, one person laughed Okay, so this is the overview This is where we all live, we share this space We, and everything we do, life runs on energy And life has been described as sort of a thin film on the surface of this earth But ultimately, what powers that life comes from– energy comes from the sun in the form of either stored energy in fossil fuels, or in sunlight, wind and waves, those sorts of things So this lesson is about energy, about how we use it, how we manage it, and how we can get smarter in how we use and manage it Actually, we’ll have to do that over the next couple of decades, so this really affects you guys quite directly This is an overview of the talk I won’t read through all of this stuff, but there’s a lot in the slides And I’m not going to get a chance to cover everything, so we’ll skip through some things to keep the time If you have any questions at any time, maybe just wave at me, and I can stop and we can have a discussion around that point At some points, I’ll stop and maybe ask you questions as well The last point there – the talking point – one thing to think about as we work through this presentation is, how do you think energy infrastructure will change? And by infrastructure, I mean the poles and wires that bring electricity to your houses, the coal and the petrol that’s mined and powers your cars and industry so on How is all that going to change going forward? And can we draw any analogies? Can we learn anything from history and the past with energy? So a definition of energy – you probably know this stuff – you can change energy from one form to another And you’re probably familiar with some of these different forms energy – electric, magnetic, thermal, mechanical, gravitational, and so on I’m not going to go into too much detail about those things I’m going to talk in general terms You can also define two classes of energy as kinetic energy and potential energy, which you’ve probably heard about in connection with objects that have mass Something that you may not have heard about is a grade of energy We can talk about a grade of energy, which has to do with system disorder So for example, thermal energy is a low grade of energy compared to electrical or chemical energy Do you have any idea why that might be? So basically, it’s easier to turn electrical or chemical energy into thermal energy That’s going down the grade Than it is to turn thermal energy into electrical or chemical energy So depending on which direction it’s easy to go in, that tells you what the grade of energy is Energy is fundamentally related to forces Work or energy is force times distance – you’d be familiar with that idea – whether it’s nuclear, electromagnetic, or gravitational And of course, you measure energy and the units of energy in joules Work can be positive or negative, depending on whether energy is going into or out of a system And don’t get confused between energy and power Power is just energy per unit time or work done per unit time Energy is an amount, and power is a rate And sometimes, people get mixed up between the two So where do we get our energy from?

These slides are from various websites, and you can get the details off the slides This one’s a few years old, but it shows you the breakdown of where we get our energy from – different sources And largely, it’s fossil fuels The large ones down the bottom there are coal, gas, hydro, and so on The renewable energy sources such as wind and photovoltaic are only a few percent at the very top Now, why is this? Why do we get most of our energy from fossil fuels? Well, there’s good reasons for that They’re high in energy density When you burn fossil fuels, you get a lot more energy out than you would by burning some other things Also, fossil fuels are easy to transport You can put them in your car They’re relatively safe and easy to use So that’s why we’ve got an industry now built around fossil fuels But, they have impacts And you’d be aware, probably, that when you burn fossil fuels, you get carbon dioxide emissions And it’s interesting to look at what the applications of energy are that produce these emissions One is generating electricity, and the other one is transportation And then, there’s a group of others including agriculture So about a third of the fossil fuels that we burn to produce energy and do things with go into generating electricity which then goes on to doing other work And another third goes in transportation Just driving around, moving products around, moving society So they’re two very large applications of energy Particularly, transportation – and to a large extent, also, electricity – are derived from burning fossil fuels Coal, in the case of electricity Petroleum, in the case of transport Now, this diagram looks relatively complicated But basically, on the left-hand side, you have sources of energy going in, then you process them in some way And then, on the right-hand side, you’ve got use for work coming out And again, you can see in the pink boxes, the breakdown between the amounts of energy used in transport, residential, and other applications You can also see how much goes through electricity generation The bulk of petroleum goes into transport, and the small proportion of that – about 5% – comes out as actually transport movement The larger part of that comes out as– the 21% of the total comes out as heat or rejected energy In fact, when you look at the balance of what’s going in and what’s coming out, most of the energy inputs end up as heat or rejected energy They don’t actually end up as useful work or useful outputs So that’s maybe a problem, there’s some fundamental limits there but that’s something worth being aware of So when we’re using energy, particularly fossil fuels, a lot of it is ending up as waste And additionally of course we’ve got carbon emissions So again you can see the breakdown there between the inputs and what carbon is produced from what applications In Australia it’s pretty similar to the rest of the world I’m not going to go through the breakdown of this in detail but some interesting numbers to note there are that we consume about a total of 6000 petajoules of energy per year And we produce about 20,000 petajoules per year so we consume less than we produce which means I guess we’re either storing or exporting quite a lot of energy If we look at the solar resources we have So I’m going to focus on solar energy for a moment This map gives you solar irradiance across the whole world And you can see that in Australia we’re pretty well endowed with solar energy About the only place that you would say has more is Africa So we’ve got a lot of solar energy I could show you the same for wind, we’re also pretty well-endowed with wind energy This table gives us a comparison between different forms of energy that we have in Australia And again, we’re very well-endowed with all these different sources of energy Unfortunately, it’s a little bit difficult to convert between the units of the different types there But if you look at solar potential – potential solar energy – it’s 25,000 million million watt-hours per year So energy, in this case, is measured in watts times hours How much space on the Australian continent do you think would be required to produce that amount of energy? Well, you can go through the numbers And because the numbers are pretty big, I’ve put down a table there of the SI prefixes that apply here So 10 to the 9, you probably know, is giga 10 to the 12, you probably haven’t heard, is tera And I haven’t even looked at 10 to the 24,

which is yotta But anyway, they’re pretty big numbers Now, if you considered that about 4 kilowatt-hours per meter squared per day of solar energy falls on Australia, and you multiply that out, you get about 1.5 megawatt hours per meter squared per year Or if you convert that to joules, then you get about 5 gigajoules per meter squared per year and if you look at, remember on that previous slide it was 6000 petajoules of energy that we use in Australia per year You divide the numbers out, you need an area about 34 kilometres by 34 kilometres covered in solar cells to produce the amount of energy that we use in Australia every year Ever if you take into account inefficiencies it wouldn’t be more than 70 to 100 kilometres square of area If it was all converted to solar energy produce more energy than we need per year I haven’t talked about climate change or global warming or anything of those things yet You probably have heard of these things And the question is if we keep on going, keep on using fossil fuels the way that we have been, what’s going to happen? So my question to you is what do we need to do about energy? Save it, that’s a good answer, yes That’s one of the things that comes down the list actually So what I had here was stop using fossil fuels basically because it’s damaging the environment But the question, that’s one of the answers There’s actually other reasons why we need to stop using fossil fuels and move more to renewables What would those other reasons be? Absolutely so climate change is the first one, cost is the second one and the third one you just got which is sustainability Fossil fuels are a finite resource And actually if we keep using them at the rate that we’re using them now, they’re probably going to, at least petroleum is likely to run out sometime in the second half of this century So we’re going to have to find alternatives anyway Okay, so two alternatives to using fossil fuels include, so okay, I’ve put them back to front unfortunately, but using sustainable sources of energy, finding alternatives, renewable energy sources is the one And Anthony’s already mentioned the other one which is using less energy, whatever form of energy is, just use less of it So improve the efficiency with which we’re utilising our energy resources, and then even if it’s fossil fuels it will last longer So what I’m going to do now is go through in a little bit more detail each of these reasons and then we’ll get on to a bit more about infrastructure So as far as the options go, renewable energy, so you’ve probably heard that we’ve just passed I think 400 parts per million of carbon dioxide in the atmosphere It’s never going to drop below that again until we reduce our carbon emissions and this is having an impact, and it will have an impact increasingly on the climate For example extreme weather events and it can also threaten the food chain both on land and in the ocean Carbon can result in acidification of the ocean which can hurt the small animals which have calciferous shells if you like And they are the source of the food chain, so everything comes from them If we damage them, we damage everything else So that’s one of the reasons and I don’t think I need to go into more detail about that I’m not an expert on climate change by any means but it’s one of the motivations for me to think about better ways to use energy Another reason is cost, and this one is often not considered, but there’s a lot of subsidies going to fossil fuels these days And if you added up the costs you’d probably find that actually a lot of the renewable energy sources are similar cost or even less expensive than using fossil fuels after the subsidies had been taken away I’m not going to go into the details of this, you can read the text of this But it’s certainly a reason to move away from fossil fuels, it would cost less in the long run And the third one you’ve already mentioned

is resource depletion If you look at the graph on the left there you’ve got the red lines which is up until now Our consumption and discovery of petroleum oil And then from about 2010 on or around now on, what’s happening is that there is a growing gap between the fossil fuels that we’ve discovered or the petroleum that we’ve discovered and the petroleum that we’re using And in fact we’re using petroleum at a higher rate now than we’re discovering it so we’ve passed what some people would call peak oil which means that it’s going to run out sometime in the future and according to this graph it’s about 2050 What’s going to happen of course is as oil becomes more scarce and less available the cost is likely to go up and that improves the economics of renewable energy as well So yeah, at current usage rates oil will run out around the middle of the century Here’s another interesting plot which I found in the literature, and it links human population to sources of energy So basically what it’s showing is a number of different sources of energy along the bottom there from firewood, coal and oil Oil is the big white peak, and it’s traced population in millions on the left hand side against that So you can see that as energy and fuels have become more available, population has grown almost along with it So the question then is, if we run out of fossil fuels, which has been our major source of energy in the past, what’s going to happen to population? According to this graph, it could plummet half or whatever over the next century It’s probably not quite that simple Can you think of anything else that has caused an increase in population over the last century or so other than our use of oil? Rather than let you stew, it’s healthcare basically So healthcare’s improved The health of the general population’s improved And so survival rates have improved If we lose energy we don’t necessarily lose the benefits of healthcare It may suffer, but we don’t lose that entirely So whether the population decreases when our energy resources decrease or not is a question that we probably can’t answer It really depends on how we manage that energy, which is what the rest of this presentation’s about But certainly it would help if we could use less energy And then we would avoid reducing our population and also maintain our living standards So using less energy is the key That’s important And then the other strategy is to replace fossil fuels with sustainable energy sources There’s a difference here between sustainable and renewable I’m not sure if you would know what it is but let me ask It’s actually on the slide Renewable means naturally replenished so we’re using it but it’s always being provided Sustainable could be nuclear energy for example because it keeps, nuclear energy at the moment, there’s more than we need for the next couple of centuries Ultimately though that one would run out as well So calling that one sustainable, it’s all relative Okay, some practical considerations around energy How we use energy and whether we use it depends on a number of things Is it available on demand? Sunlight is not available on demand, you have to store it if you want to use it at night time So you would be taking photovoltaic energy, storing it in a battery and using it at night if it’s not available on demand is one example You can also store energy in thermal, mechanical, chemical, other forms than electrical Is the energy available where you want to use it? If not then you have to be able to transport it So that’s why we’ve got pipelines all over the country, and electric wires all over the country They are transporting energy from where it’s produced to where it’s used, largely in the cities Also, is the energy in the form that you need it? If you want to use electricity, then you’d prefer to get a wire to your house But if you’ve only got chemical energy coming in or mechanical energy, you have to convert it to electricity So then energy conversion matters It’s required And efficiency with which you convert energy matters And as I mentioned before, converting energy from higher forms to lower forms is easier than going back up the chain

So the last 5 or 10 minutes I’ll talk about energy infrastructure and electric vehicles So this is a map showing evolution of our electricity generation and distribution system from the past to the future It’s from the International Energy Agency In the past, everything was centralised in terms of generation And then you had wires going out to all the consumers, which there were many of And they were distributed around So energy flowed from the generators to the consumers one way And the generators and the distributors controlled the network The consumers didn’t really have any control over the network Currently, we are in the middle In the future, we’re going to have much more distributed energy generation That means photovoltaics on roofs, fuel cells in garages, wind spread around and so on And that distributed energy is going to need to be connected to all of us through our existing infrastructure and new infrastructure And moreover, it’s going to have to be managed And we’re going to be more responsible for our own use of energy And this means in order to do this, there’s not only an electrical infrastructure, wires connecting us to the sources of energy, but communications will be monitoring and managing how that energy is distributed And used in the network And this is the huge challenge for particularly electrical engineers over the next couple of decades to implement this smart grid or we’re starting to use a term called the internet of energy You can think about future energy systems as working a little bit like the internet What do you think one of the advantages of having distributed energy might be? Think back to analogies with the internet One of the reasons the internet was invented was so that we would have communications which was robust, for example in a war, if part of the communication network got taken out, the rest of it would continue to work That’s how the internet works, it’s distributed You take out any one part of it, the rest of it still works If we have an energy system that is the same then again, you take out one part of the energy system, the rest of it still works And it’s not necessarily going to be taken out by war It could be extreme weather events such as we saw in South Australia the other week So if you have a distributed energy system, hopefully it will be more robust and more people will keep energy, a reliable supply of energy than if it was centralised and then yeah if the generator breaks down everyone loses out It’s also more efficient and potentially lower cost and so on as well, I’ve mentioned those reasons there Okay, there’s enabling technologies for the smart grid, one is information communication technology The other one is storage, absolutely critical for renewable energy which is variable over time and place The good news is that the cost of battery storage has been dropping rapidly, about halving every three years So we’re going to see batteries become much more common in households and in energy systems generally to allow more and more renewables into the system Another enabling technology is power electronics which is another one of my research interests Basically things are getting smaller, so again like communications technology, we had mobile phones which started out the size of bricks, now they’re the size of a packet of cards Our electronics and that technology is going in the same direction Okay, energy and transport, in a couple of minutes I’ll try and cover this So I mentioned before, transport consumes about a third of the energy that we utilise overall It can’t be ignored Also you probably have– I don’t know, has anyone, have either of you seen an electric vehicle on the road where you live, raise your hands if you have You have? Fantastic Okay There’s not many around in Australia, but the numbers will be increasing I think quite rapidly over the coming decade In fact the predictions are that there will be about a million electric vehicles on the road in Sydney in 10 year’s time Already in Norway, 20% of vehicles, new vehicles, are fully electric, and that’s for a number of reasons I won’t go into There are other parts of the world where electric vehicles are becoming much more common I think of as an electric vehicle as a battery on wheels Because in an electric vehicle you have a battery which is much larger than the battery that you might put in your garage Now this is good and bad because you have to charge the battery, and it can take time depending on the size of the battery And that can also load the grid where you are if you’re plugging it in On the other hand,

you can also take energy from your electric vehicle and put it back into the grid if you need to And this is called, well okay, here’s a little joke, green transport, does that look like green transport? Or that? This is a Dendrobium It’s faster than a Tesla You’ve heard of a Tesla? Okay, this one does 0 to a 100 in about 2 seconds So yeah, that’s the evolution of electric vehicles The cost of vehicles is low so one of the questions I wanted to put to you was, why don’t people get electric vehicles? One reason they usually give is cost But actually if you look at the numbers, it’s cheaper to own most electric vehicles lifetime of the vehicle than an internal combustion engine vehicle Another reason people give is range, it won’t get me to where I want to go Living in the west of New South Wales, okay, that might be a reason But living in Sydney or a major city, almost anywhere in the world, it’s been shown that 85% of people don’t need the range of an internal combustion engine vehicle An electric vehicle, your average electric vehicle would be perfectly adequate And we’ve found that for Sydney as well, we’ve done a study on that in Sydney Charging infrastructure, there’s nowhere to charge up your vehicle, that’s the third reason people usually give Well that’s going to change in future too fairly rapidly Here’s a couple of pictures of what a typical charging station might look like You’re getting shade as well as energy at the same time The one on the left, any surplus energy goes back into the distribution grid, the one on the right, there’s a couple of batteries there So this is a portable solar charging station, it’s not actually connected to the grid at all The energy that’s produced by the solar cells goes into the battery and then when a vehicle comes up it’s transferred from the battery in the charger to the battery in the vehicle Okay, I’m not going to go through a lot of detail in charging infrastructure but wireless power transfer is another method of charging vehicles which is going to become more common At the moment you’re probably familiar with the plugs that you plug into a vehicle, actually they won’t be, they will be a thing of the past So you’ll just drive over a pad and it will inductively transfer the energy into the vehicle This also means that you can transfer energy more easily back to the grid as well So you can have bidirectional energy transfer into and out of the battery in your vehicle through this wireless link That raises some interesting possibilities which I’ll mention briefly in a moment So vehicle to grid I mentioned that yeah, if you have a vehicle you can put energy back into the grid This actually was very useful in Japan You might remember the Fukushima nuclear accident when the tsunami came in and damaged the nuclear power station So a lot of people lost their electricity supplies at that time But in Japan electric vehicles were a bit more common And what they could do is they could take their electric vehicle, plug it into their household, and run their critical appliances from the energy in their vehicle So vehicle to the grid is another way of utilising electric vehicles to manage your own energy usage It doesn’t have to be in an emergency But yeah, it helps us to manage our energy Particularly in the light of more variable renewable sources coming online Okay, charging infrastructure’s increasing That’s the point of that slide but I won’t dwell on that When are where you charge matters, will electric vehicles have an impact on the grid? The answer is it depends I don’t have time unfortunately to go through the reasons here but I’ll leave that one for you guys to have a look at Possible business scenarios, there’s a whole range of business scenarios that might arise around electric vehicles, whether you own the vehicle, whether you don’t own the vehicle A couple of interesting ones that you might have heard of, autonomous vehicles where they drive themselves, they don’t need a driver, they run based on GPS And I can imagine and I hope you can too that you might have an electric vehicle that is autonomous You dial it up like an Uber vehicle, it comes and picks you up without a driver, takes you where you want to go and then goes off, picks up the next person, or if it needs to, it can go to a charging station where it drives over one of those wireless charging pads, charges up and then goes off and goes back into the pool So this is almost like a public transport system but it’s door to door So in conclusion, any energy infrastructure’s going to change substantially over the next two decades, it’s really going to affect you guys We need to use the available energy more efficiently to

make our current sources last longer but we also need to develop new forms of energy, new resources, mainly renewable energy resources And we’re going to see transport become electrified and this will have a big impact on energy as well because as I said, a third of our energy goes on transport currently To do this we’re going to need to develop a smart infrastructure around energy systems and how we manage our energy So intelligent buildings, intelligent transport, and the smart grid which is the one I’ve mostly spoken about here So lots of problems and it’s engineers that are going to be solving these problems in the future In some ways it’s exciting times And I’ll just finish on this picture So ICT is information and communication technology We’ve seen how our lives have been transformed over the last couple of decades by information and communication technology with the internet, mobile phones and so on When you combine that with energy you get a smart grid When you combine information and communication technology with transport you get intelligent transport, autonomous vehicles and so on Now because of the significant link between transport and energy I think that’s going to be the link for and the solution for increasing the amount of renewable energy we rely on and use in our lives going forward So thanks for your attention, if you’ve got any questions, I’d be more than happy to try and answer them Okay, so did I put the numbers on here? It depends on what you’re charging from Here we go, so your typical household charger will charge an average electric vehicle overnight from empty to full But a Tesla vehicle has about 4 times the battery capacity so you’d actually have to charge that for more than a day if it was going from empty to full at home On the other hand there are fast chargers that will charge a Tesla in half an hour But you need a small power station almost to do that So there’s other numbers which I’ve given here In fact, so page 36, there’s 3 or 4 levels of charger mentioned there and the amount of current that they and power that they can provide And for a typical vehicle you would use about 10 kilowatt hours a day Your typical commuter would use about 10 kilowatt hours a day So to replenish that every day on each of those different charging technologies you’d need somewhere between 10 minutes and 4 hours Even in Norway they get a lot less sunlight than we do but the uptake of electric vehicles there is very strong And the reason for that is they have a lot of hydroelectricity resources so what they do is they buy energy from the rest of Europe when it’s cheap, pump water up in the dams and then when the rest of Europe wants it back they sell it back at a higher price or they use it for their own domestic needs So energy trading is the answer to this You need to be able to collect energy in one place and then transport it to where it’s needed, that’s one example in Europe We could transport energy, not in the form of coal, but maybe through a wire, electricity to Indonesia That’s being talked about So we could, from Australia to Asia we could transport energy in that way There’s options Hydrogen is another way of storing energy and transporting it There’s already been wars over oil, I think people would say, in Kuwait and so on Look, when resources get scarce, nasty things can happen And it’s really up to us to foresee this as much as we can and do our best to prevent it through both technical means, engineers are working to provide our infrastructure to make sure people maintain their standard of living But there’s also political means and economic means The more trade we have, the more reliant on each other we are and the less likely wars and things are likely to happen Yes I do and the reason is is that if you look at carbon

emissions in Australia historically, when the carbon tax was introduced, carbon emissions started going down, energy usage started to flatten off, that is we’re using what we had more efficiently and there was more photovoltaic coming into the system When the carbon tax was removed, carbon emissions immediately started going up again So economic levers have a real impact on people’s behaviour And if we want to change the way people are behaving that is another way of doing it Energy trading, sorry, carbon trading is another approach There’s arguments for and against taxes versus trading and capping trade I’m not an expert and I can’t go into that now, but certainly economic tools for managing people’s behaviour are important Selling it politically is a challenge but it’s important I’m aware of buses, electric buses that are being produced and actually used, quite large buses I think that’s the next thing that we’ll see becoming more common but of course agriculture and all of that industry depends on heavy vehicles also Whether they get run off batteries or maybe hydrogen fuel cells is a question I can’t answer A lot of forklifts used in factories, a lot of forklift vehicles are already run on hydrogen fuel cells and it could go that way for the larger vehicles Pressurised hydrogen has a very high energy density and that’s what you need to run vehicles for a long period of time It comes down to the technology available and the costs and I’d have to have a crystal ball to tell you which way it’s going to go except for the fact that every form of transport is going to have to become electrified, it will have electric motors driving it So you don’t want to put all your eggs in one basket, you want to distribute those solar farms all over the country and one of the advantages of doing that is if you’ve got rain and bad weather and cloud cover in one part of the country, another part of the country is likely to be sunny and so again the weather, these impacts average out and having a distributed energy resource makes it much more reliable and more robust That’s a very deep question which it’s very difficult for me to answer I think I mentioned politics before is part of it, our political system and the priorities of our government as determined by the voters and the interest groups, the miners and others that are part of the democratic system All I can say is when I look at industry, they are actually making the changes They see the economic sense, they see the sense in being proactive in moving to more efficient energy sources and being more efficient with energy and using other energy sources So ultimately it will come down to being an economic thing and people will just say Look, it’s cheaper for me, I’m going to do it It’s not obvious to people at the moment For example with electric vehicles, I think it’s perfectly sensible for most people to have an electric vehicle today Although most people aren’t aware of it There are questions in their minds and they have to be educated or learn to where the truth is for them as well as more broadly So it’s a very complicated question and I don’t think there’s a simple or a single answer but I think you can understand that too I think telling your friends will help, that’s what I’m doing here As more and more people understand and become aware of what’s possible and what can happen if we don’t make changes then I think these changes will happen naturally Okay, so I’m sorry but you’ve– there’s a couple of wrong statements there, okay First of all, carbon doesn’t destroy ozone It’s fluorocarbons which are a different chemical form of carbon All right, so a couple of, few decades ago,

people noticed that fluorocarbon emissions from spray cans and things were causing the ozone layer to thin and eventually disappear And action was taken globally to restrict the use of fluorocarbons and what’s happened is that over time the ozone layer has healed itself Now ozone is produced by sunlight, ultraviolet light particularly falling on the upper atmosphere and interacting with oxygen there So it gets produced at a certain rate If there’s fluorocarbons going up into the atmosphere, it’s being destroyed at a certain rate What we’ve done is we’ve realised the problem and stopped destroying the ozone so that’s healed itself Carbon emissions are a different matter, they form a sort of a blanket on the Earth which traps heat And this changes weather patterns and all the others things that are associated with climate change So hydroelectricity specifically is storing water in dams and then letting it run downhill and converting its kinetic energy into electricity The water gets up there either because it rains and fills up a dam or it’s pumped up to the dam Wave energy is, I wouldn’t call it hydroelectricity, it of course has to do with water, but it’s capturing the energy in waves and converting that to usually electricity using different approaches, slightly different approaches, yeah There’s also tidal energy If you can capture water moving in and out of estuaries then it’s very much like hydroelectricity, you’ve got water flowing and you convert that to electricity It is very regular, the size of tides vary, so it can vary from week to week, day to day, whatever But the tides will always be there You could say the sun is always there, but of course you can’t predict cloud cover quite as well So photovoltaic energy, solar energy, is more variable than tidal energy, absolutely And thanks for the great questions too