 I'd like to spend a few minutes here talking about geothermal energy and I'll end up by telling you what we at Stanford are doing in geothermal energy, but given my previous knowledge and observation about the global understanding what geothermal energy is, I'd like to spend 10-15 minutes and talk about that specifically. Remarkably, a lot of people don't fully understand geothermal energy. We talk about renewable, any slide you ever see talking about renewable refers to wind and solar and we all get that, however geothermal is rarely mentioned. We can think of geothermal energy as the underground source, underground because that's where it is and underground because nobody's ever heard of it. So let me talk about that. I'm going to cover three topics as far as I'm able to in the time allowed today, where we are in renewable energy and the context of geothermal, principally from the point of view of electricity. I'm going to talk about direct use of geothermal in terms of heat pumps and I probably won't have time to talk about enhanced geothermal systems, but that is where our future is going. So as you all certainly know, in the past 10, 20 years, the overall expansion of renewable energy has been almost exponential. This graph shows the United States, but the same is true of much of the rest of the world. So this shows a comparison of, in the dark blue, renewable energy in comparison to hydropower, which you'll notice is declining, hydropower is a wonderfully and long used energy source, but it has some context in terms of where we are today. We've used renewable energy, the first electricity was ever generated came from renewable energy from the source of hydro and it's been that source for more than 100 years. Nonetheless, we can't continue to use hydro in the way that we have in the past and I'll talk in brief about that as we go along. If we compare the renewable sources to the conventional fossil fuel sources over here on the right, we can see there's an important characteristic difference among them and clearly understood by all of you, I'm sure, that the intermittent sources like wind and solar are not available for base load application. So if you want to switch on the light and have it come on any time of the day, any day of the year, intermentancy is an issue. It's not an insurmountable issue and we've clearly made a great deal of progress in that way. Nonetheless, a portfolio of electricity sources has to have different kinds of generation. You can't have a grid made up completely of solar unless you also have storage, which by the way is probably the direction we most likely go. Geothermal, as you'll see on the slide, little red dot, is one of two base load renewable energy sources. It can run 24 hours a day, it can run 365 days a year. And as a matter of fact, that is the way that it likes to run. It's quite hard to run a dispatchable geothermal power plant, which nowadays actually makes an important limitation, actually, on its wider use, because dispatchable power is what our greatest need is for in the current energy market. Worldwide, what you can see here, this is every five years we have a world geothermal congress, we're going to have a new one in 2020, and each of those five years represents a snapshot of where we have come to in worldwide generation. So in 2015, which was the last conference we had about 13 gigawatts, currently we had around close to 14, and a projection is with expansion to get above 20 in the next five years. Who's number one in electricity generation in the United States? If California were a country, it would also still be number one. How many Californians know that? Me and a couple of others, okay, not very many. Few people in the state of California recognize how important a geothermal country we are. But you can see some of the others. Philippines actually, this was in 2015. Philippines was overtaken by Indonesia in the last three or four months. But you can see some of these other countries, and you recognize where they are. Most of them are around the Pacific Ring of Fire. Geothermal activity or geothermal utilization typically is found in volcanic regions. So around the Pacific Rim, in Central Europe, Italy is a big nation. Turkey, remarkably, is now number four. They in the last five years have gone from 400 megawatts to in excess of a thousand. And these are some of the smaller ones. Importantly, what you can see is not just a snapshot in time, but a dynamic situation. So this is sort of a slightly confusing graph. But what you can see is over the five year periods of successive world geothermal congresses, how different countries have grown. So importantly, you can see that, for example, in the United States, we are continuing to expand our geothermal generation. And several countries, importantly, Indonesia, New Zealand, Kenya, and Turkey, are making wild expansions. I mentioned Turkey, but Kenya also is taking up a very large fraction of its electricity grid from geothermal in the last five years. So I'm going to show you three snapshots of the state of California, 2010, 2013, and 2015, as to where we generated our electricity. And importantly, there's a distinction between this table and the graphs that I showed you before, in that this is not capacity. This is actual generation. This is a gigawatt hours that were delivered to somebody's plug. And in 2010, what you see in this list, this includes all electricity sources, renewable and non-renewable. In 2010, geothermal was our largest non-hydro renewable source. And legislatively, for peculiar reasons that I've never understood, hydro is not classified as a renewable energy source, despite being completely renewable. Legally, it's not classified that way. But non-hydro, geothermal was our largest source, 6% in 2010. And in passing, I also want you to remember the number for hydro, 2010. 33,000 gigawatts hours is what was delivered in 2010. You also take note, you won't see it on some of the other tables. Our neighbors in Nevada also generated 6% of their electricity from geothermal in 2010. Currently today, I'll let them have a table of it. The state of Nevada produces 9% of its electricity from geothermal sources. And the reason that that's important is because our resources, our geological resources in the state of California are super high quality. So it's the reason we're number one in the world. We have very cheap, very easily accessible, very high temperature resources in the state of California. Nevada has some too, but they're not as good. They're lower temperature, they're harder to find, and they're harder to produce. And the fact that Nevada can achieve the same sort of percentage in their portfolio, renewable portfolio, is extremely important philosophically in what it means for the rest of the world. If they can do it, they can do it almost anywhere. Okay, so that was 2010. So this is kind of a typical day in the state of California. If you've never seen this website, caliso.com, it's the greatest entertainment you'll find today. You can see exactly where your electricity is coming from right at this moment. So on this particular day at about this time of the day, this was May 24th. You can see a huge fraction of the energy produced from solar. It's greater than that today. Usefully in our state, the wind more often blows at night. Not always, but it's a happy synthesis between the wind and the solar. You can see geothermal somewhat boringly down at the bottom. Just show that one gigawatt running all of the time. On that particular day, however, if you look over the whole 24-hour period, what generated the most electricity? In this table you can see on the right, the megawatt hours. For that specific day, geothermal was number one out of the wind and the solar. There were more gigawatt hours generated for geothermal that day than either of those other two sources. Emphasizing the importance of having basically the ability to produce all of the time. Okay, so let's look at 2013. Moving ahead three years, geothermal there shown in yellow. What you see there, 2013 was the first year in which wind overtook solar as the total generation over the course of the whole year. And if we move to 2015, which is the last numbers I could find, you can see now solar has overtaken wind, so geothermal now is number three. Nonetheless, still 6% of all of the electricity generated in the state of California still today comes from geothermal sources. And that's true for importantly some other countries also. As you may tell from my accent, I am from New Zealand. New Zealand is an important geothermal country too. And currently, New Zealand is 80% renewable, counting hydro. Currently, New Zealand produces 20% of its electricity from geothermal sources. And Iceland produces 80%, two thirds, if you look on the right hand side here, two thirds of all energy in the state, in the nation of Iceland, comes from geothermal sources. And this is not electricity only, this includes heating, cooling and transportation. So that's two thirds of all kilojoules consumed in the nation of Iceland come from geothermal sources. So that's electricity. Let's also talk about direct use, and there's a large list there that I won't read because you can read it for yourself. Mostly agricultural, but also space heating in residences and offices. So this graph shows for the United States all of the thermal energy which we consume in terms of heating, homes, factories, industrial uses, etc. The total for a single year is 100 exajoules. I forget how many zeros that is, but it's a lot. And importantly, what you notice, this graph shows that the x-axis is the temperature at which we use thermal energy. And you will clearly see that most or a large fraction of the thermal energy that we use is at a temperature between 40 and 80 degrees centigrade. And most of it, in fact, between 40 and 60 degrees centigrade. So making electricity requires high quality thermal resources up, and we're talking around 200 to 250 degrees centigrade in California. 150 degrees centigrade in Nevada. But there is a whole lot more thermal energy in the Earth beneath our feet at 40 to 60 degrees centigrade. We need only go to a 1,000 to 1,500 meters depth to find water of that temperature. So here are some examples. Balneology, this is one of my favorites for hot springs, recreational use. Space heating, this is the city of Reykjavik in Iceland. It's shown in the 1930s in the picture on the left where they heated most. It's really cold in Iceland. They heated most of their buildings with coal, of which they have none, all of which was imported from Norway. And the result was this kind of black smog that you see in the left. This is Reykjavik today on a picture on the right. Every building in the city of Reykjavik heated with direct geothermal energy, not just heated, but in fact, domestic hot water. If you take a shower in Iceland, the water smells slightly of sulfur because it's come directly from the ground into the hot water force. And interestingly, actually 80% of the population of Iceland receives reticulated hot water into their houses, which is not remarkable in Reykjavik, which is 100%. But Iceland is mostly a rural nation. A lot of places are very far from each other, little villages or whatever. But even little village with five houses has got a geothermal well and they reticulate that water to those even very small communities. These are the kind of applications that direct uses of geothermal energy go to. Big one on the right is heat pumps. And the interest you can see here in the bars again, this shows the growth, unfortunately going to the left this time. But geothermal heat pumps over here, number one, is the most widely expanding use of geothermal energy in the world. An important thing about heat pumps is that you actually don't need the thermal energy of any kind. You just need kind of a sink, which is the earth itself. Number one for the application of direct use geothermal is China. But there are also some very other surprising nations on that list. Number three is Sweden. Who imagined Sweden to be a place that's hot in the subsurface? It isn't hot at all. There's no volcanoes in Sweden. And yet they have every single building, or at least a very large number of them, heated with geothermal heat pumps. And you can see some of these others too. Switzerland is down at the bottom, but actually Switzerland has one of the most aggressive policies for the installation of heat pumps in all new structures. I think I just said that. So how many of you have seen a heat pump? All of you have seen a heat pump, OK? You all have a fridge in your kitchen. That's a heat pump. It takes the heat out of the kitchen. No, it takes the heat out of the beer and puts it into the kitchen, OK? You've all seen SESI, right? Did you take a tour of SESI? SESI has three of the world's largest commercially available heat pumps. And they are used, as you will have understood, to heat and cool the campus. This is the annual heating and cooling load of this campus, as now taken care of by SESI. And over the course of the year, the cool that we require for air conditioning is equal to the heat that we require for heating, more in the winter than the summer. And what those heat pumps do is they recycle those kilojoules from the chilled water line to the heat, the hot water line, and circulate them through the campus. This time of the year in the summer, we have too much heat reduced in the buildings, and therefore we run the cooling towers that you see there in the bright blue. And in the winter time, we have too little heat and we run gas burners to actually produce what's shown in the bright red. Phase two of SESI is going to make use of geothermal heat pump, or geothermal ground source, instead of the cooling towers, and that will obviate both the bright blue and the dark blue. So we're going to cool the circulating water on the heat pumps using the water beneath the campus. So overall, looking at the geothermal picture of the planet, in terms of both electricity and direct use, we actually avoid the consumption of about three days of oil and gas, and the CO2 which is associated with it. It's not a massive amount, however, three days out of 365 is a very useful amount and it's expanding. In many places of the world, Iceland is one, but there are others as well, geothermal is the lowest cost electricity. Solar is really cheap in California, but the sun doesn't shine so much in Iceland, and therefore that is their most attractive energy source. Now let's talk about Stanford. So we have a research group here which has existed for more than 40 years already, but our focus is on understanding the subsurface and how fluids move through it. So the place that we're at today worldwide in geothermal energy is we have captured the most attractive resources, the ones which were easiest to find and the easiest to produce, and the future is producing and exploiting or deploying the implementation of power plants and direct use applications in harder to find, lower temperature, lower quality resources. And therefore, our focus is on fractured media, how we pass water through fractured rocks, and that is us. So let me conclude with that and invite your questions. Thank you. That was at the World Geothermal Congress in 2015. Does that mean that all of the subsidies and tax credits or whatever that comes with that doesn't apply to that as well? Correct. So it's not just California actually, it's nationwide. In fact, many countries have a similar path. And the principal reason why it was in the 1970s when there was a big push for renewable energy expansion, there were rebates and feed-in tariffs and whatever applied to renewable energy. And all of the people who had massive hydro plants said, oh yes, give us some of that. And the government said, no, we're not classifying you as renewable, it only counts for other kinds of renewable. So physics, we all understand that physics is renewable. It rains and then it rains again. But legislatively, it's not classified that way. Yes, I think so too. Are there any downsides to geothermal or limitations? What's sort of the maximal that we could take? Is there any physical limitation? Could we cool the earth too much? It seems unlikely. Cooling the earth? No, we don't need to worry about that. We can actually, the amount of energy that it would take to cool the earth by one degree could supply us energy for the next 100,000 years. So we don't have to worry about cooling the earth. What we do have to worry about is seismicity. So as you move large bodies of water around in the subsurface or any kind of fluid, actually, you can produce earthquakes. And that's true of even taking groundwater out of the ground, you can produce earthquakes, but it's certainly true of oil and gas, it's true of geothermal as well. Most of them are not detectable. You wouldn't feel them, but some of them you do. And the big hurdle, the sort of public relations hurdle in geothermal is in due seismicity. And there was a famous project in Basel, Switzerland, where they were drilling geothermal well in the center of the city. And they were fracturing it, they're producing fractures to enhance the permeability as in the manner that I explained as our research focus. And they produced a 3.5 earthquake. Now, 3.5 earthquake in California, we would sort of shrug, we would hardly even feel it. But they're not used to 3.5 magnitude earthquakes in Basel, Switzerland. And they have a lot of old masonry buildings that are historical and important to them. And they were damaged, some of them. And they were seriously upset about it. That the manager of the project almost went to prison, but not quite. More recently, in Korea, they also have an enhanced geothermal project, which in 2018 produced a 6.5 magnitude earthquake, which you certainly can feel and produce a very large amount of damage. So in the focus of our research, is to actually not to gloss over those issues, but to try and understand and ameliorate them. How can we develop and stimulate geothermal reservoirs without producing significant induced seismicity? And certainly that is, we have many examples of geothermal reservoirs which have modest or even zero seismicity or undetectable seismicity. How do we have those instead of the ones that upset people? I believe using geothermal energy can cause sulfur deposits somewhere, is it true? Sulfur deposits? Yeah, before you use it to create electricity using the turbine, you have to remove sulfur, is that correct? Yes, so hydrogen sulfide, so in the subsurface, the water is at high temperature, so therefore it dissolves minerals quite easily, including gases, most importantly CO2, but also hydrogen sulfide as well. So hydrogen sulfide has to be removed for certain kinds of geothermal plants, including those most commonly used in California, which are steam flash cycle plants where the steam goes through the turbine and is condensed on the other side. So after you condense steam to water, what's left is the hydrogen sulfide, which goes out through the cooling tower. It's not allowed to be emitted in the state of California, so it has to be captured and it's then used for fertilizers and other things. In Nevada, they don't have that problem because they have closed-loop power plants in which the water never goes outside of a pipe. It transfers its heat to a secondary working cycle using pentane or something like that and the water never leaves the pipe, the CO2 and the hydrogen sulfide don't leave the pipe either and separation is not an issue. Thank you. For your research, have you also looked into like a geothermal and small scale in the sense of taking that and integrating that with microgrids, for example? We have not, but others have. One of the characteristics of a geothermal development is that they are typically utility-scale developments, not exclusively, but largely so. There are some examples coming into play now of so-called micro-binary plants. So these are plants which are 200 kilowatts, something like that, which will supply a factory or a hotel or something like that. They're not grid-connected, but they're disconnected specifically so. So that's sort of a new development, not widely deployed, but coming into play. So that, for example, in Alaska, they're seriously interested in that because they have a lot of isolated communities which are not on the grid. There are several small-scale binary plants in Alaska. They're interested in places like the Caribbean. Hawaii has some useful, they have utility-scale plants, but island grids are good examples in which geothermal is useful. One of the downsides of what's necessary to make that possible is to be able to dispatch the power because, as I mentioned, geothermal wells specifically don't like to be switched on and off, and it's hard to throttle back and open up a plant. That makes them challenging, not impossible, but challenging to actually deploy in a grid. If you have an island nation that needs one megawatt at 6 p.m., but only needs 300 kilowatts at 9 a.m., then having a single geothermal plant to meet that need is quite challenging. I'm done. All right, well, thank you very much.