So far, we've reviewed the most talked about renewable energy sources, hydro, wind, solar, and biomass. Now we'll look at geothermal or renewable low emissions energy source that gets relatively little attention, but which has immense promise for the future. Geothermal energy is naturally occurring heat from the Earth. We know that as we drill or tunnel below the Earth's surface, the rocks get hotter. At the center of the Earth, about 6,500 kilometers down, the temperature reaches 6,000 degrees Celsius, comparable to the surface temperature of the sun. The rate of temperature increase as we go deeper is called the geothermal gradient, which in most places is about one degree Celsius for every 20 to 50 meters of depth or 20 to 50 degrees for every kilometer of depth. Where the geothermal gradient is higher and harder rocks occur close to the surface, molten rock or superheated steam can make their way to the surface to create volcanoes like this volcano in Iceland or geysers like Old Faithful in Yellowstone National Park, Wyoming. Humanity has harnessed the power of geothermal energy for thousands of years. Hot springs where geothermally heated water escapes to the surface were centers of settlement in places such as Japan and Italy. They are still tourist attractions in many parts of the world, as we see here at one of the many remote hot springs in Western Canada. In the early 1800s, people started harnessing geothermal heat to generate electricity, and the first commercial geothermal power plant was constructed in Italy in 1913. Today, because geothermal is a low-emissions renewable energy resource, we use it in a variety of ways and there are exciting innovations taking place to make it even more useful. Back to the old reliable Sankey diagram, where we see the geothermal today is a relatively small energy source that goes primarily towards production of electricity. But the diagram does not reflect geothermal contributions to buildings in the form of space and water heating. As it shows, geothermal energy producing electricity only. In fact, more than three times as much geothermal energy is used for heating directly as is used to generate electricity. Let's dig into that a bit more. There are increasing numbers of applications where geothermal can supply heat directly, replacing fossil fuels or other sources in high, medium, and low-temperature applications. Let's look first at electrical generation and then at direct heat applications, where hot reservoir rocks contain water and the water is hot enough, generally hotter than 120 degrees Celsius, they can be used to spin turbines generating electricity. A well is drilled to bring super-heated water or steam to the surface where it passes through the generation system. Once cooled, the water is returned through an injection well to the subsurface at a distance far enough from the intake to avoid cooling the input stream. In addition to hot enough temperatures, the geothermal reservoir must have sufficient permeability to allow fluids to flow efficiently through it, much like an oil or gas reservoir. As you can see from this photo of a geothermal generation plant, a lot of steam is vented, but it's just water vapor. Water vapor is actually a greenhouse gas, but human activities are far too small to change the atmospheric balance of water vapor, lower temperature, geothermal waters as low as 80 degrees Celsius can produce electricity, and a binary cycle plant, where the hot water heats a fluid with a lower boiling point than water, thus generating vapor that can drive the turbines. The United States is the world leader for geothermally generated electricity, much of a concentrated in California and adjacent western states where geothermal gradients are high. Geothermal electricity generation capacity is growing slowly but steadily at two to three percent per year over the last 20 years. Much faster growth is envisioned in the IAEA sustainable growth scenario to reduce future fossil fuel demand. Direct use geothermal, tapping into relatively shallow, low to medium temperature geothermal energy is expanding rapidly. The amount of heat supplied depends on both the temperature of the geothermal fluid and the rate at which it can be produced. In this example from the US Department of Energy, we see the Capitol Mall geothermal district heating system in Boise, Idaho. Hot water is drawn from 400-800 meters below ground into a pump station where it is distributed through our buildings in the State Capitol District. At the other end of the distribution system, cooled water is reinjected into his own 500-650 meters deep. Direct use geothermal reservoirs can be cooler, but still must have sufficient permeability to allow the hot fluids to be produced quickly enough to meet heating demands. Shallow geo-exchange systems, also called ground source heat pumps, are used for heating in the winter and cooling in the summer. They're not true geothermal systems as they do not derive heat energy from the earth, instead, they are heat storage systems. Here's why. In an open-loop system, groundwater is circulated between the building and wells in the ground. A closed loop system is similar, only fluid, either water or antifreeze, circulates within a contained pipe network exchanging heat both underground and within the building. The open-loop system depends on there being good permeability in the rocks underground to allow rapid fluid flow. The close loop system doesn't need this as all the fluid flows within the closed pipe. So bedrock characteristics are critical in choosy between these systems, the constant temperature below the surface is sufficient to heat household air in the winter and cool household air in the summer. Supplemental heating and cooling using more traditional energy sources may be needed plus energy to pump the fluids. Geothermal heat energy is used for more than heating buildings. It can heat greenhouses and even agricultural ponds. Many agricultural products need to be dried and geothermal heat can be alternative to burning fossil fuels. Geothermally heated bathing and swimming facilities are popular tourist attractions and there are various industrial uses as well. Comparing geothermal direct use in 2022 to 1995, we see tremendous growth. The smaller dashed half circles represent direct use geothermal energy in 199 and the much larger half circles are the direct use in 2020. Heat pumps have really taken off with a compound annual growth rate at a phenomenal 16 percent. Remember that heat pumps are energy storage systems, not true geothermal energy supply. Direct use geothermal is used around the globe with China leading the way by far. Although Canada is not well endowed with geothermal resources, it does register on the chart at 1.42 percent because of significant direct use heat applications. Let's talk about the positive attributes or benefits of using geothermal energy. Geothermal energy is a renewable resource that emits very little carbon dioxide and other greenhouse gases after facility construction. Life cycle emissions, the quantity of GHGs emitted for each unit of electricity provided are very low compared to gas, oil, and coal. A geothermal electricity facility can supply its own energy to maintain systems and run pumps. A geothermal heat facility may require electricity or fuels from outside sources, which may increase its GHG footprint. Geothermal is constantly and predictably available unlike wind and solar, which are intermittent. The energy is there all the time. So we can consider it to be reliable baseload power, both in terms of electricity production and indirect heat applications. In fact, the capacity factor or proportion of time it's producing electricity is matched only by nuclear power generation facilities. On top of that, geothermal power generation can be scaled up and down quite quickly. It's dispatchable, making it ideal to maintain constant supply and electrical systems where demand changes or other power sources vary. Once a geothermal facility is built, costs are limited and predictable. The facilities are relatively simple and outside fuel sources are needed only for limited applications, such as running pumps unless they run off electricity generated at the facility. The thermal energy available underground is enormous and can sustain a geothermal facility for decades. These are excellent qualities, but there are some downsides which have limited geothermals contribution to world energy supply to date. This map shows heat flow from the Earth's interior to the surface. It demonstrates that many places where the hottest rocks are closest to the surface are located deep in the ocean along the mid-oceanic ridges. Places where there are lots of volcanoes like Iceland, Western North America, Southern Europe, Japan, and Indonesia may have excellent geothermal resources. Most other land areas are cooler and thus have less geothermal potential. There are other factors involved, such as thermal conductivity of the rock, but this is a good regional view. Similar to some other energy sources we've looked at in the course, such as wind, solar, and hydro, geography plays a part in geothermal availability. We can generate a lot of geothermal electricity only where the resource potential is very good. Remember that in addition to high geothermal heat flow, we need rocks with good permeability so the geothermal fluids can flow quickly to the surface. In this geothermal potential map for Canada, we see the combination of high heat and substantial permeability in the hotter colored areas, mostly in Western Canada. The gray area, the Canadian Shield, consists of very old rocks that are impermeable and contain little water. They can float to the surface even if heated sufficiently. EGS or enhanced geothermal systems are being piloted in hot, impermeable rocks. Hydro sharing, comparable to the hydraulic fracturing used in the oil and gas industry, can enhance natural fractures and hot rocks at depth to create permeability and thereby high rates of fluid flow. This can allow expanded geothermal heat production in areas where the rocks lack the natural permeability to produce fluids at high rates. Because operators must move very large volumes of hot fluids to extract sufficient energy from geothermal wellbore, the wellbore diameter must be very large and many wells are very deep. We use geoscience skills and data to locate our geothermal wells, but there's always some risk that will drill a well into an inadequate geothermal reservoir. This exploration risk is like that in minerals and petroleum exploration and can add substantially to costs. A geothermal well can be drilled to more than 3,000 meters deep and may cost around five million dollars to drill and test. A project to produce 20 megawatts of electricity enough to power up to 20,000 homes per year can cost more than $150 million for the producing wells, re-injection wells, electrical plant, and tie into the grid. These costs vary depending on location, but we're talking significant dollars to bring a significant geothermal project online. We sometimes hear that depleted oil and gas wells can be repurposed for geothermal production. Unfortunately, there are engineering and liability issues that make most old oil and gas wells unsuitable for geothermal. However, they can provide data to help us choose sites for new geothermal drilling. Upfront costs may be higher for geothermal than for many other renewable energy sources. But remember, once it's on stream, there are a few additional costs. No fuel is required to run pumps and a constant power output need and electrical storage is not required, a huge advantage over intermittent renewables. Long-term water injection and withdrawal modifies the subsurface, and if these changes occur near existing faults, they can induce movement or slippage on the faults, creating a seismic tremor or earthquake. Water injection at a geothermal power plant in the Pohang, South Korea induced a magnitude 5.4 earthquake in November 2017, causing widespread damage. This quake is regarded as the largest induced seismicity event associated with human activities, larger than any thus far recorded with hydraulic fracturing or water disposal for the oil and gas industry. A lot of research and development is happening to reduce costs and to make geothermal available in more areas of the world by making it economic to top into lower-quality heat resources. Eavor Technologies is one of the exciting new players in the geothermal industry. We're joined now by Jeanine Vany, Executive Vice President of Geosciences at Eavor Technologies Inc, to tell us about Eavor's closed-loop geothermal technology. Hi. It's a pleasure to be a part of this massive open online course that is tackling the enormous energy transition challenge. Geothermal energy development is not new, it's been around since the early 1800s in very specific settings. It has not scaled however, and currently delivers less than 0.2 percent of the total primary energy supply. Why is geothermal experiencing revival? The obvious reason is in the title of this course. New policies, tax regimes, and financial instruments are spurring technological development, field scale trials, and ultimately enabling commercial deployment. My name is Jeanine Vany, I'm a professional geoscientist in Alberta and the Executive VP of Geosciences at Eavor Technologies Inc., a closed-loop geothermal startup based here in Calgary, Alberta. I'm here today to speak to you about our new technology called the Eavor-Loop, which has the potential to take geothermal from niche to anywhere by re-purposing many off-the-shelf technologies from the oil and gas industry. Our goal is to drill a giant radiator deep within the Earth by using multi-lateral wells and connecting them at depth to form a loop that can supply heat or power. One installation can heat 1,000 homes. The Eavor-Loop Prototype Project consists of two wells drilled 2,400 meters deep and about 2,000 meters apart. Cool water goes down one well is heated as it passes through the hot rock at depth, and is produced as hot water up the other wellbore. Thermal energy is extracted at surface and the cooled water flows back to the injecting wellbore in a giant closed-loop much like the closed-loop shallow heat pump applications we saw earlier. Closed-loop technology differs from conventional geothermal in several keyways. Firstly, conventional geothermal relies on water flowing through a reservoir. So there's fluid exchange between the wells and reservoir. In Eavor's closed-loop system, water is circulated in a network of pipes that are sealed from the reservoir. This means no fluid flow into or out of the rock, and therefore, no need for permeable rocks. Conventional geothermal projects often use electric submersible pumps to pump the water out of producing wells. These pumps use electricity, sometimes up to 40 percent of the power generated. Meaning that net power delivered can be as little as 60 percent of the gross power generated. The closed-loop system runs off a thermal siphon or natural heat convection so there's no pumping required and all of the electricity generated is delivered to the grid. Open geothermal systems require ongoing water treatment to keep fluids within operating specifications. Closed loop systems have no water treatment because the water is contained in the loop for the lifetime of a project. Due to the different system design of conventional versus closed loop, the number of wells required and the capital outlay very significantly. While closed loop systems have very low operating expenses, there are significant upfront capital cost to drill the multi-lateral wells. Closed loop geothermal requires relatively little exploration for appropriate reservoir conditions. If one Eavor-Loop is successful, more can be deployed readily. Finally, the Eavor-Loop produces dispatchable electricity. I'll expand upon that shortly. Looking at some of the challenges we noted earlier for conventional geothermal, the Eavor-Loop presents some other notable differences. There is no risk of induced seismicity by fluid injection and withdrawal because no fluids escape from the close loop. Eavors' efficiencies allow access to cooler geothermal regimes. But capital cost for drilling the specialized wells and installing facilities are still the challenge. Here we see Eavor's technology development pathway. On the far left is the successful Eavor-Lite prototype, which we saw a few slides back. It has been operating for two years using off the shelf technology and oil and gas mapping methodologies. Next to the right is Eavor-Loop 1.0, which will be drilled in Germany in 2022. It uses all the same technology, but reduces the surface footprint by drilling off a single drill pad. Eavor-Loop 2.0, on the far-right unlocks hotter temperatures and produces better economic value. Magnetic ranging technology adapted from the oil and gas service sector allows Eavor to drill multiple well-bores to complete their subsurface Eavor-Loops. Let's watch the video. To construct an Eavor-Loop, two similar rigs are positioned to drill from a common location. The vertical wells for the Eavor-Loop are drilled in parallel approximately 50 meters apart. Once the vertical section is drilled, we place casing in the well down to the top of the granite layer. The bottom hole assembly or BHA from both rigs now initiates drilling of the production sections into the granite basement simultaneously. Drilling from both rigs extends down to the planned intersection point. 50-100 meters separate the two BHAs to ensure optimal thermal outputs. The lower of the two wells will extend beyond intersection point while the upper well is position at the kickoff point. The upper well is then drilled bidirectionally towards the lower well-bore by following magnetic ranging signals emitted by the upper BHA. The signal is interpreted by a specialized receiver in the lower wellbore BHA. Once within the range of a couple of meters apart, the lower well BHA is moved back out of the way and the intersection is completed. The process is then repeated for subsequent multilateral-s of the Eavor-Loop. Energy forever. Transient operation of the Eavor-Loop provides different shaped outputs to meet end-user requirements. For example, in systems with abundant solar power resources, Eavor-Loop can ramp down flow rates and store heat in the system at midday when solar is peaking. When the sun goes down and people are coming home from work, turning on their dishwashers and washing machines, the system can ramp up using the stored heat energy to deliver more electricity. This is demonstrated in the graph at top-left, showing solar output through the day in yellow and load following output from the Eavor-Loop system in orange tailored to meet system demand. Close-up geothermal thus is complimentary to jurisdictions with heavy solar penetration, such as California, Nevada, and Chile. It functions essentially like a battery, improving grid stability as solar output varies. On the right, we compare Eavor-Loop to lithium ion batteries, showing Eavor-Loop to be superior in terms of storage duration and operational life. Capacity of the geothermal battery does not degrade over time, unlike electrochemical batteries. When Eavor-Loop is operating at 100 percent capacity to meet power demands, it can generate 35 times more power output than solar and 300 times more than wind for the same land area. This is a big advantage as the large surface footprint of the wind and solar can cause many issues with landowners and communities. Similar surface footprint advantages are achieved by conventional geothermal systems as well. Geothermal has an important role to play in the more diverse energy systems of the future, and technological innovations will further improve its applications. We've got one more set of energy resources to look at in the next lesson. Wave and tidal energy.
