Geothermal Power

There are vast amounts of heat in the Earth, adequate to supply a multiple of the total energy needs of the world. As with solar energy and other alternative energy forms, the challenge is to effectively capture the vast amount of energy available in the Earth.

Hot water from the Earth has been used for thousands of years for heating buildings. Boiling water from the ground has produced electricity for over a century. The basic technology is straight-forward, if the conditions are right.

Until now, harnessing geothermal energy has been practical only in select areas, where geological conditions have brought high temperatures close to the surface. In the most favorable areas, geothermal can be directly competitive with traditional energy sources. In areas with difficult conditions, subsidies or other incentives are needed to make geothermal economically viable.

Emerging technologies hold the promise of greatly expanding the areas where geothermal electric power is viable. Other technologies are also expanding the scope of geothermal heating. It is certainly worth the effort to develop and implement these new technologies. Geothermal power is clean, reliable and environmentally friendly. It is perhaps the only alternative energy form that can operate throughout the year on a consistent basis around the clock. Once installed, the operating costs are modest, much less than carbon-based fuels. If techniques for capturing this energy can be improved, then there is potential for a large portion of the world’s energy resources to be met from geothermal sources.

Geothermal Energy Supply is Nearly Limitless

Practically limitless amounts of energy are available from the heat of the earth. The core is extremely hot: 5000 degrees Celsius. Massive amounts of heat from deep in the core flow out through the crust to be lost to space. Some of that heat is a carryover from the very origin of the planet. The heat being given off by the gradual cooling of molten rocks is augmented by natural radioactive decay. In essence, the core of the earth is a massive, low-grade nuclear reactor.

The nuclear heat nearly offsets the natural heat loss, so that the earth is cooling slowly over billions of years. It has been estimated that the heat being lost to space would be enough to provide a multiple of the total energy needs of humanity. The challenge is that the heat available on average over the crust is small - insufficient to make it economically feasible to capture and use the heat, except in a few areas.

On average, the temperature increases 25° Celsius for each kilometer of depth. On that basis, one would have to drill holes eight kilometers deep to obtain a temperature at the lower end of the range suitable for generating electricity in a conventional steam turbine.

Holes to that enormous depth are possible, but prohibitively expensive, making geothermal power impractical in most locations. In some locations, molten rock, or magma, from deep in the earth has risen through faults or cracks in the crust. In areas where the magma comes close to the surface, high temperatures can be obtained with relatively shallow drill holes. On that basis, capturing geothermal power becomes a practical reality.

Heat free for the taking

For thousands of years, naturally occurring hot springs have provided heat for humanity. The ancient Romans located some of their cities near places with geothermal activity in order to take advantage of the hot springs. For example, in Bath, England, a popular tourist attraction is The Roman Baths, one of the most elaborate bath houses ever constructed; it has enjoyed a supply of hot water for nearly 2000 years. The Romans also ingeniously channeled hot water to heat buildings.

Today, many places continue to utilize the heat from hot water flowing at or just beneath the surface. In Reykjavik, Iceland, hot water is piped from geothermal plants and used to melt snow and ice from city streets. In many other places, shallow drill holes can capture hot water from below the surface for heating buildings, greenhouses and aquaculture facilities.

Capturing hot water at or near the surface effectively provides free heating. When the hot water is near surface, the capital cost is modest, so that the economics of such systems is extremely favorable. However, there are only a very few places in the world where conditions are right to capture direct heat in that way.

Ground Source Heat Pumps

A far more broadly available option is the use of heat pumps to capture heat from the ground. Heat pumps can be used where the ground has not been geothermally heated. Even though these systems are frequently referred to as geothermal, strictly speaking they are not.

The temperature of the ground below a few meters is the same as the average ambient air temperature over the year in that location. These systems work off the ambient ground temperature. Even though the temperature of the ground may be cooler than the temperature inside a building, the heat that is in the ground can be utilized to heat the building.

A heat pump is basically the same as an air conditioner. A separate article explains the process in more detail. For now, just think of the principle of an air conditioner which takes heat from inside a room and transfers that heat to the outside. Ground heat pumps act like air conditioning systems to pump heat out of, or back into, the ground.

Heat pumps require motors to run compressors, and therefore use energy. The energy use is typically about a third less than a conventional gas furnace. A million or so of these systems are presently in use, with a production capacity equivalent to about 12 gigawatts.

The cost of installation is typically two to five times the cost of a conventional heating system. These systems are most cost effective if installed at the time of construction as the ground piping must be buried. They are also more effective on larger scales, for example for an apartment building as compared to a single house.

By saving about a third of the energy bill compared to conventional heating and cooling systems, the extra capital cost can be repaid in two to thirteen years.

Electricity from the Ground

For a century, boiling water from deep in the ground has been used to make electricity. That boiling water beneath the surface is tapped by drill holes. The steam is directed through turbines that drive generators to make electricity. The turbines and generators are identical to those used on gas or coal-fired plants. The only difference is that instead of a boiler, the steam comes from underground.

When magma rises to within a few kilometres of the surface, the rocks above become very hot. Water percolating through the hot rocks becomes super-heated, up to several hundred degrees. The immense pressure at one or two kilometers of depth keeps the water in liquid form, even though it would boil at surface.

Holes are drilled into these areas of superheated water and the holes are cased with steel tubing up to the surface. Once the superheated water flows up the pipes, it enters a flash chamber, where at lower pressure the water boils. (Thinking back to high-school physics: water expands by 1,700 times going from liquid to gas, or “steam” at atmospheric pressure.) The steam drives the turbines and generators, which are essentially identical to conventional steam turbine generators. Once the heat has been extracted, and it condenses back to liquid, the water is re-injected into the geothermal field in what is effectively a closed loop.

There are a number of variations to geothermal power generation, and these are explained in more detail in a separate article.

Once a geothermal power system is in place, the operating cost is modest, typically much less than the cost of operating a coal or gas-fired plant. One of the larger costs is in periodically cleaning the pipes due to the dissolved minerals in the geothermal water. Wells typically last for many decades before the temperature falls enough to lessen effectiveness. The Larderello field in Italy is still operating a century after it first began producing electricity.

Another important benefit of geothermal electricity is that it has a very high level of operating time. Typically, the plants operate nearly consistently at design capacity, going offline only for routine maintenance. The capacity factor (that is, the ratio of power production to design capacity) is in the order of 90 to 95%. At that rate, geothermal is comparable to the highest of any form of electricity production, which is nuclear, and better than coal. Geothermal availability is double the level of any other form of renewable energy.

Energy that is Free but Expensive

One would think that having free steam for a few decades would provide an overwhelming cost benefit to a geothermal system.

Once the plants are in operation, they are indeed highly profitable. In the same way that free sunlight is generally too expensive to use, the high up-front capital cost of a geothermal system makes it challenging to harness all that free energy.

Turning the steam to electricity uses standard equipment: the turbines and generators are basically the same as those used in a gas-fired power plant. However, in a gas plant, a simple boiler and a hook-up to a gas line is all that is needed to provide power to the plant. Harnessing energy from the ground is much more complex than installing a gas or coal boiler. In fact, geothermal plants require considerable expense to tap into the hot water beneath the surface.

First, the plant must be located near an area of high heat close to the surface. Places with suitable geological conditions are limited, and are not often close to where power is needed. Power lines to tie a remote area to the grid can add a big cost to a power system.

Finding hot rocks is only the first step. Power can only be produced effectively if those hot rocks have a high permeability. That is, large volumes of hot water must be able to flow through the rocks and into the production wells. There are many situations where there is an enormous amount of heat within reach of drill holes, but the rock formation is too “tight” or impermeable to allow adequate water flows.

Low permeability can be offset by increasing the number of drill holes. The challenge is that the large diameter holes (around 30 centimetres or 12 inches) are very expensive when drilled to one or two kilometers. The drilling cost is further increased by the elaborate protection that is necessary to guard against hot water blow-outs. Superheated water out of control could be deadly to the drilling crews.

A modest-sized plant may require 20 to 40 holes, each costing several million dollars. In spite of the best planning, not all of the holes will be economically viable. Some will fail to achieve a high enough temperature or sufficient flow rates, even though they may penetrate the hot zone for hundreds of meters. In addition to the recovery wells, there must be re-injection wells.

The cost of drilling the holes can equate to a large portion of the total cost of a conventional power plant. There is a great deal of sophisticated science involved in the siting of the recovery wells. The evaluation process involves some of the same techniques used in mineral and/or oil exploration. For example, geophysical techniques are used to identify areas with hydrothermal alteration within the hot zone. Where the alteration is most intense implies areas with the greatest water flow.

Slim holes are drilled first to get an initial indication of temperatures and flow rates. Where results are favourable, productionsized wells are drilled and tested. After a few such holes are completed, and temperatures and flow rates are projected for the balance of the holes needed for a commercial application. Those results are factored into a comprehensive analysis that will estimate the number of holes required for a target production rate. Those figures are then worked into a feasibility study that projects the capital and operating costs and the revenues in order to determine if the facility is economically feasible.

As in oil or mineral exploration, a company may spend millions or even tens of millions of dollars to evaluate a site before concluding that the site is not economically viable. Even the most favourable geothermal sites will cost much more to develop than a coal or gas-fired plant. The trade-off comes with the saving in fuel costs over time. In many cases, it is a difficult decision.

Often, subsidies or other incentives are needed to help offset the capital cost, and higher tariffs are needed to swing the economics in favour of the geothermal plant.

Expertise Required

The commercial success of a geothermal project depends on having a favorable development site and then developing that site in the most effective manner. Over the past few years, the growing popularity of geothermal has seen many of the best sites locked up by smaller companies. The situation is very similar to oil or mineral exploration, where small companies are the first movers and secure the most favourable development sites.

Geological conditions will determine the strategy with regard to drilling the production wells: hole diameter, depth, spacing, and other variables will be determined based on the unique circumstances of each location.

Finding the right site and developing the site through drilling production wells is only the first step. There are various approaches to harnessing the hot water from the ground, although at this time, all of the approaches involve the use of steam to drive turbines.

The design of the power plant will depend on the temperature and the flow rates. In a conventional power system, the boiler is adapted to meet the needs of the turbines. With geothermal, the design of the turbines must be selected and fine-tuned to optimize the nature of the energy source.

In view of the large number of variables that must be taken into account, a great deal of expertise is required to optimize the returns in a geothermal system.

At this time, government and public support for renewable energy has resulted in a variety of financial incentives to stimulate development of geothermal systems. A great many systems will be developed on the basis of simply applying today’s technology with subsidies used to make up any shortfall of revenue and achieve a return on capital.

The companies that will prosper in the longer term are those that can go beyond the present technology to achieve superior returns. That is, if a company can lock in a tariff on the basis of today’s subsidized rates and then better the economics through the most effective use of today’s technology and the use of emerging technologies, that company can achieve a superior rate of return. The companies that rise to the top in terms of technological expertise will quickly emerge as industry leaders.

Evolving Technology is Expanding Geothermal’s Potential

There have been big advances in geothermal technology over the past few years, with further potential for big increases in efficiencies and reductions in capital costs. One challenge being overcome with new technology is tight rock formations.

That is, in some locations the rock is at a high temperature, but there is too little permeability for adequate volumes of water to flow into the wells. Work is being done to adapt oil field fracturing techniques to geothermal reservoirs. In essence, permeability is created by fracturing the rock, generating minute cracks that the water can flow through to get into the recovery wells.

While the concept of fracturing is similar to oil or gas wells, there are important differences. For example, in oil wells, the producing formation may be only a few meters or a few tens of meters thick. In a geothermal well, the potential production zone could be a hundred meters or more, meaning there is a great deal more rock to fracture. Oil wells are uniformly in sedimentary rock, which is softer than the crystalline rocks that often host geothermal reservoirs.

Another important area for enhancement has been the emergence of technologies that allow efficient power production from lower temperature sources.

For example, there are many locations that could produce water at, say, 150 degrees centigrade. That temperature is below the level needed for basic geothermal, which typically exploits water temperatures of 180 to 350oC. The high temperatures are needed to obtain enough force in the conversion to steam to drive the turbines.

There are only a limited number of areas with the temperatures at the high end of the geothermal range, but a great deal more zones where lower temperatures are available near to the surface. With emerging technologies, the lower temperature sources are beginning to be exploited.

The use of binary-cycle systems, which are described in a separate article in this issue, makes it possible to exploit heat sources with a temperature lower than required for normal geothermal systems.

It is possible to exploit sources with temperatures lower than the boiling point of water. For example, a remote Alaskan resort has hot water near the surface at 73.8 degrees Celsius (165 degrees Fahrenheit). That water, which is below the boiling point, is used to boil another fluid that has a lower boiling point. The “steam” from the secondary fluid powers a turbine which drives a generator.

Engineers can select from fluids with a wide range of boiling points to match the system to the water temperature available from the geothermal source.

At this time, these enhanced technologies are technically feasible, but for the most part cannot yet compete with conventional energy sources on a purely economic basis. Over time, further enhancements to the technologies will reduce costs and improve efficiencies. Furthermore, manufacturing costs will fall as more systems are implemented and manufacturing volumes increase. In the meantime, incentives are available that can make the newer technologies viable.

Government Policy Supports Geothermal

Government policy, driven by public opinion, has swung solidly in favour of programs to reduce the burning of carbon fuels. In areas with high geothermal potential, that source of energy is at the top of the list for policy-makers.

The United States has exceptional geothermal potential, and is presently the world’s leading producer of electricity from geothermal sources. It is not surprising that American policy has shifted firmly behind geothermal energy as a way to wean the country off oil. At the end of May, President Obama announced over $467 million in funding for solar and geothermal energy projects. Seventy-five percent of this funding, or $350 million, will be invested in geothermal technologies. These funds will go towards geothermal demonstration projects ($140m), enhanced geothermal systems research and development ($80m), innovative exploration techniques ($100m), and a geothermal data system ($30m).

This funding, as well as other incentives such as tax credits, will give geothermal a huge boost and see development of geothermal projects in the United States take off. As of March 2009, there were 103 new geothermal projects under construction.

Karl Gawell, Executive Director of the Geothermal Energy Association, said, "There are more geothermal power projects under development today than have been built in the history of the United States. This stimulus funding will help make sure those projects are successfully completed and will help develop the technology needed to bring tens of thousands of additional megawatts on line.”

Many states in the United States, and jurisdictions in other countries, have mandated that a certain minimum percentage of electricity sold in the jurisdiction must come from renewable sources, with that percentage growing over the next few years.

The utilities in those jurisdictions are therefore on the hunt for renewable sources, and will pay the higher prices needed to meet the mandates. The added cost of the renewable power gets rolled into the overall average prices charged by the utilities.

Europe is making big advances in the geothermal sector; in 2004, the European Renewable Energy Council announced that by 2020, 20% of their energy will come from renewable sources. The top geothermal energy producers include Italy with 810 megawatts and Iceland with 420 megawatts of energy production. Italy has plans to double its geothermal production by 2020.

Iceland has utilized geothermal energy very successfully. The country’s entire heating and electricity needs are generated by renewable energy, with 87% of its heating and 17% of its electricity coming from geothermal sources. The country produces 220MW of electricity from geothermal power and imports fuel only for transportation needs.

Geothermal Usage is Increasing Dramatically

According to the Geothermal Energy Association and the International Geothermal Association, geothermal electricity is generated in two dozen countries around the world - this number is expected to almost double by 2010. When direct energy usage is included, 70 countries use geothermal energy today. The world produces about 10,000 megawatts of power from geothermal power plants, which is enough to meet the needs of 60 million people. This figure is expected to reach 11,000 megawatts by 2010.

The United States is by far the world’s leader in geothermal production, with nearly 30 percent of the world’s total. The country produces 3,000 mega watts of geothermal electricity. The United States also has about 1 million heat pumps that supply the equivalent of 3,700 mega watts of heat to buildings and homes. California is responsible for the largest portion of geothermal production in the United States. Those may sound like big numbers, but geothermal still represents a fraction of a percent of the total energy needs.

Geothermal energy use has been growing substantially in the U.S. and in August 2008 there were 4,000 mega watts of geothermal power plant capacity under development at 103 projects in the country. With the Obama initiatives in place as of a May 2009, these development projects could be pushed forward into production at record speeds and additional earlier stage projects could be advanced towards development.

The National Renewable Energy Laboratory estimates that based on the already discovered geothermal resources available in the United States there is potential to reach 26,000 megawatts of electricity generation by 2015, with an additional 20,000 megawatts of energy from heat pumps if technologies and funding permit.

Overview of the Geothermal Industry

There are only a handful of companies that operate exclusively in the geothermal space. Several of the large utilities operate some geothermal plants along with a variation of other types of plants such as coal or natural gas.

There are a large number of small companies that hold the development rights to geothermal sites. In a situation similar to the resource industry, those small companies are the first movers, and obtain the development rights. Often, they will carry out early stage exploration of the site, perhaps drilling the slim holes to get a first look at temperatures and flow rates.

Many of the small companies may plan to raise development funds and take their projects to production. However, reality may get in the way. Few of those small companies have the expertise needed to properly evaluate the potential of the sites, let alone convince investors that they can successfully develop the sites and produce enough electricity to generate a return on the invested money. As in the resource industry, the small companies that hold development rights will get rolled into larger companies that have the expertise and the financial clout to develop power plants.

Outlook for Geothermal Companies

From a purely economic perspective, and without some form of incentive or other financial support, only the most favourable sites have the potential to generate returns. At present, there are many forms of financial support available for development of geothermal projects. As a result, many sites will be developed.

In the meantime, exploiting the best sites, with whatever subsidies are available, puts companies into a strong position to benefit over time with improving technologies. Over time, with declining development costs and improved efficiencies, combined with the increasing price of traditional energy sources, costs of geothermal power will eventually fall into line with fossil fuels, such as oil and coal.

The geothermal industry is still in its infancy. At this time, there are many small players. Over time, there will be consolidation that will see a few companies emerge as industry leaders. The successful companies will be those that have expertise and the business acumen to quickly and efficiently develop the most favourable sites. The companies that become the leaders will enjoy cost benefits that will put them into strong positions to continue to acquire other companies.

Heat naturally flows from areas of higher temperature to areas of lower temperature. A hot cup of coffee will give up its heat to the air, eventually reaching room temperature. Heat is a tangible thing, while cold is the state of lesser amounts of heat.

A heat pump is a device that moves heat against the natural temperature gradient. A familiar example of a heat pump is the refrigerator. The interior is cold because a heat pump extracts heat from the interior of the refrigerator and pumps it to the outside of the fridge. Exactly the same principle applies in an air conditioner: Heat is pumped from the room to the outside, even though the room is cooler than the outside temperature.

A heat pump in a building operates similarly to a refrigeration system, where heat is absorbed from some source, such as the ground.

Ground source heat pumps extract heat from the ground and pump that heat to the inside of the building. Even though the ground temperature is cooler than the building, the heat pump is able to extract the heat from the ground and move it into the building. The same principle works in reverse: In summer, the same system can pump heat from the house into the ground.

Heat pumps can also extract heat from the air or from water, such as the ocean, or pump heat back into air or water. Ground source heat pumps are generally more effective than air source because the temperature difference is typically less between a building and the ground, than it is to the air.

A typical system utilizes a liquid called a refrigerant that has a boiling point around the ground temperature. An electric motor drives a compressor that pumps the refrigerant in gas phase into a heat exchanger. Under pressure, the refrigerant condenses to a liquid. The compression and the conversion of gas to liquid give off heat to the heat exchanger. The liquid refrigerant then flows to the ground loops. As it moves into a larger volume, it expands and cools, which means it is drawing heat from the ground.

The cycle is constantly repeated: compressing and warming on the building side, and expanding and cooling on the ground side. The net result is that heat is drawn from the ground and released into the building.

This process can be reversed to cool a building. Heat is pumped from the building and released into the ground.

Converting Geothermal Energy to Electricity

So far, the only practical method of converting geothermal energy to electricity is by way of steam pressure that turns a turbine, which powers a generator. There are several variations on that basic theme. The choice of a particular approach depends on the nature of the geothermal source.

1) Flash Power Plants

The most common type of geothermal power plant uses superheated water from deep in the ground, at a temperature from 180oC to 350oC or more. The pressure at depth (typically one or two kilometers) keeps the water in the liquid phase, even though the temperature is well above the level at which it would boil at surface. The water is pumped up steel-cased wells that are in the order of 12 inches or 30 centimeters in diameter.

The superheated water enters a flash tank, where the pressure is lowered enough for the water to boil. The pressure in the flash tank is still much higher than normal atmospheric pressure, as there must be pressure to drive the turbine. For that reason, flash systems require water at a temperature well above the normal boiling point, with a typical minimum temperature of 180oC.

As it boils, the water expands in volume, generating “steam” that drives a turbine as it rushes past. The turbine powers a generator that produces electricity. After condensing back to liquid phase, the water is re-injected into the high temperature reservoir, where it is re-heated by the hot rocks. In some cases, the residual heat is utilized before the water is re-injected. The flash tank is analogous to the boiler in a coal or gas-fired power plant and the turbine and generator are the same as those in the conventional plant.

Flash systems are an effective way to capture geothermal energy. However, they are only useful where large volumes of superheated water can be tapped into at a practical depth.

2) Dry Steam Power Plants

First used in Italy a hundred years ago, dry steam power plants are the oldest forms of geothermal technology. Steam flows directly up the wells from the reservoir. That steam is channeled directly to a turbine, which powers a generator. These systems are simpler with regard to the surface facilities, but are less efficient than flash systems. The reason is that a great deal more energy can be transferred up the wells as water in the liquid phase than as steam. Dry steam is the result of a reservoir that is very close to the surface, or that does not have a sufficient flow of water into it to maintain enough pressure to keep the water in the liquid phase.

3) Binary Power Plant

A binary power plant incorporates recent advances in technology that allow electricity to be generated at temperatures lower than 150oC. This process brings hot water to the surface to heat another liquid (such as isobutane or pentafluoropropane) that has a lower boiling point than water. The secondary liquid is heated in a heat exchanger, with the two liquids kept completely separate. The secondary liquid boils and turns to gas, exactly like steam from water. The “steam” turns a turbine to power a generator and produce electricity. Once the water has caused the secondary liquid to boil, it is pumped back into the reservoir to be reheated by the hot rocks.

The economics of a binary power plant are generally less favorable than for a flash system. First, there is less energy in the water coming up the pipe, as it is at a lower temperature. Secondly, the binary cycle plant requires more capital cost. Nevertheless, binary cycle plants will undoubtedly gain in importance for the simple reason that there is a big demand for geothermal power, and sites suitable for flash plants are not plentiful. Most geothermal reservoirs have temperatures of less than that required for flash power plants, and therefore binary power plants will undoubtedly increase in popularity. The economic disadvantage of these plants will be offset by the growing desire to develop renewable energy.

4) Flash / Binary Combined Cycle

The most efficient method to capture geothermal energy is with a plant that combines flash and binary technologies. After passing through the turbine in a flash plant, the water still has a high temperature. That residual heat can be utilized by passing the hot water through a binary power cycle. A suitable secondary fluid is selected to work with the temperature of the water as it emerges from the turbine.

That secondary fluid is heated to the boiling point through a heat exchanger and drives a second turbine. By capturing the residual heat after the flash cycle, the combined cycle plant is more efficient than a simple flash plant. The tradeoff is that the capital cost is higher. However the economics should favor the additional cost. Another drawback is that the re-injected water is cooler, and may therefore shorten the life of the reservoir. With lives measured in decades, that factor will generally not be a driving force in evaluating the most effective technologies.

There are various technologies that are being developed and enhanced within the geothermal space. The most critical area involves improving the effectiveness of extracting the heat energy from the geothermal reservoir.

One of the leading areas of research is aimed at geothermal reservoirs that do not have adequate water to transfer the heat to the power plant. Enhanced Geothermal Systems (EGS) or Hot Dry Rock Systems are aimed at finding ways to effectively introduce water that can be heated by the hot rocks and drawn to surface. The US administration has recently put aside $80m for funding EGS research and development.

In EGS, water is pumped into hot rock areas that are lacking the water needed to form a naturally occurring geothermal reservoir. The heated water is then directed towards a geothermal power plant to be converted into electricity.

Typically, the reason that a geothermal reservoir does not have enough water is that the rock is too impermeable for the water to flow into the system. Therefore, to introduce water, the rock area must be fractured in order for water to move through it a fast enough rate. The amount of fracturing can be improved through various techniques that are now used in oil and gas fields. The research is aimed at adapting the oil field techniques to geothermal systems, which have differences in size and rock types.

A number of countries are experimenting with such techniques today including France, Australia, Japan, Germany, Switzerland and the United States. The Cooper Basin in Australia is the largest EGS system in development today with an anticipated production level of 5,000 to 10,000 megawatts of electricity.

There is also a great deal of research being applied to the use of geophysical techniques to identify areas where there is the greatest likelihood of finding suitable permeability. That work will advance over time, as techniques are tried, and then the results are corroborated with drill holes.

Decades of work has gone into fine-tuning the design of turbines in steam power plants as those systems are used in conventional coal and gas plants.

The binary cycle technology is also getting a boost from the conventional power sector. Geothermal designers face greater challenges, as they have less control over the heat source. In essence, they must work with the hot water coming from the ground over which they have little control. For that reason, a great deal of effort is required to select the appropriate approaches and design parameters to optimize performance. That expertise will only come from experience.