What Is The Next Generation Geothermal Technology?

Geothermal energy is thermal energy generated and stored in the Earth. Traditional geothermal power plants utilize hydrothermal resources where there is existing hot water or steam underground that can be tapped and brought to the surface to turn turbines for electricity generation. This type of geothermal energy currently provides only a small fraction of the world’s energy needs.

Next generation geothermal technologies aim to greatly expand the potential of geothermal energy by enabling access to the Earth’s vast resources of hot dry rock through new drilling and reservoir creation techniques. By accessing the enormous amount of heat beneath the surface across large areas, next gen geothermal has the potential to provide consistent, renewable base load power to supplement intermittent sources like wind and solar.

Some of the key innovations in next generation geothermal technology include enhanced geothermal systems, deep drilling capabilities, reservoir stimulation through fracturing, binary power plants, low temperature geothermal applications, supercritical geothermal resources, co-production with oil and gas, and geothermal desalination. This article will provide an overview of these emerging geothermal technologies.

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Enhanced Geothermal Systems

Enhanced Geothermal Systems (EGS) are a next-generation geothermal technology that aims to produce renewable energy from geothermal resources that have insufficient permeability and fluid saturation. EGS expands the geothermal resource base by engineering reservoirs in hot dry rock through hydraulic stimulation.

EGS works by injecting fluid into drilled wells to open up existing fractures in hot dry rock and create an artificial geothermal reservoir. The injected fluid transfers heat from the rock to the surface where it can be used to generate electricity via a power plant. The now cooled fluid is re-injected into a production well to complete the loop.

The key benefits of EGS compared to conventional geothermal power include:

Access to geothermal resources in areas without natural reservoirs
Increased energy output through engineering larger reservoirs
Potential to provide baseload renewable energy almost anywhere

Overall, EGS aims to unlock the vast global heat resource stored in hot dry rock for clean renewable power generation. The technology is still in the demonstration phase but holds great promise for the future.

Deep Drilling Advances

New drilling techniques are enabling access to deeper geothermal resources than ever before. Advanced hard rock drilling methods adapted from the oil and gas industry now allow wells over 10,000 feet deep. These deep wells tap into hotter temperatures only accessible miles below the surface. The higher underground temperatures produce more energy that can be captured and converted into electricity.

Coiled tubing drilling is one important technique being utilized. It allows faster drilling through hard crystalline basement rock than conventional rotary methods. The continuous coiled pipe can penetrate to depths double that of earlier geothermal projects. This enables economical access to 358°F to 662°F resources that were previously unreachable.

Directional drilling is also opening up new deep geothermal reservoirs. Steerable drill bits can precisely orient wells and bore horizontally into ideal rock formations. Multilateral wells can branch out underground into multiple zones from a single surface location. This maximizes production from a single drilled hole. Directional drilling provides greater flexibility in finding and tapping into deep geothermal resources.

These advanced drilling capabilities are unlocking a new generation of deep geothermal systems. Previously untapped 400°F to 600°F zones are now within reach across geologic regions worldwide. This will dramatically expand geothermal energy production.

Fracturing and Reservoir Enhancement

One important advancement in next generation geothermal technology is the use of fracturing and reservoir enhancement techniques to improve the output and sustainability of geothermal systems. By creating fractures in hot, impermeable rock and enhancing underground geothermal reservoirs, more heated fluid can be accessed and circulated through geothermal power plants.

Fracturing techniques like hydraulic fracturing and thermal fracturing create new cracks and fissures in deep, hot rock formations. This allows for greater fluid volumes to flow through the fractured rock, increasing the amount of heat energy that can be captured and converted to electricity. These fracturing methods are adapted from techniques long used in the oil and gas industry.

Reservoir enhancement is also critical. By injecting water into depleted parts of a geothermal reservoir, the subsurface system can be replenished, pressurized and heated back up over time. This allows geothermal reservoirs to be managed and sustained for much longer power production. Advanced modeling and seismic mapping of reservoirs informs enhancement techniques.

With fracturing unlocking more of Earth’s innate heat, and reservoir enhancement strategically restoring geothermal reservoirs, the next generation of geothermal power promises vastly more robust and renewable clean energy output.

Binary Cycle Power Plants

Binary cycle power plants are an important advancement in geothermal technology. Unlike traditional steam plants, binary cycle plants utilize lower temperature reservoirs. This expands the number of geothermal resources that can be utilized for power generation.

Binary cycle plants work by passing geothermal fluid through a heat exchanger. This heats and vaporizes a secondary working fluid with a lower boiling point than water, such as isobutane or isopentane. The vapor spins a turbine to generate electricity. The vapor is then condensed and recycled through the heat exchanger.

Binary cycle plants are more efficient than steam plants at converting geothermal heat into electricity. Steam plants lose energy rejected from the turbines as waste heat, but binary plants recover this using the condensed working fluid. Binary plants can convert 10-13% of the heat energy into electricity, compared to only 7-10% for steam plants.

Low Temperature Geothermal

Low temperature geothermal resources are more common than high temperature resources and can be utilized for direct heating applications or with geothermal heat pumps. While high temperature geothermal systems require temperatures above 150°C for electricity generation, low temperature geothermal systems can operate with temperatures as low as 30-150°C.

Geothermal heat pumps, also known as ground source heat pumps, take advantage of shallow subsurface temperatures to provide space heating and cooling in residential and commercial buildings. These systems circulate fluid through pipes buried underground to transfer heat between the earth and the building. In the winter, the earth provides a heat source as fluid extracts warmth from the ground. In the summer, the relatively stable underground temperatures allow excess heat to be removed from the building.

Geothermal heat pumps are highly energy efficient as they leverage the free renewable thermal energy stored in the ground. They can reduce energy consumption for space conditioning by up to 50% compared to conventional HVAC systems. The technology is mature and has been utilized for decades in certain parts of the world. However, there is ample room for continued growth and innovation in geothermal heat pumps to further improve efficiency and expand adoption globally.

Supercritical Geothermal Systems

One promising area of next generation geothermal technology is the development of supercritical geothermal systems. These systems operate at extremely high temperatures and pressures, above the critical point where distinct liquid and gas phases do not exist.

Conventional geothermal power plants rely on flashing hot water or steam from a reservoir to turn turbines. Supercritical systems can potentially access vastly greater amounts of heat by tapping reservoirs at depths of 3-4 miles with temperatures over 700°F and pressures of 3,000+ psi.

At supercritical conditions, the hot fluid takes on unique properties, able to transfer heat more efficiently. New turbine designs and materials that can withstand the intense temperatures and pressures are needed to harness this massive source of clean, renewable power.

While supercritical geothermal systems are still in the early stages, they represent an exciting possibility for the next generation of geothermal energy production.

Co-Production with Oil and Gas

There are opportunities to utilize geothermal energy in conjunction with oil and gas production, creating synergies between the two industries. Existing wells drilled for oil and gas exploration can potentially be converted into geothermal production wells after their oil or gas production declines. Drilling knowledge and technology developed by the oil and gas industry can also be applied to geothermal drilling. Pumped hydrothermal fluids can help extend oil recovery through techniques like thermal enhanced oil recovery. The large amounts of wastewater produced from oil and gas production can also potentially be utilized for geothermal energy, and then re-injected into the subsurface.

Co-production of geothermal energy with oil and gas allows for resource optimization and reduces the energy and costs associated with drilling entirely new geothermal wells. There are already some co-production projects producing electricity, such as the Rocky Mountain Oilfield Testing Center and the Chena Hot Springs geothermal plant. With further research and field testing, there could be many more opportunities to utilize the oil and gas infrastructure for geothermal energy production.

Geothermal Desalination

Geothermal energy presents opportunities for co-production of freshwater through desalination. Low-temperature geothermal fluids, generally below 150°C, can be used to provide heat for multi-stage flash distillation or multi-effect distillation desalination plants. The geothermal heat replaces the need to burn fossil fuels to heat the brine input stream.

A number of demonstration and commercial plants have shown the viability of geothermal desalination. The first was a small 200 m3/day plant in Iceland in 2000. Larger scale projects producing 10,000 to 20,000 m3/day have since come online in the Middle East and North Africa region, where heat and water scarcity drive innovation in this area.

Binary cycle geothermal plants can also provide low-pressure steam as an input to thermal desalination processes. The steam condenses, releasing heat, which is used to evaporate input brine. Combining geothermal electricity generation with desalination can improve project economics and make use of brine streams.

With growing global water demands, geothermal desalination provides a sustainable solution that takes advantage of geothermal heat for zero-emissions freshwater production. The combination of desalination with geothermal power generation will open arid regions to large-scale development of these renewable resources.

Conclusion

Geothermal energy has promising potential as a renewable, clean energy source. Several key technologies are driving innovation in the geothermal space and enabling broader utilization of this energy resource.

Enhanced geothermal systems use advanced drilling techniques to access deeper hot rock reservoirs, while technologies like fracturing and reservoir enhancement create subsurface heat exchange systems. Binary cycle power plants allow lower temperature reservoirs to generate electricity efficiently. Emerging ideas like supercritical geothermal take advantage of novel materials and processes to improve the economics.

Co-production with existing oil and gas wells can unlock geothermal potential in mature fields. And direct uses like geothermal desalination highlight non-electric applications. Each of these next generation technologies offers different advantages and is unlocking new geothermal resources or improving utilization.

The future outlook for geothermal energy is positive. With continuing innovation and declining costs, geothermal has the opportunity to play a major role in the global transition to renewable energy. New technologies will open up geothermal resources around the world and support the decarbonization of electricity generation, heating, and industrial processes.