Green & Unseen
The Future of Geothermal Power

Today’s geothermal (aka hydrothermal power) is very limited because it requires a location with large amounts of naturally occurring superheated water trapped close to the surface.

• Iceland has the highest share of renewable energy in any national total energy budget thanks to its natural geothermal, hydropower & other carbon-free power sources [~]
• Icelandic power also costs less than electricity in most other European countries. [~]
• But It’s a little known fact that the US leads the world in geothermal electricity generation! [~]
• The US generates 2555 MW of geothermal power, making up about 0.4% of all the energy produced domestically. [~] [~]
• In the US, the Department of Energy estimates that there are at least 9 Gigawatts of power sitting in untapped hydrothermal systems. [~] (Enough to power 650 million homes)
• But these untapped resources pale in comparison to the 5.15 Terawatts that the Department of Energy estimates could technically be tapped by new technologies like EGS & AGS. [~] (Enough to power the US energy demand 5 times over)

Enhanced Geothermal or EGS is a new technology that can make geothermal energy widely available by creating underground reservoirs that allow water flow & heat extraction.

• In EGS, water is injected at high pressure into generally dry and impermeable rocks.
• The pressure causes natural rock fractures to open.
• These open fractures let circulating water absorb heat from the surrounding rock, making the water very hot.
• At the surface, the boiling water turns into steam which drives an electric generator and produces power.
• After the water is cooled it gets pumped down a second well to be heated again and again in a circular loop. [~]
• By not requiring highly specific geologic conditions, EGS expands the range of locations in which geothermal can be developed. [~]
• The DOE estimates that EGS can support tens of millions of house owners and businesses. [~]
• EGS has major benefits over other energy sources. It’s very efficient, has a long service life, and has many environmental benefits like emitting 99% less CO₂ than fossil fuel-based power. [~]

Why EGS is Safer than Fracking

EGS is often compared to fracking in the oil & natural gas industry, but many differences make EGS far safer and cleaner.

Oil & Gas Fracking:

1. Uses a pressurized mixture of water and chemicals to crack deep rock and extract oil & gas. 
2. Fracking mixtures sometimes contaminate local groundwater. [~]
3. Residents in some towns near fracking wells can light their tap water on fire from dissolved natural gas as a result of fracking. [~]
4. Several tons of this mixture is injected at pressure each day to create more cracks and extract more oil & gas - A typical well can use between 2 million to 7 million gallons of water over the course of its lifetime. [~]
5. This process & the accompanying wastewater re-injection steps are known to cause earthquakes in regions that had previously never experienced them. [~]

EGS:

1. EGS Uses water with fewer chemicals or plain water alone to form cracks very deep underground.
2. Once cracks are formed, no more water is needed & the plant operates on a stable water loop at constant pressure.
3. The stable pressure of the loop reduces earthquake risk.

EGS Risks:

1. No new technology is without its risks, including EGS. 
2. Early EGS tests have been related to earthquakes in Korea and Switzerland. [~]
3. It’s vitally important that more research is conducted on EGS Safety & mitigation measures. We must fully understand the risks & how to avoid them so we can safely tap into the huge potential of EGS technology.

Modern geothermal technology like EGS & AGS use closed-loop systems that emit almost no greenhouse gasses or pollutants.

• Greenhouse gasses like CO₂ & Methane (the main component of natural gas) rise into the atmosphere when we use fossil fuels. These gasses form an atmospheric “blanket” that causes our planet to slowly heat up. [~]
• The more gasses we emit, the more this process accelerates. The effects of this are becoming very clear with the record breaking wildfires in the western US & intensifying storms & flooding in the east. [~]
• Geothermal is poised to play a key role in reducing CO₂ as well as smog & pollutants that come from burning fossil fuels which cause an estimated 3.6 million deaths worldwide every year - mostly from respiratory complications. [~]
• Each year, U.S. geothermal electricity offsets the emission of 4.1 million tons of CO₂, 80 thousand tons of nitrogen oxides, and 110 thousand tons of particulate matter that could have been released by coal-powered plants. [~]
• Better still, scientists have found that geothermal systems can be used to store captured CO₂ within minerals deep underground [~]. They found that using CO₂ in geothermal plants can actually make power production more efficient. [~]

Rain or shine, still or stormy, Geothermal keeps providing stable, clean power 24/7, 365 days a year.

• Many renewables can’t provide power in certain conditions like solar at night & wind on a calm summer's day. This inconsistent output is possibly the single biggest issue preventing full use of renewables.
• Inconsistency is an issue geothermal doesn’t have; making it one of the most reliable sources of sustainable energy.
• Geothermal can also solve demand spikes - for example when everyone flicks on the lights at sunset.
• Today, that spike in electricity is met by firing up highly inefficient & polluting gas-fired “peaker” plants, so everyone’s lights don’t flicker. [~]
• Geothermal solves this by using the earth as a heat battery. By reducing the flow rate through a well, a geothermal plant can let extra heat build up in surrounding rock. When electricity demand spikes, the geothermal plant can let the wells flow at full capacity converting the extra stored heat directly into a surge of power to meet demand.

Advanced Geothermal Systems or AGS bring many of the advantages of EGS but don’t need high-pressure fracturing to allow water flow.

• AGS technologies use precision drilling to cut underground “U” shaped wells several Kilometers on each side.
• These wells function like a reverse radiator, pulling heat from the surrounding rock into a water solution circulating through the sealed well.
• If designed right, AGS wells need no pumps because the thermosyphon effect works to circulate the water from heat alone. [~]
• Because AGS has less surface area where water contacts the hot rock, AGS is better suited for locations with lower power demand like small towns [~]
• AGS technology is often combined with binary power generation. Binary generators transfer the heat energy to a fluid with a lower boiling point than water, making them excellent for converting lower temperature wells to electricity.
• Binary generators can also be used alongside regular turbines in both AGS & EGS to increase efficiency [~]

Geothermal energy has the smallest land footprint of any comparable energy source in the world.

• Geothermal uses 8x less land than solar, 3x less than wind, and 9x less land than coal per gigawatt-hour on average. [~]
• This means geothermal results in less deforestation & frees up land for recreation, farms, & towns.
• Some companies are designing small modular geothermal stations that can power remote towns using a system that fits in a couple of shipping containers. Several small geothermal stations have already been successfully deployed in Alaska. [~]

Like all energy sources, geothermal takes water to build & run.

• Geothermal can use much more water in construction & operation than other renewables and far less than every kind of fossil fuel. [~]
• In areas where water is plentiful, geothermal plants can take advantage of the increased efficiency of water cooling. [~]
• In drier locals, air-cooled binary geothermal power plants use little to no water in operation & can generate electricity from much lower temperatures. [~]
• Technologies like Enhanced geothermal do use a sizable amount of water in the reservoir formation step, but still far less than fossil fuel extraction including fracking for natural gas & oil. [~]
• In EGS reservoir formation, plain water is pumped into the wells. Any available source of water works, so drinking water supplies can be avoided as long as regulatory checks are put in place. [~]

Geothermal or ground source heat pumps can heat and cool homes & buildings at a fraction of the cost of traditional heating & AC.

• Heat pumps take advantage of the mild, but highly stable temperatures just a few feet below the ground to heat and cool very efficiently. [~]
• They can be installed in almost anyone's yard anywhere in the country. [~]
• Nearly 20 million homeowners & businesses installed geothermal heat pumps in 2019 & the market for them is expected to grow substantially. [~]
• While ground source heat pumps have a higher installation cost than traditional heating and cooling systems, one heat pump typically pays for itself in 10 years. [~]
• On top of that, heat pumps commonly last maintenance-free for 25 years and ground loops often last 50. [~]

Geothermal runs on heat & people have applied this heat to a myriad of uses beyond generating electricity.

• Extra heat from geothermal is great for district heating. In fact 85% of households in Iceland have access to heating from geothermal wells. [~]
• Using geothermal for electricity and heating has been shown to increase efficiency of a plant to 70%. [~]
• That’s 150% more efficient than solar, & averages 90% more than coal. [~] [~]
• Geothermal can also be used to mine valuable metals: Metals like lithium carbonate can be extracted from well water. In the Salton Sea, California it’s estimated that 170,000 metric tons of lithium can be extracted annually (Neupane and Wendt 2017). [~]
• At a 2017 price, the Salton Sea lithium has the potential to supply the battery market with as much as $2.3 billion annually in valuable materials [~]

From drill operators to maintenance crews to geologists, many stand to benefit from good-paying jobs in the burgeoning geothermal industry.

• Geothermal ventures need workers with many of the skills found in the oil & natural gas industries and offer more long-term, better-paying local jobs.
• According to the Department of Energy Geovision report, geothermal power plants can provide more than double the long-term local jobs per powered household when compared to other utility-scale power-generation technologies including wind, solar, and gas. [~]
• Some figures from the oil and gas industry are arguing that Geothermal is an amazing opportunity for the fossil fuel industry to switch to an environmentally friendly, stable, and cost effective energy source. Geothermal has many of the same challenges and solutions as drilling in oil and gas meaning oil companies could use their existing talent and investments while staying profitable and dramatically cutting their environmental impact & negative image in the public eye. [~] [~]

Deep EGS is the final frontier of geothermal power. Deep EGS wells can go to depths past 5, 7 or even 9 km to generate heat and electricity anywhere efficiently.

• Below 7-10 km in the earth’s crust, temperatures are hot enough to produce electricity nearly anywhere. [~]
• In already warm areas, deep EGS can tap supercritical water - water that’s neither liquid nor gas. When water becomes supercritical, it’s energy per volume jumps by a factor of 4 and almost doubles the efficiency of turbine generators. [~]
• Several deep EGS test projects are happening around the world. In the U.S. the DOE-funded Utah FORGE site is constructing an 8km deep egs system to show Deep EGS can work, and work safely. More deep test wells are being drilled in Italy & Iceland to show Deep EGS can be safe in many parts of the world.
• Drilling costs are the biggest hurdle to making deep egs commercially viable. Drilling to these depths can cost between 20 million & 400 million dollars with no guarantee heat or permeability at the bottom will be sufficient.
• If a breakthrough in low-cost drilling arrives, Deep EGS will lead to a new era of geothermal usage by utilizing hotter reservoirs at greater depths.
• With technological improvements, deep EGS could be powering 57% of all renewable US electricity generation by 2050. [~]

New Drilling technologies

The DOE, industry and others are making huge strides in developing better & cheaper drilling technology.

• Hydrothermal Spallation Drilling (HSD) is a new form of drilling for hard and brittle rocks. HSD can reduce costs by 15-20% by rapid heating of rock surfaces which allows for the expansion of solid rock under stress. [~]
• Hypersonic drilling is another new drilling technology that can be integrated into current drilling systems to greatly increase drilling speed & reduce costs. [~]
• Hypersonic systems use hypersonic projectiles that break up the rock ahead of the drill bit with 100x times the strength of the rock they’re clearing.
• The Department of Energy ARPA-E program has recently funded a company developing a drilling technology that melts the rock away with millimeter-wave lasers. Their technology also promises to greatly reduce drilling costs. [~]

Installing geothermal today costs about double that of wind, solar, and hydropower, but its high efficiency makes up the difference.

• Geothermal is extremely efficient once installed and it does not require constant input like fossil fuel-based power.
• Geothermal’s efficiency brings down the price of power to 7.8-22.5¢ per kilowatt-hour (kWh) in 2016 - less than electricity costs from solar power.
• 24% to 50% or more of the high upfront cost of a geothermal plant comes from the drilling and reservoir formation steps with drilling costs increasing exponentially for greater depths.
• While technologies are helping us understand the geology below the surface, new geothermal wells sometimes fail to reach proper temperatures or geologic conditions.
• This lack of guaranteed profits makes geothermal very unattractive to potential investors and slows geothermal development.[~]

• Regulatory & Permitting time - The Department of Energy estimates that regulatory streamlining alone could cut new installation time by 4-5 years and allow US geothermal power production capacity to double. [~]
• Public Awareness & Trust - If the public isn’t excited about geothermal & confident in its safety it may never get traction. That’s why we must invest in outreach & research risks and solutions so geothermal power can be widely used.
• Technology & Innovation - We must invest in companies & researchers innovating to find solutions that bring down the cost of drilling & broaden Geothermal's potential.
• Economic Reality - Without amazing technological breakthroughs, geothermal won’t reach the depths & economic potential needed to replace fossil fuels. Experts say we have ten years to get to net-zero carbon emissions to avoid devastating climate change [~]. That’s why we need to advocate a range of carbon-free power including expanded geothermal, hydropower, wind, solar & nuclear. More people need to know about geothermal potential, but it’s not a silver bullet, not yet at least.