Introduction to the Hydrobore
Geothermal Power Facts
Introduction to Geothermal Power
   3 Types of Geothermal Plants
   Maxlore Hybrid Plant
   Links to the Future of Geothermal Energy

Introduction to the Hydrobore

The Hydrobore technology described in Maxlore is an innovative tunneling technology that has the potential to revolutionize the alternative energy industry and our energy transportation infrastructure.

The hydrobore can speed our transition to renewable energy by helping to overcome current limitations in the promising field of geothermal power.

The Hydrobore concept

The Hydrobore, based on existing technology, does not attempt to remove water from the tunnel under construction. Instead, it uses the water to maintain internal tunnel pressure. Filling the tunnel with water ensures the tunnel’s structural integrity at extreme depths in much the same way as a natural aquifer. The tunnel-building equipment itself uses water to cut the stone and remove it from the tunnel. The Hydrobore might be considered a modified submarine, providing power for the tunnel-building equipment as well as work and living space for the crew.

Below is an artistic rendering of a cross section of the Hydrobore as it moves from left to right. Though it is not drawn to scale, this drawing demonstrates several important facts:

All of the mechanisms for drilling the tunnel, building its walls and housing the crew are located on the Hydrobore.
As the Hydrobore moves through the rock, it cuts away a tunnel that is 52 feet in diameter. By the time the Hydrobore has moved through the space it occupies, the crew has built a tunnel wall that is 1 foot thick. The wall is built in several stages so that the material has appropriate time to dry and harden.
The Hydrobore is propelled through the rock by a system of treads which move in opposing directions to keep the Hydrobore upright. If the treads all faced the same way, the Hydrobore would turn over like a screw, making it impossible for a crew to work.

Hydro-Bore Cutaway View

Tunnels, problems and current solutions

Tunnels have myriad applications, from water and energy transportation to geothermal power. Tunnels have been used in many projects ranging from underground and underwater tunnels for transportation – The Chunnel and Boston’s Big Dig – to water-supply tunnels – the 90-mile two-way tunnel supplying water to the Boston metroplex. Historically, it has been too expensive and too dangerous to drill many miles. However, with the advent of the Hydrobore, tunneling becomes safe, efficient and cost-effective.

There are numerous obstacles to consider when building at extreme depths. First is maintaining the structural integrity of the tunnel walls. Second, is keeping the tunnel from filling up with water seepage. Tunnels under construction at extreme depths are often beleaguered by water seepage.

Current tunneling techniques – using Tunnel Building Machines (TBMs) – require “sleeves” that support the sides of the tunnel. This process is time-consuming and expensive. At the same time, under certain conditions TBMs must be supplemented by pumps to remove water seeping into the tunnel. Even under optimal conditions, building in a single-medium, TBMs can build only 20 miles of tunnel per year.

The Hydrobore combines many existing ideas into a tunneling machine that has the capacity to build deeper tunnels at a significantly faster rate. A tunnel built with the hydrobore would provide safe access to geothermal energy from the earth’s core, and could harness the energy necessary for a large-scale geothermal power plant. Accessing and processing geothermal energy is already considered to be the wave of the future in energy consumption. It provides access to vast quantities of clean water, solutions to energy and waste management problems, and it is all made possible through the development of the hydrobore tunneling technology.

For more information, see our FAQ, or Contact Us.

Geothermal Power Facts

Geothermal energy provides more than 2700 megawatts (MW) of electric power to U.S. residents - comparable to 60 million barrels of oil per year, enough for 3.5 million homes. This is only a small fraction of the potential value of geothermal energy in the U.S.
Seven percent of California's electricity is produced by the Geysers, a geothermal plant complex in production since 1960. [note: Columbia Encyclopedia, 6th edition, 2001)
Geothermal electricity is clean - no fossil fuels are burned. Geothermal electricity produced in the U.S. displaces the emission of 22 million tons of carbon dioxide a year!
Geothermal electricity is reliable - plants have average system availabilities of 95% or higher, compared to 60-70% for coal and nuclear plants.
Geothermal electricity is cost-effective - today's cost of geothermal electricity ranges from $0.05 to $0.08 per kilowatt-hour, and technology improvements are steadily lowering that range.
The average geothermal power plant requires only 400 square meters of land to produce a gigawatt of power over 30 years. Compare that with the enormous amount of land needed for coal and nuclear plants and all the open-pit and other mining required for fueling them.
Last but not least, geothermal electricity is homegrown - it reduces our need to import oil, reduces the trade deficit, and adds jobs to the U.S. economy.

This information adapted from: Alameda Power and Telecom, www.alamedapt.com/electricity/geothermal.html

Introduction to Geothermal Energy

Dry Steam
Flash Steam
Binary-Cycle
Maxlore Hybrid
Future of Geothermal Energy

What Is Geothermal Energy?

The term geothermal comes from the Greek geo meaning earth and therine meaning heat. Thus geothermal energy is energy derived from the natural heat of the earth. The earth's temperature varies widely, and geothermal energy is usable for a wide range of temperatures from room temperature to well over 300° F.

Converting Steam and Hot Water to Electricity

Three Types of Geothermal Plants

Three power plant technologies are currently used to convert hydrothermal fluids to electricity:

Dry Steam
Flash Steam
Binary Cycle

The type of conversion used depends on the state of the fluid (whether steam or water) and its temperature.

For current commercial plants, a geothermal reservoir capable of providing hydrothermal resources is necessary. The geothermal plant built in Maxlore would have its own geothermal reservoir created by the hydrobore tunneling machine. Geothermal reservoirs are generally classified as being either low temperature (<150° C) or high temperature (>150° C). Generally speaking, the high temperature reservoirs are the ones suitable for, and sought out for commercial production of electricity. Geothermal reservoirs are found in "geothermal systems" which are regionally localized geologic settings where the earth's naturally occurring heat flow is near enough to the earth's surface to bring steam or hot water to the surface. Examples of geothermal systems include the Geysers Region in Northern California, the Imperial Valley in Southern California, and the Yellowstone Region in Idaho, Montana, and Wyoming.

Dry Steam

Power plants using dry steam systems were the first type of geothermal power generation plants built. They use the steam from the geothermal reservoir as it comes from wells, and route it directly to a turbine which drives a generator that produces electricity. The steam eliminates the need to burn fossil fuels to run the turbine. It also eliminates the need to transport and store fuels! This is the oldest type of geothermal power plant. It was first used at Lardarello in Italy in 1904, and is still very effective. An example of a dry steam generation operation is at the Geysers in northern California, the world’s largest single source of geothermal power. Dry steam plants emit only excess steam and very minor amounts of gases.

Sources: US Department of Energy, Alameda Power and Telecom

Flash Steam

Flash steam plants are the most common type of geothermal power generation plants in operation today. They use water at temperatures greater than 360° F (182° C) that is pumped under high pressure to the generation equipment atthe surface. Upon reaching the generation equipment the pressure is suddenly reduced, allowing some of the hot water to convert or "flash" into steam. This steam is then used to power the turbine/generator units to produce electricity. The remaining hot water not flashed into steam, and the water condensed from the steam is generally pumped back into the reservoir. An example of an area using the flash steam operation is the CalEnergy Navy I flash geothermal power plant at the Coso geothermal field.

Binary Cycle

Binary cycle geothermal power generation plants differ from Dry Steam and Flash Steam systems in that the water or steam from the geothermal reservoir never comes in contact with the turbine/generator units. In the Binary system, the water from the geothermal reservoir is used to heat another "working fluid" which is vaporized and used to turn the turbine/generator units. The geothermal water, and the "working fluid" are each confined in separate circulating systems or "closed loops" and never come in contact with each other. The advantage of the Binary Cycle plant is that they can operate with lower temperature waters (225° F - 360° F), by using working fluids that have an even lower boiling point than water. They also produce no air emissions. An example of an area using a Binary Cycle power generation system is the Mammoth Pacific binary geothermal power plants at the Casa Diablo geothermal field.

Maxlore Hybrid Power Plant

Various hybrids of these three generating processes are currently under development. The Maxlore hybrid power plant concept uses a generating process that combines Flash Steam and Binary Cycle technology.

This hybridization is a result of the changes in the water-transport technology facilitated by the hydrobore. Current power plants use small-diameter (~3ft.) wells to draw water from a limited supply found in a natural underground reservoir. The Maxlore hybrid plant would use a significantly larger bore-hole, up to 50 ft. in diameter. This size, made possible by hydrobore tunneling technology, would substantially increase the amount of water used in the generation process, and the amount of electricity generated.

The Maxlore Hybrid Power Plant proposes several new features that would make it environmentally friendly. It would create power by using the natural heat of the Earth to boil water. Using both ocean water and waste water as inputs (keeping those sources separate the entire time), the boiling process would purify the water leaving usable waste products of fertilizer and salt. Once the steam runs through the turbine creating power, it will be cooled and condensed, and can be used for drinking or irrigation water. This type of power plant, using such a large volume of water to power it, could create as much power as many of the leading nuclear power plants, with none of the dangerous risks to the environment or to the health of the workers and people living in surrounding areas.

Material Transfer System

As the tunnel walls are being built, a partition is erected to separate the tunnel into two tunnels. The partition allows water to flow in and out of the existing tunnel. The water would be pumped in through some water source, and upon exiting the tunnel, would be filtered and returned to that water source. This water can carry buoyant containers filled with materials or waste allowing the Hydrobore to have contact with the surface whenever necessary. These containers would be loaded on and off of the Hydrobore through air-lock chambers similar to those on a submarine.

What differentiates the Maxlore hybrid plant from other power plants currently in use or in production?

Use of artificial (hydrobore-drilled) well-tunnels.
Substantially larger well-tunnels (up to 16 meters in diameter). These tunnels are made possible by the hydrobore drilling technology.
Significantly greater power potential than current plants (as a result of larger-capacity tunnels).
Fewer limitations on site-placement. Because the plant is not dependent on naturally-occurring reservoirs, it may be placed anywhere in proximity to the ocean.
Use of ocean water (instead of naturally-occurring reservoir water) as heat conduit
Desalination and recycling of steam into treated drinking water or fresh water reservoir
Processing of waste-water into potential fertilizer and clean water
Less-expensive method of energy production (large-scale plant)
Lower operating temperatures and pressures than flash-steam plants
Hybrid generation process combining flash steam and binary cycle technology

For more information about the hybrid plant, and the hydrobore technology that makes it possible, see our FAQ.

Links to the Future Of Geothermal Energy

“Steam and hot water reservoirs are just a small part of the geothermal resource. The Earth's magma and hot dry rock will provide cheap, clean, and almost unlimited energy as soon as we develop the technology to use them. “
-US Department of Energy, Office of Energy Efficiency and Renewable Energy, Geothermal Technologies Program

The hydrobore is one of the new technologies whose development can make available this new “cheap, clean and almost unlimited energy.”

U.S. Department of Energy (Geothermal Energy Technical Site):
http://geothermal.id.doe.gov

U.S. Department of Energy (Geothermal Energy):
http://www.eren.doe.gov/geothermal

Sandia National Laboratories (Geothermal Research Department)
http://www.sandia.gov/geothermal/

Energy Quest - California Energy Commission
http://www.energyquest.ca.gov/

Energy Information Administration
http://www.eia.doe.gov/kids/kidscorner.html

GeoHeat Center (Low Temperature Uses of Geothermal Water and Heat):
http://www.oit.edu/~geoheat

Increasing Output at the Geysers: 29 mile-long wastewater pipeline
http://geysers-pipeline.org/

International Ground Source Heat Pump Association (Geothermal Heat Pumps):
http://www.igshpa.okstate.edu

International Geothermal Association
http://iga.igg.cnr.it/index.php

Geothermal Energy Association (Industry Trade Association):
http://www.geo-energy.org/

Geothermal Resources Council (Geothermal Industry Association):
http://www.geothermal.org

Geothermal Heat Pump Consortium
http://www.geoexchange.org

California Department of Conservation, Department of Oil, Gas and Geothermal Resources:
http://www.consrv.ca.gov/dog/

California Energy Commission (Geothermal Energy):
http://www.energy.ca.gov/geothermal

Geothermal Education Office:
http://www.geothermal.marin.org

Page sources:
• Alameda Power and Telecom www.alamedapt.com/electricity/geothermal.html
• The US Department of Energy (Geothermal Energy Technical Site): http://geothermal.id.doe.gov