The Power Tube Argus is a GEOMAGMATIC
device that differs from a standard geothermal system in that it does
not need water, steam or steam pressure to operate. It uses only the
heat of the Earth and low to medium temperature heat, 110-200 C.
The Argus units are designed for the 1-5 and 10 Megawatt market.
The installation consists of mostly a down-hole system with a very small
surface footprint. Argus operates with a heat exchanger and in
addition can also work with a thermal riser. The thermal riser option
is used when the required temperatures are further down than the total
length of the power plant itself. The thermal riser contains a
biodegradable, synthetic, heat exchange fluid that circulates through
its coaxial, flexible system which transfers the heat found at lower
temperatures into the heat exchanger at the base of the installation.
Power Tube Argus units are designed to be minimal maintenance units.
The maintenance is performed by a remote supervisory center via
satellite. The system is designed so that the supervising controller
can adjust (tweak) the settings of the on-board programmable logic
controller (PLC) as needed. If needed, a local technician can be
The four primary modules are as follows.
- Turbine/Generator: The prime power source
in the Power Tube system is the turbine, or turbo-expander, and is used
to drive the electrical generator at speeds up to 10,000 rpm. The
working fluid in the turbine is an isopentane/isobutane mixture. The
pure superheated vapor (working fluid) will be present at the inlet and
exit, without liquid (droplets) present. As a general rule, higher
temperatures increase turbine efficiency. A unique feature of the Argus
configuration is the vertical turbine orientation. The generator is
directly coupled to the turbine and is used to generate electricity.
- Condenser and Pump: The condenser is a
cross flow, finned, air cooled heat exchanger used to condense the
working fluid into a liquid before entering a high pressure pump. In
the current design, working fluid enters the condenser as a vapor at
reduced pressure and temperature and should reach full condensation
before the condenser exit. The pump then pressurizes the condensed
working fluid back to the initial turbine inlet pressure.
- Boiler: The boiler is a shell and tube
heat exchanger used to convert the working fluid into a high
temperature, high pressure vapor for inlet into the turbine. The
working fluid is inside the tubes, enters the boiler as a liquid, and
exits as a vapor. A heating fluid flows through the thermal riser up
from the hot geothermal resource and enters the vertically oriented
boiler on the shell side. The heating fluid is in intimate contact with
the tubes and heats the working fluid. Heating fluid leaves the boiler
and returns to the bottom of the riser to be reheated by the geothermal
resource. Working fluid leaves the boiler as a superheated vapor and
enters the turbine.
- Thermal Riser: The Power Tube thermal riser is the device which extracts heat from a geomagmatically
(geothermally) active region of the earth's subsurface. The current
concept uses two concentric tubes to flow a fluid down to the hot region
and return the heated fluid back to the boiler. The thermal riser
configuration will minimize pumping losses while still providing the
necessary cross section and flow velocity to transport the required