Introduction

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 dispatched.

The four primary modules are as follows.

1. 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.
2. 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.
3. 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.
4. 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 heat.