This paper presents a review of the organic Rankine cycle and supercritical Rankine cycle for the conversion of low-grade heat into electrical power, as well as selection criteria of potential working fluids, screening of 35 working fluids for the two cycles and analyses of the influence of fluid properties on cycle performance. The thermodynamic and physical properties, stability, environmental impacts, safety and compatibility, and availability and cost are among the important considerations when selecting a working fluid. The paper discusses the types of working fluids, influence of latent heat, density and specific heat, and the effectiveness of superheating. A discussion of the 35 screened working fluids is also presented.

A review of thermodynamic cycles and working fluids for the conversion of low-grade heat

The present invention provides a system for drilling boreholes having a downhole subassembly which contains an acoustic measurement-while-drilling system. The acoustic system contains an acoustic transmitter and receiver for determining the acoustic velocity through the formations surrounding the borehole ad an acoustic transmitter and a set of receivers for determining the bed boundaries surrounding the borehole formation utilizing the acoustic velocities measured by the system. The downhole subassembly also contains a computing system which performs computations downhole and transmits certain answers uphole during the drilling operations. The bed boundary information is utilized to drill the wellbore along a desired wellbore path. The downhole computing system correlates the acoustic sensor measurements with other measurement-while-drilling measurements and transmits selected correlated information uphole. The downhole computing system contains predetermined well profile which is updated based on the bed boundary information. The system may be adapted to correct or update seismic data and offset well data based on acoustic sensor system measurements.

Drilling system with an acoustic measurement-while-driving system for determining parameters of interest and controlling the drilling direction

A supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power

Due to personal and environmental safeties along with various advantages, CO2 became a potential choice as working fluid for both heat engine and heat pump cycles. Because of better temperature glide matching between heat source and working fluid during heat addition leading to no pinch limitation, CO2 has been proposed recently as working fluid for supercritical Rankine cycle with low grade heat sources. Supercritical Rankine cycle and its various working fluids, heat sources, heat sinks and analysis approaches, and performance analyses and optimization of various supercritical CO2 Rankine cycle configurations along with comparison with other working fluids, prototype development, component design and challenges are well-grouped and discussed. Supercritical CO2 Rankine cycle is superior to both steam and organic Rankine cycles, whereas yields mix results compared to other fluids in supercritical Rankine cycle with system compactness and environmental benefit as unique advantages. Future research pathways regarding to system components, experimentation, operating parameter optimizations, control strategies, etc. are discussed as well. Although, there is no supercritical CO2 Rankine cycle in operation up to now, it is becoming a future pathway due to its promising research outcomes and this review will be useful for further progress.

Review and future trends of supercritical CO2 Rankine cycle for low-grade heat conversion

The present disclosure provides several methods for selecting and transmitting information from downhole using more than one channel of communication wherein data streams transmitted up each communications channel are each independently interpretable without reference to data provided up the other of the communications channels. Preferred embodiments incorporate the use of a combination of at least two of mud-based telemetry, tubular-based telemetry, and electromagnetic telemetry to achieve improved results and take advantage of opportunities presented by the differences between the different channels of communication.

Dual channel downhole telemetry

A geothermal energy recovery system of improved efficiency makes use of thermal energy stored in hot, solute-bearing well water as it is pumped upward to the earth's surface through an extended heat exchange element for continuously heating a downward flowing organic fluid to a supercritical state. Some of the energy of the latter fluid is used within the well for operating a turbine-driven pump for pumping the hot, solute-bearing well water at high pressure and always in liquid state to the earth's surface, where it is reinjected into the earth in another well. The temperature difference between the upward flowing brine and the downward flowing organic fluid is maintained finite in a predetermined manner along the subterranean extended heat exchange element. After driving the deep-well turbine-driven pump, the organic fluid arises to the earth's surface in a thermally insulated conduit; at the earth's surface, vapor turbine electrical power generation equipment is driven by the heated organic fluid which is then returned into the well for reheating in the extended heat exchanger.

Geothermal energy conversion system

A system for the transmission of data along a borehole during drilling operations which includes an acoustic transmitter receiver and mechanical filters. Data is acoustically propagated from the transmitter to the receiver along a portion of the drill string which is isolated from noise generating elements of the drilling system by means of the mechanical filters.

Acoustic isolation for a telemetry system on a drill string

A geothermal energy recovery system of improved life duration makes use of thermal energy stored in hot, solute-bearing well water as it is pumped upward to the earth's surface through an extended heat exchange element for continuously heating a downward flowing organic working fluid to a supercritical state. Some of the energy of the latter fluid is used within the well for operating a turbine-driven pump for pumping the hot well water at high pressure and always in liquid state to the earth's surface, where it is reinjected into the earth in a second well. After driving the deep-well turbine-driven pump, the organic fluid still in supercritical state arises toward the earth's surface in a thermally insulated conduit; at the earth's surface, vapor turbine electrical power generation equipment is driven by the ascending organic fluid, after which it is returned into the well for re-heating in the extended heat exchanger. The invention provides a long life, closed-loop fluid lubricant pumping and cooling system for the bearings of the turbine and brine pump system, normally isolated from the working fluid loop and the hot brine pumping and heat exchange loop. Should the pressure level within the lubricant loop fall below a predetermined level, auxiliary means are provided for coupling working fluid into the lubrication loop to maintain the pressure within the loop above that of the hot brine, thus excluding intrusion of the corrosive brine.

Gravity head geothermal energy conversion system

A geothermal energy transfer and utilization system makes use of thermal energy stored in hot solute-bearing well water to generate super-heated steam from an injected flow of clean water; the super-heated steam is then used for operating a turbine-driven pump at the well bottom for pumping the hot solute-bearing water at high pressure and in liquid state to the earth's surface, where it is used by transfer of its heat to a closed-loop boiler-turbine-alternator combination for the generation of electrical or other power. Cooled, clean water is regenerated by the surface-located system for re-injection into the deep well and residual concentrated solute-bearing water is pumped back into the earth.

Geothermal energy system and method

The operation of a geothermal well power-generation system is monitored by sensor, communication, and performance monitoring equipment permanently associated with the operating power generation system. Sensors detect changes in well water temperature, in water pressure below and above the pump, and in pump rotating speed. This data is transmitted by multiplex communication to receiver and utilization means at the earth's surface. A novel permanent magnet generator system supplies the signal representative of pump rotation speed and also supplies electrical power for the multiplex communication of the sensor output signals.

Hugh B. Matthews

Papers

Geothermal energy conversion system

Acoustic isolation for a telemetry system on a drill string

Gravity head geothermal energy conversion system

Geothermal energy system and method

Geothermal energy pump and monitor system