1. Field of the Invention
The present invention relates, in general, to power generation and conversion, to cryogenic systems, and to improvements in heat engines and systems, and more particularly, to energy conversion systems and methods that utilizes a working fluid, such as a biatomic gas, that is recirculated within a high pressure tank that contains a compressor and is exposed to a heat exchange surface to enhance existing heat engine efficiencies and that further utilizes a cold reservoir to capture additional energy from the working fluid.
2. Relevant Background
Modem society has an insatiable and growing thirst for energy and for devices and systems that consume large quantities of energy. Presently, the largest sources of energy are non-renewable including the fossil fuels of coal, oil, and gas. Renewable energy sources are only a small portion of the global energy supply and include wind, solar, and geothermal sources. Energy sources are generally converted by conversion systems using heat engines and other devices into other forms of energy such as thermal energy (or heat) and mechanical energy. It is estimated that in the not too distant future non-renewable energy sources will become depleted or that the costs associated with converting these sources to heat and other useful energy will significantly increase causing many of these sources to be inaccessible to large parts of the population. Hence, there is an ongoing societal need for more efficient methods and systems for converting energy from non-renewable and renewable energy sources into clean, useful energy.
Common energy conversion systems employ heat engines to convert heat energy from renewable or non-renewable energy sources to mechanical energy. The examples of heat engines are numerous including steam engines, steam and gas turbines, spark-ignition and diesel engines, or external combustion and the Stirling engine. Each of these heat engines or systems can be used to provide the motive power or mechanical energy for transportation, for operating machinery, for producing electricity, and for other uses. Heat engines typically operate in a cycle of repeated sequences of heating and pressurizing a working fluid, performing mechanical work, and rejecting unused or waste heat. At the beginning of each cycle, energy in the form of heat and/or pressure is added to the working fluid forcing it to expand under high pressure so that the fluid performs mechanical work. In this manner, the thermal energy contained in the pressurized fluid is converted to kinetic energy. The fluid then loses pressure, and after unused energy in the form of heat is rejected, the fluid is reheated or recompressed to restore it to high pressure.
Unfortunately, existing heat engines do not convert all the input energy to useful mechanical energy in the same cycle as generally some amount often in the form of heat is not available or utilized for the immediate performance of mechanical work. The fraction of thermal energy that is converted to net mechanical work is called the thermal efficiency of the heat engine. The maximum possible efficiency of a heat engine is that of a hypothetical or ideal cycle, called the Carnot Cycle (based on absolute zero as the starting point). Existing heat engines generally operate on much less efficient cycles, such as the Otto, Diesel, Brayton, or Stirling Cycles, with the highest thermal efficiency achieved when the input temperature is as high as possible and the sink temperature is as low as possible. The “waste” or rejected heat is sometimes used for other purposes, including heating a different working fluid, which operates a different heat-engine cycle or simply for space heating but most often the rejected heat is released to the environment. Another common efficiency problem is that when compressors are used to compress incoming air or working fluid and are driven by a shaft driven by the device creating the mechanical power, e.g., a turbine using the Brayton cycle, and the compressor consumes a large portion of the created shaft power, e.g., up to two-thirds of the power.
Other problems often accompanying the use of heat engines is how to achieve proper timing along with appropriate intake and outlet valving and how to achieve adequate sealing of such devices. Standard timing valves with camshafts and common valves are useful for standard piston expanders and compressors but are not as desirable and useful for timing the input of high pressure gases when nutating or eccentric shafts are used in expanders and/or compressors used in heat engines. The concepts of precession and nutation of bodies with energy being transferred from the rotational motion of a nutating body, such as in an internal combustion engine, have been tried, but generally it has proven very difficult to valve such devices and even more difficult to design such nutating and/or eccentric devices for proper sealing of working gases or fluids. Often, these non-standard devices are not adopted because high precision and relatively expensive materials and machining has been required to obtain useful valving and sealing systems for these devices or sealing has simply been done through the use of flat sealing strips.
Hence, there remains a need for improved devices and techniques for converting energy in a working fluid with increased efficiencies. Preferably, such devices and techniques are selected to facilitate the use of non-standard compressors and/or expanders that incorporate nutation, eccentric drives, or epicycling (e.g., the use of an eccentric drive limited to motion in a single plane rather than the “wobbling” of a nutating device) by providing improved inlet and outlet valves and sealing systems.