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WORKING FLUIDS FOR USE IN ORGANIC RANKINE CYCLE APPLICATIONS

IP.com Disclosure Number: IPCOM000236583D
Publication Date: 2014-May-05
Document File: 30 page(s) / 72K

Publishing Venue

The IP.com Prior Art Database

Abstract

Aspects of the present invention are directed to working fluids and their use in processes wherein the working fluids comprise effective amounts of HFC-245fa and at least one of HFO-1234ze or HFO-1233zd. In certain aspects HFO-1234ze(Z) or HFO-1233zd(E) are provided in effective amounts to form an azeotrope or azeotrope-like composition with HFC-245fa. The working fluids are useful in Rankine cycle systems for efficiently converting waste heat generated from industrial processes, such as electric power generation from fuel cells, into mechanical energy or further to electric power. The working fluids of the invention are also useful in equipment employing other thermal energy conversion processes and cycles.

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WORKING FLUIDS FOR USE IN ORGANIC RANKINE CYCLE APPLICATIONS

FIELD OF THE INVENTION

    The present invention generally relates to working fluids for improved organic Rankine cycle efficiencies and low global warming potential. In certain aspects, such fluids include 1,1,1,3,3-pentafluoropropane (HFC-245fa) and at least one of 1,3,3,3-tetrafluoropropene (HFO-

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1234ze) or 1-chloro-3,3,3-trifluoropropene (HFO-1233zd).

BACKGROUND OF THE INVENTION

    Water, usually in the form of steam, is by far the most commonly employed working fluid used to help convert thermal energy into mechanical energy. This is, in part, due to its wide availability, low cost, thermal stability, non toxic nature, and wide potential working range.

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However, other fluids such as ammonia have been utilized in certain applications such as in Ocean Thermal Energy Conversion (OTEC) systems. In some instances, fluids such as HFC- 245fa have been utilized to recover energy from waste heat, such as exhausts from gas turbines. Another possibility employs two working fluids, such as water for a high temperature/pressure first stage and a more volatile fluid for a cooler second stage. These hybrid power systems (also 15

commonly referred to as binary power systems) can be more efficient than employing only water and/or steam.

    In the quest to have a secure and reliable power source, data centers, military installations, government buildings, and hotels, for example, use distributed power generation systems. To avoid loss of service that can occur with loss of grid power, including extensive

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cascading power outages that can occur when equipment designed to prevent such an occurrence

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fails, the use of distributed power generation is likely to grow. Typically, an on-site prime mover, such as a gas microturbine, drives an electric generator and manufactures electricity for on-site use. The system is connected to the grid or can run independent of the grid in some circumstances. Similarly, internal combustion engines capable of running on different fuel sources are used in distributed power generation. Fuel cells are also being commercialized for

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distributed power generation. Waste heat from these sources as well as waste heat from industrial operations, landfill flares, and heat from solar and geothermal sources can be used for thermal energy conversion. For cases where low- to medium-grade thermal energy is available, typically, an organic working fluid is used in a Rankine cycle (instead of water). The use of an organic working fluid is largely due to the high volumes (large equipment sizes) that would need

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to be accommodated if water were used as the working fluid at these low temperatures.

    From thermodynamic considerations, the greater the difference between source and sink temperatures, the higher the organic Rankine cycle efficiency. It follows that organic Rankine cycle system efficiency is influenced by the ability to match...