New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these applications, mainly because of its ability to recover low-grade heat and the possibility to be implemented in decentralized lower-capacity power plants. In this paper, an overview of the different ORC applications is presented. A market review is proposed including cost figures for several commercial ORC modules and manufacturers. An in-depth analysis of the technical challenges related to the technology, such as working fluid selection and expansion machine issues is then reported. Technological constraints and optimization methods are extensively described and discussed. Finally, the current trends in research and development for the next generation of Organic Rankine Cycles are presented.

Techno-economic survey of Organic Rankine Cycle (ORC) systems

An organic Rankine cycle (ORC) machine is similar to a conventional steam cycle energy conversion system, but uses an organic fluid such as refrigerants and hydrocarbons instead of water. In recent years, research was intensified on this device as it is being progressively adopted as premier technology to convert low-temperature heat resources into power. Available heat resources are: solar energy, geothermal energy, biomass products, surface seawater, and waste heat from various thermal processes. This paper presents existing applications and analyzes their maturity. Binary geothermal and binary biomass CHP are already mature. Provided the interest to recover waste heat rejected by thermal devices and industrial processes continue to grow, and favorable legislative conditions are adopted, waste heat recovery organic Rankine cycle systems in the near future will experience a rapid growth. Solar modular power plants are being intensely investigated at smaller scale for cogeneration applications in buildings but larger plants are also expected in tropical or Sahel regions with constant and low solar radiation intensity. OTEC power plants operating mainly on offshore installations at very low temperature have been advertised as total resource systems and interest on this technology is growing in large isolated islands.

Low­grade heat conversion into power using organic Rankine cycles - A review of various applications

Working fluids for high-temperature organic Rankine cycles

Performance comparison and parametric optimization of subcritical Organic Rankine Cycle (ORC) and transcritical power cycle system for low-temperature geothermal power generation

The organic Rankine cycle (ORC) is commonly accepted as a viable technology to convert low temperature heat into electricity. Furthermore, ORCs are designed for unmanned operation with little maintenance. Because of these excellent characteristics, several ORC waste heat recovery plants are already in operation. Although the basic ORC is gradually adopted into industry, the need of increased cost-effectiveness persists. Therefore, a next logical step is the development of new ORC architectures. Even though there has been a strong renaissance towards ORC research in the last decade, ORC architectures have received relatively little attention. Several barriers can be listed. First, there is the difficulty in assessing the additional complexity of the system. While several advanced cycle designs appear promising from a thermodynamic viewpoint, it is not clear that these represent viable economic solutions. Secondly, there is a lack of experimental data from open literature. Additionally, there is the challenge of coping with various boundary conditions from literature, which makes an objective comparison difficult. In this article an overview is presented of ORC architectures. The performance evaluation criteria and boundary conditions are clearly stated. As well, an overview of the available experimental data is given.

Review of organic Rankine cycle (ORC) architectures for waste heat recovery

Dynamic modeling and optimal control strategy of waste heat recovery Organic Rankine Cycles

Efficiency optimization potential in supercritical Organic Rankine Cycles

Experimental and numerical investigation of direct liquid injection into an ORC twin-screw expander

The method involves supplying a part of a working medium e.g. organic working medium, to a condenser (6) of a power-heat coupling system without supplying the part of the working medium to an expansion machine (4) when a condition is fulfilled. Heat of the working medium supplied by the condenser is transferred to a medium of a heating circuit, which heats an object. A medium guided from a boiler (1) to the condenser is supplied to a heat transfer device i.e. reheater (10), in which the heat from the medium guided from the boiler is transferred to the medium of the heating circuit. An independent claim is also included for a power-heat coupling system comprising an evaporator.

Combined heat and power device and associated method

The invention relates to a thermodynamic cycle device, in particular an ORC device, comprising a preheater for preheating a working medium; an evaporator for evaporating and superheating a first mass flow of the preheated working medium; an expansion machine for expanding the evaporated and superheated first mass flow of the working medium; a condenser for condensing the working medium exiting the expansion machine; a feed pump for pumping condensed working medium to the preheater; and a first supply apparatus for supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in the expansion machine. The invention further relates to a corresponding method.

Richard Aumann

Papers

Dynamic modeling and optimal control strategy of waste heat recovery Organic Rankine Cycles

Efficiency optimization potential in supercritical Organic Rankine Cycles

Experimental and numerical investigation of direct liquid injection into an ORC twin-screw expander

Combined heat and power device and associated method

Control of orc processes by injecting unevaporated fluid