Organic Rankine Cycle Power Systems: From the Concept to Current Technology, Applications, and an Outlook to the Future

Abstract

The cumulative global capacity of organic Rankine cycle (ORC) power systems for the conversion of renewable and waste thermal energy is undergoing a rapid growth and is estimated to be approx. 2000 MW e considering only installations that went into operation after 1995. The potential for the conversion of the thermal power coming from liquiddominated geothermal reservoirs, waste heat from primary engines or industrial processes, biomass combustion, and concentrated solar radiation into electricity is arguably enormous. ORC technology is possibly the most flexible in terms of capacity and temperature level and is currently often the only applicable technology for the conversion of external thermal energy sources. In addition, ORC power systems are suitable for the cogeneration of heating and/or cooling, another advantage in the framework of distributed power generation. Related research and development is therefore very lively. These considerations motivated the effort documented in this article, aimed at providing consistent information about the evolution, state, and future of this power conversion technology. First, basic theoretical elements on the thermodynamic cycle, working fluid, and design aspects are illustrated, together with an evaluation of the advantages and disadvantages in comparison to competing technologies. An overview of the long history of the development of ORC power systems follows, in order to place the more recent evolution into perspective. Then, a compendium of the many aspects of the state of the art is illustrated: the solutions currently adopted in commercial plants and the main-stream applications, including information about exemplary installations. A classification and terminology for ORC power plants are proposed. An outlook on the many research and development activities is provided, whereby information on new high-impact applications, such as automotive heat recovery is included. Possible directions of future developments are highlighted, ranging from efforts targeting volume-produced stationary and mobile mini-ORC systems with a power output of few kW e , up to large MW e base-load ORC plants.

Thermal Stability of Hexamethyldisiloxane (MM) for High-Temperature Organic Rankine Cycle (ORC)

“…The importance of thermal stability of the working fluid for high-temperature applications is highlighted by Colonna et al [13] stating that this characteristic is still a remarkable deficit of most organic fluids compared to water as working fluid. However, water suffers from other drawbacks like high pressures, necessary superheating and low efficiency below a heat source temperature of 400˝C.…”

Thermoeconomic Evaluation of Modular Organic Rankine Cycles for Waste Heat Recovery over a Broad Range of Heat Source Temperatures and Capacities

“…Hence, Colonna et al [13] identified in their overview on ORC technology a gap in the current literature for thermoeconomic investigation of modular-based ORC units for industrial waste heat recovery. This paper aims to contribute to this field of research by proving the following hypothesis:…”

Non-ideal compressible-fluid effects in oblique shock waves

“…The characterisation of non-ideal compressible-fluid flows is not only of theoretical interest, but also is relevant to applications involving molecularly complex fluids in their dense-gas regime, such as machinery operating in Organic Rankine Cycle (ORC) and supercritical CO 2 power systems, turbogenerators, refrigerators and many others, see reference [14,15,16,17] The present work is organised as follows. In section 2, the Rankine-Hugoniot jump relations across surfaces of discontinuity are recalled along with the admissibility requirements.…”