Small Scale Organic Rankine Cycle (ORC): A Techno-Economic Review

Abstract

Abstract:The Organic Rankine Cycle (ORC) is widely considered as a promising technology to produce electrical power output from low-grade thermal sources. In the last decade, several power plants have been installed worldwide in the MW range. However, despite its market potential, the commercialization of ORC power plants in the kW range did not reach a high level of maturity, for several reasons. Firstly, the specific price is still too high to offer an attractive payback period, and secondly, potential costumers for small-scale ORCs are typically SMEs (Small-Medium Enterprises), generally less aware of the potential savings this technology could lead to. When it comes to small-scale plants, additional design issues arise that still limit the widespread availability of the technology. This review paper presents the state of the art of the technology, from a technical and economic perspective. Working fluid selection and expander design are illustrated in detail, as they represent the bottleneck of the ORC technology for small-scale power production. In addition, a European market analysis is presented, which constitutes a useful instrument to understand the future evolution of the technology.

High-Efficiency Small-Scale Combined Heat and Power Organic Binary Rankine Cycles

“…Nevertheless, economic considerations (discussed, for example, in references [18,22,23]) are not here considered. In the following analysis, the efficiency of a hypothetical gasifier (or wood combustor) is not taken into account because we focused on the ORC engine.…”

“…Technical and economic rewiews about small scale Rankine cycles with organic fluids are in [22,23]. Usually, the selected working fluids are common refrigerants, the maximum temperatures are rather low (though the maximum temperature of the gaseous heat source is high) or, on the contrary, the considered Rankine cycles have a substantial superheating, often with volumetric expanders, [24].…”

Thermo-economic assessment of small-scale organic Rankine cycle for low-grade industrial waste heat recovery based on an experimental application

“…Consequently, it was highlighted that SIC minimization is preferable than electrical power maximization for the ORC adoption. Recently, Tocci et al [81] pointed that the lack of experimental applications and the scarce number of commercial systems in the small-scale range are due to the high value of SIC. With this in mind, the researchers compared SIC values of ORC systems to other technologies currently available in the market to produce electricity.…”

“…For instance, Casci et al [52] tested a 40 kW ORC prototype and estimated that its application in a ceramic kiln could result in a payback period lower than 4 years. Similarly, Tocci et al [81] analyzed generic small-scale ORC systems under different economic scenarios and assumed payback periods of 3 years.…”

“…For instance, the energy generated by the power plant could be injected into the network of the energy supplier. In that case, the economic regime could consist of the continuous energy sale to the energy market (at the pool price [123]) or to take advantage of other regimes, if any, such as net-metering [81]. In this way, Fig.…”