Optimum Organic Rankine Cycle Design for the Application in a CHP Unit Feeding a District Heating Network

Abstract

Improvement of energy conversion efficiency in prime movers has become of fundamental importance in order to respect EU 2020 targets. In this context, hybrid power plants comprising combined heat and power (CHP) prime movers integrated with the organic Rankine cycle (ORC) create interesting opportunities to additionally increase the first law efficiency and flexibility of the system. The possibility of adding supplementary electric energy production to a CHP system, by converting the prime movers’ exhaust heat with an ORC, was investigated. The inclusion of the ORC allowed operating the prime movers at full-load (thus at their maximum efficiency), regardless of the heat demand, without dissipating not required high enthalpy-heat. Indeed, discharged heat was recovered by the ORC to produce additional electric power at high efficiency. The CHP plant in its original arrangement (comprising three internal combustion engines of 8.5 MW size each) was compared to a new one, involving an ORC, assuming three different layout configurations and thus different ORC off-design working conditions at user thermal part-load operation. Results showed that the performance of the ORC, on the year basis, strongly depended on its part-load behavior and on its regulation limits. Indeed, the layout that allowed to produce the maximum amount of ORC electric energy per year (about 10 GWh/year) was the one that could operate for the greatest number of hours during the year, which was different from the one that exhibited the highest ORC design power. However, energetic analysis demonstrated that all the proposed solutions granted to reduce the global primary energy consumption of about 18%, and they all proved to be a good investment since they allowed to return on the investment in barely 5 years, by selling the electric energy at a minimum price equal to 70 EUR/MWh.

Concept and Design of a Velocity Compounded Radial Four-Fold Re-Entry Turbine for Organic Rankine Cycle (ORC) Applications

“…In this approach, the possibility to use an off-the-shelf (i.e., standard) generator (1500-3000 rpm), with its cost advantage, may offset any efficiency disadvantages when comparing the overall long-term performance of the unit. Furthermore, a lower efficiency might not be crucial because the dumped heat can be used for following heating or cooling purposes in a cogeneration regime [36][37][38][39]. To maintain the advantages of a single turbine wheel directly mounted on the generator shaft (MTG-c-kit), the velocity compounding must be implemented in radial i.e., centripetal flow direction.…”

Organic Rankine Cycle for Energy Recovery System

“…This book contains the successful invited submissions [1][2][3][4][5][6][7][8][9] to a Special Issue of Energies entitled "Organic Rankine Cycle for Energy Recovery System", focusing on a modern technology committed to energy saving and thus capable of producing positive environmental outcomes. Indeed, the organic Rankine cycle (ORC) is a thermodynamic concept already demonstrated as an engineering viable solution for waste heat recovery systems.…”

“…Branchini et al [4] analyse, in their paper, the ORC design and off-design performance in a WHR combined heat and power annual production scenario; the study offers a thermodynamic and economic parametric comparison of different most common fluids and layout options; the study also shows that the ORC application to existing CHP energy systems can be implemented, obtaining improved energy savings. • Baldasso et al [5] consider the potential of ORC on board of ships; a simplified method based on a set of precalculated regression curves of ORC performance is introduced to assess the techno-economic feasibility of the waste heat recovery applied to the engine of the ship.…”

Application of a new constraint handling method for economic dispatch considering electric market

“…In the second case, the OLD problem is divided into economic-emission dispatch (EED) problem and heat-power economic dispatch (HPED) problem. Some artificial intelligence-based methods have successfully solved EED problem [8,9] and HPED problem [10,11].…”