J.C. Bruno

Thermodynamic Optimization of Organic Rankine Cycles at Several Condensing Temperatures: Case Study of Waste Heat Recovery in a Natural Gas Compressor Station

In this article, the authors performed the thermodynamic optimization of organic Rankine cycles (ORCs) using several working fluids and considered the effect of three heat rejection media in the condenser: cooling water, ambient air, and hot water at high temperature for co- or trigeneration applications. The ORC system was modelled and optimized using the Aspen Hysys process simulator. The objective function is the maximization of turbine power output. Most natural gas compression stations use no heat recovery system. In this study, they applied the optimization procedure to the recovery of waste heat from gas turbines used to drive natural gas compressors in natural gas pumping stations. They used operational data from an existing pumping station to illustrate the potential benefits of ORC systems for this application, taking into account also non-thermodynamic aspects such as toxicity, flammability, and investment cost return. The highest ORC turbine output powers were obtained with aromatic hydrocarbons, then with aromatic fluorocarbons, n-hydrocarbons, and siloxanes (in that order). For the case studied here — a gas turbine of 2.6 MW of mechanical power— the proposed ORC can produce around 1 MWe, with a thermal efficiency of up to 24 per cent depending on the working fluid and condensing temperature.

Stand-alone and grid-connected performance analysis of a regenerative micro gas turbine cogeneration plant

Abstract Distributed generation is an attractive way of producing energy, minimizing transport losses and enhancing energy efficiency. Micro gas turbines in distributed generation systems add other advantages such as low emissions and fuel flexibility. The objective of this paper is to summarize the experimental data from a small-capacity cogeneration plant that consists of a natural gas fired 28 kWe microturbine and a hot-water waste-heat boiler installed at CREVERs testing facilities in Tarragona. The results include the electrical efficiency, natural gas consumption, electrical power quality, thermal power production and air emissions at different loads and ambient temperatures. The electrical efficiency is in the range of the specifications provided by the manufacturer and decreases considerably when the power output drops. Thermal production at full load is around 57 kW. Air emissions are very low at full load and do not increase appreciably until the load is below 60–70 per cent of the full load capacity. The results confirm that the power quality and air emissions in microturbines comply with the existing legal limits, and that they are very competitive in comparison with other technologies in these aspects. Thus, considerable market development is expected in the coming years, although further research and development will be needed.

Operational experience of the polygeneration plant in Parc de l'Alba (Spain): Start-up and first results

Polygeneration systems are highly integrated systems characterized by the simultaneous production of different services (electricity, heating, cooling) by means of several technologies to obtain a higher efficiency than that of an equivalent conventional system. This paper presents some preliminary monitoring results of a polygeneration plant installed in a technological park in Cerdanyola del Vallès (Spain) in the framework of the Polycity project of the European Concerto Program. The plant is composed of three cogeneration gas engines, a direct fired exhaust gas absorption chiller, a single-effect absorption chiller, a compression chiller, a natural gas boiler and a chilled water storage tank of 4000 m3.