Advanced Waste-to-energy Steam Cycles

AbstractThis paper focuses on possibilities to maximize waste conversion through integration of a Waste-To-Energy (WTE) plant with a gas turbine (GT). In particular, this study investigates the feasibility of utilizing the hot gases leaving the GT mainly to superheat the steam leaving the WTE steam generator. A parametric investigation on the steam production is carried out and the optimum plant match condition in terms of plants capacity ratio is identified and discussed. Detailed modifications to a typical WTE cycle arrangement are presented, in order to evaluate the resulting performance enhancement. Numerical results of a conventional reference WTE plant repowering with different GT commercial units are shown and discussed. Performance indexes, specifically introduced in order to assess the proposed integrated configuration and to allocate power output to each input fuel are illustrated and applied on the considered plant. Results of the study suggest possibilities to create new advanced WTE-GT integrated power plants or to repower existing WTE plants, in order to increase waste to energy conversion

Low temperature district heating networks for complete energy needs fulfillment

In order to reduce fossil fuels consumption and pollutant emissions, high contribution is given by district heating. In particular, the integration with renewable energy may lead to a significant increase in energy conversion efficiency and energy saving. Further benefits can be achieved with low temperature district heating, reducing the thermal dissipations through the network and promoting the exploitation of low enthalpy heat sources. The aim of the paper is the analysis of the potential related to the conversion of existing district heating networks, to increase the exploitation of renewable sources and eliminate pollutant emissions in the city areas. Further aim, in this context, is the optimization – from both energy production and operation management viewpoints – of a low temperature district heating network for the fulfillment of the connected users’ energy needs. To this respect, a traditional network with a fossil fuel driven thermal production plant has been considered and compared with a low temperature district heating scenario, including geothermal heat pumps, photovoltaic panels and absorption chillers. These scenarios have been analyzed and optimized with an in-house developed software, allowing to demonstrate the reduction of primary energy consumption and CO2 pollutant emissions achievable with low temperature networks. In addition, a preliminary economic evaluation has been carried out to compare the proposed solution with traditional district heating

Advanced Waste-To-Energy Cycles

The increase in environmental and healthy concerns, combined with the possibility to exploit waste as a valuable energy resource, has led to explore alternative methods for waste final disposal. In this context, the energy conversion of Municipal Solid Waste (MSW) in Waste-To-Energy (WTE) power plant is increasing throughout Europe, both in terms of plants number and capacity, furthered by legislative directives. Due to the heterogeneous nature of waste, some differences with respect to a conventional fossil fuel power plant have to be considered in the energy conversion process. In fact, as a consequence of the well-known corrosion problems, the thermodynamic efficiency of WTE power plants typically ranging in the interval 25% ÷ 30%. The new Waste Framework Directive 2008/98/EC promotes production of energy from waste introducing an energy efficiency criteria (the so-called “R1 formula”) to evaluate plant recovery status. The aim of the Directive is to drive WTE facilities to maximize energy recovery and utilization of waste heat, in order to substitute energy produced with conventional fossil fuels fired power plants. This calls for novel approaches and possibilities to maximize the conversion of MSW into energy. In particular, the idea of an integrated configuration made up of a WTE and a Gas Turbine (GT) originates, driven by the desire to eliminate or, at least, mitigate limitations affecting the WTE conversion process bounding the thermodynamic efficiency of the cycle. The aim of this Ph.D thesis is to investigate, from a thermodynamic point of view, the integrated WTE-GT system sharing the steam cycle, sharing the flue gas paths or combining both ways. The carried out analysis investigates and defines the logic governing plants match in terms of steam production and steam turbine power output as function of the thermal powers introduced

Available and Future Gas Turbine Power Augmentation Technologies: Techno-Economic Analysis in Selected Climatic Conditions

There exists a widespread interest in the application of gas turbine power augmentation technologies in both electric power generation and mechanical drive markets, attributable to deregulation in the power generation sector, significant loss in power generation capacity combined with increased electric rates during peak demand period, and need for a proper selection of the gas turbine in a given application. In this study, detailed thermo-economic analyses of various power augmentation technologies, implemented on a selected gas turbine, have been performed to identify the best techno-economic solution depending on the selected climatic conditions. The presented results show that various power augmentation technologies examined have different payback periods. Such a techno-economic analysis is necessary for proper selection of a power augmentation technolog

COMPUTING GAS TURBINE FUEL CONSUMPTION TO FIRM UP WIND POWER

As wind power installed capacities increase, it is necessary to deal with the inevitable variability of renewables. Some of that variability can undoubtedly be predicted, but some will in all probability remain unpredictable. In either case, reserve power must be made available. It is clear that the ramp rates that the reserve power must meet will stress technology and call for partload operation at reduced efficiencies. In the present work, we use a gas turbine (GT) dynamic models to simulate the provision of firm power in the Pennsylvania, New Jersey and Maryland grid, PJM. Rowen GT models [1, 2], well established in the literature, are modified to take into account GT ramp rates constrains and fuel consumption at full and partial load, as well as during startup and shutdown. The GTs operational requirements for two summer days in the PJM area are determined, by selecting their number and capacities to result on at least a few units operating at full load. The dynamic models [1, 2] are implemented in the VisSim simulation environment. The results of the work show how the chosen GTs must be operated to provide firm power. Although the operational strategy determined in this paper meets the firm power, in two occasions during the day excess power is produced during a few minutes, to avoid ramping the units down too fast