Tiku D.,NTPC Ltd.
IET Seminar Digest | Year: 2015
A new topology for the single-stage grid connection of Photovoltaic (PV) system is proposed in this paper. PV inverters of various types have been proposed previously. Modular multilevel inverter, MMI(HB) using half-bridge submodules is recent and a potential candidate for PV application. Conventionally, the DC link of MMI has a centralized large DC source e.g. PV system connected across it. In the proposed topology, distributed PV system e.g. PV strings/arrays are connected directly across dc link of MMI(HB) submodules (SMs). This allows easy expansion, independent monitoring of each PV string voltage and maximum power point optimization. The dynamics of PV generator is different from the conventional power generator, hence, a new combination of MPPT and decoupled dq controller is proposed to maximize the real power output from the PV strings and limit reactive power exchange with the grid as per the system requirements. In order to validate the proposed concept of new single-stage grid connected PV topology and its controller, simulations were conducted. A detailed model of the proposed 1800W, PV system consisting of 36 PV modules connected across a 13 level three phase MMI (HB) was established. The simulation results of new PV system during fast changes in solar irradiation and reactive power exchange has confirmed the feasibility of proposed MMI(HB) interface for single-stage grid connected high voltage, high power PV system and has verified the validity of the control strategy adopted.
Gupta T.,NTPC Ltd |
Ghosh R.,NTPC Ltd
International Journal of Greenhouse Gas Control | Year: 2015
The increasing greenhouse gas emissions from fossil fuel power plants can be reduced by capturing CO2 from flue gases by means of adsorption, a post combustion capture method. An on-site experiment conducted at a flue gas duct of a 500MW thermal power plant using activated carbon and zeolite samples revealed a sharp drop in the CO2 concentration from 10.6% to 2.4%. Based on this study, a rotating bed adsorber (RBA) system following the combined principles of pressure and temperature swing adsorption is proposed as a viable CO2 capture process. This can be fitted to the existing flue gas duct before the chimney. The RBA consists of disc-shaped adsorbent sheets with parallel passages which are divided into four sectors. At any instant, two of the sectors are exposed to flue gas, while the other two remain in the de-sorption chamber. The de-sorption chamber consists of a heating section which is maintained under vacuum and a cooling section. The effect of the RBA system on the efficiency of a 500MW thermal power plant was also investigated. © 2014 Elsevier Ltd.
Roy J.P.,NTPC Ltd |
Roy J.P.,Birla Institute of Technology |
Mishra M.K.,NTPC Ltd |
Mishra M.K.,Birla Institute of Technology |
And 2 more authors.
Applied Energy | Year: 2011
This paper presents an analysis of non-regenerative Organic Rankine Cycle (ORC), based on the parametric optimization, using R-12, R-123, R-134a and R-717 as working fluids superheated at constant pressure. A computer programme has been developed to parametrically optimize and compare the system and second law efficiency, irreversibility of the system, availability ratio, work output, mass flow rate with increase in turbine inlet temperature (TIT) under different heat source temperature conditions. The calculated results reveal that R-123 produces the maximum efficiencies and turbine work output with minimum irreversibility for employed constant as well as variable heat source temperature conditions. Hence, selection of a non-regenerative ORC during superheating using R-123 as working fluid appears to be a choice system for converting low-grade heat to power. © 2011 Elsevier Ltd.
Roy J.P.,NTPC Ltd |
Mishra M.K.,NTPC Ltd |
Misra A.,Birla Institute of Technology
International Journal of Green Energy | Year: 2011
This paper presents an analysis of regenerative Organic Rankine Cycle (ORC), based on the parametric optimization, using R-12, R-123, R-134a, and R-717 as working fluids superheated at constant pressure. A computer program has been developed to parametrically optimize and compare the system and second law efficiency, irreversibility rates of the system and their components, availability ratio, work output, system mass flow rate with increase in turbine inlet temperature under different heat source temperature conditions. The calculated results reveal that selection of a regenerative ORC during superheating using R-123 as working fluid appears to be a choice system for converting low-grade waste heat to power. Copyright © Taylor & Francis Group, LLC.
Kushwaha T.N.,NTPC Ltd
Procedia Engineering | Year: 2016
Fluid-machines experience a variety of forces during their operation result in different type of dynamic vibration behavior. Fluid induced instability phenomena are one such issue that typically manifests itself as a large amplitude sub-synchronous vibration of the pump shaft and pump structure due to whirl or vortex. When a pump is not operated at its Best Efficiency Point the part of mechanical energy is transferred to the fluid that develops Vortices. It occur in shear layers between the main flow and the re-circulating fluid. This rotating fluid (Vortex) having very low pressure in its centre and forms vapor bubbles at very high rate this vapor bubbles formation and collapse (cavitation) produce hammering effect that begins to participate in the system dynamics and can lead to fluid induced vibration and sound under certain machine state & operating regime favorable to the same. It should be avoided as it can lead to machine failures due to stress-cycle fatigue. © 2016 The Authors.
Adibhatla S.,NTPC Ltd. |
Kaushik S.C.,Indian Institute of Technology Delhi
Applied Thermal Engineering | Year: 2014
The objective of this paper is to perform an energetic and exergetic analysis on a 660 MWe coal fired supercritical thermal power plant at 100%, 80% and 60% of normal continuous rating (NCR) conditions under constant pressure as well as pure sliding pressure operation and to highlight the benefits of the latter over the former. The energetic input, energetic output, exergetic input, exergetic output, energetic and exergetic efficiencies of various components of the supercritical thermal power plant are estimated at 660 MWe, 528 MWe and 396 MWe load under both constant pressure as well as pure sliding pressure operation. Also the energy losses and exergy destruction in various components of a power plant i.e. Boiler, high pressure turbine (HPT), intermediate pressure turbine (IPT), low pressure turbine (LPT), condenser, gland steam coolers, condensate extraction pumps, low pressure heaters (LPH), drip pumps (DP), deaerator (D), boiler feed pump (BFP) and high pressure heaters (HPH) have been calculated. The results have shown that the boiler has the maximum rate of exergy destruction than any other component in the power plant. After the boiler, turbine has the maximum rate of exergy destruction than any other component of the power plant. The study reveals that there is a significant reduction in the rate of exergy destruction at part load conditions for the turbine in case of sliding pressure operation in comparison to constant pressure operation. The rate of exergy destruction in the turbine at 100%, 80% and 60% of NCR conditions is 49.16 MW/43.22 MW/43.92 MW for constant pressure operation and 47.66 MW/37.88 MW/28.94 MW respectively. The BFP power input reduces by 9.39%, 21.52% and 42.5% respectively at 100%, 80% and 60% of NCR conditions if the unit runs in sliding pressure mode compared to constant pressure mode. © 2014 Elsevier Ltd. All rights reserved.
Ray T.K.,NTPC Ltd |
Ganguly R.,Jadavpur University |
Gupta A.,Jadavpur University
Energy Conversion and Management | Year: 2013
Steam temperatures in large capacity boilers of modern electric power stations are maintained closely around the design specification by spraying water in the superheater (SH) attemperator to ensure safe and efficient operation and long plant life. Although the process of attemperation involves exergy destruction, and optimal controllers have previously been proposed for steam temperature control, prior studies on such controllers have not considered exergy as an important parameter. Exergy analysis of a two-stage SH attemperator with real time operation parameters in a 500 MWe pulverized fuel fired power plant pinpoints the avenues for optimization that is beyond the scope of the traditional First-Law based analysis. Strategies to minimize exergy destruction by suitably varying the proportions of stage I and stage II spray flows are established. Further, a MATLAB-SIMULINK-based model is developed and optimal control strategies are devised for SH steam temperature control following a Linear Quadratic Regulator (LQR) approach. Variation of the process parameters and the exergy destructions during the transient operations of the attemperator under stipulated disturbances have been analyzed using the model, with different values of the controller parameters. Guidelines are formulated for the spray flow controller tuning so that the total exergy destructions during the system transients are minimized. © 2012 Elsevier Ltd. All rights reserved.
Vidyanandan K.V.,NTPC Ltd. |
Senroy N.,Indian Institute of Technology Delhi
IEEE Transactions on Power Systems | Year: 2013
This paper introduces a method to improve the primary frequency contribution of grid connected variable speed wind turbine generators (WTGs). Using their energy reserve margins, deloaded WTGs are controlled to provide relief to the grid during depressed frequency conditions. The frequency support from individual WTGs is regulated based on the available reserve, which depends on the prevailing wind velocities. By continuously adjusting the droop of the WTG in response to wind velocities, its primary frequency response is significantly improved in terms of reduced stresses on WTGs during low wind speeds. The impact of variable droop operation on two aspects of WTG operation is investigated-primary frequency contribution and smoothening power fluctuations caused due to changes in wind speed. Also highlighted is the usefulness of this control when adopted by wind farms. © 2012 IEEE.
Jayan V.,NTPC Ltd
Materials at High Temperatures | Year: 2012
Quantification of carbide phase changes by X-ray analysis, with an objective of actual life assessment of service exposed 2.25Cr - 1Mo boiler tubes is described. Carbide transformations and their compositional variations in specimens subjected to extended service (~5-18 years) from a power plant were investigated by X-ray diffraction and X-ray fluorescence analysis of extracted carbide precipitates. Quantitative estimation of equilibrium carbide phase M 23C 6 by Rietveld's refinement technique showed a systematic increase with service. Carbide composition analysis revealed a decrease in Mo wt% with ageing. Based on this result, two life assessment methods were proposed and applied to few unknown specimens for its validation. The computed life was in good agreement with plant operating data.
News Article | October 6, 2016
Fortune: This Is How Political the Decline of Coal Has Become Showing just how political the decline of the U.S. coal industry has become, Appalachia’s infamous imprisoned coal baron just claimed he’s a “political prisoner.” Five months ago, the former CEO of coal giant Massey Energy, Don Blankenship, headed to prison in Taft, Calif. to serve out a year-long sentence. He was convicted for conspiring to willfully violate mine safety standards following an explosion that killed 29 coal miners, the worst coal mining disaster in decades. This week, Blankenship continued to lay out his defense from prison without the use of a computer, describing himself an “American political prisoner” in a 68-page brochure that’s posted to his website. He said he wants to tell his story that “Americans need to know.” Slate: The Paris Climate Agreement Is Officially Happening. Unless Donald Trump Wrecks It. The Paris climate change agreement passed a crucial milestone today, ensuring that it will officially go into effect in 30 days. The 195-country agreement was negotiated last December and signed at the U.N. in April, but in order to become official, it had to be ratified by at least 55 countries, as well as by countries accounting for 55 percent of global emissions. A big chunk of that came at the G20 meeting last month when President Obama and Chinese President Xi Jinping officially committed their countries, which account for 38 percent of emissions between them. India, the world’s third-largest emitter, officially joined last week. With the addition of Canada, Nepal, and seven EU countries today, we’re now at 71 countries and 58.7 percent of emissions. It’s a deal! RenewEconomy: Could Household Battery Storage Have Prevented the SA Blackout? Energy experts are still scratching their heads about what they could have done to prevent the massive, state-wide blackout that occurred in the midst of a one-in-50-years storm last month. The answer may lay inside South Australian homes. Or at least, it should do. And it’s battery storage. Dean Spaccavento, the CEO of Australian energy management software company Reposit Power, says battery storage placed in thousands of homes in Adelaide and the surrounding region -- and linked through smart software -- could have provided the emergency supply to help stabilize the network at its moment of crisis. India’s largest power generator, which is spearheading Prime Minister Narendra Modi’s ambitious clean-energy goals, is expanding its solar target and slowing down development of its coal-based plants based on concerns that the cost of renewables will be cheaper than conventional energy. NTPC Ltd. will expand its target of setting up 10 gigawatts of solar capacity, Chairman Gurdeep Singh told Bloomberg New Energy Finance in an interview. It will also support building of 15 gigawatts of solar capacity by buying power from producers and selling it to distribution companies. It is exploring new opportunities such as solar-equipment manufacturing, solar parks and electric-vehicle charging infrastructure. The Huffington Post: Hurricane Matthew’s Strength Is Yet Another Climate Change Indicator Hurricane Matthew, a record-shattering storm that is unusual for October, is a reminder of climate change’s potential to turn seasonal weather events into extreme, year-round threats. Matthew, which meteorologists downgraded from a rare Category 5 to a Katrina-magnitude Category 3 on Wednesday, could make landfall in southeast Florida as early as Thursday, and threatens northeast Florida and the coasts of Georgia and South Carolina through Saturday. The storm has already claimed at least 11 lives in Haiti, the Dominican Republic, Colombia and St. Vincent and the Grenadines. The storm has surpassed several milestones as one of the strongest, longest-lasting hurricanes of its kind on record. But on top of that, scientists note, it’s atypical for this time of year.