Informatics Publishing Limited

M. Siddhartha Bhatt ¹

Affiliations
1 Director ,Central Power Research Institute, Bangalore-560080, IN

Abstract

The presently tapped potential for cogeneration from sugar plants in Indiain India is very low (4.8 GW). There is the good untapped potential of around 10 GW from the sugar sector besides opportunities for enhancing the annual plant load factor (PLF) during the off-season phase. The use of Concentrating Solar Thermal power (CST) in the Indian power sector is gaining importance since 2014 as the linear parabolic trough technology is now available. A number of plants based on CST have been established in Rajasthan and Tamil Nadu. In this paper, the integration of CST plants with sugar based cogeneration plants (where the PLF is limited by the availability of bagasse) is presented in view of the great strategic importance of this combination which does not need the power block for CST and enhances the capacity utilization of sugar mills. By the introduction of CST, during the crushing seasons there is saving in bagasse and during the offseason, generation is ensured. On the overall, by the use of CST, the annual PLF can be increased from 69 % to 77 %.

Keywords

Renewable power, concentrating solar power, cane based cogeneration, sugar mills.

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M. Siddhartha Bhatt ¹

Affiliations
1 Additional Director, Energy Efficiency & Renewable Energy Division,Central Power Research Institute, Bangalore - 560080, IN

Abstract

This paper presents a comprehensive analysis of water utilization in concentrating solar thermal (CST) thermal power stations (TPS) keeping in mind the experience of operating coal plants. The water utilization is divided into three modes: water hold-up, water circulation and water consumption. The water hold-up and circulation represent the minimum quantity of water required for running a power plant with a few days autonomy. The water consumption represents the extent of replenishment required on a continuous basis. On the basis of quality, the consumption can be classified into: raw water, soft water and demineralized (DM) water. The reserve hold-up in a CST station of 1 GW is around 0.95 to 1.05 million m³ per GW which corresponds to 9-10 days consumption. The working hold-up inside the plant is 0.27 million m³ per GW. The water circulation rate for a 1 GW CST station is 7500 m³/h or 0.18 million m³/day. The major water consumption which is not generally tracked or measured is conveyance loss between the raw water intake source and the power station intake point which can be as high as 30 %. Loss of DM water directly affects the energy efficiency as it mostly represents the high quality steam lost from the system and has a high cost of production.

Keywords

Water consumption, water hold-up, circulation flow, specific water consumption,conveyance loss.

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M. Siddhartha Bhatt ¹

Affiliations
1 Additional Director, ERED, Central Power Research Institute, Bangalore - 560080, IN

Abstract

This paper presents an efficiency map of a solar photovoltaic (SPV) plant through knock down analysis for the three major cell types monocrystalline silicon (C-Si), multicrystalline (M-Si) and amorphous silicon (A-Si). The highest efficiency achievable by a SPV cell is the Shockley-Queisser (SQ) limit which is the ultimate efficiency. When it comes to computing the working cell efficiency which can be treated as the SQ nominal conditions (after considering the cell losses) there is a drop. Moving up the organizational level, while at the module level, there is a further drop in the overall efficiency by 2-3 % points between the cell and the module. Further drop is seen when computing under Standard test conditions (STC) conditions and (PTC conditions PV-USA industrial test conditions). The STC module efficiency is taken as the reference or base condition for the SPV plant design. From the module to the array there is yet a drop of 3-4 % points. The performance drop of the plant from the STC conditions to the actually achieved conditions can be represented by the performance ratio (PR) which considers the stochastic efficiency of the plant site. The PR excludes excludes auxiliary power (2-4 % of the generated power), losses in battery (~20 %) due to storage component (if storage is present) and loss of energy generated due to non-availability of the grid (for grid tied systems). The stochastic incident radiation loss (~16-37 %) is already accounted in the PR. Automation helps to a large extent in tracking the component efficiencies and correcting the losses.

The paper also covers the sensitivity of SPV efficiency to positive factors such as incident angle variation, module tracking, Maximum Power Point Tracking (MPPT), concentration, etc., and negative factors such as environmental conditions (temperature, turbidity, water vapor), cell shunt resistance, initial and long term degradation, etc.

Keywords

Solar photovoltaic, system efficiency, SQ efficiency, performance ratio, cell efficiency, module efficiency, array efficiency, plant efficiency.

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M. Siddhartha Bhatt ¹

Affiliations
1 Energy Efficiency and Renewable Division, Central Power Research Institute, Bangalore-560 080, IN

Abstract

This paper presents the basic considerations for design of solar photovoltaic-wind-battery-grid connect hybrid power plants(HPPs). For ensuring the successful operation of hybrid power plants at low diesel input and low battery storage requirement, high level of reliability of power supply and reliability of component are essential. This paper provides factors involved in ensuring that high level of reliability of components and power availability is fulfilled in the hybrid plants. For both SPV and wind, the annual energy generation is divided into three regimes: summer, winter and rainy seasons and all these three have to fulfil the load requirement. It is seen that for 30% solar and 70 % wind generation curve is the smoothened with less variation.With improved day ahead predictability of both wind and solar the reliability can be improved considerably.

Keywords

solar photovoltaic, wind power, hybrid power plant, renewable power, high reliability, load smoothening

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H. S. Sudhakar ¹, M. S. Indira ², Gujjala B. Balaraju ³, M. Siddhartha Bhatt ⁴

Affiliations
1 Junior Research Fellow, EATD, Central Power Research Institute, Bangalore - 560080, IN
2 Principal, Sir M Visvesvaraya Institute of Technology, Bangalore - 562 157, IN
3 Electrical Appliances Technology Division, Central Power Research Institute, Bangalore - 560080, IN
4 Energy Efficiency and Renewable Energy Division, Central Power Research Institute, Bangalore - 560080, IN

Abstract

Battery is an electrochemical energy storage device that converts chemical energy into electricity, by use of a galvanic cell. The paper presents operation of lead acid battery, its chemical reactions and the charging methods to improve its performance and life span. The constant current charging mode results in overcharging of the battery as it is being pushed at full current. The constant voltage charging mode takes more time to charge the battery fully due to float charge, but the battery will not overcharge improving the life span. If the lead acid battery is undergoing deep discharge repeatedly then the life span of the battery will be less than its rated value. The operating temperature also has bearing on the life span. The paper is also presents the introduction to battery management system (BMS,) which is the heart of the battery system. The BMS involves a sophisticated supervisory control and data acquisition system (SCADA) with data management, control, protection and prediction.

Keywords

Valve regulated Lead Acid (VRLA), Ampere hour (Ah), constant current charging, constant voltage charging

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M. Siddhartha Bhatt ¹

Affiliations
1 Energy Efficiency & Renewable Energy Division, Central Power Research Institute, Bangalore-560080, IN

Abstract

This paper presents an overview of developments in steam turbines in general with particular application to match concentrating solar thermal (CST) sources.

The design of solar steam generator which has a parabolic output profile is first presented. Technologies for maintaining steady steam inflow into the steam turbine, viz., hybridization of sources like integrated solar combined cycle (ISCC) and thermal energy storage (TES), cogeneration, trigeneration, etc., are explored.

The developments in the steam turbine consist mainly of upgraded materials to operate at higher steam inlet temperature and pressure, ungraded energy efficiency through 3-dimensional computation fluid dynamics (CFD) design, increased fatigue life to withstand large number of cyclic operations, increased dynamic response and automation in manufacture. It is concluded that while 3-d designed steam turbines for elevated temperatures fulfill most requirements of CST power systems, fatigue life improvement and better energy efficiency at part load, needs to be addressed.

Keywords

Steam turbines, isentropic efficiency, 3-d blading, variable reaction blading, stage efficiency, energy efficiency.

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M. Siddhartha Bhatt ¹

Affiliations
1 Energy Efficiency & Renewable Energy Division, Central Power Research Institute, PO Box 8066, Sir CV Raman Road, Bangalore-560080, IN

Abstract

This paper presents a review of power grids which have high component (~ 80 %) of solar photovoltaic (SPV) plants. It can be concluded that variability or infirmness of SPV is controllable to a large extent through detailed probabilistic modeling of the variation patterns. The immediate, short term and long term variation of SPV power plants has been discussed in depth. In a grid composed of a large number of 1-50 MW plants, the dispatchable power can be scheduled to as high as 80 % of the declared capacity in that time slot (since SPV varies in every time slot).

Keywords

Solar photovoltaic, synchronous inertia, synthetic inertia, rate of change of frequency, governor droop, automatic generation control, primary response, secondary response.

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H. S. Sudhakar ¹, Gujjala B. Balaraju ¹, K. Pradeep ², M. Siddhartha Bhatt ²

Affiliations
1 Electrical Appliances Technology Division, Central Power Research Institute, Bangalore-560080, IN
2 Energy Efficiency and Renewable Energy Division, Central Power Research Institute, Bangalore-560080, IN

Abstract

Performance of a SPV system is dependent on temperature, array configuration, solar insolation, and shading across it. Shading can occur when the PV arrays/modules get covered by shadows of passing clouds, buildings, etc., or even by shadows cast by other modules/arrays. As a result the ideal operation of the PV systems is severely affected the P-V and I-V characteristics. The modeling of nonlinear current-voltage characteristics of solar cells for performance prediction becomes difficult under the influence of shading. Non-uniform solar radiation due to shadows casted by the other panels/ modules, buildings, clouds, etc. can cause maximum power to change drastically. Partial shading of PV installations has an impact on its power production. For the simulated results it has been observed that 74.66% loss in I-V characteristics and 85.41% loss in P-V characteristics respectively. The power losses in the individual shaded cells would result in local heating and create thermal stress on the entire module/array resulting in hot-spot formation.

Keywords

Maximum power point tracking (MPPT), Partial shading, Solar photovoltaic (SPV) characteristics.

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M. Siddhartha Bhatt ¹, S. Seetharamu ¹, N. Rajkumar ¹

Affiliations
1 Central Power Research Institute, Bangalore, IN

Abstract

This paper presents a methodology for assessment of annual heat rate of a coal fired thermal power unit based on a snap shot test to which various factors contributing to annual effects are added. This method is successfully used in a number of stations and represents the Unit Heat Rate (UHR) and Station Heat Rate (SHR) fairly well. This method is not a substitute for measurement of heat rate by direct measurement of coal flow and energy generated and is applicable only where direct measurement of coal flow into an individual boiler by gravimetric feeders or belt weighers is not available. This method is superior to other methods in view of its total coverage of all effects and no annual factor which affects heat rate is left out. Hence it is popularly accepted by most thermal stations. This method is superior to backward computation of UHR from SHR by apportioning.

Keywords

Coal Fired Station, Unit Heat Rate, Station Heat Rate, Coal Quality Effects, Heat Rate Degradation, Cycling Losses, Stacking Losses, Make Up Losses Central Power. Station Heat Rate, Coal Quality Effects, Heat Rate Degradation, Cycling Losses, Stacking Losses, Make Up Losses Central Power.

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U. C. Arunachala ¹, M. Siddhartha Bhatt ², L. K. Sreepathy ³

Affiliations
1 Dept. of Mech. Engg., Manipal Institute of Technology, Manipal - 576 104, IN
2 Central Power Research Institute, Bengaluru - 560 080, IN
3 Dept. of Mech. Engg., JNN College of Engineering, Shimoga - 577 204, IN

Abstract

Scale formation in risers of solar flat plate collectors is evident in places where hard water is being used. This affects both the component functioning as well as system performance. In this paper, the influence of scale deposition on instantaneous efficiency, mass flow rate and heat transfer rates are analysed by the Hottel-Whillier-Bliss (H-W-B) equation in both natural and forced circulation systems. It is observed that variation of mass flow rate affects collector efficiency more than variation of heat transfer rates.

Keywords

Solar Flat Plate Water Collector, Scaling, Hardness, Instantaneous Efficiency, Natural Circulation Systems, Forced Circulation Systems.

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M. Siddhartha Bhatt ¹, S. Jothibasu ¹

Affiliations
1 Energy Efficiency and Renewable Energy Division, Central Power Research Institute, Sir C V Raman Road, Bangalore-560080, IN

Abstract

Annual variation in water infl ow down to 50 % of its maximum value is quite common in run of the river hydro plants (with storage of 1–3 hours of power generation capacity) with multiple stations located on the same river in intervals of 30–50 km. The low capacity factors (< 40 %) call for effi cient water management for modulation of unit and station loads to co-ordinate operations and maximize energy generation. The effi ciency characteristics (which represent the utilization effi ciency of water resources) of the hydro units are not fl at but decrease with decrease in load. The net operating effi ciencies of individual hydro power plant units decrease sharply at lower loading levels below 80 % of the rated capacity due to swirling and vorticity components on one hand and erosion-cavitation on the other hand. The parameter (Pmin/Pmax) amongindividual units infl uences the net overall effi ciency to the tune of 2–10 % points in multi-turbine, multi-station environments of a river. By optimal selection of the loads to maximize this parameter, the energy generation can be maximized. The ultimate solution to optimal water utilization is to achieve a flat efficiency curve over the load range through 3-d designs of turbine runner. Silt control also plays a role in the energy effi ciency but is controllable and secondary.

Keywords

Water management, Hydro power plant, Run of the river plants, Multiple serial stations, Runner design and Plant efficiency.

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