SIZING OF ISOLATED HYBRID RENEWABLE POWER SYSTEM WITH DEMAND SIDE MANAGEMENT

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1 Proceedings of the International onference on Energy Resources and Technologies for Sustainable Development IERTSD 2013 Feb 7-9, 2013, Howrah, West Bengal, India SIZING OF ISOATED HYBRID RENEWABE POWER SYSTEM WITH DEMAND SIDE MANAGEMENT K.Aravind Kumar *, Suryanarayana Doolla, Rangan Banerjee Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai India * orresponding author aravindkumar@iitb.ac.in ABSTRAT Isolated hybrid power systems (Photo-Voltaic (PV) tery, PV-Diesel-tery, PV-Wind-diesel) provide an economical viable solution for end-use electrification of remote and rural area loads. For a given load profile, hybrid system design focuses on sizing the supply side components for desired reliability. The effect of demand side options on the end- use load profiles and its impact on hybrid power system sizing have not been investigated in literature. In this paper a methodology for sizing isolated hybrid systems considering demand side management (DSM) options with supply side alternatives is proposed and applied to a typical isolated village. End use electrification case study of a typical village using PV-tery with available demand side options is illustrated. Synthetic load profile based on typical village electricity end users (Residential, Agriculture and Street lighting), solar radiation on surface tilted at angle of latitude of location and different days of tery autonomy are considered as input to simulation algorithm developed in MATAB. An available DSM option of energy efficiency is utilized simultaneously with the supply side options for sizing the system. An acceptable feasible sizing solution in terms of ratings of hybrid system is achieved for cases of with and without DSM. Results show that the introduction of DSM reduces the daily consumption by 24% (20kWh) and peak by 21% (1.9kW) for a typical summer day. Daily consumption and peak of a typical winter day reduces by 18% (26 kwh) and 13% (1.1kW) respectively for DSM introduced. Reduced size of PV and tery by 28% and 24% respectively, are obtained for a desired reliability of 1% for 1.5 days of autonomy compared to without DSM case. Results indicate that the integration of DSM option can be considered as worthwhile option for sizing hybrid renewable power system Keywords: Isolated Hybrid power systems, oss of power supply probability, Demand side management, evelized cost of energy, Energy efficiency. 1. INTRODUTION In remote villages, far from the grids, electric energy is usually supplied by diesel generators. In most of these cases, the supply with diesel fuel becomes highly expensive while hybrid/photovoltaic/wind generation becomes competitive with diesel only generation [1].Photovoltaic/wind/diesel hybrid systems are more reliable in producing electricity than photovoltaic only/wind only systems, and often present the best solution for electrifying remote areas. Design of such hybrid system primarily focuses on sizing the supply side components for desired reliability. The sizing and optimization of autonomous renewable hybrid energy systems is more complex than that of single systems. This complexity is brought about by the use of at least two different resources together. Different sizing methods have been described in the literature. Simplest sizing methodologies can be those which are based in average values of weather variables [2], [3] or the worst scenario (e.g. the month with lower solar or wind availability); however, designs obtained by these methodologies trends to be oversized because of the worst case has a low occurrence probability or the average value is not a constant value all the time. Sizing methods in literature have considered analytical models, for single objective functions.in order to deal with the multi-objective functions, non-linear characteristic response of system s components, as well as long time series of weather variables, several mathematical tools have been proposed such as probabilistic approaches [4][5], artificial neural networks (ANNs) [6], genetic algorithms (GAs) [7] to mention a few. Most of the methods reviewed in the literature have described reliability of the system solely as supply side alternatives; integration of demand side options with supply side alternatives for sizing of the hybrid system has not been investigated. The paper proposes a methodology of sizing isolated hybrid power system IERTSD2013

2 utilizing the demand side options with supply side alternatives. The method proposed is illustrated for a simple case study of a typical village considering energy efficiency demand side option. 2. DEMAND ASSESMENT A typical village case study with residential loads, agricultural loads and community loads (Street lighting) is considered. Residential load typically consists of lighting, space cooling and entertainment loads. Agriculture load is primarily agriculture pump sets. ommunity demand is considered as street lighting loads. Usage pattern of the different loads of the typical village for two different seasons are illustrated in Table 1 to Table 5. Number of Households: 50 Table 1: Residential power consumption per Household for a summer day oads Wattage Incandescent W 480 bulb Fan W 520 Television W 240 Radio/music load W 50 onsumption (W-h/day) Table 2: Agriculture power consumption for summer day oad Motor & Pump loads Wattage 3 hp onsumptio n(kwh/day) Table 3: Street lighting power consumption for a summer & winter days. oad Wattage Incandescent bulb 100W onsumptio n(kwh/day) Table 5: Agriculture power consumption for a winter day oads Motor & Pump loads Watta ge 3 hp Synthetic load profile is generated, from the above usage pattern, considering the load aggregation for two different seasons of summer and winter as shown in Fig.1 and Fig DEMAND SIDE MANAGEMENT (DSM) onsumption (kwh/day) Demand side management is one of the ways of achieving the balance between the supply and the demand. Demand-Side Management (DSM) can be defined as the selection, planning, and implementation of measures intended to have an influence on the demand or customer-side of the electric meter, either caused directly or stimulated indirectly by the utility [9]. DSM programs are used to eliminate or reduce the need for additional peak or base load generating capacity and/or distribution facilities.dsm programs are a promising alternative strategy to the power utilities and government agencies, regarding global warming and carbon emissions. DSM objectives include Peak lipping, Valley Filling, load Shifting and Strategic onservation and Growth. A simple DSM objective of energy conservation is presented as an option with supply side for sizing of PV-tery hybrid system. Synthetic load profiles for typical village are generated for two different cases, ase 1 of replacing the 60W incandescent residential lighting loads by luminous equivalent 15 W F lamps, and ase 2 of replacing the energy inefficient ceiling fans by fans with 50W energy efficient fans. Modified load profile for summer and winter seasons obtained considering two cases is shown in Fig.1 and Fig.2. Table 4: Residential power consumption per Household for a winter day oads Tota l Wattage Incandescent W 480 bulb Television W 240 Radio load W 50 onsumption (W-h/day) Figure.1. Power consumption profile for a summer day IERTSD2013 2

3 where NOT is the normal operating cell temperature ( 0 ) and T a is the ambient temperature ( 0 ). Figure.2.Power consumption profile for a winter day 4. PV-HYBRID ONFIGURATION 4.2 Modeling of Battery system During any hour, the excess power generated by the PV generators can be utilized for charging the teries whereas the stored energy can be discharged whenever there is a deficiency in power generation. When the power generated, by PV array is insufficient and the storage is depleted, the load will not be satisfied. Therefore, the difference between total energy generated and load demand energy, decides whether tery is in charging or discharging state. During the charging process, the available tery bank capacity at the time t can be calculated as follows [8]: For the system configuration Fig.3 E ( t) t t E PV t ( ) ( 1) ( ) inv (4) During the discharging state, the storage tery capacity is computed as Figure.3.Schematic diagram of PV- tery storage In order to predict the hybrid system s performance, individual components should be modeled first and then their combination be evaluated to meet the desired reliability. PV generator and the tery components of the Fig. 3 are modeled as first step. 4.1 Photovoltaic generator Model The output power from a photovoltaic cell is given by P A G (1) g g g where P g, η g and A g represent the output power(wh),efficiency and Area of generator(m 2 ) respectively. G β represents the solar radiation (W/m 2 ) on a tilted surface. E ( t) t t E PV t ( ) ( 1) ( ) inv (5) where (t) represents state of charge of tery at time t,e and E PV reperesent the oad(wh) and the power generated from PV module(wh).η inv,η represent the efficiency of inverter and tery bank respectively. 5. Sizing of PV-tery hybrid system Solar radiation obtained for the tilted surface inclined at angle of latitude of the location is utilized in Eq. (1) considering the ambient temperatures of the location for 1 year. Efficiency of PV-generator is dependent on the temperature described by the relation g r pc[1 ( T c T ref )] (2) Where η r is the reference module efficiency, ηpc is the power conditioning efficiency, β is the generator efficient temperature coefficient, T ref is the reference cell temperature ( 0 ) and T c is the cell temperature given by Tc NOT 20 T a G 800 (3) Figure.4. Solar radiation (kw/m 2 ) on inclined surface for month of January. IERTSD2013 3

4 Reliability of the system is defined in terms of number of hours the power is not supplied to the load to the total number of hours, defined as loss of power supply probability (PSP). system required to achieve the desired reliability as shown in Fig.5. T PS( t) PSP t 1 T P t t t 1 ( ) (6) PS( t) P ( t) t ( P g ( t) ( t 1) min ) inv (7) Where PS (t) and P (t) represents oss of power supply and total power required at time t. For the desired reliability obtained, cost of electricity generated from the PV tery system is calculated as follows TA E E tot (8) Where E is the evelized cost of energy (Rs/kWh), TA the total annualized cost (Rs) or termed as annual life cycle cost and E tot is annual total energy supplied (kwh) by the PV-tery system. Annualized cost of system is sum of the apital, Maintenance, and Replacement cost. R N 1 1 d R (9) (10), R and M represent the apital cost,replacement cost and maintenance cost of the equipment. N, R represents the project life time and number of replacements of the equipment through project life time. Fig.5.illustrates the methodology of sizing the isolated hybrid system for desired reliability incorporating the detail end use load profiles. 6. RESUTS M N (1 d ) 1 N d (1 d ) End use electrification case study of a typical village using PV-tery with available demand side options is illustrated. Synthetic load profile based on typical village electricity end users (Residential, Agriculture and Street lighting), solar radiation on surface tilted at angle of latitude of location and different days of tery autonomy are considered as input to simulation algorithm developed in MATAB. State of charge of the tery and the power delivered from solar are used in calculating the ratings of hybrid Fig.5. Flow chart for calculation of PSP and cost of electricity generated Available demand side management options of energy efficiency are considered with replacement of 60 W incandescent bulbs with luminous equivalent 15 W F as case 1 and replacing the energy inefficient ceiling fans with 50W energy efficient fans as case 2. Simulation is run for two cases, one with actual load profile of the area and the other for case of modified load profile due to introduced DSM options. Introduction of DSM options reduces the daily consumption by 18 % (21kWh) and peak by 21 % (1.9kW) for a typical summer day for case 1as shown in Table.6. Daily consumption and peak of a typical winter day reduces by 18%(26kWh) and 13%(1.1kW) IERTSD2013 4

5 respectively for case 1as shown in Table 7.For case 2 reduction in peak and the daily demand is predominantly observed in summer (Table.10) compared to winter days since the cooling load in winter is assumed non operating. Table 6: Demand of typical summer day for case1 Daily demand(kwh) Average(kW) Peak(kW) Table 7: Demand of typical winter day for case1 Daily demand(kwh) Average(kW) Peak(kW) Table 8: Ratings of PV for different PSP for case 1 Desired PSP (kw) (kw) 1% % % % % Table 9: Ratings of tery for 1% PSP for case 1 Desired PSP Without With DSM(kWh) DSM(kWh) 1% Table 10: Demand of typical summer day for case2 Daily demand(kwh) Average(kW) Peak(kW) Table 12: Ratings of tery for 1% PSP for case 2 Desired PSP Without With DSM(kWh) DSM(kWh) 1% Table 13: Demand of typical summer day for combined case1 & case2 Daily demand(kwh) Average(kW) Peak(kW) Table 14: Demand of typical winter day for combined case1 & case2 Daily demand(kwh) Average(kW) Peak(kW) Table 15: Ratings of PV for different PSP for combined case1 & case 2 Desired PSP Without (kw) DSM(kW) 1% % % % % Table 16: Ratings of tery for 1% PSP for combined case1 &case 2 Desired PSP Without With DSM(kWh) DSM(kWh) 1% Table 11: Ratings of PV for different PSP for case 2 Desired PSP Without (kw) DSM(kW) 1% % % % Figure.6. Ratings of PV for different PSP. IERTSD2013 5

6 REFERENES Figure.7. ife cycle cost of PV-tery system for different PSP. Figure.8. Annual ife cycle cost of PV-tery system for different PSP. Introduced energy efficiency DSM, results in a reduction of required PV rating by 28% and tery by 24% (Table.15) as compared to the without DSM for a desired reliability of 1% for 1.5 days of autonomy, shown in Fig.6.ost of replacement with energy efficiency lightning and ceiling fan is considered in the life cycle cost without the subsidy. Reduced life cycle cost of the system is observed (Fig.7) with demand side option introduced compared to without DSM case. Reduced annual life cycle cost for introduced DSM option is observed (Fig.8) for different reliability levels, thereby influencing the cost of electricity generated (Rs/kWh). 7. ONUSIONS Isolated hybrid power system components are sized utilizing the demand side option simultaneously with supply side options, the method illustrated for a simple typical village case study. Energy efficient DSM option has been considered for a preliminary approach in the methodology. An acceptable feasible sizing solution in terms of rating of PV and tery is obtained. 1. Nouni, M.R, Mullick, S.. and Kandpal, T., 2008, Providing electricity access to remote areas in India: An approach towards identifying potential areas for decentralized electricity supply, Renewable and Sustainable Energy Reviews, 12: elik, A.N., 2002, The system performance of autonomous photovoltaic wind hybrid energy systems using synthetically generated weather data, Renewable Energy, 27: Protogeropoulos,., Brinkworth, B.J. and Marshall, R., 2006, Sizing and techno-economical optimization for hybrid solar PV wind power systems with tery storage, International Journal of Energy Research, 21 (6): Tina, G., Gagliano, S. and Raiti, S., 2006, Hybrid solar/wind power system probabilistic modeling for long-term performance assessment, Solar Energy, 80(5): Yang, H.X., Burnett,. and u, J., 2003, Weather data and probability analysis of hybrid photovoltaic wind power generation systems in Hong Kong, Renewable Energy, 28: Mellit, A. and Pavan, A.M., 2010, Performance prediction of 20 kwp grid connected photovoltaic plant at Trieste (Italy) using artificial neural network, Energy onversion and Management, 51 (12): Dufo-o pez, R.. and Bernal-Agustı n, J.., 2005, Design and control strategies of PV diesel systems using genetic algorithms, Solar Energy, 79 (1): Diaf, S., Notton, G., Belhamel, M., Haddadi, M. and ouche, A., 2008, Design and techno-economical optimization for hybrid PV/wind system under various meteorological conditions, Applied Energy, 85(10): GoranStrbac, 2008, Demand side management: Benefits and challenges, Energy Policy, 36: Appendix Technical specifications of PV Module Type Pmp (W) Imp (A) Vmp (V) BP % η Ref. Temp ( o ) NOT ( o ) Asc (m 2 ) IERTSD2013 6

7 Technical specifications of Battery and Inverter Depth of discharge of tery (DOD) 0.4 harging efficiency of tery (η ch ) 0.95 Discharging efficiency of tery (η dch ) 1.0 Efficiency of tery (η b ) 0.9 Efficiency of inverter (η inv ) 0.92 ost specifications of PV-Battery system ost of PV generator in Rs/kW 75,000 ost of installation of PV in Rs/kW 30,000 ost of tery in Rs/kWh 6000 ost of bidirectional inverter(rs/kw) 12,500 Maintenance of PV 1% of price for 1 st 535 year(rs/kw) Maintenance of inverter 3% of 375 price(rs/kw) Project ife time (years) 20 Interest on capital 10% IERTSD2013 7