Optimization and Modeling of PV/ FC/Battery Hybrid Power Plant for Standalone Application

Optimization and Modeling of PV/ FC/Battery Hybrid Power Plant for Standalone Application

Debika Debnath*

Deptt. of Electrical Engineering

NIT, Agartala,

West Tripura- 799055, India

Dr. Ajoy Kumar Chakraborty

Deptt. of Electrical Engineering

NIT, Agartala

West Tripura- 799055, India

Dr. Srimanta Ray

Deptt. of Chemical Engineering

NIT, Agartala,

West Tripura- 799055, India

Abstract

The hybrid system of renewable energy can contribute in a significant way of the durable development of several isolated areas far away from the main utility grid. In this paper, a hybrid power generation system suitable for remote area for agricultural application is proposed. This system consists of a renewable energy sources namely photo-voltaic panels. The climate change which is one of the greatest challenges which must be mak e possible for the supply of these isolated areas with their needs of electricity by

renewable energy sources. For that fuel cell used as auxiliary source and combined with PV system can ensure a reliable supply without interruptions. For the production and uniform supply of hydrogen of fuel cell, an electrolyzer is considered in the proposed system. Also it consists of a battery. The main power of the hybrid system comes from the photovoltaic panels, while the fuel cell and batteries are used as back up units. The analysis of such a hybrid system feeding a load centre is carried out with the application of HOMER so ftware. HOM ER is a design model that determines the optimal architecture and control strategy

of the hybrid system. Based on simulation results, it has been found that these renewable energy sources would be a feasible solution for distributed generation of electric power for stand-alone application at remote location.

1.Introduction

Many villages in the world live in isolated areas far from the main utility grid. Despite rapid industrialization, agricu lture forms a ma jor contributor to the Indian economy. With the economy progressing and a lot of mechanization being done in agricultural practices, the demand of electric ity a mong this segment has also increased. It is rea lly responsible their meet by the conventional sources because of the high cost of transport and the distribution of energy to this re mote areas. Currently, the electric provisioning of these sectors is done by the hybrid system of production of electricity. This hybrid system consists of the combination of diffe rent energy sources like photovoltaic, fuel cell and battery [1]. A system of the combination of diffe rent energy sources has the advantage of the

balance and stability [2]. The concept of photovoltaic is well understood and currently thousands of PV based power systems are being deployed worldwide, for providing power to small, re mote and grid independent applications [3]. In addition to this , use of renewable energy sources reduces combustion of fossil fuels and the consequent CO2 e missions.

Despite abundant availability of solar, a PV standalone system cannot satisfy the loads on a 24 hours basis. Often, the variations of solar energy generation do not match the time distribution of the load. Therefore, the use of fuel cell with PV ensures the availability of power during the 24 hours [4]. The electroly zer converts the excess generation of PV as hydrogen and stores in hydrogen tank. Fuel cell uses this hydrogen and convert is to the electricity. Fuel ce ll will operate only when the PV is inactive. PV generated electric ity also stored in batteries also.

National Renewable Energy Laboratorys (NREL) Hybrid Optimization for Electric Renewable (HOM ER) software has been employed to carry out the present study. HOMER is a computer model that simplifies the task of evaluating design options for both off-grid and grid connected power systems for re mote, stand-alone and distributed

generation (DG) applications. It is developed specially to meet the needs of renewable energy industrys system analysis and optimization.

Inputs to HOM ER will perform an hourly simu lation of every poss ible combination of components entered and rank the system according to user specified criteria, such as cost of energy(COE,US$/KWh) or capital costs. Furthermore, HOM ER can perform sensitivity analysis in which the values of certain para meters (e.g. solar radiation, prima ry load) are varied to determine their impact on the

2.1. Solar Radiation and PV Cost Inputs

With the latitude and longitude HOM ER software can automatically collected the global solar rate for the place. The average solar radiation is 5.389 kWh/m2/d. The site is located at (GMT+5.30) zone. The init ial size of PV array used for this project is 80 kW. Price for the capacity is retained at $7000 and replacement cost is also $7000. Diffe rent PV a zimuths have been set for a lifetime of 20 years [9].

system configuration [4].

In this paper the simulat ion of a hybrid energy system composed of PV generator together with FC and battery storage has performed and a power management strategy has

7 Global Horizontal Radiation

Daily Radiation (kWh/m²/d)

6

5

4

3

2

1

1.0

Clearness Index

0.8

0.6

0.4

0.2

designed. Finally the simulat ion result and discussion has presented.

2. System Description

On the design point of view, the optimization of the size of hybrid plants is very important and leads to a good ratio between cost and performances. Before the system sizing, load profile and available insolation should be evaluated. Therefore, they are presented in the following sections:

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0.0 Daily Radiation Clearness Index

Figure 1. Monthly average solar radiation

2.2 Load Profile

An important consideration of any power generating system is load. As a case study this system is utilized in an agricultural (irrigation) applicat ion. The measured annual average energy consumption has been considered

to scale the load 140 kWh/d in the present study. The daily average load profile is shown in Figure 2. With added consideration for demand variat ion of 2.2% day-to- day and hour-to hour, the peak load is estimated to be 13 kW [10].

10 Daily Profile

Load (kW)

8

6

4

2

0

0 6 12 18 24

Hour

Figure 2. Daily load profile

3. HOMER Simulation

In this present work, the selection and sizing of components of hybrid power system has been done using NRELs HOM ER software. HOM ER is the general purpose hybrid system design software that facilitates design of electric power systems for stand-alone applications. Input informat ion to be provided to HOM ER includes: electrica l loads, renewable sources, component technical details and costs, constraints, controls, type of dispatch strategy etc. HOMER designs an optima l power system to serve the desired loads.

HOM ER is a simp lified optimization model, wh ich performs hundreds or thousands of hourly simulat ions over and over in order to design the optimu m system. It uses life cycle cost to rank order these systems.

The model has been developed using HOM ER, consists of a PV, a battery and a FC fed by hydrogen. The schematic of this hybrid power system is shown in Figure 3.In order to verify the system performance under diffe rent situations, simulat ion studies have been carried out using real weather data (solar irradiance).The goal of the optimizat ion process is to determine the optimal vale of each decision variable that interests the modele r. A design variable is a variable over which the system designer has control and for which HOM ER can consider of mult iple possible values in its optimizat ion process. In this study decision variable in HOM ER inc lude:

The size of the PV array The size of FC

The capacity of batteries The size of DC/AC converter

The size of electroly zer

and hydrogen tank

3.1 Power Management Strategy

The dispatch strategy is load following type and interaction between different co mponents is as follows:

In norma l operation, PV feed the load demand. The e xcess energy fro m PV is stored in the battery until the full capacity of the battery is reached. The main purpose of introducing battery storage is to import/e xport energy depending upon the situations. In the event, the output of PV e xceeds the load, and the batteries state of charge (SOC) is ma ximu m, the e xcess energy is fed to electro lyze r. The FC is bought into the line when PV fail to satisfy the load and the battery storage is depleted(i.e. when the batterys SOC is minimu m) [5].The details of proposed hybrid system components can be found in table I[10] and the flow chat of this project is also shown in Figure 4 [8].

Figure 3. Proposed system configuration in HOM ER

Figure 4. Flow chart of the project

Table I. Technical data and study of assumptions components

presented in Table II. The first column shows the presence of PV modules, FC and Battery in hybrid system. It can be noticed fro m these results that the first system consists of PV/FC is the most comme rcia l but in this paper the result of the second configuration has considered because of presence of all co mponents.

The COE of hybrid PV /FC/ Battery

/Electroly zer system(80kW PV,10kW FC, Battery and hydrogen storage,0.01% annual capacity shortage) has been found to be is 0.431 (US$/ kWh).

Average Value (kW)

120

90

60

30

0

PV Array Power Output Monthly Averages

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann

Month

max

daily high mean

daily low min

Figure 5. Powers evolutions during 24 hours

4. Simulation Results

Several simu lations have been made by considering diffe rent PV capacities. The PV capacity has been allowed to vary from 0 to 160 kW. The FC powe r considered to change from 0 to 10 kW. The simu lation results for 5.389 (kWh/m2/d) solar rad iations are

100

Average Value (%)

90

80

70

60

50

40

30

Battery State of Charge Monthly Averages

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann

Month

Figure 6. Battery SOC Monthly Averages

max

daily high mean

daily low min

Average Value (kg)

80 Stored Hydrogen Monthly Averages

60

40

20

max

daily high mean

daily low min

0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann

Month

Figure 7. Stored Hydrogen Monthly Averages

Table II. Annual Electric Energy Production

Table III. Annual Electric Energy Consumption

Table IV. Annual Emissi ons

In the proposed hybrid system the unmet load is 120 (kWh/yr). It can be depicted from Figure 8 the variation of PV capacity with solar radiation and primary load. Figure

9 shows the monthly average electrica l production.

5. Cost Optimization

The aim of this study is to achieve a stand-alone hybrid generation system, which should be appropriately designed in terms of economic, reliability and environmental measures subject to physical and operational constraints/strategies [6, 7, 10].

The system cost is defined as sum of PV cost(CPV),battery cost(CBAT),e lectroly zer

cost(C ),FC cost(C

),converter 25

Monthly Average Electric Production

PV

ELEC FC

Fuel Cell

Power (kW)

cost(CCONV) and hydrogen tank 20

15

cost(CTANK).

10

5

The cost for each ele ment should be deducted:

i=PV, Battery, FC, Electro lyze r, Converter, Hydrogen Tank

Where Ni is the number/size of the system component, CCosti is the capital cost, RCosti is the replace ment cost, Ki is the number of replace ment and OMCosti is operation and maintenance cost through the system operation. The cash flow of the sys tem ele ments can be seen in Figure 10.The cost of the system ele ments can be seen in Figure 11.

5.60

PV Array Capacity

Legend

100 kW

98

0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 9. Monthly Average Electric Production

The simu lation results indicated that a hybrid power system comprising of a 80 kW photovoltaic system together with a 10 kW fuel cell would be a feasible solution for distributed generation of electric power for stand-alone applications at re mote locations.

The cost of generating energy from the above hybrid PV/FC/ Battery system has been found to be 0.431(US$/ kWh). The hybrid

Global Solar (kWh/m²/d)

5.55

5.50

5.45

5.40

96

94

92

90

88

86

84

82

80

Fixed

PV Azimuth = 0 deg FC Capital Multiplier = 1

PV/FC/ Battery power system offers several benefits such as: utilizat ion rate of PV, FC and battery can occur. The environ mental friendly nature of the hybrid system can

140 145 150 155 160

Prim ary Load (kWh/d)

Figure 8. PV array capacity

also be depicted from annual emission of the system.

100,000 Cash Flows

50,000

Nominal Cash Flow ($)

0

-50,000

-100,000

-150,000

-200,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Year Num ber

Figure 10. Cash Flow Summary

PV

Fuel Cell Trojan T-105 Converter Electrolyzer Hydrogen Tank Other

1. R. Chedid, H. Akiki, and S. Rahman, A Decision Support Technique for the Design of Hybrid Solar- Wind Power Systems, IEEE Trans. on Energy Conversion, vol. 13, No. 1, M ar. 1998.

2. National Renewable Energy Laboratory [Online]. Available:http://www.nrel.gov/inter national/tools/HOM ER/homer.html.

   100,000

   Net Present Cost ($)

   80,000

   60,000

   40,000

   20,000

   0

   Cash Flow Summary

   PV

   Fuel Cell Trojan T-105 Converter Electrolyzer Hydrogen Tank Other

3. A. Jalilvand, H. Kord, and A. Rohani, Design, Control and Power M anagement of a Hybrid PV/WG/FC System for Stand Alone Applications, Electrical Power Distribution Conference

PV FC Trojan T-105 Converter Electr. H2 Tank Other

Figure 11. Cost Analysi s of Configuration

7. References

1. Souissi Ahmed, Hasnaoui Othman, Sallami Anis, Optimal Sizing of a Hybrid System of Renewable Energy for a Reliable Load Supply without Interruption, European Journal of Scientific Research. vol.45, No.4, 2010, pp.620-629.

2. R. Ramakumar, I. Abouzahr, and K. Ashenayi, A Knowledge-Based Approach to the Design of Integrated Renewable Energy Systems, IEEE Trans. on Energy Conversion, vol. 7, No. 4, Dec. 1992.

(EPDC),Kerman, 2009.

1. S. Jalizadeh, A. Rohani, H. Kord and M . Nemati, Optimum design of a hybrid Photovoltaic/Fuel Cell energy system, for standalone applications, IEEE Int. Conf. on Electrical Engineering, and Electronics (ECTI),vol. 1, Thailand, May 2009, pp.152-155.

2. H. Kord, A. Rohani, An Integrated Hybrid Power Supply for Off-Grid Applications Fed by

   Wind/Photovoltaic/Fuel Cell Energy Systems, 24th Int. Power System Conference (PSC), Tehran,

   Nov. 2009,pp.1-11

3. M ohammad Saad Alam, David W. Gao, M odeling and Analysis of a Wind/PV/Fuel Cell Hybrid Power System in HOM ER, 2007 Second Conference on Industrial Electronics and Applications, pp:1594-1599.

4. M . Shakawat, Hossan, M . M Aruf Hossain, A.R.M Reazul Haque, Optimization and M odeling of a Hybrid Energy System for off-grid Electrification, IEEE Int. Conf. 2011.

5. Ahmed Rohani, Kazem M azlumi, Hossein Kord, M odeling of a hybrid Power System for Economic Analysis and Environmental Impact in HOM ER, proceedings of ICEE 2010,May 11-13,2010.