Current World Environment

Introduction

Photovoltaic (PV) energy production is recognized as an important part of the future energy generation mix.¹ Because it is non-polluting, free in its availability, and is of high reliability. Therefore, these facts make the PV energy resource attractive for many applications, especially in rural and remote areas of most of the developing countries.²

India lies in the sunny belt of the world. The scope for generating power and thermal applications using solar energy is huge. Most parts of India get 300 days of sunshine a year, which makes the country a very promising place for solar energy utilization.³ The daily average solar energy incident over India varies from 4 to 7 kW h/m² with the sunshine hours ranging between 2300 and 3200 per year, depending upon location.⁴ The technical potential of solar energy in India is huge. The country receives enough solar energy to generate more than 500,000 TW h per year of electricity, assuming 10% conversion efficiency for PV modules. It is three orders of magnitude greater than the likely electricity demand for India by the year 2015.

This paper presents a study on the design and economical analysis of a stand-alone PV system to provide the required electrical energy for a single residential household in India. The Indian location selected is Delhi.

The household pv system configuration

Fig. (1) shows the suggested block diagram of the household stand-alone PV system. Where, the function of the PV array is to convert the sunlight directly into DC electrical power and that of the battery is to store the excess power through using the battery charger. The inverter is used to convert the DC electrical power into AC power; to match the requirements of the common household AC appliances.
 

Figure 1: The stand-alone PV system Click here to view figure

Site meteorological data

To predict the performance of a PV system in a site, it is necessary to collect the meteorological or environmental data for the site location under consideration. Indian Meteorological Department, Pune⁵ is a good source for these data. The monthly average daily solar radiation data incident on horizontal plane of the site is shown in Fig. (2). It is clear from the figure that solar energy incident in the considered site is very high especially during the summer months, where it reaches 7 kWh/m²/ day on horizontal plane.
 

Figure 2: Monthly average daily global radiation on a horizontal surface at Delhi Click here to view figure

average daily solar radiation data incident on horizontal plane of the site is shown in Fig. (2). It is clear from the figure that solar energy incident in the considered site is very high especially during the summer months, where it reaches 7 kWh/m²/ day on horizontal plane.

PV System Design

To design a stand-alone PV system for the considered household, the following steps are required.

The Average Daily Solar Energy Input

Fig. (2) can be used to calculate the average daily solar energy input over the year (G_av) on a south facing surface tilted at an angle equal to the site latitude to be about 6.62 kWh/m²/day.

The Average Daily Load Demand

The average daily load demand E_L can be calculated from Fig. (3), to be 5500 Wh/day.
 

Figure 3: The load profile of the household Click here to view figure

Sizing of the PV Array

The size of the PV array, used in this study, can be calculated by the following equation [6]:

                            ...(1)

Where

G_av is average solar energy input per day TCF is temperature correction factor _PV is PV efficiency 

_out is battery efficiency ( ) ´inverter efficiency ( _Inv )

If the cell temperature is assumed to reach 60 ^oC in the field, then the temperature correction factor (TCF) will be 0.8 as indicated in [7]. Assuming = 12% and = 0.85×0.9 = 0.765. Thus, using Eq. (1) the PV area is 11.3 m².

The PV peak power, at peak solar insolation (PSI) of 1000 W/m², is thus given by [7, 8]:

                               ...(2)

The selected modules are mono-crystalline silicon, with the following specifications at standard test conditions (i.e., 1000 W/m² and 25 ^oC)

• Peak power: 23.2 W_P
• Peak-power voltage: 9.6 V
• Peak-power current: 2.4167 A

Table 1: The Household Load Data Click here to view table

The storage capacity of the battery can be calculated according to the following relation [8, 9]:

                                     ...(3)

Table 2: The Used Cost Data of All Items Click here to view table

• The initial cost of the system (the capital cost) is high.
• There are no fuel costs.
• Maintenance costs are low.
• Replacement costs are low (mainly for batteries).

The LCC of the PV system includes the sum of all the present worths (PWs) of the costs of the PV modules, storage batteries, battery charger, inverter, the cost of the installation, and the maintenance and operation cost (M&O) of the system. The details of the used cost data for all items are shown in Table 2 [7, 12-14].

The lifetime N of all the items is considered to be 20 years, except that of the battery which is considered to be 5 years. Thus, an extra 3 groups of batteries (each of 6 batteries) have to be purchased, after 5 years, 10 years, and 15 years, assuming an inflation rate i of 3% and a discount or interest rate d of 10%. Therefore, the PWs of all the items can be calculated as follows [10, 11]:

• PV array cost CPV = 5×60×23.2 = $6960
• Initial cost of batteries CB = 1.705 ´ 1500 = $2557.5
• The PW of the 1st extra group of batteries (purchased after N = 5 years) C_B1PW can be calculated, to be $1840.93, from
   

• The PW of the 2nd extra group of batteries (purchased after N = 10 years) C_B2PW and that of the 3rd extra group (purchased after N = 15 years) C_B3PW are calculated, using Eq. (4), to be $1325.14 & $953.86, respectively.
• Charger cost C_C = 5.878 ´ 50 = $293.9
• Inverter cost C_Inv = 0.831 ´ 1020 = $847.62
• Installation cost C_Inst = 0.1 ´ 6960 = $696
• The PW of the maintenance cost C_MPW can be calculated to be $1498.35, using the maintenance cost per year (M/yr) and the lifetime of the system (N = 20 years), from [12];
   

                                     ...(5)


Therefore, the LCC of the system can be calculated, to be $16973.3, from: 

     ...(6)

It is sometimes useful to calculate the LCC of a system on an annual basis. The annualized LCC (ALCC) of the PV system in terms of the present day dollars can be calculated, to be $1476.51/yr, from [9,10]:
​​​​​
                                           ...(7)

Once the ALCC is known, the unit electrical cost (cost of 1 kWh) can be calculated, to be $0.74/ kWh, from;

                                         ...(8)

Therefore, in remote sites that are too far from the Indian power grid, the PV installers are encouraged to sell the electricity of their PV systems at a price not lower than $0.74/kWh to earn a profit. It is to be noted, here, that although this price is very high compared to the current unit cost of electricity in India ($0.1/kWh), this price will drop to $0.49/kWh if the future initial cost of the PV modules drops to $0.1/W_P. At the same time, if the future unit cost of electricity in India becomes five times its current value, due to the rapid increase in the conventional fuel prices, therefore PV energy generation will be promising in the future household electrification (in India) due to its expected future lower unit electricity cost, efficiency increase, and clean energy generation compared to the conventional utility grid.

Conclusion

Electrification of remote and rural sites worldwide is very important especially in the developing countries like India. The photovoltaic systems are considered as the most promising energy sources for these sites, due to their high reliability and safety. They represent, at the same time, a vital and economic alternative to the conventional energy generators. An electrification study for a single residential household in a remote rural site of India is carried out using a stand-alone PV system. This study presents the complete design and the life cycle cost analysis of the PV system. The results of the study indicate that electrifying a remote rural household using PV systems is beneficial and suitable for long-term investments, especially if the initial prices of the PV systems are decreased and their efficiencies are increased.

References
 

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