The thermal power plants generate major part (approximate 65%) of the total energy produced in India. However, it has become urgent need to switch over from fossil fuel based generation to the renewable sources based generation considering the environmental aspect and sustainable future. Among the renewable generations, the solar energy is most promising but due to the land availability issue the roof top PV (RTPV) system gained the popularity. In this paper, the techno economic feasibility study of the off grid RTPV system is analyzed. Moreover, the environmental benefit is also highlighted by showing the emission reduction of 102.45 tons considering 25 year life cycle period. The financial benefit is discussed through the simple payback period which is found around 8 year considering a typical case study. Furthermore, the technical parameters related to the off grid RTPV system are also discussed. This study will be helpful to the utility and planners for possible adoption of the off grid solar PV system in residential as well as commercial building.
guideline to the electricity consumers, factories small and medium utilities for possible adoption of the RTPV technology.
The PV modules are installed on the roof top of the buildings. It is possible to become self-reliant if the PV panels are installed by proper matching the electrical load. The off grid RTPV system is composed of the components like PV modules, solar charge controller, battery bank, inverter etc.It is very interesting to note that major portion of India receives good irradiation throughout the years. On an average, 7 hr per day the good irradiation is received. The annual average monthly irradiation in Kolkata, West Bengal, India (Latitude: 22.55; Longitude: 88.35) irradiation is 4.12 KWh/m2/day. The 58% land of India receives average irradiance of 5 KWh/m2/day [2]. Therefore, India has huge potential of solar radiation and this potential can be used effectively through RTPV system. In order to promote the solar energy, the Government of India (GOI) has come up with different incentives and schemes so that the customers as well as different companies feel interested to take up the RTPV project. Some important schemes i.e., Net Metering Policy, Fed in Tariff, Renewable Purchase Obligation (RPO) etc. are introduced for encouraging the use of solar energy. It is worth noting that GOI has set the aim to meet 40 GW roof top solar energy from total 100 GW. The year wise capacity addition of solar energy is represented in Fig.1 [2]. The huge growth in solar energy has been observed since last few years. The growth in solar energy in Indian market is displayed in Fig.2.
It is essential to find out the required technical parameters for installation of the RTPV system. In this section, the methodology for finding out the general technical parameters of the RTPV system is described. We cover both the technical as well as economic aspect. The technical parameters associated with RTPV system are number of PV panels, number of batteries, size of the inverter, size of the charge controller etc. All these parameters are evaluated one by one in this section. The methodology presented in this work is based on the concept described in [3].At first, we must know the total energy consumption of the system for which the design parameters are to be evaluated. 3.1.
The total energy consumption can be computed using following expression ℎ type equipment. Therefore, the total required PV generation can be computed as Here represents the category of load (fan, lights etc.). The represents the number of hours/day equipment type-k is used, denotes the rated power of k-th device, represents the number of − = ∑ =1
1000 ( ) KWH =
( ∗ )
KW Here, and
represent the days for which the backup power required, and the battery voltage rating respectively. Moreover, ℎ denotes the ampere-hour of the battery and the depth of discharge of Now, we have to find the size of the inverter which basically depends on the peak load . Further, the peak load is can be obtained from the diversity factor (DF) and connected system load. The DF is defined as follows = /
Here
denotes the capacity of each PV module. 3.2.
Now, the number of batteries
can be calculated by = ( ∗ )/( ∗ ℎ ∗ ) the battery is denoted by DOD. 3.3.
Inverter Sizing ∑ = =1 Pini
DF Therefore, the size of the inverter can be expressed as the required number of PV panels can be computed as follows Here, represents the number of hours the solar radiation received, D represents the de-rating factor. We consider the value of 7 hours (in West Bengal). Further, we assume 80% derating factor. Now, (1) (2) (3) (4) (5) (6)
Where respectively.
and
represent the total cost of battery and total cost of PV panels = ∗ (9) = ∗ (10) It is interesting to note that the Government is promoting the RTPV system by providing subsidy so that the utilities and customers are encouraged. The different organizations, Government bodies [4] and Ministries [5] are associated with the promotion of solar energy in India. It is worth noting that 30% subsidy can be availed from National Clean Energy Fund (NCEF). The subsidy is disbursed in the following way: • • •
On completion of the installation and commissioning of the RTPV system, 20% subsidy is provided As soon as the operation of the project starts, another 5% subsidy is disbursed
On completion of the two years successful operation, the rest 5 % subsidy is allocated Considering government subsidy (Qsubsidy ) the total cost of the RTPV system ℎ can be written as ℎ = (1 − ) ∗ ( / ) (11)
Where = ∗ and = ∗ .
Now, the overall profit that can be achieved through RTPV system is
= − ℎ (12) The others benefits of RTPV system includes independency on grid power. Nowadays, frequent power cut is observed in the rural areas due to peak deficit. In this context, the RTPV system will be very fruitful for reliable supply of electricity. In order to find the economic benefit, the simple payback period is to be calculated. The simple payback period can be expressed as
In this section the economic aspect of RTPV system is described. The aim of this section is to measure the profit and quantity the economic benefit of the RTPV system.
Let and ℎ represent the cost of grid power, and cost of RTPV system taking subsidy into account. Now, assume the lifetime of RTPV system is years, and per unit energy charge imposed by utility is . Now, the total cost of the power taken from the grid may be expressed as = 365 ∗ ∗ ∗ (7) Considering four main components such as battery, inverter, PV panel and controller, the total cost of the RTPV system without subsidy ( / ) may be expressed as / = ( + + + )
ℎ 365(
) 3.5.
= 0.82( )365 ∗ 25 t/MWh
1000 Environmental impact is one of the major concern considering the future generation. In this context, the considerable emission reduction can be achieved through RTPV system. However, a proper baseline is required in this regard to quantify the amount of emission reduction. The standard emission data is provided by Central Electricity Authority (CEA). In this context, the emission factor for thermal generating units is 0.82 Tons of CO2 per MWh of energy according to the CEA guideline [6]. Based on this concept, we can calculate the reduction of CO2 emission for 25 years period as follows (14) (8) (13)
A typical composite house building is chosen for case study purpose. The load distribution of the house building is demonstrated in Table 1. We have considered the cost of battery Rs. 14500 per battery [7] and the cost of inverter Rs. 38000 [8]. The cost of the 330 watt PV module is assumed to be Rs. 9199 per module [9]. The techno economic evaluation of the case study is illustrated in Table 2.
Total amount of CO2 emission reduction (25 40% 199914.4
In this study, the techno economic feasibility analysis of RTPV system is nicely presented. The different technical aspects like number of PV panels, number of batteries, inverter size etc. are highlighted. Moreover, the economic aspect of installing RTPV system is also outlined. A typical case study of house building considering total energy consumption of 13.692 KWh is also conducted to check the financial benefit of the monetary investment on the RTPV project. It has been observed that the simple payback period is around 8 years and 102.45 ton reduction of CO2 emission can be achieved. Therefore, the presented work will be helpful to the customers, utilities, designer etc. for successful implementation of the RTPV project. Furthermore, the Government is promoting the RTPV project by providing the subsidies to the capital investment. Additionally, the land availability issue is a major concern due to which the traditional PV projects (PV panels mounted on land) are losing the attraction of the investors due to complication arises during land acquisition. In this context, this is the high time to avail the subsidies by implementing the RTPV project. Thus, the dependency on the conventional grid power can be avoided and the sustainable future can be ensured. It is worth noting that few aspects such as partial shading, weather variability, environmental hazards etc. have the impact on performance of RTPV. Although, some government policies are introduced for promoting the solar energy, 100% proper implementation could not be possible due to regulatory obstacles. Therefore, it is urgent need for the government to introduce flexible policies or schemes so that they can be adopted at large scale easily. 6. References [1]. T. Ma, H. Yang, L. Lu, “Performance evaluation of a standalone photovoltaic system on an isolated island in Hong Kong.”Appl. Energy vol. 112, pp. 663–672, 2013 [2]. Dawn et al. “Recent developments of solar energy in India: Perspectives, strategies and future goals” Renewable and Sustainable Energy Reviews, vol. 62, pp 215-235, 2016 [3]. P. Sharma, H. Bojja and P. Yemula, "Techno-economic analysis of off-grid rooftop solar PV system," 2016 IEEE 6th International Conference on Power Systems (ICPS), New Delhi, 2016, pp. 1-5, doi: 10.1109/ICPES.2016.7584208. [4]. Solar Energy Corporation of India (SECI), https://www.seci.co.in/ [5]. Ministry of New and Renewable Energy (MNRE), https://mnre.gov.in/ [6]. CEA CO2 Baseline Database for the Indian Power Sector [online]
Available:http://cea.nic.in/reports/others/thermal/tpece/cdm_co2/user_guide_ver10.pdf/. [7]. Battery cost available at https://www.luminousindia.com/shop-now/batteries [8]. Inverter cost available at https://www.luminousindia.com/shop-now/home-ups-inverter/allinverters.html [9]. PV module cost online available at https://www.luminousindia.com/solar-products/solar-pvpanel.html