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International Journal of Electrical Engineering & Technology (IJEET) Volume 8, Issue 2, March- April 2017, pp. 81–92, Article ID: IJEET_08_02_010 Available online at http://www.iaeme.com/IJEET/issues.asp?JType=IJEET&VType=8&IType=2 ISSN Print: 0976-6545 and ISSN Online: 0976-6553 Journal Impact Factor (2016): 8.1891 (Calculated by GISI) www.jifactor.com © IAEME Publication

DESIGN OF ROOFTOP SOLAR PV Smita S. Kathar

PG Student, Department of Electrical Engineering, Government College of Engineering, Aurangabad (MH), India

A.G. Thosar Professor, Department of Electrical Engineering,

Government College of Engineering, Aurangabad (MH), India

Gunvant C. Patil PG Student, Department of Electrical Engineering,

Government College of Engineering, Aurangabad (MH), India

ABSTRACT In a view of global energy scenario and to meet increased demand for energy,

solar energy has been harvesting at faster rate across the world. To achieve the goal of sustainable development the maximum use of renewable resources is essential. In that respect, solar energy harvested in different ways such as solar thermal, solar photovoltaic etc. Similarly a solar photovoltaic systems have different configurations like, grid-connected, stand-alone which are either on ground surface or on rooftop. In this paper the grid-connected solar rooftop PV (RTPV) for Government College of Engineering, Aurangabad has discussed. Under Net-metering policy for the state of Maharashtra for grid-connected RTPV, the CAPEX model and the RESCO model are discussed. Estimation of RTPV capacity for given site is done based on contract demand or sanctioned load, utility distribution capacity and available shadow free area for RTPV installation. With estimated capacity of 119 kWp, the annual saving in electricity bill and payback period calculations are done in section-IV.

Key words: RTPV (rooftop photovoltaic); CUF (capacity utilization factor); Net-metering; Mtoe (Metric Tons of oil equivalent).

Cite this Article: Smita S. Kathar, A.G. Thosar and Gunvant C. Patil, Design of Rooftop Solar PV. International Journal of Electrical Engineering & Technology, 8(2), 2017, pp. 81–92. http://www.iaeme.com/IJEET/issues.asp?JType=IJEET&VType=8&IType=2

1. INTRODUCTION Use of solar energy is a need of time. With the view of global energy scenario, increased economic growth has put substantial increase in energy demand. To meet the increased demand of energy conventional energy sources like oil, coal, natural gas, etc. are being exploited at faster rate. These sources are exhaustive and going to

Design of Rooftop Solar PV


finish in coming future, so problem of energy security. Also as they are more polluting creates environmental issue like global warming. Therefore renewable resources which long lasting or in exhaustive, cleaner and cheaper has been harvesting across the world. The solar energy has tremendous potential on earth and it is a cleaner source for energy. Its utilization has been increasing day by day and governments formulating new policy to promote more use of solar energy. Solar energy is harvested in different forms like direct use for heating that is categorized as solar thermal, converted to electricity using solar photovoltaic. The solar photovoltaic systems have different configurations like, grid-connected, stand-alone which are either on ground surface or on rooftop. In this paper the grid-connected solar rooftop PV (RTPV) for Government College of Engineering, Aurangabad has discussed.

The paper is organized as, section-2 describes the energy scenario. The various types and configuration of solar PV system are discussed in section-3. In section-4, rooftop system design and analysis is presented. The conclusions are drawn in section-5 and references are listed at the end.

2. ENERGY SCENARIO The world mainly depends on fossil fuels like petroleum, coal and natural gas to meet its most of energy needs. As per the world energy statics data published by the EIA in 2015, over 80% of the total global energy requirements is met by oil, natural gas and coal. Based on the trends in energy consumption with overall economic growth, the estimated rise in worlds total energy consumption will be 12,487 Mtoe annually by 2040. The emission standards are also becoming more and more strict and precise. Under this scenario the world is formulating adequate policies to control the rise in global temperature to 20 °c, with that this consumption should stand at 10,748 Mtoe. Annually, approximately 32.19 billion carbon dioxide were released into the atmosphere globally in 2013 only from the combustion of fuel for primary energy supply as per IEA statistics [1]. The India’s carbon dioxides emissions were 1.869 billion. In the todays energy scenario world is facing problems like to meet increased energy demand, reducing the pollution and global average temperature with maximum use of clean and renewable energy sources. In this respect many countries across the world has devised new policies for renewable energy use and speeded up the installation. The world’s renewable energy capacity installation by the end of 2015 is shown in below figure 1. The estimated share of renewable power in global electricity at the end 2015 was accounted to 23.7% with hydropower providing about 16.6%. India has the vast renewable energy potential through wind, solar, biomass, small hydro etc. The year wise renewable energy capacity addition in Indias energy generation is shown in figure 2 below. During first four years of 11th five year plan from 2007 to 2015, about half of the renewable capacity addition has taken place. In April 2002, the installed capacity of renewable energy based power generation was 3475 MW, which was 2% of the total installed power generation capacity of India. By June 2016, it has increased to 44,237 MW, which was about 14.5% of total

Smita S. Kathar, A.G. Thosar and Gunvant C. Patil


(Source: REN21, Global Status report 2016)

Figure 1 Renewable capacity installation for various resources, 2015

(Source: CEA)

Figure 2 Year wise renewable energy capacity addition

Table 1 Current installed capacity and planned Renewable Energy targets

The wind power has dominated the total renewable generation constitutes around 61.4%. The table 1 below shows the current installed capacity and planned renewable energy targets. As per the annual budget of year 2015-16, the target of 175 GW [2] for renewable energy has set by 2021-22.

2.1. Solar Energy scenario The worlds solar PV installed capacity as of the end of year 2015 were at 227 GW of which the 50 GW capacity addition in the year 2015 itself. China, Germany, Japan and USA have vast new installation in the year 2015. With this the china has topped the list in total solar installation around the world while the Germany, Japan and USA stood at second, third and

Source Installed capacity by end

of 11th Plan (March 2012)

Current installed Capacity

(March 2015)

Target as per 12th Plan

(March 2017)

Planned Targets till

2022

Solar Power 941 3,383 10,941 1,00,000 Wind power 17,352 22,645 32,352 60,000 Biomass Power

3,225 4,183 6,125 10,000

Small Hydro 3,395 4,025 5,495 5,000 TOTAL 24,914 34351 54,914 1,75,000



fourth number respectively. For the first time India came in the top 10 countries ranked ninth in renewable capacity installation. The solar installed capacity in various countries is illustrated in figure 3. With such fast revolution in solar power technology in coming years, the total installed capacity in 2019 would reach an approximate to 450 GW [3]. Geographically India lies in the high solar insolation region and therefore has got huge solar energy potential. In most part of the country there are about 300 sunny days per year with an annual mean daily global solar irradiance in the range of 5-7 kWh/m²/day. The total estimated solar potential of the county is approximately 748.98 GW [4] as estimated by National Institute of Solar Energy (NISE).

To meet the growing power demand and government initiative has led to continuous growth in solar PV generation. As on September 2015, the total solar installed capacity stands at 4262 MW. The figure 4 below shows the solar power generation installed capacity as on July 2016. The government of India has proposed to scale up the existing target of 20,000 MW installed solar to 100 GW [2] by year 2021-22. It is proposed to have capacity addition under two categories of solar projects: Rooftop Solar Projects and Large Scale Solar Projects. The capacity addition under 100 GW solar scales up plan is shown in below table 2.

As on December, 2016 the Maharashtra’s installed solar power capacity were 386 MW [5] as per MNRE data.

Source: REN21, Global Status report 2016)

Figure 3 Solar installed capacity in various countries (as on Jan 2015)

(Source: NISE)

Figure 4 Solar installed capacity as on July 2016



Table 2 Capacity addition targets under 100 GW solar scale up plan

Category-I Proposed Capacity

(MW)

Category-II Proposed Capacity (MW)

Rooftop Solar 40,000 Projects by small scale industries, unemployed, village panchayts, etc.

20,000

PSUs, Large Private Sector, SECI, State Policies

30,000

Ongoing programmes 10,000 Total 40,000 60,000

By the year 2020, Maharashtra has set a target of 14.4 GW renewable power of which

solar power constitutes 7500 MW and the remaining comes from other renewables. To achieve this target the state has announced separate regulations and policy for grid-connected projects. As per these regulations the 2500 MW solar project shall be developed by MAHAGENCO in public private partnership mode and remaining 5000 MW solar projects shall be developed by other developers. Maharashtra Energy Development Agency (MEDA) shall be the nodal agency for the implementation of this policy. The state also declared Net-metering regulation to promote solar rooftop installations in the state. The solar projects can be installed in industrial area, warehouse area, townships, government buildings, etc.

3. TYPES OF SOLAR PV SYSTEMS The first step in the study was to analyze the major properties of SISRI. A detailed description of the analysis and the validation of the scale are given in the following section.

3.1. Grid-Connected PV System These systems are designed to operate in parallel and interconnected with utility grid. The schematic of grid-connected PV system is shown in below figure 5. A bidirectional power flow interface is made at site to supply electrical load at site and pumps extra power into the grid. The Power conditioning unit takes care of power conversion and power quality of supply.

Figure 5 grid-connected photovoltaic system.

3.2. Stand-Alone PV System The stand-alone PV systems are designed to operate independent of utility grid. In this type of systems the various configuration are found as direct coupled, with storage and charge controller and hybrid PV systems. The schematic of direct-coupled PV system is shown in figure 6. it is the simplest type of stand-alone system where PV array output is directly



connected to DC load; there is no storage and controller. So, these systems operate during sunlight hours. These systems are suitable for loads such as ventilation fans, water pumps, and small circulation pumps for solar thermal water heating systems. A typical stand-alone PV system powering DC and AC loads are shown in above figure 7. it consists of a battery storage and charge controller. A typical hybrid PV system configuration is shown in below figure 8. In this the solar PV array and an auxiliary source like wind generator and or diesel generator and or a utility grid is used to supply load. The hybrid systems are more reliable as compared to other described above [6]. The controllers like MPPT are used to utilize the maximum array capacity and increase the efficiency of system.

Figure 6 Direct coupled PV systems

Figure 7 Stand-alone PV system with battery storage powering DC and AC loads.

(Source: FAEC solar electricity)

Figure 8 Hybrid PV system

3.3. Grid Connected RTPV The rooftop solar photovoltaic (RTPV) grid connected models available in commercial market are broadly classified into two categories as Gross-metering and Net-metering.

3.3.1. Gross Metering In gross-metering arrangement all the energy generated from rooftop solar PV is fed to the grid at a Feed-in-Tariff as per state electricity regulatory policy. A Power Purchase Agreement is signed between the distribution utility and the system owner. The system installation can be done either by roof owner or by a third party player. The installation done



by roof owner termed as Self-owned and the third party installation is done with roof rent agreement with roof owner.

3.3.2. Net-Metering In net-metering arrangement the energy generated is first consumed by system owner internally and surplus generation, if any, is fed to utility grid. The energy charges for net energy fed to grid are settled as per local net-metering regulation. The typical single line diagram of Net-metering scheme is shown in figure 9. Based on ownership pattern the Net-metering scheme is further divided into two types as follows,

3.3.2.1. RESCO (Renewable Energy Service Company) Model In this scheme, the third part player does the system installation on rooftop of the consumer and owns the system. The electricity generated from the rooftop solar PV is first consumed by the rooftop owner as per the mutual tariff agreement signed between the rooftop owner and the RESCO. The excess electricity generation is then fed to utility grid and revenue generated as per net metering tariff structure.

3.3.2.2. Self-Owned Model In this scheme, the rooftop owner installs the rooftop solar PV system and owns the system. The generated electricity is first consumed by system owner and surplus generation is fed to grid as per state net-metering tariff policy. Here the rooftop owner do invest in system installation and arranges loan for project. So within both the two schemes of net-metering framework there can be either a self-investment or third party investment in rooftop solar PV system. The net-metering framework is available in the state of Maharashtra as announced in the Maharashtra Electricity Regulatory Commission (Net-Metering for Rooftop Solar Photo Voltaic Systems) Regulations, 2015 [7].

Figure 9 Typical SLD of net metering based RTPV solar system

3.3.3. Regulatory Policy and Deregulation The Electricity Act 2003 has changed legal and regulatory framework for the renewable energy sector in many respects. EA 2003 was passed and made effective from June 10, 2003. It is the single most important piece of legislation for the sector and effectively nullifying all earlier enactments that governed the electricity businesses. EA 2003 provides for policy formulation by the Government of India and mandates SERCs to take steps to promote renewable and non-conventional sources of energy within their area of jurisdiction. Further, EA 2003 has explicitly stated the formulation of National Electricity Policy (NEP), National



Tariff Policy and plan thereof for development of power systems to ensure optimal utilization of all resources including renewable sources of energy.

Extract of relevant sections of EA 2003 Section 3, Section 4, Section 61(h), Section 86(1) (e).

4. ROOFTOP DESIGN Government College of Engineering, Aurangabad is an Autonomous Engineering Institute in Maharashtra State of India. It is affiliated to the Dr. Babasaheb Ambedkar Marathwada University and was established in 1960.

Figure 10 Annual Temperature Pattern of Aurangabad

Aurangabad in Maharashtra falls in semi-arid climatic zone. Annual mean temperatures are in the range of 17 to 33 Degrees Celsius. The maximum temperature sometimes would cross 45 °C in summer season in the month of April or May. The averages for minimum and maximum monthly temperatures for the years 2000 till 2012 are shown in the figure 10. The optimum angle of tilt for solar modules in Aurangabad region is 22.1 and would have solar radiation of 5.83 kWh/m2/day, taken from historical data available from NASA.

4.1. Site Assessment The Government college of Engineering has two RCC buildings which are suitable for RTPV installation. In site visit roof condition, shadowing objects and available shadow free area were assessed. Both the buildings have single consumer number. The site visit and site survey has been done to collect the important data. Measurement of shadow-free area, electricity consumption and other information like sanctioned load, connected load, connection voltage etc. were done at site. The collected data is tabulated in table 3. Data analysis of each building was done by considering the following factors, 1. Shadow free area available for array installation: The shadow free area out of total roof area was calculated. The deductions were applied for shadowing objects on the roof and near to roof. 2. Annual electricity consumption in the building and all buildings under single consumer number: This information was analyzed from collected electricity bills. 3. Existing power network: The data like interconnection voltage from utility, contract demand, etc. was analyzed. The recommended capacity calculations were done based on the four factors as per net metering policy in Maharashtra state. The details are mentioned below.



a) Permitted Individual Capacity Cannot be more than the contract demand (kVA is converted to kW with the factor of 0.9) or the sanctioned load.

Table 3 College building electricity consumption data

Name Government College of Engineering, Aurangabad

Consumer Number 490019003750 Contract Demand 110 kVA Connected Load 450 kW Sanctioned Load 450 kW Feeder Voltage 11000 Volt Consumption /Year 352265 kWh Consumer Category HT IX (A) Public Services-Government

b) Permitted Transformer level Capacity Cumulative capacity cannot be more than 40% of the immediate upstream distribution transformer.

c) Possible Capacity in available shadow-free area Shadow-free area required for 1 kWp on flat terrace -10 m² Shadow-free area required for 1 kWp on tilted surface -10 m².

d) Required capacity to energy consumption Safe to assume 16% Capacity Utilization Factor (CUF) for rooftop system and arrive at capacity necessary to meet energy requirement.

4.2. Recommended Capacity Estimation As per the Net-metering policy for the state of Maharashtra, capacity estimation for solar RTPV is done and results are tabulated in below table 4. The calculations are done for two buildings in campus having RCC construction and suitable for RTPV installation. Both the building has single consumer number as 490019003750. The shadow free area available from building A is 1327 m² and from building B is 412 m².

The area 11.5 m² per kWp is considered for RTPV with available solar insolation. With that the possible capacity for building A and B are 115.4 kWp and 35.8 kWp respectively. According to the net-metering constraint the maximum possible capacity has been decided which is minimum of among them that is 118.80 kWp from the table 4. Also capacity assessment based on the annual consumption is calculated and tabled in below table 5. This capacity estimation is important, because any system larger than 251 kWp would be waste and not economically viable as per Net-metering policy framework. The required capacity of both the buildings is 251 kWp, is quite higher than estimated possible capacity of 118.80 kWp under net metering scheme. All the analysis and observation stated above we came to the final recommended capacity for installation on each building separately. One of the possible combination is given in table 6. This estimate is based on site survey, certain assumptions, Net-metering policy for the state of Maharashtra and an assumed typical design. The optimum efficient system design as a different sub-array configuration or breaking system into different capacities is further part of study and has left to system developer.



Table 4 Recommended capacity estimation

Table 5 Capacity Estimation based on consumption

Campus Area Consumer Number

Annual Energy Consumption

(kWh)

Required Capacity (D) @16% CUF

(kWp) College Building-A 490019003750 352,265 251 College Building-B

Table 6 Final overall recommended capacities

4.3. Proposed RTPV Model and Results After estimation of appropriate RTPV system capacity as per Net-metering framework the saving in electricity bill and calculation of payback period is done. The proposed system details and results are given in table 7. In this the project cost of Rs. 52,000 per kWp solar panel is assumed as per market scenario. The payback period calculations is given by below formula,

Payback period (in years) = (initial investment in Rs.)/ (Annual saving in Rs.).

Category Capacity (kVA)

Capacity converted to kW

Possible Capacity

(kW)

Possible Array Capacity

@DC:AC ratio of 1.2

(kWp) Based on Contract Demand

110 99 (@ 0.9 power

factor.)

99 (@ 100% of

CD)

118.80

Based on Transformer

315 252 (@ 0.8 power

factor.)

100.80 (@ 40% of TC)

120.96

Based on Shadow free Area 118.80

Campus Area Module Capacity

(kWp)

RTPV Annual Generation Estimate (kWh)

College Building-A 46.10 College Building-B 73.00 Total 119.10 1,56,103 Proposed Interconnection Voltage (kV)

0.415

Metering Voltage (kV) 11



Table 7 Prosed System details and results

Sr.No. Item Description Details 1 Existing Contract Demand (kVA) 110 2 Recommended installation capacity of

RTPV (kW) 119

3 Annual consumption of Units (kWh) 352265 4 Annual Average Electricity bill Rs. 2,20,875/-

(Two Lac Twenty Thousand Eight Hundred Seventy Five)

5 Average per unit cost (Rs. /unit) 7.52 6 Project Cost @Rs 52,000/- per kWp 61,88,000/-(Sixty One Lac

Eighty eight thousand) 7 RTPV Annual Generation (kWh) 1,56,497 8 Annual Energy Generation in Rs Rs. 14,09,265/- 9 Saving in Electricity Bill (Rs./year) 12,39,459 10 Payback period (approximate) 5 Years

5. CONCLUSION Use of solar energy is a need of time. With the view of global energy scenario, increased economic growth has put substantial increase in energy demand. At the same time over exploration of conventional energy sources to meet the increased energy demand results in depletion of these resources, increased pollution and raised environmental issues like global warming. Also these resources are exhaustive and with this rate of utilization they are going to vanish, so also possess issue of energy Security. As per the sustainable development agenda by governments optional energy sources has been searched, which are in-exhaustive, cleaner and cheaper. Solar energy has tremendous potential on earth and it is a cleaner source of energy. Solar energy harvesting across the world has been increased at a faster rate.

In this paper the solar RTPV system is discussed in details as per net-metering policy for the state of Maharashtra. Site assessment for RTPV installation is done at Government College of engineering, Aurangabad, Maharashtra. The detailed study is presented in section-iv in this paper. The RTPV capacity estimation in kWp is done based on sanctioned contract demand, utility grid distribution capacity and available shadow free area. With estimated RTPV capacity saving in electricity bill and payback period analysis has discussed in section-iv.

REFERENCES [1] A report on “World Energy Outlook, 2015 Special Report on Energy and Climate

Change.”

[2] “Draft National Electricity Plan” Available at http://www.cea.nic.in/reports/committee/nep/nep_dec.pdf.

[3] REN21, “Renewables 2016: Global Status Report (GRS),” 2016. [Online]. Available: http://www.ren21.net/

[4] “State wise Estimated Solar Power Potential in the Country, 2014-15” a report by NISE (National Institute of Solar Energy).

[5] Samir S. Kouro, J. I. Leon, D. Vinnikov, and L. G. Franquelo, “Grid-connected photovoltaic systems: An overview of recent research and emerging PV converter technology,” IEEE Ind. Electron. Mag., vol. 9, no. 1, pp. 47–61, Mar. 2015.

[6] Leopoldo G. Fra Nquelo “grid-connected-solar-power-project-installed-capacity” by MNRE, 2016.



[7] “Draft Net metering for Rooftop Solar Systems” MERC Regulations, 2015.

[8] Swapnil Shende, Sankalp Pund, Pratik Suryawanshi, S hubhankar Potdar, Analysis of PI Controller’s Manual Tuning Technique for Residential Loads Powered by Solar Photovoltaic Arrays. International Journal of Electrical Engineering & Technology, 7(6), 2016, pp. 75–80.

[9] Rajeev Kumar Sharma, Sohail Bux, V. K. Sethi and A. C. Tiwari, Environment Friendly Solar Roof Top Plant. International Journal of Mechanical Engineering and Technology, 6(9), 2015, pp. 94-101

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