RAMESH R. GOWDA REGIONAL MANAGER – INFRASTRUCTURE, INFOSYS LTDMANI R. KRISHNANSR. MANAGER – GREEN INITIATIVES, INFOSYS LTDRAKESH BOHRAASSOCIATE MANAGER- GREEN INITIATIVES, INFOSYS LTD

Shifting Towards New Dimensions in Solar Photovoltaic (PV) Roof Top SystemsInfosys has always believed in taking calculated risks and trying out innovative ideas to overcome the daunting challenge of energy scarcity and sustainability as a whole. As a proactive measure, the team undertook a practical study to evaluate the feasibility of different orientations of solar PV rooftop modules. The team has some critical learnings from this study which have been elaborated in the article

Across its landscape, India has abundant access to solar energy. India’s Global Horizontal Irradi-

ance (GHI) varies from 5.8 to 6.8 kWh meter square per day and is twice as high as that of Germany, which has the highest solar Photovoltaic (PV) installations in the world. With atotal solar capacity of more than 3 GW, India is endowed with ample solar energy, which is capable of produc-ing 5,000 trillion kilowatts of clean energy. We are blessed with around 300 sunny days in a year and solar insolation of 4-7 kWh per Sq. m per day (Ministry of New and renewable Sources, MNRE)

Recent projections by MNRE, suggest that by 2020, India will be targeting at im-plementing solar PV power projects with a capacity of 20 GW. Furthermore, as de-clared in the current budget, government

is ambitious to extend this up to 100 GW by 2022.While there are different strate-gies for achieving this target, most recom-mend the solar rooftop projects over grid-connected multi-MW-scale projects.

Solar rooftop can be a boon to states and cities that are facing acute power deficit and issues of land scarcity.However, a major concern istheorientation of solar modules used in the installed solar rooftop system. Mostrooftopinstallations in India are oriented based on thumb-rule meth-odology.The thumb-rule methodology advocates that southward orientation of solar modules can harness the maximum amount of solar energy. This is most ben-eficial to India since it is situated in the Northern hemisphere. Although this holds true, the holistic advantages of other ori-entations cannot be undervalued.

At Infosys, we are committed to meet-ing our goal of sourcing100 percent of our electricity demands from renewables by 2018. During the fiscal year 2014, we used over 76 million units of electricity i.e. 30 percent of the total electricity needs from renewables- purchased green power and on- site solar plant generation. During the same period, we generated over 1100 MWh of electricity through our onsite solar PV installations across India. Currently, we have 2 MW of solar PV installations across our campuses in India and we plan to in-crease it to175 MW in the next few years through on- site and off-site installations.

Infosys has always believed in taking calculated risks and trying out innovative ideas to overcome the daunting challenge of energy scarcity and sustainability as a whole. As a proactive measure, we un-dertook a practical study to evaluate the feasibility of different orientations of solar PV rooftop modules. As part of the study, we installed solar PV modules in the east-west direction as opposed to the tradition-al southwards orientation in our Chennai Campus. We found some critical learnings from this study which have been elabo-rated in the sections below.

Types of module orientation on rooftop

Southwards orientationThis is the most common methodology of module orientation and the most effi-cient one wherein the module is oriented in southwards direction. With southwards

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orientation,sun can be tracked to its maxi-mum limit, thus generating maximum en-ergy. However, a major drawback with this type of orientation is that it requires a larger area and also leads toshadow losses. To re-duce shadow losses, system needs to be de-signed in such a way that no solar plates in one row cast a shadow on another at any point of time. With this orientation, the tilt angle widens, increasing the pitch and re-ducing the available space.Modules installed insouthward orientation are favorable for places with high energy demand.

East-West orientationEast- west orientation of modules is the best method to optimally utilize the avail-able space. On flat roofs, this orientation has the capability of maximizing the num-ber of PV modules in a way that they don’t cast a shadow on each other. Through this method, solar PV systems can be installed on East-West-oriented (E-W) or slanted roofs as well.

One of the primary challenges withE-W installation is avoidingmismatchlosses due

to different inclinations. Some of the basic aspects that need to be considered during such installations are:• Avoid shading as much as possible to

maximize power generation.• Keep the total number of Solar PV

modules the samein all the strings.• The inclination of modules within one

string should be the same.The advantages outweigh the disad-

vantages by far in case of E-W-oriented installation as compared to the south-ward-oriented installation.E-W orientation increases the number of PV modules by over 20-50 percent. On the other hand, the southward-oriented PV modules fill only 30 percent of the total space due to inter-row spacing.

E-W oriented modules require different inverters for each direction or an inverter with more than one Maximum Power Point (MPP) tracker. This is required to avoid the mismatch losses due to constant fluctua-tions in irradiation level. In our case, we have used a single inverter with a dual MPP trackerto reduce the system size and the

number of inverters, thereby cutting the total cost.

The energy losses are highest on a bright sunny day aslower irradiation leads to dif-ferences between the strings connected to the E-W-orientations. It is evident in the graph abovethat E-W installation is rec-ommended for sites with a lot of diffused irradiation.

In our study, we aimed at maximizing the installed plant capacity and yield out of the available space. To align with this objective, layout options were worked out with southwards oriented and E-W orient-ed modules (with a tilt angle of 9 degrees).The technical details of thestudy are given below (table 1).

We simulated the area to install PV modules with different orientations on the same building roof. It is evident from the above simulation diagramthat more DC capacity with E-W orientation can be installed as compared to the southwards-orientationon the same roof area. We were able to successfullyinstall an ad-ditional 240 solar modules of the same

Top image depicts the Southwards oriented installation and the below one depicts the East-West installation. The use of space can be easily noticed in the picture.

Table 1. Infosys Chennai Campus: Latitude 12.7°N, Longitude 80.0°E

Orientation Plant Area Installed DC Capacity(kWp) No. of Modules (327Wp) Specific Yield(kWh/ kWp/year) PR % Energy Generation (MWh/year)

South Facing Same Size roof plot 235.4 720 1566 77.1 368.8

E-W Facing 313.92 960 1557 77.6 488.7

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rated capacity, i.e. over 33 percent (com-pared to southward orientation), in our Chennai Campus with E-Worientation.Thepower generation of the plantwit-nessed a reduction of merely 5 percent as compared to an optimal south-orientated installation. Also, theinverter efficiency has improved substantially as the inverter is loaded uniformly throughout the day.

Advantages of E-W PV Module Orientation• Over 20-30 percent more installed

capacity in the given area: One kWp of array in 7.5-8.5 sq.m area

• Yield per sq.m of installed area is more due to the elimination of shad-ing distances

• Even distribution of electricity genera-tion throughout the day

• Greater energygeneration during peak demand hours in the morning and evening,leading to savings w.r.t ‘Time of Use’ tariff systems

• Reduction in wind load in the case of aerodynamic structures

ConclusionWhile the solar PV industry is flourishing, it is pivotal to check and verify the feasi-bility of the orientation used in module installations. Before finalizing the orienta-tion, it is critical to understand the load profile calculations and building archi-tecture. In case of a challenging building architecture and energy demands/costs, East-West orientation may fetch attrac-

tive results. Our study clearly demon-strates that E-W orientation substantially increases the DC capacity of installations by nearly 33 percent on the same size of roof than southward orientation and also

results in considerable amount of power generation. E-W orientation can definitely prove to be a pioneering method in har-vesting solar energy on challenging roof-top structures 7

Plan View of roof top Project within same plot area.

Normalized production per kWp with different orientations (Left: Southwards orientation; Right: East-West Orientation) on the same roof

References1- The impact of array inclination and orientation on the performance of a grid-connected photovoltaic System

Jayanta Deb Mondola,_, Yigzaw G. Yohanisa, Brian Norton School of the Built Environment, University of Ul-ster, Newtownabbey, Northern Ireland, BT37 0QB, UK Dublin Institute of Technology, Aungier Street, Dublin 2, Ireland (Received 8 March 2006; accepted 24 May 2006 Available online 18 July 2006)

2- Orientation and Tilt Dependence of a Fixed PV Array Energy Yield Based on Measurements of Solar Energy and Ground Albedo –a Case Study of Slovenia Jože Rakovec1, 2, Klemen Zakšek2, 3, Kristijan Brecl4, Damijana Kastelec5 and Marko Topič4[1] Faculty of Mathematics and Physics, University of Ljubljana, Slovenia[2] Centre of Excellence Space-SI, Slovenia[3] Institute of Geophysics, University of Hamburg, Germany[4] Faculty of Electrical Engineering, University of Ljubljana, Slovenia[5] Biotechnical Faculty, University of Ljubljana, Slovenia

3- Efficient East-West Oriented PV Systems With One MPP Tracker, Dipl.-Ing.(FH) Dietmar Staudacher FRONIUS International GmbH Froniusplatz 1, A – 4600 Wels

4- Evaluating the Impact of PV Module Orientation on Grid Operation, Eckehard Tröster Jan David Schmidt, Lis-bon, 13th November 2012, 2nd International Workshop on Integration of Solar Power into Power Systems

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