Technical evaluation of existing commercial andresidential PV rooftop systems in South DelhiFinal Report

Disclaimer: While care has been taken in the collection, analysis, and compilation of the data Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH does not guarantee or warrant the accuracy, reliability, completeness or currency of the information in this publication. The information provided is without warranty of any kind. GIZ and the authors accept no liability whatsoever to any third party for any loss or damage arising from any interpretation or use of the document or reliance on any views expressed herein.

Technical evaluation of existing commercial and

residential PV rooftop systems in South DelhiFinal Report

October 2017

Contents

List of figures 04

Abbreviations 05

Acknowledgment 06

Executive Summary 07

1. Introduction 08

2. PV modules 10

2.1 Cell type 10

2.2 Module type glass-foil vs. glass-glass 10

2.3 Module quality – positive tolerance 11

2.4 Dirt and dust 12

3. Inverter 13

3.1 Inverter type 13

3.2 Inverter to PV generator sizing 13

3.3 Grid parameter 14

3.4 Inverter ventilation 14

4. Mounting system 16

4.1 Material used 16

4.2 Mounting type 16

4.2.1 Single row free standing triangles 16

4.2.2 Multiple row freestanding triangles 17

4.2.3 Superstructures 18

4.2.4 Roof parallel installation on pitched roofs 19

4.2.5 Module fixing / module clamps 19

4.2.6 Orientation and inclination of the modules 20

4.2.7 Shading 20

5. Accessories 21

5.1 Cable ties 21

5.2 PV Connectors (plugs) 21

5.3 Cable type, diameter and cable conduits 21

6. Grid Voltage 23

7. Remote monitoring system 24

8. Maintenance contract 25

9. Conclusion 26

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List of figuresFigure 1: System performance (kWh/kWp*a) of the 15 inspected sites. 09

Figure 2. Needed module area for one kWp installed. Source: SMA 10

Figure 3: Damages at the fragile back foil of the module. It remains unclear if it was damaged during the installation process or due to multiple use of the roof top. 11

Figure 4: Dirt of about one to two weeks accumulated on a module in South Delhi. 12

Figure 5: Bird nest on an inverter could lead to overheating of the inverter. 14

Figure 6: Accumulated dirt on the ventilation fence of an inverter. This could lead to insufficient ventilation and consequently potential yield losses. 15

Figure 7: Materials used for the mounting system. 16

Figure 8 : Single row freestanding triangles - horizontal 17

Figure 9: Single row freestanding triangles partly shaded by the surrounding wall in the morning hours. 17

Figure 10: Partly shaded module by the front row. This small shadow has a big impact on the whole string. 18

Figure 11: Superstructures provide shade and avoid conflict in case of multiple use of the roof top space. 18

Figure 12: European style roof”. The modules are not installed in line. 19

Figure 13: Corrosion on the module screws and insufficient fixing methods can lead to destruction of the PV generator and is a potential threat when falling off the roof in heavy weather conditions. 19

Figure 14: The picture shows a roof structure which causes significant shadow to parts of the PV generator. This has a negative impact on the system performance. 20

Figure 15: Broken Pipe conduit on the roof can lead to system failure and can be a potential health risk. 22

Figure 16: Proposal for an annual report given by the DISCOM to help system owner understand if his or her installations performing well or if measures of improvement should be taken. 24

Figure 17: Top 4 and last 4 systems ranked according to their system performance. There seems to be a correlation between the quality of the inverter, the cleaning frequency and the mounting structure and the system performance. 26

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AbbreviationsAC Alternating current

BMZ German Federal Ministry for Economic Cooperation and Development

BRPL BSES Rajdhani Power Limited

BSES Bombay Suburban Electric Supply

CEA Central Electricity Authority

DISCOM Distribution Company

GIZ Deutsche Gesellschaft für Internationale Zusammenarbeit

IGEN Indo German Energy Programme

INR Indian Rupees

IP Ingress Protection

kVA Kilo Volt Amperes

kWp Kilo Watt peak

MC Multi-Contact

MPP Multi Power Point

MNRE Ministry of New and Renewable Energy, Government of India

NIWE National Institute of Wind Energy

PV Photovoltaic

PVRT Photovoltaic Rooftop

UV Ultraviolet

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Acknowledgment The authors would like to thank the Ministry of New and Renewable Energy, India, and the Federal Ministry for Economic Cooperation and Development Germany, for the ‘Photovoltaic Rooftop’ project under the Indo-German technical cooperation.

We also take this opportunity to thank BSES Rajdhani Power Limited, Delhi, for their invaluable support during this project. The authors also acknowledge, Sadaf Shah, for her coordination in conducting the survey. A special thanks to National Institute of Wind Energy for providing the Solar Radiation Resource Assessment data for the simulations.

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Executive SummaryPV rooftop system survey was conducted in April 2017. The survey included randomly selected 15 systems in the distribution network of BSES Rajdhani Power Limited (BRPL) in South Delhi. The scope of survey is to technically evaluate PV rooftop system installations. It identifies specific shortcomings in randomly selected rooftop systems installations in New Delhi and provides recommendations on how to address those shortcomings in order to support Indian Government in meeting its ambitious grid-connected solar rooftop target of 40,000MW by 2022.

The author draw on the experiences, made in the initial phase of the photovoltaic industry in Germany. The recommendations thus made draws on the learning from the German solar market with an objective to enable Indian solar sector to ensure performance and system life through quality assurance.

In the survey, both individual components and boundary conditions are analyzed. Many findings were related to either quality defects of the components or lack of awareness among the installer or the system owner. We recommend, on the one hand to increase the efforts for training and awareness programs while, on the other hand to draft stricter guidelines in regards to the quality of the system components as well as introduce measures for long term quality control such as remote monitoring systems and maintenance contracts.

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1. IntroductionThe aim of the inspection was to get an overview of the technical knowledge of the rooftop photovoltaic system installation companies in India. In order to give recommendation, or guidelines for possible knowledge transfer to the installers and distribution companies (DISCOM).

The Indian solar roof top industry is just at the beginning. The industry stands today where Germany was 10 or 15 years ago. In Germany many mistakes were made initially. The aim is a transfer of knowledge to the Indian Solar roof top industry to help India avoid those mistakes.

We inspected and evaluated 15 commercial and residential Photovoltaic (PV) rooftop systems in South Delhi during third week of April 2017. All systems were located in the DISCOM network of BSES. To get sufficient results it was made sure that the examined PV installations were from a range of different installation companies. The size of the roof top PV systems surveyed were between 3 kWp and 120 kWp.

In general the quality of the PV-systems has increased since the last examination in 2013 by members of the AWASOL GmbH in India. However some of the installations were in suboptimal conditions or have been planned or installed in a suboptimal way.

Since the sample size of our survey is comparatively small (15 from the around 250 rooftop systems installed) this report does not claim to be scientific. We recommend that trends and patterns of our survey would have to be reconfirmed by a second study comprising of statistically significant sample size.

To evaluate a photovoltaic system the gold standard in the industry is the system performance measured in kWh/kWp*a. This performance is strongly dependent on the location, the inclination and orientation. It is relatively easy to project future yields of a PV installation. The system performance can be used to compare systems with a similar orientation, inclination and location.

The expected system performance for a PV system in Delhi is projected with annual yield of 1800 kWh/kWp. Those projections are based on satellite data. Due to the atmospheric pollution in Delhi (fine dust and dust) we estimate that the real performance a well-planned and maintained system could reach around 1500 kWh/kWp and year. We compared projected yields from PV Syst with data from the generation meter for the year 2016 of each system.

Besides the system performance we used an evaluation matrix which focused on the quality of the components and the installation. Therefore, it is likely that the systems having good system performance in terms of the yield might have a lower ranking in our matrix because of other issues like corrosion on the mounting system or incorrect installation of important system components. Here we also tried to estimate the outlook of the system in the next 5 years.

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Figure 1: System performance (kWh/kWp*a) of the 15 inspected sites.

The following questions have been addressed in this report:

A: Which standard PV components are most suitable for the Indian roof-top market?

B: Are Indian PV-Installers sufficiently trained to install PV-Systems?

C: Is there still knowledge transfer needed?

D: What are the best measures to ensure a good and sustainable PV-performance under the local conditions?

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2. PV modules

2.1 Cell typeThe evaluation showed that more than 90 per cent of the installations have been installed using the poly crystalline cell technology. This technology has some cost benefits over the mono crystalline technology. However mono crystalline modules have a slightly better performance in hot climate. This is due to the better temperature coefficient of mono than that of poly crystalline modules. Typical polycrystalline cells have a temperature coefficient of power as -0.45%/K while a monocrystalline have temperature coefficient of power around -0.3%/K.

In the last few years the price difference between mono and poly crystalline modules is getting smaller, so that the initial cost benefits for poly crystalline modules might be still there, but calculated over the expected 25 year lifetime of the PV system the total return of investment would be higher using the monocrystalline modules.

Another benefit of using mono crystalline modules is that this module type needs less space, or to put it in another way: It is possible to install more kWp on the same roof space compared to the poly crystalline technology. Since space on a roof top is the limiting factor, the use of mono crystalline modules would lead to a more efficient use of the roof space available.

• Therefore our recommendation would be to promote mono crystalline modules for the Indian roof top market. Towards this, additional financial incentives are not needed, however awareness programs for the consumer should be executed. That could increase the total installed capacity and the annual production by 5 to 10%.

Figure 2. Needed module area for one kWp installed. Source: SMA

2.2 Module type glass-foil vs. glass-glassThere are basically two types of modules available on the market. The most common one are the glass-foil modules. The less common are the glass-glass technology modules. All inspected systems have the cheaper glass-foil technology. The glass-foil modules have a glass front-side and a foil back-side. The glass-glass modules have glass on the front as well as on the back side of the module.

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The advantage of the glass-foil technology is again the price benefit. A regular glass-glass module has currently a market price for the installer of INR 7 to 11 (0.10 to 0.15 €) above the more common glass-foil technology (04/2017).

However, the cheaper glass-foil modules have two big disadvantages: On the one hand the back-side of the module is very fragile. A single scratch on the back foil can lead to severe damage of the module. During the inspection we found 3 installations (20 %) with at least one damaged back foil. The damage occurred (with high probability) during the fixing of the modules to the mounting structure. Since the mounting structure is made of metal with sharp edges, it is easy to scratch the back foil, especially when there is a lack of awareness or training on the installer side. Because roof tops often are multiple use spaces there is the likely possibility of unintended damages to the back foil of the modules during the lifetime of the installation. This could reduce the longevity of the installation.

On the other hand the glass-foil technology has an expected life time of about 25 – 30 years. The glass-glass technology is expected to achieve a 40 year lifetime. This would lead to a more sustainable energy production in India. Also glass-glass modules are not that sensitive on the backside. Small scratches on the back side during the installation, during the cleaning or because of unintended negative effects of multiple use of the roof top can be avoided or at least limited.

Furthermore the glass-glass technology has two additional positive effects. First, with glass-glass modules the expected energy production can be increased by another 5-10% because the back side of the cell receives and converts light. Second, positive effect is: with the semi-transparent glass-glass modules (especially in combination with an elevated solar roof ) the space underneath the structure can be used and thus the roof remains available for multiple use.

• It is recommended to increase the awareness of the advantages of the glass-glass modules. There seems to be a lack of training or awareness towards the sensitivity of the glass-foil modules among the installers and the consumers.

Figure 3: Damages at the fragile back foil of the module. It remains unclear if it was damaged during the installation process

or due to multiple use of the roof top.

2.3 Module quality – positive toleranceWe found that some of the installations were using less common module brands. Some of those brands did not have a positive Watt peak output tolerance. A positive Watt peak tolerance is a quasi-standard among tier-1 modules and is an indicator for a higher quality brand.

If modules with a non-positive tolerance are used, the system performance might go down because the whole string is limited to the output of the lowest performing module.

• It is recommended to increase the awareness among the end consumers to be more sensitive to positive watt peak output tolerance when comparing different offers.

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2.4 Dirt and dustThe accumulation of dirt or dust in the Delhi area is a real problem and can lead to significant yield losses of a PV-system. The interviews showed that the system owners are aware of this issue and most of them take measures to reduce the impact of soiling by regular cleaning the PV generator. On the other hand cleaning the modules is time consuming and sometimes also limited by the cost factor.

• To get the best yields from a PV system we would recommend to clean the modules once a week using low mineral or distilled water and a soft fabric / flannel. The system owner or the cleaning person has to be instructed how to handle the modules and to be careful with the rest of the installation e.g. the cables or the cable conduit. So that the cleaning of the modules does not affect other parts of the installation in a negative way.

Figure 4: Dirt of about one to two weeks accumulated on a module in South Delhi.

• It is recommended to promote the use and the advantages of a solar PV superstructures. Especially in combination with glass-glass modules alternative use of the roof space would be possible or even improved due to the shade which would be produced by the PV superstructure.

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Inverter

3.1 Inverter typeIn our sample we could not find a dominant inverter brand. The range of brands was quite diverse. The most common ones we have seen in the south Delhi area were: Delta, Tata/ Growwatt, Fronius, SMA, Power-One & Solarworld. More than 80 % of the inverter had only single-MPP tracker. The benefit of the single MPP inverter is the lower price.

During our study we have seen that in many of the systems multiple inclinations or orientations were used on the same PV generator or module string. The top 5 performing systems were all using high end European inverter brands. There seems to be a relationship between the system performance and the inverter brand /quality. But the sample size of our study is too small to make a reliable statement.

The advantage of duo- or multi-tracker inverter is that with more MPP trackers the inverter will perform better if there are different inclinations or orientations within the same PV generator. Another benefit of a multi MPP inverters in regards to the Indian roof top program is that on roof tops in highly populated areas like Delhi we will often have a negative effect of shading either from an object on the building itself or from neighbouring buildings. Multi-MPP inverters can reduce both: negative effects of orientation and inclination imbalance as well as negative effects for partly shadowed PV generators.

• The interviewed system owners mostly relied on the recommendation of the installer for the inverter choice. Therefore, our recommendation is to increase the awareness of the installer in regards to the multi MPP tracker. This will have a long term benefit on the performance of each system.

3.2 Inverter to PV generator sizingAt the moment there is a recommendation by the DISCOM to oversize the PV generator field by 20 to 30% compared to the max AC output of the inverter. The rationale behind this recommendation is that by oversizing it can be ensured that the inverter is operating at near max. efficiency level. For the grid this might be beneficial because the system will feed more equally into the grid, without a spike in the noon time.

However, we inspected one installation where the inverter had a maximum output of 4.6 kVA and the recommendation by the installer to the customer was to install a 7 kWp PV generator. In this particular case we had the monitored data of the inverter. Those data showed that the inverter was cutting down the power to 0 when it reached the 4.6 kVA AC maximum. And it took 10 to 15 minutes to reach the maximum again. The same inverter type was installed in two other systems so it seems to be a popular inverter.

The higher PV generator capacity has also a negative impact on the inverter. The constant load will wear out the inverter more quickly and thus the inverter has to be replaced more often during the life time of the system.

This indicates that there could be a lack of knowledge by some installers in terms of sizing the system.

• A more conservative system design in the range of 90%– 110% (total installed kWp capacity to AC output of the inverter) is recommended. This is the typical default setting in most of the inverter sizing programs and will most likely increase the life time of the inverter under the climate conditions in India.

• Further, to increase the awareness of the installer in terms of sizing the PV system. Sizing programs like PV Syst, PV-SOL, SOLARSCHMIEDE or similar system design software’s are available on the market. One barrier could be that those software’s cost about INR 15,000-20,000 (200 – 300 €). We would suggest to give one license to each installation company and to carry trainings on how to use these software tools to avoid planning mistakes by the installer including best practice studies. Another

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approach could be to encourage the development and launch of an affordable sizing software especially made for the Indian market which could find wide acceptance among installers and thereby help to resolve the mentioned problems.

3.3 Grid parameterIn at least two cases we detected heavy local grid instabilities and fluctuations of the AC voltage level. For a reliable operation of the inverter a stable AC voltage and frequency level is very important. The inverter can only operate in certain parameter windows.

When the grid is outside those parameters the inverter will drop out and not feed in to the grid as a consequence.

At one site the AC voltage level was higher than 260 V. So the installer had to change the parameter settings. In other places voltage stabilizers were being used to reduce the voltage.

• It is recommended to increase the awareness of the negative effects of high voltage levels. It should be made possible for the Indian PV-installers to adjust the inverter settings flexible to the local conditions. The DISCOM should be able to give special approval in extreme cases. This is a common standard also with DISCOMs in Germany. Maybe one has even to rethink parameter settings and widen those parameters hence to the instable grid parameters.

3.4 Inverter ventilationIt is very important that the inverter is cooled down as good as possible. The inverter has either a passive cooling (cooling fins) or active cooling using active ventilation. For a sufficient cooling it is key that the cooling fins or the ventilation cambers are free from dust. It is also important that there are no objects on the top of the inverter. Neither man-made objects (e.g. Operation manual) nor other objects like bird nests. Both have a negative impact to air ventilation and cooling of the inverter. If the inverter is not cooled down efficiently the inverter could reach the maximum internal operation temperature and shut down. This has of course a negative impact to the annual yield of the system.

Our survey showed that the ventilation of many inverters was affected by dirt or other objects. This is specially the case when the inverters are installed outside.

Figure 5: Bird nest on an inverter could lead to overheating of the inverter.

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Figure 6: Accumulated dirt on the ventilation fence of an inverter. This could lead to insufficient ventilation and consequently

potential yield losses.

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4. Mounting system

4.1 Material usedMost of the structures were made of galvanized steel (8 out of 15). Galvanized steel is a good material for a mounting system and should last the expected life of 20 to 30 years of the PV system. Aluminum was used in 2 installations and 5 of the inspected systems were made of “normal” painted steel.

Experience shows that normal painted steel is not the best material for the mounting system. Corrosion can lead to structural damages and can be a potential risk for the system. The inspected installations using this material showed already signs of rust.

• We recommend promoting the use of either galvanized steel or aluminum to ensure a secure installation of the panels.

Materials used for the mounting system

Figure 7: Materials used for the mounting system.

4.2 Mounting typeThe most common way to install the PV generator is by using triangles. For installations smaller than 10 kWp it is common to use single row freestanding triangles for larger installations two or more module rows were common. This could be due to mostly flat construction of the roof and often multiple purpose usage of roofs such as leisure, storage, water tanks and drying clothes among others.

4.2.1 Single row free standing triangles

The space consuming PV system is often in conflict with other roof top uses. Especially if mounted with single row triangles (as seen in the picture below). The advantage of the single row freestanding triangles is the low wind load because the modules are very close to the roof and thus low ballasting of the modules. However this on the other hand, is in many cases also the downside because, the lower the modules are installed the higher is the impact of surrounding structures and consequently higher impact of the shading. Even if one module is shaded this can have a high impact on the whole string.

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Figure 8 : Single row freestanding triangles - horizontal

Figure 9: Single row freestanding triangles partly shaded by the surrounding wall in the morning hours.

4.2.2 Multiple row freestanding triangles

For larger installations (typically above 10 kWp) we found that the multiple row freestanding triangles is mostly used. The advantage here is space optimization. The disadvantage is a higher wind load and consequently higher ballasting of the mounting system. With such mounting structure, it is important to consider the self-shadowing of the rows. We identified two installations during our study where this was not taken into consideration. That can have a significant impact on the system yield.

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Figure 10: Partly shaded module by the front row. This small shadow has a big impact on the whole string.

4.2.3 Superstructures

As mentioned earlier superstructures are a good way to avoid conflicts with the other uses of the available roof top space. The systems we have seen using a roof top superstructure were among the best performing systems of the survey. All three systems using a superstructure were in the top 5 in terms of the system performance (Ranking on 1, 2 and 4). Part of the good performance can be explained by the minimization of the influence of shadow on the modules caused by other roof structures e.g. walls, columns or staircase roof structures. They also allow for a much better ventilation of the modules which also increases the performance. However, all systems using a superstructure were also using higher quality components in general (like the inverter and the modules).

Superstructures come also with some disadvantages. They are expensive, they have higher wind loads and are more difficult to clean. Still we expect using superstructures on small residential roof tops is the best possible way to install a photovoltaic system on a flat roof.

Most of these superstructures and multiple row freestanding triangles are locally manufactured and designed singular for every site. We believe that in the long run this will be replaced by predesigned set. The standardization achieved hereby will help bring down cost for structures and increase the safety and bring down installation time. These set should preferably be manufactured in India to make them available and affordable for local installers.

We recommend promoting the manufacturing of predesigned mounting sets in India to bring down cost and time of installation and increase the safety of structures.

Figure 11: Superstructures provide shade and avoid conflict in case of multiple use of the roof top space.

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4.2.4 Roof parallel installation on pitched roofs

Pitched roofs with tiles like in Europe are uncommon in India. However, there are some farm houses in parts of Delhi where such “European style” roofs are seen. During our study we examined one pitched roof with tiles.

Here the installation did not meet the European standards. Many tiles where broken and the modules and the cables were installed in an unorthodox way. The panels were not installed in line and there was no sufficient space to allow ventilation beneath the panels. It was obvious that the installer did not have much experience with such a roof. Here some training and knowledge transfer would be beneficial.

Figure 12: “European style roof”. The modules are not installed in line.

4.2.5 Module fixing / module clamps

In many systems the modules were fixed to the mounting structure by using the predrilled boreholes from the modules. This is a legitimate way of installing the system. However the world-wide standard in the industry today is using module clamps to install the module onto the mounting rails below. This is a much quicker way to install the modules and makes it easier to maintain the panels.

Some of the installations showed corrosion on those screws other were installed by using only a thin metal wire. Both can lead to severe damages.

Figure 13: Corrosion on the module screws and insufficient fixing methods can lead to destruction of the PV

generator and is a potential threat when falling off the roof in heavy weather conditions.

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4.2.6 Orientation and inclination of the modules

The inclination of the evaluated systems is between 18 – 26° and is in the recommend range. Here the knowledge of the installers seems to be sufficient. However, some of the installations were using different inclinations within the same PV generator. This can lead to yield losses if those modules are installed in the same string.

The orientation of the PV generator is typically linked to the layout of the building. This has both practical and aesthetical reasons.

We recommend to increase the awareness among the installers to have modules of one string installed at the same inclination and orientation. Or to use inverter equipped with multiple MPP tracker in cases where different inclinations at the same PV generator is necessary.

4.2.7 Shading

Some of the inspected system showed high impact of shading. We estimate that the systems with the highest shading influence had an impact of about 20 per cent yield loss. As mentioned above the reason for the shadow was most of the time caused by structures on the roof itself; e.g. satellite dishes, surrounding walls or the top roof staircase structures. We also find competing use of the roof top which could produce shade and influence the energy production.

The only systems where we had limited to no influence of shading were the solar roof superstructures (as mentioned above). Here we had the least shading impact and the best system performance, while at the same time alternative use of the roof top terrace is possible. The interviews showed that people who did not install a superstructure but a regular free standing system mentioned cost as the main aspect for their decision.

As mentioned we recommend increasing the awareness among the system owners as well as the installers of the negative influence of shading for the system performance.

Figure 14: The picture shows a roof structure which causes significant shadow to parts of the PV generator. This

has a negative impact on the system performance.

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5. Accessories

5.1 Cable tiesHow small things can have a big impact is shown by the use of the wrong type of cable ties. In Germany in the early days of the photovoltaic industry many installers did not use UV resistant cable ties. As a consequence the cable ties crack open after 1 or 2 years and the module or string cable will end up on the building floor. Here the cables are exposed to water and dirt and will interfere with alternative use of the roof top. The cable will also be more exposed the influence of wind, which could also lead to damages of the cable when the cable is repeatedly thrown against the sharp edges of the mounting structure.

This will decrease the life time of the cable and can in the worst case lead to severe injuries.

• We highly recommend the use of UV resistant cable ties to ensure the longevity of the system. UV resistant cable ties are available in the market. They are a little more expensive compared to the non-UV resistant cable ties. But here awareness of the installer in regards to this issue has to be increase.

5.2 PV Connectors (plugs)The standard PV plug has to be Ingress Protection IP 65 to ensure that there is no water going into the plug. There is no international standard in regards to which plug should be used. That means that within the same system multiple PV connectors (plugs) can be used. The module might have different connectors, as the connectors with the inverters and the connectors used by the installer might be different for the string cable (distance between the last and first module to the inverter). So it is possible that in the same system two to three different connectors are being used.

Some of the connectors need special crimping tools, which can only be purchased from the connector manufacturers. The most common PV connectors which we have seen during the examination were MC4, Tyco and Sunclix. Sunclix is a tool- less PV-connector which can be assembled without special crimping tools. We have also seen one installation where the plugs were not sufficiently crimped to the cable and came off after pulling slightly.

• We recommend to promote the use of tool less connectors or to give incentives to the installer to buy the regular crimping tools from the manufactures.

5.3 Cable type, diameter and cable conduitsThe most common cable type and diameter was 4 mm² PV-cable (in 10 out of the 15 systems). However in one-third of the installations 2.5 mm² PV-cable was used. The losses with 2.5 mm² cable are higher which affects the system performance and is not recommendable in installations of more than 1 kWp. Obviously the costs of 2.5 mm² are lower compared to the 4 mm² or 6 mm² PV-cable.

Another downside of using the 2.5 mm² is that those cables come with a thinner insulation. Since many cable are installed in plastic (non UV-resistant) conduits which are put down directly on the roof floor, the risk of breaking the conduit and as a consequence the cable is high especially when there is multiple use of the rooftop space.

This again could lead to system failure and can also be a health risk for people on the roof especially when there is multiple use of the roof top.

• We recommend to use 4 mm² PV-cable diameter as a standard for all roof top installations up to 10 kWp and 6 mm² for installation larger than 10 kWp to avoid losses and as a safety measure.

• WehighlyrecommendtogiveguidelinesonthematerialandpositioningofPV-pipeconduits.Theymust be installed using robust material and within areas where they do not break to avoid damages.

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Figure 15: Broken Pipe conduit on the roof can lead to system failure and can be a potential health risk.

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6. Grid Voltage The connectivity of the rooftop systems in India is governed by technical standards laid out by Central Electricity Authority. For voltage level below 33kV, where most of the small size photovoltaic systems are installed, the voltage operating window of the inverter should be under the operating range of 80% to 110% of the nominal connected voltage which is 230V in India. Beyond a clearing time of 2 seconds, the Photovoltaic system must isolate itself from the grid. In some areas we found that the grid voltage was higher than allowed operating range of inverters, leading inverters to shut down. Inverters have internal algorithms which check the grid parameters such as voltage or frequency.

The inverter also has pre-programmed parameters in which grid limits the inverter will operate. Those parameters are specific to every country.

If the grid parameters e.g. the voltage reaches the upper or lower limits of the inverter settings than the inverter will shut down. And will only turn on again when the voltage is back to the “normal” parameter.

• We recommend that the installer should check the grid parameters using a Net-analyzing-data logger for at least one week to analyse the voltage and other parameters.

• Awarenessneedstoberaisedofthenegativeeffectsofhighvoltagelevels.Itshouldbemadepossibleforthe Indian PV-installers to adjust the inverter settings flexible to the local conditions. The DISCOM should be able to give special approval in extreme cases when the local voltage level is above the nominal voltage range.

Those special approvals are a common standard with DISCOMs in other western countries.

The installer than should decide if the inverter parameters should be adjusted or if a voltage stabilizer should be installed.

• Measuresforreactivepowerregulationshouldbeconsideredandenforced.Thiscouldminimizeregionalvoltage issues.

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7. Remote monitoring systemRemote monitoring of the PV system is a way to analyze the system data from your smart phone or computer. Almost all inverter manufactures provide a platform where you can see the performance of your PV system. It provides the actual power output, daily, monthly and annual reports and sends alerts to phone or e-mail address should there be a malfunction in the system.

Regular monitoring is key to ensure a sustainable operation of the roof top PV systems. We have seen a remote monitoring system being installed at 10 out of 15 Installations. 4 out of the top 5 performing systems had a remote monitoring system installed. All 5 installations without a monitoring system were in the lower half in regards of system performance.

It could not be analyzed if and how often the remote data was evaluated by the system owner. But there seems to be a correlation between the best performing systems and the frequency of analyzing the remote monitoring system data via smart phone app or computer.

• Remote monitoring of the system and a connection to the internet should be mandatory for small roof top installations to assure a better monitoring and thus higher gross yields.

• InadditiontothatmeasurewewouldrecommendthattheDISCOMshouldsendanannualreportabout the PV system performance taken from the data of the generation meter compared to the projected annual yield. Similar approaches are carried out by European DISCOMs. In our perspective this is the best way to assure not only a certain target of the installed PV rooftop capacity in India but also to assure a steady and sustainable energy output of the rooftop PV systems.

Figure 16: Proposal for an annual report given by the DISCOM to help system owner understand if his or her installations

performing well or if measures of improvement should be taken.

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8. Maintenance contractIt is also important to have the system inspected from time to time. Although a photovoltaic system has almost no moving parts and is thus widely understood to be low maintenance, still malfunction of small components could potentially cause a total shut down of the system. In our study 3 out of the top 5 systems had maintenance contracts including the best and second best performing system.

• We would recommend mandatory maintenance contract with an annual inspection of the system. During this inspection the installer has to check the function and the safety of all components to avoid future shut down of the system or even health risk because of the electrical failures or problems of the mounting structure.

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9. ConclusionBased on the evaluation of our survey data we find that the quality of components used has a huge impact on the system performance. Especially the quality of the inverter seems to be the best marker for the performance of a system. Generally, the systems using high quality European-make inverters show better performance than other inferior quality inverter brands.

Ranking Site Monitoring system

Maintenance contract

European inverter

Installation on superstructure

Cleaning weekly

Privately owned

1. Site 82. Site 103. Site 64. Site 7

…

12 Site 1513. Site 9 *14 Site 3 *15 ** Site 12

Figure 17: Top 4 and last 4 systems ranked according to their system performance. There seems to be a correlation between the quality of the inverter, the cleaning frequency and the mounting structure and the system performance.

*Monitoring system was installed, but the interview showed that the owner did not sufficiently know how to handle the data. **

The owner was aware about the low performance of the system and intended to the take measures to increase the performance.

Are Indian PV-Installers sufficiently trained to install PV-Systems? The study showed an overall understanding of how to install PV systems. However, there is a need for additional knowledge transfer through trainings, guidelines and best practices for introducing the recommendations given under each section. Especially, training on best practice to avoid smaller mistakes, which can lead to significant increase in yields should be mandatory for the installer. The smaller mistakes in each phase of system planning & designing, installation and operation maintenance must be avoided. Some examples respectively include, selection of components and sizing, mandatory use of design software’s; inverter and cable positioning; and annual maintenance contracts & remote monitoring. In such trainings among others, the issues like underestimating the impact of shadow or dirt, the fragility of the modules and the impact of quality components on the system performance should be addressed.

What are the best measures to ensure a good and sustainable PV-performance under the local conditions? We would recommend increasing the overall awareness for solar energy, especially the consumer awareness. Renewables should become a topic in schools. As mentioned in section 6 a monitoring system for the solar installations should be mandatory. We saw that many systems underperformed heavily.

Although most of the system owners were happy with their savings many of them could not say how much they were producing or should have produced with their PV system. Therefore, it should be made very transparent for the consumer what its system is actually producing each month or annually and what the system should have produced in the same period. The installer should give a forecast of a certain annual energy output should and ensure that the energy yield is guaranteed over (at least) 10 years’ time (taking a normal digression into account). That would most likely increase the yield production of the solar roof top systems in India.

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We think that if the focus for the photovoltaic systems is too much on the price alone the quality of the systems which are installed will drop. So even if the installer is well trained and skilled the system performance will suffer if the components are of a low quality. We recommend opting for higher quality standards for inverter, PV panels and the mounting system. To be more effective, we recommend that the installer has to guarantee a certain system performance (kWh/kWp*a) in the next 5 years.

We also recommend that at the initial inspection of the system by the DISCOM before commissioning of the system should not only focus on the safe interconnection to the network but also ensure that basic safety and quality standards are met. This should include for instance the use of non-corrosive materials for mounting structures and safe positioning and installation of cables and conduits.

The license/empanelment of the installer should be tied to regular refresher course including latest technologies in the market, the latest regulations and best (and worst) practice studies.

Deutsche Gesellschaft fürInternationale Zusammenarbeit (GIZ) GmbHPhotovoltaic Rooftop ProjectIndo German Energy Programme

Registered offices: Bonn and Eschborn, GermanyB-5/2, Safdarjung Enclave, New Delhi 110 029 IndiaT : +91 11 49495353E : joerg.gaebler@giz.deI : www.giz.de

Mr. Joerg Gaebler, Principal Advisor

Jan Stasik - AWASOL GmbHjan.stasik@awasol.com

Abhinav Goyal Dirk Simon

Jan Stasik, Abhinav Goyal

BSES Rajdhani Power Limited

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