PVDC PV+ Grid Voltage Monitor Test Report

Ending 24th June 2016

Foreword

This document has been compiled by matt:e Ltd to provide evidence supporting the viability of installing the PV+ Grid Voltage Monitoring Unit onto photovoltaic systems in the UK.

All data used in this report has been collected over a 12 month period using test systems installed at the matt:e offices in Tamworth Staffordshire.

This data should not be offered as a guarantee for increased solar generation for all solar PV systems, as the results from fitting a PV+ is dependent upon individual circumstances and therefore, may be higher or lower than the figures stated.

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Why do I need a PV+ Grid Voltage Monitor unit?

According to a recent report carried out by Western Power Distribution, over 50% of our homes and businesses are now supplied at a voltage above 243.8V, with nearly 7% of these being supplied with a voltage above 248.8V. Solar PV inverters have to raise the voltage (typically between 2 and 6 volts) higher than the incoming voltage in order to push the generated energy around the property or back on to the grid. Where high incoming voltages are present, this leads to premature system shut down through over voltage, causing loss of system generation.

The generation graph below (Fig A.) shows Omnik 3kWp inverter clearly showing loss in generation throughout the day. These losses in generation were caused by the system shutting down during peak generation times and were directly linked to the high voltage recorded in the property (Fig B.)

Fig A. Fig B.

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How does the PV+ help?

By monitoring the incoming supply voltage rather than the inflated inverter voltage, the PV+ Grid Voltage Monitor Unit allows the Solar PV inverter to compliantly stay in circuit for longer which prevents nuisance over voltage shut down, and allows the system to generate for longer. This will speed up the return on investment for new and existing systems alike.

Please note, matt:e do not recommend installing a PV+ device where the incoming voltage is lower than 244V.

System Overview System 1 non PV+

Afore HNS2000TL-1. each connected 8

x 250W Solar Panels.

OB100 Owen Brothers generation meter

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Expected generation using Libra Energy Pulse Design Software

System 2 With PV+

Afore HNS2000TL-1. each connected 8

x 250W Solar Panels.

OB100 Owen Brothers generation meter

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Results

The systems were commissioned on 24th June 2015 and have been left to run without interruption until the 24th of June 2016.

Final meter readings taken:

System 1 Non PV+ 1558.66kWh

System 2 PV+ 1744.97kWh

As shown in the table below both systems easily outperformed the expected generation however, the PV+ unit achieved an additional 186.31kWh or 11.95% compared to the system without the PV+ unit fitted.

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Predicted (kWh)

Actual (kWh)

Inverter run time (hrs)

Increased Generation (kWh)

Percentage increase

System 1 Non PV+

1321.3 1558.66 3676 237.36 17.9%

System 2 With PV+

1321.3 1744.97 3866 423.67 32.06%

Increase 186.31 190

Percentage increase

11.95% 5.1%

Conclusion

While the additional 11.95% increase is significant in monetary terms, especially for the early adopters on higher FiT rates, it should be noted that this test was carried out on an industrial estate where heavy loads on the local grid significantly lowered the voltage during the working week, meaning that the high voltages impacting the inverters were mainly experienced in the evenings and at weekends. A typical domestic property should receive steady voltages throughout the daytime, and therefore, should expect a higher increase in generation where high voltages are present.

This theory is supported as most of the increase in generation was gained during early evening after local factories had stopped production but mainly during weekends when they are closed.

It would be fair to assume grid voltages in residential areas would be more consistent during the day, therefore in areas of higher grid voltage, inverter off times would be more frequent meaning further loss on generation

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