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Data collection demonstrates the value of solar PV

Posted by greentomatoenergy . on 19 February 2014 at 9:02 am

A recent solar PV blog on YouGen highlighted the importance of making sure that your solar PV system is well managed, well designed and well maintained. We thought we’d illustrate this message with a case study of a solar PV system we installed in a 3 bedroom semi in Hertfordshire at the height of the solar PV rush in December 2011.

The system comprises of six 240W Sanyo panels and an Eversolar TL1500 inverter. It has consistently performed slightly better than estimated.  Our conscientious client monitors output using the high tech method of collecting meter readings each week and recording them on an Excel spreadsheet. The graph shows what she found.

Unsurprisingly, output is very dependent on the weather.  For example, remember that we had a great Spring in 2012 and the solar PV output reflects this.  Overall the solar PV array has performed slightly better than predicted, with an output of 1,145 kWh in 2012 and 1,124 kWh in 2013. It was designed using PV sol with an estimated output of 1,061 kWh per year and a SAP output of 1,021 kWh per year.

Our client ensures that the panels are washed with water and a soft cloth regularly. The data demonstrates how remarkably predictable solar PV is as a technology, performing almost as predicted for two years after installation. 

The importance of monitoring

Not only has this monitoring enabled us to analyse the system's performance, it means that any major fault in the system would have been noticed straight away, and that it could have been rectified quickly, keeping losses to a minimum.

Collecting monitored data will also make potential warranty claims easier in the future, as proof can be given of the system’s performance.

Effect on overall energy costs

Our client also provided us with consumption data.  Her annual grid electricity demand has been reduced by a massive 42%. This means that she is buying 42% less electricity from the grid. As a result she is less exposed to electricity price rises and is saving money by using electricity generated on her roof. 

Installing the PV system has increased the client’s awareness of electricity usage.  She changed their energy consumption habits so that as much as possible of the generated electricity is used.  For example, she uses the dishwasher, washing machine and vacuum cleaner in the middle of the day rather than in the evening.  

It turns out that the installation of the solar PV  was  only the start of the energy revolution at our client’s household.  Having looked at the data coming out of their solar PV system and comparing it to their fossil fuel consumption, she realised that she could do more to reduce consumption in the home.  Energy efficient light bulbs and loft insulation have since been installed using the financial benefits arising out of the solar PV system.

By changing their behaviour our clients are benefitting even more than expected from the system. When calculating the annual financial return from the measured data rather than the predicted data, the annual return increases from 7% to 9%. The feed-in tariff payments amount to 48% of the annual energy bill, meaning that that the average spent on energy in 2012 and 2013, when you take away the feed-in tariff payment was only £600 – this is only £50 a month!

...the benefits of collecting data

Solar PV is a reliable and predictable energy source on an annual and even monthly basis. Provided that the system is properly designed, installed and maintained, the annual financial benefit is certain and if you’re game, you can take the example of our client and use the income to generate more savings or improve comfort at home, making your returns even higher! All this has been made possible due to the collection of big data, allowing homeowners to take control of their own energy consumption.

Author: Clara Bagenal George

More information about solar PV on YouGen

The YouGen guide to solar electricity

From the blog

How do I know if my solar panels are working correctly?

Comparing the performance of solar PV panels (2011)

How to keep your solar panels clean

Images provided by greentomatoenergy

About the author: greentomatoenergy specialises in cost-effective renewable technologies and low carbon building.

If you have a question about anything in the above blog, please ask it in the comments section below.

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2 comments - read them below or add one


rhsComment left on: 27 February 2014 at 8:16 pm

I notice that the amount produced by various photovoltaic systems varies by some margin. From the UK figures on  the actual annual yields of those I have calculated can vary between 70% and 101%. Presumably this depends on aspect, slope, shadowing, etc. of the installation. The best I have found so far comes from a 3.60 kWp system producing 3647 kWh in a year. Our system in Worcester is rated at 3.85 kWp and this has produced 3762 kWh, 3629 kWh and 3734 kWh over the last three years, which averages at 3708.3 kWh. This calculates to 96%, which is a pleasing amount above the estimated annual generation given by the installer and by  Now if I could cut down all the growing trees of our neighbours ……

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rustyComment left on: 27 February 2014 at 10:41 am

By my calculation, in 2013 your installation produced 0.781 kWh for each installed Watt.   (1124 divided by 1440)

My installation in Berkshire (just down the road) produced 0.950 kWh per Watt, a  large difference.

My system was newly installed in December 2012. Could its outperformance be due to its newness? I wouldn't like to think that deterioration is as rapid as that.

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