CAN YOU TRUST YOUR DATA? A CAUTIONARY TALE!

For Cambridge-based Artisan Electrics, a company that prides itself on observing the highest professional standards, it looked like a straightforward project. The company had been contacted by Nimbus Hosting, a specialist in eco-friendly web hosting, with a request to install a battery system to capture surplus energy that was being produced by its solar power installation. Nimbus Hosting had supplied Artisan with data covering the twelve months since the solar panels had been installed and, on the face of it, this showed that the panels were producing a healthy surplus of power every day.

Based on this data, Artisan engineers sized and designed a battery system, and were ready to proceed with installation. Before starting work, however, they carried out a preliminary site visit to carry out the final checks that would ensure the work would proceed smoothly. As would be expected, this included checking on the arrangement of the solar power installation. This produced something of a shock – but not of the electrical kind!

Artisan discovered that the CTs monitoring the power used by Nimbus Hosting had been installed in the wrong place. They had been fitted in a sub distribution board where they only measured a fraction of the total power being used by the company. This instantly suggested that the surplus of power being produced by the solar panels might not be quite as healthy as the data supplied – in good faith – by Nimbus Hosting.

To accurately determine the real situation, Artisan temporarily installed a Chauvin Arnoux PEL103 power and energy logger in Nimbus Hosting’s main distribution board. This was done rather than simply re-positioning the incorrectly installed CTs because installation of the PEL was fast and easy, but because it could be depended on to provide reliable results, and because it would provide more comprehensive and more detailed data than the original set up.

Within just a few hours, the results provided by the PEL were a revelation. Far from producing a large surplus of power, Nimbus Hosting’s solar panels were, almost all of the time, producing far less power than the company was using, making it a net importer of energy from the grid. It seemed that there would be no surplus power available to charge the battery during daylight hours and the company’s idea of using the battery to power its operations during the hours of darkness would therefore be unachievable. in place for a month uncovered a rather more complex and more interesting picture. The first and most obvious finding, discovered in the first week of data logging, was that the building heating had been left on over the weekend, wasting a lot of costly energy. This issue was quickly addressed.

More interesting was the discovery that on Saturdays and Sundays, there was indeed a modest surplus of power from the solar panels which could potentially be captured by a battery installation. Since the data had been captured during October, it was also possible that even better results might be obtained during the summer months when sunlight levels are higher and the hours of sunlight are longer. However, this could only be confirmed by extended monitoring through the summer.

The data from the PEL also showed that, while the phase voltages were closely matched, the phase currents were not, with one phase being almost twice as heavily loaded as the other two. This indicated that if a battery system were to be installed without other changes being made, a three-phase system would not be appropriate. Instead, separate single-phase battery systems would need to be used for each of the three phases so that the difference in loading could be taken into account.

After analysing the plethora of data captured by the PEL in detail, using the supporting software supplied by Chauvin Arnoux, the engineers at Artisan were able to make some soundly based recommendations to Nimbus Hosting. The first was that with the present arrangements, installing a battery system would be likely to bring only small benefits, even in the summer months. However, as Nimbus Hosting has unused roof space, fitting additional solar panels would transform this situation and, with the aid of a suitably configured battery system, help the company to achieve its ultimate objective of completely eliminating the need to draw power from the grid.

Based on data from the PEL, Artisan also advised that it would be advantageous for Nimbus Hosting to consider reconfiguring its loads to achieve a better balance between the phases. This might allow the use of a three-phase battery system, which would be simpler and less costly than using separate single-phase systems.

In this case study, reliable data provided by a Chauvin Arnoux PEL103 has prevented a costly mistake based on incorrect information. Had the battery system originally planned for Nimbus Hosting been installed, it would have been significantly oversized because a large energy surplus had been predicted, and it would have been of little practical value.

The moral of the tale is that it always pays to monitor power systems with instruments of known accuracy before carrying out modifications – monitoring is an inexpensive exercise and, with a purpose-designed instrument like a PEL103, it can be carried out without disruption or inconvenience. And, as in this case, it might just deliver some very big savings! www.chauvin-arnoux.co.uk