The Solar Digest for Solar Power, Solar Energy and Photovoltaic PV News - Test and Measurement
New Solar PV Test Installation Verifies Module Quality and System Performance
- Published: Friday, 08 March 2013 19:24
Advanced Seaward Solar PV test instrumentation is helping a successful Caribbean based reseller and installer of solar photovoltaic and thermal systems to verify the quality of PV modules and the performance of installations.
Comet Solar is an established solar installation company based in the British Overseas Territory of Anguilla. With some of the best beaches in the world, the local economy is largely focused on tourism and Comet has been successful in encouraging local hotels, resorts, property owners and businesses to invest in solar systems as a means of helping to offset the effects of the economic downturn on tourism levels and rising energy costs.
Chris Mason, owner of Comet, explains: “Cost is very important to our customers and so we tend to look for PV modules at bargain prices.
“Without any subsidies or incentives and facing aggressive resistance from the utilities, solar has been a difficult sell. It is only because the cost of electricity is US$0.433 / kWh that we have any customers at all. At that rate and if we had net-metering, our payback on solar PV systems would be about 3 years.”
Comet customers therefore tend to focus on price and return on investment, with aesthetics often being low on the list of purchasing factors. However, buying bargain priced solar PV modules brings its own challenges; second hand or refurbished modules are often used, but, in some cases the life history of the modules or the original manufacturer is not always known.
Another issue is the lack of formal installation standards or regulations. For example, operating in a Caribbean jurisdiction means that Comet is not specifically required to perform the same tests that a UK or US based installation company would be faced with.
However, in spite of this, in the interests of maintaining installation quality, Comet always aims to apply and meet the existing standards of the US NEC code and to perform to the best practices of the industry.
To help achieve this the company has recently invested in a dedicated new Seaward Solar PV150 solar installation test kit, along with a 200R irradiance meter, to enable it to carry out effective quality control and customer reassurance testing on its products and installations.
The Seaward Solar PV150 is a dedicated multi-function PV electrical tester designed specifically for solar panel system installation. It performs open circuit voltage measurements (Voc), short circuit current measurements (Isc), earth continuity, insulation resistance, operating current (via AC/DC current clamp).
With the push of a single button the new combination tester carries out the required sequence of electrical tests in a safe and controlled manner, avoiding the risk of contact with exposed live DC conductors. Results can be recorded and stored in the tester for subsequent USB downloading to a PC.
Chris Mason, explained: “In order to ensure the quality of the products we sell to our customers, we feel it is important to carry out testing thoroughly and effectively.
“We owned standard test instruments and DC clamp meters but found that these manual methods were prone to error and were not particularly practical to use in the field. There is also no efficient way to record the results. We therefore decided to find a portable but capable test system that would document the performance of each module in a recordable way.”
Recently Comet was offered a container of 170W used monocrystalline solar panels and used them on a 12 kW commercial flat roof top system.
These PV units had been replaced on their original system due to yellowing of the backing but were in perfect electrical and mechanical condition. As the modules were used, Comet tested every unit prior to installation to make sure of the quality and safety of the modules and also to prevent any subsequent dismantling of the installation for any troubleshooting required.
To do this Comet set up an improvised test bench at the installation site and tested every module as it came out of its packing. All testing was carried out during the middle of the day so as to make use of full sun for testing. Every one of the 66 modules were tested individually and no issues were found, with all units performing as expected with little variation between the modules and no ground faults or open circuits.
Importantly, the speed of the test system allowed comet to perform full tests on each module without impairing the workflow of the installation crew.
The test data for each module was downloaded and given to the owner as a system spreadsheet to reassure him that testing had been carried out thoroughly to verify the quality of the modules and to confirm the anticipated performance levels of the system.
Comet’s latest solar PV installation project is much larger and so requires a different test regime. The company is currently installing 500KW of Canadian Solar 240W modules, purchased directly from the manufacturer.
As these are Tier 1 Grade A modules, Comet won’t be pre-testing every module, but will test each string at the combiner before installing fuses.
Working to US NEC requirements does not does not allow for easy testing of the installation in the way that typical UK systems do. The wiring is always in conduit and the combiner circuits are hard wired, so there is no easy way to test installed strings on larger systems.
For these larger projects, Comet will therefore be using 1000V rated test leads with alligator clips.
Chris Mason said: “Using the PV150 system on an installation in front of the client gives a sense of security that the installers are professional and are doing the project properly.
“We are seeing the emergence of some less than professional installers in the region who perform poorly crafted installations, test nothing and do not give the customer any comfort that the work is being done properly.
“We invite our customers to witness the commissioning tests with the PV150 so they can see how much work goes into our quality assurance procedures. This is both a marketing tool to enhance word of mouth referrals and protection against liability from call-backs.
“Documenting system performance at commissioning gives us a baseline against which to retest in the case of a complaint or problem, both with customers and manufacturers. For this use alone, the test kit and reporting system is invaluable.”