Maintaining solar PV systems can be a good source of business and customer peace of mind, writes ‘The Shadow’.

The maintenance of domestic solar photovoltaic systems is a neglected area.

It’s an area in which a business-like approach to householders might give a skilled person the chance to render a service and make some money.

On the economics – other than ‘grandfathered’ feed-in tariffs of about 60 cents per kilowatt/hour – a 12-panel installation will potentially earn about $600 a year, or reduce the energy bill by that much.

Battery storage could substantially increase these savings. Based on a period of 20 years, the savings for a non-storage system are about $12,000, but with a drop in installation efficiency this would come down dramatically.

The owners might imagine themselves doing the planet a favour, but they would not be doing that very effectively or see an economic benefit.

A check-up every two years might be annualised at $150 for labour, and installations more than four years in service would be candidates.

PV panel and inverter efficiency is the main aspect to consider. PV panels degrade, and manufacturers’ specifications state the fall in efficiency over time. The inverter does not degrade slowly over time, but it can suddenly lose conversion efficiency. Householders wouldn’t be aware of this, except maybe when the electricity bill arrived.

Other problems that can occur with grid-tie inverters may require grid voltage monitoring, as inverters are allowed to operate only within a voltage range of 204V to 268V. This is a particularly nasty problem in relation to the upper voltage limit, when inverters cut in and out because of voltage spikes. It is an ’unseen’ problem in that the inverter is sound but little or no energy is being fed back to the grid.

This is not directly a service problem. However, by doing a test on an installation – particularly one in a street of PV installations where the problem is likely to be prevalent – a contractor can alert the owners to contact their energy distributor.

Sudden failures are quickly checked by testing the inverter’s AC output. Failure or degradation of the DC link is usually because of the electrolytic capacitor. There’s not much to be done on the spot, but the inverter can be returned to the authorised service depot.

Panels sometimes degrade faster than expected. Thin panels are more subject to induced degradation than thick panels. Voltage across the cells with respect to the grounded frame causes a drift of sodium ions in the protective glass and affects cell performance.

Testing all this is ‘hairy’, but doing a rooftop inspection, armed with a DC tongue tester, will allow the DC power to be measured and can put the owners of the PV installation at ease that the panels are doing their job.

On the other hand, the failure of some cells on a panel may be apparent. Timely replacement of a panel or panels is very important and can be subject to renewable energy certificates being available to discount the panel cost.

In summary, the combination of a DC test and AC output test, of themselves not difficult to perform, will indicate the basic health of the PV installation