Components and installation

If the amount of kVA allowed for the house sets a limit, a much bigger limit often is the available space for solar panels.

These can be placed on the ground or on the roof, but have to face as much southwards as possible or be in a combined east-west configuration. Even more important is being free of shade.

Solar panels produce direct current, or “DC”. This has to be changed to alternating current “AC” for the house, which is done by a so-called inverter. Which brings us, once more, to different options. Some systems work with small “micro-inverters” on the back of each panel. Panels are then placed parallel to each other and directly feed AC from the roof down to the house. Other systems place panels in series, so-called “strings”, feeding one large inverter, that usually sits inside the house. The first option has the advantage of panels being parallel whereby shading on one panel does not hamper the others. But a big disadvantage is the placement of sensitive electronics on a roof, where it can easily suffer damage. And worse: If one panel fails, one may not notice it immediately. So regular inspection becomes advisable for this kind of installation. Furthermore, these systems will always inject all surplus energy into the grid. And that requires a bi-directional meter to be supplied by EDP.

The second system has several advantages above the first: It is more efficient for leading a higher voltage through the cables from the roof, it has no exposed sensitive electronics on the outside, and it does therefore not require special or regular maintenance. Apart from that, the centralised inverters usually offer more management and monitor options.

Mentioned central inverter should ideally sit in the house or garage or even in a special box, but always in a moist free and ventilated, space. The same applies for eventual batteries. Apart from that there will be two safety boxes, one for AC and one for DC, as well as a smart-meter. All that stuff ideally will not be too far away from the main switchboard.

Cabling is another issue. Between the panels and the inverter, heavy DC cables must run in an exclusive, not shared, conduit. When going through the ground, they should be placed in a special 80 cm deep trench with netting and a warning lint on top. When coming down from the roof, they must be protected in a suitable housing.

From the inverter to the main switchboard goes another heavy cable, being an AC one. And finally, a thin internet cable should be connected between the smart-meter and the router in the house. All this can be lead in discrete housings running on the outside of the walls, but will still be visible.

The only alternative to that is to grind channelling for the hiding of conduits, fill those up with cement and paint them over.

Obviously, this calls for the recommendation of timely planning for anyone who starts refurbishing or building.

Selling surplus energy back to the grid is an option, but bluntly put, for individual households the prices obtained lately do not justify the bureaucracy involved. Economically speaking it is better to focus on the return-on-investment by the supply of energy for one´s own consumption. Maybe this will change in a future when the grid infrastructure can better handle return loads, and also when energy companies find better ways to store energy.

Via the smart-meter one can measure how many surpluses eventually occurred, and see when a contract with the grid supplier and the installation of a bi-directional meter becomes interesting. Apart from this meter to be supplied by the energy company, no further adaptations are required from most PV-systems.

Honest advice

Anyone who buys a system too small to cover all energy requirements knows two things for sure: One is that electricity will still have to be bought from the grid, but the other is that the system bought will at least be used for a hundred percent. Each and every panel will, after all, help to reduce bills.

And yes, by reducing the energy bought from the grid one also helps to protect the environment. So, starting with the wish to save money is not so selfish after all.

Often forgotten in the equation is the raise in real estate value. Price comparisons between identical houses have shown that such raise is often higher than the investment in the PV-system installed.

Very important is also to know that all PV-systems in Portugal need to be inspected and certified by a classified engineer. Not only is this obliged, but it is also important for the purpose of insurance, and of course for one’s own safety in the first place.

Serious PV-system suppliers take care of registration and certification for their customers.

The general conclusion from the three articles dedicated to the subject is that both facts and fables exist around solar panels. Fortunately, in most cases, enough positive facts help to overcome eventual disappointments of too high expectations.

What it comes down to is the need for honest advice, as well as open and sober listening ears.

by Hans Mulder

Hans is a Dutch citizen who helps a local supplier of PV-systems to answer the high and growing number of daily quote-requests from Algarve residents. The above text reflects the most common doubts and curiosities he encounters while providing advice and suggesting solutions.

For the Dutch-speaking community, he will be guest speaker at a webinar organized by the NCA Association, to be held May the 9th starting at 7pm. Information can be obtained via