Solar energy in hot and coastal climates

The Caribbean region and La Guajira are among the highest solar radiation areas in the country, which translates into more generation for every kWp installed. In terms of solar resource, it is one of the best areas of Colombia for solar energy. IDEAM's Solar Radiation Atlas is the reference for looking up the specific value for each region.

That potential is why many projects, residential as well as commercial and industrial, are especially attractive on the coast.

There is also a favourable overlap in the consumption profile: in a hot climate, a good share of energy goes on refrigeration and air conditioning, and that equipment runs precisely when there is most sun. That synchrony between generation and consumption improves direct use of the energy, which is the most valuable way to use it.

Counter-intuitively, panels lose some efficiency when they get very hot. It is not that heat damages them, but that the higher the cell temperature, the lower its instantaneous performance.

The capacity shown on a panel's datasheet is measured under standard laboratory conditions, with the cell at 25 °C. On a Caribbean roof at midday, the cell works well above air temperature: the panel absorbs radiation and heats up, and it is not unusual for it to exceed 60 °C even when the ambient temperature reads 33 °C.

The panel's temperature coefficient indicates how much capacity is lost for every degree above that 25 °C reference. On current silicon modules it usually sits between -0.26% and -0.40% per degree. The arithmetic is direct: a panel with a coefficient of -0.35%/°C working at 65 °C loses around 14% of its nominal capacity at that moment.

That 14% is not a disaster — the area's high radiation more than compensates — but it does explain two things: why real output always comes in below nominal capacity, and why in a hot climate it is worth paying a little more for a panel with a better coefficient. Over 25 years, that difference adds up.

Heat cannot be eliminated, but the design has a considerable influence on how hot the panel gets.

Ventilation underneath is the most important thing. A module separated from the roof, with air circulating behind it, runs appreciably cooler than one mounted directly against a hot surface. That is why roof-integrated installations, with no air gap, perform worse in a hot climate despite looking neater.

The colour and material of the roof also count: a dark metal roof radiates heat towards the panels and raises their working temperature. And mounting height helps: a few extra centimetres of separation improve air circulation.

When choosing equipment, besides the panel's temperature coefficient, it is worth reviewing the inverter's operating range. An inverter installed in full sun with no ventilation reduces its output to protect itself when it overheats, and that limiting happens precisely during the hours of highest generation. Locating it in the shade and ventilated is one of the most profitable decisions in the project.

A marine environment accelerates the corrosion of metals. Near the coast, mounting structures, fixings and certain components are exposed to faster degradation than inland.

Exposure is not the same everywhere: it decreases with distance from the sea and depends heavily on the prevailing wind direction. A building on the seafront receives a far higher salt load than one a few kilometres inland, and that difference should be reflected in the material specification.

In practice, this means choosing quality aluminium structures with the right treatment and stainless steel fasteners, avoiding mixes of metals that encourage galvanic corrosion at the point of contact. Panels designed for these environments pass specific salt mist resistance tests; asking the installer for that certification is a simple way of filtering equipment.

It is also worth attending to the small details: junction boxes, cable glands and the inverter itself must have a suitable protection rating, and their location — sheltered from direct sea breeze — considerably extends their life.

A tropical coastal climate adds three factors that do not appear in a highland project.

Sustained humidity encourages water ingress at poorly sealed points and contributes to degradation phenomena associated with the array's electrical voltages. A well-executed installation, with connectors from the same manufacturer correctly crimped and sealed, is the best prevention.

Wind defines the anchoring. Structures have to be calculated for the wind loads of the area, including suction effects at the edges and corners of the roof, which are greater than in the middle. This is a structural calculation, not a catalogue choice, and it is one of the reasons the installer's local experience matters: someone who has seen what holds and what does not on that coast specifies differently.

And lightning. In areas with frequent electrical activity, surge protection stops being optional. A photovoltaic system adds metal surface and wiring at the highest point of the building, so earthing and protective devices have to be properly resolved. It is a safety requirement under the electrical regulations and, on top of that, it is what stops you losing the inverter after a storm.

The maintenance plan on the coast is not the same as inland, and the proposal should reflect that.

Salt settles on the glass and, not being washed off by dew or light rain, forms a film that reduces light transmission. In areas with strong sea breeze, cleaning frequency rises compared with what the same installation would need inland.

The periodic inspection must explicitly include checking for corrosion: the condition of the bolts, of the contact points between different metals, of the roof anchors and of the junction boxes. Catching corrosion early is cheap; discovering it once it has already compromised a fixing is not.

It is a good argument for contracting an annual plan with a local installer, who knows the real rate of deterioration in that specific microclimate.

When getting quotes on the coast or in a very hot climate, there are details worth putting to the installer. Answering them precisely is, in itself, a sign that they have worked in these conditions before.