Blessed with the most annual sunshine in Europe, the Algarve is ideal for solar technology. This, set in a context of rising bills and a movement towards energy-efficiency and a cleaner environment, means that more and more Algarve homeowners are nowadays turning to the sun.     

Solar energy now offers a practical means to heat your domestic water and/or your pool. Here we focus on domestic hot water systems. Whether a single-panel with 150 litre tank or two panels with 300 litre tank, two basic configurations are available:

Thermosiphon systems:

The water tank is mounted together with the solar panel(s), typically on a roof or roof terrace.  As the name implies, these systems work because hot liquid rises and cool liquid descends. As the liquid circulating within the solar panels is heated, it rises and gathers in the tank. The cooler liquid at the tank's bottom descends back into the panels for heating.

Forced Circulation systems:

The solar panels are mounted in a similar place but the water tank is located remotely, typically in a ground floor / basement utility room or outside cupboard. A pump system is therefore required to circulate the water to/from the panels, plus further pipework / ducting. Whilst more expensive, these system are often preferred for aesthetic reasons (the panels alone on the roof are more discreet) as well as practical reasons (the tank is easier to maintain and may be utilised for other applications (e.g. radiator or underfloor heating).   

Both types of system have a back-up electrical element, which automatically switches into action when there is insufficient 'solar gain' (i.e. cloudy weather, night-times etc).

Whether thermosiphon or forced circulation, the best systems are in fact 'closed circuits', using an anti-freeze solution which circulates around the panels and into an outer jacket of the tank. In this way, the water in the tank is warmed indirectly via a heat exchange process.

There are also thermosiphon and forced circulation systems available in simpler, 'open-circuit' format, whereby the water itself circulates around the panels and directly to the storage tank. But the Algarve's poor water quality, with its high calcium content, means that such systems can become quickly furred-up, inefficient, and even completely blocked unless given regular maintenance.

Even closed-circuit systems can be subject to failure in the Algarve's intense summer heat, as pipes and joints may expand and leak, requiring topping-up of the antifreeze solution. Again, regular maintenance is critical, which many owners fail to ensure. Solar specialists Penguin report that many call-outs for broken-down solar systems occur when the electrical back-up element inside the tank fails; at which point it emerges that the fluid had in fact completely leaked away months before, and the system had been operating entirely on its back-up all that time - with no solar heat being generated at all.

Chris Blackburn, Penguin's Director, advises a simple precautionary test: “Run several baths or just drain the hot water away in the early morning - i.e. before the sun has had effect – and turn off the electrical back-up at the fuse box. Then wait a day (with sun) to see if the panels are heating the water.”

Solar systems are often claimed to be around 75% efficient – i.e. the other 25% is generated by the electrical back-up system, on cloudy days or at times when demand for hot water reaches a peak. But this is an optimistic ratio, failing to account for non-typical patterns of hot water usage. For example, it only applies if the occupants of a house all take baths/showers in the morning, allowing the solar system to re-heat the water during the day. But this pattern of usage may be impractical to many, who prefer to bath at evenings - resulting in the electrical back-up system working overnight to re-heat the water.  

The pattern of usage therefore has a significant bearing on the return-on-investment (ROI) a solar system may offer. Let's take a typical example of a townhouse occupied by a small family – say a couple with one child, where gas-generated hot water typically costs about €40 per month. A good solar system – and be wary of cheaper ones, they are less reliable and have a considerably shorter lifespan – will cost around €3500 to install (300 litre thermosiphon system). If we say that the typical pattern of usage by this family results in 60% of hot water generated free by the sun – i.e. a 60% saving on energy bills – they will save €24 per month. The ROI is therefore about 12 years – perhaps not as compelling as some sales pitches would have you believe.

Chris Blackburn agrees: “Return on investment is a valid consideration but is not the main one in deciding to purchase a solar system. However, as traditional energy costs rise, this will become a more influential factor. Beyond that, there are still several persuasive reasons for installing a solar system, not least the greater self-sufficiency in producing hot water from free energy; plus the fact that a property with solar installed also gains a superior certification rating, which in turn increases its marketability. From a wider perspective, there's obviously a hugely worthwhile environmental incentive too.”

“Overall, there's no doubt that solar systems are the way forward, particularly here in the sunny Algarve. But in order to consistently gain the maximum benefit from them, they must be properly and regularly maintained.”

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Heat pumps, heat exchangers, and solar pool heating across the Algarve - Jandy, Heat Siphon, Zodiac, and Heat Perfector.

Heat pumps or heat exchangers are the most efficient, trouble-free way of swimming pool heating. Heat pumps run on electricity and emit absolutely no exhausts that pollute the air – they are low NOx by definition.

They work by extracting heat from the air and transferring it into the pool water. Since the air is always warm when the pool is in use, it is the perfect and most efficient use for a heat pump. Heat pumps are so efficient at transferring this heat that they operate at a lower cost than natural gas.

Enjoy warm pool water this summer with an efficient, non-polluting heat pump.