Totally tubular-choosing the right solar water heating panels, especially for the extremes of central otago

22 March 2016
Time to read: 5 minutes

Considering that the cost of electricity is rising faster than inflation, that about 35% of average household energy use is attributed to water heating, and that the payback period for installing solar panels is as low as 7 years, any new home builder is wise to consider tapping into this clean, free energy source.

The decision to go solar is easy, but how to do it is less so. Plenty of research on the subject exists. In fact, it’s as plentiful as sunshine. Separating out the helpful and pertinent from the outdated and not-so-relevant is key.

Talking to experts like Regan Heal, General Manager of Infinite Energy NZ, out of Cromwell, is vital to deciding what works best for here. Heal not only knows the technology of solar energy, but he’s also well versed in the particulars of using it in Central Otago.

When asked to weigh in on the long standing debate between flat plate versus evacuated tube panels, he is unequivocal in advocating the tubes. His reasons exemplify why relying on professionals who know the particular area you live in is of utmost importance, whether it’s looking into building an energy-efficient home or an individual component therein.

Heal recommends evacuated tubes over flat plate collectors for their superior performance & efficiency as well as two reasons specific to the region; the frost and the hard water.

He readily admits that both technologies are perfectly adequate in certain situations and that “a bit of opinion” gets involved in anyone’s recommendations. Nonetheless, considering these two factors, he advocates the tubes.

Understanding how both systems protect themselves against frost reveals why one performs more efficiently.

Flat plate collectors are most commonly installed as a direct system – pumping or circulating the water in the cylinder up to the roof where heat transference occurs.

The alternative, evacuated tubes, can more readily be installed as an indirect, or closed loop system (providing your cylinder has a coil) which works by pumping an anti-freeze glycol through to the roof where it heats up and then transfers that heat to the usable water via the coil, though never coming into contact with the water in your cylinder.

Evacuated tubes afford greater peace of mind during our hard Otago frosts because there is no chance of the glycol freezing no matter how low the temperature dips.

The same reason explains why the hard water of our region makes a closed loop system a better choice.

Under extreme heat, deposits form in the water, which can eventually compromise the performance of direct systems. There are ways of mitigating this factor, but opting for evacuated tubes installed via a closed loop means less maintenance.

Are there any drawbacks to evacuated tubes? Depends on the importance of aesthetics versus efficiency. All solar water heating systems should be installed at an optimal angle to the sun for year round efficiency (this angle should be the same as your latitude).

Installing for optimum efficency means the system may be more visible and distinct from the roof.

Just as there is personal opinion involved in deciding which type of panels work best, so is there personal preference. Which type depends on many factors; deciding is made easier, however, when all the factors are pertinent to the individual making the decision.

This is why consulting experts, which is one of the helpful services Evolution provides, not only in the field, but also in your field, or back yard, means you get information that relates specifically to you.

Regardless of which type of panel suits your lifestyle and home best, most everyone agrees nowadays that pursuing solar energy in some form is the right choice all around.

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