Member Comments

I've got a 30-vacuum-tube solar system, with a 350L tank sitting immediately above the tubes (- the top of the tubes actually go into the tank). The bulk stored water, actually goes inside the vacuum-tubes and is heated directly (so the energy collection is 100% efficient). This system needs no heat-pipes, nor pumps, nor electricity to run, it is all just a big thermosyphon.

There is an integrated 30m copper heat-exchanger coil inside the tank, and water coming out of the taps flows through the heat-exchanger and is automatically mixed with cold, to ensure max of 55°C at the outlets.

There is an electric element and electronic controller, than can be activated to boost the bulk water up to whatever temp you want in the cylinder, upon reaching desired temp it will automatically turn the element off. This 'autoboost' can also be programmed to start every day (say 4pm), to ensure it reaches a certain temp every day with minimum electricity used.

The only losses in this system are from the tank/bulk water storage to the surrounding air, but this is minimal due to the 60mm'ish moulded polystyrene insulation between the inner and outer tanks.

On a sunny day you can get a 40°C rise on 350L (= 16.3KWH equivalent). More typical during winter, is a 20°C rise (= 8.2KWH equivalent). There have been days when the whole tank is at 99°C and the vent is steaming. It's been going for a couple of years now and provides over 80% of the hot water for a family of 4.

You have indicated what regular maintenance could be expected with solar panels, but has Consumer Inst done any research on the lifespan of the solar panels available in NZ - ie how long before any unit would need to be replaced because of normal wear and tear and therefore what long term cost efficiency could be expected given the number of years solar panels have been available in NZ.
Mike Atkinson

We've had the leaky home crisis, and now are we suffering the beginnings of a solar water-heating rort? Comments below refer to solar water heater problems. And its possibly widespread - see this website: http://www.healthandlifestyle.co.nz/solarpanels/index.html Could the gurus at Consumer please let us know whether they are doing any work on this potentially major problem?

I'd like to see Consumer take the initiative with this. We can't count on BRANZ or the government sorting out the problem proactively: look at their record - they let the leaky homes problem develop (for anyone who reckons things have changed in terms of solving systemic building problems, you must be joking - its the same team, only different jerseys).

We need an truly independent organisation advise us whether we have a solar water-heating problem.

Great info but test results and consumer satisfaction survey results for the types of solar hot water systems which are available, will help a lot. You have done it for heat pump water heating why not for solar?

Solar hot water systems have been around for a number of years in NZ. When are we going to see test results and consumer satisfaction survey results from the Consumer Institute, for the types of solar hot water systems which are available here?

I could not afford to buy a complete solar heating system outright so I purchased a solar ready cylinder first and then the evacuated tube system later. The cylinder is a Superheat brand and was purchased new from Thermocell. It has an internal coil and electric element for boosting the temperature if required. The tube system is a closed loop glycol type due to the freezing levels over winter for inland North Otago and was purchased from Mirak who have been incredibly helpful and did a quality installation. I am impressed with how well the evacuated tubes work in our area. Unfortunately, the cylinder failed just after one years normal use i.e. before the tubes were even connected so heating was sole by the electric element. I had endless trouble with Superheat but they did repair the leaking cylinder over a period of two weeks for free or so I thought (having no hot water and a young family for that time was not fun). In just over a year after this repair, it failed again and I could get no satisfactory support from either Superheat or Thermocell without paying them something. They had many excuses and didn't really want to deal with the issue. I got fed up with them both and had a local tradesman inspect and repair the cylinder at my cost who found two faulty welds. He advised me that the copper was probably not annealed correctly when manufactured and it would most likely crack again. I was not happy mainly because I was originally going to purchase a stainless cylinder but was talked out of it by the sales person at Thermocell as this would prolong the time it would take for me to save for the solar heating arrangement and delay the pay back time. It made sense then but now, I am currently saving up for a stainless cylinder to replace the copper one as I do not trust it will last. I think I have made a loss here but time should ease the pain. So before purchasing a system, I recommend talking to other consumers who have had a system for a couple of years and find out how there experiences went, I didn't.

How do you choose between closed or open loop? A vendor of either will tout their own so which works best?

I wish Consumer would update this report and give us their own evaluation of the system that is best for various zones around the country...