Response
The failure of solar water heating
Tone Wheeler
06.07.09
Why has the solar water heating industry struggled to make an impact in sunny Australia?
In the 1950s, two countries led the world in the development of technology for heating water from the sun: Israel and Australia. Both countries were developing a simple thermosiphon solar water heater, a system that had been pioneered in California and Florida in the 1920s. Given the plentiful sunshine in both countries it seemed a ‘no-brainer’ that this technology would be quickly developed and implemented.
Fast-forward 50 years: in Israel there is hardly a building that doesn’t have a solar water heater; in Australia less than 5% of houses have one. The question must be asked: both countries started out with the same enthusiasm, technology and access to sun, why did Israel succeed and Australia fail? Most commentators believe that the answer is financial: with the cost of energy in Australia so cheap, and the cost of a solar water heater so expensive (at least in comparison to an electric or gas storage heater) there is little financial incentive to install solar. The internal rate of return (IRR) of six to eight years was always considered too long, but that is a silly argument: no-one asks the IRR of a stone benchtop over laminate, and the water heater would last at least twice that time to deliver savings to the current (or next) owner.
Another reason given for the failure in market penetration was administrative: that there was never the government regulations or incentives to install solar, as there had been since the 1970s in Israel. Rebates were state based, and periodic, while mandatory installation requirements were sometimes Council based with no national or state based coordination. Those incentives that were in place were confused and poorly promoted.
But the real failure was one of design: the technology was never well resolved and the design was never suited to Australian houses and conditions. The most common solar water heater was an integrated tank model: using darkened flat plates, usually copper and about two to three square metres in area, behind glass, to heat the water and a tank mounted horizontally above the absorber to store it. As the water in the absorber was heated by the sun it would warm and rise up the sloping panel into the tank, at the same time drawing down cold water from the tank into the bottom of the panel to be heated, a closed loop setting up a circulation system known as a thermosiphon. Simple and self-regulating, easy to manufacture, at first it appears a very elegant solution.
But there are technology failures. In cold frosty conditions the water in the absorber can freeze, bursting the copper plate. The solution, using a separate circuit of liquid with an antifreeze agent, increased the initial price and created problems of cross contamination in the early models. Hailstorms, more common in Australia than in the Middle East, can also wreck the panels even if the glass is laminated or tempered.
One of the most vexing problems stemmed from the fact that a booster of electricity or gas was needed to provide energy in cloudy conditions. The problem was that the booster system would never know when the sun was about to come out, or when the users were about to use the water, so the system had a timer to heat the water overnight in case there was early morning demand for hot water. If there was early morning sunshine, or the owners showered later in the day, then the solar energy input would be wasted with an artificially heated tank. This problem was eventually resolved through instantaneous gas boosting, which takes advantage of all the solar heating and only heats the water that is not hot enough.
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The following 9 people were compelled to have their say. We encourage you to do the same.
Solar also includes heatpump as defined by ORER for RECs. Demonstrated lowe recurrent costs than solar in many cases, lower installed cost in most cases. Quantum as pioneer, struggled for years now have hit the big time. Good product, appalling company. Siddons Solarstream, good product good company yet to hit the big time- watch this space! Rheem/olahart/Edwards heatpumps poor performers need boost elements. Dux, looks good but has issues. Saxon, HE system restricts temp maintained output flow rate, Stirebel Eltron, not a contender. Note none yet have low GWP refrigerant such as R290, using R417, R134A mostly. No real commitment to low emission future.
Interesting article thanks. I’d never stopped to think why the take-up of solar water heating has been so poor. Other factors that prevent uptake are residents’ associations in Truman Show villages, and body corporates (mine won’t let me touch my north-facing roof). Also clients seem to want PV panels these days, despite the high cost and low payback.
Great article. Love it. Make sense.
Malaysia is a neighbour to Australia, I belive I see a similar situation…
Thank you for article. Explained a lot. Another point is that solar collectors, of all sorts, are extremely unexciting in a ‘consumer’ sort of way; I remember a friend, having installed an extremely expensive solar set up, at the BBQ we were all invited across the road to try and neck twist to see the technological marvel on his roof, well, the excitement must have lasted all of 15 milliseconds before we went back to beer and snags. Had the equivalent amount of money been spent on a motor vehicle . . .
At my place I have no mains connection of any sort, so solar is of interest to me. I have built my own hot water thermo siphon (from second hand bits and stuff from my local irrigation supplier), the idea came from an old CSIRO pamphlet that I came across decades ago and the idea never left me. Thought I would find out more, drew a blank, had to design my own -not as simple as it appears, but by Mk.3 (yes, I have built 3 crude hot water systems, pain in the bum) I now have hot showers. The main benefit of your own energy systems is something that is very difficult to explain, how do you tell people about something you Don’t have ? i.e. quarterly bills. I am not saying that alternative energy is a wonderful way to go, there are draw backs as with everything, the weather forecast tends to affect my living -having to work with mother nature as a partner is not to everyones taste and yes modern tech now has workarounds, but its still all a bit expensive, very Unexciting, and combined with a bureaucracy that has no imagination and a desperate desire to maintain the status quo, it gets close to being a complete waste of time. And then there’s water tanks, which governments loathed for decades as a breeding ground for mozzies, however most mozzies breed in uncleaned gutters (-which are also a severe problem in bush fire times), no government interest whatsoever, also having worked on a number of building sites and been present during building inspections I have NEVER seen the fall on a gutter being checked -all you architects out there be careful with your roof designs !! with changing climate you can expect Dengue and Ross River to become a commonality in Sydney and Melbourne and malaria is only a windgust away. Yes, not on topic, but the design of something as simple as a gutter can increase mortality in ways you wouldnt expect
Tone, while you begin with a comparison of Australian and Israeli interest in solar hot water heaters, and zero in on the aesthetic problems in Australia, you say nothing about the aesthetics of the ubiquitous roof units in Israel.
While Australia headed off in the direction of trying to sort out the technical production of integrated units, and flirted with subsidising their understandably high price, the Israelis legislated the requirement for every household to have SHW (think seat belts in Oz), and figured out how they could be best made for the least cost. The result was an open system of separate components, on a strident frame like a Russian constructivist roof decoration. Ugly as sin as an individual item. But when on every roof, they became the accepted and characteristic silhouette of the Israeli settlement. Worrying about them became about as useful as railing against the seatbelts spoiling the look of the inside of a car……
i just came back from china
a huge number of the roofs there are covered with exactly these units which is an incredible energy saving given the amount of households in china.
Sums up my experience very well. I installed a solar hot water unit (tank and panels) 22 years ago near the Victorian coast and less than 2 years later sold it to a cousin living in Darwin after suffering inadequate hot water and increased heating costs (no off peak heating available for such units back then!). I have recently installed an evacuated tube system and have not looked back. No boost heating has been required so far (summer) and I only anticipate occassional need for boost heating over winter.
Beware of turning off your electric booster!
you open yourselves and your families to the real risk of bacterial infection. Solars are great at overheating the water in summer, (what a waste!) but get this: Once you heat the potable water in a storage tank beyond about 35C you need to regularly (daily) heat it to at least 55C to kill bacteria. Please do some research on this guys.
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Dan Hill said on July 13, 2009 17:07
Good article, thanks. The image accompanying the piece looks almost exactly like the unit on my roof. I’d expand your point to address the overall design aka service design, design thinking aspects etc. – including legislation, service design, user experience (why no informatic feedback loops such that on a cloudy day I can access the system’s output levels from a webpage so I know whether to switch on the booster when I get home? Or control it from there, for that matter), cost models etc. – as well as aesthetics. Either way, I’d happily swap the red terracotta roofs you describe for an entire roof system i.e. the airborne visitor looks down and sees almost every roof entirely ‘productive’ with solar or greenery … that would be a fine vision.