solar panels

The failure of solar water heating

Jul 5, 2009
  • Article by Tone Wheeler

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 five percent 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.

But while the technological issues of solar water heaters were overcome, and mass production and better manufacturing techniques reduced their price, the public nevertheless resisted installing them. I think this was largely because the design of the overall system was woeful – aesthetically and functionally.

No manufacturer made an effort to visually integrate the design of the solar system into Australian houses. On the contrary, they were often finished in bright aluminium or polished stainless steel, not coloured to match the roof, and had garish manufacturer’s signs across the entire tank. There isn’t a single other house product that has taken this aggressive approach to branding. No wonder some Councils baulk at their potential visual pollution. Sydney’s Leichhardt Council, for instance, has a policy mandating solar water heaters, while at the same time prohibits them from being visible from the street. This highlighted the contradiction that faced most home-owners and designers: while the contribution of solar water heaters was valuable, they were so ugly that installing them required a separate frame mounted at the rear of the house to hide them. This in itself brought with it its own problems – the panel was often overshadowed and hence less efficient, and was just as unsightly when viewed from the private open space of the house.

No manufacturer made an effort to visually integrate the design of the solar system into Australian houses. On the contrary, they were often finished in bright aluminium or polished stainless steel, not coloured to match the roof, and had garish manufacturer’s signs across the entire tank. There isn’t a single other house product that has taken this aggressive approach to branding. No wonder some Councils baulk at their potential visual pollution. Sydney’s Leichhardt Council, for instance, has a policy mandating solar water heaters, while at the same time prohibits them from being visible from the street. This highlighted the contradiction that faced most home-owners and designers: while the contribution of solar water heaters was valuable, they were so ugly that installing them required a separate frame mounted at the rear of the house to hide them. This in itself brought with it its own problems – the panel was often overshadowed and hence less efficient, and was just as unsightly when viewed from the private open space of the house.

More problematic than the aesthetics was the impracticality of installation: the builder had to reinforce the roof and crane the unit in, and then the plumber had to install half a dozen or more fixings to hold the panels and tank in place, together with multiple penetrations through the roof for the hot and cold water pipes and the booster connections. This was all to be performed on Australian roofs, which are predominantly comprised of fragile terracotta or concrete tiles. Likewise, this presented a problem for installation and maintenance on older, brittle roofs, making retrofitting, the Holy Grail for sustainability, much less attractive.

The elegance of an integrated design was more than offset by the clumsiness of installation: a good idea in theory, but terrible in practice. Two generations of plumbers, the most expensive sub-contractor on a building site, became disenchanted with the attractions of solar water heating. What is even more amazing is that the manufacturers persisted with this design for over 40 years, spending their time seeking government rebates and support rather than looking at the failures of their own product.

Fortunately, the predominant design has changed in the past five years: panels are better designed or have evacuated tubes, still vulnerable to hail, but so much more efficient that they will work on a wider range of roof angles and orientations, eliminating the need for a bulky frame. Equally important, the tank is now separate from the panels and is located on the ground where it is more easily installed and maintained, and where instantaneous gas boosting is appropriate.

Given that water-heating is the single largest producer of greenhouse gases in Australian housing, the installation of a gas boosted solar water heater should be the number one priority for our governments. It is the single most effective way to get a dramatic reduction in energy use and greenhouse gases (E2G2), a reduction that is being demanded by the Kyoto Protocol. Uptake of the technology would happen almost overnight if coal-fired energy were priced for its environmental cost but that would require political courage that, as we observed last issue, is sadly lacking. So we have to look to government subsidies for encouragement, but in Peter Garrett’s recent announcements ‘insulation batts’ (which will do nothing to reduce E2G2) have taken precedence over far more worthy initiatives for solar water heaters.

Now that the aesthetic, design and technological failures are overcome, Australia needs a coherent program to promote solar water heating for 95% of its dwellings, particularly in widespread suburbia, which has access to sunlight on almost every roof. Ten years from now, travellers arriving by plane should remark on three things: the red terracotta roofs on the houses, the blue swimming pools and the black solar water heaters offsetting the energy demands of the former two.

Conversation • 21 comments

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09 Jul 09 at 7:10 AM • Geoff Little

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.

11 Jul 09 at 1:40 AM • Peter Johns

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.

13 Jul 09 at 7:07 AM • Dan Hill

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.

21 Jul 09 at 8:17 AM • IAGD Interior

Great article. Love it. Make sense.
Malaysia is a neighbour to Australia, I belive I see a similar situation…

24 Aug 09 at 6:28 AM • Bruce Longhurst

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

17 Sep 09 at 12:07 PM • Steve King

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……

26 Nov 09 at 4:25 AM • chris

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.

09 Feb 10 at 11:08 PM • Mark Harwood

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.

13 Mar 10 at 7:47 AM • Sean Hughes (Skyline Energy)

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.

22 Nov 10 at 11:41 AM • bella

The reason why these hot water heaters (i use the term loosely) are loosing favour is because they are bloody rought with problems and the manufacturers (in particular Rheem) don’t want to fix them even under warranty. Some jobs that do occur have to be paid for by the consumer and the out of pocket expenses add to the ongoing cost of the thing as well as negating any cost benefits that may have been acheived if the solar hot water service actually worked on solar. Bloody big joke. If i had my time over again i would stick with electric because that is the main power i use to heat my water even though i have a solar unit. I live in a very sunny environment and i use night tarriff all the time.

04 Aug 11 at 1:34 PM • david

my Rheem lowline has been a dog I have always had intermittent hot water but it has been hard to find the cause and Rheem have been no help at all. Finally the impeller failed Rheem have know about this problem but keep it quite, the impeller shaft rusts causing the pump to stop now and again so you get poor hot water performance and you don’t know why .Your panels will be left baking in the sun with no or little circulation you will find that the replacement part will cost heaps and is not covered by warranty one year only on that part ,The replacement impeller will have a ceramic shaft to avoid the same problem and now the cylinder has a rust spot inside causing a rusty discharge , The hot water system is only 4 years old I have spent more money on this heater in the last 4 years than I did running my previous off peak hot water which lasted 14 years and it provided proper hot water Thank god I never recommended one to anyone.
I found out that this information from my p v installer who knew all about the pump failures and if you search Rheem solar water heaters reviews for australians you will find that the panels are just as bad .

22 Dec 12 at 10:56 AM • Peter Field

I have a 250L tank powered by offpeak 1 (nightrate) electricity and costs me $58 per quarter GST inclusive. I bought it just before they were banned so it’s going to last me a few more years before I have to replace it. Under current conditions I would opt for a gas no tank system. I have found that these are inexpensive to buy and run and don’t take up a lot of room. I like the idea of solar but I can’t see how the cost is justified. There would have to be a dramatic change in design and cost before I would consider having one installed.

09 Jan 13 at 1:58 PM • Pieter

Excellent article. If any government of any political persuasion is serious about wanting to cut the CO2 emissions of Australia, SHW is an absolute no-brainer. They could probably easily achieve their targets given water heating accounts for about 25% of a household’s energy use.

28 Jan 13 at 10:03 PM • Mary Reilly

I installed a Solarhart Black Chrome II (Melbourne) in 2000 & it has been brilliant. Solarhart, now Rheem performed a retrofit on a thermostat, at their request, and replaced a valve at 7 years that should only have lasted 4-5y. The unit is not automatically elctrically boosted; instead I turn on the electric boost via the Circuit Breaker and generally only for 10-20 minutes when needed (very infrequently). Very happy with the system. Will be building again this year and will definately be going solar HWS again.

23 Aug 17 at 8:59 AM • thomas horn

i have one too..what a great unit..98% free hot water..

14 Feb 13 at 10:28 AM Lesha Helgren

I agree, but everyone needs to acknowledge that adding Solar to their house is an purchase that will boost the long term worth of their house if / when they decide to sell. With the environment the way it is going we cannot disregard any product that offers totally free power at no cost to both the customer and more importantly the environment!

24 Jul 13 at 10:05 AM • andrew

i have the the solitaire solar hot water split system works fine, except in in winter here in Victoria on those few frost days/mornings.

the tap end explodes off from the frost, water rushes down the gutters and eaves. seems there is no cure. even with the expansion valve , im told by the company, it will dump hundreds of litres of water.

so now every winter it is disconnected. not happy.

25 Jun 14 at 1:21 PM • Vivienne

I recently paid for an expensive solagain HWS unit and realise that the advertising was in fact just good marketing. It is constantly boosting, in other words runs on electricity. The cost savings are minimal? if not non existent and not worth it. I’m in Perth and had 3 months of very very hot days, with no “piping hot water” as advertised, unless my booster stayed “ON” this caused it to over heating, and dump the whole 300l out the over flow pipe (So much for the booster turning off) They came out, turned it down, now if I want hot water the booster has to remain on even in the height of summer I pay $100 – %150 every 60 days on my power bill for solar hot water every day, even if it’s not used. I proved this by turning off the booster in February and putting up with warm water. Power bill dropped by $150 dollars. Waste of time and money .. I should of gone for instant water, then I’d be paying only for the hot water I used. Remember quoted savings of UP to 80 – 90 percent of you hot water costs, actually means savings from ZERO to 80 or 90 percent, there is no guarantee there is really any savings, as your paying for boosting 24/7 even when you don’t use it … I’d never buy an over priced Solar Hot water system again …

31 Jan 15 at 5:32 AM • Armand

I am from New England and have had a closed-loop Solar Hot Water system on my home for the last twenty years. The good news is it has worked. The bad news the high failure rate of the hybrid hot water tanks has eliminated any potential cost savings it provided. My system is based on a large capacity (119 Gallon) stone lined tank that uses 2 x 4500W heater elements combined with a single integrated exchanger. I have gone through multiple tanks and have made the decision to toss in the towel on this effective, but not cost effective alternative.

08 Jun 15 at 1:07 PM • bryan

My experience with solar HWS has been pretty good.

We have had two units since we moved here in 1988.
The first one replaced a 3 phase Electric instantaneous heater which was hopeless.(they drop a phase & produce lukewarm water)

It lasted for about 19 years then needed a new tank.
A bit of a leak,not the hundreds of litres others have reported.

Probably would have been better to replace it all,as the other bits failed after another 6 years.—-Probably should have done more maintenance.

Got a new one in 2013,which will probably last as long as I will-plus!

No problem with the weight of the unit—but we build REAL houses in WA!

just as a test,we went through one year with the booster turned off.
Hot water all winter!
I’m pretty certain there is no timer system for the booster–it runs off a thermostat like ordinary Electric storage systems.

It isn’t pretty-unfortunately pretty & efficient don’t go well together!

17 Mar 17 at 1:47 PM • Dieter

Thanks for the interesting article. As a former owner of a slit system I can predict this solar hot water systems will never take off.
Reason : The warranty is only 5 years (they brake down short afterwards) against the roof mounted with 10 years warranty( but who wants a heavy unsightly unit on the roof),
In short, instead of spending money on a replacement tank I got for about the same amount a heat pump system and haven’t looked back. In my life definitely no solar hot water, if a industry can’t get the act together in 40 years they don’t deserve support.


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