Feb 8, 2015: In all sorts of hot water

Last week I wrote about a couple of revolutionary projects that might lead us to rethink the way we design and build shelters. Meanwhile, during this year of monitoring and evaluating the performance of the Greeny Flat we are doing a lot of thinking about what we could have done better in the design and construction of this little house. I’m pleased to report that there is very little that we would change if we were starting again but there is one major thing that we would do differently.

No Solar Hot Water

This might come as a surprise to some readers but we would very likely not install a solar hot water (SHW) system, certainly not a split system like we currently have, and definitely not anything made by Apricus.

What’s wrong with a Solar Hot Water System?

The main problem with the particular SHW system that we purchased is that it was extremely expensive. After much deliberation we selected a ‘top-of-the-line’ split system with an Apricus APKR-20 Evacuated Tube collector, an Everlast Series 2000, 160ltr storage tank, a DeltaSol BS/4 Controller and a price tag of about $6250. There a many cheaper systems on the market and, in future, I might consider using a less expensive option, at least to pre-heat our water. But, if you’ve been following the results of the Greeny Flat experiment , you’ll know that we are making way more energy than we are using. What we could really use is a way to store some of that energy during the day for use at night. The simplest way to do that would be to heat water. If we didn’t have this super-fancy and expensive solar water heater, we could simply use our excess electricity to heat a tank full of water during the day for use at night. In effect this would still be a solar water heater we would just be converting the sunlight to electricity first, then the electricity to hot water. This would be somewhat less efficient but much simpler and less expensive and it would help us to reduce the amount of electricity that we export to the grid. We only get paid 8c/kWh for what we export and we pay 22c/kWh for what we import so it’s better for us to make use of the electricity directly rather than export it. In short, the SHW system we have is way more complicated and expensive than it needs to be.

What’s wrong with a split Solar Hot Water System?

There are a lot of different types of SHW systems which are described in detail in the Wikipedia article on solar water heaters. In Australia there are two main types available: ones that have the tank attached to the top of the collector panel (called ‘close-coupled’ systems); and ones that have the tank separate from the collector panel (called ‘split’ systems). As you can see from the images below, it’s easy to tell the difference when you see a SHW system on a roof because the close-coupled system has a big tank on top and the split system doesn’t.

Split SHW system with ‘flat plate’ collector and tank on the ground. Note the complex system of pipes, wires, pumps, controllers, etc, required to make this work.

Close-coupled SHW system with evacuated tube collector. Note the simple and natural ‘thermosyphon’ system that makes this work.

The other thing you can glean from these images is that the split system requires a complex arrangement of pumps, controllers, valves and piping to make it all work whereas the close-coupled system is much simpler and works by the natural tendency of hot water to rise (called the thermosyphon effect). So, in future projects I might consider using a close-coupled system to pre-heat the water but I’d be very reluctant to use a split system again.

What’s wrong with Apricus?

Apricus has a very good reputation as the Australian leader in SHW technology. Their website makes them sound like a wonderful company to deal with. Their ‘Core Values’ are listed as:

• Building strong relationships with customers.
• Providing the highest quality product.
• Providing the best possible support.
• Having the “good bloke” factor; Going above and beyond for our customers.

Sounds good doesn’t it? The trouble is that, at least in our experience, they haven’t lived up to any of these promises. In fact:

• There are some serious shortcomings in the design of the product, particularly the lack of a user interface for monitoring and control of the system and the poor design of the smaller storage tank which we were forced to use due to the low height of the available space above our bathroom.
• We have made many attempts to raise these issues with Apricus and have met with a very poor response.
• Their customer service is almost non-existent.
• Most of the ‘good blokes’ at Apricus that I have tried to contact haven’t even bothered to reply. The ones that have responded have been very slow and their responses have generally been unsatisfactory.

In short, I would never use an Apricus product again.

So what would we do next time?

Next time I will most likely do the simplest thing possible that would still allow us to use the sun to heat water. That probably means that I would simply have a good, old-fashioned, electric tank water heater with an element. This is simple, tried and trusted technology that every plumber understands, can install and repair. It is also silent and has no moving parts so requires minimal maintenance. I would set this up on a timer to run between 10am and 2pm every day which is the period of maximum production from our solar power system. Since we seldom use any other electricity during the day this would allow us to store a lot of our excess power in the form of hot water.  To summarise, such a system would be:

• Inexpensive to install
• Inexpensive to operate
• Silent
• Easy to maintain
• Easy to repair
• Easy to understand

If I had a good place for it with easy access I might consider using an inexpensive, close-coupled SHW system with a flat plate collector to pre-heat the water on sunny days. Of course on cloudy days we would be using grid power to heat the water but that is true now with the expensive and complex solar hot water system that we currently have.

And so we live and learn…

February 8th, 2015 | Category: Andy's rantings, Energy, Environmentally Sustainable Design, Green Building

6 comments to Feb 8, 2015: In all sorts of hot water

• Mark

  February 9, 2015 at 7:57 am · Reply

  Hi,

  Sorry to hear your dissatisfaction (Perhaps that is too strong a word) with the SHW setup.

  We’ve got an Apricus split system, and had a generally positive experience with it. Aside from wanting it to collect more sun in the depths of winter we are quite happy with it.

  I think there are a couple of advantages of the split system, which might only apply in some situations. Firstly you don’t need to support the weight of a water tank on the roof, which means there are places a split system could be used that a close coupled can’t. Personally I’m glad we just have a collector on the roof as I’ve had to do some work up there, but this is not a common requirement.

  Additionally since most of the plumbing is at ground level (tank, controller, relief valves etc), it can have maintenance advantages. There is also the benefit of being able to replace a single tube if there is a breakage I guess.

  Certainly though the close coupled system seems more “elegant”. Powered by the heat it’s already generating!

  I can understand why you’d go for close coupled in the future, but I’m interested to know why you would prefer flat plate? Is it just because of the price/performance value? I’ve not seen any great information with an objective comparison between the two (and they seem to mostly be tied up in supplier deals as to what is recommended), but I had understood the evacuated tube should absorb heat more effectively.

  Having excess hot water should be seen as a blessing though – not so much use in summer (unless you can use it to power an absorption chiller?), but you could use it for hydronic heating in winter.

  The idea of direct element heating from solar PV kind of makes me shudder at the inefficiency – you could at least maximise the amount of heating with a heat pump system, but you do lose silent operation with no moving parts.

  • admin

    April 25, 2015 at 6:44 am · Reply

    Mark, thanks for your thougths and sorry to be so terribly slow to respond. I greatly value reader feedback and I try to acknowledge it and answer question as quickly as possible. Unfortunately your’s slipped through the cracks.

    It’s now a few months since I wrote this post and we have, finally, received some customer service from Apricus. They sent out a very nice fellow and made some changes to our systems so that it works a bit better for us. I’m still not particularly happy with it as it has been boosting fairly regularly and we’re not even close to winter yet. But at least I now have a way to monitor the tank temps and I can tell if the PTR valve gets stuck open (things I couldn’t do before).

    Having given this whole problem a lot more thought I still feel like I would never use a split system again unless I really had to. I don’t know what the best solution is to be honest. I totally appreciate your comments about the improved efficiency of both the evacuated tube systems and heat pumps. It’s the cost and complexity that I don’t like and the fact (or perhaps it’s just a feeling) that evacuated tubes are much more likely to break in a hail storm than a flat panel. Nevertheless I’m still of the opinion that a close-coupled system with an electric element booster timed to run when there should be some power coming from a PV system (cloudy weather is the obvious problem with this idea… when you don’t have hot water, you also don’t have much solar power) is likely to be the least expensive, simplest, quietest, and least likely to give trouble in the future. Plus you have the option to add a ‘bolt-on’ heat pump to an element tank heater in the future if you want, or need, more efficiency. Heat pumps and split systems are just too complicated and expensive. The trouble is, they are also more efficient. It’s a dilemma that I continue to struggle with and would appreciate any further thoughts you might have. Andy

• Dominique Guillot

  November 18, 2015 at 12:21 am · Reply

  HI, I, also have exactly the same issues as you have described above with my Apricus system. I purchased the system in april 2015 (gas Boosted) and has never worked since, the storage tabnks cannot retain any hot water, period. Four experts had a look and cannot find anything wrong with it.I’ve given up on their customer service (hopeless)$6.5K later, I am now using more gas than ever before in other words i am worst off now.
  I like the idea of using the solar panels to heat the water during the day.
  This was my two cents

  • admin

    November 18, 2015 at 7:03 am · Reply

    I’m very sorry to hear that. Since I wrote that post I was finally able to get someone from Apricus in Sydney who knew what they were doing. They reconfigured the settings on our system and changed a few things and now it is working very well. I still feel like it was too much to pay but at least it works and we don’t have to worry about it.

• Doug Foskey

  June 18, 2017 at 5:54 pm · Reply

  Hi,
  I had a friend refer me to your site. I am building 2 of units for persons with disability in Lismore 2480. I used a different approach for the PV power: I installed 13Kw of PV with a 10Kw Fronius inverter. I will use an electronic switch to dump power to the storage style Hot water services when it might be exported. Even though this is less efficient, because PV panels are cheap, it is more economical than all the extra plumbing involved with a ‘wet’ HWS. Once the water is heated, any extra unused power is exported. (fyi, it takes 10-12Kw to heat the average HW for 2-3 people, so an additional 1.5Kw of solar panels is adequate.) This could be used with a heat-pump system, but I feel the extra complexity is unwarranted. I fitted 2400 watt elements to my HWS so I could use a 15A power circuit (then my smart box plugs in). The switch is here:
  MK2PV.org in UK, although commercial switches are also available..

  • admin

    July 15, 2017 at 6:39 am · Reply

    Thanks Doug, were you able to get this through BASIX as a solar water heater?