Sustainable Living Tasmania member Warwick Moore’s electricity use for hot water over summer was slashed by more than 95%! How? He was the lucky winner of an Apricus solar hot water system at the 2011 Sustainable Living Expo.

I had been thinking about installing a solar hot water system and PV panels for some time. I had formed the opinion that a solar hot water system was the single most effective way to reduce my electricity consumption, with obvious benefits for the environment, as well as to reduce my power bill. I had also attended John Todd’s course at the Hobart U3A on home energy consumption and he had supported this view. He had pointed out that Tasmania was the only state that still allowed the installation of archaic, electric storage hot water systems, the most inefficient of hot water systems.

The Sustainable Living Expo provided a great opportunity to talk to a number of solar suppliers in one location at one time. I spent several hours at the Expo talking to various businesses and it was a very productive visit. The discussions confirmed my research that an evacuated tube system was the best system to install and I arranged for several firms to provide a quote.

As I left the Expo I was asked if I had time to provide some feedback about the Expo. As a member of SLT, I was happy to do so, especially since my visit had been such a productive one. I was told that I would be entered in the members draw for a solar hot water system but, with my luck, gave it no further thought until I was contacted several weeks later.

I was particularly pleased that my prize was an Apricus evacuated tube system, one of the two brands of evacuated tube systems on display at the Expo. The local Relationship Manager, from Apricus, was very helpful, providing me with details of the system and sending me copies of the installation and user’s manuals, as well as a list of approved installers.

My installer suggested several additions to the system I had won. As my north-east facing roof has an elevation of only 18 degrees, I needed a high pitch roof frame to elevate the tubes to 50 degrees, to maximize the system for winter insolation. He also suggested I upgrade the control unit to a SolaStat Plus 2 with a relay, that automatically activates the electric booster when water temperature drops too low. Without the automated controller, the booster must be managed using a manual switch.

His other major suggestion was that I request an upgraded cylinder – from vitreous enamel to stainless steel. Stainless steel has the benefit of a much longer life and it allows the water to be heated to 80 degrees, ensuring a longer time for the temperature to drop to a level where the booster is activated. Water above 50 degrees goes through a tempering valve, where it is mixed with cold to deliver a constant, safe 50 degrees maximum. The high tank temperature and the use of the tempering valve provide the potential for hot water to last through a day or two of cold cloudy weather (unless exhausted by use). I believe it was worth paying the extra cost to upgrade the tank.

The installation of the system took place in late January over a period of two days. My old tank was due for replacement and it was removed on the first day. The new tank was installed and the electric boost was connected. The electric booster provided me with hot water that night. On the second day the evacuated tubes were set up on the roof frame and the pipe-work completed. The solar tubes raised the temperature of the water in the tank to 61 degrees at the end of the first full day of operation.

Until my system was installed, our hot water power consumption averaged 15.2 kWh (kilowatt hours) per day (2010-2011 figures). Surprisingly, the average for the summer quarter was highest at 16.1 kWh per day, perhaps reflecting extra hot water consumption due to relatives from overseas staying for a protracted period. It also may reflect more showers in the hot weather.

The solar system was installed on January 25 and, at the time of writing, has been in operation for 33 days. During this time it has used 24 kWh of electricity in total. This includes 3 kWh to heat the initial intake of water and five occasions when successive cloudy, colder days activated the automatic electric boost – the maximum being one 5 kWh boost (ambient temperature was 13 degrees on that day) and the minimum only 1 kWh.

The system has a pump which circulates cold water onto the roof and through the manifold into which the evacuated tubes are fitted. Pumps generally use a lot of energy so I was concerned about how much energy the pump would use. Over the 33 days, the pump consumed a miserly 3 kWh!

So far the system has used an average of less than 0.75 kWh per day for the 33 days compared to the previous summer daily average of 16.1 kWh and the annual daily average of 15.2 kWh, clearly a huge saving. Unfortunately, the Aurora hot water tariff includes a fixed daily charge of 17.266 cents per day irrespective of the quantity of energy used. After a full year of operation of the solar system, it will be interesting to determine whether it might be better to have the electric booster connected to the more expensive light and power tariff, in order to remove the daily fixed charge of the hot water meter.

– Warwick Moore

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