So you’ve read through the all the information on the differences between gas and solar power, and you think you’ve got the gist of evacuated glass tube systems versus flat plate systems? Excellent, now it’s time to consider whether a Thermosiphon or a Split Solar Hot Water System is the right choice for you.
Positioning of Solar Water Storage Tank
The Thermosiphon or the Split Solar options essentially refer to where you want the storage tank for your collected water to be positioned. For this, there are two options:
- If the tank is placed on the roof, the system utilises the rising of hot water to move the water through the panel without the need to rely on an external pump. This is called the thermosiphon system because the eater is siphoned through the system 100% thermally.
- By placing the tank at ground level the water must travel up to roof, which means that you will need an external pump to allow this happen, this is what is known as a split system.
The thermosiphon is the most popular system in Australia mainly due to its cost-effectiveness, efficiency, and low maintenance. The distinctive feature of the thermosiphon system is the tank positioned at the top of the panel.
How does it work?
- Cold water from the water mains is connected to the bottom of the panel through a series of pipes
- As the panel comes into direct sunlight, the water heats up
- The hot water moves up the panel and into the tank and pushes the cold water out, starting a cycle of warming
- The cycle continues as long as the sun keeps shining through the day
The result of this cycle is a full tank of hot water. If the heat from the sun isn’t strong enough, or the weather changes for an extended time, the heat of the water will be boosted by either electricity or gas to ensure continuous warmth.
An electric boost comes from the heating of the electrical element to boost the heat of the water upwards.
A gas boost allows water to be heated through an instant gas heater on demand whenever a hot water tap is used. Therefore the gas boosting is a lot more efficient to save the collected warmth from the solar panels.
- An affordable option (approx. $1500 – $5000 to install)
- Effective and reliable system
- There is no pump or electricity needed to move the water
- You must have a strong roof in order to hold the weight of a full tan
- The tank is exposed to the elements, meaning that is could potentially be damaged, or lose more heat than a tank on the ground
- Not as aesthetically pleasing as other options
The alternative solution to where to store your tank, and to where you will get your hot water system is the split water system. With this system, the tank is stored on ground level, meaning that it will not damage the aesthetics of your home, be susceptible to storms or other weather damages, or break through your roof, and it has the potential to keep more water hot for a longer period of time.
How does it work?
The split system operates with the help of electricity. The pump is powered electrically to merge the water through your storage tank and solar collector and straight into your tap. This system is remarkably different to the old fashioned electric hot water systems; instead on relying wholly on electricity to heat your water, these systems rely on solar power and the collection of heat from the sun through the solar panels, with the electric pump as a small addition to their operation. The pumps are rated around 30 Watt, and make only a small dent in the cost of your annual electricity bill of around $10 per capita.
- Ground level tank is easier to access
- It is easier to super-insulate the tank, and to retain heat
- More flexible boosting choices (instant gas, gas storage, electric, or electric heat pump)
- Electricity is necessary to power the pump
- Longer pipe runs can affect heat circulation
- Slightly more expensive and complex to maintain
Two Tank Systems and the Advantages of Preheating
With tanks that can retain up to 450 litres of hot water per day, the single tank system is often the most effective for the average Australian household. These large tank systems may work the best for many households, however the use of the two tank system will ensure that you will have access to glorious warm, solar-heated water 24/7, regardless of the size of your household.
So far the only systems that we have discussed have been based on the use of one tank. So, why would you need another?
Two tank systems reduce the need for gas or electric boosters to keep your hot water system going. The advantage of the two tank system is that you can ensure that you will have continuous hot water throughout the day and night without having to worry about the extra cost that the booster could incur.
The two tank system allows the hot water in your household to remain constant regardless of the amount that has been used throughout the day. While tank one is in use, tank two is pre-heating water so that it is readily available when the amount of water in tank one has depleted. When tank two switches to becoming the dominant tank, tank one refills and replenishes its store of hot water. These two tanks work alongside the existing circulatory system, and continue to circulate cold water just as a singular tank does, however through two tanks instead of one. The two tank system allows hot water to be more readily available to the household, as there will always be a store of pre-heated water available, and is more energy efficient as it hugely reduces the use of electric or gas boosters.
- Hot water constantly available
- More beneficial for hot water use for larger households
- More energy efficient
- Less reliance on boosters for when hot water storage is depleted
- Higher up-front cost
- More complex maintenance required
- Need for larger space for storage
- Virtually unnecessary for households of less than five people