Solar Hot Water System

The Amazing Benefits of Solar Power

Solar Hot Water System Melbourne

Solar power is gaining traction in the world of alternative energy and is becoming utilized in many areas of everyday life. One method of implementation is the solar hot water system. These systems range from simple solar domestic hot water systems to complex industrial scale operations capable of heating water for businesses and other large-use situations.

Parts of a solar hot water system:

  • Collectors
  • Heat-Transfer Fluid
  • Heat Exchangers
  • Pumps
  • Controllers

Solar PowerCollectors

The collector captures the sunlight to be used throughout the rest of the system. For this reason, the type of collector plays a large role in the workings of the rest of the system.

The most basic collector is simply a tank, filled with water, sitting in the sun, which is how the first solar hot water system functioned. Such a simple system is, however, inefficient as there is little to prevent the loss of heat back to the environment. Insulation improves this system by leaps and bounds, but it is not widely used as some other methods such as a flat plate collector.

Flat plate collectors consist of a large, flat surface, called an absorber, which maximizes exposure to sunlight. Fluid runs through small tubes in the collector, absorbing the heat for use in the rest of the system. Flat plate collectors are well insulated all around, with a plate of glass on top to allow sunlight through while still retaining the necessary heat.

In practice, this is a fairly simple system, with straightforward workings and implementation, but there are a few technical factors that figure into making the solar hot water system as efficient as possible. For example, the glass is high in iron and specially coated to prevent heat loss. The coating on the glass is designed to collect as much heat as possible while radiating back out as little as possible, augmenting the insulation even further.

There are two more types of collector which we will cover briefly. The first is called evacuated tube and uses a long, thin absorber with a glass tube inside. The tube has the air evacuated from it, much like a light bulb, making it highly insulated. The second is a parabolic dish or tray and is most commonly used in larger-scale systems to generate steam which is used to run turbines for generating electricity. The dish focuses sunlight into a small absorber, enabling much higher heat potential.


Heat-transferred fluids are responsible for carrying the heat through the solar collectors and a heat exchanger to the storage tanks. The heat-transfer fluid is the bridge between the collectors and the desired hot water, so, needless to say, the type of fluid chosen has an impact on the rest of the system. There may be some restrictions or requirements on the type of fluid used in the solar hot water system, so be sure to check the local regulations yourself or ask the solar heating professional installing the system.

There are six main options:

  •  Air. Air does not boil or freeze and is also non-corrosive. However, it has a low heat capacity, and, being air, tends to escape from the collectors and pipes.
  • Water. A high specific heat capacity, low viscosity, and the ease with which it can be pumped, combined with being non-toxic and inexpensive make water better than air. However, for areas with extreme weather, the low boiling point and high freezing point make water a limited option. It may also become corrosive if pH level is not maintained, and mineral deposits may form in pipes if the water has a high mineral content.
  • Glycol/water mixtures. To counter-act the freezing problem inherent in a pure water based solar hot water system, glycols (antifreezes) can be added to water in a 50/50 or 60/40 ratio. These antifreezes must be changed every 3-5 years as they degrade over time. They also require a pressurized system, which should only be serviced by a solar heating professional.
  • Hydrocarbon oils. Being Inexpensive, having a low freezing point, a lower specific heat than water, and a higher viscosity could make hydrocarbons ideal in your solar hot water system. They do require more energy to pump, but that may be just fine. Some hydrocarbons are toxic and require a more complex system while others are non-toxic and require little maintenance.
  • Refrigerants. Also used in refrigerators and A/C units, they have high heat capacity and low boiling point. A small amount of refrigerant can transfer a large amount of heat very efficiently, and also absorbs solar heat quite rapidly. This is ideal for cloudy areas.
  • Silicones. Low freezing point, high boiling point, non-corrosive and long lasting. Silicones require more energy to pump, and they also leak, even through tiny holes in the system.

Solar Hot Water SystemHeat Exchangers

There are two basic categories of heat exchanger for any solar hot water system: Liquid-to-liquid and Air-to-liquid.

Liquid-to-liquid exchangers use a heat-transfer fluid circulating through the collector and then running through the heat exchanger to transfer the heat to water stored in a tank.

Air-to-liquid systems use air heater collectors, which actually don’t require a specific exchanger but transfer the heat to the water without any intervening fluid.


The pump of a solar hot water system is responsible for moving the heat-transfer fluid through the system and for this reason the type of pump largely depends on the amount of pressure required to move the heat-transfer fluid.


Every solar hot water system has a controller which turns the pumps on and off, based on input from a temperature sensor. The sensor detects when the collectors are at a higher temperature than the storage tanks and the controller then activates the pumps to circulate the heat-transfer fluid through the system to transfer the heat to the water in the tanks. Then the hot water will be ready to use throughout the building!

Benefits of Solar PowerA solar hot water system can be installed directly on a house as an excellent way to save on the energy bill and reduce dependence on the grid. Understanding the components of the system will help you make an informed decision about the system required for your hot water needs.

For a quotation of a solar hot water system cost, feel free to contact us today.


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