How Does Solar Hot Water Work?

Updated: August 29, 2023

Solar hot water systems are gaining popularity as a cost-effective and eco-friendly household heating solution. But how do these systems work, and are they truly the energy-saving marvels they are made out to be?

Solar hot water systems capture energy from the sun and use it to heat water. Heat-absorbing solar collectors mounted on your roof collect sunlight, which is then transferred to an insulated storage tank.

On cloudy days, a gas or electric booster can keep the water at the right temperature. These systems help reduce your carbon emissions and energy costs.

Join us as we unveil the mystery behind solar hot water systems and explore their many benefits.

  • Solar hot water systems are an energy-efficient solution for heating water in households.
  • Components such as solar collectors, storage tanks, and circulation methods facilitate the process of transferring cold water to absorb heat from the sun’s radiation before returning it to a storage tank.
  • Solar hot water systems provide financial savings, reduce emissions, and contribute to sustainability.

Components of solar hot water systems

At its core, a solar hot water system is a simple yet ingenious technology that harnesses the sun’s energy to heat water for residential use. These systems consist of solar collectors, which capture and convert solar radiation into heat, and a storage tank that holds the heated water until it’s needed.

Some systems also employ a gas or electric booster to provide extra heat when solar energy is insufficient. As a result, solar hot water systems can significantly decrease energy consumption and reduce your carbon footprint, making them an attractive option for homeowners looking to save on energy bills and contribute to a greener planet.

Solar collectors

Solar collectors play a vital role in the efficiency of a solar hot water system. Typically, these collectors are mounted on the roof, facing north to maximise exposure to the sun’s energy. They are designed with dark, heat-absorbing surfaces that efficiently capture the sun’s heat, which is then transferred to the water circulating through pipes inside the collector.

These collectors come in various shapes and sizes, but the most common type is the flat plate collector, which is approximately 2m tall and 1m wide. These collectors are constructed from materials that are highly effective at conducting solar radiation, ensuring that the maximum amount of heat is absorbed and transferred to the water.

Storage tanks

Storage tanks are another essential component of solar hot water systems, serving to retain the heated water until it’s needed for household use. These tanks are typically constructed from high-grade stainless steel or vitreous enamel coated mild steel, ensuring durability and longevity.

The size and warranty period of the storage tank will depend on the specific model chosen, but most tanks offer a cylinder and collector warranty of 5, 7, or 10 years. It’s important to choose a tank with a capacity that meets your household’s hot water demands, taking into account factors such as family size and daily water usage.

By doing so, you’ll ensure that you have a constant supply of hot water when you need it.

Circulation methods

Circulation methods refer to how water is transported between the solar collector and the storage tank. There are various types of circulation methods, such as direct and indirect systems, as well as differences in the solar collectors used.

In ground-mounted direct systems, an inbuilt circulator is used to pump the water throughout. On the other hand, roof-mounted systems make use of the natural “thermosiphon” effect. This effect is based on the principle that hot water rises and cold water sinks, allowing for the natural movement of heated water from the collector back to the storage tank.

By understanding the different circulation methods available, you can choose the most efficient and suitable option for your home’s solar hot water system.

How solar hot water systems work: a step-by-step process

Now that we’ve explored the components of a solar hot water system, let’s dive into the step-by-step process of how these systems actually heat water.

The procedure begins with cold water being transferred from the storage tank to the solar collector, where it absorbs the sun’s heat. Once heated, the water returns to the storage tank, where it is readily available for household use.

Cold water transfer

The first step in the solar hot water heating process is cold water transfer. In this stage, cold water from the storage tank is moved to the solar collectors, where it will be heated by the sun’s energy. This transfer is facilitated by a pump and a heat transfer fluid, which work together to circulate the water through the system.

Cold water transfer is an effective method for heating water using solar energy, as it allows for the efficient transfer of heat from the solar collectors to the storage tank without the need for additional energy sources. By minimising energy consumption, this process helps to reduce your overall energy bills and carbon footprint.

Solar heat absorption

Once the cold water has been transferred to the solar collector, it’s time for the solar heat absorption process to take place. In this stage, the upward-facing surface of the solar collector, which is designed to efficiently absorb the sun’s heat, transfers that heat to the cold water running through the pipes inside the collector.

As the water absorbs the sun’s heat, its temperature increases, effectively transforming the cold water into hot water. This process demonstrates the power of solar energy and its ability to provide a sustainable and cost-effective solution for heating water in households.

Heated water return

With the water now heated, it’s time for it to return to the storage tank. Heated water return can occur through either natural circulation or a pump system, depending on the specific solar hot water system installed in your home.

In a natural circulation system, the principle of thermosiphon comes into play. As hot water rises and cold water sinks, the heated water in the solar collector is drawn back to the storage tank.

Alternatively, a pump system can be used to force the hot water to return to the storage tank, ensuring that the heated water is readily available for household use.

Hot water availability

Solar hot water systems are designed to continuously heat water, providing a reliable and sustainable source of hot water for your household. However, factors such as climate, location, and system size can affect the availability of hot water.

In cases where solar hot water systems are unable to provide sufficient hot water, supplementary heating options can be employed. Gas or electric boosters can be installed to ensure that the hot water tank remains at an adequate temperature, providing your household with the hot water it needs, even during periods of insufficient solar energy.

Comparing solar hot water systems and heat pumps

Comparing solar hot water systems and heat pumps

While solar hot water systems harness the sun’s energy through solar collectors, heat pumps are another type of solar hot water system that collects heat from the atmosphere instead of utilising solar panels.

Heat pumps use an evaporator to draw in air, similar to an air conditioning unit. This is how they work. The evaporator transforms refrigerant liquid into a gas and pressurises it, which is then heated within condenser coils in contact with water, thereby heating the water.

Heat pumps do require electricity to operate, which sets them apart from solar hot water systems that rely solely on solar energy. However, both systems offer energy-efficient solutions for heating water in households, and the choice between the two will depend on factors such as location, climate, and personal preferences.

Solar hot water system performance in various weather conditions

A common concern among homeowners considering solar hot water systems is their performance during nighttime, cold weather, and cloudy days. The good news is that solar hot water systems are designed to operate effectively even in less-than-ideal conditions.

Solar hot water systems can still function in overcast conditions and continue to provide hot water during the winter months. In the rare event that the system is unable to produce sufficient hot water, a gas or electric booster can be employed to ensure that your household maintains a consistent supply of hot water, regardless of the weather conditions.

Choosing the right solar hot water system for your home

Selecting the best solar hot water system for your home involves considering several factors, such as the type of residence, climate, water quality, and family size. By taking these elements into account, you can ensure that you choose a system that meets your household’s specific needs and requirements.

To assist you in making an informed decision, professional solar hot water experts can offer valuable guidance and advice. These experts can assess your home’s conditions and discuss your individual needs, helping you choose the optimal solar solution for your home.

The benefits of solar hot water systems

Solar hot water systems offer a range of benefits that make them an attractive option for homeowners looking to save on energy bills and reduce their carbon footprint. By harnessing the power of the sun, these systems can significantly decrease energy consumption, resulting in substantial savings on energy bills.

In addition to financial savings, solar hot water systems contribute to a greener planet by reducing greenhouse gas emissions and enhancing overall sustainability. By opting for a solar hot water system, you’re not only investing in your household’s future, but also in the well-being of the environment.

Debunking common myths about solar hot water

Several myths and misconceptions surround solar hot water systems, which can cause confusion and uncertainty among homeowners. For instance, some believe that solar hot water systems only function when it’s sunny, that they’re too expensive, or that they can’t store hot water like traditional water heaters. It’s important to dispel these myths to provide accurate information for better decision-making.

The truth is that solar hot water systems can operate even on cloudy days, and while they may have a higher upfront cost, the long-term savings on energy bills make them a cost-effective solution.

Moreover, solar hot water systems are fully capable of storing hot water, ensuring a continuous supply for your household’s needs. By debunking these myths, we hope to encourage more people to consider the benefits of solar hot water systems for their homes.

FAQ's

The disadvantages of solar hot water include a high initial cost, potential maintenance needs, and the requirement for long periods of unobstructed sunlight to be effective.

In many cases, these drawbacks may mean that other water heating options are more suitable.

It is possible to have hot water at night from solar heating. During the day, a solar hot water system captures the sun’s energy and stores it in a tank. This stored heat can last long enough for you to still have hot water during the night.

Ben McInerney head shotAuthor: Ben McInerney is a renewable energy enthusiast with the goal of helping more Australians understand solar systems to make the best choice before they purchase. Having an accredited solar installer in the family helps give Ben access to the correct information, which allows him to break it down and make it easily understandable to the average homeowner.