Solar Domestic Hot Water System (SDHW)

How Solar Domestic Hot Water Systems Work

The solar domestic hot water system works via a closed loop system. A closed loop system heats water via a heat exchanger, evacuated tube collectors and a heating fluid. This system is designed to work with any existing domestic hot water system. Cold water is diverted into a heat exchanger tank which is heated by the split solar collector. Once the water is heated to the desired temperature it flows from the heat exchanger tank into the current heating system where it requires little or no additional heating.

Solar Domestic Hot Water System Schematic

The solar domestic hot water system works by pumping a heating fluid into the solar collectors where it is heated and then into a heat exchanger tank where the heat is transferred (or exchanged) to the water in the tank. The fluid then repeats this cycle until the desired temperature is achieved. The hot water in the tank rises to the top by a process called thermosyphon. Once there is a demand for hot water, the water at the top of the heat exchanger tank flows into the current water heating tank where it can be heated further if necessary.

A Solar DHW system utilizes the following components:

Solar Collector (1 collector is most commonly required per household)
Heat Exchanger Tank
Pump
Expansion Tank
Controller

The solar domestic hot water system is completely automated and can be set to heat water to any desired temperature. Once the controller senses that the desired temperature has been achieved it will stop pumping water into the collector.

As previously mentioned, this system utilizes a separate heating fluid (a mixture of water and glycol) to transfer heat from the collectors to the heat exchanger. The tap water never enters the collectors or comes in direct contact with the heating fluid. Nonetheless, the fluid is propylene glycol which is a safe liquid found in various foods. This mixture of glycol and water is used as a heating fluid in order to prevent the pipes from freezing in the winter. Although the pipes are well insulated and in some cases are not exposed to the outside air, the mixture will prevent any freezing from occurring.

Benefits of Solar Domestic Hot Water Systems

The most common conventional domestic hot water systems run on electricity or natural gas. These systems are found in residential and commercial applications and the cost of heating water using electricity or natural gas can be quite high. Not to mention, conventional domestic hot water systems cost between $3,000-$6,000 and require constant maintenance. The average lifespan of such systems is 7-10 years. Therefore in 10 years you will have to purchase a new domestic hot water system, not to mention all the tune ups that are required along the way.

Meanwhile, an average solar domestic hot water systems costs between $2700 and $3500 before installation. This investment will not only reduces your monthly energy bills, reduces greenhouse gas emissions, save up to 1000 cubic meters of natural gas a year but it will also prolong the life of your current heating system.

Solar domestic hot water systems are a great way to pre-heat or completely heat water without paying extra on your monthly utility bills. The sun's UV rays are absorbed to heat water instantly where it can be stored or diverted into the current domestic hot water system where it requires little or no additional heating. Solar domestic hot water systems also require no maintenance and could last up to 20 years. Also, after 20 years, the entire system does not need to be replaced. Instead, a few parts can be replaced making this investment more feasible.

With the solar domestic hot water system, the cost of heating water can be greatly reduced even in the winter months. Depending on the weather, your current water heating system does not always need to start. In some months, the cost of heating water with your current heating system could be as low as $30. This system will also reduce a single home's greenhouse gas emissions by 2 tonnes each year. Also, by installing a solar domestic hot water system the life of your current heating system will be extended given that the load on your system is greatly decreased.

Just by pre-heating cold water with solar energy you can save between 50-70% of your current energy bill.

The current water heating system found in every home or commercial facility heats tap water, which enters at 5-15 degrees Celsius depending on the weather, to a desired temperature set by the user, normally between 40-50 degrees Celsius. This water enters the building and is diverted into the current water heating tank where it is constantly heated to maintain the desired temperature. By constantly re-heating the water, the current water heating tank utilizes a lot of energy throughout the year. This is where a solar domestic hot water system will reduce greenhouse gas emissions while reducing monthly energy costs.