Many of Canada’s major cities, including Toronto, Montreal, Winnipeg, Ottawa, and Regina, are strategically situated along the Canada-US borders, where solar insolation reaches its zenith compared to the northern parts of the country. With a substantial demand for building envelope heating for almost eight months a year and a year-round need for domestic hot water and other process water heating applications, solar energy emerges as a highly promising renewable energy source for Canada.
This article aims to elucidate the workings of various Hydronic Solar Heating Systems, specifically those utilizing Vacuum Tube Solar Collectors. These collectors, known for their superior performance during Canadian winters, outshine other types such as glazed and non-glazed flat plate panels.
How Solar Thermal Water Heating Works
Solar Thermal Panels, regardless of their type, function as heat exchangers. Among these, Evacuated Tubes Solar Collectors, available in configurations of 15, 20, 25, and 30 tubes, stand out. They absorb solar radiated energy and transfer the harvested solar energy into a fluid—whether water, a polypropylene glycol/water mix, or other fluids—in a closed-loop configuration. This process aims to heat a secondary fluid suitable for the specific heating application, such as water for Domestic Hot Water (DHW) Heating, air for Hydronic Air Handling Units, or chlorinated water for swimming pools.
Pressurized Polypropylene Glycol Solar Line Configuration
In a typical pressurized configuration, an immersed coil transfers harvested solar heat into a Hot Water Storage Tank through an indirect immersed coil. This setup is effective in cold climates and works well in retrofit contexts where an electric or natural gas domestic hot water heater is already installed. In such cases, the Solar Hot Water Storage Tank preheats domestic cold water before it enters the existing hot water heater.
Solar Heat for Hydronic Radiant Floor Heating
In areas employing hydronic radiant floor heating, solar heat can be transferred to hydronic floor heating loops via a thermal storage tank. A recommended approach involves using a dual-coil tank with two inlets and outlets. The lower coil harvests solar energy collected by solar collectors, while the upper coil transfers solar energy to hydronic heating loops. The tank’s main inlet and outlet can be reserved for DHW heating.
Most Common Solar Water Heater Configurations
Regular Split Solar Water Heating System
This configuration, featuring an external heat exchanger (usually a brazed plate heat exchanger), is employed in residential and commercial retrofit projects where an existing Domestic Hot Water Heater or space heating device with thermal storage is in place.
Split Solar Water Heating System with Pressurized Closed Loop
Particularly beneficial in Nordic climates, this system utilizes a closed loop containing a heat transfer fluid with an anti-freeze solution (usually a propylene glycol mix). In pressurized drain-back systems, the heat transfer fluid requires an anti-freeze solution as it drains back to the tank (located indoors) when the pump is turned off by the solar controller.
Regular Split Solar Water Heating System with External Heat Exchanger
Commonly used in residential and commercial retrofit projects, this system involves an external heat exchanger, usually a brazed plate heat exchanger. While cost-effective, it may be less efficient due to regulatory requirements and limitations in pre-heating return with hot fluid produced by solar.
Challenges & Considerations in the Mechanisms of Solar Water Heating Systems
In DHW heating applications, maintaining a high temperature as required by regulations can impact the efficiency of Vacuum Tube Solar Collectors. Closed-loop heating applications may face limitations in pre-heating return with hot fluid, reducing the savings generated by the solar water heating system. Additionally, the efficiency of the brazed plate heat exchanger is affected by friction loss and temperature loss. Electrical power consumption is higher in configurations requiring two circulation pumps, presenting a trade-off between system cost and efficiency.
Most Common Solar Water Heating Applications
Solar water heating applications align with general water heating needs, encompassing thermal comfort in space heating, infloor heating, forced air heating, swimming pool heating, process heating, and various other applications. Given the time gap between solar radiation availability and hot water demand, each hydronic solar system requires thermal storage in the form of a water tank for daily storage or underground seasonal thermal energy storage in a thermal pit.
Solar Water Tank Solutions
Designed to accommodate multiple applications, our Solar Water Tanks provide a secondary or tertiary source of heat, enhancing system reliability. This flexibility offers customers one or two levels of redundancy when solar energy is absent for longer periods, such as consecutive winter days without sun.
Explore Solar Water Heating Kits
The 2 x 30 Tubes Panel Kit with Tank and accessories, integrate seamlessly with Air to Water Heat Pumps and/or Titanium Heat Exchangers for swimming pools. Designed primarily for space heating, these kits can be adapted for applications where DHW heating dominates the load. The 4 x 30 Tubes Panel Kit with Tank and accessories, combined with an Air to Water Heat Pump, is a popular choice for modern homes in regions with milder winter temperatures.
Conclusion
In conclusion, understanding how solar water heating systems work is essential for harnessing the full potential of renewable energy, particularly in a country like Canada. With a wealth of solar energy available, these systems offer a sustainable and cost-effective solution for meeting various heating needs. Whether for residential or commercial applications, the versatility and efficiency of solar water heating systems make them a cornerstone in the transition to greener and more sustainable energy practices.
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