When it comes to the structure of solar water heaters, they can generally be categorized into several types based on their design and function.
1. Based on the heat collection part:
1) Glass vacuum tube solar water heater
This type includes all-glass vacuum tubes, heat pipe vacuum tubes, U-shaped vacuum tubes, and integrated vacuum tubes. The most commonly used is the all-glass vacuum tube model. It offers advantages such as safety, energy efficiency, environmental friendliness, and cost-effectiveness. Solar water heaters with an electric heating backup are particularly useful in low-temperature environments, ensuring consistent performance throughout the year. However, these systems tend to be bulky, with fragile glass tubes that may accumulate scale and cannot operate under pressure. To address these issues, Tsinghua Sunshine has developed a heat pipe vacuum tube system, which uses a heat transfer medium to improve durability and reduce scaling problems. This design also increases thermal efficiency by nearly ten percentage points compared to traditional models.
2) Flat plate solar water heater
Flat plate collectors come in various designs, including tube-plate, wing-tube, coil, flat box, round tube, and heat pipe types. Their benefits include long lifespan, low failure rate, high safety, and the ability to operate under pressure. They also have a large heat absorption area, making them easy to integrate with buildings. However, due to non-vacuum insulation inside the cover, their heat retention is poor at low temperatures, leading to lower efficiency when auxiliary heating is needed. In colder regions, frost damage can require full replacement of the collector plate, making them more suitable for southern areas where freezing is rare.
3) Ceramic hollow flat solar water heater
Ceramic solar panels are made from a base of common ceramic material with a three-dimensional mesh vanadium-titanium black porcelain surface layer. These panels are waterproof, durable, resistant to corrosion, aging, and fading, and have no toxic or radioactive properties. They maintain high sunlight absorption efficiency over time. According to the National Solar Water Heater Quality Supervision and Inspection Center, ceramic solar panels have a solar absorption ratio of 0.95 and daily heat output of 8.6 MJ, exceeding national standards. They are cost-effective, long-lasting, and can be integrated into building structures, providing hot water, heating, and even power generation in large-scale applications like desert solar farms and seawater desalination.
2. Based on structural design:
1) Compact solar water heater: This design inserts the vacuum tube directly into the water tank, using natural convection to heat the water. It is the most common type available in the market.
2) Split-type solar water heater: This model separates the collector from the water tank, allowing for larger capacity and improved usability without relying on gravity-fed water flow.
3. Based on the water tank pressure:
1) Pressure-bearing solar water heater: These systems deliver hot water under pressure, typically through a top-water mechanism, and do not require a pressurized tank.
2) Non-pressure-bearing solar water heater: The most common type, these units have a water tank open to the atmosphere, relying on the height difference between the roof and home to generate pressure. They are safer, cheaper, and have a longer service life than pressure-bearing models.
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