The initial investment of a solar water heater is usually more than conventional water heating systems. The home owner will save more money in the long run, depending on the amount of hot water required, system’s performance, geographic location, and cost of conventional backup.
The following are the key things to consider when selecting a solar water heater;
1. Average Daily Efficiency and Average Heat Loss Coefficient
These are vital thermodynamics target of the vacuum tube. The efficiency of a solar collector is dependent on the temperature of the tube which in turn is dependent on the nature of fluid flow in the tube, solar insolation, glass cover emissivity, ambient temperature, and slope. Once you install a solar water heater, your water heating bills should drop by more than 50%. Interestingly, sun’s energy is free. Therefore, you will not be affected by fuel price fluctuations and fuel shortages.
2. Solar Energy Factor (SEF) and Solar Fraction (SF).
SEF is the energy produced by solar water heating system divided by electrical/gas energy within the system. The higher the factor, the more the system’s energy efficient. The factors range from 1 to 11, but 2 to 3 are the most common factors.
SF is the part of the total conventional water heating load. The bigger the solar fraction, the higher the solar energy contribution, hence reducing the energy required as a backup. The solar fraction ranges from 0 to 1.0, but 0.5 to 0.75 are the typical factors.
Before buying a solar water heater, you should consider calculating the annual operating cost in order to determine the energy saving and payback period.
3. Heat Absorption Efficient
The absorber coating is responsible for absorbing sun’s heat, as well as preventing heat loss through radiation. The vacuum tube should have absorption coefficient greater than 93%, and emission coefficient less than 10%. Also, you should choose a system with the absorber coating of CU-SS-AL/N/AL for maximum sun’s heat absorption, durability, and long lifespan.
4. Stainless Steel Water Tank and Frame
When choosing a solar water heater system, consider the storage tank and the mounting frame for the solar collector. Stainless steel tank stands out as the best for its exclusive ability to resist corrosion, as well as high durability. Also, they have less maintenance cost, and lightweight nature makes them easily installed.
Choice of the frame depends on the environmental condition to ensure durability and safety of the collector once mounted on the roof. The best frames are made up of stainless steel or high tensile anodized aluminum. Stainless steel is excellent for resisting corrosion while aluminum is suitable for strength especially in strong windy regions.
5. Electric Heater Certification
Apart from assured warranties when buying your hot water heater, it is vital to check authenticity of the electric heater. Before purchasing, check if it has CE certification in order to enjoy big savings, smart purchase that protects the environment.
6. Daily Water Consumption Per Capita
The maximum daily hot water usage per head is 50 Litres. This should be one of the factors to enable you choose a solar water heater that will satisfy your family. Using the average per individual hot water consumption; a system with a capacity of 250/300L can be fit for a family of 5 to 6 people, system with a capacity of 200L is suitable for 3 to 4 people, while system with a capacity of 100/150L is suitable for 1 to 2 people.