Have You Sized Your Solar Water Heater Correctly?


Solar Heaters have different capacities and when buying and commissioning one, it is important you are aware of your hot water needs. Depending on the numbers of users, the plate collectors vary, as does the storage tank. In nations like the UAE where climate temperatures are high, Solar Water Heaters are the best thermal application to use. These systems provide hot water on very high efficiency in such areas and even similar efficiency across other nations and continents on an average supply rate during summer periods.

The correct approximate size of the collector and the storage unit for the solar heaters results in high and optimal efficiency and more effective systems reliable for the users. As a user, it is important to know the number of people (fixed and variable) and restrictions to avoid running low on hot water. The information gives a solid basis for sizing and change and eventual efficiency rating.


In terms of installation, the importance of maximizing solar energy is great, therefore, it requires appropriate sizing and orientation. Specialized arrangement of plate collectors, and the storage tank, is important. We must put consideration into the solar heater type, direct gain, flat plate collector and so on. Aside from the type selected, the tilt and orientation of the solar collector are paramount. For regions close to the equator, the solar collector tilt angle is zero degrees, but for a region like UAE according to research, 22 to 24 degree was a good tilt angle range.
However, for optimal solar absorption, 22 degrees is the better angle. The installation process varies from region to region and depends on the position or distance from the equator. However, it is important to state that the effect of the installation process causes deviation and variation in the amount of solar radiation absorbed by up to 20%. Also, in terms of the circulation system, we must put consideration into the installation height of the water storage tank. It could improve thermal efficiency because of this single factor. Either forced circulation or thermosiphon system is in place, the installation process has to be appropriate to avoid unnecessary change.

Sizing and Commissioning

Having taken the tilt and orientation into consideration during commissioning, we measure the size of the solar collector (for example, a flat plate), this along with the tilt orientation would provide the optimal experience for the users.

Important to the design of the solar heater is the flat plate collector. We must do the calculation in terms of the amount of energy and the energy available needs to give a more accurate sizing of the flat plate collector for further analysis. Find the water usage per person, the number of people using the hot water, the average desired temperature and the average incoming water temperature to calculate the energy required to shorten the search of the solar heater you need. The value you derive from using the parameters stated will inform your decision to what to get as the energy rating of the solar heater is stated on these thermal systems.
The energy available is depending on the solar collector efficiency, solar intensity and insolation because of climate. The resulting value from a division of the energy values can give a good approximation of the collector aperture. Most studies show that a person uses an average of 20 gallons of hot water daily. Therefore, 30 to 60 gallons’ tank storage volume corresponding to less than or equal to three persons. For four persons, 80 gallons’ storage volume capacity is enough. For greater than four and less than six persons, we estimate 120 gallons’ volume capacity to be adequate. A more than adequate estimation is using volume capacity to the collector area. The recommended guideline is 1.5 gallons’ volume capacity per square foot collector area.

Piping System

Aside from the heating elements and the energy system, the piping system has to be ideal. Pressure testing the piping network to make it carries the water at the pressure is trivia. The collectors play a part in this area. The collectors have to be inclined in a manner to prevent the air bubbles in the piping network. Where the supply pressure is low, the pipe installation needs with it a downward flow to let our air that might have accumulated. In terms of safety, we should install a safety valve.
Pressure testing needs to be done on the piping system to inform changes in the network. We can pressure test with water alone to determine leaky areas or joints. The pressure testing could be done with water and compressed air or air alone. Whichever, the pressure must be at the recommended mark to allow the sizing and changes to make an absolute impact.

Energy Efficiency

Efficiency is a necessary quality in every system, and so it is for solar heaters. According to research, tilt, orientation is of significance to efficiency rating. The efficiency of a solar water heater depends on how much of the sun’s energy reaches the collector. Following the above sections strictly with research, you are certain to get a better efficiency that when installed without it. Now, we have successfully carried out thorough commissioning of a well-sized Solar Heater.


To increase the utilization efficiency for the solar collectors which affects the efficiency of the solar heaters, we should mount it at the monthly optimum tilt angle and carry out slope change once every month according to the corresponding tilt angles for every month. However, based on calculation results from certain journals, change the tilt angle, at least twice a year. In terms of the size of the solar heater, the size must correspond to the number of the intending uses giving allowance for some people to avoid using a backup solar heater or having less or no hot water when you need it.
For Solar Heater you intend to get, QCC Approved and Dubai Municipality Approved requirement is a must. Moosa-Daly provides great solar heaters such as Termicol, which are adjustable for different users and fulfil the Solar Keymark Certificate. Also, if in the UAE, the solar heaters have to be Dubai Municipality approved and ISO 9001 Quality assured. If you intend to get some solar heaters for personal, community or industrial, you can check here for more information.


by Hakim Kagalwala – Business Development Executive

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