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Solar Water Tanks – Worthy Recommendations on How to Size Them Properly

When solar water tanks are used in proper sizes, they allow the solar heating systems to function perfectly and cost-effectively. There are a few crucial reasons for which the solar hot water tank storage sizing becomes essential:

  • If the solar water tanks are undersized, they may get overheated, shut off the pump and make the solar collectors water-starved.

  • If the solar hot water storage tanks are larger in size, users may experience little heat performance at a heavy price.

What are The Solar Water Tanks Used for?

The solar water tanks are basically used for solar water heating. They store heat in hot water and help preserve the solar energy produced by the solar thermals collectors during the day time so that it can be used in the evening, night and the next day morning. Normally, the solar water tank temperature will begin with the temperature of water coming from the mains supply in the morning and go up to 140-160F with solar energy production till late in afternoon (If ever the tank temperature goes far above this mark, then corrosion can be an issue – the effect of corrosion will be double for every 20F rise in temperature).

Sizing of Solar Water Tanks: The Calculation

After all the family members take a shower in the morning, the solar water tank temperature may go down to attain the mains water supply temperature and the SHW owners may require a certain quantity of energy to bring the temperature back to its previous level i.e. 140-160F.

They can depend on the formula given below and calculate the exact size f their solar water storage tanks:

V = 120/(X – Y)

  • X is the parameter representing set-point temp of the solar water heating system

  • Y is the parameter taken for mains water supply temperature at the specific location

  • V is the parameter for solar storage tank volume required per square feet of solar collector

This above formula is quite safe and can be a rule of thumb to serve SHW users well in majority cases (and can be effective in balancing the price and longevity of the solar water heating system). If there is a significant draw of heat energy during the day time, then a low volume solar water tank can be used.

Easy to Follow Solar Water Tanks Sizing Recommendations:

SHW owners can follow this recommended list of sizing for storage tanks with solar PV collectors:

  • 1 gallon solar water tank volume per square feet area of solar collectors (for high-temperature requirement in northern climates condition with flat plate collectors)

  • 1.5 gallons solar storage tank volume per square feet area of solar collectors (for medium-range temp and typical energy requirements in SHWs including flat plate collectors)

  • 2 gallons solar tank volume per square feet area of solar collectors (high-temp heating systems with evacuated tubes and low-temp heating systems with flat plate collectors)

  • 2.5 gallons solar tank volume per square feet area of solar collectors (for medium range heating systems with evacuated tubes)

  • 3 gallons solar water tank volume per square feet area of solar collector (for low-temp heating systems)

  • 4+ gallons solar tank volume per square feet area of solar collectors.

All the above recommended solar water tank sizes are worth considered but must be thoroughly analyzed by expert heating engineers for calculating exact payback.

Latitude51 Solar distributes quality solar and PV systems all across the USA, Canada and Caribbean. It has an expert team of engineers to advice and give tips on sizing of solar water tanks. To buy the right size of solar water tanks, Latitude51 Solar’s expert engineers can be called and consulted at 1800 317 9054 Now!

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