Solar Water Heater Calculation

BTU per Day Formula:

\[ BTU/day = Gallons/day \times 8.34 \times \Delta T \]

Daily BTU Requirement:

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1. What is BTU per Day Calculation?

The BTU per day calculation determines the daily energy requirement for solar water heating systems. It helps size solar thermal systems appropriately based on water usage and temperature rise needs.

2. How Does the Calculator Work?

The calculator uses the BTU per day formula:

\[ BTU/day = Gallons/day \times 8.34 \times \Delta T \]

Where:

\( Gallons/day \) — Daily hot water consumption in gallons
\( 8.34 \) — Weight of one gallon of water in pounds
\( \Delta T \) — Temperature difference between incoming cold water and desired hot water temperature in °F

Explanation: The formula calculates the energy needed to heat a specific volume of water through a given temperature range, measured in British Thermal Units (BTU).

3. Importance of Solar Water Heating Calculation

Details: Accurate BTU calculation is essential for proper solar water heater sizing, ensuring adequate hot water supply while maximizing energy efficiency and cost savings.

4. Using the Calculator

Tips: Enter daily water usage in gallons and the temperature difference in °F. Typical ΔT values range from 50°F to 90°F depending on climate and desired water temperature.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical daily hot water usage?
A: Average household uses 60-80 gallons per day, but this varies based on family size and habits.

Q2: How do I determine the temperature difference?
A: Subtract your incoming cold water temperature from your desired hot water temperature (typically 120°F).

Q3: Why is 8.34 used in the calculation?
A: 8.34 pounds is the weight of one gallon of water, and BTU is defined as the energy to raise 1 pound of water by 1°F.

Q4: Can this calculation be used for other heating systems?
A: Yes, the formula applies to any water heating system, but solar systems require additional considerations for solar resource availability.

Q5: How does this relate to solar collector sizing?
A: The BTU/day result helps determine the required solar collector area, typically 20-40 BTU per square foot per day depending on location and collector efficiency.