How to estimate power needs for a long offshore trip?

Calculating Power Needs

To estimate power needs for a long offshore trip, consider the average daily energy consumption of your vessel. This includes lighting, communication, navigation, and water purification. A common starting point is to allocate 10-20 watts per person for lighting, communication, and other appliances. For a 4-person crew, this equates to 40-80 watts per day. Additionally, consider the power requirements for navigation, such as GPS, radar, and VHF radios, which can range from 1-10 watts per device.

Determining Battery Bank Capacity

To determine the required battery bank capacity, consider the daily power needs and the expected solar panel output. A common rule of thumb is to size the battery bank to provide 2-3 days of power in case of cloudy weather or reduced solar panel output. For a 4-person crew with a 40-80 watt daily power requirement, a 100-200 Ah battery bank would be suitable, assuming a 12V system and a 10% depth of discharge.

Selecting Solar Panel Arrays

For a marine solar system, flexible panels are a good choice due to their durability in a salt environment. Consider a panel array with a peak power output of at least 400 watts, assuming 10-20% efficiency. A 400-watt panel array could provide 20-40 amp-hours of energy per day, depending on the solar irradiance and panel efficiency. Use a charge controller to regulate the energy flow from the solar panels to the battery bank, ensuring safe and efficient charging.