SER Unit : SailSafe Energy Rating for Electrically Powered Sailboats

SER Unit

Sail Safe Energy Rating for Electrically Powered Sailboats 

Introduction

The Sail Safe Energy Rating (SER) unit is a standardized measure designed to evaluate the energy safety of electrically powered sailboats, including their capacity to safely navigate and "runaway" from adverse weather conditions. It assesses a sailboat's capability to maintain safe conditions by considering factors like battery capacity, energy consumption, and charging capability. The SER provides a comprehensive assessment of a vessel's energy autonomy, aiming to promote safe and sustainable practices in marine navigation. Its goal is to ensure that sailboats have sufficient energy reserves to navigate safely, even in challenging situations and during emergency escapes.

Before using the formula, it's important to acknowledge its limitations. The formula does not account for factors such as windage, currents, tidal effects, hull efficiency, and various energy losses, including battery degradation, mechanical friction, and environmental influences like wiring quality. Additionally, it assumes that the electric motor size matches the boat size and its weight. These considerations may impact the accuracy of the assessment and should be taken into account when interpreting the results of the SER calculation.

Formula 

The SER rating is calculated using the following formula:

SER: W 

​For SER², which incorporates charging capacity and time to full battery charge, the formula is modified as follows:

SAIL SAFE ENERGY Rating Safety Scale

The Sail Safe Energy Rating safety scale assesses the safety level of an electrically power Sailboat by considering its energy capacity. It provides various safety ratings to determine the vessel's preparedness for different navigational conditions. 

*The SER Rating, correlating with 1 hour of energy autonomy per unit, serves as a guide for users to evaluate their energy requirements within various contexts. For instance, individuals familiar with frequently enduring three-day storms may deem one day of energy insufficient, while those adept at forecasting might find 24 hours of autonomy adequate for escape. 

Explanation

The formula aims to offer a transparent depiction of the energy reserves aboard your boat and to evaluate your safety at sea using simple mathematical calculations. Our hope is that this tool will play a pivotal role in encouraging electric boat manufacturers to integrate a similar unit, or our own, prior to marketing their vessels. This unified adoption will facilitate consistent communication and foster a holistic approach to safety across the maritime community. 

How to use the formula

1^st : Gather the information bellow : 

Battery True Capacity: This is the total capacity of the ship's battery, measured in kilowatt-hours (kWh). It represents the amount of energy stored in the battery and available to power the ship's electrical systems.

Eg : A battery of 30kw has a true capacity around 28kw

Charging Capacity: This is the battery's charging capacity, measured in kilowatts (kW). It represents the rate at which the battery can be recharged, typically from renewable energy sources such as solar panels or generators, and contributes to the ship's energy autonomy.

Eg : 1 solar panel of 400w will produce in average around 1.2kw , in this example we use 2pcs or 2.4kw per day.

Engine Max Load: This is the maximum load that the ship's engine can handle, measured in kilowatts (kW). It represents the maximum power output of the engine for propelling the ship.

Eg : At 10kw your boat go 5.5kn and at 7.5kn your boat go 5kn (so in this case you won’t push the motor to the max and your true consumption is around 7.5kw

Safety Electronic Load: This is the electrical load required for the operation of the ship's electronic safety systems, such as emergency communication systems (VHF), navigation instruments, and autopilots. It is measured in watts (W) and ensures the continuity of critical operations in emergencies.

Eg : 500w

Other Electrical Devices Always "On": These are essential electrical devices that are constantly operational on the ship, such as bilge pumps, refrigerators, and navigation systems. Their electrical consumption is measured in watts (W) and contributes to the total electrical load of the ship.

Eg : 200w 

2^nd , apply the formula 

According to SailSafe Energy Capacity Safety Scale,

You are good for the day (with caution) – 3 hours is just enough for maneuvers.

How to interpret the result: 

For the day, you have to consider the use of the windlass for anchoring or maybe a bow thruster. So doing 1 or 2 maneuvers plus in an out of the harbor will require some battery management in this case.

By using this formula, we could advice to improve the setup by covering at least the safety load + the load of the devices always on. (such as the Fridge)

In practical terms, it's advisable to ensure that your solar panel setup can at least cover the combined load of essential safety systems and devices that are always on, such as bilge pumps and fridge. By doing so, you can maintain a sufficient level of energy autonomy for safe navigation and maneuvering, even when relying primarily on solar power.

Note that by adding a generator, you could feel safer. Of course, using a generator is a good way to charge your battery.

But in a situation of ‘running away’ from a dangerous situation, you can see that it won’t help much.

Eg : Caught in a storm at night (solar off), I start my 2.2kw / hour diesel generator. 

So using a generator of 2.2kw will only give us 16 minutes of extra energy. While it’s already good to keep the safety equipment on, we can understand that it won’t be enough to cover the power used by the engine.

We believe this example offers a clear illustration of the advantages and disadvantages of electric power, providing valuable insights into actions you can take to enhance safety on your journey.