We are delighted with the response and feedback we’ve received so far and we think it’s great to be able to communicate and respond to you all.
Some have correctly identified ‘unlimited range’ as something worth defining more critically. So we thought we would take that task on in today’s blog. When there’s no sun or wind, you’re not sailing around for free. It’s all about management and planning.
At the very heart of CMG is the calculation of your battery state at the end of your journey. Whio II’s energy model is based on an itinerary around the Mediterranean, the Bahamas, the Baltic, and Alaska with 4500km (2500nm) and about 22 stops in each region. The journey is planned in advance with a fixed arrival time at each stop. The weather data from several different years is then applied to the model to see if Whio II can travel at a minimum of 5kn and arrive at enough battery charge and water to last for the stay and provide for shore trips, fishing trips, waterskiing and other leisure activities, as well as providing power to the tender, and all house loads.
Not only is all this possible, but there is enough energy to afford quite a luxurious lifestyle aboard. On occasion the weather will not abide to the needs of the vessel. This would drain the batteries and obviously be a major concern. However, in the model we looked for periods of weather 2-3 days prior with moderate to strong winds, where Whio II can sail around in what we call ‘supercharging mode’.
The vessel is slowed down to around 3kn by the specialised trailing-edge propellers, and charging at 50kw is achievable. This engineering has been independently verified twice. The end result is that you can prepare for long journeys through poor weather when there is no sun or wind by pre-charging the batteries. This is analogous to charging your E.V. before a long road-trip.
The energy model shows that on average, the supercharging (sailing around required to charge batteries, but not to travel anywhere) makes up less than 1% of the sailing hours for any given period. Here is a graph showing just such charging events in the Bahamas.
To the left of the blue arrow shows where our energy is declining with demand from the tender and house loads. On the morning of the 23/09 we have to be in another harbor, so two days prior we take advantage of the good weather we have and fully charge the boat (indicated by the blue arrow). The actual journey costs us half our 200kWh energy (indicated by the green arrow). The weather is hot and we have visitors, so the tender is used for extensive watersport, exploration, and fishing. On the 28/09, we take advantage of a passing front for a hour of supercharging (indicated by the pink arrow), and have enough energy for exorbitant use of the full air-condition system, letting the batteries to as low as 30%, but we don’t mind this, as we know that the normal trade winds have kicked in again for our next island-hop and we can travel and charge at the same time.
In our eyes, unlimited range means no restriction on travel days, destination, or lack of power for comfortable living aboard. We have to manage the energy and we will live by the forecast.
We’ve used the same load profile on other years’ weather data to see if this can be achieved, and yes it can. Three months in the Bahamas showed 15 hours, 7 hours, and 5 hours of supercharging mode events in their respective year’s weather data. Using active management will not eliminate extreme weather anomalies, but normal yachts run out of diesel and water too, without proper planning and preparation.
Unlimited range for an all-electric, zero-emissions sailing vessel. We hope you’re as excited as we are for the future!
Thank you to everyone for showing your interest and helping us spread the word about CMG and Whio II!