This is probably the most important element of the electric picture. If we have to generate electricity using fossil fuels then all we have done is move the fossil fuel from one source and time to another. On the other hand if the electricity that we store comes from renewable sources then we can look at fossil free cooking, cooling, heating, lighting, navigation, dinghy outboard and one day full engine power for the whole boat. You can see by the number of those areas without links how much more writing I need to do.
On-board renewable energy generation
We are starting from zero here. Nothing on the boat at all and no supporting infrastructure (cables etc). There are 3 main sources of renewable generation commonly used on boats. Solar, Wind and Water. Sadly our boat has shortcomings when it comes to all of these which make it all rather challenging.
Until I started researching solar panels for boats I didn’t realise the impact of shadows on solar panel performance. It takes very little shadow to reduce the output of a whole panel (or even a whole series of panels connected together) to almost zero. Unfortunately sailing boats have a whole load of shadow creating rigging (masts, booms, stays, sails, sheets) and other equipment (radar, aerials etc).
Also we all know that solar panel efficiency is greatly affected by the angle of the panels to the sun. Again this is tricky on boats as they roll, heel and change direction.
Finally, solar panels become less efficient if they get too hot. So fixing them to a flat surface (such as a cabin top) without ventilation reduces the efficiency (but adding ventilation means that you have strength issues if they are in places where you need to walk).
The easiest boats to add lots of solar power to are catamarans, as they are so much wider they have huge areas of deck space (and large cockpits that can be made more comfortable by adding shade from solar panels). We don’t have a catamaran (and not because we would not have liked one, just they are way outside our price range for purchase, maintenance, storage and mooring).
When it comes to monohulls then the most common solution is to build a “radar” arch across the stern and mount solar panels on this (sometimes with the option to tilt them to face the sun). See this video from the wonderful Kika and Dan on Sailing Uma for how they did it (first time around).
Unfortunately, even here we have extra challenges. As a rather traditional design our Rival 38 has many advantages when it comes to seaworthiness, however, compared to modern boats the stern is quite narrow which restricts the size of panels that can fit on a “radar” arch. Also, Vida is a ketch so we have two masts and rhe mizzen mast is set well back with a boom that extends to the very end of the boat. That means that any solar arch would need to be a gantry extending out beyond the end of the boat. The structural challenges are not too great but there are implications on the cost of moorings and storage (typically charged by length) and it would likely be vulnerable to damage in lots of situations.
Using a wind generator seems obvious on a sailing boat. They too are not without their challenges (and again our boat makes some of these more difficult).
- Power: They work best in stronger winds. However, generally by choice you anchor in sheltered places protected from the wind for comfort, exactly the opposite of what you need for effective wind generation. When long term sailing the goal is typically to sail downwind whenever possible (much more comfortable and faster). When sailing downwind the apparent wind speed is reduced (true wind speed less boat speed) often making wind generation ineffective.
- Mounting. Again our mizzen mast makes things more difficult. We can’t just mount a supporting pole on the back of the boat as our mizzen boom sticks out so far. This doesn’t just affect the vertical pole but also the supporting braces. One option with a ketch is to mount the wind generator on the mizzen mast. Typically on the front about 1/2 way up (exactly where our radar is at the moment and where it would get snagged on the potentially very useful mizzen staysail). Another option is on top of the mizzen mast which keeps it well out of the way of everything including me when it needs maintenance (as the boat rolls the top of the mast moves pretty dramatically which puts a lot of strain on the wind generator and means that it is moving rapidly which affects it spinning).
- Noise: Wind Generators have a reputation for both noise from the spinning blades and from vibration echoing through the supports. Not great for us as our main sleeping cabin (at least when we are not on passage) is the aft cabin which has the mizzen mast stepped on it and where the braces for a pole at the stern of the boat would be mounted.
In recent years water generators have been gaining popularity. Essentially they look at little bit like an outboard engine with a propeller on a shaft off the back of the boat. As you move the water spins the propeller which generates electricity. For us a couple of concerns. One is whether we can sail fast enough to generate much power. Second is that there isn’t a lot of space on our narrow stern, especially if we end up with a windvane self steering (which would probably reduce our energy consumption by more power than the generator would add).
Initially, we are going to try to break all records for the amount of solar we can generate given the challenges we face. That will include us moving the panels dynamically to try to make the most of them. More in a later post.