We thought that our water supplies would pose the biggest challenge, but in fact we’ve discovered that our power supply is way trickier. We’ve noticed that the batteries are emptier every day, which means we use more than we produce. So big question is: do we need to invest some money into a new solar panel or a generator?
First we took a look at the solar panels. They are two 85 W panels, and on a fairly sunny day their output was 6 amps (together). According to factory information, these should be able to output almost 10 amps, so either they are old, dirty or the day was not an optimal day. If we calculate with their output in practice, over a day with 8 hours of sunshine they can maximally give us 6 * 8 = 48 Ah.
To cut a long calculation short, our daily energy use under sail is 140 Ah. Most of that is the refrigerator (48 Ah) and navigational instruments (80 Ah). On anchor we use only half of that, about 70 Ah. Again, most of that is the refrigerator and the rest just lights, charging our phones and the water pumps.
Notice how our total input of solar energy equals only the power demand of the fridge!?
The battery bank is 210 Ah, but using more than 50% decreases the life span of a battery drastically. So we’ve got 105 Ah to use, less than our daily demand on sail! We do tend to turn off the refrigerator at night, get a little bit of power from motoring now and then, and the calculation was pretty overestimating so we think the battery bank is right for our average usage.
The difference between our estimated average daily output of 105 Ah and estimated daily input of 48 Ah is 57 Ah. So, we now know that we lack energy. There are several options to bridge this gap:
– If we motor, we get 40 amps (with the new motor) of input so we would have to motor 2,5 hour a day. At 2 L per hour (guess, we are not sure how much the new engine uses), this is 5 L per day. If an ocean passage would take 20 days (very likely) that means 100 L of diesel. We could stock up on jerrycans and go for this option as it requires no installation of equipment and no initial costs of buying equipment. It’s not very green though.
– Adding a solar panel of 57 Ah * 12 V = 680 W. That costs around 400 euros and we would have to find one that fits on our bimini. Then it would take a day to install the panel and change the charge regulator. The advantage of solar panels is that they are maintenance free, downside is that we would be betting everything on one horse (the sun).
– Adding a wind generator. A wind generator works 24/7 and could also make up for cloudy days. A silent wind generator costs 1550 euros, and requires rewiring of the existing solar panels and an installation on a mast on the transom. A cheap one costs 400 euros but is probably loud. The advantage is that we would also charge our batteries during bad weather, the disadvantage is that it makes the transom look cluttered (ugly in my opinion).
– Adding a towing generator. This is a propellor on a stick you throw in the water which turns a rope connected to the generator by boat speed. A towing generator alone costs around 1500 euros. There are also towing generators on the market which can be transformed into wind generators (2000 euros). This makes sense because a towing generator only works when the boat is moving. The output of these generators is 4-6 amps, enough to fill up our battery banks. The advantage is that we would be betting on three horses (wind, speed and sun) but disadvantage is definitely the price.
– Adding a diesel generator. We are not really considering this, because it uses up space, stinks, is likely to fail or break, uses diesel and its expensive.
– The extreme green alternative: get rid of the fridge. We’ll just drink warm beers and go for canned food. I don’t think my crew can be convinced of this option (but I like canned food and I hate our deep top-loading fridge!)
Note: electricity seems way less important than say, water, in the overall scheme of survival or extreme situations. But we heavily depend on our navigational equipment and communication via VHF for a safe and quick passage! But we promise also to get a paper chart.
Edit: Our new engine has a 120 amp charger, but in praxis it only charges about 40 amps. Also, the charge capacity drops when the batteries are almost full. We tried to buy a secondhand towing generator, but we were ripped off and canceled it. Towing generators are very asked for these days! Unless we find a secondhand generator in the Canaries or Cape Verde, we will just stock up on diesel and rely on our engine.