By Kaare   |   2023-09-23 (update)

Hydrogenerator & Energy Usage

Perhaps the most important question for cruisers today is how to generate electricity for running the boat. To that effect it is a good exercise to make a calculation of the energy usage on board taking into account both when you are sailing and when you are at anchor.

On IRIS we have a fridge and a small freezer, as well as the usual electronics and lights. Our usage is 5-8 Amps when we are at anchor, and 10-15 Amps when we are sailing depending on how hard the autopilot needs to work. Furthermore, we have a watermaker, which makes 65 lph and consumes approx. 25 Amps. We run the watermaker for an hour or so every 3 to 4 days.

In the tropics, as a rule of thumb, we can get as much as 4 times the nominal effect out of our solar panels (4 * 600W = 2400 Wh or 180Ah @13V). That covers our normal use of electricity when at anchor (providing that the sun shines).

When we are sailing that does not cover the usage at all, furthermore then sun is not always shining. For instance, when we left the Galapagos we ran into some bad weather, and did not see the sun for 4 days. Therefore, you need an alternative way of generating electricity.

You can run your main engine, or you can run a separate small generator. We have chosen a slightly different way; in that we have invested in a hydrogenerator from watt&sea. The most common type is an external generator which is mounted on the stern and lowered into the water when you need it. That type fits very poorly on a German Freers designed Hallberg Rassy.

IRIS have a narrow “sugar scoop” stern. The distance from the water up to the stern is quite long and calls for a longlegged version of the generator. Furthermore, when the boat is heeling over you really need to fit the generator to the leeward side in order to ensure it reaches the water. Finally, the angled stern makes it complicated to attach the generator.

We therefore opted for the POD-600 version. The POD is permanently mounted on the hull under the waterline. Ideally it should be mounted on the centerline behind the keel and forward of the sail drive. On a HR42F with a shaft drive that is not an option. Instead, we have mounted it close to the keel and a little off to the side, approx. 40 cm off the centerline, and almost in line with the water intake for the engine. In that position it does not receive the full protection from the keel, only some.

Or experience from almost 20.000 nm is that this position works well. Even the millions of fishing lines and buoys off the Portuguese coast did not damage our POD. When we crossed the Atlantic, we ran into large amounts of Sargassum as every boat does. This algee is very tough, and is very likely to foul the propeller on the POD. It did interfere with the propeller and slowed it down quite a bit. However, for some reason turning it off and on again always solved the problem and it cleared itself of the Sargassum.

That is quite contrary to other cruisers we have met with a POD. Their experience was that the propeller on their POD fouled so much that it almost stopped working for the entire passage. Perhaps our position off center helps clearing the propeller of sargassum.

We have mounted the large diameter propeller, rather than the standard size. Our cruising speed is approx. 5,5 knots on the average. With that speed the POD generates a little less than 200W or 15 Amps. Running that for 24 hours a day yields 360 Ah. Going back to the energy usage, it is seen that the POD covers the entire energy usage alone. On the number of passages, we have made over the last year, this is also our conclusion. We are able to generate enough electricity when sailing to cover both the needs of the ship, and also run the watermaker every 3 to 4 days.

Are there really no drawbacks? Of course, there are negative things about the POD and its placement.

First of all, it is not silent. The POD is a bit noisy, especially when we are running fast. You get used to it, but a more silent version would be nice. To me it is the sound of free energy and I enjoy that, but I am also an engineer so that may explain my enthusiasm.

Secondly the position off center is challenging when you are hauling the boat out of the water. If you are craning then it is not a problem, however if you are using a hydraulic trailer, then you need to be very careful not to damage the POD.

Thirdly if you are going faster than approximately 7 knots you cannot turn it off. The internal brake can only handle speeds up to 7 knots. Watt&Sea states that you must turn ON the POD if the brake cannot keep the propeller from turning. This means that you will be producing quite a lot of energy, which you eventually cannot store in the batteries because they quickly become fully charged.

On IRIS we try to solve the problem by turning on power consuming equipment:

• boiling water on an electric kettle
• running the watermaker
• turning on the radar

Furthermore, we follow our power production/consumption closely using the Watt&Sea App, and if we predict that we will be running in excess on 7 knots we build up “energy-storage-space” in our batteries by shutting off the solar panels, and/or not turning on the POD before it becomes a problem stopping the pod from running.

Some of the problem can be mitigated by mounting a smaller diameter propeller, such as the standard propeller, however, then you reduce the amount of energy you get out of the POD.

The propeller design is actually quite nicely done. It is quite easy to change the propeller (or replace a damaged one). It can be done while the boat is in the water, preferably using diving equipment, but it is also possible doing it using simple snorkel and mask.

The installation of the POD is straight forward and quite thoroughly described in the installation manual. I have only a few tips/amendments:

• The POD needs 3 holes for mounting. Two for the mounting bolts and one for the cable. It helped a lot to make a drilling guide out of a 50mm thick piece of wood. First of all because the guide ensured that the drill was perpendicular to the hull, and secondly that all 3 holes were perfectly aligned with the POD when finished.
• Tracing the cable through the 90-degree fitting in the internal mounting plate is difficult, but if you take your time and do it slowly it can be done.
• In the manual watt&sea recommends using electrical connectors like the Waco 222. I will advise against using these connectors. Only a small misalignment of the cables in the connector will create a point of higher resistance, and if you go very fast the current in the cables increases to a point where heat in the connector can become a problem. Using the old fashion screw connectors of sufficient size is much safer.
• When watt&sea states that the converter becomes hot, they do not lie. The converter can easily reach 60degrees centigrade or more, so be sure to mount it in a well-ventilated space.

CONCLUSION

The hydrogenerator watt&sea POD-600 works as advertised. We have been using it for almost 20.000 nm, and when sailing it provides us with the power, we need together with our 600W solar panels. It is however a bit noisy, and that is the major drawback. In the end I would do it again if I had the choice. The only issue I see is if your boat speed routinely exceeds 7 knots. In that case you will not be able to stop energy production, which can be a problem.

APPENDIX

for some reason our POD stopped working between Niue and Fiji in the South Pacific. We got in contact with the support team at Watt&Sea, and after a number of tests the conclusion as that the POD was broke and needed replacing.

When the support team learned that we were going to have a haul-out on Fiji, and since our POD was still under guarantee, they arranged for shipping a new POD to us, which arrived 6 days later by DHL.

The replacement POD is apparently from a newer generation than our original one, because the noise level is markedly lower, which is a great improvement.

I can only applaud Watt&Sea for a very quick and efficient support team. They quickly responded, and helped finding a solution which got us up and running again on the other side of the world.