People often ask me how we keep food cold on long ocean crossings. Well, we use the refrigerator and if we want it really cold then we use the freezer! Then the question arises, “Where does all the electricity come from?” So I thought I would write a little bit about how we manage electrical usage on Koinonia. Keep in mind as you read this that Koinonia is a very modern boat and quite luxurious compared to some sailboat provisioning. I spoke with one sailor here in Horta who had “refrigeration” on his boat only for about two days until the ice in his cooler melted…
Managing electrical generation and usage is a lot like managing a financial budget. Just like a monetary budget has an income or the money that you have coming in, the boat has various means for generating electricity. When you get some money coming into your budget you generally would store it in a bank account until you are ready to spend it. On the boat our electricity bank is a set of big batteries. We call them the “house” batteries to distinguish them from the engine-starting batteries. In your financial budget you have various expenses. Some of the expenses are considered essential and must “come off the top” before optional or luxury items can be purchased. On the boat we have electrical needs that are considered critical as well. There are also some things that are considered optional uses for the limited energy available to us.
Electrical generation on the boat can be divided into two classifications, renewable and non-renewable sources. The renewable energy sources on the boat are a pair of solar panels and a wind generator. The solar panels are rated at 260 watts. So if it is a bright sunny day and the angle of the sun is good on the panels we can generate enough electricity to keep two very bright light bulbs lit. But instead of using the energy directly to light bulbs, it is stored in the house batteries. The wind generator makes electricity from the power of the wind. It does not generate wind from electricity as the name may imply, otherwise we would just call it a fan. The more wind we have, the more electricity the wind generator creates. The electricity generated by the wind generator is also stored in the house batteries.
The theory behind choosing these two methods for electrical generation is that on windy days it may very possibly be cloudy. A low pressure system typically makes for cloudy, windy days. On the other hand a high pressure system usually is very calm yet the sky is clear and sunny. Other days it may be both sunny and windy and we get some good energy generation. Also some areas of the globe historically have constant winds and other areas are historically sunny but lack a reputation for reliable wind sources. So having both of these forms of renewable energy sources on board provides a good balance under the broadest conditions for sailing vessels.
There are two sources of non-renewable energy on board as well. The engine of the boat will charge the batteries when it is running. The engine runs on diesel fuel which is of limited quantity on board so this method is non-renewable. We also have a diesel-powered generator on board. It outputs 5,500 watts of energy, making the generator a very strong source of non-renewable energy. It can re-charge the batteries completely in a few hours.
On the expense side of the equation we have a few items which are left powered on all the time and considered relatively critical by the crew. Keep in mind that nearly all of these items are luxuries in the minds of some sailors. One may still meet a sailor who rebuffs all modern technology and still does things the way it was done in the past. The more complexity you have and rely on, the more likely it is that something will break that you cannot fix yourself.
The refrigerator and freezer are very important to us. We have prepared a number of our meals ahead of time and they are vacuum packed and stored in the freezer. We can just drop the vacuum bags into hot water to prepare the meals. If we lost the freezer, we would either have to quickly eat all the remaining food in one big feast or some of it would go bad and be wasted. We could probably live without the fridge if we had to. It tends to hold luxury items such as butter, cheese, lunchmeat and cold water. We keep both of these appliances powered on nearly all of the time.
The only exception for keeping power to these devices is when trying to use the radio. One or both of them generates some extremely bad radio frequency (RF) interference. It creates an overall noise level much higher than the natural RF noise floor. It also generates a pattern of beeps and blips as you tune to different frequencies up and down the dial. The interference is so bad in some frequencies that it makes them unusable. As it happens, one of my favorite frequencies is 14.300, the Maritime Mobile Service Network is centered right on some bad bleeping. So when doing any radio operating I turn off the fridge and freezer. Most of the time I remember to turn them back on.
The next item that is (or was) considered to be essential in our power budget was the auto-helm (poor Otto…). The auto-helm is the system that will physically steer the boat for us. It interfaces electronically with the GPS, chart-plotter and wind instruments and moves the rudder with a screw drive to keep us on the course we select. The auto-helm is a power hungry device because it is doing a lot of physical work moving the rudder back and forth all the time. It is rated at about 7 amps so it can be a big draw on our energy resources. After Otto died on our Bermuda-Azores leg all that extra power was money in the bank, baby! We were power-rich after that and could run anything we wanted (except the auto-helm). But I would still prefer having Otto back instead full batteries any day.
It is important to have the sails well balanced with each other and to the wind conditions. When properly balanced, the forces needed to keep the boat on course are significantly less than when not balanced. The auto-helm (and us) work much harder when the boat is unbalanced. I am still learning how to do this balancing, Charlie and Don are very good at it but don’t seem to be able to explain it well enough for me to understand. I think it is more art than science.
There are two ways that the auto-helm can be set up for navigating. Using the first method causes the auto-helm to go on an absolute path from one specific point to another specific point regardless of what the wind is doing. The second method allows you to tell the auto-helm to automatically keep you a certain number of degrees off the wind.
The first method ignores what the wind is doing completely. Otto assumes that the humans are making the proper adjustments to the sails to enable him to take the boat where he is told. If the wind or wave conditions change while in this mode and you do not adjust for them it may cause the auto-helm to work much harder than it needs to. Eventually Otto will just throw in the towel and give up. It’s his way of telling you to pay attention to what is going on.
When using the second method, you ride along with the wind, if the wind shifts, your course changes as well. This is easier on the boat (and the crew) as long as we don’t care which way we are going because it does not fight trying to make the boat do something that the sails may not be set for and it keeps the crew from constantly changing the sail set as the wind changes. Fortunately, at sea the winds will stay at a pretty much constant direction for days and days which is really nice if they are favorable to where you want to go. It can be more than a little irritating if they are not favorable to your destination. Watching a negative VMG (velocity made good) for very long or beating into the wind for days does not make for the most pleasant sailing experience.
In order for us to know where we are, what our speed and course it and what the wind conditions are we rely on the instruments on the boat. This is the next category that is deemed to be power-essential. The instruments are left on all of the time while under way. The radio and AIS receiver are usually turned on at the same time and are left on as well, they all work well together. Plus the switches for these items are all right next to each other on the electrical panel. So a simple triple-finger switch flip gets all the navigation systems going.
All of the electronics on board are integrated into the RayMarine sea-talk system. The GPS sends location information and the central control unit sends that data back out to the chart plotter. The chart plotter places the boat position on the map on a computer display that is right at the helm of the boat. This is the main instrument one keeps track of while under way. It is a back-lit display and can be set to be quite bright for visibility in bright sunlight. At night it can be very bright even when turned down, I like to keep it way down or near off when I am not using it so I retain night vision. My guess is that the brightness of this display is a big power consumer.
There are a couple of wind instruments located at the top of the mast. One of them is the anemometer which tell us the strength of the wind. The other is a wind vane which tell us what direction the wind is coming from.
Remember that both the anemometer and the wind vane can only give us information relative to the boat. If the boat is moving through the water at 5 knots and the wind is blowing at 20 knots at an angle of 40 degrees off the port bow then a strict reading of either instrument would be helpful but not accurate. In order to be accurate and give us true information we need some other inputs and some computational power.
There is another sensor which is a little wheelie thing under the water on the hull of the boat. This sensor feeds our speed through the water into the main computer. We also have the GPS which can tell our true course and speed over ground. When all of these inputs are collected they can be processed using the RayMarine system to output much more useful information.
The RayMarine computer can use it’s program and something called “trigonometry” to calculate the “apparent” wind speed and direction. To the sailor, these are much more useful figures. It tells you how you are doing relative to the wind. Both the True and Apparent wind and speed are displayed on the chart-plotter screen so you always have access to both.
The chart-plotter display is packed full of other useful information as well. If you have a destination waypoint set there is always a little line from the boat to your destination. A quick glance tells you if you are close to being on course. One of the data fields present on the screen is XTE (Cross Track Error). This tell you how far off the track you have drifted. It’s a way to judge how well you are doing when trying to manually steer a track. It can be quite useful, especially when motoring. Fortunately there is an easy way to reset the XTE and I find it helpful to do so just before the end of my shift. Charlie is known to make a 90 degree turn near the end of his shift to get back near the track.
The second most important instrument as we are sailing is the wind direction meter. It is a smaller display near the chart-plotter that has a picture of the boat in the middle with a needle that swings around the boat, indicating where the wind is coming from. It also has a digital readout of the wind speed. You can set this readout and the needle to indicate true or apparent wind with the press of a button. While sailing one tends to watch this display almost as much as the chart-plotter. Once the sails are set to our course and wind you need to maintain the same direction relative to the wind for optimal speed and angle to the waves. That is the exactly why you keep an eye on this little meter.
Those are the main critical energy consumers on board that are kept on constantly. There is another electric powered system that is just as critical but does not consume energy all of the time. But when you need it, you really need it. The water maker is only run every few days but it takes quite a bit of power when it does run. We frequently run the generator or the motor when making water just so it does not deplete our house batteries too much. The water maker uses a process called reverse osmosis to convert sea water into drinking water. It will make about 8 gallons of water per hour. As long as we have energy, we have drinking water so it saves us from having to carry a lot of water and allows us have the occasional luxury of a fresh water rinse while under way.
As the water maker works the fresh water is stored in a couple of big water tanks. In order to use the water in the tanks there is a pressurized water pump system that makes the faucets work just like they do in a house. This water pump is generally kept on most of the time as long as it is working OK. It only uses electricity when the water is flowing.
The SSB radio is a critical (IMO) electricity consumer which is only used occasionally. We use the High Frequency radio for getting weather fax, sending and receiving e-mail via WINMOR, receiving Marine Safety Information reports, checking into nets, chatting with hams and other sailors and of course it would be critical in case of an emergency.
The last system that is a critical consumer of electricity but not a constant use is the heads. Flushing the heads uses electricity and fresh water. This is a critical system. Even though it is a luxury to have electric flushes and I like the way it works, I wish there were some manual backup system in case of a catastrophic electrical systems failure. I guess the P-lines are our backup system.
Optional items that use electricity include items such as room lighting, fans, the entertainment system (TV, DVD player), microwave and the water heater. We typically use personal lighting systems such as headlamps or flashlights so it is rare to have a room light on, maybe only during cooking or meals. It also tends to wake someone up because there is usually someone trying to sleep. On the last leg we were power-rich due to Otto being off. We also had some extreme winds for days in a row which kept the battery bank actually too high a voltage level. We were looking for things to use the electricity to keep the batteries from being damaged by overcharging.
Most of the other items that are frequent consumers of electricity are battery powered and need to be re-charged occasionally. Some devices can recharge using 12v car adapters and other devices need AC voltages and current. We can produce normal household AC power from the house batteries by turning on the “inverter”. There is some overhead involved in using the inverter but it is an essential element to a well designed electrical system on board a boat. It costs approximately 16% to run the inverter itself then There is additional overhead using a charger which typically converts back to DC voltage at the levels required for each specific device.
Well, that is a brief summary or how power is generated, stored and utilized on Koinonia while we are under way. Hopefully you found it to be entertaining and educational as well.