A cruising sailing boat needs to generate & store energy to power up all her working systems while being decoupled from the shore. When selecting Chloe's energy systems we had to make some non-straightforward calculations based upon some fairly loose assumptions & estimates. There are a lot of opinions out here about sailing boat energy systems, written on the web or in many books on the topic; however these system choices evolve technically. During each stage of their evolution, different systems may become more or less beneficial, more or less cost effective and more or less reliable, when ranked against their alternatives. Therefore new systems can 'over take' in terms of being the best approach to adopt, as things evolve.
Chloe is being built in 2018/2019; at a time when solar panels have reached 22% efficiency in the mainstream, when Lithium Phosphate batteries are reliable and cost effective but before diesel reforming fuel cells have become practical. Working at this time in history, dictates our broad choices for Chloe.
Lithium Phosphate Batteries (Not to be confused with LiPo, or Lithium Polymer) is a new, safe, mid energy density battery - broadly used in lower performance electric cars, lawn mowers, bikes and scooters. It's an ideal battery for yachts. You can see from this figure that it can store better than twice the amount of energy that a Lead Acid (AGM) battery can, per Kg; and for many more charge/discharge cycles.
Windmills, being mechanical, break down, but are becoming a little more reliable with each generation and solar panels still don't create a lot of power for a given area. Dangling Hydro-generators are still new, evolving very slowly, given the market size and are some what susceptible to breakage, perhaps grazing the forehead of a dopey whale or serving as an appetizing 'fishing lure' to a large predatory fish.
Our direction today is to (i) maximize the area of solar panels that will fit on the boat and (ii) to use the best silicon technology available for PV Cell designs.
Photovoltaic solar energy is 'space limited' on a boat. Where-as on a house, on land, adopting renewable energy is simply a matter of choice, in terms of dollars spent. A house can very easily be made to be 101% energy neutral - by installing heat insulation & lots of large, cheap solar panels on the roof or a nearby ground mount. We built our last house as such in California with no real issues other than simply installing a lot of PV panels. We solar power alone we had no annual electricity bill - and with that we also ran an electric car and irrigated a vineyard. On land, solar is a no-brainer.
Every thing in a house can be run from electricity. Cooling, Heating, Hot water and Lighting, Information & Media systems. But, on a boat, unshaded space is the limiting factor. We can only fit so many solar panels on top - no matter how many dollars we throw at the problem.
Wind mills take up space, generate shade and hydro-generation doesn't work whilst at anchor, unless we're anchored in a fast flowing river.... while somehow protecting our hydro generator's propellor from the inevitable debris that rivers bring...
Energy Sources, Storage & Generation Sources
We looked at a range of potential techniques to both store and generate energy on the boat. Summarized as follows:-
Batteries: Yes. And Lithium Phosphate for good reliability, safety, energy density, energy density, available BMS systems, safety and toughness.
Diesel fuel tank: - Yes. for massive energy density.
Propane tanks: - yes. For simplicity of cooking and energy density. With a set of adaptors. "Standards are a wonderful thing, everyone should have one...."
Hydrogen or reformable Hydrogen source tanks. eg. a Hydride or Petro-carbon. No. For lack of safety and lack of reliability.
Engine driven alternators - yes. and 2 for reliability. And high speed simple charging, if needed in the event of solar failure.
Engine Heating water - yes: Primary way to make hot water for showers.
Connect a shore line to charge up batteries and to power up electrical systems directly: - yes fro simplicity & care free use of power. And for hot water heating after more than a day of engine use. With a transformer and diode chain for galvanic isolation.
Windmill generator: No. Too unreliable. Too little bang for the buck. Creates shade on the PV panels.
Solar panels: - Certainly Yes. 1.1Kwatts. With Maximized area. For simplicity. And high performance reliable power. We need a strong reliable frame for mounting and individualized MPPT boxes. Use 60"- 96 cell SunPower X22 panels for maximum power per unit area.
Hydrogenerator: - Yes. for fun and for a back up.
Fuel Cells: - No. Nothing available quite yet that works with reformed diesel. Watching various companies make slow progress however. A 1 KW reliable, quiet diesel FC would be a nice system to have.
Diesel Generator: - no way Jose! Noisey. Unreliable. Heavy. And maintenance maintenance maintenance.. no Thanks!!!
Portable Gasoline Generator with a tank of Petrol/Gasoline: No Thanks! Kaboom!!
Energy scavenging systems: No. Research areas. Interesting. Magnetotrictive scavengers look interesting. A sheet block or an anchor chain. High force-tension, small displacement systems may become available based upon NIB magnets..?.
This list makes for an interesting set of choices and considerations.
We want of course to minimize the number and quantity of systems that can go wrong. We wanted to minimize the number of 'Moving systems' as moving parts fail faster than static parts or electronics. Electronic systems are inherently reliable, when compared to mechanical counterparts. Specifically this meant that we wanted to avoid the use of, any 'Rotating Generators', if we could. But we can't have it all. Sailing boats systems are about lots of trade-offs and compromises. The considerations are as follows:
Reliability
Maintenance
Simplicity
Install Space
Points of failure
Cost
Usage Models (Energy Source availability)
Pollution
Energy source availability
Energy Use & Generation Conditions
Of course, the amount of energy we need to create and store will depend upon (i) how much energy we will need to use in any given condition and (ii) now much energy we can reasonably generate at any given time. (iii) the amount of energy that we can create and use for a given state of boat life. Clearly, when sailing across the overcast ocean, or in big seas at night, 100 miles North of Scotland is a different situation to that when lying at anchor, in a calm bay, at noon, in the tropics.
We calculated our use & generation models based upon living on Chloe under each of these sets of different conditions.
11Kwatt.hours of Lithium Phosphate Batteries.
Central to the electrical systems is a big chunky battery bank - in Lithium Phosphate for reliability. This means 3x 300amp.hr, 12v batteries. 300Amp.hrs x 12v x 3 batteries = 900 amp.hrs @ 12v = 11Kwatt.hrs (About 10% of a Tesla battery).
900Amp.hrs of batteries might be considered normal for a 45ft sail boat when adopting AGM's, but Lithium Phosphate batteries are able to draw down their state of charge by around twice the amount when compared to that of AGM's. Thus they can store twice the energy by using Lithium ions. Chloe would therefore have about 1800 Amp.hrs @ 12v, of AGM 'equivalent' storage. Given our average daily minimal cyclic load of about 20%, this battery bank should last for 10 years as a minimum and be able to support any reasonable transient load or charging rate.
Given that we use Lithium batteries, we were far less concerned about controlling the rate of charge, being delivered to the batteries, as one would be when using older AGM Lead-Acid batteries. Lithium batteries are much tougher in this sense and don't require quite the level of charge rate baby-sitting that older tech, AGM's required. One of Chloe's 3 batteries can support a surge of 1000 Amps. The three in parallel : 3000 Amps. Theoretically : )
No Wind mill.
At a realistic generation rate of 50~200Watts, low reliability and space taken up on the sailing arch and the shading of installed solar panels; the windmill numbers just didn't make sense. We prefer the solid state for its simplicity & reliability. We have seen a LOT of broken windmills, over the years.
Solar panels
3x 360Watt solar panels are Chloe's primary electrical energy generation systems. A 4.5m2 array of well mounted and efficient solar panels. The best mono-silicon solar panels for a sailing boat application with limited area, means the panels that generate the most energy per unit area. Not the best in terms of $/Watt. SunPower from Sunnyvale, CA, Cells offered the best at the time of installation. We fabricated a large frame & secured it to the sailing arch. The size of this array was something similar in area to many sailing boat's hard dodgers. Each panel will be connected to an individual Victron MPPT box to maximize shade tolerance considering the inevitable mast & mainsail shading. This is an important sub-systems design aspect that offers a solution for sailboats that suffer from solar panel shading issues. Three MPPT's also provides for tripled up point of failure, redundancy; each being essentially an independent current routes to the batteries. In 6 hours of sunshine, exposed with say 60% of the Saraha's luminosity; this 3x panel array should generate 360W x 0.6% x 3panels x 6hours = 3.9 KWatt.hrs or energy per day. About 40% of our batteries storage capacity. 3.9KWatt.hrs is enough energy to cook and heat water with electricity without much need to burn propane.
We bought our panels in the UK and drove them over the channel in the back of a car, to France. (We found it prohibitively red-tape-ish to buy panels in France without a business license. )
We found a great supplier in the UK, whom we'd highly recommend.
Jonny Wilson
Oxford Solar PV
www.oxfordsolarpv.co.uk
50 High Street
Wheatley
Oxford
OX33 1XT
UK
Tel: 01865 875555
Fax: 01865 876005
MPPT boxes (Maximum Power Point Tracking) is a Small Power Electronics box that will modulate the switched power supplies of both the incoming energy from the PV panels and outgoing energy to the battery. By using switching transistors to briefly storing the energy in inductors, they modulate these two respective impedances to maximize the energy flow efficiency. This is needed as the relationship between current and voltage that a PV panels will put out, is non-linear. An MPPT box will continuously monitor and assess the best impedance to present to both the PV panels and the batteries. In other words, they squeeze as much power out of the panels and into the battery as is feasible.
We included 3x 100 | 50 Victron MPPT boxes for the main 3x solar panels. These are rated at 100v max and 700 Watts of max. power each. So operating at half rating will mean the transistors are therefore oversized and offer low resistance, leading to less self heating and greater reliability. Fire is always a sailboats worse enemy - we always have to keep it in mind. The SunPower panels run at about 60v and 360Watts max, so the MPPT's are each running well below their maximum operating specs.
They are also capable of being monitored via Bluetooth links.
As either back up or expansion for solar power, we installed some extra future-proofing MPPT 'channels' for future projects. Perhaps to better balance the demand/generation relationship that we discover we need, empirically. These options include perhaps either : 1. A bimini solar array, where-by we might plan to add 8x long & thin 50Watt flexible Sunpower cell arrays into the folds of the bimini. Attached with zippers and velcro.
Or, 2. An extra mini-array of square 50W flexible panels, glued to the underside of the main panels, facing down. These would capture sunshine reflected from the sea - although the dinghy would get in the way to some extent. If Bifacial solar panels can generate a 20% boost, then this 'adder' might deliver an additional 60~80Watts?
These back up MPPT boxes, ready for more power, are smaller and rated at 290Watts each and a maximum voltage of 100V.
2x Volvo alternators.
Our Diesel engine is a 75 hp Volvo Penta D2-75. A turbo charged, 4-cylinder engine that doesn't like to be run at low load. We installed two 115Amp alternators, each on it's own belt. This offers both reliability , though redundancy - double the load of a single alternator and about (2 x 60A) = 120Amps x 12v = 1.44Kwatts of charging power, while motor sailing at a nominal 1500 rpm. If we had to charge faster, for some reason, we could 'rev up' the charge current to 230Amps. but we would be thinking about over heating all the time! Each alternator has its separate, dedicated smart charger from Stirling.... sorry I mean Sterling. If a belt snaps, we'll still have one running.
A Watt & Sea Hydrogenerator.
We considered this a back up system, and, perhaps an interesting toy. It might be capable of generating a couple of hundred watts, reliably and might even balance the energy usage of our heavy duty autopilot. We will form an opinion in the years to come, after we have enough experience to know anything about what we're talking about.
Boat's voltage
We stuck with 12v, as opposed to 24v, out of design simplicity and to take the complexity away from the required battery cell balancing, imposed on the integral battery management system (BMS).
An additional, 110amp hours of bow thruster/windlass battery was added, to prevent the 500amps or so of transient current, from having to run up the boat's length. It's charged at 20amps max from the house bank.
We installed a combined Philippi and Victron energy monitoring system and we'll write a bit of software to log and even optimize the various uses around the boat - one we have figured out how to tap into the various CAN buses. We added a shunt to the hydro generator and to the combined PV array so that we can monitor the total solar power level in real time.
Shore Power
Being docked along wide a marina with plenty of available electrical power is perhaps the simplest set of considerations. For this sweet of requirements we stated with a solid shower power plug. A good long 15m cable and a SmartPower plug and socket. The SmartPower shore power plug design is a step up in design solidity. Over the years we have seen two many boats with a shower power plug that is wobbling and almost falling out based upon a very old design. These types however are great in either 110v-3-pin or 240-4-pin versions!
110v and 240v Smart Plug Shore power connections for super solid power plugs. They just don't wiggle loose. We love them.
For shore power isolation, being an aluminum boat, we needed an isolation transformer. This provides boat a chunky isolating transformer and some fat, fast, back to back diode chains in series with the ground wire, to provide a little voltage barrier, to prevent any galvanic currents.
Also a 3KWatt switching inverter so as to be able to handle power tools and kettles, hairdryers, space heaters and kettles of hot water for tea.
A small battery charger
Most typically we'd stay at least a night in a marina with shore power, so that a small 700Watt charger would be more than sufficient to supplement the solar panels charger rate for if we were living with a lot of energy usage - for some reason. We find we only run it at about 400Watts to avoid any of it's system fan cooling from ever switching on. This we find, is plenty even for a situation when we have several stormy, overcast days leading to only a little solar radiation.
Note that a shore power connection is not ONLY about charging batteries. In addition, when plugged in to a 16Amp shore socket, we have an available 16Amps at 240v of direct shore power. This is automatically switched in via the Victron Phoenix Inverter. 16 x 240v = 3.8Kwatts. More than enough to run a kettle, electric pressure cooker, hair drier and space heater.
We find our small 500W space heater is an ideal way of heating the boat's insides without burning Webasto heater diesel. We can even run it for 30 mins with our solar/battery system.
In arriving at this set of power and energy design conclusions, we considered the following use case conditions, to make sure we should not have an issue.
Use Conditions for when considering a boat's electrical power systems
Condition 1 : On the Dock at a Marina
This is the simplest 'energy position' to be in for the obvious reasons. We provided for a 16amp/240v and 30Amp/110V 'international' shore power connection. We would therefore be able to pull up 3 KWatts of power from the shore and charge 12v batteries as fast as our battery charger unit would support (60amps at 12volts ~ 720 Watts). Given that we would would typically be sitting at a dock for some hours at a time, a charger of 720watts would be a practical size. Our ~10 Kwatt.hr 'empty' battery level requirement would therefore take about 14 hours to top up to 100% - this only in the unlikely event that there we completely depleted when we pulled into a dock.
The shore power connection would be 3 Kwatts, so that only a quarter of this power would be directed towards the battery charger. But this would be fine.
We considered that more than likely, we would spend a night at the dock, hooked up to power - and so we would end up as fully charged, by the next morning. In reality the PV panels do nearly all the work.
During this time we could use all the power we wanted to. Run all the electronics, fridge, freezer and lighting, hair drier, kettle. We would not run radar, AIS, auto-pilot, Nav gar, bow thruster or winches on the dock.
We also want to charge our pair of e-scooters which require about 80Watts for 3 hours a day, each. Shore power takes care of this load, as, for some reason we never seem to use the scooters when at sea.
Condition 2 : At Anchor or on a mooring buoy
At Anchor we are on our own, for power. We would generate power during daylight hours with our solar power array and top up as needed by running the main engine. We would not be running the auto pilot, but we would be running electronics, lights and the fridges. This condition meant that we needed to install the solar panels as best as we could as these would be our primary energy generators. If needed we would most likely have the Bimini deployed and generating power from these secondary Bimini solar panels also.
If the anchorage had good looking clean sea water around, we may also choose to 'make water'. This would mean running a DC 600Watt motor for several hours, during which we most likely NOT have to run the main engine. The same consideration holds for running the small Hookah diving compressor, at ~700Watts.
We also have charged up our pair of ~1kwatt.hr scooters while hanging on a mooring. This means we have had to manhandle the scooters into the dinghy... doable and actually made simple with Chloe's easy swim platform
Condition 3 : Underway, Passage making in the mid-lattitudes
Boating in the mid-lattitudes means over-cast cloudy weather. We would draw heavy loads from the Autopilot. Not optimum for small solar panels. As a rule of thumb we can derate the amount of energy produced by a solar panel by a factor of 40 to 50% during overcast, stormy or rainy conditions.
We would be relying on engine alternator power and experiment with the Hydrogenerator. Our Larger than standard batteries means that we can bridge the times between sun shine days, at least to some significant extent. We sized the batteries for 2~3 full days of use in these darker conditions.
Condition 4 : Underway, Passage making in the tropics
Whilst underway we wanted to make sure all energy systems we fully functional and available. The most 'dangerous' time to run a boat, is obviously whilst at sea, but is also the essential 'whole point'. In the tropics, during the day light hours, we would be generating a good amount of energy via the solar panels on the arch. The Bimini would perhaps be folded away when winds exceeded 30 knots. In the case of a short hop between islands in good weather we may have the bimini up and would therefore could add solar generating area. We would most likely, avoid making water, while underway; saving this task for when we were stationary, but sitting in clean sea water at anchor. We would monitor the battery levels carefully when running the autopilot - especially while sailing at night. The hydro generator would be another reasonable option during these times. Our major sources of energy usage would be the Autopilot in heavier seas and, or course our two refrigeration systems.
Condition 5 : On the hard.
We would rely entirely on the arch mounted PV and wind systems and use minimal power on board,. The water maker would be pickling and thus 'off'. The engine would not be available without water cooling. We could live 'cleanling' & sleep on the boat - while on the hard, but using a marina's bathroom facilities.
In practice the PV panels are more than enough.
Condition 6: Motoring or Motor-sailing.
While running the main engine's we could generate a good level of power. We installed two alternators, each rated at 115Amps. Under normal conditions, motoring at 5 knots, this means that the two alternators together produce about 100Amps at 12v or 1200 watts. A fully depleted house battery bank, requiring ~10 Kwatt.hrs means that motoring for ((10000 Watt.hrs / 1200 W) = 8 hours) would fill our house batteries from empty. With our solar, we would not need the motor at all for all but perhaps night time, heavy weather sailing with the autopilot running at full tilt. We could run the motor at a high rate of power generation but would be cautious of over heating the alternators and excessive fuel burning. We will try to treat engine running as an 'opportunistic' time to use energy.
Summary and Conclusions
After our first year, we have found that this system has performed a little better than expected. We have not run out of energy on any occasion. We have never had to react to charge the batteries, although we have quietly monitored the system's natural perfomance. We have pugged into shore power on occasion, but not because of battery charge necessity; instead only for hot water, for when docked for more than a day after arriving at a location. (Hot water is created by engine heat exchanger so that it is hot upon arrival at a dock. It will stay hot from this engine heat for about a day. After that, we either plug into shore power or run the webasto heater to heat more water. Dawn's Orders being the compelling reason to do so. )
Our house batteries have not dropped below 75% to date. The worst case being in stormy weather without being plugged into shore power and without running the engine for a while. ie. On a mooring buoy in bad weather. The powerful solar panels do the heavy lifting and perform very well. In South UK, France attitudes in Spring time we get 50% of rated power from them. 50% of 1.08Kwatts is 550Watts for 6 hours a day = 3Kwatts.hrs/day. The twin alternators will top up the batteries in a very short space of time, if motoring. Often when leaving port early in the morning, we will leave with 85% battery charge. So, while motoring for 20 mins, out of the port in the early hours, we find the batteries are charged up fully before the sun comes up.
We boil two or three kettles of boiling water a day and run the electric pressure cooker daily with this solar energy. We run two laptops and 3 iOS devices. Charge Scooters. Watch TV and run internet router, switch and WAP. All with PV power.
We expect in gloomier climates that batteries will be drawn down more, but still with plenty of battery capacity wiggle room. We feel that the choice of 1.1Kwatt of PV and 10Kwatthrs of batteries - this sizing is approximately perfect. As a result, Dawn is now talking about tossing out or propane cooker and buying an induction cook top. Hmm... it's still shiny.
Over Time we plan to summarize Chloe's energy generation and use performance and perhaps adjust our systems or conclusions accordingly.
We'll post our continuing learnings as blogs along the way... Also we'll write about the best appliances and loads we discover.
- dawn
