Sailing off the Grid. Nigel Calder. (c) Nigel Calder

Transcription

1 Sailing off the Grid Nigel Calder

2 Unplugging the shorepower cord: At dockside, the shorepwer cord acts as an umbilical cord; AC power is the primary energy source; its availability is more-or-less unlimited At sea, in the absence of a constant AC source, the DC system is the primary energy source; the availability of DC energy is strictly limited The DC system is rarely, if ever, adequately tested at dockside to see if it has the necessary capacity All too often, once away from the dock the DC system crashes: this is the #1 problem on cruising boats

3 The unhappy life of a cruising boat s batteries

4 Getting the system in balance: We must either create appropriate energy sources to meet the demand, or Reduce the demand to match the available energy sources The first task is to calculate the demand This is generally done assuming the batteries will be recharged once every 24 hours

5 Determining demand:

6 At sea versus at anchor: On sailboats, the load should be analyzed for both passagemaking and also at anchor The passagemaking load is often higher because of the autopilot, radar, and navigation electronics The highest load is in the evening (you add the navigation lights, cabin lights, and often entertainment systems) Underway, powerboats have a continuous source of power (similar to being plugged into shorepower) At anchor, in the absence of air conditioning (which generally, but not necessarily, requires a generator), refrigeration and lighting are normally the greatest loads

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9 Calculating solar power contribution: Single crystal, polycrystalline & amorphous Up to 22.5% efficiency, including semi-flexible (e.g. Solbian); cost of mounting vs. cost of panels Maximum Power Point Tracking (MPPT) regulators The effect of heating & shading parallel versus series installation Calculating output the 3-hour rule (versus 4.8 for home power) - e.g. a 55-watt panel = 3x55 = 165 watts = 165/12 = 14 amp-hours

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11 Wind generators differentiating features: The key output power number is from knots wind speed Kick-in speed Voltage regulation/speed control & where it is Ease of shutting down Noise Ease of installation Cost

12 These solar panels keep up with the entire load when at anchor; the wind generator keeps up with the load in wind speeds above 15 knots

13 Worst case planning: The worst case load should be the starting point for planning Credit can be given for alternative energy sources: Solar panels: estimate the output on the basis of 3 hours a day. Wind generators: output rises disproportionately with an increase in blade size. Key wind range is knots. At sea, boat motion will substantially reduce output Water generators on sailboats: very effective at boat speeds above 5 knots but may be a hassle to deploy and retrieve

14 We now have a DC energy requirement number

15 Meeting the energy demand: PbA batteries are the limiting factor At every discharge cycle, some internal damage occurs The deeper the discharge, the more the damage: the depth of discharge must be limited

16 If a PbA battery is kept in a partially discharged state (partial state of charge psoc), it suffers damage from sulfation Periodically, it must be fully recharged

17 A full recharge takes a long time: 25 Charge Rate versus State of Charge ('typical' voltage regulator setting) Charge rate in amps (100 Ah battery) % 60% 70% 80% 90% 100% Battery state of charge as % of full charge Charge rate

18 The mid-capacity rule: The level to which batteries are discharged must be limited: with conventional batteries the goal is normally no more than 50% The level to which they can be readily recharged without excessive engine-running time is typically no more than 80% In which case only 30% of nominal capacity is used in everyday life Therefore battery capacity should be 3 to 4 times the estimated energy consumption between recharge periods

19 If demand exceeds battery capacity: Add capacity (this may not be possible because of weight and space considerations) Shorten the interval between charging times Reduce demand: Improve the insulation on the icebox Turn off the radar when not needed Turn off cabin lights when not in use Replace lighting with low energy lights Replace high energy fans with low energy fans Get rid of unnecessary electrical devices (e.g. toilets) Limit microwave use to times when the engine is running On a sailboat, use a wind vane in place of an autopilot Design for something less than the worst case and accept some battery damage

20 Charging batteries: On the surface of things, the charge rate we need is: Energy use Available charging time For example: Energy use = 226 amp-hours Available charging time = 1 ½ hours Charge rate = 226/1.5 = 151 amps However, we run up against the limited charge acceptance rate of batteries:

21 Charge Rate versus State of Charge ('typical' voltage regulator setting) Charge rate in amps (100 Ah battery) Charge rate 50% 60% 70% 80% 90% 100% Battery state of charge as % of full charge

22 Charging rules of thumb : There is little point in having a charging output (in amps) with conventional batteries much above 25% to 50% of the total amp-hour capacity of the batteries being charged (AGM, and lithium-ion up to 100%). If charging times are not restricted, the preferred rate of charge for battery longevity is 10% to 15% of battery capacity

23 The effect of raising voltage regulator settings Battery Charge Acceptance Rate (CAR) versus Charging Voltage Charge rate in amps (100 Ah battery) Charge rate at 13.6 volts Charge rate at 14.4 volts Battery state of charge as a % of full charge

24 Multi-step regulators: Courtesy BatteryTender

25 Precise control: Multi-step regulators can cut charging times almost in half This pushes batteries to their limits Precise monitoring and control is essential

26 Putting the pieces together: We have: Sized the battery bank Sized the alternator and other charging devices Determined the need for a multi-step regulator We need to put the pieces together in a manner that: Optimizes system performance Guarantees we can always start the engine

27 Single alternator installation: Install a high output alternator and smart regulator Maintain an isolated cranking battery Concentrate all other batteries in the house bank Feed the alternator output to the house bank Use a paralleling relay to charge the cranking battery Blue Seas has single switch that does this

28 Latching solenoid with manual override

29 A better approach (two alternators): The standard alternator charges the cranking battery he high output alternator with smart regulator charges the house bank There is built-in redundancy Either alternator can be used on all batteries, or both alternators on the house bank The system is conceptually simple and easy to manage

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31 PbA full charge and conditioning cycles: The overarching goal is to never run an engine for battery charging at low loads Piggyback battery full charge cycles onto extended propulsion runs Opportunistic use of solar, wind, & regeneration (hybrid sailboats) when at sea (may require batteries to be isolated) Fuel cells are well suited to this application low power for extended periods of time Use shorepower when at a dock Better yet, use batteries that tolerate psoc

32 In an ideal world we end up with something like this :

33 Rules of Thumb ( conventional batteries): Differentiate cranking and cycling applications and buy the appropriate batteries Size a dedicated cranking battery according to the necessary CCA rating Size the house bank to have a capacity 3 to 4 times the maximum likely amp-hour drain Put all the house batteries in a single large bank Single alternator installation: replace the existing alternator with one that has a hot-rated output, at normal operating speeds, of 25% to 50% of battery capacity (up to 100% for AGM and lithium) Dual alternator: wire the existing alternator to the cranking battery and add another as above The optimum system has two alternators independently charging an isolated cranking battery and a single large house bank, 2017

34 Modifying the mid-capacity rule: new batteries and generating devices

35 Batteries with high charge acceptance rates (CAR): AGM varieties Lifeline Thin plate pure lead (TPPL) Lithium-ion If an engine is run solely for battery charging, the battery CAR is one of two key factors in reducing engine run times and energy costs

36 Batteries that are immune to sulfation: AGM types Carbon dust Carbon plate negatives Lithium-ion If an engine is run solely for battery charging, a high CAR to high states of charge, OR immunity to sulfation, is the other key factor in reducing engine run times and energy costs

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38 Emerging motor/generator technology: Hairpin stator windings raise peak alternator efficiency as high as 70+%; outputs to 200A Conventional brushless PM machines raise peak alternator efficiency as high as 80% PMDC machines with 3-phase VSDs operate as motor/generators (MGU) with 90+% efficiency over broad operating range; outputs to 300A Coming soon: outputs up to 8 kw (= 12v)

39 Steyr graph What if we could add a 10 kw electric load to the propulsion load? 1. The propulsion load is met in a more efficient part of the fuel map 2. The house power needs are met in an efficient part of the fuel map 3. Sophisticated energy management is needed Propulsion load (propeller curve) Courtesy Steyr Motors & Nigel Calder

40 Revised rules of thumb for high CAR batteries: Size batteries based on discharges at each cycle of up to 80% of rated capacity; lithium recharges to 90%; TPPL & carbon-foam depends on available charging time Charging devices should be sized for continuous duty at up to 100% of rated battery capacity; In general, the greater the charging capability the less the engine run hours and the more efficient the system

41 The keys to the energy kingdom: Reduce demand (LEDs, etc.) Optimize the use of shorepower Optimize the use of solar and wind Design the system such that an engine is only run if it can be loaded close to its peak efficiency Modern electric machines, inverters, batteries and energy management devices are an enabling technology for all of the above We are on the cusp of a generational shift in how we create and manage energy on boats

42 A universal shorepower, inverter-based boat:

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