Generator selection#

Sunwake SW-15 · SW-GEN Rev 1 · August 2026

This document selects two variable-speed DC passage generators and defines the terms for their purchase. It applies the requirements in Design specification SW-500 to the 352 V bus in SW-300, reviews the marine products available at that voltage, and turns the viable options into an RFQ package. It also uses a measured basis for fuel-to-bus conversion and recomputes range for 600 L of HVO.

1. Requirements#

The 20 kW rating follows the duty analysis in Power and energy. One set at its 16 kW efficient point holds 8.15 kt; at its 20 kW rating it holds 8.53 kt. Both sets at 16 kW each hold 9.39 kt, and both at rating hold 9.81 kt. The design passage speed of 8–8.5 kt therefore uses one generator in its quiet, efficient region, leaving the second available as redundancy. At 9 kt, the 25.6 kW bus demand runs both sets at about 64 % of rating. Ten knots requires 43.5 kW, more than the pair can supply, so it needs battery assistance and is not a sustainable generator speed.

The requirement is therefore for two modest machines that normally run at part load. If one fails on passage, speed falls by about 1.2 kt but the passage can continue.

2. Recommendation#

Primary: 2 × Fischer Panda AGT 20-VS PMS (art. 0034157). This unit matches the SW-500 requirement and is the only packaged, capsule-enclosed 20 kW / 300–500 V DC marine generator found in the current catalogue review. The larger AGT 45-VS is used as the range extender in Torqeedo's Deep Blue Hybrid with 348–352 V packs, providing a production reference for the product family at Sunwake's voltage. The published sound claim of 55 dB(A) at 7 m equals the SW-500 limit before installation treatment. At the 16 kW test point the set runs below rated rpm, which may provide the required margin; see §4. Two units weigh 490 kg with capsules, leaving about 150 kg in the 640 kg group budget for exhaust systems and added lining.

Challenger: EPTechnologies 12–20 kW Kubota-based DC generator, configured to order anywhere from 48–800 V DC. At under 110 kg per unit, the pair would save 270 kg, equivalent to roughly 0.04 kt at solar noon or additional margin for the 192 kWh battery growth path. A Sunreef 50 serial-hybrid installation provides a reference. The gaps are significant: there are no published sound data beyond a description of the insulation, no published pricing, and no verified wet-exhaust, HVO or US-support details. Include it in the RFQ and require a witnessed sound demonstration before considering selection.

Engineering fallback: Kubota or Yanmar engine plus a Danfoss Editron EM-PMI240-T180 PM machine and an EC-C1200-450 active front end. This is a custom system using marine-class-approved power electronics (ABS, BV, DNV, LR, RINA, CCS; dual CAN J1939) and an 85 kg machine rated to 50 kW. No packaged small-craft product or suitable small-craft integrator was identified. It is an [ENG] project requiring vendor sign-off on the 308–394 V link and should be pursued only if Fischer Panda lead time or pricing is unacceptable.

Rejected options:

• 48 V generator families. A 48 V product cannot feed a 352 V bus. Serving it would require stacked DC-DC conversion — no off-the-shelf marine 20 kW converter exists, so the route is banks of 5.5 kW modules (Epic Power class) per hull, adding cost, losses and failure modes to reach a bus the AGT 20-VS feeds natively. Every 48 V machine on the market is eliminated on that ground alone, including the otherwise attractive quiet capsules.
• WhisperPower. The DC Genverter line tops out at 12 kW / 48 V, with no HV product below superyacht scale.
• Praxis Automation GreenGenerator. Excellent DC-bus gensets; the smallest is 140 kW.
• Volvo Penta and Yanmar variable-speed. Volvo has nothing below roughly 200 kW; Yanmar has nothing at high voltage (the YF12e harvest unit is 48 V and ≤ 10.5 kW).
• Hydrogen fuel cells. The Genevos HPM-40 (35 kW rated, 230–450 V DC, 190 kg, 54 % efficient) fits the bus window and is the quietest machine reviewed. It is rejected because hydrogen is not available at Maine or ICW fuel docks. Revisit only if marine hydrogen supply becomes practical.

3. Candidate comparison (verified August 2026)#

Two details require changes to SW-500. First, the AGT 20-VS speed band of 1,200–3,000 rpm is wider than the specified 1,500–2,600 rpm and allows quieter light-load running. Revise SW-500 to match the vendor range. Second, both Panda units are seawater-cooled through a heat exchanger; keel cooling is not catalogued for the VS line. The baseline therefore becomes heat-exchanger cooling with a dedicated scoop and strainer, with the raw-water circuit included in the noise design. EPTechnologies describes its cooling as customizable, so the RFQ should ask whether keel cooling is available.

4. Noise: from datasheet claim to acceptance test#

The datasheet figure of 55 dB(A) at 7 m equals the SW-500 limit with no margin. The claim is at rated load in free field, while the acceptance test is at 16 kW, or 80 % of rating, where a variable-speed set runs more slowly. Three measures provide the available margin.

1. Operating point. Program the energy management dispatch so normal single-set running sits at 14–16 kW, reserving the 20 kW rating for the both-sets passage case. SW-320 also prevents routine nighttime generator use at anchor by delaying automatic start until 15 % SOC.
2. Installation. Meeting the ≤ 50 dB(A) cabin limit depends on the installation. SW-500 specifies a double-elastic raft inside a lined enclosure (50 mm class-A foam plus mass barrier), underwater exhaust with a gas/water separator and above-waterline idle relief, flexible sections in every service, and no rigid bridges. Add a full-load intake silencer, stiffened and damped adjacent panels, through-hulls and strainers away from berths, and acoustic lagging on the wet-exhaust run.
3. Structure-borne path discipline. The machinery bays are aft and the sleeping cabins are forward of them in the same hulls, so the raft-to-bearer-to-hull double isolation and the mass of the bearers matter more than another decibel of airborne capsule rating. Specify measured vibration limits at the bearers — mm/s at 1× and at firing frequency — in the installation contract, not only dB(A) in the cabin.

Contract language should require acceptance per SW-800 (≤ 55 dB(A) at 7 m abeam, ≤ 50 in any cabin, ≤ 57 in the cockpit, one set at 16 kW) and a witnessed factory or reference-boat sound demonstration at the 16 kW point before the order is placed. Fischer Panda have demonstration boats and Torqeedo-equipped references. EPTechnologies must produce one to stay in the running.

5. Fuel and range#

Fuel-to-bus conversion directly affects tankage and derating decisions. Published small-diesel and PM-alternator chains support 2.9–3.2 kWh of DC at the bus per litre. HVO carries roughly 9.6 kWh/L thermal, and the hardware delivers 30–33 % engine-to-bus efficiency near its efficient operating point. Values near 3.7 kWh/L omit losses in the alternator or rectifier.

Sunwake carries 600 L of HVO in two integral keel tanks at the LCG, with crossfeed. At 2.9–3.2 kWh/L that is 1,740–1,920 kWh to the bus per tankful. Against her own power curve:

The 600 nm passage requirement is met with useful reserve at 8–8.5 kt, where one generator carries the load, and with little reserve at 9 kt, where both sets run. The operating plan is therefore 8–8.5 kt for passages, with 9–10 kt used on shorter legs when needed. The corrected conversion does not require a design change, but it should govern tankage decisions. Capacity could grow toward 800 L at modest cost and an additional 160–200 kg if experience calls for longer legs.

Ask each vendor for the measured fuel map — g/kWh against load — at RFQ. Fischer Panda publish none, so make it a quotation deliverable rather than an assumption.

6. Integration items#

These are the [ENG] items that must be settled with Electrical architecture and insurability and the SW-320 monitoring scheme before the order is signed.

• Parallel operation. SW-300 calls for current-source droop-share between the two sets across the cross-tied islands. Fischer Panda's fpControl regulates to a voltage setpoint window; confirm at RFQ whether two AGT 20-VS units coordinate by droop natively or require EMS-mediated setpoints. Deep Blue Hybrid runs multi-source buses near 360 V, so the capability exists somewhere in the family — the task is to get it documented for this unit.
• CAN. The 45-VS integrates with Torqeedo's system over a documented DC-generator interface. Require the protocol specification (J1939 preferred, per SW-320) as a quotation deliverable for the 20-VS. Victron document fpControl DC-generator support on VE.Can for the GX platform; verify that it extends to the VS high-voltage series if a Cerbo-class EMS is chosen.
• Start authority. Generator start rules belong to the EMS — below 25 % SOC underway, below 15 % at anchor, solar first, quiet hours enforced. Configure the genset's autostart to follow EMS commands rather than apply separate rules.
• Heat recovery. A coolant-loop tap feeds the 60 L calorifier per SW-400. Confirm at RFQ that the VS-series heat-exchanger plumbing exposes a takeoff circuit.
• HVIL and isolation. The generators are high-voltage sources and join the per-hull insulation-monitoring zone, HVIL loop and crash-signal contactor scheme in SW-300 and SW-900. The active rectifier must tolerate contactor opening under load, so the RFQ must state its load-dump rating.

7. RFQ package#

Send both hull sets as a single RFQ to Fischer Panda (Paderborn headquarters and the Fort Lauderdale office — note that the US site does not retail the VS line, so route through headquarters or a dealer) and to EPTechnologies (direct, Denmark). Hold Danfoss Editron distributors as the fallback route. Require in each quotation:

1. Price, lead time, and a US East Coast commissioning and service arrangement.
2. Voltage setpoint configuration at 352 V nominal with a 308–394 V window, and charge-profile behaviour against LFP — specifically, who owns the charge curve, the genset or the BMS/EMS.
3. Measured fuel map (g/kWh against load) and sound pressure at the 16 kW reduced-rpm operating point, not only at rating.
4. Parallel and droop-share documentation for two units on cross-tied buses, plus the CAN protocol document.
5. An HVO (EN 15940) warranty statement in writing.
6. Keel-cooling option yes or no; calorifier takeoff circuit; load-dump rating at contactor opening.
7. A witnessed sound demonstration, at the factory or on a reference vessel, at the 16 kW point.
8. Weight with capsule, mounts and recommended exhaust components, to feed the weight ledger against the 640 kg group budget.

Redlines to raise against Design specification when the quotations return: SW-500 candidate line to name the AGT 20-VS PMS as primary, EPTechnologies as challenger and the Editron pairing as engineering fallback; SW-500 speed band to read 1,200–3,000 rpm variable; and SW-500 cooling to record that keel cooling is not catalogued on the VS line, making heat-exchanger cooling with a dedicated scoop and strainer the baseline and the raw-water path a noise item.

Sources#

Verified August 2026.

Fischer Panda Hybrid-VS: Hybrid-VS category · AGT 20-VS PMS (specifications verified directly) · AGT 45-VS PMS · 2023 Hybrid Series brochure (30/35–100 VS) · PVMV-N custom-voltage program · AGT-DC line · AGT-DC 18000-48V datasheet

Torqeedo, field proof at 348–352 V: Deep Blue Hybrid

EPTechnologies: Generators (specifications verified directly) · Product overview and Sunreef 50 reference · METSTRADE Mini DC generator listing

Danfoss Editron route: EM-PMI240-T180-2200 datasheet · EC-C1200-450 AFE datasheet (class approvals, CAN)

Ruled out: Praxis DCG, ≥ 140 kW · WhisperPower lineup, ≤ 12 kW DC · WhisperPower Piccolo GV 3 · Powerflow Marine 48 V genset · Volvo Penta variable-speed, D8 and above · Yanmar YF12e, 48 V · Epic Power DC-DC modules · Genevos HPM-40 · EODev REXH2

Energy management reference: Victron Cerbo GX fpControl support

Sound figures are manufacturer free-field claims with the enclosure fitted, at the stated distances; they are not directly comparable across brands or conditions. Prices given as "quote" mean the manufacturer publishes none. Items marked [ENG] or "RFQ" require vendor or engineer confirmation before contract.