Mariner 36 in Falmouth in November 2019

Solar Panel Selection

Solar Panel Selection

Solar panels were purchased in 2020 but have yet to be mounted. In retrospect it might have been better to wait for solar panel prices to continue to drop. The downside of waiting is that panels with Vmpp of about 58V are now nearly impossible to find and are generally the panels purchased in 2020, still listed on some retailer pages as out of stock and unavailable.

Solar panels considered

At the time of purchase the primary contenders were:

  1. REC Solar 315 Watt N-Peak Monocrystalline Solar Panel is a nominal 315 W panel delivering 18.9 W/sqft. This panel is 65.9" x 39.25" x 1.1" and weighs 40 lbs. It is rated at 315 W, with 33.9 V and 9.31 A at MPP. It costs $195. This panel is nominal 36V and so under voltage for this application and would need two in series.

  2. Panasonic VBHN330SA17 330 Watt Mono Solar Panel is a nominal 330 W panel delivering 17.8 W/sqft. This panel is 62.6" x 41.5" x 1.57" and weighs 41 lbs. It is rated at 330 W, with 58.0 V and 5.70 A at MPP. It costs $368.

  3. The newer Panasonic HIT High Efficiency Solar Panels at 335W and 340W are also nominal 58V. These sell for $320 and $338. Both are 62.6" x 41.5" x 1.6" and weigh 42 lbs.

Near the time of purchase the Panasonic 300W panels were older technology, 310-315W provided the lowest cost per power, 330W incured a big jump in price. Panels up to 360-400W were available but at very high cost. Prices continued to fall and the 330W and 340W panels became among the price leaders and commanded the bulk of the market. Two 340W panels were purchased. This should provide 680W or 2.7 to 3.4 kWh of power per day.

The Panasonic HIT panels or Panasonic HIT+ panels were the best choice. The Panasonic panels are 96 cell, nominal 58V panels. Most panels are about nominal 32-36V are require two in series. Panels in series on opposites sides of the mast will have severe shading problems since one or the other is likely to be shaded. This led to the choice of Panasonic HIT+ 340W panels in 2020.

Other options considered

The Rec Solar panel provided 15W less but at just over half the cost. Since these were nominal 36V two in parallel would need to be installed on each side of the boom.

Most panels are about 66x44 inches. With 11’2" beam, two panels can easily be fit forward of the mizzen mast, on either side of the center line with a wide gap for the main boom. To make this feasible panels with Vmpp of about 58V would be needed.

Another possibility was to mount two nominal 36V panels on each side of the boom with the long side athwartship and tilted at an angle of 20° to each side. This would require about 5’2" width per panel, leaving a gap of about 11" between panels with no overhang beyond the beam of the boat. This gap would make the masthead visible but would be narrower than the cockpit sole. The 20° tilt would reduce headroom when sitting in the cockpit.

Using four lower cost nominal 36V panels would not cost much more than two nominal 58V panels. Bringing the panels closer to the centerline would increase shading problems. The larger area will also add a lot of windage. The benefit is over 1200W of total solar panel capacity, even if shading may cut that in half. There also needs to be 80" (6’8") between the mizzen mast and aft of the main mast to not interfere with sheeting (the traveller or aft or the traveller). The option of using 4 panels between the mizzen mast and traveller was considered but not chosen.

Panels aft of the mizzen mast

A option is to put solar panels aft of the mizzen mast. This would be a difficult install and also would require the use of pairs of smaller panels in series. This option will be considered if solar capacity proves inadequate or marginal. The rigging of the mizzen sail and the mizzen mast standing rigging would be affected, therefore this topic is considered in the Rigging Improvements web page. Since smaller panels not generally used for home solar would be used the price per watt of the panels aft of the mizzen mast would be high. At this time (2025) some panels in the 120W range (pair on each side yielding 240W per side) would fit but at a high cost per watt.