Travel Reference
In-Depth Information
rising and setting sun at our location over the course of a day. PSH neatly boil down our
solar situation to a single number. For example, in January in the Virgin Islands, we have
the sun above the horizon for about eleven hours. As the sun moves across the sky during
these eleven hours, it delivers the same amount of solar energy that a theoretical stationary
sun directly overhead our position would provide in just over five hours - five PSH in this
case. [1]
It is this “sun vertically overhead” scenario that most of us have in mind when we talk
about “how many amps” our solar panels deliver. It is also the scenario assumed in manu-
facturers' output specifications for solar panels. With this in mind, PSH is what we should
be looking at in order to realistically estimate the energy we can reap from our solar pan-
els each day along our cruising itinerary. This can be a bit sobering: if I see my solar pan-
els delivering a charge current of 10A during the height of summer in the Chesapeake Bay
around noon time [2] , I can assume only 5.3 PSH of that output over Christmas in the Vir-
gin Islands. Take off another 20% to 30% for cloud cover [3] and I'm at 4 PSH - on a
sunny day and assuming no obstruction from rigging or shore structures.
Figure 2: PSH as a function of latitude and season
Figure 2 shows daily PSH values over the year across a range of latitudes. If you know
your energy needs over a twenty-four hour period at anchor, you can use the data from
Figure 2 as a starting point for sizing your solar capacity. For example, let's assume a
Search WWH ::




Custom Search