Solar

Aurinco is insinuating that some solar panel manufacturers are trying to mislead the public by publishing cell efficiency figures rather than panel efficiencies. They are also suggesting that some manufacturers are embellishing results using tactics learned from the automaker VW.

Normally this sort of rhetoric would be quickly dismissed as being disingenuous and unprofessional, but it does merit some analysis.
There are several ways to measure solar panel efficiency. Some are shown below, all at Standard Test Conditions (STC)

Single Cell Efficiency - Solara has always stated cell efficiencies, not panel efficiencies, which can be very misleading (see below).

Overall Panel Efficiency - This takes into account the overall panel dimensions, and so can vary wildly between one panel manufacturer and another dependent on how they construct their panels. If a manufacturer is willing to risk edge damage and water intrusion by fabricating a panel with very small edge margins, then it will inevitably look to be more efficient than a similar panel that has wider, and subsequently much safer, edge margins and overlaps.

True Panel Efficiency - This is calculated from the actual total cell surface area, ignoring space between cells and margins/borders, and is by far the more reliable gauge of panel efficiency.

Panel Single Cell
Efficiency
Overall Panel
Efficiency
True Panel
Efficiency
Aurinco Compact
147ST
 unknown  16.6%  20.0%
Solara Power M
140 
22.5%   17.2%  21.3%

Cells - Aurinco use standard monocrystalline cells with bus lines and collector fingers on the surface that reduce effective surface area and actually create their own shadows at low light angles.

Solara Power M panels use genuine high-grade back-contact SunPower® cells that give superior performance in low irradiance, low light angle, and high cell temperature conditions.

solar-efficiency-bargraph-cost
We often get asked about the latest developments in solar technology, and when will they be available, if suitable, for boat applications. I am by no means a solar expert, geek would be more appropriate, but I do keep my ear to the ground and try to keep up with the latest developments.

The people at the National Renewable Energy Laboratory (NREL) make this a lot easier by publishing their chart (below) of research cell efficiencies for various solar technologies. This shows the state of play of the very best of the best cells available of each type of solar, measured by their efficiency, i.e. how much of the available solar irradiance is converted into electrical power. Here's a quick synopsis of the chart.

Cracked-solar-cellDid you know that there is an official measurement for a hairs breadth? Well, according to my conversion tables:

one hairs breadth = 100 microns (micrometers, millionths of a meter)

So the thickness of a regular silicon solar cell, at around 200 microns, or 2 hairs breadths, is pretty darn thin! And when you consider that the SunPower® back-contact cells that are used by Solara and Solbian are even thinner, at about 1.5 hairs breadth, and that these cells are essentially glass in nature, you will no doubt appreciate that they will need careful handling.

The SunPower® cells used in Solbian flexible panels are high grade cells that are purchased guaranteed free from physical defects, but careless handling in storage, shipping or on site, together with improper installation, can initiate cracks in the cells which will be invisible to the naked eye.

In the majority of applications these cracks will be comparatively harmless and may not cause any problems other than a small loss of power, but

solar-wind-640x434
Here at Coastal Climate Control, we talk to a lot of boat owners, at shows and in the course of daily business, and in general most of the people we talk to who have wind generators seem to be less than ecstatic about their performance.

We commonly hear gripes that what these device's specifications promise on paper seldom seem to materialize in real life application. And then the cost, complexity, and effort of installing wind generators apparently put a lot of people off, not to mention the unease of having sharp-edged blades whirling away within a daggers-throw of one's head!

Some wind generator owners report that their systems perform well on passage, when the boat is beating into the wind, although it is well known that gentlemen never go to windward ... but then when the destination is reached and the hook dropped in the sheltered anchorage of an island, the wind generator seems rarely to have the oomph needed to fully charge the battery, at a time when reliable charging is most needed.

So, have wind generators had their day?

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