Watt Wizard Solar Monitor
The US Federal Government continues to offer a solar energy tax credit, applicable to your primary and second homes, i.e. your boat! As long as there is a head and galley onboard and it is docked in the United States, your vessel qualifies.
This federal tax credit, in place since 2005 (known as the Energy Policy Act of 2005) has been extended yet again to its current expiration through 2023 for non-commercial installations. Best grab it while you still can!
SunPower® back-contact solar cells are currently the highest efficiency cells available for use in everyday applications at 22%+ rated efficiency. But they can be expensive and difficult to purchase. Genuine high-grade SunPower® cells are only sold to prestigous manufacturers in a few select markets, and significant quantities, a minimum 10,000 cells at a time, must be purchased by the manufacturer to ensure a workable price for their customers.
It has recently come to light that some back-contact cells made by SunPower® have found their way on to secondary markets and into panels originating primarily in China. Rejected by SunPower®when they failed their rigoroustesting, these faulty cells cannot carry the prestigious SunPower® name due to their substandard quality. Unfortunatley, some promotional material we’ve seen brazenly disregards this fact.
Be wary of any solar panel with back-contact cells that does not explicitly make reference to the cells as being genuine, high-grade SunPower® cells.
While the claim may be that this type of panel has superior shade resistance, the results can be very different.
FACT: The smaller the cell size, the less shading it requires to be 100% shaded. The same amount of shade that completely covers a small cell might only cover ¼ of a larger cell. Larger cells are better for shade resistance.
FACT: If just one cell is 100% hard shaded, the output from that series string of cells will be zero, or close to zero.
FACT: Silicon solar cells consume power as well as produce power. If a cell is shaded, it will consume power from the other cells in the series string, resulting in diminished output and heating up of the shaded cell.
FACT: If several series strings of cells are connected in parallel without the installation of blocking diodes, the power from good strings will feed into a shaded string resulting in diminished panel output and the chance of cells burning.
FACT: Blocking diodes prevent back-feeding in parallel circuits, but reduce voltage output by 0.7v.
FACT: By-Pass diodes prevent cell burning ("Hot-spots") and do not consume any power or diminish panel output.
FACT: The more cells and electrical connections there are on a panel, the more output-reducing series and shunt resistance the panel will exhibit, and the more chance of a connection failure, particularly if the panel is flexed.
For best results, look for a panel with large, high efficiency cells, in one series string, with by-pass diodes protecting any string of 50w or greater.
Blocking diodes must be installed on circuits or panels connected in parallel.
An essential component in the installation of solar panels on your vessel is a solar charge controller or regulator. This will regulate the voltage and current coming from your solar panels going to your battery. Most solar panels are 16-25 volts, so if there is no voltage regulation the batteries will be damaged from overcharging. Bear in mind that a fully charged 12v battery is around 12.7 volts at rest, but needs around 14.2 to 14.8 volts under charge. A solar panel has to put out at least that much voltage to be of any benefit, but if the panel voltage is not controlled and reduced it will cause serious battery damage.
Another point to keep in mind: solar panels provide power best when cool, under a clear sky, and in full sun; in other words in perfect conditions. But one can't count on that type of weather day after day, so solar panels have to be built to provide that extra voltage for when the sun is low in the sky, there is cloud cover, high temperatures, or heavy haze to ensure your solar output is not compromised. The truth is a 100 watt panel rated at per industry Standard Test Condition (STC) of 77oF and 1Kw/sq m irradiance will put out less watts when its surface temperature is 100oF degrees and when only 800 w/sq m irradiance is available, i.e. when it is in non-standard conditions.
So this is where the right solar charge controller can help. There are basically two types – PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking).
Did 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
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?
When a manufacturer states their solar panel's power ratings, one must bear in mind that this is only a nominal reading. Unless power tolerance data is shown in the specifications, there is likely to be quite a range of possible power outputs.
Several of the solar panels we offer are made with genuine SunPower® cells which are only sold by SunPower®, directly to known manufacturers, who have passed their scrupulous inspection. And like many manufacturers, there are different grades of SunPower® cells - the higher the grade, the higher the price to the manufacturer, however the better the output. Solara and Solbian use only the geniune, high grade cells themselves on their SunPower® solar panels.
When looking at solar panels, ask to see the specification for the panels themselves. For example, Solara's Ultra glass panels show a power tolerance of -0%/+4.99%, so they are guaranteed never to be less than the nominal rating.
The good news for those with flexible solar panels with a polymer top coating is that maintenance is minimal.
1. Keep the modules clean by washing them with fresh water to remove salt water deposits, bird droppings, dust particles or other debris that can lessen the chances of the sun's rays from reaching your solar cells.
The surface of the panels may be cleaned using neutral soap and water, wiping carefully and without using abrasive material. Denatured alcohol (methylated spirit) can be used to remove grease, etc.
When panel is clean and dry, apply a coating of a plastic protectorate such as "Plexus" or Novus Plastic Cleaner #1- available at your marine chandlery or online.
If contaminants build up or oxidation occurs over time, it may be necessary to polish the panel. The recommended polish is either ReJex or Novus brand polish, #2 (Fine scratch remover). It is recommended that you hand polish the panels, as a power polisher could burn the surface with too much friction. Follow the instructions on the product label.
2. Check the structural integrity of the installation and the electrical connections periodically.
3. Check the efficiency of the system using the monitoring functions in the charge regulators (LEDs or displays).
If you see me at a trade show and notice that the company shirt I’m wearing does not fit too well around the collar, it is probably because it was bought at low cost from an outlet store by the embroiderer. The label suggests that this shirt is from a highly respected manufacturer and is of high quality, which is all true up to a point, but somehow the buttons and button-holes were mis-aligned during assembly, and so this item was sold off as a “second” or reject item in the manufacturer's outlet store.
Well, guess what? Somewhere out there is an outlet store for low grade, off-spec, SunPower® solar cells.
During manufacture, after solar cells have been tested electrically they are sorted into different “Bins” dependent on how they performed. Some will be over achievers and be put aside for research purposes, while others will simply fail miserably and be destroyed. Those remaining are the Good, the Bad, and the Ugly cells; Good being “Prime”, Bad being “Off-Spec”, while the Ugly cells will have visual or cosmetic defects.
The Prime cells are further graded into High, Premium, and Ultra performance categories, while the Off-Spec cells are
Standard solar panels produce much higher voltages than are safe to feed directly to a battery, so a solar controller or regulator must be connected between them.
Two types of controllers are available; PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking).
PWM Controllers - When charging, these controllers feed the power from the panel straight through to the battery until
the battery voltage reaches a predetermined Acceptance level. It will then keep the voltage at that level by pulsing
the panel voltage on and off to keep the battery voltage constant.
During the Bulk stage of charging, the amperage delivered to the battery is slightly less than the amps from the panel due to losses in the electronics.
MPPT Controllers - These controllers take the best mix of amps and volts from the panel to give the maximum power.
They then track this Maximum Power Point as conditions change to ensure the highest power is extracted from the panel
at all times.
The DC panel output is then inverted into very high frequency AC and then converted back down to DC to feed to the battery. The result of that inversion/conversion process is that more amps can be delivered to the battery than were produced from the panel, resulting in reduced charging times.
That is a significant advantage over PWM controllers, and more than justifies the higher cost of the MPPT models.
Typical marine solar panels are comprised of a number of silicon cells (normally 32+) connected together electrically in a series string. Individual silicon cells produce only around 0.6v to 0.7v, and so enough of them have to be connected together in series to produce a voltage high enough to be able to charge a 12v battery.
A Charge Controller must be connected between the panel and the battery to reduce the panel output to a safe charging voltage. Some panels have less than the normal number of cells and produce less voltage than is required to charge a 12v battery, and these will require either a special boost controller, or for a number of them to be connected in series to produce a higher voltage.
The published wattage rating of solar panels is determined by testing with a machine that flashes a light with an intensity of 1,000 watts per square meter on to the panel as if the sun were directly overhead. This flash test, performed under standard temperature and air quality conditions, gives a theoretical maximum power output that might be possible from that panel under the most ideal conditions.
This may sound like a cheap marketing ploy, but in fact is done from a safety aspect, as the cable and safety devices (fuses, breakers, etc.) must be sized in accordance with the maximum power that the panel(s) might produce, especially in multiple panel arrays. Typically, a panel will produce nowhere near its rated output in normal use, except maybe occasionally and then only very briefly. Considering the above, and the multitude of ever-changing conditions in a real deployment, it is not practical to simply use the wattage rating of a solar panel as an indicator of what power output to expect over the course of a complete solar day; i.e. from sun-up to sun-down. So how can we estimate what size panels, and how many, we might need to satisfy our daily amp/hour consumption?
First it is necessary to differentiate between the three most common types of silicon cells in general use.
An increasingly popular question we hear at Boat Shows is "What size solar panel do I need to run the refrigeration on my boat?" Of course, this begs the question "What is your refrigeration's current draw?" which in itself may not have a set answer.
The current consumption of any refrigeration system is meaningless unless all the conditions are specified, i.e. box temperature, ambient temperature, water temperature, compressor speed, voltage, etc. The manufacturer's figures are simply average numbers; some manufacturers, like Frigoboat, attempt to give a true average figure, while others use their figures more as a marketing tool.
Making use of variable compressor speed, as Frigoboat does with the Merlin II and Guardian speed controls, and others do with the Danfoss/Secop AEO control module, brings even higher efficiency and lower overall power consumption in air- and keel-cooled systems, but is counter-productive in a pumped-water system. This is because the pump adds 25% to 35% extra current draw, and so it is best to run the compressor at full speed and get the job done as quickly as possible. The most efficient system is one using the Keel Cooler; no pump, no fan, and variable compressor speed can be used to gain even higher efficiency.
Daily consumption is measured in amp/hours per day, and you can get an idea of what to expect by using a watts meter, like Watts Up, on your refrigerator leads. These meters can tell you how many amp/hours per day a device is using, and it's best to use it over several days to get a daily average. The running consumption will vary dependent on conditions, as will the on/off cycle time, so you will need to be able to come up with an average daily amp/hr draw.
As a general rule of thumb, a solar panel with SunPower® cells will give approximately 1/3 of its rated wattage as a daily yield in amp/hrs. A panel with regular monocrystalline cells will produce about 1/4 of its wattage as daily amp/hrs, and a polycrystalline panel produces around 1/5 of its wattage rating in amp/hrs per day.
Let's take an example:
Which type of Solar Panel is best for Marine Installations?
Monocrystalline; Polycrystalline; SunPower®
3 - 4 - 5 Remember these numbers. These are the factors by which you need to divide the rated wattage of a panel to give an estimate of the amp/hr daily yield, at 12v, that a panel might produce dependent on the type of cell.
Example: If we have one of each type of panel, all rated at 100 watts, then the one with SunPower® cells will produce somewhere in the region of 33 amp/hrs per day; the one with regular mono cells will produce around 25 amp/hrs a day; and the panel with poly cells will produce 20 amp/hrs or so a day. (Note: This is assuming a good solar day, using a MPPT controller, and with a full time load). So why the difference?
There seems to be many misconceptions regarding solar panels, particularly concerning marine installations on vessels. I’m thinking that maybe it’s because we all see solar panels on houses and assume that what applies to roof-top installations also applies to boats. Wrong!
Here’s some solar facts. Typical solar panels with silicon cells will:
• Produce electrical power whenever they are exposed to light, and this is proportional. Small amount of light - small power output.
• Produce full voltage even in very low light, often even indoors, but only if they are disconnected and not being asked to produce any power. Potential voltage output depends mainly on the number of cells. Each cell typically produces around 0.6 to 0.7 volts.
• Produce full current output only if there is a big enough load, the sunlight is good enough, and shading is non-existent. Potential current output depends on the size and type of cells.
In general; the quantity of cells determines voltage; the quality of cells determines amperage.
Now, what we are after in a boat solar application is to grab whatever power we can whenever there is available sunlight, and that means from dawn right through to dusk, not just at noontime. I often hear customers say that there is absolutely no shading at the back of their sailboat, but then when it is suggested that maybe in early to mid morning or mid to late afternoon, the presence of a humongous mast and associated rigging might shade a stern-mounted panel, they will humbly agree. From that sort of response one could deduce that many boaters are under the assumption that solar panels will really only work for a couple of hours each side of noon. Not so Horatio.
When you want solar on your boat... You Want Solar On Your Boat! Now, where you put it depends on what real estate you have available that is relatively free of potential shading and yet still gives you room to move around.
Those of you with a sail boat need to be aware of the shadows cast by your mast, boom, and rigging. If you have a power boat, be aware of the shadows cast by your radar, arch, antennas, water toys, helicopter, etc.
So, let’s look at what others have done.
1. Dingy davits are popular locations for either glass panels or lighter weight semi-flexible panels. The davits themselves should be specifically designed and fabricated to carry the extra weight. Notice the clever person who put lightweight panels in-line with the davits to allow easy access to the dingy and swim ladder.
A while ago I debunked some common misconceptions about solar panels in another blog here, but it seems I missed one that has come to light several times recently, i.e. the myth that to have proper, serious, useable solar power on a boat one must use residential panels, as marine solar panels are just itsy-bitsy wimpy battery top-up trickle-chargers.
Nothing could be further from the truth!
There's a lot of talk of trade and trade agreements in the run-up to the election, but I've heard nothing of how the substantial anti-dumping and anti-competition tariffs applied to Asian solar products are protecting US interests.
Originally applied to just solar cells, these tariffs were expanded last year to also include complete solar panels made in China and Taiwan, and add a whopping 250% or so of duty to the imported price of all but a very few manufacturers of Chinese and Taiwanese panels.
The results of these tariffs are already being seen in the semi-flexible panels, popular in marine applications. Many of these low-cost panels suddenly shot up in price, and several outlets stopped offering them altogether, but the tariffs are not the only reason .....