Marine solar panels – having improved tremendously in efficiency and affordability over the past few years – are becoming a popular option to keep lights and appliances running on board.
Solar panels replenish the DC power in your boat’s battery system. A small panel or two can maintain or trickle charge your batteries while you’re unplugged from shore power. Add a couple more panels, and you’ll be able to produce enough energy to power appliances.
For sailboats that go on long passages, marine solar power kits can eliminate the need for running the propulsion engine to keep the batteries charged in order to replace energy that’s been consumed.
Benefits of Adding Solar Panels to Your Boat and Turning Photons into Electrons
Solar panels are perfect for keeping batteries topped off while you’re disconnected from shore power.
This means that while you’re out fishing or anchored for the evening, you can run your electronics (TV, laptop, cell phone charger, stereo, cabin lights, navigation lights, bilge pump, GPS, etc.), and still have enough power to start your engine and get home.
You can also safely generate electricity and charge your batteries with solar power while you’re away from your boat. This isn’t possible with generators, which require manual operation and monitoring. With solar panels, you can produce usable electricity during the day and then use it for weekend boating adventures.
One of the most attractive benefits of marine solar power systems is the money and time you’ll be saving. For a small upfront investment, you’ll be generating free electricity for your boat for as long as your panels last. Alternatives to electrifying your boat, like marine generators, require purchasing fuel on an ongoing basis which is both time-consuming and a continuing cost.
Another benefit of marine solar panel systems is the quietness of operation. For those going out on the open water to experience nature, running a generator can be a noisy disturbance. By powering your boat with solar, you can enjoy peace and quiet without losing power.
How Solar Panels Bring Electricity Onboard
(1) to charge the batteries
(2) to provide 120-volt AC power for household appliances
In the charging system (1), the solar panels convert sunlight into electrical current and deliver it to the batteries via a solar charge controller. Similar to a voltage regulator, the charge controller acts as a gatekeeper to protect the batteries from receiving more current than they need as they are being charged.
In the AC power system (2), an inverter converts the 12-volt DC power in the battery into 120 volt AC household power whenever it is turned on, allowing it to power appliances.
A charge controller is an essential component of your marine solar power system. The controller maintains the life of the battery by protecting it from overcharging. When your battery has reached a 100% state of charge, the controller prevents overcharging by limiting the current flowing into the batteries from your solar panels.
How Many Marine Solar Panels Will You Need?
The first step when figuring out how many panels you need is to figure out your boat’s power requirements. Creating an excel or google sheet, or using this sheet, is the best way to organize this.
Add up all the energy used by each device on your boat, such as the fridge, lights, computers, etc. by checking the badge on the appliance to give you the power requirements in watts or amps. You will want to use either all watts or amps when making your computations, and match it to the solar panel’s quoted output. This online calculator can help you convert watts to amps and vice versa for when needed.
Note: Just for your reference, the relationship between power and current is expressed as: Power (W) = Current (A) x System Voltage (V)
Next you want to calculate all of the watt-hours or amp-hours of each device – get the watt or amp output of each device and then multiply it by the hours per day the appliance will be running.
When making estimates, take into account that some appliances will work harder during certain hours – for instance, the fridge will work harder when the sun is out and the temperature rises, or you will use your watermaker more should there be more guests onboard.
You will also need to calculate how much power you can reasonably expect to get from your panels over 24 hours, and ensure that the panels are powerful enough to supply your complete power requirements in the daytime, plus have enough capacity to charge the battery by the amount it has been depleted overnight.
Once you’ve figured out your energy requirements, you should add at least an extra 10% margin for expansion and errors. Underestimate your power needs and you will end up having to run the engine to top off the batteries every so often.
Worse comes to worst, you can always add another panel or two later. Power usage fluctuates, and is hard to predict. After cruising, you should get a better idea. And keep in mind – a bit more is always better than a bit less.
How Much Power Can You Reasonably – and Consistently – Expect to Get from Your Panels?
You may be wondering if you’ll get the quoted wattage from your panel — If the panel is a 100 watt panel, will you really get 100 watts?
Panels are rated by the electrical power produced under certain testing conditions, generally the best possible solar and clarity conditions. But do you ever really get these when out boating?
On the right days, a solar panel will put out its maximum output (when the panel is in the full sun – defined as 1000 watts of energy per square meter) for a set number of “insolation” hours. A good indicator that you are under full sunlight is when there are fairly sharp-edged shadows. In most of the continental US, there is an average of 4 or 5 hours of insolation per day. You can get a good estimate of your region’s insolation hours, here.
Even though the sun may be above the horizon 14 hours a day, any one site may only receive a maximum of six hours of full sun hours per day for the following reasons: 1) the reflection due to a high angle of the sun in relationship to your solar panel, and 2) the amount of the earth’s atmosphere the light is passing through. When the sun is straight overhead the light is passing through the least amount of atmosphere. Early or late in the day, the sunlight is passing through much more of the atmosphere due to its position in the sky.
An example to better illustrate solar panel output related to daily hours of sunlight
When using appliances, they draw power off your battery. Solar panels put this energy back into the battery banks.
For instance, one Go Power Flex-100 panel will put about 5 amps per hour back into your battery bank. So if you are using 20 amps per day, it will take you approximately 4 hours of insolation hitting your panel to fully recharge your batteries.
As to how much power you can expect to get from any individual solar panel per day, let’s say you are using the Go Power 100-watt solar panel that produces 5 amps peak power in a location that has 5 hours of insolation, it can be said that the 100W panel will produce 25 amp hours a day.
Two Go Power Flex-100’s will provide you with 50 amp hours a day… and so on and so forth.
How to Get the Most out of Your Marine Solar Panels
Bear in mind the following tips to maximize the energy your solar panels will produce:
1) Keep your panels as perpendicular to the incoming sun’s rays as possible: All panels will produce more power if they get direct sunlight. Mount your panels as best possible so they can be aimed in the appropriate direction, no matter what the season, course, or latitude.
2) Consider shadows when placing your panels: The output of a panel drops dramatically when under a shadow, even if only 10 percent of the panel is covered. A small shadow can reduce the panel’s output by 50 percent or more. When something as large as a boom, radar scanner, or mast casts its shadow on a panel, your output goes down dramatically.
3) Keep your panels cool: It’s not easy to keep a black surface cool in the sun, but panel output can go down as the temperature rises, so if you can provide some ventilation on the backside of the panel, you may be able to pick up a decent increase in energy production. The colder the panel, the higher the output. For instance, a solar panel’s performance on a clear, cold winter day can be 30 to 40 percent over rated specs!
Marine Solar Panels and Solar Power Kits
We carry Go Power Marine Solar Panels, Chargers, Inverters and Solar Power Kits. Go Power provides cutting-edge, high-grade monocrystalline cell solar panels that give you the most power out of your panels, and industry leading warranties. Engineered to work far better than competition in low light or overcast conditions. You can find Go Powers Marine Solar Power Kits and Panels, here.
Have a good one!