In 2019, the renowned climate activist Greta Thunberg traveled to address the UN Climate Action Summit. She sailed in the Malizia II, which is a yacht powered entirely by hydro (water turbine), solar (panels), and wind (sail).
The voyage on the Malizia II raised the credibility of using renewable energy as the primary power source for boats.
While the combination of technologies used on Malizia II is outside the reach of the average boater, it still raises the question of what technologies are realistically available.
Solar Electric Boats
Solar electric boats are one of the purest forms of renewable power supply. In this form, gas or diesel engines are replaced by electric motors.
The motors receive the electrical current from batteries. In turn, the batteries are recharged by the electrical current produced by a solar panel array.
This can be supplemented with a wind turbine, which can produce power even when the sun isn’t shining. Wind turbines are generally inefficient (compared to solar). For this article, I will concentrate on hybrid solar power.
Hybrid Solar Boats
Like hybrid electric vehicles, hybrid solar boats can be divided into further categories.
- A diesel or gas-powered engine is the most powerful and primary power source.
- An electric drive is the primary power source, and the boat is fully electrically propelled.
- An electric motor (generally on the output shaft) is attached to the engine and can provide sufficient power to move the boat short distances at relatively slow speeds.
In the cases where an electric motor is present, you can harness the sun’s power using solar panels. Understand the benefits of charging boat batteries with solar panels, such as acting as a generator on board appliances and equipment.
🔑 Key Components
Each solar system comprises four basic components.
The solar panels are mounted in a position that is at an optimal angle relative to the sun. 3 main types of solar panels are available.
Monocrystalline Solar Panels
These panels are constructed of silicon wafers placed into rows and columns to make up the panel.
Monocrystalline panels are produced from a single crystal of silicon. This makes them the more efficient technology.
Polycrystalline Solar Panels
Like Monocrystalline panels, these are constructed silicon wafers placed into rows and columns to make up the panel.
The difference is that the polycrystalline solar cells comprise silicon crystal fragments. These are melted together in a mold. This transforms them into ingots. The ingots are cut into smaller wafers used in the assembly process.
Polycrystalline solar panels are inefficient compared to Monocrystalline Solar Panels.
Thin Film Solar Panels
Most thin-film solar panels are made from cadmium telluride (CdTe). They can also be made from Amorphous silicon (a-Si) or Copper Indium Gallium Selenide (CIGS).
The advantage of thin film solar panels is that they can be bent to fit the shape of the underlying mounting surface. This makes them ideal for use on boats with few flat surfaces.
The downside is that thin film panels generally offer under ½ the efficiency and power production of Monocrystalline Solar Panels.
Thin film panels are also known as flexible panels. Compare rigid vs flexible marine solar panels for solar boat applications.
The sun’s energy that reaches the solar panels presents two primary challenges to boat owners.
The quality of the sun’s energy that reaches the solar panels is volatile and varies according to many variables.
1️⃣ The Solar Boat’s Geographical Location
The boat’s latitude is one of the primary factors determining the amount of sun’s energy available.
At the equator, the days are longer and less affected by the seasons.
The Earth tilts at an angle of approximately 23.5 degrees relative to the sun. This results in the sun being high in the northern hemisphere in May, June, and July and low in November, December, and January.
The lower the sun’s angle, the shorter the days and cooler the temperatures.
As the boat moves North or South, the vagaries of the season become more apparent. This has two impacts on the solar system.
- The daylight hours are shortened in winter – the opposite is true in Summer.
- The solar panel’s angle to the sun is lower as the boat moves North or South, and the energy it can capture is reduced.
2️⃣ The Weather Affects Solar Panel Efficiency
Cloud cover, fog, rain, and storms reduce the amount of solar energy reaching the panels.
3️⃣ The Time Of Day Affects Solar Panel Efficiency
The peak solar hours (when the maximum solar energy is produced) range from 2 – 6 hours daily.
Outside of this, the amount of energy produced by solar panels is reduced (or even stopped.)
4️⃣ The Direction The Boat Is Travelling Affects Solar Panel Efficiency
As the boat changes direction, the orientation of the panels changes.
A Maximum Power Point Tracker (MMPT) equipped charge controller solves the problem of solar volatility.
The device constantly controls and stabilizes the current produced by the solar panels. This ensures that the batteries receive the optimal charge rate.
The batteries are the weakest and most expensive components of a solar system.
The problems with batteries are listed below.
- They are very heavy, which ultimately reduces the boat’s range.
- They have a finite lifespan which ranges from 2 – 10 years, dependent on the battery technology.
- They are the single most expensive component in the solar system.
Despite these weaknesses, the batteries are essential components in the solar system.
They Store Energy
To overcome the volatility of solar energy, the batteries store excess energy and release this as required. The problem with this solution is that batteries are a relatively inefficient technology.
The Amount Of Energy Released Can Be Controlled
The problem with solar energy is that only the energy available now can be consumed.
The sun’s energy is constant. Pushing a throttle and increasing the sun’s energy is impossible.
This is where the battery comes into play. The solar energy is converted to electrical current and stored in the battery system.
It can then be discharged from the batteries at whatever rate the systems require.
The most obvious component of the solar system is the electric motor, which propels the boat.
The motor is connected to the inverter/charge controller via the throttle. The throttle is essentially a rheostat controlling the current amount to be discharged from the battery.
As the throttle setting increases, the rheostat opens the connection more and withdraws more current from the battery.
The increased current provides more energy to the motor. Which, in turn, speeds up.
👍 Benefits and Advantages
Several compelling benefits are achieved when switching your boat over to solar power.
The environmental benefits are the most commonly used to justify switching to solar.
With the technology widely used today, this is not as clear-cut an argument as proponents would have you believe.
Solar systems are essentially zero-emission power sources. However, the benefits are offset by the large emission releases and human rights violations committed during the manufacture.
- Essential minerals are mined in central Africa, and documented cases of child labor are being used.
- The manufacturer of solar panels is not an eco-friendly operation, nor is the end-of-life disposal of these components.
These are not reasons to abandon solar; however, the environmental impact arguments should not be the primary reason for switching to solar.
The efficiencies that a solar system brings are an argument that can be used to switch to solar power.
Solar panel efficiencies have improved with recent technology and continue to grow. The solar panel’s efficiency is measured by the amount of electricity generated by a given sized panel receiving a known solar energy rate.
That may sound a little complex – essentially, the amount of electrical energy is calculated as a percentage of the solar energy received. All measurements are done at the equator.
A panel that is 100% efficient would convert all the solar energy into electricity. An example of this is
If a panel measuring 1m2 receives 1kW of sunlight and produces 1kW of electricity, it would be rated 100% efficient.
Unfortunately, that technology doesn’t exist, and high-efficiency Monocrystalline Solar Panels that are efficient only convert 23% of the sun’s energy into electricity.
Despite this, as long as the sun is shining, solar energy is available, which is wasted if it is not converted into electricity. This means that despite not being 100% efficient, solar systems are still considered energy efficient.
The cost of a solar system is balanced against the ongoing gas or diesel prices to fill up the boat’s tank.
While installing solar panels on a boat is expensive and ranges between 100% and 400% premium over a gas engine, the long-term savings are considerable.
A solar boat is not subject to the whims and volatility of the international oil price. While American gas prices currently average around $3.50 per gallon, they have shown massive peaks over the years. This is shown in the following table.
|Price per gallon (adjusted to 2023 $ values)
|Start of 2nd world war
|Desert Storm Iraq War
|Russian Invasion of Ukraine
Owners of solar power systems are not affected by these price swings in the oil price.
👎 Challenges and Limitations
As with all technology, solar power boats have challenges and limitations.
As discussed earlier, a solar system’s operation depends on weather and time of day. While battery systems overcome this constraint to some degree, they have a finite capacity and will eventually need recharging.
Unlike a gas tank that can be filled up regardless of weather conditions, a solar system needs access to solar energy (the sun).
Speed and Range
Just like gas-powered boats, solar-powered craft have a finite range that they can operate before they need to be recharged.
With the largest batteries and electric motors, these ranges continually increase and are beginning to match gas-powered boats.
The real frustration occurs when it comes time to recharge. There are no such things as “top up and go,” which gas-powered boats enjoy. Recharging is an extended process.
Superchargers are becoming available in the electric vehicle market, substantially reducing the charging time. The same availability does not exist for the electric boat market.
This will come with time as the electric boat market begins to surge.
🚤 Notable Solar Powered Boats
Solar power propulsion systems (and the boats in which they are installed) are becoming increasingly available.
The applications range from small 1HP (equivalent) outboard motors on a small Jon boat to systems that propel large catamaran vessels.
The following manufacturers are just a few that produce a wide range of electric marine motors.
At the other end of the spectrum are manufacturers producing high-value cruising boats.
🔮 Future of Solar Boats
As with all newer technologies, the rate of growth and advancement is increasing. I expect the market to develop in the following ways.
Solar panel technology will become more efficient, and in the next five years, solar panels will reach a regular efficiency rate of 35% or more.
This is a virtual doubling of efficiency rates and, in simple terms, will mean that ½ the number of panels will be required to generate the same power.
Battery Technology Will Improve
Substantial investments are being made in battery technology. Hopefully, the end result will achieve the following.
- Batteries Will Become Cheaper.
- Batteries will have a longer expected lifespan.
- They will have an ever-increasing capacity, increasing the range on offer.
- Recharging times will be reduced.
Electric motors will become more efficient and use less energy to travel the same distance.
As the adoption rate increases, there will be increasing benefits for users.
- Prices should lower
- Service and maintenance centers will become more accessible
- The number of public recharging points will increase.
❓ Frequently Asked
Are there any specific maintenance practices unique to solar-powered boats?
Solar-powered boats require regular checks on their solar panels for any debris or damage, ensuring the battery connections are secure and monitoring the health of the batteries. While they have fewer moving parts than traditional boats, it’s essential to maintain the solar and electrical components to ensure longevity and performance.
How do solar-powered boats perform in comparison to traditional-powered boats?
While solar-powered boats may not match the top speeds of some fuel-powered boats, they offer a quiet, eco-friendly, and often more cost-effective mode of water transportation. Their performance in terms of agility largely depends on the boat’s design and the efficiency of the solar system installed.