When I want to recharge my batteries (metaphorically speaking), I like a combination of sun, wind and waves. Besides contributing to an energizing beach vacation, one company is turning the blend into a hybrid source of renewable electricity. German upstart SINN Power developed a power production platform that can be tied to a local grid or deployed as a microgrid to remote areas that lack a central utility. The company is currently testing its floating hybrid platform, a modular, scalable system that can house three forms of renewable electricity generation: photovoltaic (PV) panels, small wind turbines, and wave energy converters (WECs).
Per square meter, waves offer considerably more power density than solar and wind, and unlike solar and wind—which can be intermittent—ocean waves are relatively consistent. In spite of these obvious advantages, wave power remains a largely untapped resource, with just a few megawatts installed in various pilot projects around the globe, primarily due to its relatively high levelized cost of electricity (LCOE). Nonetheless, industry experts predict that electricity from wave power will increase dramatically in less than a decade, reaching a global capacity of 27 gigawatts by 2027. Several national utilities in Europe, as well as some heavy hitters in the private sector, are investing in WEC technology, hedging their bets on a clean, renewable source of energy that can be conveniently located near coastal population centers.
The Platform
Designed with modularity and scalability in mind, SINN Power’s platform is made to handle saltwater environments with minimal maintenance. Each module can accommodate any combination of up to four WECs, four small (6 kW) wind turbines, and 20 kW of solar panels. The modules, which fit in standard ISO shipping containers, can be arranged in any convenient physical configuration, and additional modules can be added as the budget allows. The open design provides easy access for construction, maintenance and repair.
The buoys and WECs combine to create a damping effect—a high-tech shock absorber, as it were—drawing energy from waves as high as two meters, converting their motion into electricity, and keeping the platform’s surface relatively still. The platform itself can withstand waves up to 10 meters in height—something that might occur during a Category 2 hurricane.
Multipurpose Powertrain
After considerable research, SINN Power concluded that existing off-the-shelf generators were unsuitable for the harsh saltwater ocean environment, so the company developed its own: the Powertrain, a 3 kW permanent magnet generator with integrated power electronics, which allows multiple Powertrains to be wired in parallel. Housed in saltwater-resistant coated aluminum, the generator has an IP68 rating, which means it’s impervious to dust, dirt and liquid. In addition to the built-in power electronics, the Powertrain features customizable gear ratios, a mechanical brake, and a rectifier that produces a DC output.
To further reduce costs, the Powertrain was designed for SINN Power’s wave energy converters as well as the small wind turbines that the platform is designed to house. This puzzled me at first since waves produce a reciprocating motion, while turbines and most generators use rotational motion, so I wondered how they go from up and down to ’round and ’round. Conventional ways of converting reciprocating motion into rotational motion include a screw, a rack-and-pinion, a slider-crank mechanism (like old steam locomotives had), and others. SINN Power’s WEC uses the company’s patented system of rollers pressed against the WEC’s vertical shaft, with each roller turning the shaft of a Powertrain. It’s similar to a rack and pinion, but without the teeth. The patent says that the rollers themselves can be used as generators, but the company’s WEC uses the Powertrain instead.
Wave Energy Converter (WEC)
SINN Power’s core technology is the brainchild of company founder Philipp Sinn, whose doctoral dissertation explored the concept of a modular, scalable wave energy system made from standard components suitable for mass production. Upon graduation, he received financial backing to found the company and continue his work.
The WEC comes in two standard configurations: a 24 kW model for moderate wave climates and a 36 kW model for strong wave climates. In each, four Powertrains are mounted at 90-degree angles to one another, forming a 12 kW group. The 24 kW unit has two groups, while the 36 kW version has three.
Wind Power
Normally, I’m not a big fan of small wind turbines—their low altitudes don’t get access to the high-speed winds needed for good energy production, and their small cross-sectional areas don’t grab a substantial portion of the wind. As a result, their payback periods are usually longer than the turbine is designed to last. In this case, however, I can see reasons to add them to a floating platform. First, although the turbines are low in elevation, the ocean winds are unobstructed and relatively steady, not turbulent. Second, their long payback periods are based on U.S. average electricity rates, while a platform like this is designed for remote locations that may use expensive diesel fuel generators or have no source of electricity at all. In those cases, you take what you can get.
SINN Power doesn’t make wind turbines, but it encourages turbine manufacturers to use SINN Powertrains, whose DC outputs and control electronics allow Powertrains to be connected in parallel with a single DC bus, reducing the number of inverters needed for grid integration.
Solar
Floating solar offers numerous advantages, not the least of which is a built-in cooling system that keeps the solar panels running efficiently. The SINN Power platform is built to house up to 20 kW of solar panels per module. The company is looking for PV manufacturers that want to test their products at SINN Power’s test site in Greece. The configuration shown here would be oriented east-west, with one set of panels doing well in the morning and early afternoon, and the other set taking the early afternoon to early evening shift. This would be ideal in equatorial latitudes where the sun more or less rises due east, travels overhead, and sets due west. In more temperate zones, south-facing panels (in the northern hemisphere) tilted at the site’s latitude would be preferable.
Energy Storage
SINN Power offers a few energy storage devices, which are also designed with the company’s “modular, scalable, and inexpensive” mantra. Its lithium iron phosphate (LFP) battery has a 1.5 kWh capacity and includes a built-in battery management system, microcontroller, and battery health monitoring. For quick bursts of energy—incoming or outgoing—the company’s supercapacitors, which are roughly the same size and weight of the battery, albeit with much less storage capacity, can be added. In both cases, multiple units can be configured in series or parallel, depending on voltage and current requirements. Like all the company’s electrical products, they’re IP68 rated.
Floating Microgrid
Scientists estimate that more than a terawatt of wave power is available around the globe—we just need to find a cost-effective way to harness it. Best-case scenario, wave power becomes a base load generator, producing a substantial portion of the grid capacity. I don’t see that happening in the near future, but in remote areas where grid power is costly or nonexistent, a floating microgrid that combines solar, wind, waves and storage could do the job. By filling a niche market now, companies like SINN Power can continue their research and development into new wave power technologies that could, someday, become a major player in renewable energy.