The power flower

Countries like Singapore are land scarce. With a population close to 5.1 million and a land area of about 710 square kilometers, the possibility of massive solar parks are close to impossible. One can even say a ‘weakness’ of solar installation is the hefty space often needed for chalking up the megawatts of power. As optimal as rooftop and building integrated photovoltaics can be, the reality is that these land-scarce countries need more compact solutions. For an island like Singapore, blessed to be in a region with high sun radiation, it is a shame to let all that sunlight ‘go to waste’. Yes, there are rooftops, but older buildings were not developed with the capacity of holding rows of solar panels adding significant stress to the structures. So when Hann-Ocean introduced its Hexifloat at the PV Expo in Japan, it caught the attention of pv magazine in terms of solutions for islands like Singapore . Floating PV farms themselves are not all that new. In Aichi, Japan, a fifteen by nine meter, water-cooled floating system of ten kilowatt-peaks is present in a reservoir. The Lotus in Taranto, Italy is also a floating PV farm of 20 kilowatt peaks developed by Enerdaiet. Hexifloat as well revolves around the core idea of solar energy. However, it ropes in wind, tidal and wave as well. Why all four? Sounds ambitious. Hann-Ocean’s Business Executive Andreas Knie explains to pv magazine that Hexifloat is not only a means of increasing energy output but also diversification so that the fluctuations in power outputs are reduced.
Henry Han founded Hann-Ocean Technology in 2005. The Singapore-based company has been focusing on floating platforms like pontoons, to support houses or cranes required for offshore construction. So the energy business is new for them. Knie explains how the idea came about. “Last year when conducting a feasibility study for a solar structure, we found that pontoons that would have been used for such solar structures to be sub-optimal. Unnecessary amounts of materials were to be used and the solid structure of the pontoon would have blocked the sunlight and impacted water flow. That is how Hexifloat came about. It is a wire and truss system and thereby uses lesser materials.”

The Hexifloat

What exactly is the Hexifloat? It is a patented aluminum and stainless steel, hollow, floating structure that integrates solar, tidal, wave and wind energies into one platform. The tensioned wire and truss system is optimized for ventilation, light penetration, strength and stiffness and allows the free-flow of water underneath the platform.
Solar modules are mounted onto the hexagons, on module suspension bars. The suspension bars are then locked onto the truss using locking rings. Solar modules occupy the most amount of surface area on the platform. The number of solar panels that can be fitted onto each hexagon is stated as 252, being the prime energy provider of the Hexifloat. At the sides of the hexagon, where two sides meet, wind turbines are found as the pictures illustrate. Directly below the nodes of the wind turbines are the tidal turbines. For wave energy generation, the company already has its own Drakoo wave energy converter. Knie explains that the concept that is being used to generate wave energy, for example, is different from the conventional buoys. The box shaped device is attached to the Hexifloat where a turbine is driven inside the box, a concept that Knie highlights is completely new. The box is attached along the perimeters under the structure. The entire hexagon has a diameter length of 27 meters, a breadth of 23.6 meters and a depth of 1.7 meters. It weighs 14 tons.
The breakdown of the structure in terms of energy provision is: 48 kilowatts-peak (kWp) of solar energy, 45kWp of wave energy, 23kWp of tidal energy and 18kWp of wind energy. In total, the Hexifloat can generate approximately 134kWp. The main highlight of the 4-in-1 structure remains the vast potential use of solar energy. Questions, however, that are raised include the ability of solar modules to withstand conditions out at sea, should they be installed in the open waters. If the Hexifloat is placed in a lake or reservoir, then the utilization of wave and tidal energy maybe minimum and the energy provision will fall back onto solar and wind. However, keeping in mind that the structure was developed to be used on a site where tides and waves are present, are there modules in the market that can withstand the conditions found in the rough sea conditions?
Modules that are selected to be mounted on the Hexifloat would then have to have made the cut under tests that are often more optional like the Salt Mist Corrosion test (example being IEC 61701), where the modules are tested for their ability to withstand the environment in coastal settings. That would have to be a primary concern of a project development with the Hexifloat when selecting modules. The junction boxes and cables behind the modules have to be extremely water proof and sturdy. The module frame itself also has to be extra susceptible to oceanic conditions. Shading is another concern that arises. When the integration of wind and solar energy is suggested, the idea gets questioned because of the shadows cast by wind turbines. “We are aware of this problem as a negative side effect of wind turbines. However, we think that the advantages from the increase and the smoothness of the energy output outweigh them. The wind and tidal energies do not affect solar. The diversification and higher output speaks for itself and shading becomes a small issue,” says Knie. The wind turbines as seen in the model are relatively smaller than the norm.
The Hexifloat itself can withstand a sea state of seven. A seastate is the general condition of the free surface on a large body of water with respect to wind, waves and swell at a certain location and moment. The scale goes up to nine. At sea state seven, waves up to nine meters can be withstood by the robust structure, as Knie highlights. The Hexifloat itself can be safely assumed to be a sturdy enough structure, having been developed by a company possessing know-how in the pontoon industry.

Getting it out to sea

From the installation side of things, it is essential to know how easy it will be for workers to get the system built and ready to go. Imagine solar installers having to lug 252 modules out to sea to mount them on the structure. No worries, says Knie. The Hexifloat itself can be assembled on land and mounted with modules and thereafter deployed into waters. When building a sea flower, a seven hexagon design, the individual Hexifloats can be connected in the water. Rigid Pontoon Connectors (RPCs) are used to lock the Hexifloats together. Within seconds, one or two people can lock in two platforms. It also works the other way around. Easy detaching is also enabled by the RPCs. “It works for our pontoons and thus works for our Hexifloat as well,” adds Knie. The Hexifloat itself, with all its individual components can fit snugly into a 40 foot (approximately twelve meters) container, enabling containerized, compact packing. Therefore transportation and storage is easy as well. It draws up the image of taking pieces of building blocks and snapping them together: as easy as that.

A swimming maintenance crew?

Once it is out at sea (assuming sea because of the rougher conditions it garners in comparison to a lake or reservoir), the solar panels mounted on the Hexifloat work in collaboration with wind, wave and tidal to generate electricity that is then channeled into an all-in-one charger-controller-converter on the Hexifloat itself which transmits the power to the shore via an underwater cable. Now, what if one of the modules malfunction? How can servicing be done? Does the developer then have to haul the entire Hexifloat back to shore (costing him extra money for hauling and thereafter repair or replacement)? Or will solar technicians also need to start having swimming courses for high seas? “No, there is no need for the maintenance crew to swim around underneath and conduct checks or repairs on the Hexifloat,” laughs Knie.
Maintenance crew can walk on the platform as the main picture shows. The structure itself is flat and the modules are tilted a little. This allows for a plank to be laid across and the service staff can walk across the hexagon in this manner to service single modules. The wire and truss system allows for the modules to be attached and detached easily. “Should an entire device (Hexifloat) require servicing, it can be detached as well (from the Seaflower),” elaborates Knie. “Of course, we do not want the Hexifloat to float away, so it needs to be anchored to the ground or moored,” he adds.

Certifications, costs and looks

Transferring the frequently asked certifications and costs questions to Knie. Does the Hexifloat already have certifications? “At this stage, it is still too early for official certifications. But we have done our own computer simulations, stability and stress analysis. We are looking into the required certification at the moment,” Knie tells pv magazine. Hann-Ocean has years of experience in the pontoon business so the patented platform itself is ready to go as Knie excitedly says. What is missing is the pilot project at the moment. And how much does such a hexagon cost (minus the cost for the energy generators)? It seems that we are not going to get any solid figures as of now. However, Knie reveals that the approximate cost of the Hexifloat structure itself is about 20 to 30 percent of the cost of the solar panels themselves. At a fraction of the cost of the investment required for solar panels, the Hexifloat seems to offer a cost-effective mounting platform.
The earth has more water than land surface area; common knowledge. This water surface area is waiting to be used in a positive manner that is not hazardous to the environment. Under such an argument, the Hexifloat fits in well as a great candidate. It also looks better than an oil rig for sure. Aesthetics speak for the Hexifloat. Design-wise, the company seems to have nailed it. To add to the perks, the centers of the Hexifloats are able to light up with LED lights as well at night. The Seaflower, being the combined Hexifloats in a flower-like array, then glows when the sun goes down. The layout can also be changed and alternative connection layouts of the Hexifloats to one another are also possible. At the recent PV Expo in Japan, the Hexifloat received really good feedback and solar module manufacturers have expressed interest as Knie informs pv magazine. Hann-Ocean is currently in talks. The first project to be secured looks to be happening not too far in the future. And if so, then the Hexifloat and its combined Seaflower power would be all set to generate energy from not just the sun, but wind and water as well. The extra perk of it all is that it looks good while generating green energy.