One fairly constant criticism of solar energy not being able to provide significant chunks of power for everyday life is that the amount of space and scale needed for installations that can meet those needs are staggeringly huge. For solar energy to make significant contributions to the electric grid, a whole lot of space must be devoted for power plants and solar farms.
For example, solar installations in the Mojave Desert, which receives about twice the sunlight compared with the rest of the U.S., can spread over five to 10 miles. Often, the high levels of sunlight craved by solar farms are found in the desert, but the drawback of locating huge solar installations in the desert is that not a lot of people live all that close to deserts, meaning additional infrastructure is needed to transport the electricity to population centers far away.
This gave Netherlands-based energy industry consultancy and certification firm DNV KEMA some inspiration. It has come up with the concept of large-scale offshore solar fields that float out at sea, and has dubbed it SUNdy. According to an article by BusinessGreen, the company’s designs for floating solar arrays could rival offshore wind farms.
The SUNdy concept is a 2-MW hexagonal array that floats on the sea surface. Arrays then are linked together, for a total of 4,200 solar photovoltaic panels, to form a “solar island” on water capable of generating 2 MW of power. Multiple islands connected together could then make up a solar field that can produce 50-plus MW of electricity — enough for 30,000 people. Such islands would be located in waters with depths ranging from 20 to 100 m (65 to over 300 ft), about five miles offshore and away from shipping lanes.
DNV KEMA officials say that because the SUNdy concept uses 560-W thin-film solar panels, which are lighter and more flexible than traditional glass-based modules and can move with the waves on the sea’s surface, it comes at an opportune time. Solar photovoltaics “is experiencing extraordinary market growth,” they say, noting that “almost 30 GW of operating capacity has been added, increasing total global capacity by 74 percent to more than 69 GW, according to the Renewable Energy Policy Network 2012 report.”
A SUNdy solar island would be stabilized by lengthy spread mooring, according to Bjørn Tore Markussen, chief operating officer at DNV KEMA Energy & Sustainability Asia. He said the floating solar field concept “offers sound and sustainable development prospects, particularly in Asia and the congested coastal megacities, where there’s limited opportunity for rooftop solar power and urban areas which command premium prices for large-scale mounted solar production.”
SUNdy floating modules would be manufactured as pre-wired units, which have the advantages of reducing the number of electrical connections and minimizing the need for offshore assembly. This is an important consideration when dealing with anything based on water — as wave energy collection schemes have learned — as components need to be not only waterproof, of course, but hardier and resistant to being jostled around.
Kevin Smith, global segment director for DNV KEMA’s Renewable Energy Services, explained that “the solar arrays are divided into electrical zones feeding electricity into two main switches collecting the power for voltage step up at a central transformer,” and electrical transmission lines connect other islands in series “to form a close loop and continue to the electrical sub-station onshore for grid connection.”
There are distinct benefits to such a scheme, DNV KEMA officials note. Compared to land, oceans have more space, and floating solar fields can be sited close to places where there is great energy demand. Although they profess reliability by noting that SUNdy doesn’t have many moving parts, anything on water, of course, will have more maintenance and troubleshooting issues than a land-based counterpart. Company officials also claim that SUNdy has a low visual profile; in other words, the solar islands wouldn’t be eyesores like offshore wind farms.
DNV KEMA hasn’t offered much information in the way of estimated construction costs for these islands. One can safely assume that they will be more costly than land-based solar installations of comparable energy output. This is one of the main issues, if not the main issue, with offshore wind farms, as they are much more expensive to build and maintain than land-based wind farms.
Renewables-Info.com notes that offshore wind energy projects need to be built to withstand rough weather conditions at sea. An article on the site says that the costs of installing an offshore wind turbine were around $5 million per megawatt of capacity in 2010, while installing a turbine on land has per-megawatt installation costs of half that.
Offshore solar islands do solve the issue of land use, which is one of the main drawbacks of terrestrial solar farms. According to industry observer Dennis Hartman, solar farms must be located in sunny areas and on “cheap land in remote areas.” While builders of solar farms may lessen the investment impact this way, the costs of transporting the electricity to those who need it far away rises as utilities must construct the infrastructure — electrical towers or underground power lines. And Hartman says solar farms usually cover many acres and thus run the risk of disturbing an area’s ecosystem, either when they are built or afterward “as animals migrate and plants change with the seasons.”
Offshore solar islands, on the other hand, can be located more optimally close to population centers, in the abundant space of the open waters. Because of this greater flexibility in siting offshore solar power, it has less probability of affecting marine life and disrupting shipping lanes, but if they do, these problems can be solved more easily than on land, where a solar installation can’t simply be moved.