Is it a vessel? Is it a power plant? Wait – it’s both!
by Roman Elsener
The SeaFloat is a fully integrated solution that is prefabricated in a controlled area at a shipyard, then transported to its destination.
The SeaFloat concept: A conventional, gas-fired power plant on the water that doesn’t have to be tied to one location.
When people think of a power plant, they see in their mind's eye a large facility on a piece of land. Over years, planning takes place, a site is secured, permits are obtained. Finally, the facility is built, connected to the power grid and, once the turbines start turning, the assumption is that it will remain there for decades.
But what if no site is available, for example in a densely populated area where land is expensive and large parcels are difficult to obtain? What if it is not certain how long electricity will actually be needed in the area? Or how long a contract between a power producer and its customers will remain in force?
The SeaFloat concept was developed to address these issues. Conventional gas-turbine technology on a floating platform, together with battery storage, forms a turnkey power plant that can be positioned on large rivers or along a coastline. The floating plant generates electricity quickly and independently of the location.
Plug-and-play principle
Stefan Linder, Director New Generation Sales, North America, and Steffen Reising, Senior Sales Manager for Power Plant Equipment at Siemens Energy, offer comprehensive expertise in the SeaFloat program and its turnkey design. “It is a mature concept that can be reproduced in series,” Linder said in a recent interview. Reising agreed: “We offer a fully integrated solution that is prefabricated in a controlled area at a shipyard – basically, the entire power plant is put together like Lego, according to the plug-and-play principle.”
There are practical advantages to this: a shipyard has cranes, heavy-lifting equipment, skilled workers and an established industrial supply chain. Building the plant there avoids the need for complex construction work on site – assuming that were possible. Once completed, the plant is transported to its location – a reversal of conventional infrastructure.
While the majority of market requests are for the successful SGT-800 gas turbine, the SeaFloat concept has also been assessed with alternative gas turbine platforms, including the SGT-8000H series, to address a variety of market requirements. In addition, Siemens Energy gas turbines used for offshore installation are well suited to meet particular operational needs, such as SGT-A65, SGT-750 or SGT-400.”
Santo Domingo, the vibrant capital of the Dominican Republic, welcomes Estrella del Mar III on the Ozama River
Relatively calm waters
A SeaFloat plant is designed for marine conditions, but it cannot be anchored anywhere. The floating power plant is intended for near-shore, relatively calm waters, where the barge is less exposed to rolling and pitching from waves.
This makes it possible to use much standardized industrial equipment above deck, rather than requiring the elaborate marine technology necessary for plants operating on the open sea. Thus, a SeaFloat functions largely like a conventional industrial power plant, but with a much smaller footprint compared with traditional power plants. Optimizing the barge topside area results in a cost-effective solution unlike traditional power plants which typically occupy a considerably larger area.
From an interim solution to a long-term asset
In markets where electricity demand grows faster than infrastructure can be built, floating power plants have long been established. The first so-called “power barges” were constructed during World War II to bring electricity to shipyards or disaster areas. Today, there are companies that operate fleets of power ships that provide electricity for clearly defined periods – particularly in markets where conventional generating capacity is difficult to finance or build.
The model is intentionally flexible. A customer can sign a power purchase agreement for several years. If the contract is extended, the power plant stays where it is. If it is not extended, the power barge moves on. A solution that was originally intended to be temporary can thus become a medium- or even long-term source of electricity. This flexibility is something a conventional power plant cannot offer.
When there is no space to build
In emerging markets, the problem may be inadequate infrastructure. In densely populated, wealthy cities, on the other hand, land may simply be unavailable or unaffordable. In sparsely populated remote areas, underdeveloped, or even highly developed areas, such as major city centers, mobilizing the necessary resources, cranes, personnel, accommodations, etc. costs time and money. Here, SeaFloat, built in a controlled environment, offers a low-risk solution for power generation needs.
New York City is a good example: sites for new energy infrastructure are expensive and difficult to obtain. Building permits are also hard to come by. This explains why a floating power plant is in operation in Brooklyn. With the SeaFloat solution there is no need to find a large industrial site on land. The other advantage of the Brooklyn Bay plant is that electricity can be generated close to demand.
A flagship example
A prime example of a SeaFloat is Estrella del Mar 3, a 145-MW combined-cycle power plant on a barge in the Ozama River in Santo Domingo. The plant was largely built in Singapore and then transported to the Dominican Republic.
Seaboard Corporation, the owner of the plant, opted for a first floating platform more than 20 years ago because it was not clear how long the customer would need the electricity, according to Stefan Linder. What would happen if the economic or political environment changed? A land-based power plant would leave the company with a large, immovable asset. A barge offered a way out.
The concept has proven itself. Estrella del Mar 3 is already the third floating plant in operation, while Estrella del Mar 2 will be deployed by Seaboard Corporation elsewhere. And because electricity consumption in Santo Domingo continues to increase, Estrella del Mar 4, based on the same basic concept, is currently under construction, intended to operate in parallel with its sister plant. The two power plants use river water for cooling and steam generation..
Battery storage for frequency regulation
The power-generation technology used by Estrella del Mar is remarkably similar to that of an industrial power plant on land. It has two gas turbines, two heat-recovery steam generators and one steam turbine in a “two-on-one” combined-cycle configuration.
A battery storage system enables the fast-response services required by the power grid. The system provides frequency regulation and thus allows the plant to respond to fluctuations in the grid without having to hold back generating capacity from the gas turbines.
This integration is part of what makes the concept so unusual: the combination of traditional power generation and battery storage in a single floating system.
This approach earned the project POWER magazine's 2023 Plant of the Year award.
Flexible interfaces
Linder emphasized that the floating platform does not require an HVDC connection. Because Estrella del Mar is located close to shore, the grid connection is made using high-voltage AC. Transformers and gas-insulated switchgear are located on the platform, while AC high voltage overhead lines establish the connection to the power grid.
A substation on land does not rise and fall with the tides. The floating power plant with HV equipment does. The electrical connection therefore has to compensate for the movement of the platform while simultaneously maintaining a reliable connection to the power grid. Every interface that would be static on land has to be able to tolerate movement.
Maintenance is no marine operation
On the other hand, marine expertise is not required for maintenance, Linder said. The maintenance approach is “basically no different” from that of a land-based power plant. Routine maintenance can be carried out at the plant itself, while major overhauls and repairs can, when necessary, be carried out on land.
The operating personnel – in the case of Estrella del Mar, around 30 employees – essentially remain on land and attend work on the barge when needed. No one has to live permanently on board.
Turbines capable of using 75% hydrogen
The SGT-800 gas turbines can operate with significant quantities of hydrogen, currently up to 75 percentage by volume. The SGT-800 gas turbines at Estella del Mar 3 & 4 are designed for natural gas fuel only, but can be modified to operate with a hydrogen blend, enabling future decarbonization of electricity generation. This makes it tempting to describe floating gas-based power generation as a step towards a low-CO₂ power system. But Linder and Reising are cautious in their forecasts.
Steffen Reising highlighted the availability of green hydrogen as one of the key challenges facing the energy industry. His concern is not whether turbines can burn hydrogen, but whether sufficient quantities of green hydrogen will be available, and if electrical generation will remain affordable as the hydrogen economy continues to expand.
A turbine may be hydrogen-capable. But fuel supply cannot be planned by the turbine manufacturer. The technical equipment could ultimately be capable of becoming CO₂-free, but the supply chain lies outside a company's control, Reising explained. He pointed out that many industries, including the chemical industry, transportation and aviation, are likely to require significant volumes of green hydrogen as they pursue their decarbonization goals.
Economic benefits for different markets
Linder, too, agreed that technical plans for switching to a green fuel may exist on paper, but the economics and electricity tariffs will determine whether the switch ever actually takes place.
Which future fuel will ultimately prevail is not clear. That is why perhaps the most interesting aspect of SeaFloat is not the fuel, but the flexibility that a movable power plant provides and the options that remain open to electricity producers enabling them to meet regional decarbonization goals.
Linder identified several markets in which the ability to relocate a power plant could bring economic value: countries struggling to build infrastructure quickly; cities with little available land; industrial projects that need electricity only for a limited period; and oil and gas projects that do not want to permanently tie their generating capacity to a single location.
And therein lies the innovation of the SeaFloat concept: It separates electricity generation from a permanent geographical location, thereby enabling it to adapt to the needs of the population – and the planet.
Copyright: 3. Picture (Triphticon): 2x Getty Images/ Walter Bibikow, Getty Images/ Maremagnum; 5. Picture (Triphticon): left on top: EPS Este Project Service GmbH ; 8. Picture: Seaboardship
*nmHC: non methane hydrocarbones
About the author: Roman Elsener is the US Correspondent for the Swiss News Agency SDA, specializing in energy and healthcare. He has been a Primafila Correspondent for more than 15 years.
