Monster deep water offshore floating wind turbines are the new horizon for renewable energy

Andy Zalay / PE ME / President / Ewind

Andy Filak / Principal / Amfconcepts

John Reeves / PE PMP Naval Architect / Elliott Bay Design Group

With the U.S. grid saturated with PV (solar panels) and land based wind turbines and dotted with new gas peakers, the new horizon is barely visible offshore. It is monster commercial wind turbine generators (WTG’s) floating on concrete foundations 20 to 30 miles at sea.

The 8 MW Adwen turbine provides a hint at turbine sizes to come. Possibly two 10-MW units will be unveiled next year and other designs later on.

The U.S. goal is to install 86 GW according to the Global Wind Energy Council which is six times the current 14 GW worldwide wind capacity. In addition, 43 GW of offshore wind (50%) will serve U.S. coastal population centers according to the American Wind Energy Association (AWEA).

The deep water offshore wind farms will meet the public’s preference for out sight out of mind WTGs located away from commercial fishing areas and will reinforce the U.S. Grid without requiring new long-distance transmission lines and will balance conventional PV and thermal plants.

To reach the new offshore wind horizon, the following elements are required: Political will and public support, suitable wind resource, commercial technology offshore WTGs and floating foundations, and grid compatibility

Political will and public support

As a pioneer state accustomed to PV and lacking large areas for onshore wind, the state of Massachusetts has established a call for 1.6 GW of offshore generation by 2040. Other Atlantic coast states including New Jersey and Rhode Island and others as well as Pacific Ocean states (California and Hawaii) have the opportunity to follow this lead.  The states can establish incentives to promote offshore energy through competitive off-take and interconnect agreements and support the Bureau of Ocean Energy Management (BOEM) Task Force responsible for issuing outer continental shelf (OCS) leases to developers.

Highest coastal wind resources are deep water offshore sites

The highest consistent wind resources are found in deep water offshore sites.  A recent study in the UK demonstrates offshore wind energy sites surpass onshore sites in terms of energy content and consistency.

Technology for the monster turbines and floating foundations

Fresh ideas such as the MACC will take cost out of the production and commissioning of spar mounted offshore wind turbine.

Reliable low maintenance gearless offshore WTGs

The technology is available for direct drive monster 10 MW WTGs as evidenced by the commercial offshore wind farms on bottom founded foundations in Europe with 6 to 8-MW WTGs. The gearless WTG reduces weight aloft, improving performance while reducing operation and maintenance (O&M) cost. The new technology is the floating foundation substructures in water depths that bottom-mounted turbines are not feasible. The next generation of monster (10 MW) turbines, stand roughly sixty stories above the sea and when viewed from the shore 20 to 30 miles away they will be under the size of your fingernail. The manufacturing sites of these monster WTGs are ocean ports so that the WTG can be loaded directly onto vessels. The key WTG components are also manufactured portside because they are too large and heavy for land transport.

Cost effective durable floating foundations

Each major offshore WTG manufacturer is developing their own preferred floating foundation suitable for deep water sites similar to the design practice for onshore WTGS where the foundation design specs are WTG specific. The offshore WTG vendor has many choices for the floating foundation such as buoyancy (high water plane floater or spar buoy) or materials such as conventional steel construction or concrete and steel rebar construction or other innovative technology such as geopolymer cement with basalt rebar (GCBR ). One attractive floating foundation concept with the potential for the lowest cost and highest durability is the spar buoy concrete floater with GCBR as described below.

This is the floating substructure that supports the WTG and is constructed on one end of a large Ocean Going Deck Barge (OGDB) tied to the quay in the harbor. The WTG is assembled at the opposite end of the OGDB, and commissioned, ready for mating with the substructure at sea. No expensive heavy lift equipment is needed since the OGDB construction and deployment method air and water for final assembly of the WTG on top of the substructure after its launch from the OGDB and positioning. The completed floating turbine is then fixed to the station keeping system in the wind farm.

Grid friendly offshore wind

Faced with the retirement of coal and nuclear plants and grid constraints due to PV and onshore wind, the transmission serves providers and host utilities are considering the addition of offshore wind projects connected directly to the existing substations at power plants and coastal load centers.

The offshore wind projects can reinforce the grid (provide dynamic spinning reserve) and delay the need for new transmission lines by virtue of their permanent magnet motors with full four-quadrant inverters which provide voltage and VAR support analogous to the conventional synchronous generators found on baseload utility generating plants. By means of available predictive models, the output of the offshore wind farm can be balanced by the grid to diversify the generation mix. In effect, the offshore wind farm can serve as base load generator (dispatched generator) to balance the load such as intermittent PV solar (duck curve due to day to night shift in generation) and keep the lights on.

The way forward

Wind power has come into its own as the preferred source of renewable energy second only to hydroelectric generation as stated by the American Wind Energy Association (AWEA). With the U.S. grid saturated with PV and land based wind turbines and dotted with new gas peakers, the new horizon is barely visible offshore; monster commercial wind turbine generators (WTG’s) floating on concrete foundations 20 to 30 miles at sea and the realization of this vision lies in the hands of the public and our political leaders.

Reach the authors:

Andy Zalay, PE ME, President, Ewind, (949) 609 9897

Andy Filak Principal, Amfconcepts,,  (310) 373-5004

John Reeves, PE PMP, Naval Architect, Elliott Bay Design Group,,  (206) 204-1300

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