The TITAN 200 in all areas of evaluation projects the highest score as compared to other fondation designs.
There are numerous factors which show the Titan Wind Turbine Platform is superior to all other foundations for offshore wind turbines in water depths over 50 feet. This section discusses all the related factors, evaluates each factor and determines a relative score. The overall cost of installing and operating an offshore wind turbine is the basic consideration. Comments and discussion of each area of concern is given below and given a weighted evaluation:
Heavy Lift Crane Rental
In the case of support equipment requirements the Titan Platform design eliminates the requirement of heavy lift vessel that are common in the offshore industry and can cost as much as $100,000.00 to $200,000.00 per day (day rate) depending on the specialty of the vessel adding a huge cost to the installation process. These vessels are weather dependant meaning that projects potentially lose scheduled days and valued installed production time (redusted profits) for each day of delay times the number of units, these vessels are also in demand by the oilfield and not always available. Therefore high cost and a lack of dependable equipment are the consideration. Heavy lift vessels are required for moored installations, such as Spars and Pontoons as well to place anchoring structures on the sea floor and the same considerations have to be made.
Titan Platform The design is self installing. After launching sea water is used to transport the platform. When at the time of launch from the shipyard the Titan Platform is a vessel and transportation is accomplished by towing the platform to its assigned location for installation. No assembly is required. Once the platform is at the location, sea water is used to install the platform. The legs of the platform are lowered to the sea floor and then ballasted downward. This causes the footings to penetrate the sea floor. As the footings proceed to drive deeper into the sea floor, the vessel is raised above the normal sea level and creates an Air Gap between the vessel’s bottom and the water. Eventually, the legs penetrate to their proper depth and converts the vessel into a platform for the support and normal operation of the wind turbine. Thus the vessel/platform is self installing and no heavy lift vessel is required. This system uses a common everyday practice used in the oilfield for the past 50 years and is safe and proven stable. The Titan’s machinery used to lower and raise the legs is completely portable and can be removed for use on remaining platforms for a given wind farm, or reinstalled later for decommissioning or repairs from storm damage or used to adjust the platforms location to gain more efficiency for the pattern of platforms in the production of power.
Transport and use of Concrete / Aggregate: Many systems require their bases to be stabilized within the soil, this adds cost and time to the system and project overall. Vessels and weather are a concern as with all heavy lift vessels. The Titan Platform vessel and the legs it stands on are designed to penetrate the sea floor and be sable without the use of additional materials. This is common practice in the oilfield and it is not uncommon for a jack-up drilling rig to stay in one location for 5 years. Rules and regulations which we design to require the legs to withstand a category 5 storm and extreme conditions of various kinds. Additionally, The wind turbine platforms must be designed for a 25 year design life, which is not uncommon in the oilfield.
Ecological Damage to the Sea Floor / Nature of Damage / Impact on Nearby Fishing: In all cases of the sea floor foundations there will be some sort of damage. The systems that use concrete and aggregate normally cause the most damage and are the most difficult and costliest to cleanup. Blasting structures out of the sea floor and removal by heavy lift vessels are required by practice and by regulators. In most cases the structures attract wildlife of all kinds but being the least intrusive should be the goal.
The Titan Platforms are the least intrusive system available and that has been proven time and time again in the oilfield as far as sea floor disturbances are concerned. We simply lower our vessel to the sea level and pull our legs from the seafloor. The later settling of the seafloor silt results in normal seafloor conditions. The Titan Platform system is the least intrusive.
4. Stability: Stability is key to the performance of the wind turbine and therefore the production of power and resulting profits. If the platform is fixed to the bottom seafloor directly and if it is designed to withstand a severe storm condition and have the support tower of the turbine remain in its original manufactures specified vertical position, then this is what is required. Unfortunately, a ridged vertical position for monopoles and tripods require deep penetration of piles to accomplish this rigidity, typically 3 times the water depth below the sea floor and are also limited to maximum water depths of 60 feet. Therefore, 60 ft water depth, plus 180 ft below the sea floor plus 50 ft above the normal sea level of 290 foot of column for monopoles as a example. This results in considerable steel weight and high construction cost, when the minimum wall thickness is 3 inches and the diameter of the pile is an average of 20 ft.. The limited water depth capabilities also contribute to the view shed problem as they must be installed close to the land.
Floating systems such as TLP (Tension Leg Platforms) and moored systems have their own set of unique problems. Floaters that support great amounts of weight such as a 3.6 MW wind turbines and towers must be very buoyant and therefore displace the equal amounts of water to reduce the weight. Sea based wind farms require that the installation be based upon the economics of cost vs. profit. Therefore, the largest capacity turbine in MW output for each platform site must be installed to be a feasible deal. That means the steel weights to construct such a vessel is considerable based upon the area of displacement required. The other problem from a performance stand point is that no matter how much the vessel is anchored, it will stretch the cables and tilt the platform in the direction of the wind and wave conditions at the time of operation. The object is to use the wind force to efficiently generate power. Manufactures of turbines specify the optimum vertical plane that the turbine must operate within to produce power efficiently. The problem gets worst as water depth increases, therefore, on a typical application the maximum tilt of the tower may not exceed +/- 0.02 deg. And in 200 ft of water depth the platform movement in the horizontal plane can be as much as 3 ft. resulting in a 1 deg. Variance, resulting in a reduction of power output.
Titan Platform: The Titan Platform is stable and designed to meet the requirements of the regulating authority such as MMS of the US government. It will pass third party evaluation to the same standards used for drilling and production operation throughout the world. The Titan Platform is able to withstand a CAT 5 storm and continue operations after inspection of the turbine equipment. On a everyday bases the Titan is able to adjust and hold a tolerance of +/- 0.01 in the horizontal plane by means of adjusting the elevation between leg heights from the water line which is monitored and measured dynamically at the time of installation.
Maximum Operating Depth: Almost all installed support structures throughout the world today are 60 ft or less water depth. Physics of the monopole and tripod systems limits their capabilities to go to deeper water. Moored systems that float can be installed in much deeper water but the physics of the design are limited by the platform capabilities to support a large turbine and hold an acceptable tolerance in the vertical plane.
Titan Platform: The basic Titan Platform design is easily capable of deployment in 200 ft of water depth, which enables the turbines to operate far offshore with the flexibility to be redeployed in its rated water depth any where. In the oilfield platforms of the jackup design operate in 600 ft of water and in the worst storm conditions in the world.
Sea Floor Preparation Requirements: For all sites the sea floor must be surveyed to determine the conditions and not all areas are flat and stable soil conditions. In fact most sea floors are not flat . These conditions cause additional expense in installation costs for virtually all other designs with the exception of a jackup design. Uneven sea floor conditions do not allow a foundation to be simply placed on the sea floor. Finding a flat surface or preparing one, which is a hard task in 100 ft of water or basically at any depth. Gravity foundations all require site soil modifications which is added cost. TLP and moored systems need a flat surface to work from for even load distribution at the surface in tensioning the cables to be able to hold the tolerances required. Monopoles and tripods being driven deep into the soil have problems as well in that typically it is not know what is below the sea floors surface. Rock and debris cause installation problems, caves cause stability problems. Additionally, if the spacing or distance between turbines for the overall farm changes due to the bottom conditions the efficiency and profits of the farm are reduced.
Titan Platform: The Titan Platform is designed to deal with these conditions, in fact all jackups are designed to deal with the worst of sea floor conditions, uneven surfaces; legs are off-set in elevation, soft bottom conditions; the feet of the legs are deigned with additional area to cause them to penetrate to the proper depth. If there are obstructions below the surface we simply rotate the platform to provide a reorientation of the legs and reinsert them into the sea floor on the same centerline for the turbine.
Decommissioning Cost: The industry is so young at the present time that the 25 year design life of the offshore turbine installations have not required decommissioning to date, therefore to make this comparison we can draw from a similar industry. That being the oilfield production platforms installed offshore in the Gulf of Mexico, and in general the removal of those installations and reclaiming the site has cost the industry on average $4 mil. USD per site. This is simply the cost of doing business.
Titan Platform: The Titan decommissioning costs is the best in all cases. The sea floor is left virtually undisturbed. When decommissioning the wind turbine from the site, the platform is lowered using the same machinery used to installed the platform, pull the legs from the sea floor. Nothing is left but the inclusion of where the legs where and it fills with silt over a short period of time. The costs for the services to do the operation is a few thousand $ USD.
Storm Effect: Based upon the recent storm damage in the Gulf of Mexico and the resulting rule changes within MMS in Washington DC, the requirements for support structures are becoming much more robust. The requirements of survival of a CAT 5 storm of the structure will require stronger overall structures, which mean more cost, Monopoles and tripods will face the greatest problems in this area as they are marginal in design even in 60 ft of water depth. When wind loads and wave loads go up, then the cost goes up proportionally. MMS is now requiring a 50 ft wave consideration in the design before approval to deploy a site, which means more steel and more cost. Floating structures, TLP and moored systems will be under water in all design cases like these and the tensioning systems must be able to survive the buoyant loads of 50 ft waves and the unloading of the tension system in the trough of the wave as well and then the reversal of the load as the wave comes back. The Titan “jackup” design allows for such conditions to occur and survive. Rigs have operated in the North Sea everyday for the last 50 years under these conditions by raising the platform height to a known maximum clearance or “Air Gap” between the normal sea level and the worst storm conditions known for that area based upon records. Waves pass under the platform not through it, the legs are designed to withstand the force of the wave and provide the least amount of exposure in area to the wave to reduce the effects of the wave. Wind is considered in the loads in the design phase as well so that the combination of the weight and distance between legs will resist any predetermined overturning moment loads. The legs are always in compression, loaded downward.
Platform Maintenance on a 25 Year Life Cycle: All the designs will require annual inspections by regulators and third party surveyors to be able to operate. They will be checked for proper material conditions as compared to the original design approvals by MMS and other regulatory bodies. If machinery such as tensioning equipment is required as in TLP and moored designs they must be maintained and in good working order as well. Corrosion is always a problem offshore, therefore, corrosion allowances must be considered in the initial design and on a annual bases. The Titan Platform is no different with respect to the requirements, but it is less exposed to the salt water and by use of anti-corrosion devices insure little problems passing the inspection requirements. The Titan Platform is a steel structure when installed and is only a steel structure; therefore, machine maintenance is not an issue. We have a good history from the oilfield to make this comparison and our history is excellent.
Cost Index monopoles and tripods require great amounts of steel to be placed below the sea floor surface and these designs also require installation vessels that cost considerable amounts on a daily “Day Rate Basis” and are weather dependant. Basically it is a dollar per pound shipyard construction cost that is the real factor, steel cost and shipyards labor rates combined.
Cost are based upon industry reports, shipyard survays and audited project data, details provided upon request.
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