Differences and Advantages of the Sea Solar Power OTE Design

The Andersons, in the 1960’s, embarked on an extensive engineering study to evaluate and model how an Ocean Thermal Energy plant could be built economically and practically. They examined extensively what George Claude in Cuba and the French at Abidjan had done. From this knowledge base and new technology available on heat transfer and new manufacturing techniques, as well as knowledge from the refrigeration industry, they evaluated the advantages of building an Ocean Thermal Energy plant using a secondary fluid in a Rankine cycle versus the traditional open cycle approach used by Claude. Claude and d’Arsonval had both suggested the use of another fluid than steam, as in the open cycle, but at their time, heat transfer technology had not progressed to its level of development that had become available by the 1960’s.

SSP Hybrid Cycle to Make Power and Fresh Water

Through the years the Andersons developed their SSP plant using an innovative design approach using creative solutions based on a priori knowledge and up to date manufacturing technology and practical experience from the turbo machinery and refrigeration industry. The Andersons recognized early on that, with heat transfer employed to use a working fluid other than water, the approach temperature in the boiler and in the condenser had to be much lower than was commonly used in any commercial heat transfer product. They also recognized that to improve approach temperatures, increased heat transfer surface and or increased heat transfer performance was required. Increased heat transfer surface meant increased pumping power.

Through thousands of iterations, assumptions, years of testing, trial and error design revisions, the SSP designs evolved and have continued to advance through the years. Largely, the optimized SSP design employs some off the shelf equipment but many newly and improved design components that will ultimately lower the overall cost of an SSP plant. 7 independent engineering studies by different engineering groups have evaluated SSP’s proprietary work and confirm the correctness of SSP’s design. These studies offer useful suggestions and check costs in various ways independent of SSP’s estimates. Though there is not exact duplication of cost estimates, the 7 engineering studies do conclude the SSP technology is accurately applied and that SSP has tested and made design assumptions based on their own tests as well as outside data, industrial experience, and current prices at the time.

The Department of Energy work, which began with the National Science Foundation in 1972, developed baseline 100 MW floating plant designs using large government contractors. The studies concluded that Ocean Thermal Energy plants were feasible. The studies produced slightly different design approaches for the closed cycle plants but the projected sizes were similar and in the range of 200,000 to 300,000 tons of displacement. For the most part these plant designs used commercially available equipment with ammonia as working fluid. In fairness to DOE, the contractors were given about 9 months to do design studies. No testing and little prior knowledge was had by the DOE selected contractors.

Through other DOE contracts, various studies confirmed that aluminum was suitable as a heat exchange material and biofouling could be kept under control with small amounts of chlorination. Platform shape studies for sea worthiness confirmed that generally semi-submersible structures were acceptable and preferred for stability and for weathering storms at sea.

SSP heat exchanger test facility

Sea Solar Power’s design uses a hydrocarbon such as propylene as the working fluid whereas most other designs use ammonia. SSP’s total water flow requirements are significantly lower than other OTE designs. SSP has been building and testing various components and parts of systems since the 1970’s. SSP’s design for heat transfer, turbines, compressor, pumping, cold water pipe, and plant design are innovative and optimized for an OTE plant but are based on sound engineering principles, test results, and practical experience. The SSP design for a 100 MW floating plant would weigh close to 25,000 tons. This is significantly lower than the DOE projections.