Innovative Techniques

     Temperate fruit and vegetable crops have been grown successfully in the Natural Energy Laboratory of Hawaii Authority’s (NELHA) sub-tropical climate by utilizing the cold seawater to chill the soil. The combination of high solar insulation and cold roots has enhanced production and quality of many crops, including strawberries, grapes, asparagus, pears, gourds, alstroemeria flower, and many others.

     In the ColdAg process (developed at NELHA by the Common Heritage Corporation), designed for utilization in an integrated OTEC system, the deep ocean water (following usage in the OTEC power facility) flows through enclosed pipes embedded in the soil at the root zone. Temperatures as low as 10^oC are produced. This results in temperatures at the soil surface of approximately 25-30^oC. This is below the dew point in most tropical regions and moisture condenses at the surface of the soil. As the water continues to cool, it migrates through the soil until it reaches the coldest spot in the root zone. As the water migrates through the soil, it accumulates minerals and nutrients. The heat from the sun (as high as 37^oC in tropical regions) warms the flower and fruit and the heat diffuses down the stem to the root. The resulting thermal gradient carries nutrients up the stem at a rate proportional to the temperature difference between root (10^oC) and fruit (37^oC). Nature rarely produces a temperature difference greater than 9^oC. Thus, the ColdAg process transports nutrients at least three times as fast as nature! The cold water flow necessary to provide this effect is very small and costs associated with this form of agriculture in conjunction with a working OTEC system in which the cold water is readily available as a secondary contributor are far outweighed by the potential benefits. Likewise, associated costs are small compared to other costs (labor) generally attributed to the agriculture process.

Enhanced Production

     As a result of this fundamental process, the Common Heritage Corporation has been able to successfully produce more than one hundred crops from nearly every known climate. Dormancy can be induced by turning off the deep ocean water flow periodically and as a result four or more seasonal cycles can be achieved in one year. Fruit trees can produce as many as four crops on a single tree in one year. This is also true for grapes. Sunflowers can be "tricked" into producing more than a dozen flowers per stalk. The fruits are large and have a high sugar content (sweetness). It is estimated that 100 acres of agriculture can be had from the secondary use of water that has been employed to generate one megawatt (1 MW_e) of electrical power. The system employs standard irrigation pipes and standard farming techniques and can be maintained by agricultural workers.

Enormous Potential

     As you can see, agriculture utilizing the ColdAg process in conjunction with an integrated OTEC system can provide new and exciting industries to tropical island communities. Agricultural cash crops previously limited to commercial applications in the temporal zones of the globe can now be successfully, and profitably, grown in the tropical regions. Thus, an integrated OTEC system not only provides tropical island communities a reliable source of renewable, environmentally friendly energy and fresh, potable water, but also provides them with a renewable and reliable food sources to support the island’s inhabitants and tourism industry as well. Likewise, the potential exists to help diversify the local economy beyond conventional crops towards higher value exportable fruits and vegetables. This diversification can help establish a much needed extensibility to the current economic base and create more jobs for the local tropical island communities embracing OTEC technologies.