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Ocean Energy

Ocean Energy

One of the ways to capture energy from the ocean is through temperature. Ocean thermal energy conversion (OTEC) is a renewable energy technology that uses the ocean’s temperature variations to create electricity. For those of us who have been in ocean waters, the temperature difference between the sun-warmed surface and a few meters below the surface is noticeable. Temperature differences increase with depth. OTEC is particularly viable for tropical regions where there is a 20 degrees Celsius difference or more between surface and deepwater temperatures.

An OTEC facility has three main phases. First, warm water is introduced into a closed loop system containing a low boiling point carrier liquid such as ammonia. The warm water vaporizes the ammonia, which then passes through an electricity-generating turbine. The vapor’s pressure is then dropped by a condenser connected to the inflow of cold seawater. The now liquid ammonia begins the energy cycle again by being reintroduced to warm water.

The upfront costs of an OTEC facility are substantial, especially compared to long-term maintenance costs of the facility. Cost effective strategies factor location and materials. Ideal sites involve deep ocean waters with nearby shorelines. The piping system to bring cold water up is often one of the most expensive aspects of the facility, but evolution of cheaper, lighter weight and more durable materials will bring these costs down. Additionally, implementers are trying to increase efficiency by using waste heat from industrial processes to increase ocean water temperature differences.

The U.S. government has varied in its funding of OTEC technologies. In the 1970s, funding was provided for research and development but this funding has decreased and today, there is no official subsidy program to finance start up costs. Without the government subsidies that other renewable energy technologies experience, it is difficult for OTEC facilities to gain traction as viable, widely implemented energy sources. In spite of the history, stakeholders are optimistic that rising energy costs, increased concern for global warming and political commitment for energy security will make OTEC commercialization an attractive energy option in the future.




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Organic Farming: Energy Efficiency?

This past weekend, I went to Coyote Farms in Elgin, TX and got a tour of their farming operation. The farm primarily produces organic eggs and organic animal feed. Some of you may have seen their eggs in Austin stores; they are labeled as Jeremiah Cunnigham’s World’s Best Eggs. Coyote farms produces 100% organic products. Their vision is to revitalize middle income farming practices through sustainable faming techniques and humane treatment of animals. A significant portion of the farm’s business is derived from the organic feed. Coyote Farms is the only organic feed producer in Texas. All of their feed components are sourced in Texas and mixed on the farm. A significant portion of the tour was dedicated to explaining the feed production process. A mixture of wheat, soy, legumes and other grains comprise most feeds (a fraction of their feed is produced soy-free). Because of the nutritional variation of products, Coyote Farms regularly performs nutritional testing to ensure their feed maintains constant nutritional levels. Apparently, peas grown in west Texas can have different vitamin and caloric values than peas grown in east Texas due to geographic variations in soil, sun and rain, for example. The farm experiences high demands for their organic feed and they often struggle to have enough supply of raw feed components. The farm is hoping to promote more Texas farmers to produce organic grains. Coyote Farms believes that there is a greater demand for organic agricultural products than there is a supply.

While energy was not explicitly discussed on the farm tour, a couple of points about energy inputs and outputs came to my mind. The first relates to a comment from John, the tour guide. After explaining the complexities of combining grain and legume components to make feed, John said that the farm was interested in producing organic, nutritionally dense feed rather than large quantities of simple calorie dense feed, typically produced by conventional means. John followed up this comment by stating that because organic feed tends to be more nutritionally dense, farmers usually use less than they would conventional feed. He also said that livestock tends to be healthier on an organic diet therefore decreasing farmers’ cost of medicine. While John’s comments were anecdotal, the nutritional efficiency that he spoke of made me wonder how and if it translated to energy efficiency.  Since the raw materials for the feed come from all across Texas I wonder if the Texas environment is well suited for growing these items. Does the desire for “locally sources” trump environmental efficiency? In Dr. Webber’s lecture we learnt about the energy inefficiency that can result from growing food locally in un-ideal environments. When considering the environmental factors, the research reveals that there are numerous benefits to organic livestock and dairy production versus conventional rearing. Output comparisons show reveal slightly different results. With respect to organic feed for cows, for example, they produce less milk on average on organic feed than on conventional feed. This is probably due to higher volumes of feed given and that conventional feed tends to have higher protein ratios. In pig rearing, similar trends reveal that pigs on organic feed grow to smaller sizes on average than pigs fed conventional feed. In considering these differences however, it is important to note that we compare organic farming outputs to conventional industry standards, which in essence are inflated to above “natural” outputs for many of these animals. The conventional livestock industry has gone to great lengths to modify animals, living conditions and feed to increase yields. Thus, while organic production and feed may yield less output than conventional practices, a more holistic assessment must incorporate various factors including environmental impacts, treatment of animals and human health impacts resulting from consuming organic products. Coyote Farms is addressing all these factors and they are producing quality products whose market share, particularly in the Austin area, is growing at a fast pace.


Blair, Robert. “Nutrition and Feeding of Organic Pigs”, 2007.

Sundrum, Albert. “Organic Livestock Farming: A Critical Review”. Livestock Production Science; January 2001.


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