India\u2019s project will tap 1,000-meter-deep sea water to generate 65 kilowatts of electricity and produce 100,000 liters of potable water per day. Developed by India\u2019s National Institute of Ocean Technology<\/a> (NIOT), it\u2019s a small project, but a big step toward a commercial breakthrough for OTEC. \u201cWhat we are doing is scalable in numbers for islands and remote communities. This can be a market strategy,\u201d says Purnima Jalihal<\/a>, who led the project before retiring last year as head of the energy and fresh water division at NIOT.<\/p>\n The project is part of a fresh wave of enthusiasm behind OTEC. Kilowatt-scale projects have been completed recently in China and the Canary Islands, and more are planned for Hawaii, Taiwan<\/a> and Japan<\/a>. While previous efforts to commercialize OTEC have come up short<\/a> amidst engineering snafus, efficiency shortfalls and funding constraints, today\u2019s efforts benefit from advances in key devices and engineering capacity. <\/p>\n Still, far bigger projects are needed before investment in OTEC will take off, says Robert Varley<\/a>, who led defense contractor Lockheed Martin<\/a>\u2018s OTEC program from 2006 to 2017. Most OTEC proponents agree, saying the field needs a demonstration of at least a few megawatts, which is an order of magnitude larger than the longest-running projects to date. \u201cOnce that happens, I think the world changes for OTEC,\u201d says <\/a>Varley. <\/p>\n How Ocean Thermal Energy Conversion Works<\/p>\n Earth\u2019s oceans absorb much of the sun\u2019s daily irradiation and excess heat trapped in Earth\u2019s atmosphere. But most of this thermal energy stays within 100 meters of the ocean\u2019s surface. The deep seas remain frigid, dominated by meltwater from Earth\u2019s frozen poles. <\/p>\n Since the 1970s a few dozen projects have sought to harness that heterogeneity. It\u2019s challenging because the temperature gap the technology aims to exploit is relatively narrow. Even in tropical zones most OTEC plants will have to make do with a 25 \u00b0C difference between the surface waters and the cold waters 1,000 meters below. (By contrast, conventional thermal generators function off of a 400 \u00b0C temperature spread.) <\/p>\n To harness the small temperature differential, most groups generate power by heating and cooling a working fluid that naturally boils at a low temperature, such as ammonia. Surface water is pumped into the plant and its heat is transferred to the ammonia, causing it to evaporate. That vapor then drives a turbine to generate power. Finally, to repeat the cycle, the ammonia\u2019s heat is transferred to cold water piped in from the deep, causing the ammonia to condense. <\/p>\n Squeezing power from a meager temperature delta requires a lot of surface and deep water. A 6.4-MW OTEC plant proposed on Taiwan\u2019s east coast by Taipei-based industrial conglomerate TCC Group Holdings<\/a> would suck up to 9,500 liters of cold seawater per second from 600 meters below the surface. A 10-MW design Lockheed envisioned for installation in China<\/a> in 2013 would have processed 40,000 liters of seawater per second, but it was never built. <\/p>\n Pumping on that scale favors placing plants on offshore platforms, which shortens the pipes required since they can extend straight down to reach lower depths. But offshore platforms increase costs, and operating in punishing open ocean conditions increases risk. When filled with water an offshore OTEC platform\u2019s dangling cold water pipe will weigh tens of thousands of metric tons, and any movement from rough seas will place immense stress on its connection to the platform.<\/p>\n To address one of the risks of being located off shore, London-based startup Global OTEC<\/a> deployed in the Canary Islands the world\u2019s first platform<\/a> purpose-built for OTEC and hurricane readiness. The platform, floated in April and paid for by government grants, is a 1:7-scale, non-working model of a 2.5-MW demonstration plant. <\/p>\n An operating plant will be required to convince investors of the technology\u2019s reliability. Jacobus, PA-based Sea Solar Power<\/a>, established in 1962 to pursue OTEC is designing a 25-MW plant that it vows would satisfy investors by paying for itself if its electricity serves an island grid reliant on expensive diesel<\/a> power. Sea Solar president Jim Anderson<\/a> says his firm survived to date thanks to revenues from its manufacturing spinoffs, but he says the company is now seeking a US $5\u201310 million investment to finish the plant\u2019s \u201cpre-feasibility\u201d engineering design. Building the plant would cost at least $120 million more.<\/p>\n Islands Seek Renewable Energy from OTEC<\/p>\n India\u2019s project in the Lakshadweep Archipelago aims to show that small OTEC plants can be reliable and cost-effective. The key is using simpler technology and producing more than power. <\/p>\n Rather than adding a cycle that evaporates and condenses a separate working fluid like ammonia, NIOT\u2019s plant will evaporate seawater at low temperature. To achieve that, pumps will create a vacuum, which lowers the atmospheric pressure around a liquid, decreasing its boiling point. This enables the Archipelago\u2019s approximately 29 \u00b0C surface water to evaporate more easily. That resulting \u2018steam\u2019 will then spin a low-pressure turbine<\/a> before it is condensed using 7 \u00b0C water. Then, instead of returning all of its condensed water back to the ocean, NIOT\u2019s plant will divert some of it to generate fresh water. <\/p>\n NIOT\u2019s technology emerged after a failed bid to go big in 2002. The Chennai-based government lab sought to demonstrate the world\u2019s first 1-MW OTEC process, 40 km off India\u2019s southeast coast. But during construction, workers dropped the project\u2019s 1,000-meter-long cold water pipe, losing it to the depths of the ocean. It was a confidence-shaking accident that Global OTEC founder and CEO Dan Grech<\/a> calls \u201cthe biggest mistake in OTEC history.\u201d<\/p>\n After the incident, NIOT pivoted, adapting its technology to address the needs of Lakshadweep. Like many island communities worldwide, the people of this archipelago rely on pricey imported diesel to generate electricity, and they face mounting water stress due to overdrawn aquifers and rising seas. NIOT initially addressed the drinking water crisis<\/a> with desalination<\/a> plants. <\/p>\n These plants use vacuums to evaporate hundreds of liters of warm surface water per second<\/a>, and condense the vapor to fresh water using deep sea cold water. The first plant started up in 2005 in Kavaratti, Lakshadweep\u2019s capital city, ending islanders\u2019 consumption of salty water. Doing so slashed rates of hypertension and gastrointestinal illness. \u201cThat was a moment of triumph for NIOT because nobody else had thought of doing this,\u201d says Jalihal, the project\u2019s former leader at NIOT. <\/p>\n But Lakshadweep\u2019s desalination plants still rely on the islands\u2019 expensive diesel-powered grids for electricity. So they\u2019ve turned to OTEC for power. NIOT\u2019s OTEC-enhanced desalination project, now under construction on Kavaratti, will use its low-pressure turbine to generate enough power to operate desalination grid-free. <\/p>\n It\u2019s not technology that will scale up, because the low-pressure turbines require much larger blades. But it could provide a small return on the 500 million rupee (US $5.3-million) installation, saving about 20\u201330 million rupees (US $210,000\u2013260,000) per year in annual diesel costs, according to one report<\/a>. <\/p>\n And the design could be replicated at many of the world\u2019s developing islands. NIOT has discussed sharing the technology with Maldives and Mauritius. That would be another small evolutionary step for OTEC. But, as Lakshadweep\u2019s experience shows, the local economic and health impact could be impressive. <\/p>\n From Your Site Articles<\/p>\n Related Articles Around the Web<\/p>\n","protected":false},"excerpt":{"rendered":"Construction underway on a remote island nearly 400 kilometers west of India\u2019s mainland could demonstrate, for the first…\n","protected":false},"author":2,"featured_media":622252,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[2885,246,61,60,211366,226663,264174,82],"class_list":["post-622251","post","type-post","status-publish","format-standard","has-post-thumbnail","category-environment","tag-climate-change","tag-environment","tag-ie","tag-ireland","tag-ocean-energy","tag-ocean-power","tag-otec","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/622251","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=622251"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/622251\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/622252"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=622251"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=622251"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=622251"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Schematic](\"https:\/\/spectrum.ieee.org\/media-library\/schematic-of-an-offshore-closed-cycle-otec-system.png?id=67744854&width=980\")
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