Concentrated Solar Works Day and Night With No Batteries Required
By Paul Brown
The massive expansion of solar panels on rooftops and solar farms across the world has captured the headlines, but the other established way of generating electricity from sunlight—concentrated solar power (CSP), or solar tower power—is also making great strides.
For a long time, using mirrors to concentrate the sun's rays to heat molten salt and produce superheated steam to drive a generator's turbines was thought to be a more promising technology than photovoltaic panels (PV), because it was originally cheaper.
But as the price of the panels has dropped dramatically in the last five years, CSP fell out of favor, although some countries continued to support its development.
Now the cost of CSP is also falling. But it has another major advantage: unlike the panels, it can go on producing power long after the sun has set, and can store it for up to 15 hours, for use when it's needed.
Dubai, the largest city in the United Arab Emirates, where sunshine is almost guaranteed, is a fan of both solar technologies. It has just announced that electricity from a proposed 200 megawatt CSP project, to be completed in 2021, will be priced at 9.45 cents per kilowatt hour—40 percent below the previous world record.
The cost is well above the three cents per kilowatt hour of the cheapest solar PV, but has the advantage of running for 15 hours at full power during the night, doing away with the need for any fossil fuels for back-up generation.
CSP has many variations, all ways of concentrating solar power onto liquid to heat it and so create steam for driving turbines. The two main types use parabolic troughs or mirrors to aim the sunlight at a central tower. Troughs have been more widely used so far, but towers are gaining fast—the latest scheme, Dubai's, uses a tower.
Current technology for storage uses sodium nitrate and potassium nitrate together heated to 566°C to store the heat in a large tank until it is needed. It is then fed gradually through a heat exchanger to produce superheated steam for the turbines.
Dubai Electricity and Water Authority (Dewa) has ambitious plans to reach 1000 megawatts of CSP as part of plans to boost capacity for its solar park from 1,000 MW by 2020 to 5,000 MW by 2030. The first 13 MW of PV came on line in 2013. The city aims to have seven percent of clean energy by 2020, 25 percent by 2030 and 75 percent by 2050.
There were a number of bids for Dubai's CSP projects. Consortiums included Saudi Arabia's Acwa Power and China's Shanghai Electric, followed by the Abu Dhabi clean energy company Masdar, with partners EDF of France and Abengoa of Spain.
Saeed Al Tayer, the managing director and chief executive of Dewa, claimed: "The UAE's focus on renewable energy generation has led to a drop in prices worldwide and has lowered the price of solar and wind power bids in Europe and the Middle East."
Paddy Padmanathan, chief executive of Acwa Power, said it was exciting to see CSP technology with storage "offering dispatchable solar energy—day and night, competing with fossil fuel-based alternatives." Several of the companies involved said they would continue to compete for future projects.
The U.S. was one of the pioneers of CSP, and many sunny countries in the Middle East and Africa are now developing projects, including South Africa, but, as with many other renewable projects, China is hoping to take a lead.
China plans to build 1.3 GW of CSP capacity by 2018 in a first batch of 20 CSP projects which includes nine solar towers, seven parabolic trough plants and four linear Fresnel plants (using a form of lens which also concentrates solar power).
So far, the Chinese have yet to decide which is the most promising technology.
Reposted with permission from our media associate Climate News Network.
At first glance, you wouldn't think avocados and almonds could harm bees; but a closer look at how these popular crops are produced reveals their potentially detrimental effect on pollinators.
Migratory beekeeping involves trucking millions of bees across the U.S. to pollinate different crops, including avocados and almonds. Timothy Paule II / Pexels / CC0<p>According to <a href="https://www.fromthegrapevine.com/israeli-kitchen/beekeeping-how-to-keep-bees" target="_blank">From the Grapevine</a>, American avocados also fully depend on bees' pollination to produce fruit, so farmers have turned to migratory beekeeping as well to fill the void left by wild populations.</p><p>U.S. farmers have become reliant upon the practice, but migratory beekeeping has been called exploitative and harmful to bees. <a href="https://www.cnn.com/2019/05/10/health/avocado-almond-vegan-partner/index.html" target="_blank">CNN</a> reported that commercial beekeeping may injure or kill bees and that transporting them to pollinate crops appears to negatively affect their health and lifespan. Because the honeybees are forced to gather pollen and nectar from a single, monoculture crop — the one they've been brought in to pollinate — they are deprived of their normal diet, which is more diverse and nourishing as it's comprised of a variety of pollens and nectars, Scientific American reported.</p><p>Scientific American added how getting shuttled from crop to crop and field to field across the country boomerangs the bees between feast and famine, especially once the blooms they were brought in to fertilize end.</p><p>Plus, the artificial mass influx of bees guarantees spreading viruses, mites and fungi between the insects as they collide in midair and crawl over each other in their hives, Scientific American reported. According to CNN, some researchers argue that this explains why so many bees die each winter, and even why entire hives suddenly die off in a phenomenon called colony collapse disorder.</p>
Avocado and almond crops depend on bees for proper pollination. FRANK MERIÑO / Pexels / CC0<p>Salazar and other Columbian beekeepers described "scooping up piles of dead bees" year after year since the avocado and citrus booms began, according to Phys.org. Many have opted to salvage what partial colonies survive and move away from agricultural areas.</p><p>The future of pollinators and the crops they help create is uncertain. According to the United Nations, nearly half of insect pollinators, particularly bees and butterflies, risk global extinction, Phys.org reported. Their decline already has cascading consequences for the economy and beyond. Roughly 1.4 billion jobs and three-quarters of all crops around the world depend on bees and other pollinators for free fertilization services worth billions of dollars, Phys.org noted. Losing wild and native bees could <a href="https://www.ecowatch.com/wild-bees-crop-shortage-2646849232.html" target="_self">trigger food security issues</a>.</p><p>Salazar, the beekeeper, warned Phys.org, "The bee is a bioindicator. If bees are dying, what other insects beneficial to the environment... are dying?"</p>
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