[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/13143\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EFrom sunlight to stored power: how hot air could solve solar energy\u2019s biggest challenge\u003C\/h2\u003E\u003Cp\u003EAs the world shifts toward renewable energy, one major challenge remains: efficient energy storage. An EU-funded research team is exploring the use of\u0026nbsp;compressed air\u0026nbsp;to store excess energy collected from solar panels.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EA pilot plant at Plataforma Solar de Almer\u00eda, a solar technology research centre in southern Spain, will demonstrate a concept they call solar thermal energy that will offer a sustainable and cost-effective alternative to traditional battery storage.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EBy capturing and storing thermal energy (heat), this innovative approach ensures that solar power can be accessed\u0026nbsp;even when the sun isn\u2019t shining, helping to stabilise the energy grid and accelerate Europe\u2019s transition to a clean energy future.\u0026nbsp;\u003C\/p\u003E\u003Ch2\u003EBalancing supply and demand\u0026nbsp;\u003C\/h2\u003E\u003Cp\u003EThe root of the issue, according to Professor David S\u00e1nchez, an expert in energy systems at the University of Seville in Spain, is that increasing the installed capacity of photovoltaic panels is not going to help provide energy at night or guarantee that electricity is available whenever it is needed.\u003C\/p\u003E\u003Cp\u003EIn theory, the sun provides ample energy. According to the Commission, solar power already contributes significantly to Europe\u2019s energy mix and, based on current market trends, has the potential to meet up to \u003Ca href=\u0022https:\/\/commission.europa.eu\/news\/focus-solar-energy-harnessing-power-sun-2022-09-13_en\u0022\u003E20%\u003C\/a\u003E of the EU\u2019s electricity demand by 2040.\u003C\/p\u003E\u003Cp\u003EBut solar panels generate electricity when there is least demand \u2013 in the middle of the day. Then, in the evening, when the sun has set, electricity demand peaks, but solar energy is not available.\u003C\/p\u003E\u003Cp\u003E\u201cRenewable energy is wasted because we don\u2019t have enough storage,\u201d said Fritz Zaversky, a research engineer at the National Renewable Energy Centre in Spain.\u0026nbsp;\u003C\/p\u003E\u003Ch2\u003EMechanical storage\u003C\/h2\u003E\u003Cp\u003EBoth Zaversky and S\u00e1nchez are part of a four-year EU-funded research initiative called ASTERIx-CAESar that is developing an innovative, high-efficiency solar thermal power plant which integrates two separate concepts: concentrated solar power and\u0026nbsp;compressed-air energy storage.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cCompressed-air storage is not a new concept and has been demonstrated already at commercial scale,\u201d said Zaversky.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003ECurrently, there are three compressed-air energy storage plants operating globally, in Germany, the US and China. Other sites are being explored and developed.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003ECompressed-air storage uses low-cost surplus electricity to compress air to a high pressure. This compressed air is stored and then used to drive turbines to generate electricity when power is needed.\u003C\/p\u003E\u003Cp\u003EUnlike batteries, these technologies do not rely on critical raw materials, for which there is competition from other battery-based technologies, like electric cars.\u003C\/p\u003E\u003Cp\u003EIf, on top of that, an underground storage reservoir such as a cavern or old mine can be used as storage, this further lowers costs, S\u00e1nchez explained. But there is a flaw.\u003C\/p\u003E\u003Ch2\u003EFossil flaw\u003C\/h2\u003E\u003Cp\u003ECompressed air cools during storage and needs to be heated before it can be used. Usually this is done using fossil fuels, which diminishes the eco-friendly credentials of the process.\u003C\/p\u003E\u003Cp\u003E\u201cThe concept is not carbon neutral because you burn natural gas,\u201d said Zaversky.\u003C\/p\u003E\u003Cp\u003ETo address this, the ASTERIx-CAESar team, comprised of energy experts and academics from eight EU countries, Switzerland and the UK, is looking to combine compressed air energy storage with another form of renewable energy known as concentrated solar power.\u003C\/p\u003E\u003Cp\u003E\u201cConcentrated solar power uses many mirrors to focus sunlight on one single spot, and this is usually at the top of a tower,\u201d said Zaversky.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003EOur approach is to use solar heat instead of natural gas, to make compressed-air energy storage carbon neutral.\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EFritz Zaversky, National Renewable Energy Centre, Spain\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EIn conventional concentrated solar power plants, the generated thermal energy is used to heat a liquid, usually molten salts, which then acts as thermal energy storage. When power is needed, the superheat from the liquid is used to create steam and drive a turbine to generate electricity.\u003C\/p\u003E\u003Cp\u003EHowever, according to Zaversky, conventional concentrated solar power plants are too expensive to be competitive against other renewables. The researchers are therefore proposing to combine the concentrated solar power technology with compressed-air energy storage, heating the compressed air with solar heat before expanding in the turbine.\u003C\/p\u003E\u003Cp\u003E\u201cOur approach is to use solar heat instead of natural gas, to make compressed-air energy storage carbon neutral,\u201d said Zaversky.\u003C\/p\u003E\u003Cp\u003EIn the system they are developing, low-cost renewable electricity is used to compress air for storage during the day, while concentrated solar power feeds a thermal energy storage system.\u003C\/p\u003E\u003Cp\u003EWhen energy demand is high, the thermal energy is used to heat the compressed air as it is released from storage to drive turbines.\u003C\/p\u003E\u003Ch2\u003EHigh temperatures\u003C\/h2\u003E\u003Cp\u003ES\u00e1nchez said the main challenge will be to develop technology able to convert concentrated solar energy into thermal energy at around 800\u00b0C and store it at such high temperatures.\u003C\/p\u003E\u003Cp\u003EThis is important, he explained, because it matches the temperatures used when burning natural gas. Also, higher temperatures increase the power output and efficiency of the process.\u003C\/p\u003E\u003Cp\u003EThe pilot plant in Spain will put these ideas into action. They will be upgrading a concentrated solar power tower already in place by adding compressed air energy storage, using high-pressure storage tanks, to create the hybrid system.\u003C\/p\u003E\u003Cp\u003EThe team aims to demonstrate that their hybrid concept works on a small scale. After that, Zaversky believes it will be necessary to develop an intermediate-scale demonstration plant. If that proves successful, the technology could start being used.\u0026nbsp;\u003C\/p\u003E\u003Ch2\u003ESolar efficiency\u003C\/h2\u003E\u003Cp\u003ETheir goal is to build a highly efficient solar thermal power plant that can ensure 24\/7 availability of renewable energy. Because it will have enough storage capacity, it will be able to offer much-needed grid stability and help support the uptake of renewable energy.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EThe solar-to-electric energy efficiency conversion of this system is predicted to be around 40%, or double that of today\u2019s commercially available solar panels, which achieve 15 to 24% efficiency.\u003C\/p\u003E\u003Cp\u003EAccording to Zaversky, there are several sites in Europe where this concept could operate, especially in southern European countries such as France, Greece, Italy and Spain.\u003C\/p\u003E\u003Cp\u003E\u201cThe Greek islands are particularly favourable, because they have high solar energy available and there are locations where compressed air could be stored underground.\u201d\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EResearch in this article was funded by the EU\u2019s Horizon Programme. The views of the interviewees don\u2019t necessarily reflect those of the European Commission. 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