Researchers from Qatar University and Jordan’s Hussein Technical University have found a way to double the power produced from a type of solar tower. The “twin technology solar system” they report in the journal Energy Reports can produce energy all day and all night.
Solar panels, which absorb light and turn it into electricity using photovoltaic materials, are a conventional, well-known technology to harvest the sun’s energy. The concept behind the new solar tower system is very different. It relies on the fact that hot air rises.
Such solar updraft towers are typically made from glass or other greenhouse materials that trap heat. The air is heated at ground level and as it rises up the tall tower, it spins a turbine to produce electricity. But the idea remains experimental. Costs of building the large, tall glass towers remains prohibitive for mainstream use.
The new twin-technology tower could bring down cost by producing over twice as much power as previous designs, say the researchers. Their design entails building a secondary tower around the inner tower.
The second tower is a cooling tower, in which air would be sent downward to spin another turbine. To accomplish this, the researchers propose spraying a fine mist of water into the hot air that reaches the top of the tower, making it cooler and sending it downward.
In the paper, the researchers present details of a model tower structure that is 200 meters tall, with an inner updraft heating tower that is 10 meters in diameter. The outer downdraft cooling tower’s diameter is 13.6 meters. The gap between the towers is separated into 10 channels, each serving as a cooling tower, with water misting systems at the top and turbines at the bottom.
Using simulations of the tower combined with local weather data, the team estimated that it would generate a total of about 753 megawatt-hours of energy annually. That is about 2.14 times the power of a traditional solar updraft tower. The external cooling towers would produce about 400 megawatt-hours, and the inner heating tower working better during the day under the hot sun to generate around 350 MWh.
The researchers found that seasonal variations in temperature and humidity affected the external tower more, so its output power swung widely throughout the year. Its performance decreases significantly in high humidity, they say, so it is best used in areas with hot and dry weather. They tested their simulation in Riyadh City, which is a hot, dry desert climate, and the results show that the system could be beneficial to deploy there.
“However, the system has limitations, such as access to water for the operation of the downdraft system,” the team writes. They plan to work on a deep techno-economic analysis of the proposed system and a take a closer look at its scalability.
Source: Emad Abdelsalam, Fares Almomani and Shadwa Ibrahim. An innovative twin-technology solar system design for electricity production. Energy Reports, 2024.
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