Thermodynamic solar power is being considered for multiple sites around the world following a successful trial of the technology outside Seville in Spain. The plant reliably produces 400MWh of clean energy per day regardless of weather conditions, thanks in part to a Movicon 11 SCADA control system.
Solar panels have been a dependable energy source for decades. But to date they have tended to be confined to smaller applications in Europe, typically supplying only their local area and usually backed up by another power source in case the sun does not shine. Engineers and scientists have spent many years trying to develop solar technology to overcome this scaling restriction so that grid-scale quantities of power can be generated for wide distribution to a significant population of domestic and commercial users.
Now they are in the final stages of perfecting a reconfiguration of existing solar technology, known as thermodynamic solar power, that has the potential for large scale energy production through the day and also long after the sun has gone down. An energy plant in Seville, Spain has, with the help of a Movicon 11 control system, proved that this technology is practical and reliable
In the semi-arid Seville region of southern Spain, the new solar facility is now supplying power to 25,000 homes, businesses, schools and other energy users. The thermodynamic technology works like this: a massive array of over 2600 large mirrors redirect the sun’s rays toward a 150m (450ft) tall tower which is filled with salt.
The energy provided by all this sunlight melts the salt (a mixture of 60% potassium and 40% sodium nitrate) and superheats it to over 500°C. This is used to produce steam, which in turn drives a turbine that is connected to a generator producing 400MWh of electricity for distribution to homes and businesses. The mirrors can move individually or en-masse to track the sun on its daily journey across the sky or for fine adjustment of the energy directed towards the salt tower.
Thermodynamic solar power has several advantages over other solar solutions, the most important being that this technology can continue to generate electricity for up to seven hours after sunset. This is possible because of the incredible heat build-up in the salt mixture. Significantly the thermodynamic system works in cloudy weather, so is able to produce power throughout the year in many locations around the world.
A key to the efficient operation of the Seville thermodynamic power plant is being able to closely regulate the temperature in the tower tank and in the turbine. The Seville managers also wanted a control system that had simple to follow graphic read-outs. For these vital supervisory and control functions, they selected Movicon11 SCADA technology.
The first challenge for the control engineers at the Seville power plant station was to figure out how to get highly accurate temperature measurements from multiple locations within the salt tower. This was accomplished by installing heat-resistant thermal imaging cameras on steel poles around the tower and linking them through a fibre optic Ethernet network to the Movicon SCADA system.
Each camera is configured to measure maximum, minimum and average temperatures. These measurements are processed by Movicon data-logging software and displayed in the Movicon Trend and Historical screen pages. All thermal image data are collected in real time by Movicon SCADA software in the control room, from where operating staff can monitor the readings and if necessary adjust the control system accordingly.
If there is a problem or need to change the temperature, this information is sent to a PLC which relays it to the mirror control system. Then, the mirrors can be quickly moved to redirect the reflected sunlight, increasing or decreasing the energy delivered to the tower. The Movicon system also produces trending information from recorded temperatures and provides options for setting adjustments so that power production can be optimised.
The supervision and control provided by the Movicon system has helped make the Seville power plant a highly reliable and safe facility with a simple to use control room. It has also proved the concept of thermodynamic solar power production, which should lead to similar installations around the world.
Movicon is a leading SCADA (supervisory control and data acquisition) system – used in many industrial installations around the world. As well as power plants it can be found controlling, utilities, oil and gas production, water works, manufacturing and processing plants, food and pharmaceutical plants and in building automation. It is made by Progea in Italy and available in the UK through Sutton Coldfield based Products4Automation.
