Chillers make hot summers more bearable. But they could also make energy systems more flexible throughout the year. And this is extremely important at a time when renewable energies are growing. Siemens experts in Berlin are looking at how they can optimize the cooling supply of Germany’s largest scientific center and trying to determine the hidden potential of chillers in combination with thermal energy storage systems.
by Ulrich Kreutzer
When summer temperatures soar, we often forget that air-conditioners not only cool the air but are also energy guzzlers. They consume a tremendous amount of energy annually. As explained in a recent study by the International Energy Agency (IEA), air-conditioners today account for 10 percent of the world’s energy consumption. According to projections, the number of air-conditioners could triple by the year 2050.
That’s why optimizing the operation of chillers – which are a component of air-conditioners – plays a key role. Their optimal operation is even more important in a world that’s increasingly dependent on renewable energies. Because wind and solar energy fluctuate – meaning that they’re irregularly generated – they require a flexible energy system. This is precisely where electrically operated chillers could be of service – if they’re combined with thermal energy storage systems.
Researchers from the Siemens' central research and development unit Corporate Technology in Berlin have been showing how this works since spring 2018. In a BMWi (German Federal Ministry for Economic Affairs and Technology) research project, they’re collaborating with partners at the Technical University of Berlin, RWTH Aachen University, and Zuse Institute Berlin to optimize the cooling supply at the Berlin-Adlershof Technology Park, Germany’s largest scientific center. The project is part of the “Energy Strategy Berlin Adlershof 2020” initiative, which is aimed at reducing the site’s primary energy requirement by a total of 30 percent by 2020.
The project focuses on six chillers and a thermal energy storage system, known as an ice storage system, that provide the necessary cooling for offices and laboratories occupying an area of nearly 20,000 square meters. The cold generated serves three purposes: It regulates room air, cools machines, and is used for process cooling, for example for manufacturing semiconductors on site.
“Until now, the on-site chillers have operated extremely inefficiently,” says Stefan Langemeyer, project manager at Corporate Technology. The six systems, each with an output of between 600 and 800 kilowatts, are generally operated according to current load requirements. That’s why the chiller units often operate within a low and therefore inefficient load range. “We’re developing a fully automated energy management system to control the chillers more efficiently,” explains Langemeyer. The goal is to reliably provide the necessary cooling at the lowest possible cost and with the smallest possible carbon footprint.
“In terms of the energy management system, we have to take into account complex dependencies and interactions,” explains Langemeyer. Ideal chiller operation depends on the outdoor temperature, because the colder it is outdoors, the lower the energy requirements. Of course, it’s also best to operate them when energy prices are low. That’s why the experts’ energy management system also takes into account the times of day and year that are most favorable for generating cold and coordinates this with the site’s requirements.
But times of peak demand don’t necessarily coincide with times when energy prices and outside temperatures are low. This is where the ice storage system comes into play in order to enable load shifting. Whenever cooling isn’t required, it stores the cold in the form of ice so that it can be supplied at times of high demand. And it does so extremely efficiently: The losses from standstill are about 0.02% per hour.
Current investigations are based on the results of the research project “EnEff: Stadt Energienetz Berlin Adlershof,” which the experts completed in 2018. At that time, the focus was on making the cooling grid more flexible and expanding the metering infrastructure, meaning energy meters and chilled water heat meters that can track the operation of the individual cooling circuits. At the core is the cloud-based “Navigator,” a data acquisition tool provided by Siemens colleagues at Building Technologies. It measures various temperatures, electrical outputs, and the overall system’s cooling capacity. “This data helps us to identify the measures we need to take to optimally operate the cooling grid,” says Langemeyer. The results are also extremely interesting for colleagues at Building Technologies. “They provide us with important clues about how we’ll be able to integrate this technology into our building automation portfolio,” explains Bruno Illi at Building Technologies.
Why did the researchers specifically select the Adlershof site? “The overall package suits our investigations,” says Langemeyer. The campus is large enough, provides the cooling necessary for various purposes, and has an ice storage system for load shifting. “Under these circumstances, intelligent energy management is especially attractive.” In this way, energy savings of up to 15 percent can be realistically achieved. The Adlershof site serves as a pilot project. In the future, the scientists want to apply the research findings to other buildings. Thus, the science and technology center is also a real-life laboratory for the energy transition. Initial findings will be available in 2019.
Picture credits: from top: picture 1: Getty Images
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