One biproduct of all industrial processes, from aluminium production to cooling for data processing centres, is thermal energy – in other words, excess heat. This is energy that is rarely utilised. At the same time, we know that thermal energy comprises half of the global energy needs. In other words, capturing and using excess heat has enormous potential for industry.
At SINTEF, we have a leading research community as well as laboratories, which help customers around the whole world to find and develop solutions for using excess heat or “waste heat” as it is also called. The challenge for our customers is often developing technologies and solutions that both work sufficiently for the purpose and are cost-effective enough that capturing and using excess heat is profitable. Enabling heat to be utilised at as high a temperature as possible is an important premise for increasing efficiency.
SINTEF has extensive experimental and numerical expertise in all of the important areas within the development of technology for use and upgrading of excess heat: from developing technology and modelling components and processes to experimental activities and industrial implementation.
Heat capture technologies
Once we have managed to capture the excess heat, we can do a lot with it. For example, it can be reused in the industrial process or used for central heating. At SINTEF, we are researching how business parks or other places where energy-intensive industries are clustered together can share excess heat so that actors that need thermal energy can buy it from other actors that have a surplus. A third alternative is to use the energy to heat nearby homes, in the same way as district heating receives heat from waste incineration.
Many processes require heat at specific temperatures, which means the captured excess heat cannot necessarily be reused directly. In these cases, the excess heat can, for example, be transferred by a heat pump and upgraded to process heat. This considerably reduces the energy required to create process heat.
We are also investigating how the use of CO2 can contribute to reducing the greenhouse gas emissions from these heat pumps. Yes, you read that correctly. CO2 as a cooling medium can actually contribute to limiting 0.5 degrees of global warming. Find out more about how this works in the video.
Thermal energy storage
Sometimes we need to store heat instead of using it as soon as it is caught. This is called thermal storage. At SINTEF, we are working with storing thermal energy at low temperatures using, for example, phase changing materials (PCM), at medium temperatures using accumulator tanks and energy wells, and at high temperatures using steam.
An example of how thermal energy storage can be used is the Nidar factory at Leangen in Trondheim. The factory has a steam need of just over 3 MW, which is currently met with a propane boiler. Orkla/Nidar aims to make steam production fossil free by swapping to an electric boiler, but this is not yet feasible due to the limited capacity of the power grid in the area and around the factory, which will take many years to expand. We will now investigate whether combining the boiler with thermal storage in the form of a steam accumulator can contribute to evening out the loads in the power grid and reduce peak power, thereby facilitating fossil-free steam production in the plant.
Converting excess heat into electricity
The laws of nature dictate that reusing heat has a higher efficiency (less loss) than the conversion of heat into electricity. That is not to say that converting heat into electricity cannot be profitable. Electricity has the significant advantages of flexible distribution and universal demand. In Norway, energy-intensive industries are often not located close together, which makes it difficult to transfer heat efficiently between them. Therefore, there are more gains to be had from converting the heat energy into electricity than not using the energy at all.