Using hot exhaust air to drive down heating costs

Many production halls are air conditioned all year round to ensure constant working and manufacturing conditions. Ventilation systems generally extract the waste heat given off by manufacturing processes and release it into the outside atmosphere. In the fall and winter, factory halls frequently also have to be heated. With a new type of solution, the company Hoval offers systems capable of recovering process waste heat, cutting factory heating bills for one of its customers by up to 88 percent. Hoval relies on automation technology from the Siemens Industry Automation Division in its systems.The ambient temperature of a production hall is held at a comfortable 20 degrees Celsius – not just for the benefit of staff but of the machines too. This is the only way to prevent uncontrolled metal expansion and so ensure adherence to tolerances. In winter, the energy needed to heat the fresh air in the factory hall is a significant cost factor.The company Hoval based in Liechtenstein has developed an oil-tight plate heat exchanger whose function is to recover waste process heat, and which has been specifically designed to work with exhaust air laden with dirt and oil particles as well as aerosols from industrial processes. The thermal energy in the exhaust air heats the cold fresh air by means of the heat exchanger, so improving the energy efficiency of the entire ventilation system. To control the heat exchanger and system, Hoval has opted to use Simatic ET 200S distributed I/O control technology. The control is integrated in the production automation system, and exchanges data with the building management system in order to maximize convergence and save costs.Used at the company Aesculap in Tuttlingen, Southern Germany, the system meant an 88 percent saving in terms of fresh air heating costs. Aesculap saw its initial investment fully recouped in just three years.The Swiss company Wito in Weinfelden took responsibility for programming, making use of the Engineering Framework TIA Portal from the Siemens Industry Automation Division: For instance for communication between the Comfort Panel TP700 operating element and ET 200S, and for adaptation to the customer’s IT network. The time required for commissioning was cut by performing the entire function testing process in advance in the office using the Simit simulation system. 02.10.2013, Siemens AG, Industry Sector