Engineering News and Mining Weekly
Heat pump saves manufacturer’s site 169 MWh/y
According to a recent press release from “forward-looking” machinery developer Ecoclean, premium car manufacturer BMW has replaced its electric water heating system with a heat pump at its Steyr site, in Austria.
This has resulted in electricity savings of about 70% a year in that process and contributes to improving energy efficiency and mitigating some of the climate-related concerns that plague the automotive industry.
The optimisation of production lines and machinery for the manufacturing of core engine components like crankshafts and crankcases, cylinder heads and housings for the latest generation of electric drives has been on the agenda of BMW Group’s Steyr site for several years. This also includes the cleaning machines for these components.
“To reduce energy consumption, we started with Ecoclean to equip the pumps of cleaning machines with variable-frequency drives in 2016,” explains BMW Steyr site’s process and energy manager Gerhard Fuchs.
In the search for additional ways to save energy it was determined, through consumption measurements, that the electrical heating systems of the cleaning machines running in three-shift operation elevated consumption. Considerations on how energy could be saved in hot water generation resulted in the use of a heat pump.
“I wanted to implement a pilot project to determine the energy savings potential we could achieve by replacing the previous electric heating system [with] a heat pump. [Owing] to the excellent cooperation we have had with Ecoclean, I asked the company whether they would join us as general contractor. After they agreed, we chose a transfer cleaning machine from the manufacturer,” says Fuchs.
Potential Analysis
Firstly, to calculate the energy savings achievable by integrating a heat pump, a potential analysis was conducted. The basis for the analysis was the production, process and system data, previous energy consumption figures, and the modification concept prepared by Ecoclean.
To ensure neutrality, an independent engineering office was hired for the analysis. This independent office calculated savings of about 70%, compared with previous energy consumption.
The solution is tailored exactly to the situation at BMW Steyr. On the roof of the transfer system there is a tank holding 2 000 ℓ of clean water that is supplied to the cleaning process at 56 °C. The required electrical heating system had a power draw of 39 kW.
Cooling of the vacuum pumps and control cabinet was affected by a cold-water circuit. Cooling water is provided at a supply temperature of 16 °C and returns at a temperature of 22 °C.
This ‘warm water’ serves as an energy source and is supplied to the heat pump (power draw 11.2 kW) where it is heated to 65 °C.
The heat transfer to the hot water supply of the cleaning machine is affected by a plate heat exchanger. A new circulating pump (power draw 1.2 kW) delivers the heated process water to the hot water tank of the cleaning machine while a second, new circulating pump (also with 1.2 kW power draw) returns the water that has been cooled to 16 °C to the cold-water circuit.
This well-thought-out solution reduces the energy consumption from 39 kW to 13.6 kW. With a defined production time of 5 760 hours a year, this adds up to more than 146 MWh. Further, another 23 MWh are saved in cold water generation since the cooling water now needs to be cooled down from a much lower return temperature.
Uninterrupted Quick Modification Production,
As the project was to be implemented without interrupting production operations, the modification job was carried out during a two-week holiday.
The heat pump, plate heat exchanger and the two new circulating pumps were installed on the shop floor near the machine, insulated and surrounded with fencing.
The surface area required corresponded roughly to the size of two European pallets. In addition, the modification required four new pipes.
Two of them connect the clean water tank on the machine to the plate heat exchanger.
The two other pipes transport the warm water from the cooling circuit to the heat pump and return it after cooling. Ecoclean also integrated a display for temperature and flow monitoring, which comprises an energy monitoring system that includes an energy meter to verify the saved heating power.
This monitoring – as well as measurements made by the independent office after project completion – shows that 100% of the predicted savings have been achieved. Owing to the current saved total of 169 MWh, the yearly operating costs for cleaning have been reduced by some €19 000.
In addition, significantly fewer carbon dioxide (CO2) emissions are emitted into the environment. In this case, the savings amount to about 34 t of CO2.
“It has been a good decision to involve Ecoclean as prime contractor for energy-efficient projects. We are very happy with the results and their support, and will continue our cooperation,” concludes Fuchs.