Environmentally friendly cooling using groundwater
Since October 2019 Buchs has been using groundwater to assist cooling processes in Production and to cool the buildings in summer. The project shows considerable signs of ecological and economic success.
The mobile drill is in position, the mini drill rig has been constructed: the test drill for groundwater can begin.
This absorption refrigerator works like an ordinary refrigerator. The system cools district heating steam to cool the production building. The intention is that in future cooling will come direct from groundwater.
The photos show sections of Mibelle Group’s ice water system: the left-hand photo shows one of the three vapour compression refrigerators. The right-hand photo shows the free-cooling system (left) and the cooling tower (right). Here cooling is achieved with cold water and used in production as “process cooling”.
The diagram shows the cooling process, from drawing to infiltration of the groundwater.
Drilling the infiltration wells to return the groundwater to the earth.
Drilling work for the three extraction wells. One well is being constructed for air conditioning, the other two are for process cooling.
Most of the 600 metres of new pipes have been laid across the roof and connected.
Checking the groundwater network's system pressure and pressure maintenance at the hydraulic separator, before the groundwater is distributed to the absorbing wells.
Maintenance work to the ultra-pure water treatment plant's membrane vent system.
Test drills in autumn 2017 saw the launch of a completely new Mibelle Group project with great ecological potential – refrigeration provided by groundwater. The pumping tests delivered the hoped-for results. There was sufficient groundwater in the borehole and the groundwater level did not fall during pumping – two important project requirements. There were therefore no further obstacles to implementation of this major project, requiring an investment of CHF 1.3 million.
Cooling requires a lot of energy
Why does the Mibelle Group need refrigeration at Buchs? Thomas Aliverti, head of Infrastructure, Energy & Construction explains the context: “In Production we heat products to make them smoother and easier to process. Most products are then cooled down again. And then there are the buildings. We don’t have an air-conditioning system, but we need to cool the rooms so they don’t overheat. The refrigerators consume big amounts of electricity and steam.”
Until recently the energy for refrigeration was obtained from conventional electricity. Savings produce clear improvements in the carbon footprint. Since 2010 the Mibelle Group in Buchs has reduced electricity consumption by 21% and heat consumption (steam) by 34%, with reference to the volume produced.
Groundwater cooling can play an important role in energy saving. Cooling operates safely and uses almost no electricity - in other words it is extremely efficient. It is also important that the project should not harm nature and the environment, which is ensured by strict regulations applied by the canton of Aargau, Switzerland. According to Aliverti: “We draw the groundwater from the ground at around 12 degrees and must return it at a temperature only slightly higher, up to a maximum of 5 degrees. The groundwater temperature can rise by a maximum of 3 degrees within a radius of 100 metres.”
Groundwater can cool, heat and also be used as a raw material in products
A total of three extraction wells were sunk in spring 2019; one for air conditioning and two for process cooling. Another five infiltration wells were built for return. Groundwater use was commissioned in autumn 2019 and the existing ice water system and absorption refrigeration system decommissioned. Thomas Aliverti is delighted that “900 litres of groundwater are flowing out of each well per minute. This means we have been able to save 615,000 kWh and 1,100,000 kWh steam, which is around 10% of our total electricity and steam consumption.”
How will the groundwater be used?
After cooling the groundwater will be returned direct to the ground.
Theoretically it would be possible for slightly heated groundwater to
flow through a heat pump to regain the heat and to use this for heating
during the winter. As the Mibelle Group obtains its heating in Buchs
from the adjacent domestic refuse incinerator, it is not worth it.
Groundwater use will, however, be taken to another level. Part of the
groundwater is discharged, the remaining groundwater is converted into
ultra-pure water, which is used in the production of creams and lotions.
The water quality remains absolutely homogeneous. Ultimately, the
groundwater for cooling and Mibelle Group’s drinking water comes from
the same groundwater source.
The Mibelle Group has been assisted with its groundwater project by engineers from Migros Engineering Solutions. Thomas Aliverti sums it up by saying that “The exchange of experience and knowledge was extremely valuable, as the project is also a beacon project for the whole of M Industry.”
Facts about groundwater cooling at Mibelle Group:
- 100% of cooling in Production and cooling buildings is from groundwater. As a result, the Mibelle Group is saving around 10% of the electricity and steam, corresponding to around 615,000 kWh electricity and 1,100,000 kWh steam.
- This should also contribute to Migros’ climate and energy strategy. Since 2010 the Mibelle Group has achieved a 21% reduction in electricity consumption and 34% reduction in heat consumption (steam).
- It also backs up M Industry’s long-term vision of reducing the electricity consumption and specific heat consumption of M Industry as a whole by 25% by 2040.
Water & soil