[Case study] Fordia – Energy efficiency and energy savings opportunities in industry
Like many players in today’s society, industry stakeholders are taking concrete action to reduce energy consumption and reduce their impact on climate change. Fordia is focusing on drastically reducing its global carbon emissions and has launched a global Energy Efficiency program on all of its operations combined with a green energy program.
In this regard, TERAO carried out a first energy audit (see interview from Gaëtan Grand from Fordia about this mission) in 2021 focusing on the energy consumption analysis and the energy optimization of the building part of the factory, including the envelope and the systems. In 2022, TERAO conducted a second audit focusing on the process and its interaction with the building.
This was done using advanced modeling tools able to model the behavior of the building:
- Energy modeling, and
- CFD (Computational Fluid Dynamic),
The main topics covered by the second audit were HVAC, workshop geometry optimization, oven, and waste heat recovery.
Workshop geometry optimization
The industrial sector is quite diverse and standard solutions are usually not adapted. It is therefore not as simple to design air conditioning for a workshop in comparison with an office or a residential building.
In a workshop, the thermal impact of the process needs to be taken into consideration as it will have a major impact on comfort, air conditioning, and heating. Therefore, analyzing thermal load intensity and location is key to defining the thermal zoning, workshop geometry, and appropriate HVAC system for each zone.
In the case of Fordia’s workshop, one area with a high thermal load was identified to have an impact on the overall AC consumption. This area was open in the workshop and was containing gas and hydrogen/electrical ovens. Each system was generating a high intermittent thermal load varying along the stage of the cooking cycle.
To enhance natural ventilation via the stack effect it is however recommended to design the natural ventilation. Through the combination of CFD and Energy/thermal modeling, TERAO specified the following approach:
- Design of the isolation room (shape, size, type of partitions): The height of the room should be as high as possible and the depth as low as possible. Indeed, the greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect.
- Air inlets and outlets specification (type, size, position, distance). To increase the stack effect the distance between the outlet and inlet should be as high as possible. A comparison of the volume air change according to the distance between openings is given in the graph below as a reference:
- Settings of the inlet and outlet in different seasons and for different process operating modes. In Changzhou the climate is variable and the processing load is intermittent, adjustable louvers will be necessary to ensure good thermal conditions,
Workshops are usually large spaces, which means that the area to be conditioned is also quite voluminous and will involve high consumption of the HVAC system to maintain a decent temperature in the whole volume throughout the year.
Knowing that, it is important to analyze why air conditioning is needed in the workshop: is it for the product/manufacturing process or for the thermal comfort of the occupant?
In this regard, a system such as an adiabatic air conditioning system is usually energy efficient and will be dedicated to providing the right level of comfort to the operators instead of maintaining the room at a certain temperature. Adiabatic AHU is a system that cools down the air by spraying water on the air without the use of a cooling system, bringing air into contact with water allows the water to evaporate and lower the temperature of the air.
With such a system, the blowing temperature being most of the time around 23.5°C by 35°C outside, it is possible to maintain a measured temperature of 28°C corresponding to a feeling of 26°C for an air displacement of 1m/s. As with such a system the temperature cannot decrease as low as a typical AC system, the comfort is maintained by increasing the air speed near the operator. An outside temperature sensor can be added to switch from adiabatic mode (water circulation pump on) to free cooling mode (ventilation only).
Gas heat treatment furnace – energy efficiency high-level review
Fordia has one gas heat treatment furnace that is accounting for 43% of the total energy consumption. An analysis focusing on this existing furnace accompanied by an on-site thermographic measurement was done. This analysis led to a recommendation list aiming at reducing energy consumption and improving thermal comfort in the workshop. Some of the suggestions are described below:
- Enhanced temperature control via the installation of a ramp soak temperature control on the furnace enables to create the different heating scenarios for different products,
- The heat exchanger on the exhaust air of the furnace preheats the combustion air of the burner,
- Preheating the cooling chamber via the exhaust of the furnace to reduce the heat load emitted in the workshop and its impact on cooling and thermal comfort
- Switching from Natural gas to Biogas to reduce CO2 emissions. The graph below is shown the CO2 impact of different energy sources:
- Adding a second layer of product in the oven to maximize the number of products cooked in one cycle,
Through this very specific energy audit, TERAO was able to advise the customer on the envelope, HVAC and process systems. The audit results in a list of recommendations including % of energy savings and implantation details to facilitate customer decision making.
Written by Thomas Krysinski
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