Mark Venables reports on how OEMs are controlling their energy use throughout the manufacturing process using a combination of increased visualisation and energy efficient equipment
OEMs have been trying to reduce the input costs of energy by generating their own through co-generation plants, solar panels and wind turbines. This generation drive shows no sign of abating but attention is now increasingly focused on energy management within the production process, with added scrutiny on energy intensive locations such as foundries and paintshops.
“We would typically look at an entire facility, we don’t care whether it is the building energy or the process energy – wherever the biggest advantages are we tackle it,” explains GM’s global energy manager, Al Hildreth. “One of the key differences is that nowadays energy management is really integrated into our business plan. We treat energy, safety and production quality equally because they all cost the business. That gives our whole approach a leg up because it means that this programme isn’t the ‘flavour of the day’ – it is not a separate project. So once we have set the goals and the plants have their targets, they are out there looking for whatever energy efficiency or conservation projects they can find. “We look at the process energy angle as one of the biggest targets for us because it takes about 60% of our energy. So when we are looking at energy efficiency projects we tackle all of them, but our focus is on production energy.” Like most automakers, GM considers energy consumption per vehicle at its vehicle plants or energy per engine at its engine plants as standard measurement metrics. The actual figure is dependent on the range of functions handled at each plant; those with their own bodywork shops, foundries and stamping shops will obviously use more energy than simple assembly plants.
Advanced controls, automation systems and sensors have been used to improve industrial process control and energy efficiency for years. However, within the context of energy management, industrial automation, advanced controls and sensors, and information technology assets offer even more significant energy-saving potential.
Industrial process optimisation depends heavily on data, which is used to drive decision making in all parts of a plant – whether its production scheduling, equipment maintenance or energy consumption. Because industrial sensors and wireless controls provide real-time data feeds to manufacturing plants, data-enabled automation systems can make energy use more visible in real-time, which can potentially lead to continuous improvement of energy use in manufacturing plants and data centres.
“The next big evolution we see in energy management is the convergence of energy infrastructure and information technology,” says Paul Hamilton, vice-president at Schneider Electric. “As technologies become more sophisticated and data collection of energy use becomes more consistent, decision makers in a plant can use the data to use energy more efficiently and facilitate persistence of energy savings.” However, as with monitoring systems on any production line, too much data can be as problematic as too little. “There is almost too much information,” GM’s Hildreth agrees. “I did a snapshot of our plants in the United States of how much data we had – we look at about 2.5 million data points every minute. From an enterprise standpoint that is unmanageable.”
To get around this, GM worked with UK-based system integrators SAIC to develop a dashboard system that analyses and prioritises all that information. “The net result is 15 energy management targets for things such as HVAC, fan energy, run times, set points, how much supply air we bring in from outside, how much we circulate – as well as having our energy metrics integrated into that dashboard system,” Hildreth says. “So we don’t have to wait until the end of the month to find out if we’ve got a plant that is not going to meet its energy target.
“This information enables us to drive our efforts where they are needed. For instance, we have people from SAIC who look at the screens on a regular basis so they can give us suggestions that generate projects for us.”
Considering a paintshop can consume up to 70% of a plant’s energy in its booths and ovens, it unsurprising that these are the subject of much attention. “We take two strategic approaches,” Hildreth explains. “The first is, if we are designing a new facility, a couple of subject experts will sit with the facility and process design teams and decide where we can optimise energy: it’s a huge advantage for us because if we are going to spend half a billion dollars on a new plant, this is the time when we want to ensure that we have energy-efficient equipment designed into the process.
“Our second strategic approach, if a plant is already built – we have a number of older facilities globally – is to go in and optimise the existing operations together with our subject matter experts. They are assigned to optimise the energy, but they do know the paintshop process: they will optimise temperature and humidity set points and ensure that we recycle as much air as possible, because every time we bring in outside air it costs a lot to condition it to the correct temperature and humidity. We have undertaken some pretty good payback projects using those two approaches.” Two brownfield sites on which GM has modernised paintshop operations are Lake Orion, in Michigan and Arlington in Texas. At Lake Orion assembly plant, the energy savings came from building a new paintshop that was optimised to suit the US sub-compact Sonic, as well as incorporating an innovative paint technology. A threewet process was added, which allows for the application of the primer, colour and clear coat materials in the same booth. This reduces the overall number of booths and ovens needed and reduces energy usage. Additionally, GM developed a radiant tube-paint oven heating system that was implemented for the first time at Orion and will migrate globally.
“In a traditional paintshop, you would fire up the ovens four hours in advance of painting, and you would spend a lot of gas to do that,” Hildreth says. “We can get that temperature up in the oven much quicker and shut that thing down, and you don’t have a lot of air blowing around in the paint ovens to introduce dirt to the paint job.” Arlington, on the other hand, epitomises the more typical scenario of managing energy within an existing facility. “We updated the plant equipment with energy efficiency in mind” says Hildreth. “Instead of just putting in new equipment, we had a look to see if we could redesign the systems so that we could save energy. In that particular instance we were able to reduce oven exhaust – we now use 90% recycled air with only 10% outside air as opposed to the original system design that was 90% outside air. Between all of that, downsizing the ventilation system and the abatement system where you are treating the volatile organic compounds that come off the paint, we were able to save close to $3 million a year.”
Outside of the paintshop – in BIW and final assembly for example – much of the process energy is locked in. In BIW most energy is used in welding, which is already a heavily controlled process, so lighting is the main focus, given that welding robots don’t need high visibility to operate efficiently.
In final assembly, HVAC is where most of the savings come, fuelled by efficient measurement and control systems. For Mercedes, ‘achieving more with less’ was the slogan of a project at the Unterturkheim plant that analysed the savings potential of all its ventilation systems. New machines that produce fewer emissions and less waste heat were installed, allowing the ventilation rate in the halls to be reduced. By optimising the control system and reducing the ventilation rate – by on average 23% – the energy bill was cut by 30,000MWh of heat and 22,000MWh of electricity per year, without degrading the employees’ air quality.