Electrification in the food industry
December 15, 2020
Electrification appears to be one of the possibilities to meet the objectives of a gas-free production process. But that has some snags, says Izak Boot. “Do it smart or don’t do it.”
Izak Boot is an energy transition specialist at engineering and consultancy firm Bilfinger Tebodin. He increasingly sees that customers in the food industry are wondering how their production facility or factory can operate gas-free and what role electrical engineering can play in this. “These demands are often made by a (foreign) head office without local knowledge. Or from countries without an extensive natural gas network and a high supply of sustainably generated electricity. Here in the Netherlands, the situation is often completely different.”
Electrifying heat demand
The Dutch food industry is responsible for about 7 percent of the total energy consumption of the industry as a whole. Electrification of the applications that currently require gas can be a solution to reduce natural gas consumption and make it more sustainable. Because there is a lot to save, Boot sees in practice.
“The heat demanded by the Dutch food industry is usually below a hundred degrees Celsius. Often, however, energy carriers are designed to meet the temperature requirements of a single application that requires more than a hundred degrees. This is not convenient from an energy perspective and makes direct electrification unnecessarily expensive. Take, for example, a dairy factory. In that factory, an evaporator operates at 180 degrees Celsius with steam. Most other applications require much less heat, but still a boiler is installed in that factory that also supplies all those other processes with 180 degrees of heat. That’s something we see a lot with customers.”
Electrification is one of the possibilities as an alternative to heating with natural gas. But there are more options, sees Boot. “Think of the use of residual heat. If it is directly applicable, it is both economically and technically more interesting than electrification. Unfortunately, the supply of residual heat at the right temperature level is limited and sometimes difficult to utilize.” In addition to residual heat, there are biofuels such as biomass and bio-oil or diesel, but there is quite an image problem with that in the meantime. “Biogas is often too little available (on-site) and therefore not a total solution.” Furthermore, there are high expectations of hydrogen or green gas, but that is not yet really alive within the food industry. “Even apart from the costs.” All that remains is electricity. You can approach the electrification of heat demand from different angles. First, you can focus on the utilities, i.e. the direct electrification of the current steam-water heating installation.
The second possibility is to start with electrification at the heart of the factory: scrutinizing the process itself. Look where heat is needed and consider how you can adjust process steps so that they run on electric energy. An example is the replacement of thermal separation processes by centrifugal processes. With electrification it is also important to maximize the use of residual heat and heat pumps. This is good for the energy and financial efficiency. A prerequisite for efficient electrification with heat pumps is to adjust the process as far as possible, so that the utility matches the required temperature level, says Boot. “Replace steam with hot water where possible. Most applications require less than a hundred degrees Celsius, as mentioned above, but get heat at a much higher temperature because a single other application in the plant requires that high supply. That’s a shame.”
Direct electrification unattractive
Simply replacing utilities one-on-one with electrical ones is expensive. Boot: “You have to deal with high investment costs for adapting the grid connection and electricity distribution and possibly transformers. You also pay a high capacity fee periodically. Furthermore, you don’t change anything about the process: heat is still supplied at a high temperature level, which is not necessary in most places. It is often not possible to use a heat pump in combination with waste heat.” So both the investment and operational costs are high, according to Boot. “At the current rates for natural gas and electricity, heating with natural gas is still more than twice as cheap as direct electric heating. Simple direct electrification is therefore expensive and the payback time is often negative. In addition, in the case of ‘grey’ electricity, more CO2 is emitted.”
Electrification must therefore be done in a smart way if it is to have any chance of success, both economically and technically. At the same time, electrification can be an opportunity for better energy efficiency, Boot thinks. “Then you would have to use a different order of focus. First, look at energy efficiency and building heating. Do that as much as possible with heat pumps and residual heat instead of natural gas or steam. This is already being used in new buildings, but technically it’s quite a bit of puzzling work for which, unfortunately, not enough time and budget is being made available.” Next is step two to look at the process.
“Change your process steps and equipment so that thermal heat is replaced by electrical heat. If a machine needs to be replaced, first consider whether it can be done electrically. Electrification becomes more cost effective when the energy carrier is adjusted to the required temperature level of the process. So thermal oil or steam heating replaced by hot water. A residual heat network can play an important role in this. Then you don’t even have to electrify.” The last step is to look at your utilities. “I mean, for example, a compact electrical steam installation for those processes that really can’t do without steam and need more than a hundred degrees Celsius. Another possibility that is being applied more and more widely is a central hot water distribution network at one or possibly two temperature levels where the integration of the residual heat present is the starting point. The required hot water can be efficiently produced using a heat pump with industrial waste heat as a source, if possible. This can also be low-grade heat such as wastewater or cooling water. A point of attention is buffering and delivery of the peak demand.”