You have probably heard the term ‘empty calories’, referring to food with low or no nutritional value coupled with high energy content. The same concept can be transferred to energy use, consuming high amounts of energy (calories) to provide a small amount of actual work. Consider a hair dryer, it uses a lot of electricity to evaporate and remove a small amount of moisture from somebody’s hair. In the food industry many processes remove unwanted water content as part of the process, this requires a lot of energy. However, few recapture the energy that goes into the evaporation of water. This is a huge waste of energy, but solutions are readily available.
Current Situation - The Case of Potato Chips
Potato chips (UK: crisps) frying is perhaps one of the easiest case to dive into to explain the situation. Up to 90 percent of the energy when producing potato chips goes into the frying of chips. Then more than one quarter of the energy that goes into frying is lost in the exhaust gases. This because water needs to be removed from the potato to become a chips.
When entering the fryer, a potato chip contains about 80 percent water. After processing the moisture content is typically only two percent. Ready-to-eat breakfast cereals from wheat, rice or maize go through a similar process and end up with a similarly low moisture content. This list is long, just consider what processed or pre-fried foods there are available in the supermarket.
Another source of empty calories is that the exhaust contains compounds, such as frying oil, Volatile Organic Compounds (VOC) and odor particles. These need to be removed before releasing the exhaust to the air. More often than not, this is done by using even more energy to burn off the unwanted particles in the exhaust.
How we can solve it!
The water naturally occurring in the ingredients is both the problem and the key. As the water is evaporated it exits the process as low pressure steam. The evaporation of water takes a lot of energy, but as the waste heat is carried in water it is also relatively easy to recover the energy by condensation the water.
Companies such as Centriair have solutions that can recover both the wasted heat in the exhaust and remove unwanted particles. In a brilliant setup that first separates oil for reuse or recycling, a second step condensates the steam in a heat exchanger to capture the waste heat, and finally remove the particles by an advanced UV-treatment.
Recovered heat can then be used to heat buildings, preheat and the dry different stages of food processing. If there is no use for heating, a Climeon Heat Power System can convert this low temperature waste heat into electricity. The electricity can then be used to offset internal electricity consumption. Reducing the need for grid-purchased electricity while improving the factory energy efficiency.