Energy saving with inverters in refrigerating groups

Following a roadmap to renewables and energy saving, on the pace traced by our latest Tempco Infographic, I would like to talk about how energy saving can be specifically applied in all of the different thermal machines. Starting with refrigerating groups.

I remember when first attempts started on the market to employ inverters in order to adjust the speed of compressors on refrigerating groups. Inverters are largely employed to regulate speed on electric drives, adjusting the power absorption based on the season conditions. It’s clear indeed that during the summer season, when ambient temperature is higher, a refrigerating group needs the maximum power in order to achieve the refrigeration task required. While during the winter season it requires less amounts of power, due to a series of reasons such as the increased efficiency of the condensation system and the fact that water comes from the production process at lower temperatures.

The study to implement energy saving on refrigerating groups aimed then at adjusting the speed of fans on condensers using EC motors, with electronic control, through inverters. This allows the regulation of the speed of fans based on ambient temperature levels.

The same kind of adjustment was then possible on compressors. Let’s make an example to explain why: when sizing a refrigerating group employed to regulate the temperature of pharmaceutical reactors, the plant must be engineered to provide the maximum capacity required to achieve the cooling task. But there will be also a series of intermediate steps not requiring the maximum design refrigerating capacity, but maybe only at 50% or 30.

 

In the past it was used to employ multi-compressor plants, with step-compressors, using all of the compressors, or only 2 on 4, or one on 4 for example. The solution allowed to obtain a good energy saving, clearly using a step-approach. Which means, having a four-compressors plant, the possibility to have a 100% capacity, or at 75, 50, 25 or 0%.

A further improvement was to install a collecting tank in order to accumulate refrigerated water to satisfy peaks and hollows on the thermal work diagram. An optimal regulation, that can be furthermore improved.

The improvement consists in the employ of an inverter, which allows to adjust the speeed of the compressor in order to have the correct amount of power at the exact right moment when it’s needed. Which represents the very perfect condition. I remember that the first attempts to install inverters on compressors failed, because these were volumetric piston compressors that when powered by the inverter kept stuck.

The problem has been solved with the adoption of scroll-type compressors, that can be used with inverters. Taking a huge step forward in energy saving applied to refrigerating groups. There are also other possibilities to further enhance energy saving, such as using inverters also on pumps to regulate the pressure, but let’s discuss it in a next video.