Pressure Cooker Energy Saving

The domestic pressure cooker makes food preparation easier and introduces energy saving during cooking. This article is considers the essential aspects related

saving energy by using pressure cooker

to energy saving.
 
When comparing an open pot and a pressure cooker, the following basic aspects are observed:


1. The open pot performs its operation in the environment atmosphere (approximate absolute pressure of 1 atmosphere). Regularly, food cooking is performed in the presence of abundant water, all of which causes the temperature in which food is cooked to be close to 100° C
 
2. The pressure cooker, by containing a higher pressure (internal absolute pressure of approximately 2 atmospheres), makes water boiling temperature (at that pressure) close to 120° C, for which the pressure cooker performs at higher pressure and temperature than the open pot and achieves a final product with similar quality in less time. In it, also, cooking time decrease increases fuel saving and the energy it represents.  

Within the technical parameters that most influence the efficient performance of a pressure cooker is pressure, since this depends of the temperature.
Technical deficiencies related to pressure:

1. Lack of vacuum sealing in the lid due to steam outlets in poor shape, lid deformation or imbalance in the handle – lid joint.


2. Lack of vacuum sealing in the weight, due to wear or filth in the weight or in the rod, which causes steam outlet in the first minutes and delays the achievement of working pressure.


3. Lack of quality in the weight. If the weight is below necessary, the pot will perform at less pressure and will require more cooking time. We can also include here the inadequate exchange of weights amongst pots.


Depending on the manufacturer and each country’s regulations, working pressure in each pot can be different, but usually a value close to two atmospheres is used as absolute pressure.

The influence of pressure is very high in the pot’s performance, since pressure also determines temperature.

Gauge pressure measurement is common instead of absolute. For example, if a pot has an absolute pressure of two atmospheres, it can be decided that it has an excess of one atmosphere above the atmospheric pressure value. This excess (or defect) of one in relation to the other is denominated gauge pressure, commonly measured with a gauge, for which from this moment we will consider it as adequate pressure for a pot, the value of one gauge atmosphere.

In a sampling (relatively small) of pressure cookers in use, performed by the author, we detected that most of them had gauge values closet o 0.6 atmospheres (i.e. 60% of the adequate value). The causes were mentioned before, although we should add that there is great incidence of new pots that don’t meet the one atmosphere gauge pressure requirement. 

Pot working pressure control diagram.

When comparing fuel required by a pot with a one atmosphere gauge pressure and another with 0.6 atmospheres, we detected that pressure decrease caused a 50% increase of fuel use. This indicator reflects the analysis final objective: avoid excessive fuel or energy consumption.

To illustrate the weight’s weigh influence, in an analyzed case we concluded that a 13 g weigh variation, which equals a 3.5 mm height increase (or decrease), causes a 1% pressure variation, and which is the maximum variation allowed as production quality control. For which larger weight variation (common in many renowned brands), cause inadequate pressure variation. Weight exchange between pots is not an advisable habit. 

Usually, pot maintenance or repair includes a group of appropriate mechanical adjustment practices, but the most important of all is rarely considered: working pressure control, even considering that the objective of all the pot’s elements is achieving (stable and safe) one atmosphere gauge pressure and, in consequence, 120° C temperature.

Below we suggest maintenance, repair and adjusting technicians, a working pressure control diagram.

From a compressed air source a, through a pressure regulator b, an adjustment valve c and a gauge d, we connect a flexible hose e, using the safety valve orifice.

With the lid appropriately placed we increase pressure until the weight allows the air to escape with its regular movement. Under these conditions, with similar pressure it would have when performing, gauge pressure is measured with the gauge. Usually gauge values between 0.9 and 1.1 atmospheres are considered appropriate. If a value inside this range is not achieved causes should be determined and decisions should be made.

No matter how clean and adjusted all the pot parts are made (which is necessary), only a pressure control guarantees its optimal design performance. Lower pressures (which are frequent) imply an excessive and unnecessary fuel or energy consumption.
 
It’s a fast and simple way of cooking dishes that require quite a lot of preparation time. It also allows great energy savings and cooking with less fat.
The pressure cooker’s appearance is a clear example of adapting to new times which require fast cooking. Far are the times when cooks with future plans would cover the edges of saucepans with bread crumbs to prepare dishes faster.

What was probably unknown then were the great advantages that this type of cooking implied. Besides the unquestionable energy savings, which can reach up to 70%, food retains it nutritional value by reducing preparation time. Besides, the lid’s hermetic sealing avoids flavor loss.

In any case, the pressure cooker took some time incorporating to kitchens. Security problems in the first models that hit the market caused trust issues amongst the users. Now, security devices in the new pots guarantee reliability when using them.