Washing Machine Works on Which Principle

A washing machine is a machine that can wash certain items. This article deals specifically with machines for washing laundry, in the form of a washing machine that has been common for decades. After filling the laundry and the detergent as well as setting the desired program, the entire washing process – usually including slingshots – runs fully automatically. For some appliances, which are called washer dryers, even the laundry can be dried afterwards.

Washing by hand would be much more tedious and would usually not even save energy.

The widespread introduction of washing machines is one of the most important simplifications of housework, which no one would have wanted to do without today. Here a certain energy consumption created, usually in the form of electrical energy. Modern washing machines are, of course, optimized in such a way that it would be difficult to wash more sparingly by hand. This is due to the fact that you usually need more hot water for a hand wash, while the drive of motors etc. plays a minor role in energy consumption.


Functional Principle of Washing Machines

Functional Principle of Washing Machines

In the case of the drum washer, which is by far the most common type in Europe, the core is a cylindrical stainless steel laundry drum that can be rotated around its axis with an electric motor. (So-called vat washing machines with a fixed washcloth and a stirrer arm are still very common in the USA, but not in Europe, mainly because they are extremely inefficient and wash worse.) The lower part of the laundry drum is in a mostly heated washing liquor, i.e.dem washing water with a detergent that is added in the form of powder or a liquid. By occasionally rotating the drum to the left and right, the laundry is pulled through the washing liquor and moderately strong, but often walked through.

The washing phase today usually consists of only one main wash cycle; sometimes, there is a pre-wash or even a soaking beforehand. Subsequently, the washing is repeated with fresh water in order to remove dirt and residues of the washing liquor to a large extent from the laundry. A softening agent can be added during the last rinse. After that, the slinging is usually carried out at high speed in order to drain the laundry as much as possible.

Commercial washing machines usually operate on the same principle as described above but are optimized for commercial use. For example, they handle much more laundry, wash in less time (for more washing sands per day) and may use additional equipment to reduce water and energy requirements. For example, water can be used after rinsing for a later wash, or heat recovery from the wastewater can be carried out.


Washing effect and energy consumption

The strength of the reported washing effect depends on several important factors – not only on energy use:

Many factors determine the washing effect, which is why a high energy input can also be replaced by the optimization of other factors.

  • The more aggressive and higher the dose of the detergent, the higher the washing effect is in general. However, this should not put too much strain on the laundry; in particular, dyes can fade over time by bleaching dyes, i.e. become pale. In addition, aggressive detergents tend to be more polluting unless they can be mined in a wastewater treatment plant. For such reasons, the aim is also not to dose the detergent too high.
  • The effect of detergents can be impeded by the content so-called “hard” water of certain minerals. This can be compensated by adding correspondingly more detergents or additional aids. A possible alternative is the softening of the water e.B. with an ion exchanger.

The washing temperature is the most important factor in energy consumption!

  • Most contaminants can be removed better at higher temperatures of the lye. However, there are exceptions; for example, the removal of proteins is easier if the alkaline temperature is not too high, at least initially, in order to avoid denaturing the proteins before washing out. On the other hand, the washing temperature is the most important factor for energy consumption, since water heating requires far more energy than .B. the operation of the electric motor driving the drum.
  • An intensive mechanical action (walking through) improves the washing effect, but also leads to a load on the laundry, which makes it wear out faster. If the machine is overfilled, the laundry is less walked through and therefore, less well washed.
  • The use of a low water level in the drum reduces the energy required to heat the water, but not necessarily the washing effect. Note that the washing liquor is then more concentrated with the same amount of detergent.
  • Finally, an increase in the duration of the wash can also improve the washing effect.

The manufacturers of washing machines try to achieve a sufficiently high washing effect, but at the same time, do not overburden the laundry and at the same time consume as little energy as possible. A balanced combination of the above factors is, therefore, necessary. In order to save energy, the washing temperature is now as low as possible – in special savings programs even lower than indicated by the program selector. Since the manufacturer of the machine has little influence on the detergents used, he is most likely to compensate for the low washing temperature by extending the washing time, which can usually be accepted by the users (at least in private use).

In the case of modern machines, a number of other measures are taken to use as little energy as possible for a given washing effect. Examples:

  • Many machines today have a kind of loading sensor or automatic quantity, which reduces the amount of water used accordingly when the machine is only partially loaded. For example, the load can be determined by how much lye the laundry absorbs, i.e. how much water level decreases again after the louse has been inlet. If less water needs to be heated, it also saves energy. However, you usually need. B more than half the full amount of water, i.e. per kilogram of washed quantity, if only half the machine is loaded, more than with optimal loading.
  • Some machines allow the additional connection to a hot water tap. Then the heating of the lye takes place at least up to a temperature of e.B 55 or 60 °C via the heating system instead of the electric heating rod installed in the machine. This is usually much more energy efficient. For example, a gas heating system for hot water heating requires only about half as much natural gas as when using an electric heating rod with electricity from a modern gas-fired power plant. Ideal, of course, is the case of solar hot water heating. By the way, unlike dishwashers, it would not make sense to connect a washing machine with only one water connection to the hot water, simply because hot water would then be used unnecessarily for rinsing. At most, this problem could be solved with a special ballast, which gives the machine warm water at the beginning, in order to switch to cold water later.
  • The highest possible spinning speed helps to thoroughly drain the laundry after washing. This costs slightly more electrical energy when spinning, but saves significant amounts of energy during subsequent drying. This is especially true when using a tumble dryer, but in winter often even when drying on a leash in the basement, when it needs to be ventilated, and the cellar then cools down.
  • The system of lye pump, heater, valves, etc. should be designed in such a way that as little lye as possible remains unused in such parts.

Anything that improves the washing effect without consuming additional energy can ultimately be converted into energy savings.

  • A well-designed laundry drum, which is moved in an optimized manner, improves the washing effect and therefore allows savings e.B. via the washing temperature. Flood systems that pump lye into the laundry drum during washing also increase efficiency.
  • Virtually all modern machines today also offer savings programs that either achieve a similar washing effect to the normal program with significantly longer washing time or also cause certain reductions in the washing effect, which are acceptable in case of low contamination of the laundry. The focus is usually on the reduction of the washing temperature and the amount of washing liquor.

The lowest possible water consumption is also of interest in principle but is less important both economically and ecologically than energy consumption (at least in Central Europe).


Choosing a thrifty washing machine

Choosing a thrifty washing machine

The consumption class A+ no longer contains the best, but even the worst devices – devices of class A to D are now banned!

An assessment of the energy efficiency of a washing machine is hardly possible on the basis of technical specifications on efficiency-enhancing measures as described above. Rather, one should not orientate oneself on the corresponding prices of the manufacturers, but on the actual energy consumption e.B. per wash, which of course depends on the type of washing process and the loading.

Figure 1: Energy labelling model under the EU Ecodesign Directive.

Today, all new washing machines sold in the EU must be labelled with energy consumption labelling, which includes standardized information. The total power consumption per year is given, based on the assumption that 220 washes are carried out in certain washing programs per year. This may not correspond to actual use in individual cases, but it does lead to well comparable consumption figures. In addition, the device is classified into an energy consumption class for easier comparisons. It should be noted that class A+, which appears to be very good, is no longer the optimum; Since December 2013, worse devices are no longer allowed. Machines in the newer efficiency classes A++ and A+++ are even more economical. The additional price for a more efficient machine can pay off several times over the course of the life of hopefully ten or more years.

Of course, the washing machine should also be the right size. A small drum for, for example, 5 kg of laundry per wash, may often be a sensible choice for small households. For a family, a model with a capacity of 7 kg may also be displayed, although such a machine can usually be well filled in practice. In this case, washing with a larger device also tends to be more energy-efficient.

Standby consumption is no longer a problem for new devices thanks to EU regulations.

The standby consumption, which is problematically high for some older models, is now also covered by the aforementioned energy consumption labelling. (There should also be older machines from brand manufacturers that consume 10 W or even more on standby, which would mean 87.6 kWh per year – as much as for dozens of additional washes.) It is no longer a problem with new devices anyway, as the European ecodesign requirement limits standby consumption since 2013 to a maximum of 1 watt (with information and status display) or 0.5 W (without display).

For a reasonably efficient machine (for 7 kg of cotton), the power consumption of around one-kilowatt hour should suffice for each wash at 60 °C, with hot water connection even considerably less (e.B. 0.4 kWh). With an Eco program without the hot water connection, it can be e.B. 0.7 kWh – with about the same washing effect, but significantly longer program duration. On the other hand, at 95 °C washing temperature (7 kg cotton, with cold water, without eco-program) it is already over 2 kWh.

For example, compare this consumption with the total daily electricity requirement of 10 kWh of a single-family house with two relatively economical residents. For example, if a wash with 1 kWh consumption were needed every five days, this would be about 0.2 kWh per day, which is only 2% of the average electricity demand. If washed more often, especially with higher temperatures and with an older machine, it can also easily be several per cent of the total power demand.

It is remarkable, by the way, that a kilowatt-hour would be sufficient for the preparation of about 20 litres of hot water e.B. in an electric boiler. This shows that a washing machine that consumes only 0.4 kWh in an eco-program for 7 kg of laundry has to achieve the washing effect with very little warm water. It is therefore unlikely that the electricity consumption of washing machines can be reduced much further in the future.

By the way, it is usually not worth replacing an older but still working washing machine for energy saving. Only if the consumption of the old washing machine were extremely high, and it was used frequently, the early replacement could be financially amortized. 


Efficient use of washing machines

If you want to save energy when washing, you won’t be able to create an unnecessarily large amount of dirty laundry as a first step. For example, you won’t do strenuous gardening with a newly washed shirt, where it will sweat again.

Even with modern machines with quantities of automatic or similar, the most efficient thing to wash is when fully loaded.

The next important factor is to load the washing machine as full as possible (according to the manufacturer). Although modern machines can adapt to less loading, full loading remains the most efficient. However, overloading should also be avoided, as this can greatly reduce the washing effect. If one tried to compensate for this by an increased washing temperature, the efficiency advantage would already be gone.

In no way should the calling speed be reduced, as far as this is not necessary for the protection of particularly sensitive laundry. This means that the washing machine hardly needs less energy, while the effort for drying is much higher.

Now the right washing program should be chosen, where the washing temperature is the most important factor for energy consumption. This should be based not only on how high the laundry tolerates but also on the degree of contamination of the laundry. For example, for laundry, which should be washed at 90 °C, usually, a washing temperature of 60 °C is sufficient, if it is not heavily and stubbornly polluted. If necessary, an austerity programme can also be used.

It is highly advisable to familiarize yourself with the manual of the washing machine. Otherwise, it may happen that you regularly choose a washing program with unnecessarily high energy consumption. For example, some users do without savings programs in the opinion that they reduce the washing effect, although they might learn from the user manual that this results in the same washing effect, only with longer program duration.

In some cases, it can even be washed at 20 °C, which is extremely economical.

When choosing a good detergent (which contains, for example, certain dirt-releasing enzymes), it tends to work with lower temperatures – in some cases even at just 20 °C. However, the machine should be operated at least occasionally at 60 °C or more. Otherwise, bacteria can survive, which over time lead to unpleasant odours (musty laundry). The risk of germination also depends on the detergent used.

Since many modern washing machines can also be delayed in starting the laundry, washing can easily be moved into the night hours in order to use cheaper night electricity. On the other hand, if you operate your own electric, solar system, you will try to install the washing machines in times of good sunlight in order to optimize the proportion of self-consumption. Of course, the financial savings that can be achieved is quite small. The same applies to plans to integrate washing machines into load management in the future, for example, via a system of circular control.

Calcification of the device, which reduces energy efficiency, should hardly occur in practice when used properly. In the case of hard water, a little more detergent may need to be used or a suitable additive. Otherwise, on the one hand, lime stains in the laundry and on the other hand, damage to the washing machine are risked. Contrary to what is often claimed; however, energy consumption is unlikely to increase, as the heat generated in the electric heating rod can hardly escape outward even in the presence of a lime layer. The heating rod then simply becomes hotter inside.


Combination with tumble dryer

Tumble dryers are usually used as stand-alone appliances. However, there are also so-called washer dryers, which combine the functions of a washing machine and tumble dryer. However, this is not optimal, as a given-sized drum, which is optimally filled for washing, is too full for drying. So you would either have to wash a smaller amount, which is inefficient or remove some of the laundries before drying.

Note that machine laundry drying is much more energy-intensive than washing with the washing machine and can also be replaced much more easily, for example by drying on a leash.

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I am tech writer who is passionate about technology and spearheads the core writing team on tech news

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