Household appliances

Johan Smeds

During the last decades, electricity consumption for household appliances has increased substantially. For example, between 1970 and 1999, the energy use for household appliances in Swedish dwellings doubled from 9.2 to 19.6 TWh (Energimyndigheten, 2000). This fact clearly shows the necessity of taking a closer look at the energy use of household appliances. The different kinds of household appliances discussed in this section can be summarized as follows: washing machines and

Source: Björn Karlsson

Figure 14.2.9 A façade-integrated concentrating solar collector

Source: Björn Karlsson

Figure 14.2.9 A façade-integrated concentrating solar collector dryers; dishwashers; refrigerators and freezers; cooking equipment such as ovens and stoves; and, finally, lighting and other equipment - for example, radios, TVs and computers.

14.3.1 Household energy use

Since the amount of energy used for household appliances is almost as big or even bigger than the amount used for heating modern, well-insulated dwellings, there is a clear potential for economic and environmental gains by reducing their energy use. A reduction in energy use for household appliances can be even more important in comparison to other energy uses of a household since the source of energy for household appliances is mostly electricity. The delivery of electricity is combined with losses in the power plant and in the grid. Therefore, even a small reduction can have a rather large effect on the use of cumulative primary energy. For an energy efficient detached house built in 1990, the yearly energy use in Sweden is approximately 15,000 kWh. 5000 kWh are used for heating, another 4500 kWh are used for household appliances, 3500 kWh for DHW and 2250 kWh for fans and pumps (Lovehed, 1995). The shares of energy use are shown in Figure 14.3.1.

Source: Johan Smeds

Figure 14.3.1 Shares of energy use in an energy-efficient Swedish detached house in 1990

14.3.2 Potential reduction of energy use for household appliances

The energy use of 4000-5000 kWh for standard household appliances in 1987 can be reduced by approximately 42 per cent to 2770 kWh per year (Lovehed, 1995) by using best available technology (BAT) of 1995. Compared to the average of 1987, the energy use can be reduced by 54 per cent with BAT of 2002 (Niedrig Energie Institut, 2001). As shown in Table 14.3.1, the yearly energy use would then be 2178 kWh. The efforts made by developing new energy-efficient products are clearly shown by comparing the total energy use for BAT 1995 and BAT 2002. A reduction of 21 per cent for the energy use of BAT is achieved within seven years. Table 14.3.1 shows the energy used yearly in an average household for cooking, washing, drying, dishwashers, refrigerators, freezers, lighting and other electrical appliances, such as radios or television sets. A similar potential of reduced energy use for household appliances is documented in the Mure report on best available technologies in housing (Eichhammer, 2000). Despite the massive reduction in the use of electricity for refrigerators and freezers, there is still a potential to lower the electricity use even more. Simulations show that the energy use of an average German refrigerator can be lowered by 93 per cent from 370 kWh/a to only 27.6 kWh/a by using modern technology with vacuum insulation (Feist, 2001). According to Feist (2001), a refrigerator/freezer combination, built with the best technology known from today's research, could, in future, use as little as 100 kWh/a. This is to be compared to 230 kWh/a for the best refrigerator/freezer combination on the market in 2002.

Table 14.3.1 Yearly energy use of electrical appliances

Appliance

Standard 1987 (kWh/a) BAT 1995 (kWh/a) BAT 2002 (kWh/a)

Cooking

Washing + drying Dishwasher Refrigerator + freezer Lighting + other Total

1030 750 370 1450 1180 4780

568 621 250 457 874 2770

568 308 198 230 874 2178

14.3.3 Environmental effects

For calculating environmental effects, it is assumed that the electricity is generated according to the European electricity mix (EU-17). The non-renewable primary energy factor will, in this case, be 2.35 and the use of 1 kWh of electricity will cause 0.43 kg of CO2 equivalent emissions (GEMIS, 2004). For standard appliances from 1987, the yearly energy use of 4780 kWh results in 2055 kg of CO2 equivalent emissions and a primary energy use of 11,233 kWh. For appliances with the best available technology of 2002 and a yearly energy use of 2178 kWh, the CO2 equivalent emissions are reduced to 937 kg and the primary energy use is reduced to 5118 kWh.

Source: Johan Smeds

Figure 14.3.2 CO2

equivalent emissions, non-renewable primary energy demand and electricity end use 1987 (standard) and 2002 (best available technology)

14.3.4 Internal loads and space heating demand

For a house with a well-insulated building envelope and using effective heat exchangers in the exhaust air, it is absolutely necessary to invest in energy efficient appliances with best available technology in order to avoid overheating. This is not so important for dishwashers or washing machines, since most of the surplus heat from such appliances leaves the house with the wastewater. It is very important, though, for appliances such as tumble dryers, refrigerators, freezers and lighting equipment, where almost 100 per cent of the energy use is a heat gain to the indoor environment. In order to reduce the total energy use of a household, and in order to avoid overheating, the energy use of appliances in high-performance houses has to be kept at a very low level. Even in a cold climate region, the heating period of new high-performance buildings extends over only a few winter months. During the rest of the year the internal load of electrical appliances will either help to keep a comfortable indoor temperature or cause overheating.

Dynamic building simulations with the computer program DEROB-LTH (Kvist, 2005) of a single family house reaching passive house standards, situated in Stockholm, show that the use of standard appliances will reduce the space heating demand by only 257 kWh per year, while the use of electricity for appliances is 1893 kWh higher in comparison to energy efficient appliances. This means that only 13 per cent of the increased energy use due to standard appliances reduces the heating demand of the building. The construction of the simulated single family house corresponds to solution 1a of the high-performance single family house described in Chapter 8, Section 8.2 of Volume 1 in this series. The assumed electricity use of household appliances for four persons (two adults and two children) is shown in Table 14.3.2.

Table 14.3.2 Electricity use of standard and energy-efficient household appliances

Appliance

Standard case

Energy efficient case

Refrigerator

350

128

Freezer

550

299

Oven, microwave, coffee maker

212

212

Stove

356

356

Dishwasher

430

218

Washing machine

420

188

Dryer

640

214

Lights

850

300

Other

574

574

Total

4382

2489

0 0

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