The impact of water heating on the overall consumption of electric energy in Brazil

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Based on the results from the latest survey, it is estimated that 22.6% of the electric energy consumption of the residential sector is using an electric shower device (Figure 1) which instantaneously heats the water as it flows through it commonly called Instantaneous Electric Shower Device; in turn, this represents about 6% [7] of the electric energy consumption in the whole of Brazil (± 22 TWh).

The graph of the average residential load curve in Figure 2 reveals that it is at peak-hour_ normally between 06:00PM and 09:00PM_ that the use of electric shower as a water heating device is the most widely spread [1].

The value indicated in brackets in the key corresponds to the percentage in electric energy consumption for each domestic piece of equipment.

image002 Подпись: □ Microwaves (0,1%) □ Washing machine (0,4%) □ Iron (2,6%) □ Sound (3,5%) □ TV (9,5%) □ Air conditioner (19,8%) U Electric shower (22,6%) □ Rumination (14,3%) □ Freezer (5,2%) □ Refrigerator (22,1%) image004

The load curve of the Brazilian Electrical System-BES, on a typical day, is shown in Figure 3 [11]. Fig. 2. Residential Average Load Curve (W) Fig. 3. Load Curve of the BES (MW)

These studies about the Ownership and the Utilization of Equipments (Pesquisa de Posse de Equipamentos e Habitos de Uso — PPH in Portuguese) coordinated by PROCEL/Eletrobras, are also meant at qualifying the type of ownership, using a customised questionary but with the same standards of measurement from other research institutes for relevant comparison. Through the careful analysis of the individual answers from end consumers regarding the use of their domestic equipments, it is possible to raise important data about living conditions and socio-economic information for example, as well as about the quality of the electric energy supply as a whole, market changes following the electric energy rationing of 2001, domestic appliances purchasing habits etc.

Table 1 shows a summary of the comparative data from the various surveys ran by PROCEL between 1988 and 2005 about instantaneous electric shower ownership in Brazil: it is clear that the number of households using this device increased over those 17 years.

Table 1. Percentage (%) of Brazilian households with electric shower

BRAZIL

North

Northeast

Center-West

Southeast

South

1988

67.6

7.9

15.2

73.0

83.6

88.2

2005

73.3

4.0

30.3

85.5

91.1

98.6

In 2005, 42 % of all residencial electric showers were turned on between 06:00PM and 07:00PM causing the Brazilian Electrical System-BES to reach its maximum level in electric energy demand.

There was also a noticeable change of habits in the first hours of the day. Whilst in 1988, 10% of all households in the country had at least one person using this equipment between 06:00AM and 08:00AM, in 2005 this percentage had increased to 31%. (Figure 4).

Fig. 4. Use of electric shower (typical day)

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According to Table 2, the Southern region not only has the highest index in electric shower use as well as the highest average ownership with 1.17 electric shower per household_ way above the national average of 0.89.

Table 2. Average ownership of electric shower per household in unit (2005)

BRAZIL

North

Northeast

Center-West

Southeast

South

0.89

0.05

040

1.08

1.10

1.17

Futhermore, it appears that 21% of all interviewees, by 2005, had already switched electric shower devices for solar heating systems. A new demand is also emerging by means of the efforts of a few Brazilian municipalitiescouncils to integrate within their City Planning Directives the obligation, for all new buildings, to offer solar collectors installation facilities.

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PROCEL has been focusing, with partner entities and enterprises, on promoting the technological development of equipments using solar energy for water heating.