The values presently analyzed were measured during the summer month of February, 2004. Although the solar absorbed energy is high, the number of showers per inhabitant

tends to increase compared to other seasons, possibly having a negative net effect on the solar fraction.

Fig. 3 shows the daily totals of solar irradiation on a horizontal surface and the daily average of ambient temperature during February 2004. The daily total of solar irradiation data and the daily average ambient temperature were measured in a site[1] located 25 km distant from the housing unit. The solar irradiation distribution as well as the ambient temperature is similar to those measured at the reference site. It can be observed in Fig 3 that the analyzed month had high solar irradiation levels, low values occurring only on two days. The daily average temperatures during the month lie between 20°C and 30°C, which are typical values for the summer season in Florianopolis.

Suspicious data, collected from vacant apartments or resulting from incorrect use of the CSDHWS, were discarded from the analysis. Measured data from a total of 44 consumers from Group A and 24 consumers from Group B were used.

The measured power of each of the showerheads was totalized in hourly intervals and divided in three subsets according to the weekdays as follows:

(a) workdays;

(b) weekends and holidays;

(c) all days.

This division is intended to verify if differences exist in the consumption profiles between workdays, weekends and holidays.

Fig. 4 shows the mean electricity consumption profile of Group B. It can be seen that the consumption profile is characterized by a very low consumption from 2 AM to 5 AM. After this time interval, the energy consumption rises to a new level that persists until the middle of the afternoon (4 PM). During this period, a small peak was found before noon, probably caused by those who work or study only during the afternoon. At the end of the afternoon, the energy consumption increases substantially, reaching its peak around 7 PM, to then decrease. The relation between the average consumption and peak demand (load factor) was 0.37. The visual inspection of Fig. 4 leads to the conclusion that there is no considerable difference between workdays and weekends.

The average hourly energy consumption of Group A is compared with the values for Group B in Fig. 5. The hourly peak of energy consumption still remains in Group A, however, the energy consumption is significantly reduced compared to Group B. The load factor was 0.38, which is practically the same value obtained for Group B. Comparing the peaks of the two groups, it was found that the peak demand of Group A is 60% lower than the peak demand of Group B.

Fig. 6 shows the hourly solar fraction, considering that the hot-water consumption profile is the same for both groups. It can be observed that the solar fraction varies from 40% to 80% during most of the day, but it becomes lower in the morning periods. This is probably due to the storage tank heat losses during the night and also to those cases where stored hot-water was consumed during the previous day. From to 2 AM to 5 AM the solar fraction is not representative since hot-water consumption is low. The solar fraction obtained during the analyzed month (February 2004) was 58%.

The true peak demand can be identified from instantaneous power values. In the present analysis, power is averaged in 5 minute intervals, which can be considered a good approximation of the instantaneous values. Fig. 7 shows the average power of Group B on the day during which the highest peak occurred (01-Feb-2004). The same is shown in Fig. 8 for Group A (28-Feb-2004). It can be seen in Fig. 7 that the maximum contribution of the electric showerhead to the peak of each low income consumer was 0.57 kW. On the other hand, Fig. 8 shows that for a group of consumers with the same characteristics, but owning a CSDHWS, the contribution to the peak is around 0.30 kW. Therefore, the power necessary to supply electricity to the showerheads was reduced by 47% with solar heating.

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