A. Reinders, Ahme",pramusito,"sudradjat et al., Sukatani revisited: on the performance of nine-year-old solar home systemsand street lighting systems in Indonesia, RENEW SUST, 3(1), 1999, pp. 1-47
In 1988, 86 solar home systems, SHS, and 15 street lighting systems, SLS, w
ere installed in the village of Sukatani in the province of West Java of In
donesia. The systems have a PV array of 80 Wp.
In this paper we analyse the performance of these systems. For this purpose
we use monitoring data and data from field surveys recorded in the period
1988-1993 and data collected in a field survey in 1997. This survey compris
ed both technical measurements on 62 solar home systems and interviews with
22 users of these systems.
We found that, although the failure rate of street lighting systems is high
, the villagers have a positive opinion about these systems.
Further, we found that technically the solar home systems performed well. T
he users are satisfied about the performance. However, in the course of tim
e the configuration of the SHS has changed: villagers have replaced most of
the strip lights with cheap home-made candescent lamps and have replaced t
he initially-installed 100 Ah capacity solar batteries with cheaper locally
produced 70 Ah capacity car batteries.
From an analysis of monitoring data we found that the average irradiation i
n Sukatani is 4.2 kW/m(2)/day, which is a common value for Indonesia, but m
ore than expected in 1988 when the systems were installed (3.5 kWh/m(2)/day
). Furthermore, we found that daily electricity consumption per SRS can be
as high as 25 Ah/day, Average values, however, range from 8.8 to 14.8 Ah/da
y, which is 15-50% below the daily load used in the design calculations (17
.4 Ah/day). However, the average daily electricity consumption is close to
the recommended value on the instruction sheets given to the users of the S
HS. Because of the low demand of electricity the average performance ratio
is 49%. By means of an energy loss analysis of the PV systems we found that
15% of the theoretically available energy from the array cannot be fed in
the battery because it is fully charged.
The replacement of 100 Ah batteries by 70 Ah batteries was justified on the
grounds of the low electricity consumption of the SHS users in the period
1988-1993. On the basis of field surveys we found that the average lifetime
of the 100 Ah and 70 Ah batteries is 4 and 3.5 years, respectively. The re
alized battery lifetime is rather long compared with other SHS projects in
the world.
While the average battery size in Sukatani decreased in course of time, we
found on the basis of interviews with users of SHS that the average daily e
lectricity consumption increased. We found a value of 18 Ah/day in 1997.
Furthermore, the spread in the demand of electricity in 1997 and the use of
other than initially-installed appliances, such as small incandesent bulbs
and intercoms, indicates the need for a broad offer of system sizes and lo
w power appliances. By means of design calculations we found that PV arrays
in the range of 35-130 Wp are needed to satisfy different demand patterns.
We conclude that monitoring by means of data loggers is a useful approach t
o allow the analysis of the long-term system performance. To increase the s
tatistical reliability of results, monitoring should be supplemented by hel
d measurements and interviews with users. However, due to the deviation bet
ween real and narrated experiences, interviews alone may not be sufficient
to assess an SHS project. (C) 1999 Elsevier Science Ltd. All rights reserve
d.