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K. Use of Water from Rawa Pening for Power Production

One of the main users of water from Rawa Pening is PLN (Perusahaan Listrik Negara) the National Electricity Supply Authority. Discussion with the staff of the Jeklok Power Station revealed some interesting points.

Water is used for 24 hours per day for power production, except when a turbine needs servicing. The actual power production is small (16Mw).

It is noteworthy that this mode of operation of a hydro-electric power station would be considered irrational in many countries. Even in East Java in the Brantas River system power stations, hydroelectric power is only used on a 24 hour basis when reservoirs are full. Normally, in that area, hydroelectric power stations are only used to provide peak load power during the morning period of maximum consumption. Hydro-electric power production has the useful property of quickly reaching high levels of power output. This contrasts with coal fired power stations where it may take some time for coal to ignite and heat water for steam production. In a coal fired power station there is therefore a time lag between the time when an increase in demand is noted and more power is requested and the time when that power actually becomes available. This is not the case in a hydro-electric power station where the request for more power can be met immediately by simply opening the valve allowing water to reach the turbines.

Hydro-electric power is therefore seen as a particularly valuable type of power production and is reserved for the purpose of meeting sudden demands for power, in most cases. It is therefore quite surprising that the limited amount of hydroelectric power available from Rawa Pening should be used in this way.

This is even more surprising when one finds that it is reported in the national press that there is an excess of electrical power production in Java at present. It is not within the scope of this project to investigate the working philosophy of PLN, or to investigate the economics of power production in Java.

Discussion with the staff of Jeklok Power Station suggested that the reason for this full-time use of hydroelectric power was because there was no charge for the use of the water from Rawa Pening. This was therefore a cheaper way for PLN to produce electric power than to pay for coal for a coal fired power station.

One may feel that this is not entirely rational in terms of power production within Java.

On the other hand, it is very much a concern for this investigation that PLN should use a major proportion of the water available from Rawa Pening without considering the needs of other users. 16Mw may be a very small proportion of the total power available in Java, but when an estimated 40% to 70% of the water in Rawa Pening eventually flows through the turbines of the power stations, it represents a major proportion of the water used from Rawa Pening.

PLN is an example of an organisation which uses the water in Rawa Pening as a free resource. The water, as far as PLN is concerned, is inexhaustible. The resource is seen as being infinitely large. In discussion, the staff were quite clear that they had never experienced any period when they had a shortage of water for power production. Whether they, by their actions, caused any shortage of water for other users was not known. As they pointed out, that was not their problem, as they were only concerned with power production.

There were some comments from other Government Staff that the failure of PLN to release water from the sluice gates during the wet season caused repeated flooding of villages near Ambarawa. The cost of losses due to this annual flooding is unknown.

There was some suggestion that it was preferable to flood the lower areas near Ambarawa rather than coastal areas to the north, as might happen if the flood gates were opened during heavy rain. The literature suggests that villages near the main Salatiga-Bawen road have also been affected by flooding from Rawa Pening.

No assessment was available of the relative costs imposed on the communities of flooding at Ambarawa versus flooding downstream. The basis of decision making in this case is not known.

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