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Benefits of Co-generation: Utility Perspective


Bothwell Batidzirai


Electricity sector

Electricity sector is the sole supply domain of ZESA, which generates, imports and distributes all electricity in the country except for a few small private generators. Although reforms in the electricity industry are currently being implemented, the current legislation favours ZESA and disadvantages IPPs.

Entry of private players into the power sector will depend on progress on power sector reforms initiated to create a legal and regulatory framework supportive of private power development. However,currently, IPPs enter a captured market already dominated by the national utility. One such IPP is the cogeneration plant commissioned by Hippo Valley Estates in South Eastern Zimbabwe.

Cogeneration at Hippo Valley Estates

Hippo Valley Estates has commissioned a cogeneration plant that generates both steam and power for the sugar processing factory’s requirements and extra power for export to the national grid.

The total electricity load for the Chiredzi area (which is farthest from the country’s generating plant located in the North West) is about 25 MVA. The introduction of 5 to 10 MVA at HVE will result in significant changes in the power flow in this network. For instance, quality and reliability of power are expected to improve in the area.

The cogeneration plant is to be interconnected to the national grid to facilitate the export of power to the grid. HVE has the potential to generate up to 26MW and 15MW is to be used to meet factory and estate needs. While 11MW is for sale to ZESA. Up to 30 GWh can be supplied to ZESA over the 6 months of the crushing period. This figure can easily be doubled since the crushing season sometimes runs for up to 10 months.

Benefits of embedded cogenerator to the utility

The performance of Chiredzi 33kV network is expected to vastly improve when the cogeneration plant is interconnected to the grid. Improvements are expected in terms of quality of supply, reliability and reduction in line losses. Load flow assessments carried out on the network confirm that the voltage profile in the area would improve.

The utility is also expected to realize tremendous technical, economic and environmental benefits from the introduction of the embedded generator in the network.

Conclusions and recommendations

Deregulation of the electricity industry will force utilities to face new challenges and to evaluate the cost-benefit implications of providing an acceptable level of service. It is in the best interest of ZESA to welcome the entry of small scale IPPs who contribute significantly at local level, even if the national impacts are marginal.

There are tremendous benefits that accrue to the utility when embedded generation is introduced into an electricity supply system. These include: improved voltage profile on the local network which translates into improved quality of service to local consumers as problems of voltage fluctuations are eliminated; With proper protection system in place, reliability of the local system is improved as the local network can operate in island mode when there is a failure on the main grid. Clearly the image of the utility improves when quality of supply improves and supply is more reliable. It then becomes easier to promote the use of electricity. System losses are reduced significantly and this translates into loss reduction higher up on the grid network at immense benefit to the utility.

The use of green or environmental funding can help to bridge the commercial gap between ZESA and HVE, so that the concept becomes worthwhile for both the utility and the investor. The Lowveld area has huge potential of up to 210MW which could fully be utilized if adequate incentives and a conducive operating environment as well as enabling policy are in place. Additional potential exists in the timber industry in the Eastern Highlands where over 70,000 tons of wood waste is inefficiently disposed of.

It is also important to note that in other countries such as Mauritius, the concept of centralization of power production has been implemented whereby bagasse from other sugar factories is sold to the power producers. Similarly, it is worthwhile to consider the centralization of power production in the Lowveld either through consolidation of milling activities or supply of surplus bagasse to power producer.

It is in the best interests of both the utility and HVE as an investor to do everything in their power to utilize this wasted renewable resource by engaging in progressive partnership. Borrowing from the successful experiences of such countries as Mauritius, India and Brazil will go a long way in alleviating power supply problems and allow investment in the power sector.

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