Bui cuts down power supply

Ghana’s energy crisis, which has resulted in load-shedding exercise, is likely to worsen, as the Bui Power Authority (BPA) has reduced its current generation capacity.

The reduction of the generation capacity, which is due to drop in water levels in the dam, has forced the Authority to limit the generation capacity to an average of about 1.44 million kWh/day.

The BPA was operating its generation plant at an over-draft rate of 3.66 million kWh/day from November 2013 instead of the 1.44 million kWh/day, in order to supplement existing generation.

Mawuli Fui Kwadzovia, Assistant External and Communications Relations Officer, BPA, in a release said, the Bui Generating Station is unable to maintain the high rate of power generation, and production has had to be reduced in order to protect the turbines from potential damage.

“This is necessary because it is imprudent to operate the generating plant below the minimum operating level of the reservoir (168 masl) as this unduly exposes the turbines to higher risks of cavitation damage,” he said.

Fui Kwadzovia said the current situation was also not favored by the hydrology of the Black Volta River as expected inflows in May and June were usually very low.

However, he said BPA was monitoring the reservoir level and will revise the production plan in conjunction with GRIDCo as soon as it is prudent to do so.

Background

The reservoir created by the construction of the Bui Dam was designed to have a maximum water level of 183 meters above sea level (masl) and a minimum operating level for power generation of 168 masl.

By June 2011, construction of the dam had progressed sufficiently to allow the commencement of river impoundment. Filling of the Bui reservoir therefore commenced on June 8th 2011 and about two years later; by March 2013, the water level had risen from about 100.0 masl to more than 168.0 masl. This level was just adequate to allow the start of power generation in May 2013.

Planned 2014 Generation

At the end of the 2013 rainy season in October 2013, the reservoir level had risen to 177.9 masl which was still well below the maximum reservoir level. The limited amount of water stockpiled during the rainy season therefore had to be used judiciously in order to last through the dry season and until the start of next rainy season in July 2014.

Based on the limited amount of water obtained in the 2013 rainy season, BPA planned to drawdown the Bui reservoir at a rate which could be sustained throughout the dry season.

Generation was to be restricted to an average of about 1.44 million kWh/day during the period.

Actual 2014 Generation

In response to the inadequate power supply from other sources experienced in the last quarter of 2013, the system operator, GRIDCo, requested BPA to temporarily increase power generation from the planned draft rate of 1.44 million kWh/day to an over-draft rate of 3.66 million kWh/day from November 2013 (about 2.5 times the target rate) in order to supplement existing generation.