Climate change and power generation

VILLAGERS settled near the shores of Lake Kariba tell of a time when fish were plenty on the water. Now fishermen are failing to fill up nets. The fish are gone, they say.

“The water at the lake is low. We have never experienced such. This lake is our life but you wonder who is sucking the water out. Temperatures are high, it has never been like this as far as I can remember,” said Mr Luckson Munhende who has lived in Kariba for years.  

That is the state of affairs obtaining at one of the world’s biggest man-made lakes. While Munhende decries the disappearance of his most loved delicacy, it is the impact of the dam’s low water levels on electricity generation that has become topical nationwide of late. 

The hot season’s impact is to be felt at its worst on power generation, a situation that engineers at the Zimbabwe Power Company (ZPC) say might lead to a total shutdown of the Kariba Hydro Power plant.

While there is no denying that ageing equipment at the plant can no longer capacitate high amounts of power generation, it has to be acknowledged too that climate change plays a huge part. The El Nino-induced drought has had the biggest blow.

Energy experts say the recurrent electricity shortage is in part a result of the drop in water levels at Kariba Dam, which undoubtedly is due to climate change.

The dwindling water levels at the lake, where the country’s biggest Hydro Power plant is located, is enough evidence of the dire effects of the changing climate characteristics.

Authorities at ZPC are not shy to reveal that if not much power is imported; a shutdown on Kariba is imminent.

Engineer Bernard Zengeya, the ZPC business performance manager, said Kariba Hydro Power Station could be decommissioned by end of September month owing to critical water levels. 

“The water levels are worrisome. The only way to offshoot the effects is to import. The minimum water level for power generation is at 478m, currently the water stands at 475m,” he said.

In the same vein, respected energy expert, Mr Eddington Mazambani, the acting chief executive at the Zimbabwe Energy Regulatory Authority (Zera), said talk of climate change impacts on Lake Kariba is scary.

“Climate change is a glaring reality when looking at Kariba Dam’s pathetic water levels. This in turn has led to water rationing for use at the strategic hydro power station.”

In order to understand this, the energy crisis in the country has to be intertwined with what happens globally. Climate change has far reaching effects to all humanity, meaning electricity shortage is not a Zimbabwe problem only.

According to a research by the National Geographic, the global average surface temperature rose from 0,6 to 0,9 degrees Celsius between 1995 and 2015 and continues on the same trajectory if not on the increase.

The world over, scientists and energy production engineers are trumpeting the call for the use of alternative energy as thermal and other fossil fuels are no longer sustainable. After deliberations by the World Energy Council (WEC), a position paper on the effects of climate change on energy globally was tabled.

“Climate change presents increasing challenges for energy production and transmission. A progressive temperature increase, an increasing number and severity of extreme weather events and changing precipitation patterns will affect energy production and delivery,” states the WEC.

A Bulawayo-based climatologist Mr James Mugawa stated that indeed climate change has had a causal effect on power generation.

“This has been studied over years. It has come to the conclusion that climate change is the key factor on the ever reducing water levels at Kariba. In essence, climate change causes extreme weather conditions and unpredictable, low rainfall patterns. 

“The El Nino effect we are having induces extreme atmospheric heat that causes high and frequent evaporation rates on water. Electricity voltage generation is a product of water head which is the difference of water in the dam and the level of penstocks,” he said.

The weather expert further explained:  “When there is drought the level of water reduces in the dam leading to a low water head which reduces the pressure with which water passes through penstocks hence reducing the rotation of the turbines which compacts negatively on the amount of voltage produced by the generator.” 

He added that hydroelectricity is not only produced from the water in the dams but it can be generated from other sources like waterfalls and these are also affected by climate change when it comes to power generation especially when temperatures become very high.

“Climate change results in reduced rainfall amounts and high rate of evaporation which reduces the level of water in the river. This means that water drops from the top of the waterfall into the plunge pool at a low velocity and pressure, resulting in slow rotation of the turbines in the plunge pull therefore leading to low voltage.

“Increased temperatures and reduced rainfall amounts have also led to many farmers relying on irrigation to supplement insufficient natural rainfall. This has increased consumption for water in the dams therefore instead of some water going to the generation of power some of it is consumed in the farms,” said Mr Mugawa.

He noted that even though climate change has low power generation, it has to be the push factor for solar power.

 “However, even climate change may also be used positively in power generation, this is because some countries are going green by using solar energy. There is now increased sunlight which is received by solar panels and directed to photovoltaic cells which then convert solar energy to electrical energy.”

Zimbabwe’s power generation according to Eng Zengeya is at 944 MegaWatts but the demand stands at 1 700MW.

Other power generation plants which serve as alternatives to Kariba have absolute equipment. ZPC said regardless of a 1 200MW installed capacity at Kariba, Hwange (thermal), Munyati (thermal), Harare (thermal), more power has to be sought.

The low levels of water at Kariba have affected a number of countries in the region with Zimbabwe, South Africa and Zambia already facing power shortages.

Source: The Sunday News

Post Author: Chido Luciasi

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