Where does most of our electricity come from?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

21 February 2021

I read a report recently which stated that Kenya was the world leader in geothermal power because more than half (51 per cent) of our electricity in 2020 came from this source. Our closest rival was Iceland with 30 per cent.

When I shared this finding on Twitter, someone came out strongly (with data and pie charts) to point out that only 30 per cent of Kenyan’s installed generation capacity is geothermal. So how can it be that the sour with 30 per cent capacity generates 51% of the electricity?

It depends on how long the power station is operated during the year. We can get an indication of that duration by comparing the electrical energy (kilowatt-hours - kWh) produced in a year to the installed capacity (MW) of the generator.

The Kenya Power and Lighting Company’s (KPLC) annual reports contain this information, albeit indirectly. Unfortunately, due to delays in the appointment of the Auditor General, the latest available one is for the year 2018/19.

In that financial year, the country’s total installed capacity was 2,712MW; of this, 684MW was geothermal (534MW by KenGen and 150MW by independent producers). In other words, this source of electricity accounted for about 25 per cent of the nation power.

The total electricity generated by all generators in the country during that year was 11,323 million kWh, or 11,323GWh (gigawatt-hours) and, of this, geothermal contributed 5,033GWh – about 44 per cent.

Of course, this 2018/19 figure is smaller than the 51 per cent mentioned earlier. The latter value was for 2019/20 and was contained in an unofficial report – the official one is yet to be published.

Using this data, we can work out the effective availability of the geothermal generators. This is done by dividing the energy generated (GWh) by the installed power capacity (MW). But, before punching numbers into the calculator, we must ensure we are working with similar units.

We note that 1,000MW = one GW, hence 684MW = 0.684GW. Thus, dividing 5,033GWh by 0.684GW yields 7,358 hours. This is the effective duration that the geothermal generators were operated during the 2018/19 year.

How about the fossil-fuel powered generators? The installed capacity was 807MW which was about 30 per cent of the national total. However, the combined electricity generated was just 1,240GWh, or 11 per cent. The effective availability of these generators was 1,240GWh divided by 0.807MW = 1,537 hours.

What does this tell us? KPLC buys very little electricity from the fossil-fuel generators, despite their high installed capacities.