Report Highlights Risks From Inaccurate Irradiation Data To Solar Projects In Africa

A recent report developed by a solar electricity provider to African enterprises, CrossBoundary Energy (CBE), says that Data irregularities in estimating solar production can have significant impacts on both technical teams and solar buyers.

Solar production/ solar irradiation is the measurement of how much sunlight shines in each location and therefore how much electricity a solar array can produce. And this is a key design factor for solar customers, suppliers, and investors likewise. But, irregularities in such estimates in Africa could cut energy savings for commercial and industrial (C&I) solar buyers and reduce investment returns for developers and investors.

Declining solar equipment costs continue to drive African businesses toward solar energy solutions. Solar developers rely on solar irradiance measurements to predict how much power the plant will produce daily and annually. This affects the solar installation’s design, the price for solar-charged to C&I clients, and the expected return to investors from solar investments.

The actual irradiation is measured by the ground-based measurement systems – tended to deviate from the satellite data widely accepted as accurate for making calculations of long-term energy production during solar design, says CBE after analyzing its own portfolio of solar projects in Africa. The deviation between actual measured and estimated irradiation – referred to as ‘relative mean bias deviation’.

“Due to Africa’s diverse topography, we found that sites outside of major cities experience even higher biases; satellite solar irradiation estimates for sites snuggled in highlands, valleys, or next to lakes can be biased by up to 20%. This could result in up to 20% lower energy savings for solar customers, with businesses outside of major metropolitan areas most at risk,” the report said.

The report suggests two main ways to estimate solar irradiation and that are; satellite and meteorological models, and ground-based measurement.

With satellite and meteorological model estimation, the accuracy is limited to the accuracy of the satellite imagery and the ability of the satellite.

Ground-based measurements, on the other hand, record the actual solar irradiance data on the earth’s surface. Accurate data from the ground-based measurement system is used to validate the disparity between actual and estimated irradiance is reduced.

The complementary relationship between these two approaches makes solar irradiation estimation practically feasible for any point on the earth.

According to CBE, the distribution of ground-based validation sites is clustered in Europe, South Africa, and overall in temperate regions, with few and sparingly distributed stations serving other parts of Africa, particularly in the tropics.

Consequently, Solar buyers and developers bear the consequences of solar production overestimates. As kWh Analytics’ inaugural 2020 Solar Generation Index report noted, “If you blindly trust a production estimate, on average, you are likely overestimating a site’s production.” Considering the higher irradiation data biases seen in Africa, African solar developers and their clients could find themselves facing even greater impacts.

The report mentioned two key risks that solar developers in Africa face as a result of inaccurate solar production estimates: failure to meet portfolio investor returns and under-delivering on the expected savings to solar buyers. The report numbered out that 3%-5% Bias identified in solar irradiation measurements in Africa, 5%-20% Lifetime savings lost for solar buyers due to higher-than-expected electricity costs from overestimation, and 1%-2% Decreased IRR for project developers from overestimated asset productivity.

Also, a solar developer’s failure to meet the modeled solar production output also reduces the effective savings for C&I clients. CBE also suggested that solar buyers, data providers, and developers should better interrogate irradiation data and collaborate on long-term solutions. They should seek to interrogate multiple solar irradiation data sources to evaluate a realistic range of solar irradiation and, use P90 over P50 values when estimating solar productivity. This will help to ensure that projections are not overly optimistic and avoid misrepresentation of project profitability.