The potential to produce electricity from wind turbines in South Africa is significantly greater and more widely spread than initially thought. This was the finding from a study undertaken to quantify the combined effect of wind and solar energy resources in the country.
The overarching objective of this study was to increase the fact base and the understanding of aggregated wind and solar photovoltaic (PV) profiles in South Africa for different spatial distributions of a hypothetical wind and solar PV fleet. The study outputs can serve as input into South African energy-planning processes such as the Integrated Energy Plan (IEP), the Integrated Resource Plan (IRP) for electricity, strategic grid planning, the Transmission Development Plan (TDP), wind and solar PV Strategic Environmental Assessments (SEAs).
The study results show that across South Africa, solar photovoltaic (PV) and wind resources are good enough to be able to produce globally competitive solar and wind power and that over 80% of the land mass has enough wind potential to achieve a 30% average annual load factor. The load factor is a measure for the average utilisation of wind turbines. In countries like Spain and Germany, which are known for their good wind resources, actual average load factors of the entire wind fleets are 25 – 27% and 20 – 23%, respectively. The ‘good wind’ resource is not restricted to the Cape area, as was previously thought, and therefore, wind plants can be established almost everywhere in South Africa.
The results also indicate that wind and solar PV installations can provide a smooth power output when the power plants are dispersed over a large area. Consequently, short-term fluctuations in the combined aggregated power output can be avoided almost entirely by spreading solar PV and wind power plants across the country. This, in combination with the cost competitiveness of wind and solar PV, means that these two energy sources can economically and technically supply bulk power to meet large parts of the country’s electricity requirements.
Furthermore, the results indicate that power output from wind and solar PV plants do not happen at the same time, they complement each other, which benefits the power system. Solar PV output is higher during the day and wind output is higher in the evening, which is ideal for meeting the evening peak load.
The results of this study will be used as input to South Africa’s strategic grid plans and the Transmission Development Plan. The high-quality, high-resolution wind and solar PV resource data is already being used in the modelling of the revision to the Integrated Resource Plan. The datasets have been made available to the public.
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The challenge: Incorporating renewables in energy systems
The shift to renewable energy is a gradual process and to minimise the risk of costs and grid instability, the incorporation of sources such as solar photovoltaic (PV), wind and biogas needs to be carefully planned. An integrated system will require cost-effective components and an optimal regime to dispatch different sources at different times.
Formal comments on government’s Integrated Resource Plan
The CSIR made a formal written submission to the Department of Energy as part of the public consultation processes to inform government’s Integrated Resource Plan. Based on power system simulations, this plan is meant to provide the electricity generation mix for the country until the year 2050. The department published the draft plan in the Government Gazette for public consultation on 25 November 2016. The CSIR participated in public hearings and its submission indicates that the country can provide cost-effective and reliable electricity supply via solar photovoltaic, wind and flexible generation sources, such as natural gas, up to the year 2050.
Developing solar PV plants in Pretoria
Several research projects flowed from three solar PV plants that were installed on the CSIR’s campus in Pretoria from 2015 to 2017. The three solar PV plants have a 1 008 kW power output and marked the start of a journey to an energy-autonomous CSIR campus.
Researchers developed a model of the CSIR’s campus grid using power system analyses software, creating a real-time digital simulator that models the solar output of the PV plant. It allows them to study the behaviour of the campus energy grid, to detect and mitigate potential risks to power supply and to proactively plan future grid developments, such as determining the impact of installing new PV plants on campus buildings.
Modelling for best performance
The researchers also developed a mathematical model that can be used to analyse energy demand and energy generation from different sources to inform the best way to dispatch the sources at hourly and sub-hourly resolutions. This type of modelling helps to determine the best technically possible performance from an energy system. The next step is to integrate this model with the real-time digital simulator.
Developing a campus energy plan
Another CSIR study aims to create an integrated energy resource plan for the campus, similar to what was done for government. It takes into account all possible energy generation sources such as PV, wind and biogas to determine the least-cost generation mix, while taking into account demand-side options like flexible load, battery storage and electric vehicles. This model serves as a blueprint of what can be applied to other campuses, institutions and municipalities to assess future energy systems of different sizes. Initial results have been generated and the model was used as a basis for drafting a CSIR Pretoria campus integrated resource plan for the next five years.
Sharing lessons learnt
The CSIR engaged with various municipalities to share knowledge gained from establishing the solar PV plant and trying to become energy-autonomous. The organisation provided training on its procurement approach to the City of Cape Town and Ekurhuleni.
Ekurhuleni used this methodology to procure some of its own solar PV assets. The CSIR has also engaged with the City of Tshwane regarding its sustainable energy plans.
The South African Local Government Association took note of these engagements and has requested that this training be adapted and made available to all interested municipalities. The Deutsche Gesellschaft fur Internationale Zusammenarbeit has expressed interest in funding training programmes underpinned by CSIR expertise. Engagements with Transnet, which is also looking to procure solar PV assets, provide a suitable pilot opportunity for the CSIR to see how the training service could be rolled out.
Helping others with long-term planning
The CSIR was commissioned by the eThekwini municipality to develop a long-term sustainable energy plan in line with the municipality’s climate change goals. eThekwini has since also requested two studies that investigate the use of bioenergy and the feasibility of developing a regulatory incentive for small-scale embedded solar PV systems for the residential housing sector. The CSIR is also assisting the City of Cape Town with its long-term energy planning.
A bioenergy plan for KwaZulu-Natal
The KwaZulu-Natal Department for Economic Development, Tourism and Environmental Affairs commissioned the CSIR to develop a long-term strategy to grow the bioenergy sector in the province, thereby boosting the creation of new industries, jobs and offtake markets for the biomass resource in the province.
Photovoltaic testing facility
Incorporating solar power into an energy system requires a good understanding of the electrical output that the latest panel technology and weather conditions allow. CSIR researchers completed a study to scope an outdoor and indoor solar photovoltaic testing facility, in collaboration with the South African Bureau of Standards. The technology will comprise a set of test bits mounted on panels to measure the electrical output of panels over time. It will be used to do verification testing for imported and locally manufactured modules.
This will support local energy providers and solar photovoltaic manufacturing industries. The facility is expected to be operational within a year.
Developing wind forecasting techniques
The ability to forecast wind speed is becoming more important as South Africa adds renewables to its future power system. CSIR researchers are building local capacity to incorporate wind speed forecasts that rely on mathematical algorithms.
An earlier study in which the CSIR partnered with Germany’s Fraunhofer Institute for Wind Energy and Energy System Technology managed to quantify the combined effect of solar and wind energy sources in South Africa and concluded that it is a viable source of renewable electricity.
South Africa has abundant wind and solar resources, but these fluctuate naturally and continuously. It is important to understand this variability in the context of a stable power system for the country.
Wind patterns are fairly consistent from year to year, but over shorter time scales, such as days and hours, it is difficult to predict. Predicting wind speed a few hours ahead of time would enable better estimates of potential wind electricity production and allow for better planning to balance energy production from different sources.
One of the renewable energy projects of the South African National Energy Development Institute is to map wind resources in the country to produce the Wind Atlas for South Africa (WASA). The atlas contains a large quantity of data that researchers in mathematical modelling can use to find trends in wind patterns.
CSIR researchers used machine learning techniques on wind data from Alexander Bay in the Northern Cape to see if they could forecast wind 1 to 24 hours ahead in hourly intervals. They tested several machine-learning regression algorithms and all algorithms improved on a benchmark forecast previously set. The researchers are adding atmospheric readings from the WASA, for example, air temperature, relative humidity and wind speed direction.