Focus on clean renewable energy

Clean renewable energy is about us finding ways to power up our homes, offices, factories, machines and technology that don’t burn fossil fuels or irreversibly damage the earth.

This isn’t straightforward, however, because any solution needs to match or better our current and increasing energy demand and use patterns.

Solar and wind are the two main sources of large scale grid-connected clean renewable energy presently being installed in South Africa as part of the Renewable Energy Independent Power Producer Procurement programme. Known by the acronym REIPPP, the programme is a government initiative aimed at encouraging private investment to help develop the local renewable energy sector.

Under REIPP three Concentrating Solar Power (CSP) plants have been built for Eskom near Upington in the Northern Cape with a total energy capacity of 250 megawatts (MW).

CSP plants use rotating mirrors to concentrate the sun’s rays on a central receiver. The thermal energy generated is then stored either in steam or molten salt, ready for transfer.

According to Eskom, over a 20-year operating period, the Upington CSP plants can save 9 million tons of CO2e (carbon dioxide equivalent) emissions from entering the earth’s atmosphere.

Similarly, at Vredendal 300km north of Cape Town, South Africa’s first large-scale wind farm with a production capacity of 100MW should save at least 5 million tons of CO2e emissions during its first 20 years. This wind farm consists of 46 turbines, each generating 2.3MW.

If we look at the global potential energy available from these sources, it’s clear to see that they could easily provide all the power we need.

Current worldwide human energy consumption is around 15 terawatts (TW) or 15 million megawatts (MW) but with the potential levels of energy available from wind estimated at 870 TW and solar at
86 000 TW these are two enormous energy sources that we just need to learn to tap properly.

Clean renewable energy sources typically produce no emissions in energy production, are safe, and mostly designed to be recycleable after their lifetime.

Renewables are becoming some of the cheapest energy production available and getting cheaper every year. What is also good is that they are quick to implement and can start delivering energy back to the grid very quickly thus allowing supply and demand to be quickly balanced. For example the REIPPP projects have typically been delivered on time and on budget in one to two years.

A potential problem with wind and solar, however, is reliability. What if the sun doesn’t shine and the wind doesn’t blow? Also, can they deliver the peak energy when it is needed in the morning and evening? The solution lies in energy storage, and a range of technologies such as batteries already exists or is being improved for this.

Another excellent source of clean renewable energy is biogas, typically a mixture of gases mostly made up by methane (CH4) and carbon dioxide (CO2).

Biogas is a reliable, simple and well-established energy source in use around the world, including South Africa. Millions of households in China, Nepal and India generate and use biogas for cooking and heating but it can also be used for electricity production and even to power vehicles.

Bacteria produce biogas through the anaerobic digestion of organic wastes from humans, animals, and plants in a closed container. The process produces biogas and also leaves behind a nutrient-rich matter called digestate, which is commonly utilised as fertiliser.

Questions:

1. Name the two main energy plants being installed through the REIPPP programme?

2. Where are Eskom’s first CSP plants located?

3. How many tons of CO2 emissions could South Africa’s three CSP plants save?

4. Through what mediums can CSP plants store thermal energy?

5. Where is Eskom’s first large-scale wind farm?

6. What is the energy capacity of this wind farm?

7. True or false: There are
1 million Megawatts in 1 Terawatt

8. Name the two gases most commonly found in biogas

9. What is biogas produced from?

10. Which of these terms relates to an absence of oxygen: aerobic or anaerobic?

Answers

1. Concentrating Solar Power (CSP) and wind
farms

2. Upington in the Northern Cape

3. 9 million tons

4. Molten salt and steam

5. Vredendal in the Western Cape

6. 100 MW

7. True

8. Methane (CH4) and Carbon Dioxide (CO2)

9. Decomposing plants, manure or food waste

10. Anaerobic