The Projects
Mapping a path to renewables baseload
In the arid north-western region of Southern Africa, where the unforgiving sun and wind hold court with striking predictability, the earmarked Wolmaransstad energy scheme awaits. It is a mammoth undertaking. One that needs to be negotiated in multiple phases.
To put things in perspective; the scale of this project is 10 times larger than any hydro-pumped storage scheme ever attempted. However, in times of crisis ordinary will not serve up what is required for transformative solutions. This is the time for entrepreneurs with big ideas to emerge and lead the way.
Given the large scale of the project it is planned to approach it in stages, with a trial site that will prove the viability of the seawater PHES solution, that will lead to a scaling project of increased reservoir sizes teamed with new renewables builds that will scale up the renewables baseload over time.
The setup for the generation of hydroelectricity is installed in the areas where the kinetic energy of water is very high, like in hilly areas. The kinetic energy of water can also be improved by adjusting topographic relief of the area or by constructing the dams to control the flow of water. The hydroelectric power generation setup can also be installed near the ocean by stabilizing the relief accordingly.
In the areas near the oceans, a particular type of hydropower generation system can be created that is known as pumped storage plant or hydro pumped storage. In this system, water is circulated among two reservoirs, one which is higher than the other. This system is also equipped with a series of water pumps.
When the energy demand is low, the excess of energy is utilized in pumping the water from the lower reservoir to the higher one. As the energy demand increases, water is allowed to flow from the upper reservoir to the lower one. Hence the kinetic energy is produced, which is utilized in generating electricity, which is then supplied. Pumping stations are kept off during times of high energy demand
Figure 1: the comparison in size between the large and small dams.
In Figure 1 we can see the comparison in size between the large and small dams. The smaller one has a 11GWh capacity while the larger one has 986GWh of capacity. There is a plan for scaling up the larger one from two intermediate sizes too. The smaller dam is closer to the sea and should be quite a bit cheaper to build due to substantially shorter headrace. With both dams we are using naturally formed salt pans as our basins resulting in less dam wall building for equivalent capacity.
The first stage
The first stage dam is designed to be small enough to attract private sector investment to get it built. With 11GWh of storage capacity it would be useful to run 250MW to 500MW of nameplate capacity which would be supported on the planned 400KVa Eskom lines in the area.
Figure 2: Planned project
This dam has two 25 metre walls and a canal that links the main body of water to the top intake which is 1.5km from the ocean. This dam has a head of 140m above sea level with 11GWh of capacity. The plan would be to have a couple of headrace pressure pipes linking it to the ocean.
This dam has a head of 140m above sea level with 11GWh of capacity. The plan would be to have a couple of headrace pressure pipes linking it to the ocean. Some clever design will be needed to manage the ocean side intake to avoid sand build-up and ingress into the lower intake. The marine environment would require a higher amount of high quality stainless steel to be used throughout the machine room to avoid corrosion and biofouling. On the electrical side, off-peak power can be brought in through the nearby planned 400 KVa lines. An examination of the wind performance in the local area suggests the possibility of building 100MW of wind power on the adjacent hills that could also provide input power for storage.