November 17, 2018


Marco van Dijk

1on1-the-weekly Heeding the call by the government on big private firms, municipalities and other independent players to consider generating their own electricity to relieve pressure on the overburdened Eskom,  Bloemwater this week commissioned a new conduit hydropower plant with capacity to generate 96kW of electricity, enough to power the bulk water supplier’s head office in Bloemfontein. In an interview at the commissioning of the power plant on Wednesday, The Weekly’s Martin Makoni sought to establish from Marco van Dijk – who is with the University of Pretoria’s faculty of engineering and is one of the brains behind the project – the potential of this technology to help end the country’s perennial power problems. Excerpts: 

Conduit hydropower technology is not well known in the country and it is particularly new to the Free State. What exactly is this technology and how does it work?
Basically, conduit hydropower is energy produced by tapping into canals, water pipes or other man-made structures that carry water and fitting electric generating equipment in order to generate power in the pressurised pipes or conduits. There are five areas where there could be potential to generate power in the water supply and distribution system, namely: at the dam, water treatment works, inlets to reservoirs, along the distribution networks and treated effluent.

The important thing is to ensure that there is adequate elevation to allow the water to move at high speed in order to be able to turn the turbines and generate electricity. This form of energy is clean and it enables users to generate hydroelectricity for on-site use and in some cases to supply energy to other locations or even to the national electricity grid depending on the location type and size of installation.

How will Bloemwater benefit from this hydropower plant?
Bloemwater should save about R50 000 per month in electricity bills. The figure could fluctuate because it depends on whether it is summer or winter. This pipeline that supplies Bloemwater here, the main water reservoir actually has potential to generate electricity at two points. That is here at Brandkop and Uitkijk. But because this is a pilot project, we only developed 96 kilowatts (kW). We arrived at that figure because that is what Bloemwater needs here at the head office. So everything you see here is being powered by that hydropower plant.

There is potential to go up to 250kW. Excess electricity cannot be put back into the grid. So you should only produce what you need. There are plans to increase generation capacity because Bloemwater has grown over the years. At the moment we are only tapping into 35 percent of the water coming to this site. We could install more water pipes and generate electricity.

Does this new development mean Bloemwater is now permanently off the national grid or it will still need some back-up from the national power grid?
Bloemwater has been getting its electricity directly from Eskom but now they are generating their own power. Bloemwater is not entirely independent but they are going in that direction.

They may need back-up from Eskom if they turn off their equipment for service and maintenance or if there is a fault. And because Bloemwater is expanding, the 96kW might not be enough, meaning they might have to supplement it with Eskom power. But there are also plans to install another pipeline to run parallel to the current one and that would mean increased generating capacity.

The electricity feed that has been going to Bloemwater will obviously be utilised by other consumers, thereby relieving the pressure on the grid, all things being equal. About how many households do you think could benefit from this electricity?
Electricity consumption varies with seasons. In summer, 96kW could serve at least 200 households. The figure would obviously come down in winter because of the high demand for heating. But it largely depends on the sizes of the households. You may actually feed a couple hundreds more of houses with 96kW.

What is the capacity of conduit hydropower technology? Can this technology be used to generate electricity on a larger scale and, perhaps, help end South Africa’s power problems?
It is always important to note that the water has to move from a higher place to a lower point in order to have enough force to turn the turbines. This technology cannot be used effectively if the water is not moving fast. It works very well when used on a small scale because of the limited amounts of water moved by the pipes. But it can be used to cover areas if more conduit hydropower plants are built in different water channels. It could be quite effective in alleviating power shortages.

Where else in the country this technology is in use or being considered?
South Africa does not have particularly good conditions for hydroelectricity mainly because of its flat terrain but at the same time large quantities of raw and potable water are conveyed daily under either pressurised or gravity conditions over large distances and elevations. Several potential conduit hydropower sites have been identified, investigated, constructed or are actually operational around the country. Examples include Rand Water, Mossel Bay, Lepelle Water, Amatola Water, Bloemwater, eThekwini Municipality, City of Tshwane, Johannesburg Water, City of Cape Town, Eskom and Midvaal Local Municipality. Feasibility studies for more conduit hydropower projects are being carried out.

In terms of impact on the environment, how does this type of technology fare in comparison with other methods of generating electricity?
The technology requires minimal civil works, meaning the construction takes less time.

There are practically no negative environmental or social effects as you are using water already being transported and releasing it without polluting it or the environment.
The power stations also have a long lifespan, operating for more than 50 years.

Hydropower stations are also very efficient, among others.

Vandalism by people looking for scrap metal is a major problem facing Eskom and other power distributors. How susceptible is this form of energy to sabotage?
Your power generating equipment is installed in already existing infrastructure and it is on a smaller scale. You can install it in a place that you can easily monitor so that you can spot intruders on time and protect your equipment. You are constantly in charge of your equipment. It’s a big spin-off.

You say studies on the feasibility of conduit hydropower plants are underway at various sites in the country, but what is the country’s overall potential to produce electricity through this means?
We already know of about 40 megawatts (MW) that have been investigated and there is a potential 60MW still being investigated. We should get at least 100MW through conduit hydropower. And in the river systems in the Eastern Cape there is a possible 40MW. Dams, by law, are supposed to release water to the environment, so we are saying instead of just letting the water go, why not install turbines on every dam and generate some energy before releasing the water? There are plenty of opportunities that need to be explored. The farming communities can also benefit from this.

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