Renewable energy streetlights could change lives

In less than five years, the Twerly has gone from a post-graduate research project to a commercial product thanks to engineers at eNtsa, a research entity in the NMMU’s engineering faculty.

The brains behind the original concept belong to Dr Russell Phillips, associate in mechanical engineering at NMMU. He supervised the research project that developed a vertical axis wind turbine (VAWT), and it was his vision that led to the development of the hybrid streetlight.

The Twerly is hybrid because it can use two different renewable energy sources. One is a standard 140W photovoltaic panel, while the other is the VAWT. These two power sources provide power for a standard LED streetlight.

The VAWT is a type of turbine known as a Savonius rotor, after Finnish inventor Sigurd Johannes Savonius, who developed the concept in 1922. It differs from the large propeller-type wind turbines in the way it is powered; the VAWT is better suited to low wind speeds and wind from different directions.

According to Etienne Phillips, eNtsa’s project manager for product development, the VAWT developed at NMMU is silent and can harvest power at extremely low wind speeds. The latter is thanks to some electronic wizardry that makes the energy conversion more efficient than other VAWTs on the market.

That’s not the only engineering feat that the makers of the Twerly can boast about. Etienne Phillips says that the design goal was for the Twerly to last three full nights on a charged battery with both power sources switched off. As it stands, the commercial model can last two and a half nights, but according to Phillips, it will be difficult to get beyond that without adding a third battery. It is achieved by a flexible new power control system, as well as sophisticated monitoring tools built into the Twerly.

Every Twerly tracks its VAWT and solar panel output, battery charging, and LED power use. On top of this, each one has a wireless transceiver and a unique address, which means that groups of Twerlys can form networks that can be connected to a cloud-based dashboard for easy monitoring. With just one connection to the internet per group of lights, says Nik Jankovich, “we can remotely track, manage and monitor the outputs of the VAWT, batteries solar panels and light of every Twerly that leaves the factory.”

Another feature of the Twerly is that it is modular – the electronics allow for one or two solar panels, different sizes of solar panel, more or less lighting, as well as various components like surveillance cameras, wireless hotspots and almost anything else you can think of. The result is a system that can be optimised based on environmental conditions and the needs of the community. And, because the system produces a surplus of energy, the Twerly can be used as an entrepreneurial tool too. Jankovich suggests providing a power source to charge cell phones and laptops in off-the-grid locations, or a WiFi hotspot and network for a community without reliable internet access.

Despite these exciting applications, a business proposition like this is not without challenges. And for the renewable lighting sector, the challenges are diverse, covering environmental issues and the social challenges associated with informal settlements and rural communities, where these lights could have the greatest impact.

The environmental difficulties faced are quite clear – without sun or wind, the Twerly can’t produce power to light up a street, or generate WiFi for internet access. Phillips says that despite the flexible nature of the Twerly, it might just not be feasible, “There are some areas of the country where this just won’t work, where it’s completely unfeasible to keep a light on all night, three nights in a row.”

Wind maps for South Africa are in development as part of the Wind Atlas for South Africa project, and solar maps like this one have already been developed. Together, this data will give a good idea of where the Twerly can and can’t work.

With the ability to adjust the power sources, it would seem that the Twerly will be able to function in most parts of SA. As for surviving high-speed winds, the engineers have got it covered. The Twerly can tolerate up to 300km/h winds (The VAWT won’t be operational, but the light won’t blow over).

The business side of things could present more of a problem. A quick Google search reveals that there are a myriad of simple, solar panel-only LED streetlights available in South Africa that cost between R10 000 and R20 000 each. Jankovich said that the retail price for a Twerly was not set in stone due to installation and logistical costs. However, his estimate at the moment is in the region of R61 500, three times the upper price range of your basic solar LED streetlight.

While this price is quite steep, the Twerly has obvious advantages over a basic Solar LED light. Beyond battery life superiority, the most important advantage is that these lights will stimulate small businesses and entrepreneurs, which could be used to offset the high cost of installation.

According to Ulricht Terreblanche, a Renewable Energy Research Engineer at Stellenbosch University’s Centre for Renewable and Sustainable Energy Studies (CRSES), this is where they can hope to differentiate themselves. He says the Twerly will only be successful with a business model that encourages alternative uses of the technology.

Nik Jankovich agrees. He foresees business opportunities throughout the lifecycle of the Twerly for installation, maintenance and other service companies. In particular, he says, maintenance is important. The Twerly is built to last, as long as it’s taken care of.

There is little doubt that the Twerly can have a positive effect in rural or peri-urban communities that are without electricity or internet supply. It fits in well with the targets of the Department of Energy’s Integrated Energy Plan to diversify supply sources and primary sources of energy, and to promote local technology transfer and job creation. The technology is quite possibly the most advanced in the world.

So, the question is, will we see Twerlys in South Africa in the near future? Jankovich is talking to everybody it would seem – from individual businesses to SANParks to the Nelson Mandela Bay Metro. He says the response is very positive. But at such high cost, and with no guarantee of government buy-in, the answer right now can only be ‘maybe’.