Keeping in touch thanks to polymers

“Cleanliness” is not the only benefit offered by renewable energy. In the poorest countries, renewable energies are often one of the only means of bringing electricity to many villages located miles from the traditional grid.

Wind turbines take to the skies

Many ongoing projects are based primarily on wind technology, such as that of the Massachusetts Institute of Technologies (MIT). Two former students of the prestigious Institute came up with the idea of sending micro-wind turbines to an altitude of 300 m, by housing them in the middle of a cylindrical balloon inflated with helium. Their flying wind turbine is above all an alternative to petroleum-powered generators, and they have designed it to supply electricity to sites that are far from the electricity grid. Indian industrial group Tata, known for its automobile production and as a leader in the development of wind energy projects in India, believes in the concept and is financially supporting the American start-up.

A first prototype has already been tested at 150 metres above the ground, in winds travelling at 70 km/h. The tests are very encouraging. As for yields, they should be quite good since the winds at an altitude of 300 m are stronger and above all more constant. The balloon is made of PVC, a polymer that is well known for its strength and watertightness and which is, above all, easy to recycle. The wind balloon is inflated with helium and fixed to the ground with cables. Gone are the days of large, unsightly masts, as the wind turbine is almost invisible… as long as you don't look up.

Integrating a wind turbine into a helium-filled PVC envelope could be one of the solutions that could make unsightly wind turbine masts a thing of the past.

Other start-ups have also tried their hand at this, developing equally daring concepts. This is the case of Makani, which made headlines by proposing a wind turbine solution suspended from a sail that looks a bit like a kite. The sail is rigid and consists of an ultra-light composite frame on which a vinyl film (PVC) is placed.

Mounting wind turbines on a composite wing is one of the solutions currently being tested.

This type of fabric has long been used to make the wings of small single-engine aircraft. The advantage of this project over the balloon is the aerodynamics of the wing, which can be forced to circle around its axis. This perpetual motion increases the apparent wind speed and thus the rotation speed of the wind turbines. The faster they turn, the more energy they produce...

Supported by Google with a great deal of communication, this ambitious project was recently abandoned; more for economic reasons than because of its energy performance. However, the idea has not been abandoned entirely because oil giant Shell is also interested in developing the wind turbine. New tests are currently taking place off the coast of Norway. We'll keep an eye on this one. 

Plastics brave the current

The power of the current, whether at sea or in rivers, is also a solution for providing green electricity. Less flashy in marketing terms than its wind or solar cousins, hydroelectricity would benefit from being better known. Continuous, decarbonised and inexpensive, this energy has many benefits to offer, particularly in the design of small generators with a power of less than 20 kW, which can be used in the most remote areas.
New Zealand's PowerSpout is raising awareness of hydroelectricity with a mobile micro-turbine fitted with a polyethylene shell and a mechanism composed mainly of polyamide parts. Suitable for low water flows (from one litre per second), this generator provides a power of one kilowatt. Installing it on rivers with sufficient flow would be a very interesting solution for supplying electricity to many villages on the African or Asian continents.
Aquakin, a German start-up that, used this same technology to develop a micro-hydro power station for the home. It too is made of plastics. The flat turbine made of polymer-based composite materials can be moored near dykes in shallow waters; thanks to plastics, it is resistant to corrosion by the sea. It can produce around 160,000 kWh per year, which is equivalent to the consumption of around 30 households.

Germany's Aquakin designs portable mini tidal turbines that are ideal for charging a telephone, for example. This is an attraction solution for certain countries where part of the population is still cut off from the electricity grid.

The young company has also designed the Blue Freedom, a lighter model which is in fact a portable 'charger'. Once immersed in a stream, this Frisbee-sized plastic generator weighing 400 grams generates a power of 5 W that can be used to charge a mobile phone in an hour, for example. A solution that could enable the inhabitants of countries like Madagascar, which is rich in white water and where 80% of the population has no access to electricity, to keep in touch with each other.

Less ambitious, its Bavarian rival Smart Hydro Power is marketing a lighter floating turbine. With its mixed high-density polyethylene (HDPE) and aluminium structure and composite blades, it has a more modest power of 5 kW.  

By the light of polymers

In sub-Saharan Africa, the potential for producing solar energy is quite simply phenomenal. With around 3,000 hours of sunshine per year, it has the highest amount of sunshine on the planet. It is estimated that the sun could produce more than 60 million TWh (terawatt hours) per year. In comparison, Asia has a theoretical potential of 37.5 million TWh/year and Europe only 3 million TWh/year. This would therefore be a solution for bringing electricity to the most remote villages. As a reminder, the continent is home to around 600 million people. Awareness of this potential has been growing over the years. In Senegal, for example, the government has set itself the goal of providing access to electricity for all inhabitants by 2025. In other words, very soon indeed.

The continent is ideal for taking full advantage of solar energy, and many African villages are gradually equipping themselves with panels, and more specifically with polymer-based models which are less expensive and much easier to transport.

The wind is favourable and can be explained by a combination of different factors: political will, the increase in investments by financial backers, the enthusiasm of many start-ups for sustainable energies and, above all, the sharp drop in the cost of photovoltaics, particularly thanks to the thin-film technique (see Part 1), which is used more and more frequently. Here, this is more about modernisation than effecting a transition, and it is not uncommon to come across solar kits in villages. These are simple panels that have been made very lightweight thanks to polymers. They are therefore easily transportable and can be placed and moved according to the movement of the sun. Of course, they are not sufficient in and of themselves to power high-powered machines, but they can provide light and power a television or charge a telephone as soon as night falls, and thus provide inexpensive energy to a population that is still in desperate need of it.