One of the difficulties with national electricity grids is that they don't store power, they just move it around (very inefficiently). What you don't use, you lose. There are ways to store it, such as by using excess power during periods of low demand to pump water into a storage reservoir that can be used to run a hydroelectric generator during periods of high demand. The City of Cape Town is using this method with the 400 MW Steenbras Dam pumped storage scheme, saving the city R2 million a month. And there's an even bigger 1000 MW pumped storage scheme in KwaZulu Natal.
There have also been proposals to store power as compressed air, and hydrogen fuel cells are a more high-tech method of storage. Whatever the technology, a significant benefit of storage is that it eliminates the need for building extra power stations just to meet short periods of peak demand. New storage technologies could also open up whole new markets for electricity, including vehicles that don't rely on liquid fuels. Biofuels reduce reliance on fossil fuels, but they still produce emissions and they have introduced new concerns over food security. Running vehicles on electricity (stored in some intermediate form) eliminates both these problems if the electricity is generated from a low-carbon source.
This could be a great way to overcome one of the shortcomings of generating electricity from the wind or sun: the wind and sun don't always show up when they're needed, so store their power for later use. But to make these sources reliable, on a significant scale, requires wind and solar farms to be distributed all over the place. To avoid environmental impacts, or to find enough land, many of these sources will need to be far from where the power is needed. This raises the challenge of overcoming the inefficiencies in transmitting power over long distances.
Enter a group of Norwegian companies, already building a multinational high-voltage DC grid that can transmit power more efficiently. (Norway also happens to be a country with large hydroelectric capacity.) I strongly believe we should be promoting micro-generation of electricity - distributed over local grids - but it sounds possible that an international DC grid combined with storage would allow the development of power from renewable sources at an industrial scale, which may be a necessary part of a broad strategy to slow the growth of fossil-fueled or nuclear power plants.
It is commonly assumed that electricity generation from renewable sources isn't feasible at a scale that can produce a significant reduction in carbon emissions, but Irish company Airtricity believes that high-voltage DC transmission lines can make possible a wind farm in the North Sea that could generate 10 gigawatts, and that's not small-fry. The cost would be 17% higher than building the same capacity using coal-fired plants, but with the obvious saving in carbon emissions. Carbon credits could offset at least some of that extra capital cost, but with zero fuel costs for a wind farm, the extra upfront costs should be easy to stomach. And then there's all that sun in the Kalahari Desert...
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