by Dave Elliott
Africa has amongst the world’s best renewable energy potential globally, given its climate, with solar an obvious choice, hydro already being well established and wind beginning to be taken up. Biomass and, in some areas, geothermal, are also very significant options. However, hydro apart, the continent only just started to exploit these resources. (more…)
By Dave Elliott
Some continue to portray renewables as marginal, with for example, ExxonMobil claiming that their potential is limited by ‘scalability, geographic dispersion,intermittency (in the case of solar and wind), and cost relative to other sources’, and renewables are only likely to make up about 5% of the global energy mix by 2040: www.ft.com/cms/s/0/5a2356a4-f58e-11e3-afd3-00144feabdc0.html?siteedition=uk#axzz33albsQ2B
Most however see renewables as booming, with IRENA looking to 30% or more of primary energy coming from renewables globally by 2030 (www.irena.org/remap). That is the sort of future envisaged, on the way to maybe near 100% of power by 2050, by most who attended the 13th biannual World Renewable Energy Congress, this one at Kingston University, London, in August.
By Dave Elliott
Hydro plants are the largest existing renewable source of electricity, with around 874 GW installed worldwide, providing almost all of the electricity for many developing countries, for example, in 2008, nearly 100% in Albania, Angola, Bhutan, Burundi, Costa Rica, D R Congo, Lesotho, Mozambique, Nepal, Paraguay, Tajikistan and Zambia, as well 60–90% in 30 other developing countries. In addition, it provides nearly all the electricity in Norway, most of it in Iceland, and up to 60% in Austria, Canada New Zealand and Sweden. See http://k.lenz.name/LB/?p=6525.
Since the energy output is dependent fundamentally on the head height, sites that can accommodate taller dams can produce more energy and it is a square law: double the head gives you four times more energy on average. So in energy terms at least, the bigger the better, and trapping a large mass of water in the reservoir behind the dam will help to give a guaranteed supply, although there will be cost trade-off and site limitations.
The energy source is ultimately solar heat, which drives the hydrological cycle, but since that is climate and weather related, the energy resource at any particular location and time can vary. Indeed, with decreased rainfall in some areas in recent years, output from some hydro plants has fallen. This is likely to get worse with climate change.