Increasing access to energy is critical to ensuring socioeconomic development in the world's poorest countries.
An estimated 1.5 billion people in developing countries have no access to electricity, with more than 80 per cent of these living in sub-Saharan Africa or South Asia.
The problem is most acute in remote areas: 89 per cent of people in rural sub-Saharan Africa live without electricity, which is more than twice the proportion (46 per cent) in urban areas.
For these people, even access to a small amount of electricity could lead to life-saving improvements in agricultural productivity, health, education, communications and access to clean water.
Options for expanding access to electricity in developing countries tend to focus on increasing centralised energy from fossil fuels such as oil, gas and coal, by expanding grid electricity. But this approach has little benefit for the rural poor. Grid extension in these areas is either impractical or too expensive.
Neither does this strategy help tackle climate change. Power already accounts for 26 per cent of global greenhouse gas emissions and while most of this comes from the developed world, by 2030 developing countries are predicted to use 70 per cent more total annual energy than developed nations.
There is therefore a clear need for pro-poor, low-carbon ways to improve access to electricity in the developing world — solar power could be one such solution.
Place in the sun
The Earth receives more solar energy in one hour than the world population consumes in an entire year.
Almost all developing countries have enormous solar power potential — most of Africa, for example, has around 325 days of strong sunlight a year, delivering, on average, more than 6 kWh energy per square metre a day (see Figure 1).
The Desertec Foundation, a joint German and Jordanian company, estimates that covering just one per cent of global deserts in solar panels could power the whole world.
And yet the countries that receive the most solar energy are often also the ones least able to benefit from it, due to a lack of knowledge and capacity to harness solar power and convert it into electricity.
There are two ways of using power from the sun: collecting its heat (solar-thermal) or converting its light into electricity (photovoltaics).
Solar-thermal devices use 'collectors' — ranging from flat plates put on roofs to parabolic dishes, power towers or solar pyramids used in solar power plants — to absorb sunlight and produce heat.
Solar-thermal devices can be most simply used for heating or cooling but are also suitable for drying crops, pasteurising water or cooking (see Table 1).
Through concentrating solar power (CSP) systems, that use a combination of lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam, they can also be used to provide electricity. The concentrated sunlight heats water to produce steam to drive a turbine, connected to a generator.
Solar photovoltaic (PV) systems use solar cells, linked together in 'modules' (solar panels), to convert light into electricity. They range from a few small cells that can run a calculator to huge solar power stations with thousands of solar panels....