Efforts by developing countries to tap renewable sources of energy run into two typical problems – finding cheap and widely usable technologies; and connecting renewable energy to the main electricity grid.
Europe is ahead on the (not necessarily cheap) technology front. But it too is grappling with the grid connectivity question, discussed at a session at ESOF 2010. The European Union (EU) plans to raise the share of its renewable energy sources in its total energy consumption to 20 per cent by 2020. This has implications for designing, operating and maintaining power transmission networks across and within countries.
Gianluca Fulli, from the European Commission’s Joint Research Council, suggests using high voltage direct current (HVDC) grids – electric systems that use direct current to transmit the bulk of the electricity. Traditionally Europe uses a high voltage alternating current (HVAC) system, but HVDC is preferred for long-distance transmission from large, off-shore plants to the grid inland with fewer losses, says Fulli.
Scientists are addressing storage options for renewable energy. Maria Rosa Palacin, from the Materials Sciences Institute, Barcelona, points out that systems of energy production and transmission leave very little room for storage.
Storage systems are crucial, given the fluctuating nature of some of the renewables. For example, Spain’s moody winds can account for 30 per cent of the electricity on a good day and as little as 2 per cent on a bad day.
Palacin says potential storage options include batteries, or a ‘flywheel’ in which the energy is stored as kinetic energy that powers a motor that spins a rotating disc and releases the energy by slowing the wheel down.
Other storage options include a ‘hydro’ option where electricity pumps water from a lower reservoir to a higher reservoir and is released by pumping back to the lower reservoirs; and a compressed air energy storage system where the electricity is used to inject air at high pressure into an underground cave and is released through a gas turbine.
T V Padma, South Asia Regional Coordinator, SciDev.Net