generation capacity can be built on a much larger scale offshore, and solar generation potential increases with proximity to the equator. Across offshore and onshore wind, China (91,424MW), the USA (61,091MW), Germany (34,250MW), Spain (22,959MW) and India (20,150MW) formed the top five for installed capacity at the end of 2013, according to the Global Wind Energy Council (GWEC). Northern Europe leads in offshore wind. GWEC reports that, in 2012, 4336MW of offshore capacity was installed in 56 wind farms across the continent, with most of the world’s offshore capacity located in the North, Baltic and Irish Seas and the English Channel. China has set itself dramatic goals to catch up, with a target to install 5GW of offshore wind capacity by 2015, and 30GW by 2020. However, cost remains a barrier worldwide, as offshore technologies are still developing. Africa is endowed with vast renewable power resources that could supply demand throughout the continent and far beyond. Northern Africa is particularly bountiful, as its latitude gives it one of the world’s highest solar and wind power potentials and high wind speeds are found on the Atlantic and Red Sea coasts and in parts of the Sahara Desert. However, lack of investment and geopolitical inconsistency are Africa’s fatal weaknesses, and have historically prevented it fulfilling its potential as a generation powerhouse. Smart grids, also known as smart networks, are essential to marry together these new renewable generation sources, given the intermittence and unpredictability of wind and solar and the wide range of generation capacity to come on line – from microgeneration to enormous new schemes. Within a smart grid, sophisticated control systems enable the easy redistribution of electricity to achieve a better power balance across the grid, and storage facilities such as flywheels, batteries, fuel cells, hydroelectric pumped and other storage provide power reserves that can be mobilised almost immediately in times of intermittent supply. By absorbing excess power from the grid, storage facilities also help to regulate grid frequency.
Dedisa substation, South Africa IMAGE: ESKOM
Smart grids are also revolutionary in the way they reorder the power grid by allowing consumers to transfer power back into the grid from their own microgeneration such as small-scale wind and solar equipment, and storage sources such as vehicle batteries. Providing this reversed flow is one of the biggest areas of upgrade work needed to make typical power grids ‘smart’. Ultimately, smart grids provide flexibility for the network to use of all forms of power generation at any location.
The Importance of Resilience Opportunities for flexible power
trading on a grand scale will come from long distance and subsea interconnectors using high- voltage, direct current (HVDC) transmission. HVDC offers a more practically feasible, higher stability means of transmitting power across long distances than more common alternating current (AC) transmission, which currently dominates electricity grids as it
‘Africa is endowed with vast renewable power resources that could supply demand throughout the continent and far beyond.’
164 GLOBAL OPPORTUNITY 2014 | ISSUE 01
is more economic and convenient to operate over short distances. New voltage sourced converter (VSC) HVDC technology is more flexible than its predecessors and is becoming more affordable, but HVDC is still not a cheap option. A number of international interconnectors already exist, with the current longest link in China. The 2,071 km long Xiangjiaba– Shanghai HVDC system exports hydropower from Xiangjiaba Dam to Shanghai with a capacity of 6400 MW. Brazil is currently building a 3500MW-capacity line extending 2096km between Xingu and Estreito. However, both these lines are based on line commutated converters, which effectively cannot accommodate more than two terminals. Multi- terminal and networked HVDC transmission systems would require the use of VSC converters, which can potentially be configured into multi-terminal networks, and direct current (DC) switching devices which are currently being prototyped and tested by manufacturers. DC switches would permit a DC network, rather than the present simple bilateral DC links.
If and when DC networks are fully developed, they could come to enable a large scale transmission network, permitting international power trading through a super grid stretching through Africa, Europe and Asia. Many countries harbour a goal of domestic self-sufficiency for fear of power supply being used for political leverage, but in fact
global-opportunity.co.uk
POWER
|
MOTT MACDONALD
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