.JPG)
Hydro and pumped storage, CO2 free power from man made lakes..
Hydro generating systems have been in use for many years and consist of river water captured behind a dam at a high level, which flows to lower level driving a water turbine which drives an electrical generator.
The energy which can be extracted by electrical power in any scheme depends on the quantity of water flow and the height it can fall. Considerable land space is required for collection of water. In a pump storage scheme, which should work well with the intermittent green sources of power, solar wind etc, the power potential is considerably more for the same take of land space,
Examples of large hydro power stations worth visiting are at the Hoover Dam in the USA (2000 MW) capturing the water from the Colorado river or the Aswan High Dam in Egypt (2100 MW), using the Nile river water caught in lake Nasser or the three Gorges Dam in China see below (18000 MW)(ref 125) or Yacyreta Argentinia (3200 MW)(ref130).
Three Gorges Dam in China (18000 MW)(ref125)
Hydro power supplies 16.6 % of world energy (ref 173 April 08) and most of the renewable energy. Small hydro stations (SHP) ie up to 10 MW size, using rivers canals and streams, account for 37,000 MW worldwide today which should rise to 55,000 MW by 2010.
A disadvantage is that the lakes for hydro schemes often result in CO2 and methane release due to vegetation drowning and decay at the bottom of the lake. This could exceed the same generation due to burning fossil fuels. Peat bogs.
Pump storage - energy islands - Sea raiser.
A pumped storage power station has a much larger capacity on the same site than a hydro station would have. There are two levels of dam. In peak hours, water flows from high to low providing power. At times of low power demand water is pumped back up to the high level. The overall efficiency from electrical power in to electrical power out is around 65%(ref 6). Advantages are that extra power is available at peak times of the day and at low demand periods surplus power from nuclear stations(which like to remain on steady load) is used.
An example is the Dinorwig North Wales 1320 MW (Max generation in 16 secs.)
An 'energy island' is a development of pump storage. A Dutch feasibility study will propose a man made island. Water is pumped out using wind power, when available, or surplus power and runs back when power demand high via turbines. This will enable the Netherlands to reduce carbon emissions by 30% by 2020.
Sea raiser is a plan to use wave energy to pump water to a high resevoir on land. This will enable flow back to the sea with power drawn from turbines when demand high and /or in calm conditions.
