Friday, January 25, 2013

WAZANZIBARI HATUNA HAJA YA UMEME WA TANESCO JUWA TU.

WAZANZIBARI KAMA HUYU DIKTETA HATUJA MTOWA KATIKA NCHI YETU HAYA YOTE YATAKUWA NI NDOTO JUWA JUWA SI DISSELI WA PETROLI JUWA JUWA TU SISI TUTAKUWA NA UMEME WAKUTUMIA NA WAKUWAUZI KENYA,UGANDA NA TANGANYIKA PIA NA MAJI YATAKUWA BURE LAKINI WAPI JINAMIZI LIMETUKA JUU YA KICHA HATUFURUKUTI KILA KUKICHA WANANCHI DUMISHENI AMANI NA UTULIVU NDIO MAENDELEO YATAKUJA YAWAPI MIAKA 50 NI NUSU KARNE SASA.
A large power network with very low electricity losses allows clean electricity to be generated from renewable sources at the most advantageous locations. The type of technology used on site depends on local circumstances, as well as on the wishes of the country concerned and the investors.

In desert regions near the coast, solar-thermal power plants can be combined with seawater desalination so that they not only produce electricity, but also drinking water. Air-cooled solar-thermal power plants combined with water-saving cleaning robots are particularly useful in desert locations inland. Many coastal areas are excellent locations for inexpensive wind power plants. Photovoltaic systems are useful for covering peak mid-day demand, for example from air conditioning systems. Solar-thermal power plants, as well as biomass, geothermal, hydroelectric and pumped storage plants, provide valuable, controllable electricity. This means they can be used to balance out the fluctuations of wind and photovoltaic power, so that more of these variable energy sources can be used in the future electricity mix.



High-Voltage Direct Current (HVDC) transmission
HVDC transmission is a way of carrying clean electricity over long distances to the places in the world which consume large amounts of energy. Around 90% of the human population live less than 3000 kilometers from deserts and could be efficiently supplied with clean desert electricity. The line losses are very low – only around three percent per 1000 kilometers – and the extra cost is only one or two cents per kilowatt hour. This is more than compensated because solar power plants located in deserts are much more efficient due to the longer and more intensive solar irradiation and less winter months. The same is with wind power plants that benefit from stronger and more constant winds at optimum sites. An extended grid and connected backup power plants compensate for fluctuations in renewable energies and downtime in power plants and transmission lines.

There are dozens of lines up to 1700 km long (Inga-Shaba, Democratic Republic of Congo) with capacities of up to 5 gigawatts (Yunnan-Guangdong, China) already in operation around the world. HVDC lines are also used in Europe: Sardinia is connected to the mainland by undersea HVDC cable and there is a whole network of HVDC connections between central Europe and Scandinavia. HVDC lines take up less space than conventional AC power lines and can be laid over long distances underground. This increases public acceptance and means the network can be extended faster. A study by the DLR confirms the positive eco-balance of the transmission lines used for DESERTEC. Wikipedia contains a list of existing and planned lines around the world.

Concentrating Solar-thermal Power (CSP) plants
CSP plants are key to the DESERTEC Concept because they are ideal for utilizing the solar potential of the world’s deserts and supplying electricity on demand. A reflector area of just 20 square meters in a solar-thermal power plant is enough to supply all the electricity one person needs (including electromobility) day and night with no carbon emissions.

Solar-thermal power plants use mirrors to concentrate solar energy in order to heat water and produce steam. This creates pressure, which is used to drive a conventional steam turbine and generate electricity. Solar-thermal power plants can produce clean electricity from solar energy day and night, because heat, unlike electricity, can be stored in large quantities. Heat storage tanks supply energy to the steam cycle at night and especially during times of peak demand. This means that these power plants, when combined with other renewable energy sources, can compensate for the inherent fluctuations of photovoltaic and wind power and thus help stabilize the grid.
At sites near the coast, solar-thermal power plants can use sea water to cool the steam cycle. This way, a collector array designed for a 250 megawatt steam turbine can produce 200 megawatts of electricity and 4 million liters of drinking water every hour through thermal seawater desalination. This method is already used on a large scale at the fossil-fired plant at Jebel Ali in Dubai. At inland sites, air cooling is most suitable – which means that the ideal locations for solar energy can be used, regardless of whether there is a water source. Water-saving brush robots are already successfully used for cleaning the collectors.

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