Tham khảo tài liệu 'biofuels, solar and wind as renewable energy systems_benefits and risks episode 1 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1 Renewable and Solar Energy Technologies 7 The efficiency of solar ponds in converting solar radiation into heat is estimated to be approximately 1 4 assuming a 30-year life for the solar pond Table . A 100 ha 1 km2 solar pond can produce electricity at a rate of approximately per kWh Australian Government 2007 . Some hazards are associated with solar ponds but most can be avoided with careful management. It is essential to use plastic liners to make the ponds leakproof and prevent contamination of the adjacent soil and groundwater with salt. Parabolic Troughs Another solar thermal technology that concentrates solar radiation for large-scale energy production is the parabolic trough. A parabolic trough shaped like the bottom half of a large drainpipe reflects sunlight to a central receiver tube that runs above it. Pressurized water and other fluids are heated in the pipe and used to generate steam that drives turbogenerators for electricity production or provides heat energy for industry. Parabolic troughs that have entered the commercial market have the potential for efficient electricity production because they can achieve high turbine inlet temperature. Assuming peak efficiency and favorable sunlight conditions the land requirements for the central receiver technology are approximately 1 100 ha per1 billion kWh per year Table . The energy input output ratio is calculated to be 1 5 Table . Solar thermal receivers are estimated to produce electricity at approximately per kWh DOE EREN 2001 . The potential environmental impacts of solar thermal receivers include the accidental or emergency release of toxic chemicals used in the heat transfer system. Water availability can also be a problem in arid regions. Photovoltaic Systems Photovoltaic cells have the potential to provide a significant portion of future . and world electrical energy Energy Economics 2007 . Photovoltaic cells produce electricity when sunlight excites .
