Text 5. Solar energy

Solar energy is energy from the Sun in the form of radiated heat and light. It drives the climate and weather and supports life on Earth.

Solar water heaters heat swimming pools and provide domestic hot water. In agriculture, greenhouses grow crops and photovoltaic-powered pumps bring water to animals. Evaporation ponds find applications in the commercial and industrial sectors where they are used to harvest salt and clean waste streams of contaminants.

Solar distillation and disinfection techniques produce potable water for millions of people worldwide. Solar cookers and large solar kitchens concentrate sunlight for cooking, drying and pasteurization. More sophisticated concentrating technologies magnify the rays of the Sun for high temperature material testing, metal smelting, and industrial chemical production. A range of prototype solar vehicles provide ground, air and sea transportation.

Earth continuously receives 174 PW of incoming solar radiation (insolation) at the upper atmosphere. When it meets the atmosphere, 6 % of the insolation is reflected and 16 % is absorbed. Average atmospheric conditions (clouds, dust, pollutants) further reduce insolation traveling through the atmosphere by 20 % due to reflection and 3 % via absorption. These atmospheric conditions not only reduce the quantity of energy reaching the earth's surface, but also diffuse approximately 20 % of the incoming light. After passing through the atmosphere, approximately half of the insolation is in the visible electromagnetic spectrum with the other half mostly in the infrared spectrum (a small part is ultraviolet radiation).

The absorption of solar energy by atmospheric convection and evaporation and condensation of water vapour powers the water cycle and drives the winds. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. The conversion of solar energy into chemical energy via photosynthesis produces food, wood and the biomass from which fossil fuels are derived.

Solar radiation along with secondary solar resources such as wind and wave power, hydroelectricity and biomass, account for over 99.9 % of the available flow of renewable energy on Earth. The flows of solar energy in the environment are vast in comparison to human energy needs.

Text 6. A general evaluation of the region's hydroenergy resources

Hydroenergy technologies, are highly developed and widely employed at the present time. Hydro energy resources are capable to supply the energy market with guaranteed capacities of energy available at competitive prices like hydroelectric power installations in Russia's Siberia or the major hydropower plants in China or Brazil. Hydroenergy covers approximately 20 % of the global energy demand and is the main power source in more than 30 of the world's countries. For two thousand years of its development, hydro power has achieved considerable levels of energy efficiency, advancing from the wooden water wheel with a performance efficiency rate of 10 % to the high-speed hydroturbine with efficiency rates reaching 95 %.

The Kola Peninsula has more than 1000 kilometers of coastline. A complete evolution of ocean waves along the coasts of the Barents and the White Seas showed significant supplies of wave energy, its concentration and transmission represent a great difficulty because of the severe climatic conditions.

Hydroenergy has been harvested for more than 70 years on the Kola Peninsula. Six major rivers of the peninsula are harnessed by 17 hydroelectric power plants, which supply more than a third of all electric power consumed in the region. At the same time, the region abounds in small rivers, where mini- and micro-hydroelectric power plants could be built to make a significant contribution to power supply in remote and isolated areas.

Flowing water creates energy that can be captured and turned into electricity. This is called hydropower. The most common type of hydropower plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydropower doesn't require a large dam. Some hydropower plants just use a small canal to make river water to flow through a turbine. Another type of hydropower plant – called a pumped storage plant – can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.

The technology needed for full-scale commercial production of power installations operating on energy from the sun, wind, small rivers, tides and surface waves has made great advancements. In such countries as Germany, Spain, the US, and Denmark certain branches of the non-conventional energy sector have become competitive in comparison with their traditional counterparts, and the scope of their development is now commensurate with that of the conventional power industry.

The particular quantity of hydroenergy resources that can be used by hydroelectric power plants for the generation of electric power is called "technical resources". The technical potential is always smaller than the entire theoretical potential because, for various reasons, not all river stretches can be used for the construction of hydroelectric power plants. Especially in densely populated areas considerable volumes of water are also collected from many rivers to cover other needs than producing energy.

Дата добавления: 2015-08-03