Renewable Energy Sources Flashcards

Flashcards about renewable energy sources, hydroelectric power (HEP), wind, solar, biofuels, geothermal and tidal energy.

What are the properties of renewable energy sources that need consideration?

Intermittency, predictability, energy density, ease of storage, application to current uses, environmental impacts, geographical constraints, size of available resource, level of technological development, economic issues.

Why is intermittency a problematic property of some renewable energy sources?

Some resources are not available all the time, so they can't be the only source of energy used. For example, solar power is not available during the night, it's not always windy, and tidal cycles have periods when water is not moving.

How does ease of storage affect the usability of renewable energy?

Many renewables can't be stored unless converted into other forms of energy. For example, solar power or the kinetic energy of wind power. Biofuels can be stored, as can gravitational potential energy in the water in HEP reservoirs.

What geographical constraints affect the use of renewable energy resources?

Most renewable energy sources can only be harnessed where natural processes or geographical conditions are suitable - solar, wind, wave power.

What factors determine whether a country produces higher levels of energy from renewables than others?

Climactic conditions, space to set up, political will, public environmental awareness, and economic factors.

What problematic properties affect solar power?

Intermittency, reliability, and low energy density require very large areas of solar collectors.

Where is solar power most viable, and why?

Dry, sunny deserts with the highest light levels. Systems that concentrate sunlight using parabolic reflectors only work where there is no cloud cover.

What are the two main technologies to harness solar power?

Photothermal solar power and photovoltaic (PV) solar power.

What is the difference between photothermal and photovoltaic solar power?

Photothermal systems absorb sunlight to produce heat to heat water, while photovoltaic systems convert energy in sunlight directly to electricity through the movements of electrons in a semiconductor.

What are the environmental impacts of manufacturing solar panels?

Manufacturing requires extraction and processing of materials like metals, plastics, paints, and silicon. Making PV solar panels produces toxic wastes like silicon tetrachloride and small amounts of cadmium.

What are some new solar power technologies?

Multi-junction photovoltaic cells, anti-reflective surfaces, concentrating Solar Power (CSP) with thermal storage, photovoltaic/thermal hybrid systems (PVT systems), transparent PV cells, heliostats, and self-cleaning panels.

Describe how hydroelectric power (HEP) works.

Gravitational potential energy of rainwater that lands on upland areas can be harnessed as kinetic energy as it flows downhill to generate electricity.

What are the locational constraints for hydroelectric power (HEP)?

Large water catchment area, high total rainfall, evenly distributed throughout the year, low water turbidity, impermeable bedrock beneath the reservoir, low seismic activity, suitable topography, no serious land-use conflicts, close to consumers or electricity grid.

What are the environmental impacts of reservoir creation for HEP?

Dam construction requires large amounts of material like gravel, sand, rock and cement. Extraction, processing, and transport of the materials requires energy, it will flood land, cause the loss of wildlife habitats, farmland, and homes, and produce anaerobic conditions and the release of methane gas.

What are some new HEP technologies?

Low-head turbines, Kaplan turbines, Helical turbines, Micro-hydro schemes, and Large HEP schemes.

Describe how wind power works.

Differences in atmospheric pressure are produced by regional differences in heating by solar energy, winds blow to equalize these pressure differences. Turbines convert this wind energy into electricity.

What are the advantages and disadvantages of onshore versus offshore wind?

Onshore is less expensive and easier to build, with limited habitat damage; offshore has stronger winds, is less obtrusive, but is more difficult to maintain and can harm marine life.

What are the locational constraints of wind power?

Wind velocity, isolation, land use conflicts, ecological impacts, land requirements, telecommunication interference and public opposition.

What are the new wind power technologies?

Blade-tip fins, Nacelle brushes, Direct drive turbines, Helical VAWT turbines, Wind-assisted ships

How does wave power work?

Friction of winds blowing over water creates waves and the kinetic energy of the vertical movement of the water can be harnessed.

What are the locational constraints of wave power?

Kinetic energy of the waves is greatest where mean wind velocities are high and winds are consistent in strength and direction to allow the wave height to increase; there is a long 'fetch' - distance of open water over which waves can build up
Need to be in an area of undisputed sea

Describe the different technologies to harness wave power.

Point absorber, Overtopping/terminator device, Oscillating wave surge converter, Surface attenuator wave power, Oscillating water column wave power

What are biofuels?

Renewable energy resources where photosynthesis has recently captured sunlight and stored it in materials such as vegetable oils or carbohydrates.

What are the advantages of biofuels?

Supply rate of energy crops can be controlled, biofuels can be stored until needed, they can be used to make vehicle fuels , they are 'carbon neutral', and the energy density is high.

What are the disadvantages of biofuels?

Supply of biofuel from wastes is limited, large areas of farmland are needed, the energy density of some biofuels is low, and intensive farming techniques may release as much carbon dioxide as using fossil fuels.

How does geothermal power work?

Radioactive decay of isotopes of thorium, uranium, and potassium in the Earth's mantle releases heat, this heat may be moved towards the surface of the crust by molten magma or hot water and is harnessed to create electricity.

What are some new geothermal technologies?

New turbine technologies are being developed that use liquids which boil and turn turbines at lower temperatures.

What are the locational constraints of geothermal power?

Geothermal power stations that use steam turbines need a heat source with a temperature above 150 degrees C. This requires relatively recent volcanic activity so that rocks are near the surface of the crust.

How does tidal power work?

Gravitational attraction between the Earth and the moon creates tidal flows of water that produce two periods of high water and two periods of low water in each 25 hour cycle.

What is a tidal barrage and how does it work?

A dam across an estuary or bay in which turbines are located so that all the water flowing in or out of the lake flows over the turbines.

What are the environmental impacts of tidal barrages?

Tidal range change, sedimentation, pollutant concentration.

What are some new tidal technologies?

A tidal reef - similar to a barrage in crossing an estuary but not as tall so water can flow over the top of the reef.