Renewable Energy

The vast majority of my blog posts have been about how we are depleting our planet of its natural resources by means such as mining and fishing. For that reason, today we shall focus on renewable energy sources that could be the way of the future. Currently they still have a long way to go to reach the popularity of fossil fuel energy; Germany is the world front-runner in renewables yet uses just 14% renewable sources of energy. Here are summaries for four of the main types:

Wind

Wind turbines seem to be the icon of renewable energy, and wind farms (a combination of up to several hundred turbines) are an oddly captivating sight. They harness energy from the wind and then transfer this to huge electric power transmission networks that the turbines serve. This can be done more effectively offshore, where winds tend to be stronger, yet many turbines are still erected on land, a subject of much controversy.

Rygg (2012) has compiled the pros and cons of wind power very elegantly in a broad summary. Reasons for communities wanting wind farms are generally for modernization and increased employment opportunities, rather than for a source of green energy. Complaints stem from the turbines being eyesores and spoiling the landscape, as well as recent worrying affects to human health from living close to them. Despite these controversies wind power accounts for a huge 45% of the total renewable energy utilised worldwide, according to Solange et al (2011)

Main advantages: Turbines take up very little land space (despite being so tall) and so agriculture can carry on around them relatively undisturbed. They are very cheap to run once built.

Main disadvantages: They are eyesores, and there have been links to adverse health affects in humans living close to wind turbines; dubbed as ‘wind turbine syndrome’.

A lone wind turbine in rural England

Solar

Solange et al (2011) place solar energy as the best form of renewable energy due to it having the “least negative impacts on the environment”. The two main ways of turning solar energy into electricity are PV and CSP. PV (photovoltaics) directly converts light into electricity, whereas CSP (concentrated solar power) relies on mirrors to concentrate sunlight into a small and powerful beam, from which electricity can be produced. From the literature I have read it seems PV systems are favoured.

Main advantages: Very environmentally clean and can be used in places where people are not on a national grid (rural areas and LEDCs).

Main disadvantages: Weather dependent. Start up cost of the cells are very high.

A cartoon to illustrate the PV method

Tidal

Tidal power as the name suggests is harnessed from the tides of the oceans, which are brought about by the gravitational pull of the moon and the Sun. Currently tidal power has negative environmental impacts associated with it (despite being a renewable source). This is because tidal barrages (which are commonly implemented in bays) act as dams stopping the natural flow of rivers into the ocean and may affect migration patterns of organisms. Sluice gates in the barrages are periodically opened at high tide and the force of water coming through drives turbines to produce electricity. To try and get round this environmental issue tidal current turbine technology is being produced, as is discussed by Rouke et al (2009). This technology will harness kinetic energy from the tides to turn into electricity, in a similar mechanism to wind power. They can be attached to the sea floor, or float in the water and so are not as obtrusive as barrages.

Main advantages: It is extremely reliable and predictable

Main disadvantages: Due to the infancy of tidal current turbines they are not yet economically viable. Barrages have negative ecosystem impacts.

The proposed, less conspicuous, tidal current turbines

Geothermal

The Earth generates a vast amount of heat in it’s interior, from both radiation decay and gravitational processes. We can harness this heat and turn it into energy by forcing water down underground pipes, which are heated and produce steam. The steam rises and drives a turbine, which produces electricity. The water can then be cooled and the process started again, so it is very sustainable.

Lund et al did a world review in 2005 and the top 5 countries taking advantage of their geothermal heat were the USA, Sweden, China, Iceland and Turkey. However, on a world scale the use of geothermal energy was low because prior to the report the costs of fossil fuels and natural gas were very low. Their prices have rocketed in recent years and now geothermal energy is looking increasingly desirable. In a 2010 update to their studies it was indeed noted that between 2005 and 2010 the application of geothermal energy has risen by 55%.

Main advantages: Virtually unlimited sustainability and relatively safe to use.

Main disadvantages: It is not universally available (heat source points vary in intensity).

The process of geothermal energy production

(Note: papers linked to may need an institution log in to access the full text)