Overview of Green Technology

Green technology is a broad term used to describe any technology which reduces, mitigates or reverses the effect of humans on our environment. It is also known as environmental technology.

The most prominent example of green technology is renewable energy, but green technology also covers sectors, such as water management, recycling, waste management, agriculture, and sustainable industry. Below are more in-depth descriptions of key green technologies.

Solar Energy

Solar energy harnesses sunlight and turns it directly into energy. The most common method of utilising solar energy are solar panels (also known as photovoltaic cells), which generate electricity when the sun shines on them. The amount of electricity generated is proportional to the intensity of the sunlight shining on the panels.

The main advantage of solar panels is that they require very little maintenance or ongoing costs once installed. Solar power will feed into the electricity grid when the sun is shining, therefore, at that moment the grid does not have to rely on fossil fuels and will reduce the amount of greenhouse gases entering the atmosphere. However, the obvious disadvantage is that they do not work when the sun is not shining. That said, solar panels are fast becoming one of the cheapest sources of energy on the planet [1],[2].

Wind Energy

Wind energy, or wind power, generates electricity from the wind. This is usually in the form of a wind turbine whose blades are turned by the wind. The more the wind blows, the more energy is generated. Typically wind turbines are situated in places which have strong and constant winds, either on the top of a hill, by the coast or out at sea.

Like solar power, wind power is an intermittent energy source, since electricity is only generated when there is sufficient wind. However, by combining wind power with other renewable electricity sources, as well as backup and energy storage technologies, these intermittency issues can be evened out.

Hydroelectricity

Hydroelectricity generates power from the flow of water. For example: from the natural flow of a river; by releasing water from behind a dam; or from the ebb and flow of the tides. In all these cases, a turbine is placed in water and spins as the water flows through or past it. The turbine is connected to a generator, which generates the electrical energy.

One advantage of hydroelectricity is that it is a fairly predictable source of energy. For example the tides will reliably flow back and forth. Furthermore, the flow of water from behind a dam can be varied to match the demand from the electricity grid. However, hydroelectricity is heavily reliant on geographical features. For example, it requires mountainous regions to build dams or narrow coastal straits, which which have strong tidal flows.

Anaerobic Digestion

Anaerobic digestion is the process by which organic matter is broken down in an environment starved of oxygen. This creates a methane rich gas which can then be burnt to generate electricity and heat. The primary source of feedstock for anaerobic digestion is purposely grown energy crops, waste organic matter and waste food (i.e. the stuff that goes in your waste food bin). The feedstock is placed into large digesters, where the matter breaks down into gas, which is used to generate electricity and heat, a semi-solid fertilizer called digestate.

Waste-to-Power

Waste-to-power or waste-to-energy is the process by which general household and some industrial waste is processed and uses to produce heat and electricity.

Many waste-to-power facilities are attached to larger waste management plants, which recycle some of the waste material. Some waste-to-power facilities simply incinerate non-recyclable waste, whereas other facilities will turn much of the waste into gas before burning it to generate electricity and heat. These processes are not renewable, since the materials required to generate the power will be a mixture of plastics and other materials, which have not been sustainably sourced. However, the process can be regarded as green technology because the waste will not be stored in a landfill, which is considered beneficial to the environment.

Reserve Power

Reserve power refers to a group of different technologies used to provide backup services to the National Grid. These backup services provide a range of functions, such as grid balancing and fast frequency response. In the event of a power station cutting out or a sudden increase in demand from consumers, these backup services will provide extra electrical energy into the grid to stabilise it.

Many existing reserve power systems use fossil fuel technologies, such as diesel engines or gas turbines (obviously not green technology!). However, Reserve power is also providing an increasingly important service for renewable power by starting to solve the intermittency issues of solar power and wind power. For example, it is able to fill in and provide power to the grid in case of a drop-in wind power. Future reserve power technologies will involve battery storage technology, which will store excess renewable power and allow it to be fed back into the grid when these renewable technologies aren’t producing power or when consumer demand increases.

Battery Energy Storage

Anaerobic digestion is the process by which organic matter is broken down in an environment starved of oxygen. This creates a methane rich gas which can then be burnt to generate electricity and heat. The primary source of feedstock for anaerobic digestion is purposely grown energy crops, waste organic matter and waste food (i.e. the stuff that goes in your waste food bin). The feedstock is placed into large digesters, where the matter breaks down into gas, which is used to generate electricity and heat, a semi-solid fertilizer called digestate.

References

  1. The Guardian, 2019, Coal is on the way out: study finds fossil fuel now pricier than solar or wind [accessed 3/4/19]
  2. energyinnovation.org, 2019, The Coal Cost Crossover: Economic Viability of Existing Coal Compared to New Local Wind and Solar Resources[accessed 3/4/19]

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