Green energy is energy that is generated using sources with a low environmental impact. These sources are generally renewable and include the sun (solar), wind, water (hydro) and geothermal.
Green energy sources don’t generate harmful greenhouse gases as the use of fossil-fuel energy sources do. Although they are often used interchangeably, the subtle difference between “green” and “renewable” energy is that with green energy, the focus is on the impact on the environment, whereas with renewable energy the focus is on sustainability.
As well as using renewable sources that reduce greenhouse gases, using green energy also avoids environmentally harmful extraction techniques such as drilling, mining and fracking.
Types of Green Energy
Solar power is usually produced using photovoltaic panels, solar collectors and thin-film solar sheeting. The solar cells turn sunlight directly into electricity. It is a clean and non-polluting source of energy. Solar technology has become cheap enough to power everything up to entire neighbourhoods.
The design of many new homes takes solar energy generation into consideration both through solar panels and the water-heating systems. Analysis has shown that the UK has now reached its one million solar homes milestone if you count both solar PV (800,000 homes) and solar thermal (250,000).
Energy from wind is generated by using large turbines which are connected to a power collection, storage, and distribution system. The wind turns the turbine’s blade and a motor turns transforming kinetic energy into electricity. This energy is then transferred to the gearbox, converting the slow speed of the spinning blades into higher-speed rotary motion which turns the drive shaft quickly enough to power the electricity generator.
This type of energy generation is very effective in providing electricity to small, isolated communities. Wind powered energy is often preferred over solar-powered methods in agricultural areas, as land containing wind turbines can be more easily used for other purposes.
Off-shore wind farms, which are becoming an increasingly common site around the coastline of the UK, have much higher building and maintenance costs, but are able to harness stronger, more consistent winds.
Wind power is increasing in popularity around the world as the technology becomes cheaper and global policies and targets on climate change have become a priority. Many countries outside of the traditional energy markets of Europe and North America are the ones driving the trend. By the end of 2018, China accounted for roughly 34% of global installed wind power capacity, roughly the same as the whole of Europe. In the UK the percentage of electricity used from wind farms has risen from 1.5% in 2008 to 18% in 2018.
Hydro power uses the movement of water to power turbines attached to generators. In many countries, it provides the highest proportion of energy over any other green resource. Hydropower has the advantage of not producing significant amounts of waste and also provides a unique environmental advantage as many of the largest hydroelectric dams make use of the reservoirs, which often serve as a facility for recreational activities. The reservoirs also provide a large water supply which can provide valuable support for agricultural regions.
Smaller scale hydro or micro-hydro power has become an increasingly popular alternative energy source, particularly in remote areas where other power sources are not viable. Small scale hydro power systems can be installed in small rivers or streams with little or no environmental effect or disruption to fish migration. Small scale hydro power systems do not generally make use of a dam or major water diversion, but instead use water wheels to generate energy.
Hydropower currently accounts for around 20% of the world’s electricity and 90% of the world’s renewable power. The UK generates about 1.5% of its electricity from hydroelectric schemes which are mostly large-scale schemes in the Scottish Highlands.
Tidal energy is generated either by tidal stream generators or by barrage generation. Energy created through the use of tidal generators is generally environmentally friendly and causes little impact on the environment. Tidal stream generators use the kinetic energy of the water’s movement to power the turbines. Although, as yet not widely used, tidal power has the potential to add significantly to future green electricity generation. Significantly, tides are more predictable than wind energy and solar power.
Traditionally, among sources of green energy, tidal energy has suffered from relatively high cost and a limited availability of sites with sufficiently high tidal ranges or flow velocities, restricting its application.
However, many recent technological developments and improvements suggest that the total availability of tidal power may be much higher than previously assumed, and that economic and environmental costs could be brought down to competitive levels. Some tidal generators can be built into existing bridges or entirely submersed, thus reducing concerns over their impact on the natural landscape. Land constrictions including straits or inlets can create high velocities which can be converted into energy with the use of turbines.
Geothermal energy is generated underneath the earth’s surface as heat. Most thermal energy power plants are built close to tectonic plate boundaries, where the energy is extracted more easily.
Geothermal energy is a very powerful and efficient way to extract renewable energy from the earth through natural processes. This can be performed on a small scale to provide heat for a residential unit using a geothermal heat pump, or on a very large scale for energy production through a geothermal power plant.
Recent technological advances have significantly expanded the range and size of viable resources, especially for direct applications such as home heating. Geothermal power doesn’t require fuel, and is therefore immune to fluctuations in fuel cost, although capital costs are high. It is the drilling which accounts for most of the costs of electrical plants, and exploration of deep resources involves very high financial risks.
Green Energy Networks
Both the generation and distribution of energy has an environmental impact and therefore is a green issue. Where electrical generation and storage is performed by a variety of small, grid-connected or distribution system connected devices it is referred to as “distributed energy resources” (DER). DER systems increasingly use renewable energy sources, including solar power, wind power, and geothermal power, and play an important role in the overall electric power distribution system.
Part of DER initiatives has been the establishment of local heat networks, which can vary enormously in size creating both cheaper and lower-carbon sources of heat generation.
There are essentially two types of local heating networks, “Community heating” which is about supplying heat to a relatively small development of one or perhaps two buildings with multiple dwellings and “District heating” which aims to distribute large-scale sources of heat over a large area, and connect multiple buildings in a heat network.
In England and Wales, the UK Government has launched a £320million investment programme as part of plans to extend district heating capacity, which has been driven by local authorities. The target is in place for 15-18% of heat to be generated from networks of this kind by 2050.
Learn More with Therma-Mech
Here at Therma-Mech, we help leverage district heating to create effective energy solutions. To learn more about this type of green energy and how it can save money as well as providing environmental credentials, get in touch with our expert team today.