Renewable energy sources
Renewable energy is fuel that comes from a source that can be replenished in a short amount of time. This includes solar, wind, water, geothermal power and bioenergy. While renewable energy sources may not always be available – for example, if there is no wind to drive wind turbines, or cloudy days that reduce solar energy – they play an important part in reducing the use of non-renewable resources. Furthermore, many of these resources do not emit greenhouse gases directly into the atmosphere.
The Sun.
The sun is the source for nearly all energy on Earth. Not only can we harness solar power for electricity, the sun drives ocean currents, winds and plants use sunlight to grow.
Solar power
In the broadest sense, solar power supports all life on Earth and is the original source for all other energy resources we use. Solar energy is the Sun’s rays (solar radiation) that reach the Earth.
Having produced solar radiation for millions of years through nuclear fusion, this powerhouse produces so much energy that the amount of sunlight that reaches the Earth in a single hour could meet the energy demands of the whole world for an entire year! Outside Earth's atmosphere, the Sun's energy contains about 1,300 watts per square metre. About one-third of this light is reflected back into space, and some is absorbed by our atmosphere. Solar energy can be used directly to heat water or spaces (a greenhouse, for example).
In this process, the energy in the form of solar radiation is converted into thermal or heat energy. Solar energy can also be transformed into electricity through photovoltaics or solar power plants.
With such an amazing power source that produces no air pollution, you may be asking yourself why we do not utilise it more. The problem lies in our ability to harness the Sun’s power efficiently. At the moment, solar panels that capture sunlight and turn it into energy are expensive to produce and inefficient, but technology is improving. New Zealand does not yet have any solar-powered power stations.
Explore solar power further.
Wind power
People have been using wind for hundreds of years to transform the wind’s kinetic energy into mechanical energy that drives machines, mills grain and pumps water.
Modern technology wind mills use the wind to drive blades that turn generators that produce electricity. Wind power is hailed as a ‘green’ technology as it produces no air pollution. However, wind farms need a lot of wind turbines to be efficient, opponents complain about the noise, some people think they are eyesores, and there are fears that large wind turbines could be endangering wild bird populations.
Energy prospecting
Dr Peyman Zawar-Reza, from the University of Canterbury, explains how scientists can help energy companies to predict which areas they should target for further exploration and use for energy farming. He measures wind speed and how often it is windy in a particular area and uses this data to make predictions about how much energy could be generated.
New Zealand has some areas with consistent and strong wind levels, for example, in the Manawatu. This provides prime conditions for wind farming – indeed, New Zealand already has a number of wind farms supplying our electricity.
Explore wind power further.
Hydro (water) power
Like wind power, hydro power has been used to generate power for a long time – the Egyptians were using hydro power 2,000 years ago to mill grain. Hydro power is the most common form of renewable energy to generate electricity. It is estimated that around 70–80 percent of New Zealand’s electricity supply is generated through hydro power.
The movement of water on Earth that fills the rivers and subsequently drives hydro power is due to the water cycle. To use the power of water, it is often stored in dams and then channelled through pipes that drive the turbines of a generator.
Clyde hydro dam
The Clyde dam in the South Island uses water to generate electricity. It is New Zealand’s third largest hydro dam.
The benefits of storing water in dams for hydro power include areas for water sports and recreation. However, the modification of rivers can damage the ecology of an area, for example, interfering with fish migration. Now, any proposed hydro power schemes must take into account the ecological and local impacts they might have.
Explore hydro power further.
Geothermal power
Geothermal energy is derived from heat retained inside the Earth. To use this heat, we need a fluid that transports the heat (steam or water). The fluid needs to be able to move through pores and cracks in the Earth’s crust. When a source of heated fluid is close enough to the Earth’s surface, wells can be drilled into the ground to transport the geothermal fluid up.
In New Zealand, there are several low and high temperature geothermal fields, the most famous area being the Taupo Volcanic Zone where the geothermal reservoir reaches temperatures between 200–340°C. There are a few technologies used. Most commonly, the water or steam is heating a secondary fluid in a power station, which drives generators to produce electrical power.
Geothermal power station
Steam pipelines at the Wairākei geothermal field. Three of the five Contact Energy geothermal power stations in New Zealand are based within this field outside of Taupo.
Side effects of geothermal power are mostly related to what is being done with the water or steam after it has been removed from the ground. Geothermal power plants generate CO2 – but far less than fossil fuelled plants.
Explore geothermal power further.
Bioenergy
Bioenergy means converting biomass to produce a form of energy like heat, light, electrical power or transport fuel. Burning wood in a fire, for example, is using bioenergy. Natural materials that are used as energy sources can be wood, plants and even bacteria.
Woody residue uses
Peter Hall from Scion discusses how waste wood can be used as an energy resource.
The forestry industry already uses some of its waste wood to produce heat and steam. Sawdust and wood shavings are being used in a compressed form to make wood pellets, which can be used in fireplaces. Waste wood can also be turned into ethanol (using enzymes). Ethanol could be used to run cars and other combustion engines.
With rising oil prices and concerns about how long fossil fuels will be available, bioenergy has received a lot of attention in recent years as people search for alternatives like using the by-products from sawmills, re-using cooking oils and planting fast growing plants that can be converted into a usable fuel. While these resources are renewable, they produce greenhouse gases.
Explore New Zealand's bioenergy options further.
Residual waste and biomass
Peter Hall from Scion explains that residual biomass is material created as a byproduct from making something else.
Residual biomass is a term that is used to describe waste products from biomass resources that can be used to produce energy. Wood off-cuts left behind in the forest are a good example of this. However, energy demands outnumber what can be supplied by using residual biomass. In order to supply a growing demand of renewable energy resources, residual biomass could be supplemented through purpose-grown products.
Related content
Find out more about these renewable energy sources:
Compare to these various non-renewable energy sources.
Useful links
The New Zealand Energy Efficiency and Conservation Authority (EECA) focuses on energy efficiency and the use of renewable energy sources.
Gen Less is a government agency dedicated to mobilising New Zealanders to be world leaders in clean and clever energy use, explore how business can run more sustainably with renewable energy.
MBIE is responsible for maintaining data on New Zealand’s generation stack. This is a list containing information on the costs of existing and new electricity generation plants in New Zealand, it includes reports on geothermal, hydro, thermal, solar and wind power.
