Renewable energy

SDG Ensure access to affordable, reliable, sustainable and modern energy for all

The sun is the ultimate source of most of our energy either directly through light and heat or indirectly through wind and waves. In addition there are tides created by the rotation of the moon around the earth or geothermal heating from the cooling of the earth’s core. The other source of energy is the conversion of light by photosynthesis into nutrients to enable the growth of plants and trees generally known as biomass.

These sources are renewable, abundant and inexhaustible. Their usage creates little or no pollutants and could be generated or produced on a micro-scale at point of use saving transmission and distribution losses. They have met our energy needs in previous eras and there is no reason why they could not meet our needs today.

One hundred years ago all energy production was localised – electricity was generated at point of use primarily by wind turbines whilst oil and paraffin was available in containers. Windmills or watermills were also used to grind wheat to produce flour.

Windmill		Watermill

Description

Renewable energy sources arise directly or indirectly from sunlight and involve five major processes

• absorption of heat from sunlight to produce hot water (solar water heaters)
• conversion of sunlight directly into electricity (photovoltaic or solar cells)
• conversion of air movement (wind) into electricity (wind turbines)
• conversion of sunlight into food which enables plant materials and trees to grow (biomass)
• concentration of low-grade heat stored within the thermal mass of the earth (heat pumps)

Advantages

The advantages of renewable energy sources are:

• they are abundant and wide spread
• they are non-polluting
• the fuel source in the form of sunlight or wind is free of all charges and is an inexhaustible resource

Disadvantages

The disadvantages are:

• variation in sunlight between day and night
• variation in sunlight between summer and winter
• the source is diffuse so that the 'collector' or 'absorber' may need to be reasonably large

Centralised versus dispersed energy production
Today most of our energy production is centralised with large electrical power stations situated on or near coal fields or near coal fields or near gas pipelines. This energy is then transmitted and distributed to our homes by electrical cables or pipelines. Whilst this is the most efficient form of generation and supply of energy supplied by fossil fuels, it does require a large infrastructure and leads to substantial losses of the order of 20%.

The reintroduction and uptake of renewable energy sources is most efficiently done at point of use as such sources are widespread and abundant. The losses in transmission and distribution can then be avoided. The electricity grid and pipe lines then perform a different role in which they supply energy if insufficient renewable energy is available locally or transfer energy if supply exceeds demand. In particular the electrical grid lines can link local sources together so that lack of supply in one area can be met by supplies from another area where the wind is blowing or the sun is shining.

The challenge
The challenge will be to adapt our lifestyle to the variation during the day and between seasons like summer and winter. Thermal storage and electrical storage will have a key role to minimise the mismatch between supply and demand.

In the longer term, we may need to adapt our lifestyle so that we work when energy is available and so this may mean going to school some days and staying at home on other days when no renewable energy is available. This could be quite an enjoyable experience.

Attaching renewable sources to a building

With renewable energy technologies, it is possible to install a number of these in the same building as is illustrated below. In future many buildings will be equipped with one or more of these energy sources which are described in more detail in the following sections.

Activity
Do many houses in your town have solar panels on their roofs?
Is your roof orientated SE to SW so that at some future time solar panels could be fitted?
Have you seen wind turbines and are there any wind turbines locally? Iif not, why not?
What do you think is needed to convert from fossil fuels to renewables sources in your community?