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Renewable energy sources
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Renewable energy sources

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.

The challenge will be to adapt our lifestyle to their variation during the day and to the variation between summer and winter. In this thermal storage and that of electricity will help to overcome the mismatch between supply and demand.

Renewable hot water and space heating

The three principal sources of renewable heating and cooling are solar thermal, heat pumps and biomass. Whilst solar thermal panels generally provide only domestic hot water, the other two sources can provide heat for both hot water and for space heating.

Solar thermal panels are generally mounted on the roofs of buildings and should be orientated to have direct sunlight for most of the day. They could supply all of a family’s hot water needs in the summer and up to 40% during the winter.

[link to the solar thermal page on the KITH website]

Heat pumps do not produce heat, but concentrate low grade heat present in the ground, air or water and convert it into useful heat. Heat pump systems vary in size from small systems for individual homes to large systems for schools, commercial buildings and hospitals. Heat pumps are reversible and so can extract heat from building during the summer.

[link to the heat pump page on the KITH website]

Biomass boilers generally use wood pellets which can be gravity fed or blown into the boiler. Space of 1 to 2 cubic metres is required for storage. The alternative is wood burning stoves which require a source of logs most likely from a nearby forest.

[link to the biomass page on the KITH website]

Renewable electricity
Solar cells and wind turbines are the principal sources of renewable electricity. Solar cells, generally in the form of photovoltaic modules or tiles, are usually mounted on the roofs of buildings that have a suitable south facing orientation, or on a flat roof with a similar orientation. The electricity generated can be used by the occupants and any surplus exported via the electricity grid; conversely electricity can be obtained form the grid if demand exceeds supply.

[link to the photovoltaic systems page on the KITH website]

Wind turbines generate electricity by the movement of air turning the blades to which the shaft of a generator is attached. Large turbines can supply electricity to communities whilst small sized turbines and can be mounted on a pole or on top on ones roof.

[link to the wind turbine on the KITH website]
[link to encouraging renewable energy sources]

Isolated wind turbine generator, Fair Isle
Grid connected wind turbines


Centralised versus dispersed energy production
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



 

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