Renewable energy

The main types of renewable energy systems are:

Solar
Passive solar design: Techniques that harness the free energy available to architects by good planning. Good examples of this working are greenhouses that harness heat and atriums for light.

Active Water/Air heating: A system for generating low temperature hot water from daylight. The systems are black panels that absorb daylight to heat a liquid (either water directly or an anti-freeze system through a heat exchanger). The system usually has roof mounted panels and a larger than normal hotwater tank to store the heat. Requires roof space on the East to South to West side of the building.

Photovoltaic (PV)
Solar panels arranged facing South-East to South-West to harness sunshine to generate electricity. There are various technology options with slightly differing efficiencies (costs are offset against efficiency). The array supplies power to an inverter, a device which converts the direct current (DC) generated into alternating current (AC). This can be stored in a battery or be grid connected. In most applications it would be appropriate to seek grid connection.

This technology can attract payments from energy companies called feed-in tariffs. These are continually changing and residents should check with the Ofgem and DECC websites for the latest information.

Wind
The whole Sefton cost is a rich source of wind for wind generation hence the Seaforth docks installation. The moving blades convert energy from the wind stream which rotates a shaft, mechanically coupled via a gearbox to an electrical generator. Usually grid connected although can be linked to batteries.

Biomass
Essentially this is where biological material (wood, straw, energy crops or other organic material) is combusted in a modern burner/boiler to generate heat. The source for energy is usually dried wood (20% water content, wet basis is normally 50%). The resultant available energy for it is 14.4MJ/kg. Suppliers of fuel are limited but there is a well-developed network of producers and setting up new sources can be a rapid process. Most boilers are adaptable to new sources (ie: if you have been using wood you can switch to straw without altering the boiler, although you may need to adjust your delivery system). Wood is the most abundant fuel source and comes in 3 forms; logs, woodchip and pellets. Pellets are the easiest to automatically load the burner with although there is a processing premium applied. Some systems are amenable to burning waste products such as card, wood offcuts/shavings or even garden waste (known as green waste).

Geothermal
Is accessing the Earth's internal heat stores, not strictly available without significant drilling, theoretical uses have been around for a while and only really limited applications use this. Hot water spa towns have benefited from preheated water for centuries but attempts to commercialise this have not been successful in the UK without significant grant support. The most successful application has been the Southampton district heat network that uses geothermal heat stores to warm water for heating offices and shops in Southampton town centre (this is topped up with a gas turbine).

Ground source heat pumps
This involves the use of underground heat stores created by the Sun mainly (the ground at 2m below the surface has a fairly constant temperature of around 10°C). Heat is accumulated through the use of a heat pump (the same principle as a refrigerator in reverse: think of the hot grills on the back of your domestic refrigerator). There are two main ways of accessing underground heat, either trenching or boreholes. Trenching tends to be cheaper as it involves digging to 2m deep and up to 1m wide, filling 0.4m of trench with sand at various stages, inserting heat coils and backfilling. This is usually half the costs of boreholes (unless you are trenching on an existing specialised surface, such as a highway or carpark). Boreholes are no more 6 inches in diameter and usually descend down to 70m.


Last Updated on 15 September 2015

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