The role of green energy
I thought it might be useful to give a backdrop to residential energy and look at the macro picture of electricity generation in the UK.
UK Energy Landscape
According to figures produced by BERR in May 2008, the United Kingdom had around 85,000MW of electricity generating installed capacity. This capacity is largely made up (~80%) of conventional thermal power stations, those that burn fossil fuels.
The remaining was then made up of a mixture of generating technologies; nuclear (~14%) and others such as biomass thermal power, hydroelectric plants and wind farms (~6%).
The potential issues with this mix of generating technologies are as follows:
1. Conventional thermal stations rely on fossil fuels such as coal, natural gas and oil. The UK has for some time now been a net importer of these fuel types, they are not renewable and the major reserves of many are in less politically stable countries. All of these factors put our energy security at risk.
2. By burning fossil fuels we are contributing to the impact of global warming, as the combustion process produces Carbon Dioxide as a by-product. For instance producing 1 kiloWatt-hour (kWh) of electricity from coal produces between 800-1200g of Carbon Dioxide, for Natural Gas the figure is 400-600g.
3. The UK has not yet invested in a new nuclear programme, many of the nuclear power stations that currently operate are due for decommissioning in the next decade or so.
Renewable Or Green Energy
Renewable energy generation offers some countermeasures to the above.Renewable energy is largely generated ‘locally’ so not subject to the political risks cited. During generation it provides a significant benefit in terms of carbon footprint, many technologies are carbon free or carbon neutral.
It is more socially acceptable and is increasingly important in meeting our legal obligations. Under EU law by 2020, 20% of UK energy must be produced by renewable technologies, as opportunities for renewable heat & transport are limited in the UK; it’s likely that over 30% of our electricity will need to be produced by renewable sources to meet this target.
However, before we get too excited, green energy is not a panacea. Many are not suitable for providing the base load electricity requirements that technologies such as nuclear generation can; this is due to technologies such as wind and solar being dependant on prevailing weather conditions.
A Selection Of Renewable Energy Technologies
- Photovoltaics (PV) – solar panels that convert solar radiation into direct current electricity
- Wind – the use of wind turbines, where the blades are rotated by wind energy and the mechanical energy is converted into electricity by a generator. The UK has a number of onshore and offshore wind farms that harness wind energy
- Wave Power – devices are used to convert the mechanical energy of the waves into electricity
- Tidal Stream Power – uses a similar approach to wind power, where underwater turbines turn as a result of tidal flows, this mechanical energy is converted to electrical energy by generators.
- Hydro – turbines are used to drive electricity generators, the turbines are driven by running water.
- Biomass – a collection of techniques where things such as gas byproducts from landfill or sewage, wood, waste and straw are burnt to produce heat. The generation processes are similar to conventional thermal, however, the raw materials are sustainable.
Some of these technologies are clearly not suitable for domestic application, however, some such as wind and photovoltaics are.
How Can Individual Households Help?
Every soldier must know, before he goes into battle, how the little battle he is to fight fits into the larger picture, and how the success of his fighting will influence the battle as a whole.
Bernard Law Montgomery
The quote above fits quite well in my view. Each of us, by applying some form of green technology to our homes, has the ability to contribute to the story. By producing our own green electricity we reduce the demand on the main grid, which has to be beneficial.
UK households use between 3,000 – 5,550 kWh of electricity a year. In a document produced by the Mid-Wales Energy Authority looking at payback periods for domestic wind turbines an annual power of aroung 1,700 kWh (given a set of assumed conditions) could be produced. This would serve to reduce the power pull on the grid by 33% – 60%.
Alternatively, photovoltaic arrays can typically produce between 4 – 6.5 kWh/m^2/day in the northern hemisphere; the variance mainly driven by hours of sun. For a full year there is the potential to produce between 1,400 – 2,400 kWh per m^2 of photovoltaic array. Given these figures, the application of one or more of these technologies means that we can reduce our demand on the centralised large scale electricity generation resources and have a noticable impact on the production of green house gases.
