With incredibly testing time-scales for the move to 100% Zero Carbon new buildings in Wales, perhaps the proposed Severn barrage presents an opportunity to make this dream of the Welsh Assembly government achievable.

Here’s my plan…

The proposed barrage will generate over 8.6 gigawatts of electricity, that’s enough to power all the houses in Wales with renewable energy. So if the welsh can requisition all the power generated by the barrage - ignoring that fact that the southern end of the barrage will hit land somewhere in Somerset, then the renewable energy part of the Zero Carbon equation will be met and Wales at least can happily move toward the Zero Carbon utopia…

Of course this is ignoring all the objections to the barrage in relation to cost and impact on wildlife, but it does make you think…

Reference:
http://www.energysavingtrust.org.uk/Resources/Daily-news/Renewable-energy2/Barrage-on-Severn-renewable-energy-shortlist

A photovoltaic (PV) cell is a electronic device that converts solar energy into electricity.

The (very) basic process is:

• Photons in sunlight hit the cell and are absorbed by the semiconducting materials (usually silicon) from which the cell is made.
• These photons collide with atoms in the cell and in doing so electrons are loosened.
• The electrons flow through the material and produce electricity.

PV cells are bundled together and through some very clever technology the low voltage electricity generated by the cells is converted to a higher voltage for use in appliances.

PV cells are able to utilise both direct light and indirect sunlight and so, contrary to popular myth are effective even under grey overcast skies.

There are then three options of what to do with the generated electricity:

• Use it to power electrical appliances!
• Store it locally - ‘batteries required’.
• Export it to the national grid - removing the need for battery storage.

You can read more on these options - energy storage options

Pros and Cons

+

• A typical domestic installation in the UK will save around 1.2 tonnes of carbon dioxide per year
• No emissions of CO2 so renewable and sustainable
• No moving parts therefore minimal maintenance

-

• Require a open roof (within 90 degrees of South) that is able to support the substantial weight of the system
• High cost - currently around £10,000 for a typical domestic installation in the UK

References:
http://www.energysavingtrust.org.uk/Generate-your-own-energy/Types-of-renewables/Solar-electricity

For a truely Zero Carbon solution, we will need to aim for self-sufficiency (or a partial-self-sufficiency) in relation to the electrical energy that we consume. We must couple our energy generation system(s) with a storage system. Current options for what we do with the power we generate are:

• Use it to power electrical appliances! - ‘no batteries required’.
• Store it locally - ‘batteries required’.
• Export it to the national grid - removing the need for battery storage.

Regardless of the type of electricity generation system we choose any electricty not immediately used will need to be stored for future usage.

Batteries are a thorny issue as storage using batteries is an anathema to good environment design. This is because batteries contain toxic metals and unless they are discarded and reprocessed appropriately can easily lead to hazardous waste. Unless for truely off-grid situations, where few viable alternatives exist, batteries are best avoided.

That leaves us with exporting generated electricity to the national grid. These systems remove the need for battery storage. The generation system is connected to the local electricity network (grid) and any electricity not consumed locally can be sold to the electricity supply company. Where the local generation system is unable to provide all electricity demanded, for example at night, then electricity is bought from the grid. The ‘grid’ acts as the storage system. These systems avoid the risk of wasting unused power and also provide a back-up system that ensures that supply is maintained even when the local system is unable to fulfill demand.

According to the UK Housing and Planning minister Margaret Beckett the meaning of ‘zero carbon’ now needs to be re-evaluated.

“We need a revolution in the ways in which we plan, design and construct our buildings.
“They currently account for nearly half of all our carbon emissions. If we could improve construction methods, the ways in which we heat, light and power our homes, then we would make huge strides towards our overall ambitions.”

So perhaps the suggestion is that we walk before we run, that we in the UK start small and become more efficient as a beginning. I’m not sure that necessitates a new definition of zero carbon, but appreciate that in light of the political goal of all new homes being ‘zero carbon’ by 2016 the politicians may want one.

To this site, Zero Carbon still remains Zero Carbon …

[a zero carbon building] must produce zero net emissions of carbon-dioxide over its lifetime. [zero carbon definitions]