In the second talk, Bill Dunster began by making an important point, as yet little understood by politicians or the general public, that, as we move towards a low carbon future, and begin to seriously address the problem of global warming, we shall no longer be able to import food, or energy, in any significant amount. Thus, the energy we use, and our food, will have to be produced within our national borders. For the UK, these borders include our surrounding seas, as a source of wind, wave and tidal power, but the need to feed some 60 65 million people, on this crowded island, from locally produced food, puts serious restraint on the land that can be used to grow energy crops, and dictates that urban development can no longer be allowed to encroach on green fields which have the potential to contribute to food production.
Estimates have been made of the potential contribution renewable sources can make to energy need in the UK in the long term. Adding up the contributions from onshore wind (including roof top turbines), offshore wind, wave power, tidal current power, photovoltaics, passive solar gain, solar water heating, biofuels and biomass the total comes to some 30% of the energy we use today. But by changing our life style in pleasant, benign ways we can live well using only one third of the energy we use today.
70% of UK housing is in suburban areas. For the typical suburban dweller, one third of the total energy used is consumed within the home, one third is car use and other transport, one third is used in the production, distribution and wrapping of the food this suburban dweller consumes. It follows that if we source locally produced food, particularly if this is produced on zero energy farms (a development that Bill is involved in, and showed us pictures of, with energy produced from bio digesters and with organic rather than synthetic fertilizer) then food energy use can be drastically reduced. As Bill Dunster then pointed out, transport energy use can be much reduced by living close to one’s place of work and cycling there each day.
He then turned to discussing energy use within the home, or within a cluster of homes, the field in which he has considerable expertise from experience at BedZED in south London and at Jubilee Wharf in Cornwall. ZED stands for Zero Energy Development, which means not zero energy use but total supply of all energy used from renewable sources. This aim has not yet been achieved at BedZED because the original wood fuelled ‘combined heat and power plant’ proved problematic (coking up, essentially, and requiring frequent servicing). A newer design for a plant of this kind has now been developed and, when this is fitted at BedZED, potentially all the heat and electrical power for this complex of homes and work spaces can be derived from wood chips produced from the maintenance of the local parks, urban trees and gardens.
A prominent feature on Bill Dunster’s developments are the roof cowls which funnel fresh air into the buildings and extract stale air. These allow the buildings to be well sealed against heat loss, through draughty doors and windows, while maintaining fresh air within. Heat exchangers warm the incoming air in winter by taking heat from the outgoing stale air.
In these various ways, building with a very high standard of thermal insulation and with thermal mass for temperature regulation, with passive solar gain, using photovoltaic panels to supplement electrical power from wood fired combined heat and power, Bill Dunster has shown that it can be done. Buildings can be zero carbon, keeping us warm and comfortable, and supplying our electrical needs, without putting any carbon dioxide into the atmosphere.
For more information see www.zedfactory.com
Summary by Geoffrey Haggis – June ‘07