Permaculture blog

Session 4: Renewable Energy

Published by Sam Page on 15 May 2012

The Renewable Energy session was hosted at Nick's house. Nick lives in Lockeridge, one of the many villages in the Marlborough area which is not linked to the gas grid.

We began by discussing ways in which the UK can meet its carbon reduction targets by exploiting the power obtained from solar, wind, tide and biomass incineration. Since renewables can only ever contribute about 15% to our current energy needs, it is clear that we need to cut our energy consumption massively in order to survive in a world without fossil fuels, such as oil and gas.

Nick showed us how he has insulated his house in order to cut heat loss from the roof, walls and windows by an amazing 50%. He introduced us to the 'U value', which is a measurement of the rate of heat flow through solid mass, such as windows, walls, floors and roofs. U values are expressed in watts per square metre per degree centigrade (w/m2/oC), for example:

  • an unfilled breeze block cavity wall has a U value of 1.6 w/m2/oC  
  • so a 10 sq m wall where the temperature inside is at 21oC and the temperature outside is at 1oC will lose heat at the rate of: 10 X (21 -1) X 1.6 X 24hrs = 7,680 watts or 7.68 kWh per day
  • if the house has outside walls measuring 156 sq m, then the loss will be 119.8 kWh per day
  • heating oil produces 10kWh per litre and costs about 65p per litre
Fuel cost comparison
Fuel Cost per kWh
Wood pellets 5.0p
Heating oil 6.2p
LPG 7.4p
Natural gas 4.1p
Electricity 7.3p - 15.3p

See: Confusedaboutenergy



Nick explained that he decided to invest in a wood pellet boiler because it uses a cheaper, more sustainable fuel source and also attracts the 'Renewable Heat Incentive' payment from the government.!

Find out more about the full installation of this wood chip boiler, here...

You can also view Nick's Solar PV system, here...




Nick demonstrating the working of his new wood chip boiler to participants