Web Site of Robert John Morton
Sustainable Energy: Energy Needs
We measure energy in joules. It is the same unit for heat energy as for electrical energy as for mechanical energy as for any form of energy. A joule is a watt-second. There are 3,600 watt-seconds in a watt-hour, and 3,600,000 watt-seconds (3.6 megajoules) in a kilowatt-hour.
- Our home consumes energy in two forms:
- eh = thermal for space heating and hot water
- ee = electrical for lighting and electrical devices
We cook by electricity. The heating energy heats the house and provides hot water. The default amount shown also accounts for what is lost to the outside via combustion products - ie what goes 'up the chimney', which in our case is a balanced gas flue. I would expect a modern wood burning fireplace to be of comparable efficiency to our 20 year old gas boiler. One should also consider the psychological benefits of the dancing flames of an open log fire over the inanimate facade of a closed stove or boiler on dark winter nights.
This amount of thermal energy provides us with a tolerable, though by no means comfortable, level of heating. With better design and more sensible materials, a house of the same size could be made to provide a very comfortable environment for the same energy consumption.
Annual figures are fine for energy sources which store large amounts of energy in a compact form like wood and rape oil (see oilseed rape crop on the right). However, the availability of solar and wind energy varies considerably with the time of year. For these it is very helpful to know how your demand for heating and electricity varies from month to month during the year.
Figures in the above tables are automatically posted to other tables in this HTML frameset for sizing the various energy conversion systems. Now please return to the Introduction frame.
© January 2001: Robert John Morton