"Make hay while the sun shines"
This principle deals with the capture and storage of energy, within the environment, buildings and even society. If you think about a bank account, this principle is about how we can make our capital bigger, rather than how we spend the interest.
The vast majority of energy is supplied by the sun which is then captured by plants who have learnt the clever trick of how to turn photons into complex carbohydrates. This basic trick drives the whole planet's ecosystem. We need to rebuild 'natural capital' in order to create the basis for a long-term sustainable society.
Storing energy in the landscape
As permaculture designers we are helping to arrange our landscapes to maximise this energy capture. This is mainly by planting and nurturing new areas of 'biomass' - living things - mainly plants, usually as trees, woodlands, forest gardens, meadows, ponds, etc. Wherever possible we are also seeking to ensure that plant systems contribute to the development of deep healthy soils. Deep soils allow good crops, retain more rainfall, and also have the hugely important role of being the world's largest and most important living stores of carbon.
One advantage we have over nature is that we can also plan and decide how to catch energy in the landscape by storing it in dams, ponds and reservoirs, that can be used to do useful work for us.
Catching and storing energy in our built environment
We can design our buildings to catch energy too. Passive solar techniques are used to face buildings towards the sun, so that sunlight can help heat homes and provide light for free. Active solar technologies like solar photovoltaics and solar water heating can also catch the sun's energy and store it in well insulated water tanks and batteries.
You can store energy in the household too
Examples include preserved fruit and veg, wines and beers, a wood pile for winter fuel, a diverse seed box for the next growing season.