• The booklets first looked at thermal energy storage. Energy can be stored. Energy can flow. Energy can spread from a source to its surroundings. Energy is conserved.
• The booklets showed and used the idea that temperature change can result from mechanical as well as thermal processes. Energy can be transferred by doing work. In fact, there are mechanical energy stores just as there are thermal stores.
• Energy transfer that is driven by temperature difference can result in work being done, as happens in an engine. There is, fundamentally, only one kind of energy, and it is important in both thermal and mechanical contexts.
• A chemical system can store energy. A battery is an important example. Any fuel-oxygen system is also an energy store. Plants gather energy from sunlight to create such a store in a carbohydrate-oxygen system.

• Energy can be transferred from store to store. This can happen directly or it may involve the action of an energy transfer device such as a lever or an electric circuit component.
• Dissipation is the spread of energy into the surroundings of a process, so that the energy can no longer be usefully transferred. It is necessary to understand dissipation in order to have a working understanding of energy conservation.
• At the end, the one amazing idea is the universality of the energy concept. It can be applied in simple physical systems or in complex industrial, biological or indeed cosmic processes.

Questions to develop understanding

Using the SEP Energy Transfer Kit you can set up more chains of components and repeat the questions that have been asked in the practical activity and the animations. Where does storage take place? Where is direct transfer happening? What about dissipation? How does dissipation help us to understand conservation?