In the project's materials energy is also shown as flowing from stores of concentrated energy
such as fuel-oxygen systems. Such systems are represented as a "chemical spring." Thus, one way
that energy could be stored would be by making something hot as in Figure 6(a), for example using
an electrical supply connected to a heating coil to make some water hot. However, the same
electrical supply could be used to electrolyse the water, splitting the water into hydrogen and
oxygen. Making this hydrogen-oxygen system can be thought of as stretching a chemical spring,
as in Figure 6(b); when the two gases react together again, the spring relaxes and energy is
released.