Consider a compartment model for biological energy production and transfer within a closed ecosystem, of the general form shown in Fig. 3.73. Assume, for instance, that the limiting factor governing the rate of primary production is solar radiation, such that the production becomes proportional to a schematic solar input, constant or with only seasonal sinusoidal variations (cf. (3.47)). Think of a food chain, in which you may find data on the rates and biomass levels appearing in Fig. 3.73 or some modification of it, and try to determine conditions for stability (no net production of the community as a whole).
If you have a computer at hand, you might try to set up a numerical simulation model for the system, assuming each rate (time derivative of a compartment level) to be a linear combination of all the compartment levels (some coefficients may be zero, of course). In this case you may also be able to follow the growth phase of the system, and attempt to judge whether the parameter values chosen are reasonable (cf. e.g. Odum, 1972, where examples of parameter values may also be found; Patten, 1971, 1972; Serensen, 1975a).
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.