Chapter 2 (Part 3) Environmental Systems: Energy Energy is a fundamental component of environmental systems Electromagnetic Spectrum Earth derives most of its energy from the Sun. Radiation arrives as photons (packets of energy traveling in waves through space). Electromagnetic Spectrum Photons travel in varying wavelengths (distance from wave crest to wave crest measured in nanometers). Short wavelengths=high energy: Long wavelength=low energy High frequency = high energy: Low frequency = low energy Electromagnetic Spectrum Sun energy reaching Earth is typically 250nm- 2500nm UV, Visible Light & Infrared radiation (most harmful radiation filtered by our atmosphere + Ozone Forms of Energy Energy- the ability to do work. Power- the rate at which work is done. energy = power X time Forms of Energy Kinetic energy- energy of motion. Potential energy- energy that is stored. Forms of Energy Chemical energy- potential stored in chemical bonds. Forms of Energy Temperature- the measure of the average kinetic energy of a substance. First law of thermodynamics Energy is neither created or destroyed. You cant get something from nothing. Second law of thermodynamics When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes. Second law of thermodynamics Energy Efficiency- Amount of work done : Amount of energy introduced 1 unit of energy : 20 logs 1 unit of energy : 3 logs 10% efficient : 14kg wood70% efficient : 2kg wood Second law of thermodynamics Energy quality- the ease with which an energy source can be used for work. Considerations: energy density, power density, emissions, cost and efficiency of conversion, financial risk, amenability to storage, risk to human health, and ease of transport. Second law of thermodynamics Entropy- all systems move toward randomness rather than toward order. This randomness is always increasing in a system, unless new energy from the outside of the system is added to create order. Energy conversions underlie all ecological processes System analysis shows how matter cycles in the environment System analysis shows how energy flows in the environment Open system- exchanges of matter or energy occur across system boundaries. Closed system- matter and energy exchanges across system boundaries do not occur. Steady state: Input = Output in a system A system responds to change by returning to its original state, or decreases the rate at which the change is occurring. Negative feedback loops A system responds to change by increasing the rate at which the change is occurring. Positive feedback loops