Early man relied on fire for the luxuries of light, heat and cooking. Today, all these luxuries are taken for granted. At the flick of a switch, a push of a button or the turn of a knob, instant power is delivered to us. Mother Nature produces the natural renewable resources that can used to generate electricity and heat such as ocean tides, natural winds and the sun. A variety of these resources are finite including fossil fuels such as coal and oil. For the 21st century, coal, gas and oil are no longer recommended as we’re moving towards infinite renewable resources such as solar and wind power. The electricity and heat energy derived from these resources is used in our homes for every day uses such as cooking, lighting, air conditioning, refrigeration etc (see figure 1). Figure 1: energy use in homes Stoves, microwaves, dishwashers, washing machines, televisions and air conditioners all rely on electricity. Everyday researchers work to find innovative ways to use our limited resources, find entirely new energy sources and improve the energy efficiency of a 21st century home. This report aimed at investigating the effect of different variables and their ability to keep a 21st century home warm during the winter. The investigated variables included floor insulation, double glazed windows and fan direction. Key Concepts Heat Light Intensity Heat transfer Heat transfer is essential in everyday living as it makes cooking possible, help keep warm or cool and assists in designing energy efficient homes. Heat energy is transferred when two objects come in contact with each other. If there is a temperature difference between two systems, heat will always find a way to transfer from the higher system to lower system. According to the first law of thermodynamics, heat transfer changes the internal energy of both the involved systems through conduction, convection and radiation (see figure 1). Figure 1: Heat transfer methods Heat transfer is given by: Q=m*c*∆T where m = mass c = specific heat ∆T= temperature difference between the final and initial temperature Conduction When two objects with different temperatures are in direct contact with each other, the transfer of heat between them is referred to as conduction. When a substance is heated, particles will gain more energy, and vibrate more. These molecules then bump into nearby particles and transfer some of their energy to them. This then continues and the energy travels from the hot end down to the colder end of the substance (see figure 1). The formula for conduction is given by: Q=kA(Thot-Tcold)t/d Where k = the thermal conductivity of the material A = the cross sectional area THot = the higher temperature TCold = the cooler temperature t = the time taken d = the thickness of the material Convection Convection occurs when a fluid (a liquid or gas) is heated resulting in change in density. The fluid expands on heating and becomes less dense. The difference in density with the surrounding fluid causes the fluid to flow, carrying thermal energy with it. For instance as displayed in figure 1, when a pot of water is heated by conduction, the hot air rises as the cold air falls to fill its place causing a continuous flow of air by natural convection. In some instances natural convection isn’t fast enough, therefore forced convection is applied. An example of forced convection is preventing computers from overheating, by installing a fan inside that blows the …show more content…
For instance if a copper wire is heated and plunged into a beaker full of cold water, the particles in the wire will transfer to the water until thermal equilibrium is reached. At the center of the second law of thermodynamics is a property of thermodynamic systems called entropy. Heat cannot spontaneously flow from a cold object (low entropy) to a hot object (high entropy) in a closed system because it would violate the expression: ∆S≥0
Entropy is a measure of the disorder in a system and it will always tend to stay the same or increase. When the temperature of an object increases, its entropy increases also, however when the temperature of an object decreases, the entropy decreases. The change in entropy is expressing using the equation: ∆S=Q/T where ∆S=change in entropy Q =heat added