Introduction
Efficient energy utilization is an important aspect of human life. The principle of conservation of energy states that energy can never be created nor destroyed. Thus, it is essential to utilize the energy available for us effectively and efficiently. Energy can be transformed from one form to another by use of appropriate transducers. When designing a house, it is essential to do it with the greatest regard to efficient energy use as well as safety to the environment. House designers should always come up with designs that promote efficient energy use. For instance, utilization of renewable energy should be maximized. On the other hand, the house should be designed in a way that it is habitable promoting good health, comfort, as well as, aesthetic. Since we have designed a house that produces its own energy, it is prudent to avoid losses as much as possible. Most domestic energy losses are thermal losses. When these are avoided then the energy produced in the house can be enough to run the house and the surplus can be distributed to the neighborhood. We have looked into a couple of principles in order to achieve an energy efficient house. These elements include well closed thermal envelope, regulated ventilation, energy conserving appliances, doors and windows and energy saving cooling and heating systems. These are key elements in the design of high energy efficient house (Kelly, 2012).
Thermal regulation
Thermal regulation is a key element in this design. In order to keep thermal conditions in the house habitable and energy-conservative, we have considered the following factors: insulation, roof and wall assemblies, caulking, weather-stripping, vapor and air retarders as well as position of windows (Wilson &Morril, 2000).
Insulation
Energy-efficient houses are designed to have greater R-values of insulation than any other local house. R-VALUE refers to the capacity of a material to offer resistance to the transfer of heat. The larger the value, the higher the conservation of heat. The determination of the R-value that a house needs to be constructed with will depend on the average temperatures that are experiences annually. For cold areas, the house should be designed with a high R-value whereas, in hot places, the house should be constructed with a low R-value. For instance, a normal house in London will have a ceiling whose R-value insulation is 19 while the exterior walls have R-value 11. The foundation and floor may not necessarily be insulated. However, we have come up with a well- designed energy-efficient house in the same locality. The house has a ceiling whose insulation lies within the range of R-50 to R-70 while the external walls have insulation ranging from R-20 to R-30.We are expecting to achieve this by filling the wall cavities with foam, wet-spray cellulose or rolls of fiberglass. The foundation walls are also insulated similarly to the walls in the living space. The heating appliances are placed at the basement so that there can always be the convectional movement of air where hot air goes up to where people live replacing the cold, dense air. Insulation compaction is ensured, and gaps avoided as much as possible so that energy conservation can be encouraged.
Roof and Wall Assemblies
Our house will have wood as door and window frames. It is also used in the roofing assembly in an extensive way. This is because wood is a poor conductor of heat and; therefore, most of the heat produced needed to warm up the house will not be lost through conduction. In our wood use, we have been very particular to use Structural Insulated panels. This design consists of oriented-strand board or plywood that has been laminated to form foam board. The foam board is seven inch thick and is used for insulation and framing. This reduces the chances of builders to make mistakes and to conserve the house from unnecessary energy losses. In the place of steel reinforcement, we have used two foam boards one outside the house and one inside the house. This does not only keep the house warm, but also reinforces the house to be able to stand such strong winds like hurricanes and tornadoes.
Windows
Heat lost through the windows in a typical house is approximately 25%. Our window for our energy-efficient house will have a window area of about 6 to 8 percent of the total floor area, with most windows placed high and in the opposite direction of wind travel. This encourages the less dense warm air into the house and discourages the cold air. The south-facing roof is made to overhang over the window to prevent overheating of the house during summer. On the other hand, the east, west and north facing windows are designed with low Solar Heat Gain Coefficients unlike the south facing windows which are designed with high Solar Heat Gain Coefficients to ensure summer heat enters the house. The house contains doors and windows with energy star labels which are extremely efficient in energy conservation. We have used casement and awning styles for windows due to their ability to close tighter and prevent heat losses.
Vapor and Air Retarders
Water vapor is a major risk to the house structure if it happens to condense inside the structures of the house. While water vapor has the effect to cause would rot, it has the effect of drawing latent heat of vaporization from the house causing refrigeration effects in the house. This implies that a lot of energy is used to heat the house as much heat energy is drawn by the water vapor. Thus, our energy-efficient house is designed with airtight walls where calking materials and gaskets are installed. Moreover at the convergence point of seams where sill plate, foundation, sub floor and floor joist header meet is a compact seal of gasket or calk material.
Ventilation
As much as the emphasis on the energy-efficient house is on tight seals, the house needs to be ventilated only that, in this case, the ventilation has to be controlled. Well, ventilated house prevents the risk of suffocation, air pollution, creates a comfortable environment and reduces the risk of damage, as well as, controlling moisture-air infiltration into the house. To preserve most of the energy, the ventilations are fitted with heat recovery ventilators that help recover approximately 70% of the heat.
Cooling and Heating Systems
Our house is designed to be air tight and allowing minimal thermal energy losses. Therefore the heating and cooling systems are simple and automated. Firstly, the house is fitted with sensors that determine the temperature of the house. Then these sensors are connected to a system of air conditioners consisting of heaters and coolers that have been programmed to operate under certain thermal conditions. They have been programmed to maintain the temperatures in the house to remain at room temperature approximately 298K. When the temperatures in the room fall below this level, the sensors detect and send this information to an installed micro controller that sets the heaters in function mode thus regulating the temperature. Similarly, if the temperature rises above the room temperature, coolers are automatically switched on thus regulating the temperature to normal room temperature. This will not consume much of the energy since the house is well designed to prevent heat losses. It saves energy and improves comfort in the house.
Efficient Appliances
In order to conserve the energy, design alone is not enough. The inhabitants of the house should ensure that the equipment used in that house are highly efficient. Appliances with high efficiencies, that is, close to one, draw the power they require to run with minimal energy losses. From time to time, the appliances need to be checked for efficiency and servicing be made for the faulty ones and those whose efficiency has lowered. Another important aspect that we have included in our design is the power factor meter that helps determine whether the power drawn by the appliance is the actual power utilized. Power factor helps one know by what angle current lags voltage or vice versa and it is denoted by the term cosФ. The power factor of any electrical circuit should be as close to one as possible to ensure efficient utilization of electrical power. In our house, there are fans that have motors with an inductive reactance that cause reactive power in the system. When this reactive power is much, it alters the power factor of the system causing current to lag behind voltage thus the fans draw a lot of current that is not utilized. This is corrected by use of capacitor appropriate capacitor banks. Thus, our house design contains a power factor meter and a capacitor bank in the electrical system (Electrical4u, 2013).
Environmental safety
Since the house utilizes carbon based fuels, some harmful gases to the atmosphere might be released to the atmosphere if not well disposed. For instance, combustion of carbon in limited supply of oxygen produces poisonous carbon monoxide which is lethal. Thus, carbon monoxide should either be reduced to carbon or oxidized to carbon dioxide. The carbon dioxide is not released into the atmosphere due to its tendency to cause global warming. Thus, the carbon dioxide is recycled in a hydrogen reactor at about 350oC fitted with a nickel catalyst to produce methane gas that is used as fuel again. When methane is combusted, it produces carbon dioxide that is recycled and water vapor that may be released since it is harmless.
Energy Source
The energy source for this home is the basis of its energy conservation since it utilizes renewable sources of energy. It is designed with large solar panels that produce enough energy to run the house on a sunny day. There are three big lead acid accumulators that store the excess energy. These accumulators are used alongside a dc- ac power inverter since the appliances in the house run on ac. Since the area is not well endowed with sun, a well-designed windmill is placed in the compound that rotates a powerful ac motor that produces ac power to supplement the energy requirements of that house. The lead acid accumulators are very essential in power storage such that they store the excess energy. The windmill is designed such that even if strong winds come twice a day for an average period of two hours and making the motor to make two hundred revolutions per minute, one lead acid accumulator would be full. Thus, on a dull day wind energy is converted into electrical energy. The electrical energy is used for several applications like cooking, heating, air conditioning and running the reactor. Its advantage is that it does not cause environmental pollution, and it does not require monthly expenses to cater for the bills. Once it has been installed, it will power the house as long as the system does not break down. Additionally, the two sources of energy can supplement each other when one fails (GVEP, 2013).
Effect of Energy Usage on Local Environment
The energy sources used are friendly to the local environment. They are safe to use and have no pollution effects to the environment. The carbon monoxide used is oxidized to carbon dioxide which is recycled in a hydrogen reactor to produce methane gas used for fuel in the house. This process helps to prevent release of carbon IV oxide to the atmosphere thus preventing global warming. This makes the energy efficient house friendly to the environment.
Conclusion
The designed house has a number of advantages, the primary one being the ability to conserve energy and use renewable fuel. Secondly, the house produces its own power which in excess will be sold to the neighborhood and earn income to the owners of the house. The house is comfortable with a conducive environment. The air conditioning is automated making the work less manual. In terms of safety to the environment, this house does not release harmful products to the atmosphere. During the winter, the house is not affected by the cold weather since it has been designed to be air tight, and all its joints are well sealed to warm up the house. The ventilation in the house is well controlled thus it sustains good health among the inhabitants of the house. Although the house is modern and energy-efficient, it has one disadvantage. To put up this house will require more capital than a typical house. However, in the long run the house will save the owner a lot of money since it uses renewable energy sources and earns income through the sale of electric power and methane gas.
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