In the field of engineering, and especially in the branch of building and construction, some principles serve as very important guides. The two most important principles of a well-constructed house are the principles of design and the principles of construction (Rounce, 1998). The design aspect covers the shell of the building while the principles of construction cover the structural aspect of the building (Austin, et al., 1999). Therefore, the design engineer as well as the workers and building contractors have to be in sync to ensure that the building is up to the required standards, both aesthetically and structurally. All that stated, the economics of the building have to consider the environmental repercussions that will come when the building begins its day to day operations. The building sector is responsible for a huge percentage of the emissions that lead to global warming: the decrease in polar ice caps, the increase in temperature, the shift in weather patterns, the increase in sea levels just to mention a few.
The major responsibility lies on the design engineers. Their responsibility lies on the fact that designing a building is the most important aspect of construction: design a building that tends to consume a lot of energy for efficient functioning and the result will be an increase in the emissions, design a building that tends to consume little energy and there will be a decrease in emissions but, there will be a decrease in the efficiency of the building. Therefore, the design engineer has to consider all the aspects of operation as well as the design aspects.
Various structural aspects as well as appliances that come with the operation have to be considered in the design and construction of a building. The ability of the building to withstand natural forces as well as its ability to utilize these forces plays a crucial role in green building technology which is at the forefront of building conferences and forums. Therefore, not only are design engineers mandated with the responsibility of ensuring that there is comfort in our homes, they play a crucial role in ensuring that the deterioration of the environment is at a minimal level. According to Sálvano Briceño, the United Nations secretariat of the international strategy for disaster reduction, increase in disasters both in magnitude as well as frequency worldwide is attributed to unchecked urban design and growth coupled with environmental changes and degradation, which basically mean the design engineers (Willison, 2008).
The following design to some extent demonstrates the concepts stated. The building is a 250 bed hotel that typically has a conference room. In the design some of the factors to be considered include the hotel occupancy during the high and the low seasons. Furthermore, the building will consider the electrical usage and all the heat gains and losses. Heat gains and losses are a major factor in the design of the building because they determine the comfort levels. However, all this is determined by the materials of construction as well as the temperature ranges.
The design of the building
The building has 250 beds distributed all over the 12 floors and as such, the various design aspects such as ventilation, electricity usage, heat losses and gains have to be accounted for. The electricity consumption basically plays an integral part in the running costs of the building. Buildings which tend to consume more electricity tend to have high running costs. However, the electricity consumption may be attributed to the design employed because the heat gains and losses can be offset by electrical appliances such as heaters and fans. The two are rudimentary forms of heating and cooling equipment and basically consume presumably low amounts of electricity (Bradshaw & E, 1993). However, some buildings employ complicated systems for cooling and heating the buildings.
Considering the room size to be 60 square meters (7.75 square meters=length=breadth) with the basic electricity consumption on electrical lighting, the following procedure may be used to determine the total electricity usage of the building.
In the design aspect of lighting, we have to consider the duration when the lights will be on full time. In our case, we might take the period between 7 p.m. and 9.a.m which is basically 14 hours.
In the determination of the total power used, the efficacy, the energy of the lamp and the illuminance are essential (Kreith, 2001). Because our scenario is basically that of a hotel, we may chose an illuminance of about 50, which is that of a dwelling. The bulb may be taken to be 100 watts
On the other hand, the efficacy may be chosen from the following table:
In this, we can chose a fluorescent light of an efficacy of 80lm/with the light loss approximated as 50%.Therefore, the electrical consumption of one 100 watts bulb will be calculated as follows:
Therefore, the energy consumption of one room=6000/80=75 watts for a single room assuming that there is only one fluorescent bulb. Therefore, the total energy consumption of the building =75*250=18750watts=18.75 kW/day
The Heat Losses of the Building
Heat losses from a building are mainly achieved through radiation, conduction and convection (Emmerick & Dolls, 2001). The air inside the building is typically warmer than the air outside the building and as such, the heat is transferred from the inside to the outside as per the previously stated methods. Another important aspect in the transfer of heat is the thermal transmittance (Per kvols, 2000). Different materials have different rates at which the heat can be conducted through them and as such, the design engineers should consider this property before selection of the materials to be used for the slab, walls, roof, windows etc.
The heat losses can be tabulated as per the table below by basically applying the formula where: Q is the cumulative heat loss, A is the area of an element, U the thermal transmittance of the element and the internal and external temperatures respectively. In this design, the elements to be considered are those for a single room and include: windows, doors, the floor and the walls. The heat loss from all these elements will be based on their thermal transmittance.
To begin with, let’s consider a window of 2.5 by 2.5m.Furthemore, the window is a double glazed one with thermal break.
Therefore, AU=2.5*2.5*3.3=20.625 considering each room has a single window
Considering the floor slab, the following table may be useful
Only one floor is solid while 12 floors are suspended. Therefore, we can calculate AU as follows:
One solid floor (taking a total floor area of 1600 sq. meters).Furthermore, two edges are exposed
12 suspended floors with the same area=12*1600*0.22=4224
Walls: Taking the height of the walls as 3 meters and the length =width =7.5m (220mm light plaster)
Therefore the cumulative AU=4587.The total heat loss can be calculated as follows (taking the comfort internal temperature to be 25 degrees Celsius)
|Ambient temperature (°C)|
Total heat loss=163173925watts
Heat gains to the building
Heat gains basically take two forms: sensible heat gains and latent heat gains (de Souza, 2013). The former refers to heat gains mainly attributed to temperature difference and electrical appliances while the latter basically deals with heat gains due to moisture transfer. In this design example, we will consider sensible heat gains as they mostly affect the temperature of the building (Attia, et al., 2012).
The electrical fluorescent bulb produces 100 watts of sensible heat. Furthermore, sensible heat is obtained by multiplying the insolation by the window area.
|Daily Insolation (kWh/m2)|
Therefore, the sensible heat gain for the whole building =345437.5watts
The running costs of the building
Considering that the high season and low season are 6 months each, the running costs can be calculated as follows:
For the low season (taking 50% occupancy i.e. 125 rooms) =0.075*125*7*4*6=1575kW
for electricity=1575*0.5*16=12600 euros
The charges are the same for gas hence=12600 euros
The standing charges=electricity= =5840euros
Therefore, the total charges during the low season=19224.75euros
During the high season, the hotel is bound to have 100%occupaancy i.e. 250
Therefore, the electricity consumed=0.075*250*7*4*6=3150kW
The electricity charges=3150*0.5*16=25200euros
The same price for gas=25200 euros
The standing charges remain=784.5 and 5840, gas and electricity. Therefore, the running costs during the high season=57024.5euros.
Energy reducing measures
With the advancement in technology, various measures can be put in place to ensure that there is an on-site measure to reduce the energy costs of a building. Not only will these measures reduce the running costs of the building, they will also be a good move towards green building technology (The leadership in Energy and environmental design, 2007). Furthermore, they will reduce the impact of buildings on the non-renewable sources of energy such as oil. Oil has been the most common source of energy in most parts of the world because of the relative rudimentary aspect of technology. However, various studies are being conducted to ensure that the world minimizes the usage. Scientific research has proposed measures that will allow the oil bases of the various parts of the world to rejuvenate. Some of these measures include the use of solar panels, the use of biomass for energy production, wind power, geothermal power production, wave energy, ocean energy conversion, magnetohydronynamic energy, fusion among others (kibert, 2016). In this essay, we will focus on the solar energy, wind energy and the use of biofuels. The three energy sources are renewable which basically means that the sources are not easily depleted.
It is the most common source of power by the mere fact that most parts of the world experience sunny days. However, some parts of the world do not enjoy sufficiently long hours of sunshine which consequently reduces the intensity of the sunshine. Therefore, the suitability of this form of energy source is limited by the weather pattern of an area. The average incident solar energy received on earth’s surface is about600 W/rn2 but the actual value varies considerably (Kothari & Nagrath, 2009). Furthermore, the energy density of solar energy for any given area is very low compared to some other sources of energy .However, the advantages may overshadow these drawbacks. Some of the advantages of solar energy include the cheapness, the non-exhaustibility and the non-pollution factor (Swinbourne, 2017).
The major challenges that face solar technology include the aspect of harnessing, collecting and concentration with conversion of this form of energy by mechanical means into electricity also contributing to this quagmire. However, developments in the scientific as well as technological fronts have led to the design and implementation, though not on a larger scale, of two technologies. The first technology is that of a solar pond which as the name suggests, is founded on the concentration of solar energy on a pool of water. Engines which can run on low temperature are used to convert solar energy to electricity and currently. Israel produces a steady 150kW from 0.74 hectares (Lohnert, et al., 2003). The second technology basically depends on the concentration of solar energy on bowls that have concentrators raising the temperature to the possibility of running a steam engine. The steam engine is thereafter used to produce electricity. One of the challenges that arise in this technology is the ability to raise the temperature to the required levels. However, technological and scientific advancements can play a major role in ensuring that the two stated technologies can be used to effectively produce electricity.
The potential for electricity generation using solar energy is unlimited and as such, can be used to supplement the energy requirements of buildings. The electricity produced from solar energy can be used to reduce the electricity costs of buildings mainly in areas that experience long sunshine durations. Furthermore, this energy can be used to reduce the heating costs of building. The two are some of the solar technologies towards sustainable housing and settlement.
Biomass energy and electricity
It is a form of renewable energy that basically depends on the constituent matter of plants and animals. Plants and animals are composed of biomass which can be converted to biofuels such as methane gas, liquids in the form of propane and charcoal. All these can be used to generate energy for cooking, for heating the building and steam for running engines. Because of the ease of obtaining animal waste, the potential growth for this form of energy is enormous.
Because of the availability of animal waste in rural areas, programs that focus on biofuels and biomass can be implemented in these regions to reduce the energy as well as the electricity costs .One technology that has been vastly implemented in various rural parts of the world are biogas digesters. The biogas digesters are used for the production of methane gas which effectively reduces the heating costs of houses.
Wind energy may be regarded as the most abundant form of energy on most parts of the world because the basic determinant is the daily range of sunshine. Winds are produced as a result of varying temperature changes and as such, may cover a larger part of the world than solar energy. The major advantages of wind energy as a source of electricity and heat include the cheapness, non-exhaustibility nature as well as the non-pollutant cause. However, the undependable as well as the non-steady natures provide significant challenges to the use of wind as a source of energy. Some parts of the world such as India have devised control equipment that function when the wind speeds attain a certain target.Furthermore,there are equipment that have been used to generate constant power whenever there are varying wind speeds.
Wind power generation is suitable on small scales but the method may be only as effective as the wind and hence, suitable to be used with other methods of power generation.
Energy saving measures and sustainable design
As stated initially, design engineers have a huge task over their shoulders in ensuring that any building functions as effectively as possible while ensuring the emissions are as minimal as possible. The major aspects of appropriate design include ventilation, electricity usage, and construction materials among others.
To begin with, the design has to consider minimization of the heat gains and heat losses of the building (Charms & Bryant, 1984). Therefore, the ventilation requirements of the building have to ensure that the costs as well as the comfort of the occupants are met. The use of natural and hybrid ventilation can be regarded as to kill the two birds with one stone. However, the basic foundation of natural ventilation is the reduction in the use of mechanical ways of ventilation (Allard, 1998). Basically, ventilation in any building is meant to serve the following purposes: control the air quality, advective and personal cooling and indirect cooling at night (Schlueter & thesseling, 2009).
The major aspect of natural ventilation is the fact that it is cost effective because of the minimal usage of mechanical means of ventilation. There are a couple of natural ventilation systems that have been proposed in the recent past and include: wind driven cross ventilation, buoyancy driven stack ventilation and single sided ventilation (Allard, 1998). To begin with, the wind driven cross ventilation basically depends on the difference in pressure between the air inlets and outlets, situated at opposite sides, for air conditioning as well as removal of other pollutants that may be present in the building. On the other hand, the design of buoyancy driven stack ventilation depends on the density of warm and cold air for proper ventilation of the room. In this, the stack pressure obtained between the outdoor air and indoor air enables the latter to move into the chimneys where it is expelled into the environment. Therefore, the openings are located at high and low areas of the building. Finally, the single sided ventilation is used in single rooms where there are two openings, for inlet and outlet. The three natural ventilation mechanisms are cost effective because the major cost involved are on the ensuring that there is a window system that works on the difference in pressure and buoyancy of the inlet and outlet airs.
However suitable a natural ventilation may be, there is always the need to incorporate a mechanical system into the ventilation requirements of a building. The resultant system is known as a hybrid system. Though hybrid systems may be more costly and expensive than natural ventilation, the cost depends on the mechanical system used and the frequency of usage (Bradshaw & E, 1993). These systems may be best suited in climatic regions of the world where the summers and winters pose significant ventilation challenges.Insteasd of using a mechanical system throughout the year, a hybrid system may be put in place whereby the cooling and ventilation requirements in summer are met basically by the natural ventilation system while winter will combine both the natural as well as the mechanical system.
Heat losses are not limited by the use of proper ventilation measures, the ability of the building to retain heat is a crucial aspect for the design engineer to consider. Heat losses from a building occur through the walls, slab, and the roofs and as such the thermal properties of the materials used in construction play a crucial role in saving costs used for heating the building. However, these materials used in construction should be checked to ensure that the heat gains are not so significant that they may reduce comfort in the building. In the design of a roofing system, one method of reducing the heat loss may entail installing a 3⁄4- or 1-in-thick mineral fiberboard between roof deck and roofing (merritt & ricketts, 2001). On the other hand, a method of reducing the heat losses between the various structural members may entail designing the members with voids in them or putting epoxy in these voids.
Illumination in buildings and specifically in rooms is obtained through the use of natural as well as artificial lighting. However, artificial lighting has the disadvantage of increasing the heat gains in a room. By so doing, not only does the ventilation and the cooling requirements of the building increase, the materials that are used in construction are more likely to have a shorter life (Hardie, et al., 2012). Furthermore, the cost of installing these systems of lighting are very high and thus induce more strain on the economics of the building. Therefore, it is more advisable for any design engineer to consider natural lighting in the design plans. Natural lighting basically entails the usage of sunshine light or environment in the building. The major cost incurred will be on the windows and the ceilings. However, these costs will be very minimal compared to the costs likely to be incurred using artificial lighting.
Finally, smart buildings is a design concept that is still to be implemented. The smart building is fitted with various cables and optics that the building ‘itself’ can use to manage all the functioning. A smart building has the capability of regulating the internal temperatures as well as the air flows, therefore regulating the comfort levels brought about by heat gains and losses.Furthermore,these buildings will have the ability to check the electricity database to ensure that the most appropriate and cost effective supply routes are taken (Clarke & Randal, 1991).
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