Introduction
The building sector is changing remarkably with the design and construction of buildings taking considerable effort to reduce the energy consumption as well as decrease the greenhouse emissions. However, there are various types of buildings for various purposes such as residential, industrial etc. Therefore, the design engineers should ensure that the design does not alter the usage while still maintaining the efficiency (Al-Homoud, 2005). The following is a design that focuses on the energy input and output of a building that serves the purpose of a hotel as well as a conference. The building has 12 floors and the capacity of 250 beds.
Design
Electricity usage for a single room (assuming all the rooms are the same)
In our design, we will consider lighting of rooms as the main energy usage for the building. However, because there is the natural light as well as artificial lamps, the lighting hours may be between 1800 hrs. And 0800 hours=14 hours per day, 7 days a week and 48 weeks a year
Time that the lights are used= =4704hrs/year
The floor area to be illuminated=37.162 square meters
The lighting data will determine the electricity usage for a single lamp. Taking a 100w incandescent GLS lamp with an efficacy of 18l/W and taking the illuminance of a dwelling which is about 150lx.Also taking a light loss of 50%.
Installed lumens= =11148.6lumens
Input power= therefore the total electricity consumption=0.619 =154.84kW
The heat losses from the building
The standard hotel room is estimated as 400 square feet (37.1612 square meters). The heat loss from this standard room mainly occurs through radiation from the walls to adjacent rooms and to the environment (Per kvols, 2000). Heat loss can also occur through windows and as such, a good estimation can be obtained from the energy necessary to warm this room (de Souza, 2013).
Considering a square room where the length =width =6.1 meters. The room height can be approximated to about 3 meters. Each room is to have two windows for proper ventilation. Furthermore, the floor is another important aspect in the design of buildings with different floors having varying levels of surface resistance as follows: the sheltered floors have minimal surface resistance(the maximum number of floors is 3 and these buildings are in city centers),normal surface resistance and this includes buildings that are located in suburban and rural areas with the number of floors between 4 and 8 for buildings in city centers, and severe surface resistance which occurs from the fifth floor in suburban areas and floors above the ninth in city centers (Kreith, 2001).
Heat loss through the four walls
In our design, we will have to consider that the exposure is normal and as such, the thermal transmittance of the basic components is as shown below.
The heat loss from any building is given by the heat loss of the individual members given by the formula
Where: A is the area of the building element
U is the thermal transmittance
The internal and external air temperatures respectively

Element Area U AU
Walls 18.3 1.90 34.77
Roof 1600 2.6 4160
Floor 1600 Suspended=12
Solid=0.22
2304
352
Windows 2.5 by 2.5 meters 5.7(aluminum frame with thermal break) 35.625
 
       =33321

 
The total area of the floor has been estimated to be about 1600 considering balconies and the hallways that serve to make the stay all more comfortable. Furthermore, the roof area has been approximated to be the same as that of the floors. Another basic assumption is the air temperature of the room which may be taken as
 
 
 

  Daily Insolation (kWh/m2) Wind Speed ground level (m/sec) Wind Speed at 50 m (m/sec) Ambient temperature (°C)  
January 1.84 2.3 3.4 4.5 15.5 516475.5
February 1.91 1.7 2.5 5 15 499815
March 1.99 2.1 3.1 6.4 13.6 453165.6
April 2.03 1.5 2.2 9.2 10.8 359866.8
May 2.42 2.2 3.3 9.9 10.1 336542.1
June 3.66 1.7 2.5 13.7 6.3 209922.3
July 3.41 1.5 2.2 17.4 3.4 113291.4
August 3.39 1.7 2.5 14.4 5.6 186597.6
September 2.66 1 1.5 13.1 6.9 229914.9
October 2.06 1.2 1.8 11 9 299889
November 1.89 1.8 2.7 8.2 11.8 393187.8
December 1.82 2.6 3.9 7.8 12.2 406516.2
Average 2.42 1.78 2.65 10.05    4005184.2watts

 
The heat lost the whole year due to varying temperatures=4005.18kW
The heat gains
Heat gains to a building can take two forms: sensible heat gain and latent heat gain (Schlueter & thesseling, 2009). The former refers to heat gains to a building resulting from ventilation, heat conduction from the outside, electrical appliances, industrial processes among others while the latter refers to heat gains attributed to basic human processes such as breathing, exhalation etc. (Attia, et al., 2012).Specific heat gains are calculated as follows: specific heat gain=specific heat
Where SH is the specific heat gain
Q is the air mass flow rate
Recirculation and supply air respectively

Source Quantity Specific heat
Windows 2.5 by 2.5 by the insolation Check the table
  Daily Insolation (kWh/m2) Specific heat gain
January 1.84 11.5
February 1.91 11.9375
March 1.99 12.4375
April 2.03 12.6875
May 2.42 15.125
June 3.66 22.875
July 3.41 21.3125
August 3.39 21.1875
September 2.66 16.625
October 2.06 12.875
November 1.89 11.8125
December 1.82 11.375
Average 2.42  181.75 for a single window

Therefore, the sensible heat gain for a single room= =363.5 watts
The whole building therefore =90875watts
 
Running Costs of the building
Annual electricity consumption to be used by the occupants=154.84 52012.8kW
The total cost of energy is based on the hotel occupancy and as such, during the low season the costs should be relatively lower compared to the high season.
Low season taking 50% accommodation=125 bed occupancy
Power consumed =0.619 =15165kw
Total cost of electricity= 121324euros
Total cost of gas=121324euros
Standing charge of electricity= =5840
Standing charge of gas=365 =784.75
Therefore, the annual bill during the low season=249272.75
 
During the high season
Taking 100% bed occupancy, total power consumed=0.619 =21665kW
Total cost of electricity= 173320euros
Total cost of gas=173320euros
Standing charge of electricity= =5840
Standing charge of gas=365 =353264 euros
Solar panels wind turbines and biomass energy production
Solar panel may be used to supplement the energy requirement s of a building (The leadership in Energy and environmental design, 2007). By doing so, not only will the emissions resulting from large scale production of electrical energy reduce, there will be an increased usage of green technology. Basically, solar panels convert solar energy to electrical energy and as such, provide a very efficient means of green energy. Energy requirement swill necessitate the use of solar panels and is also an important part of saving on the energy costs of a building. The other application of solar panels is the heating of water for consumption. The major advantages of solar energy production is the cost free nature, pollution free as well as the non-exhaustibility (yildiz & gungor, 2009).On the other hand, the major disadvantage are the lower energy densities per area and being subject to weather conditions. Therefore, by basically introducing solar energy to the building infrastructure, the energy costs will be reduced and there will be a profound effect on the environmental conservation by this form of energy.
Electricity is produced by various renewable as well as non-renewable sources. However, the non-renewable sources are the major contributors to greenhouse gases (Woloszyn, 2000). On the other hand, renewable sources include hydroelectric production and wind turbines. Basically hydroelectric power station convert the energy in the water to electricity while turbines convert wind energy to electricity and energy and as such, provide a very good base for energy and electricity production. Wind energy provides a very cheap method of electricity and energy production, just like solar energy. However, this may be limited to the site conditions and as such, the designers need to make sure that the energy production conforms to these site conditions.
Biomass is an important source of cooking heat, crop drying, comfort heat and providing the necessary steam for electricity production.basically,the biomass is burnt which initiates chemical and biological processes that basically produce other biofuels such as methane, propane etc.  In India, the potential for bio-Energy is 17000 MW and that for agricultural waste is about 6000 MW (Kothari & Nagrath, 2009). It is thus an indication of a comparatively better way for energy production in buildings as well as a more as a program that can meet the need for the increased demand in buildings
Energy saving measures and sustainable design
Fossil fuels are the primary means of generating energy. However, these fuels are responsible for an enormous amount of carbon emission which means that they play a huge role in global warming and the production of greenhouse gases. In essence, the engineers responsible for the design of buildings should focus more on building systems that tend to use fossil fuels at a much lower scale. The systems basically revolve around ventilation and heating. However, the constraints to this efficient design are limited by the finances. The design engineer has to consider the funds behind any project in order to establish a blueprint for the design of a more energy conservative system. In the design of the building, the energy saving measures may include both the manual and automatic systems which basically means varying costs.
The three components that basically form the foundation for energy saving are: the primary design, measures for maintenance and retrofitting energy saving measures (Chadderton, 2007).Furthermore, it is the responsibility of the building owner to ensure that there are efficient energy measures implemented .In this, the two primary reasons that may lead to this investment after an initial design include: the owners decision to renovate the building which may be as a result of him/her either obtained the required capital or has been funded, or the cost of operation of the energy facilities in the building are greater than the returns. If the energy facilities pose a significant challenge to the conservation of the energy, the owner may decide to invest more into upgrading the current system.
Still on the aspect of energy savings, it is important to note that the buildings of the future will be smart such that they will have a very different configuration on the aspect of the architecture. Furthermore, these buildings will have the capacity to manage themselves (Per kvols, 2000). All this will be possible because of information communication. (Lucent Technologies, 2000).Therefore, intelligent buildings with plug and play controls will exhibit lower startup costs, fewer problems, increased comfort, lower O&M costs, greater adaptability to changing needs, and increased energy efficiency (Chadderton, 2007). There are basically two factors that call for intelligent buildings and these are; energy saving and the environment.
The ability of any building to search the internet and compare the prices of electricity may be a far-fetched idea to most but this can actually happen in intelligent buildings. More to this is the fact that this technology will also enable buildings to select a variety of options when it comes to the electricity available (Clarke & Randal, 1991). Some of the properties may include: the extent of emissions, the green factor etc. All this is for the future with the main endplay to save on the cost of energy production as well as reduce the emission from buildings. However, this may be observed first in industries and other sectors with the idea of an intelligent residential house still at a distant.
The use of a hybrid system for ventilation is one way to be energy efficient (Emmerick & Dolls, 2001). This will entail using the natural circulation of air to offset heat gains to a building. By doing so, the amount of energy saved will be astounding and as such, a reduction in the emissions as well as cost of energy. Major strides have been made towards optimizing the use of natural ventilation and liberty tower is a major indication of this. By ensuring that there is a wind floor that ensures the continuous distribution of natural air throughout the floors, the energy costs are reduced tremendously (Wilkins & Hosni, 2000). Furthermore, this system has ensured that there is stability of wind forces throughout the year primarily by providing four exits. Another important aspect is consideration for smart winmdows.The smart window has various aspects of ensuring an energy efficient building, from daylight saving to the mechanical circulation of air (Tallinn, 2001). This part of the design, much like the smart building, is a tool of the future and will ensure that the comfort of the building as well as the energy saving measures are provided.

References

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