Energy Analysis For A Hotel And Conference Facility In Glasgow

The construction sector is responsible for a large amount of greenhouse emissions that have a detrimental effect for climate change. Thus the traditional role of buildings as a shelter is beginning to change with increasing emphasis on lowering energy consumption.

Taking into account the above, a progressive client has approached you to do a thorough energy analysis of a 12 storey, 250 bed hotel and conference facility at the identified city centre site in Glasgow [ refer to the project brief on page 3].  For this report are asked to do the following:

• Perform a full energy audit of the building including electricity usage, heat losses and heat gains assuming that the building follows the latest building regulations - but only barely (U-values are the highest permissible)
• The building will be connected to the electricity grid and gas mains and the manager has negotiated a rate of 16p/day standing charge plus 9.8p/kWh for electricity and 16p/day standing charge plus 2.15p/kWh for gas. Calculate the running costs of the building during a high season (June-September and December-January) and a low season (October-November and February-May) taking into account different usage patterns (low hotel occupancy for low season and high hotel occupancy for high season)
• Investigate the possible on site usage of solar PV, wind turbines and biomass boilers in order to reduce electricity and heating costs.
• Discuss your findings and propose how energy saving measures and sustainable design could help offset the running costs. These can include but are not limited to: better insulation, more low energy saving devices, increased use of natural light etc.

Design of the hotel

Without proper design technologies and practices, the increase in temperature coupled with the increase in sea levels will never change. The main reason for this judgement is the fact that the building sector is contributing enormous amounts of greenhouse gases. The production of these gases is because of the increased energy usage in buildings without provision of the necessary precautionary measures. However, technology has improved remarkably and there are various renewable energy technologies with far less consequences on the environment.Therefore,it is important for any building designer to consider the environmental effects of the energy consumption of the building.

Design of the hotel

Buildings are designed for comfort and safety. Considering comfort, heat losses and gains are a major factor (Attia, et al., 2012). The comfort of any building will be determined by the heat control measures taken to ensure that the heat gains and losses are within the desirable range. As a matter of fact, there should be proper ventilation measures to ensure proper air flows because air is the major controller of environmental and building temperatures (Woloszyn, 2000).

The determination of all these heat gains is demonstrated in the following design of a major hotel in glascow.The hotel has a bed capacity of 250 and has a conference room as well. However, considering that this hotel is at the heart of Glasgow, the rooms must be of deluxe sizes (from 500 sq. feet to 1000 sq. feet).As in our design example, we will consider a room size of 600 square feet (55.74 sq. meters)

The weather data for the whole year is indicated below

Electricity usage

In this design example we, will consider that the number of rooms is equal to the number of bed spaces available. Therefore, the number of rooms =250

The area of the room =55.74sq.meters.taking the rooms to be square where the length=width=7.4 meters. However, the height may be taken as 3.5 meters. We will take that the building has two windows per room each window 2.5m=length=width.

The lighting system can be designed in such a way that the artificial lights are on from 1600hrs to 0800hrs.therefore, the duration of lighting per day=16 hours which totals to 5376hours per year.

In this particular case, the illuminance required may be approximated to that of a dwelling which can be approximated to

The lamp that can be used basically in each hotel room is fluorescent warm white with an efficacy of 85lm/W, energy 100 watts. We may further consider that loss of light factor is 70%

Therefore, the installed lumens= 

Therefore, the power used by the lamp= 

The total electricity consumed for the building considering the lighting only=92.4 =23.109kW.

This power consumed could be higher depending on the number of appliances used and the number of bulbs used in each room.

Heat losses

The heat loss from a building mainly occurs through the fabric of the constituent elements (de Souza, 2013).However, the major factor that leads to this loss is the temperature difference between the internal and external environment. Therefore, the major processes that heat is lost are radiation and convection (merritt & ricketts, 2001).

Electricity usage

Some of the measures that are taken to reduce heat losses include: using an insulating layer and materials that have lesser thermal conductivity. The walls, the slab, the windows, the doors all play a major role in heat losses. As a fact, their thermal transmittance is the most useful value when calculating heat losses (Al-Homoud, 2005). In this, the accumulative heat losses from all the elements is found by the formula:  where A represents the area of an individual element, U is the thermal transmittance and the terms  represent the temperatures within and outside the room respectively.

The tables below shows typical U values for the various elements

Therefore in our design example, we will have to consider all the elements and their areas.

Windows taken are double glazing aluminum frame with thermal break

The doors are taken as being 3m in height and 2m wide

Taking the internal temperature as 25 degrees Celsius, the total heat loss over the 12 months can be calculated as follows

Therefore, the building loses approximately 1735.594kW annually

Heat gains to the building

Ventilation is a requirement for every building.  Ventilation is responsible for ensuring that the heat losses and heat gains within the building balance out. As with heat gains, there are two types that buildings can experience: sensible heat gains and latent heat gains (yildiz & gungor, 2009). 

Sensible heat gains result from :solar radiation, conduction from outside to inside during hot weather, warm ventilation air, lighting, electrical machinery and equipment, people and industrial processes (Chadderton, 2007).On the other hand, latent heat gains are as a result of moisture that comes from people and other processes, either industrial or mechanical (Lohnert, et al., 2003). In comparing the two, the former affects the building because they alter the temperature of the air while the latter do not. The primary reason why the latter does not affect the temperature is because it mainly deals with the transfer of moisture (Per kvols, 2000).

With the design of the hotel, we will consider the sensible heat gains: from the electricity and from the windows through insolation.

Electrical supply=100watts (check the specification of the lighting)

The total sensible heat gain from the windows = 

Therefore, the sensible heat gain from the two can be calculated as below

The whole building will gain a sensible heat of 390.875kW

The running cost of the building depend on the electricity consumption. However, it is expected that during the high season the electricity will be at a much higher usage than during the low season. Regardless of the season, the standing charge will remain.

During the low season, the occupancy rate may be assumed to come to about 30%.with the number of months 6.However, during the high season, the occupancy rate can be taken as 100%, with the number of months 6.Therefore, the electricity and gas usage can be calculated as follows:

0.0924 0.03  1164.24kW

The amount of cash needed= 9313.92euro

The bill of supplying the gas= 9313.92 euro

The standing charge of the power supply remains constant and as such= =5840

Heat losses

                                                     Gas=365 =784.75euro

The amount needed assuming a 30% occupancy rate is 25252.34euros

During the high season the 250 bed spaces will be occupied and as such

0.0924  38808kW

The amount of cash needed for electricity= 31046.4euros

The bill of supplying the gas= 31046.4 euros

The standing charge of the power supply remains constant and as such= =5840

                                                     Gas=365 =784.75euro

The total amount of money needed=68717.3 euros

Solar PV, wind turbines and biomass boilers

Supplementary energy supplies are always a good investment. The main advantage of this is the likely possibility of a reduction in cost as well as a reliable system that ensures that failure of one system does not necessarily mean loss of power and energy. To begin with, The  average incident  solar  energy  received  on  earth's  surface  is  about 600  W/rn2 (Kothari & Nagrath, 2009).that stated, the solar energy sector has a potential to provide supplementary onsite energy demands.However,this solar energy depends on the weather patterns and as such, it may only be efficient on areas that are less cloudy and have longer duration of sunshine hours. A number of research has been conducted to determine the most economical and viable means of converting solar energy and currently there are two breakthroughs.

One breakthrough in solar energy technology has led to the creation of bowls that have concentrators which can be exposed to sunlight in order to gain temperatures as high as 700 degrees Celsius (Lohnert, et al., 2003).later on, the bowls can be used in a heat engine in order to produce electricity. However, this design is complicated and as such, very affluent building owners may manage to provide this facility for onsite generation of heat and electricity (Lawson, 2006). The second technology basically involves the collection of solar energy by a solar pond that is attached to an engine that operates at low temperature and which consequently produces steam that can run a generator for electricity production.

Wind power is available in abundance and as such, the building sector should incorporate this form of supplementary energy in the design blueprint (Baccarini, 1996). Winds are created by differential heating of the earth surface and may therefore be an alternative for solar energy. However, various research programs have tried to examine the feasibility of wind power generation but the response has always been that there is no techno economic satisfaction (Austin, et al., 1999).

Just like solar energy, wind energy has a number of advantages as well as disadvanbtages.Some of the advantages include the non-polluting factor, the availability, and inexhaustibility among others. However, this form of energy production is very unpredictable with varying strengths of wind producing different frequencies of electrical power. Therefore, wind power is suitable for small and isolated areas (Charms & Bryant, 1984). Therefore, the energy demands of the building determine the size of the project.

Finally, there is the energy that can be produced by biofuels. Biofuels are produced when biomass are subjected to  chemical and biological processes through heating. The major advocate for this type of fuel is the fact that plants and animals are composed of biomass. Therefore, because of the availability in biomass, a supplementary source of heat for cooking and steam production for electricity generation can be easily obtained.

Heat gains to the building

Running costs of building

It is important for any designer to ensure that the running costs of the building are maintained at a minimum. By integrating technologies that use the natural environment more, there is a significant reduction in the amounts that will be used during the operations of the building. Furthermore, this will be an environmental oriented move because there is bound to be decrease in the emissions and consequently a decrease in the greenhouse gases produced (kibert, 2016)

The use of hybrid ventilation cannot be overemphasized. This technology is for the future because it basically contains all the ingredients in the reduction of the running costs as well as ensuring the environment remains unpolluted. The basic principle of operation of hybrid ventilation involves making use of the difference in external and internal air temperature in ensuring that there is a continuous flow into and out of the building (Rounce, 1998). However, hybrid technology comes with some demands such as a mechanical system to be used whenever the air conditions are unfavorable.

Cooling devices such as heaters and boilers increase the running cost of a building. Therefore, designing the building in such a way that the need for such devices will be at a minimal is a really feasible and economic option. In this, special design will have to be considered for the windows and the walls. Windows may be designed in such a way that the energy lost through them is at a minimal. However, the design should also consider the ventilation requirements of the room. On the other hand, walls may be designed in such a way that there are voids to reduce the heat lost through radiation and conduction.

References

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