CHAPTER III: SIMULATING THE EFFECTS OF SEMI-TRANSPARENT SOLAR
3.4 SIMULATING VCCI TOWER IN REVIT 2016
3.4.1 Building information
VCCI Tower has 23 floors and 2 basements with the heights vary from 3 m for the ground floor and the mezzanine, 4.5 m for the 2nd floor to 5th floor, and 3.45 m each floor from the 6th to 23rd. Each floor has an area of 1,820 m2 with 52 m length and 35 m with.It has 220 mm brick external wall with alluminum along with double glazing with the Window to Wall Ratio (WWR) of 60%. The building faces southeast orientation with a small building next to it.
The model of VCCI Tower has been built based on its practical geometrical measurements and it is shown in Figure 3.10 below:
Figure 3.10: Using Revit 2016 to build VCCI Tower model
3.5 SIMULATING THE MODEL IN DESIGNBUILDER AND ADJUSTING THE OUTPUT RESULTS
3.5.1 Gathering practical data of energy consumption of VCCI Tower
According to a report of Ministry of Construction of Vietnam which was published in July 2014, the actual data of energy consumption for VCCI Tower was gathered during the period of 2008 to 2014. It was chosen to represent the typical office building in Vietnam due to it was designed with proper materials with the climate of Vietnam such as alluminum ceiling tiles, natural marble and granite with high aesthetic finish and long durability. Its
top to utilize the area for rent and help the owner to divide rooms to meet customers’ demands much easier. This trend of design has become more and more popular in Vietnam.
The results of the total energy consumption by sectors of VCCI Tower has been shown in the Table 3.3 below.
Table 3.4: The average monthly data of energy consumption of VCCI Tower during the period of 2008-2014
(Source: Trinh, H.V., Tran, T.V., 2014, retrieved from https://bit.ly/2tvTwxx)
According to the report, VCCI Tower is a multi-store office building with different materials and variety U values and SHGC. The external wall with alluminum outside has 2.2 W/m2.K of U value, the concrete has 1.86 W/m2.K, and the double glazing has 5.9 W/m2.K of U value and 0.52 SHGC.
3.5.2 Importing Revit model into DesignBuilder
The Revit model of the building was imported into DesignBuilder to run the simulation. After adjusting the thermal properties of the materials, the result of the model and its visualization are shown in Figure 3.11 and 3.12 below:
Figure 3.11: Importing Revit model into DesignBuilder
Figure 3.12: The visualization of the model in DesignBuilder 3.5.3 Running and adjusting the simulation
The study will focus on 4 criterias of the energy consumption data which are Chillers energy (Cooling energy), Total lights energy, Total equipment energy, and Total Fans interior. They take account of 84% the total end used energy every year:
Chillers energy (Cooling energy): 1018.7 MWh
Total lights energy: 1499.4 MWh
Total equipment energy: 1275.5 MWh
Total Fans interior: 3933.2 MWh
Figure 3.13: Input values of double glazing The simulation results are shown in the following Table 3.4:
Table 3.5: Simulation results of double glazing units
The total energies for cooling is 970.233 MWh, for interior lighting is 1479.746 MWh, for equipment is 1261.153 MWh, and for fans is 3858.921 MWh. Compared with the actual data of 1018.7 MWh (cooling), 1499.4 MWh (lighting), 1275.5 MWh (equipment), and 3933.2 MWh (fans). The results are quite accurate to the practical data.
3.5.4 Simulating the performance of BriteSolar’s product on the energy balance of VCCI Tower
Since there is no real model about the building, the method is to keep every properties of the simulation as constants (cooling temperature, heating temperature, floor area per person, metabolic, schedules, etc) and change only the properties of glass to take the simulated results of energy performance of BriteSolar’s STPV panel. That is believed to be
Figure 3.14: Adjusting the properties of BriteSolar STPV panel
The results of the energy consumption and energy generated while applying BriteSolar’s glass are shown in Table 3.5 and Table 3.6.
Table 3.6: Energy generated by BriteSolar glass
Table 3.7: The energy consumption of VCCI Tower with BriteSolar glass
The figures indicate that cooling energy decreases from 1018.7 MWh to 834.624 MWh (decreased 18.07%), interior lighting energy increases from 1499.4 MWh to 1644.162 MWh (increased 8.8%), fans energy slightly decreases from 3933.2 MWh to 3855.735 MWh (decreased 1.97%) due to the changes in U value, SHGC and Visible Transmittance. Only equipment remains the same since the schedule and number of equipment do not change.
Besides, the solar panels do generate 143.08 MWh every year.
CHAPTER IV: ANALYZING THE FEASIBILITY OF APPLYING STPV GLASS INTO THE BUILDING
4.1. GATHERING INPUT PRICES
4.1.1. Double glazing
The building was coated with the double glazing which is common in Vietnam. The price before tax of this type of glass is VND 650,000/m2 ($28.55/m2). Its durability is 25 years. With the total area of 8413.935 m2, the total cost for double glazing is $240,217.844.
4.1.2. BriteSolar panel
BriteSolar is providing STPV glass with a cost of €50/m2 ($58.55/m2). The transport price from China to Vietnam is VND 16,000/kg ($0.7/m2). The government does not give any other tax on it except VAT of 10%. Since the total area applying BriteSolar panels is 8413.935 m2 then the total price of STPV panels before tax is $498,525.65.
Since the durability of this product is guaranteed to have at least 90% after the first 10 years and at least 80% after the next 15 years then the life cycle of this product is considered as 25 years.
4.1.3. Inverter
After STPV panels convert solar radiation to electricity, it will have to go through an inverter which is an electronic device that changes the direct current to the alternative current to fit with the grid or the facilities inside the building. Since this is a large building and the price of battery is high so it is not supposed to be installed in this system. The best choice is
Due to the total amount of electricity generated by STPV panels in VCCI Tower is 143.08 MWh then we have to choose inverters which have at least 143.08 MWh of capacity in total. The peak sun hours during a day that STPV can generate power in north Vietnam is from 9h30 to 14h30, 5 hours.
The proper inverter would have at least 110 kW in capacity since the total power it can convert for 1 year with 80% efficiency is: 110 x 5(peak hours) x 0.8 x 365 (days) = 160.6 MWh.
In Vietnamese market, there are variety of type of inverters with a range of capacity.
One inverter of the model ABB ACS550-01-195A-4 110kW with a price of VND 94,322,288 ($4143.3) would be enough for the system.
The durability of this type of inverter is 5 years.
4.1.4. Cost of energy
The price of electricity in Vietnam for office building in 2018 is shown in Table 4.1:
Table 4.1: Vietnam Electricity tariff (2018) From 6 kV to 22 kV (per kWh)
Normal hour VND 2,426 (US$ 0.106)
Off-peak hour VND 1,428 (US$ 0.063)
Peak hour VND 4,061 (US$ 0.178)
The peak time is from 9h30 to 11h30 and from 17h to 20h. Off-peak time is during the midnight and the left is normal hours.
According to the report, the equipment has been used 100% from 6h to 20h every except Sunday, holidays (Figure 4.2) then the average amount of electricity for equipment in 1 hour is A (kWh). The total amount of energy for equipment in 1 day is 14A (kWh).
Figure 4.2: The operating schedule of equipment in VCCI Tower (100% from 6h to 20h)
It can easily be seen that 100% of the equipment of this building work during the peak hour of 9h30 to 11h30 and 17h to 20h. The other time is in normal hour. In conclusion, equipment use 5A kWh in peak time and 9A kWh in normal time.
The energy for cooling, lighting, and fan varies by the number of people inside the building. From the report, it is shown that there is 50% people from 8h, it goes to 100% from 8h30 to 12h, then 75% staffs will have lunch outside until 13h they will come back and work until 17h. People start leaving the building from 17h to 20h. (Figure 4.3).
Figure 4.3: The schedule of number people inside the building by time (Source: Trinh, H.V., Tran, T.V., 2014, retrieved from https://bit.ly/2tvTwxx)
Assume B (kWh) is the average amount of energy for cooling, lighting, and fans in 1h with 100% of people inside the building then the average amounts of electricity by time
(Number of people in the building) x (Number of hours)
Then the total amount of energy for cooling, lighting, and fans in 1 day is 9B (kWh) includung 3B peak hour and 6B normal hour. In summary, 1/3 of the energy consumption in a year is in peak hour and 2/3 left is in normal hour.
In terms of the power generated by the STPV panels, they can only generate power during the time of 9h30 to 14h30 (5 peak sun hours) in a day on average. As we know, 9h30 to 11h30 is the peak hours and the rest is normal hours so 2/5 of the power generated by STPV glass is in peak hour and the other 3/5 is in normal hour.
4.1.5. Calculating the costs
The costs were calculated in the previous parts:
- The price of double glazing units was shown in 4.1.1, page 53: $240,217.844 - The price of BriteSolar’s glass was shown in 4.1.2, page 53: $498,525.65
Besides, the costs of energy consumption by applying double glazing units, BriteSolar glasses in a year and the amount of money that can be sold from generating power by STPV panels in a year are indicated below by multiplying the amount of energy consumption by the unti price of electricity in peak hours and normal hours:
- The price of energy consumption by applying double glazing units in a year:
(5
14 x 1,275,500 + 1,018,700+1,499,400+3,933,200
3 ) x 4061 + [9
14 x 1,275,500 + 2
3 x(1,018,700 + 1,499,400 + 3,933,200)] x 2426 = VND 23,005,980,000 = $1,010,585.55
- The price of energy consumption by applying BriteSolar glasses in a year:
(5
14 x 1,275,500 + 834,624+1,644,162+3,855,735
3 ) x 4061 + [9
14 x 1,275,500 + 2
3 x (834,624+1,644,162+3,855,735)] x 2426 = VND 22,659,030,000 = $995,345.05
- The amount of money saved by generated power from STPV panels in a year:
2
5 x 143,080 x 4061 + 3
5 x 143,080 x 2426 = VND 440,686,400 = $19,358.07
Due to the efficiency of it decreases by time and it is guaranteed to have at least 90%
efficiency after the first 10 years and 80% efficiency after the next 15 years (year 25) then it will be divided into 2 periods of the first 10 years and the next 15 years to calculate. It is assumed that the efficiency decreases gradually during those periods.
During the first period of 10 years, it decreases 10% then every year it decreases 1%
which is 1.4308 MWh. It costs VND 4,406,864 = $193.58.
During the next 15 years, it decreases 10% then every year it decreases 0.67% which is 0.8585 MWh. It costs VND 2,644,180 = $ 116.15
4.2. CALCULATING THE NET PRESENT VALUES OF TWO ALTERNATIVES Choosing the interest rate
The calculations are based on the case that all of the costs will be paid by the owner’s money, there is no loan from bank in this study. The chosen interest rate would be at least the same as the interest rate that the banks are offering to people who save money in it. The newest interest rates that are given by a variety of banks in Vietnam are shown in Table 4.2.
Table 4.2: Interest rates in Vietnam (updated April 2018) (Source: https://bit.ly/2KcagEu)
According to the table, the average of interest rates is 7 % while Eximbank is giving the highest interest rate of 8%. It is reasonable to take the interest rate of 10% (8% + 2% for risk) in this study.
Financial result of applying double glazing units
For 25 years life span of double glazing, the owner has to pay the cost of buying
Figure 4.4: Cash flow diagram of VCCI Tower with double glazing units
Then the net present value of the alternative of applying double glazing glasses is:
NPVDG25 = -240,217.844 - 1,010,585.55 (1+0.1)
25−1
0.1(1+0.1)25 = - $9,413,343.32
For all the life cycle of the building (50 years), with 25 years durability of double glazing, it has to replace all the double glazing once at the end of year 25, it is assumed that all the prices and performances remain the same, the net present value would be:
NPVDG50 = -9,413,343.32 - 9,413,343.32 x 1
(1+0.1)25 = - $10,282,157.2 Financial result of applying BriteSolar panels
For 25 years life span of STPV glass, the owner has to buy the STPV glasses and inverter first and then reinvest inverter every 5 years due to its life cycle of 5 years. The owner also has to pay the bills for the power consumption of the building and take profit from selling electricity generated by the STPV glasses.
Figure 4.5: Cash flow diagram of VCCI Tower with STPV glasses Then the net present value of the alternative of applying BriteSolar glasses is:
NPVSTPV25 = -498,525.65 - 4143.3 - 995,345.05 (1+0.1) glass, it has to replace all the STPV panels once at the end of year 25, assume that all the prices and performances remain the same, the net present value would be:
NPVSTPV50 = -9,379,425.7 - 9,379,425.7 x 1
(1+0.1)25 = - $10,245,109.2
CHAPTER V: CONCLUSION AND RECOMMENDATIONS
5.1 CONCLUSION
The study estimated the energy performance of an office building in Hanoi called VCCI Tower in a year applying semi-transparent photovoltaic panel glasses. The case study STPV panels have 70% transparency, U value of 0.84 W/m2.K, SHGC of 0.52, and 3%
efficiency. The results show that it is potential to have at least $37,048 saving money, from
$10,282,157.2 of the net present value of applying double glazing units in 50 years to
$10,245,109.2 of the net present value of applying STPV panels. Although the amount of money saving is still low but the technologies of inverter and STPV glass have still been developed. In the future, it is undoubtedly that there will be more supplier with a variety of products that have higher and higher efficiencies and the costs will certainly be lower and lower. Even in this study, PolySolar and Ubiquitous confirmed that their current products can already achieve up to 12% (4 times higher than the case study product).
Besides, the results also prove that this kind of technology is suitable to be applied in all the region of Vietnam since the amount of solar radiation in the north region, where VCCI Tower is located is lowest among 3 parts of Vietnam, lower than central and southern parts.
The field of energy consumption for the building has not been considered properly by both the designers and the owners. They have been giving their attentions on the initial phase of building the construction. However, operating the building in its entire life cycle are so important and it should not be skipped.
5.2
RECOMMENDATIONS
It is obviously that the technology of semi-transparent photovoltaic glass has high potential to be applied in the building. Among with the process of developing it has been continuing, the efficiency, the U value, the SHGC, and also the visible transmittance will be improved in the future. Recently, scientists have invented the next generation of photovoltaic glass which is called the fully-transparent photovoltaic glasses with remarkable efficiency performance. It looks totally similar to regular glass and can be applied to the facades of the building to generate power. Furthermore, scientists believe that it can be replaced the screen of mobile phone with its amazing capabilities. That kind of technology has still not been provided in the market and only be produced in small scale for experimental purposes at the moment but it has certainly opened the door for further studies about the potential of generating solar power on the building. It could help decreasing not only the power consumption, the money but also giving a hand to reduce the greenhouse effect which has caused a lot of natural disasters such as flood, drought, typhoon, etc.
Besides, in order to achive the best effectiveness of applying this kind of technology to the building, it is essential to find the proper WWR and the way to design the area of STPV panels in the facades of the building in different directions.
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