In: Physics
A large, two-story office building has a first floor which measures 500 ft by 750 ft and a second story which is 500 ft by 500 ft. This building used 76,650 GWh of electricity last year and 120,035 therms of natural gas.
a) What is the EUI of the building? How does this compare to similar buildings?
b) Currently the office encourages carpooling and public transportation and therefore does not have a parking structure attached. They are considering adding this as an amenity to their employees. How does an unheated, 145,000 square feet parking garage change the EUI? How might this
impact an energy audit of the building?
c) By 2025, the company would like to add solar panels on the roof of the building to create on-site
electricity. These panels are projected to create a minimum of 20,000 kWh, annually. What is thebuilding’s new EUI?
a) The EUI (energy use intensity) of the building is calculated by dividing the total power consumed divided by the area of the building.
Here, the electricity consumed by the building = 76650 GWh = 76650*3.412*106 kBTU = 2.6153*1011 kBTU
The natural gas consumtion = 120035 therms = 120035*99.98 kBTU = 1.2*107 kBTU
So, total energy consumed in kBTU = 2.6153*1011 +1.2*107 = 2.61542*1011
The total area of the building = 500*750+500*500 = 625000 sqft
So, EUI = 2.61542*1011/625000 = 418467.2 kBTU/sqft
This value is much higher than the average EUI of 600 kBTU/sqft, for supermarkets, which consume the highest power for a day to day building.
b) Here, the parking garage is unheated. So, energy consumed by the building remains the same, while area is increased by 145000 sqft
So, new area = 625000+145000 = 770000 sqft
So, new EUI = 2.61542*1011/770000 = 339664.935 kBTU/sqft
Since EUI reduces, it would be good for the energy audit of the building.
c) Here, solar panels that produce 20000 kWh is to be installed in the building
So, the grid EUI will reduce, since less power is taken from the grid.
Power produced by the pnels = 20000 kWh = 20000*3.412 = 68240 kBTU
The power taken from grid = 2.61542*1011-68240 = 2.6154193*1011 kBTU
Considering that they already built the parking lot,
So, EUi = 2.6154193*1011 /770000 = 339664.844 kBTU/sqft