Monday, October 31, 2011
Step 5: Assume standard appliance profile and occupancy for the home. Make a list of all the energy uses other than heating and cooling for your home.
The total electricity needs is approximately 34.72 BTU per year, or 1.18 kW.
Step 4: Now determine the total heating and cooling energy needs for your home using the equations developed in class for thermal envelopes. Data for temperatures and wind conditions can be obtained on the web (monthly averages are sufficient)
The total heating and cooling energy needs of our home for an entire year can be found using the equations discussed in class for thermal envelopes:
cp= 0.241 BTU/(lb*F) for air
QHeat= (UA + mdotcp)HDD = 65.7 x 10^6 BTU per year = 2.2 kW
QHeat =65.7 x 106 BTU per year = 2.2 kW
QCool=(UA + mdotcp)CDD + Qlatent = 7.36 x 10^6 BTU per year = 0.25 kW
cp= 0.241 BTU/(lb*F) for air
QHeat= (UA + mdotcp)HDD = 65.7 x 10^6 BTU per year = 2.2 kW
QHeat =65.7 x 106 BTU per year = 2.2 kW
QCool=(UA + mdotcp)CDD + Qlatent = 7.36 x 10^6 BTU per year = 0.25 kW
Step 3: Assume standard air exchange for homes. What is the ventilation rate for your home?
Assuming standard air exchange for homes, we will calculate the ventilation rate for the home. The density of air is about 0.075 lbm/ft3 at 70 0F. By using the volume of the house of 8000 ft3 and neglecting the area taken up by the objects in the house and the walls separating the two rooms, we can see that 619.6 lbm of air is in the house at all times. We will say that 40 percent of the air needs to be circulated to prevent stagnant air, which is a valid assumption. Also, this air change per hour is assumed to be 2 times, so 48 times over the course of a day.
mdot = (619.8 lbm)(0.40)(2 times per hour) = 495.7 lbm/hr = 8.26 lbm/min
mdot = (619.8 lbm)(0.40)(2 times per hour) = 495.7 lbm/hr = 8.26 lbm/min
Ventilation rate = Q = mdot/density of air = (8.26 lbm/min)/(.075 lbm/ft^3) = 110 CFM
Step 2: Determine the heating and cooling degree days for a typical year
Next we will determine the heating and cooling degree days for a typical year. These values help is find the amount of energy that will need to be supplied to the house over the entire year. First we will look at the cooling degree days (CDD). We will reference the Iowa Environmental Mesonet [40] to get averages from 1951 until 2011. The average number of CDD is about 1045 and cooling days typically are needed between the months of April and September. Heating degree days (HDD) are taken into consideration for all months except for June thru August. The average for HDD is taken to be about 6140 for a typical year.
Step 1. List the R-values of the building materials and compute the overall thermal conductance of the home
Let’s say we want to design a way to heat and cool a house in Iowa City, IA using renewable energy. For a simple analysis we will say that the house is a 1 story, 2-bedroom, 1000 square foot home. The design will be planned around the goal of maintaining an interior temperature of 70 0F. We will assume that there is no basement, and therefore we will not consider heat flow in or out of the bottom of the house(adiabatic). We will also assume the overall dimensions of the house are as follows: base of the house is 25 ft x 40 ft and the walls are 8 feet tall. Next, we assumed that windows in the house can be neglected. The ceiling and the four exterior walls will be modeled using the same R-values as those used for a wood construction wall. This is a valid assumption because a typical R-value for a ceiling is usually between 10 and 15 (hr*ft^2*F)/BTU . Below is a figure that shows the generic components of a wall along with their specific R-value and the R-value of the wall assembly as a whole. [39]
As shown in the figure, the total one wall assembly R-value is 13.31 (hr*ft^2*F)/BTU. When we set R1=R2=R3=R4=R5=13.31, find the area of the exterior walls to be 1040 ft2 and the area of the ceiling to be 1000 ft2, we can then find the overall thermal (UA) conductance of the home. UA = (1/13.31)(5)(25*40+2*8*40+2*8*25) = 766.4 Btu/(hrF)
Sunday, October 30, 2011
Pick a project. What is the LEED rating of this project and what made this project LEED certified?
The 2,216 square foot Chipotle Mexican Grill in Gurnee Mills, Illinois is an example of LEED retail and was granted LEED Platinum certification on May 18, 2009. For LEED retail, the maximum possible points you can receive is 71; Chipotle received an astounding 53. The following is a breakdown of how Chipotle received its points: 10 out of 16 for sustainable sites, 4 out of 5 for water efficiency, 13 out of 17 for energy and atmosphere, 7 out of 13 for materials and resources, 14 out of 15 for indoor environmental quality, and 5 out of 5 for innovation and design.
Overall, this particular Chipotle is the first stand-alone restaurant to receive LEED Platinum certification. When designing the Gurnee Mills Chipotle, two main goals were stressed: increasing energy efficiency and to install an onsite renewable energy source. Since Lake Michigan is in close vicinity and the surroundings are fairly windy, Chipotle partnered with Chicago to build a 6 kwh wind turbine, which would be used to power the lighting and other needs in the restaurant.
Also, the project expects to increase water savings by 43 percent and increase outdoor water savings by 100 percent through the installation of a 2,500 gallon cistern to collect rainwater.
Overall, the project estimates that energy savings will decrease by 33 percent, water savings by 43 percent, and 86 percent of construction waste would be diverted from landfills.
Overall, this particular Chipotle is the first stand-alone restaurant to receive LEED Platinum certification. When designing the Gurnee Mills Chipotle, two main goals were stressed: increasing energy efficiency and to install an onsite renewable energy source. Since Lake Michigan is in close vicinity and the surroundings are fairly windy, Chipotle partnered with Chicago to build a 6 kwh wind turbine, which would be used to power the lighting and other needs in the restaurant.
Also, the project expects to increase water savings by 43 percent and increase outdoor water savings by 100 percent through the installation of a 2,500 gallon cistern to collect rainwater.
Overall, the project estimates that energy savings will decrease by 33 percent, water savings by 43 percent, and 86 percent of construction waste would be diverted from landfills.
What is core-and-shell construction?
Core-and-shell construction entails the base building elements, including the structure of the building, the building envelope, and the HVAC system.
What are the categories of LEED profiles?
There are 8 different categories of LEED profiles: new construction, existing buildings, commercial interiors, core-and-shell, school, homes, retail, and neighborhood development.
Brief description of the LEED rating system
The most recent LEED rating system came out in 2009 and contains 9 different LEED rating systems for the design, construction, and operation of buildings, homes and neighborhoods. Of the 9 rating systems, 5 categories are most commonly employed: green building design and construction, green interior design and construction, green building operations and maintenance, green neighborhood development, and green home design and construction.
In general, if buildings are accepted for LEED certification, they are given one of four statuses by the USGBC based on a 1-100 point scale. There is also a 6 point bonus for innovation in design and a 4 point bonus for regional priority. The four statuses are given below, with 1 being the least green to 100 being the most green.
Certified: 40-49 points
Silver: 50-59 points
Gold: 60-79 points
Platinum: 80 points and above
Note: These point ranges apply to most of the profiles, not all. For example, for LEED Retail, the maximum point value is 71.
In general, if buildings are accepted for LEED certification, they are given one of four statuses by the USGBC based on a 1-100 point scale. There is also a 6 point bonus for innovation in design and a 4 point bonus for regional priority. The four statuses are given below, with 1 being the least green to 100 being the most green.
Certified: 40-49 points
Silver: 50-59 points
Gold: 60-79 points
Platinum: 80 points and above
Note: These point ranges apply to most of the profiles, not all. For example, for LEED Retail, the maximum point value is 71.
What are the components of LEED?
The implementation of LEED accreditation is a whole-building approach, aiming on attaining high performance in five crucial areas: sustainable site development, water savings, energy efficiency, materials selection, and indoor environmental quality.
High performance in these five areas work together to lower operating costs and increase asset value, conserve energy and water, reduce greenhouse gas emissions, reduce waste to landfills, and make the living conditions healthier.
What is LEED?
The acronym LEED stands for Leadership in Energy and Environmental Design and the system was set up by the United States Green Building Council in March of 2000. The main goal of the system is to give building owners and operators a basis for developing and integrating green building designs, construction, and operation and maintenance. While the initial costs may be larger in the short-term when compared to non-green solutions, LEED applications make business sense in the long-run. These applications include both commercial and residential estates.
Thursday, September 15, 2011
Can we make a sustainable plan for Hong Kong?
Developing a sustainable plan for Hong Kong is a process that will take many decades to do effectively. The sustainable sources of energy would have to focus around tidal, wave, solar, and wind energy. Ideally, geothermal and hydroelectric power plants make for great sources that are sustainable and economically sound. However, in Hong Kong, these two sources do not possess a future and any chance of prosperity for these industries is unrealistic as discussed earlier. The rivers having don’t have sufficient flow and height; capital costs to create hydroelectric power plants would be a pointless task due to the lack of energy created.
If Hong Kong were to rely on these four sources for their energy they would be in a lot of trouble. Looking back to the green stack we can see that these four categories would provide about 17 kWh per day per person, while the red stack number clearly exceeds the energy provided. For a sustainable plan to be possible, there would have to be restrictions and limits placed on transportation, and heating/cooling for industries and private sectors. The massive amount of energy consumed in Hong Kong can be reduced but not to 17 kWh per day per person. So while it does seem impossible to rely on sustainable resources for 100 percent of the Hong Kong energy, it is very possible to create a sustainable plan for the population. If the people and the businesses keep the topic of conserving energy on their minds then change will happen. It’s tough to say where we will be at ten, twenty, or even a hundred years from now, but a sustainable plan may be the only way to preserve out planet.
If Hong Kong were to rely on these four sources for their energy they would be in a lot of trouble. Looking back to the green stack we can see that these four categories would provide about 17 kWh per day per person, while the red stack number clearly exceeds the energy provided. For a sustainable plan to be possible, there would have to be restrictions and limits placed on transportation, and heating/cooling for industries and private sectors. The massive amount of energy consumed in Hong Kong can be reduced but not to 17 kWh per day per person. So while it does seem impossible to rely on sustainable resources for 100 percent of the Hong Kong energy, it is very possible to create a sustainable plan for the population. If the people and the businesses keep the topic of conserving energy on their minds then change will happen. It’s tough to say where we will be at ten, twenty, or even a hundred years from now, but a sustainable plan may be the only way to preserve out planet.
In terms of energy usage in the USA, where does it go?
Above is the United States Department of Energy treemap of energy consumption data in the U.S as of 2010[33]. This figure is beneficial because you can conceptually see the magnitude of where energy goes within each one of the four main categories: transportation, residential, commercial, and industrial.
Industrial processes make up the most of where energy goes at 32 percent. Manufacturing, chemicals, and feedstocks form the bulk of these processes.
The next highest is transportation at 29 percent, which is expected. Cars and trucks have a great significance in America in meeting our daily needs. Therefore, it is expected that gasoline and diesel make up almost all of the transportation energy usage.
Next, it is interesting to see that the residential sector uses slightly more energy than the commercial sector. Heating, air conditioning, and water heating contain the highest energy among this category. This is why there is a strong emphasis put on making HVAC systems more efficient. If these systems become highly efficient, energy usage in the U.S can drop significantly.
The commercial sector out of the four main categories is the lowest in energy usage at 18 percent. Lighting proves to be the highest energy guzzler from this sector, followed by HVAC.
Can we grow our economies but still decrease energy use?
Economies can definitely grow with decreasing energy usage, but appropriate measures need to be taken. The United States will be concentrated on in this entry; however, the principles apply to the rest of the world.
For one, in the commercial and residential sector, which make up 39 percent of total United States energy consumption, HVAC and lighting are the majority energy functions. Therefore, common sense would say that if the efficiency of HVAC systems and lighting is drastically improved, the total energy usage would decline substantially while economies increase. Making these systems very efficient is possible, but as of now requires a financial compromise. Currently, HVAC systems are more or less designed strictly to function, not worrying about the efficiency because not many businesses are willing to pay extra for higher efficiency systems. It is this financial barrier which will be hard to overcome. In terms of lighting, the switch from incandescent bulbs to florescent could make a substantial difference.
Also, the transportation sector guzzles up 29 percent of America's total energy consumption, predominantly driven by gasoline. As cars that run on batteries gain popularity and get integrated more and more in the general public, the gasoline numbers will drop severely. This would decrease energy usage and grow the renewable energy economy.
For one, in the commercial and residential sector, which make up 39 percent of total United States energy consumption, HVAC and lighting are the majority energy functions. Therefore, common sense would say that if the efficiency of HVAC systems and lighting is drastically improved, the total energy usage would decline substantially while economies increase. Making these systems very efficient is possible, but as of now requires a financial compromise. Currently, HVAC systems are more or less designed strictly to function, not worrying about the efficiency because not many businesses are willing to pay extra for higher efficiency systems. It is this financial barrier which will be hard to overcome. In terms of lighting, the switch from incandescent bulbs to florescent could make a substantial difference.
Also, the transportation sector guzzles up 29 percent of America's total energy consumption, predominantly driven by gasoline. As cars that run on batteries gain popularity and get integrated more and more in the general public, the gasoline numbers will drop severely. This would decrease energy usage and grow the renewable energy economy.
Discuss the GDP per capita versus energy efficiency figure in terms of Hong Kong?
Above is a figure showing the GDP per capita versus energy efficiency for the leading 40 countries in the world according to their GDP.
Based on the figure, it seems as if Hong Kong is in the best position out of all the 40 countries. It's close to being a highly energy efficient region, while also maintaining a highly productive GDP per capita.
It is interesting to note that the bulk of the 40 countries lie in the energy inefficient region. To cut down on total worldwide energy production, this statistic needs to change drastically.
What is the embodied energy in an apple?
When most people go and but an apple from a grocery store they do not appreciate the amount of embodied energy that’s gone into a single apple. Embodied energy is the energy invested into growing, harvesting, transporting, packaging, marketing, and selling the product. For a simple analysis of apples grown in season we will say that most of the energy is used to farm and transport them. The in season apples will need to be shipped but we will assume that the consumer can walk to the local market to get their apples. All the embodied energy comes from driving the apple from the orchard to the local market. We will say that a standard path taken by an apple starts at an orchard, then to storage where they will be graded, then transported to a wholesale market, then transported to the market, and finally picked up by the consumer. From Blanke’s calculations [34] we can estimate that the energy required to produce a local apple is about 2.8 MJ/kg.
Now we need to look at the apples when they are out of season. The Food (miles) for Thought journal [34] looks at the energy balance (or imbalance) for locally-grown apples in Germany vs. imported apples from New Zealand. They found that the imported apples only contained about 27 percent more embodied energy than those that were produced nearby. The comparison made for these German apples is probably very similar to most countries around the world when apples are out of season. The difference they found was 5.89 MJ/kg for local apples and 7.50 MJ/kg for imported apples.
We can now compare these values to a small to average apple that contains 53 calories. We will assume the apple weighs about 3.5 ounces. The energy that we get out of this one apple is only 0.4 MJ/kg.
Now we need to look at the apples when they are out of season. The Food (miles) for Thought journal [34] looks at the energy balance (or imbalance) for locally-grown apples in Germany vs. imported apples from New Zealand. They found that the imported apples only contained about 27 percent more embodied energy than those that were produced nearby. The comparison made for these German apples is probably very similar to most countries around the world when apples are out of season. The difference they found was 5.89 MJ/kg for local apples and 7.50 MJ/kg for imported apples.
We can now compare these values to a small to average apple that contains 53 calories. We will assume the apple weighs about 3.5 ounces. The energy that we get out of this one apple is only 0.4 MJ/kg.
Compare the following sources in a well-organized table: nuclear, wind, solar, natural gas, coal, petroleum, bifuels
Below is a link to our table:
Sources:
What is the carbon footprint and embodied energy?
A carbon footprint encompasses the total amount of Greenhouse Gas emissions generated by an event, product, person, or from electricity production. Out of all the electricity sources, wind, hydroelectric, and nuclear have proven to contain the lowest carbon footprint. That is, throughout the whole life cycle from construction to operation, these energy sources give out the lowest concentration of greenhouse gases [35].
In terms of our country under study, Hong Kong contains the second highest carbon footprint per capita in the world at 29 tonnes per year. This is mainly due to the large-scale importing of energy, manufacturing, and transportation of imported goods [36].
Embodied energy consists of summing the total energy inputs throughout the whole life cycle of a product. Components of the life cycle included that are summed are as follows: extraction, transport, manufacture, assembly, installation, disassembling, deconstruction, and/or decomposition [37].
What is energy density?
Energy density is the amount of energy stored within a fuel. The energy density also helps us to realize how much waste will be produced per unit of energy extracted. Nuclear fission reactions are those that harness the potential energy of a nucleus, which contains nearly all of the energy of an atom. The element uranium is particularly useful is nuclear fission. The isotopes U-235 and U-238 are used most often to extract nearly all of the energy from an atom. The waste energy from nuclear reactions isn’t released to our atmosphere like most energy conversion processes. Instead, all of the waste can be stored and kept underground where is won’t have any negative effects on our environment.
When looking at other more common energy sources we can place propane near the top for high energy density. The next highest energy density can be found in gasoline, followed by diesel fuel, biodiesel, and then coal. Coal still has a higher energy density than a 100-ft-high dam with water spilling over by about 30,000 times.
When looking at other more common energy sources we can place propane near the top for high energy density. The next highest energy density can be found in gasoline, followed by diesel fuel, biodiesel, and then coal. Coal still has a higher energy density than a 100-ft-high dam with water spilling over by about 30,000 times.
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