Home energy

For a 1000 square foot home with 8 foot ceiling, we assumed the wall was made of bevel wood siding, polywood sheething, 3 1/2" fiberglass batt, 3 1/2" wood studs, 1/2" drywall, and 15% stud contribution to 85% cavity contribution. We also assumed that there were 14  air exchanges per hour. Using these assumptions, the values we got for a home in Boulder, CO are:

Rsiding=.8;

Routerins=.63;

Rinnerins=13;

Rstud=4.38;

Rdrywall=.45;

Riair=.68;

Roair=.17;
Rshingles=.44;
Rattic=3.1

Rwall = 13.3

Rceiling = 16.8

UA = 2.78

ma = 1498 lb/hr
cpa = 0.24 BTU/(lb °F)

JAN	FEB	MAR	APR	MAY	JUN
34.54	35.87	42.51	48.63	57.59	65.98
JUL	AUG	SEP	OCT	NOV	DEC
73.54	70.89	62.88	51.34	41.78	34.08

Heating degree days:5320

Cooling degreedays:476

Qh = 1,927,000 BTU/year

Qc = 172,700 BTU/year

LEED Quality Homes

LEED is the Leadership in Energy and Environmental Design, a green building certification system that is internationally recognized. LEED provides ways to identify and implement measurable and practical ways for people to design, build, operate, and maintain green buildings.

LEED has multiple rating systems for projects, which is based on an open, consensus based process. They type of rating system used is depends on the type of construction being done. Volunteers from the building and construction industry make up a committee which leads the process. Some of the things LEED ratings are based on include water efficiency, energy efficiency, location sustainability, what materials and resources are used, and awareness or usage of the buildings green capabilities.

Some of the different categories or profiles that LEED provides to chose from are new construction, existing buildings, commercial interiors, core and shell, schools, homes, retail, and neighborhood development. If a project seems appropriate for more than one category, they have a 40/60 rule to determine which category to use. To determine which is more appropriate, LEED recommends assigning every square foot to one of the categories, and then using the resulting percentages to determine which is most appropriate. If a catergory has 60% or more, then that is the recommended category. If the categories are between 40% and 60%, it is up to the projects lead designer which category to use.

One of the profiles is a core-and-shell project, which could be a bit ambiguous. Generally, a core-and-shell project consists of base building elements, such as the structure, envelope and building-level systems, such as central HVAC, etc.


One example of a LEED-certified project is the Medium Tactical Equipment Maintenance Facility at the Joint Base Lewis-McChord, W.A. The facility is labeled as a new construction profile, and has a Gold rating of 45/60 points. The individual ratings are 10/14 for site sustainability, 5/5 for water efficiency, 11/17 for energy and atmosphere, 5/13 for materials and resources, 10/15 for indoor environment quality, and 4/5 for innovation and design. Since 2006, all military buildings must achieve at least a silver rating from LEED in an effort to reduce excess water and energy usage and waste production. 

Hong Kong End Uses

Comparison Summary

Wind power essentially has no cost for fuel, but has a high cost of production per kWh it can produce as well as a low energy capacity. It is also limited to the main areas of the wind stream for fully effective use. Wind farms also require a large amount of land dedication, whether they are on land or offshore turbines. Wind power has essentially no waste production, greenhouse or otherwise.

Natural gas has the second highest cost of production per kWh, with solar being the most expensive. It has a cost of energy production comparable to petroleum. Natural gas would use about the same amount of land as coal or nuclear, as it would need a standard power plant to burn the gas. Natural gas also has waste gas production, although it is much lower than coal or petroleum.

Coal is currently the largest producer of energy, because it is cheap and has a decent energy density. However, the impact it is having on the environment is cause for concern. Greenhouse gases as well as the effect of mining make it necessary to be phased out of use. Coal is a fossil fuel, meaning there is finite amount of fuel reserves, which are predicted to be depleted in less than 100 years. 

Petroleum has production cost similar to coal, and has the same problem of greenhouse gas emissions, although to a lesser degree. It also has a relatively high energy density compared to other forms of energy production. Petroleum uses power plants, so the land use is the same as coal as well. It is also a fossil fuel like coal, so there is a finite amount of fuel reserves. 

Nuclear power has very many advantages to it. It’s cost of electricity production is on par with the cost from coal, which is considered one of the cheapest methods of production. Nuclear has by far the best energy density and capacity factor compared to the other methods of energy production, nearly two million times more than that of coal! It has a very low to no greenhouse gas emission, but the toxic waste it produces still does not have a great means of disposal. 

Biofuels use waste from other products, so it has a much cheaper cost of fuel. It also means that there is not a finite limit to how much fuel is available. It uses power plants like many others, so the land use is comparable to current coal power plant land use. Biofuels have a lower energy density than other methods as well. There is very little waste produced compared to burning coal or petroleum.

Solar has no fuel cost either, but has a huge production cost per kWh. It is still a very inefficient power source as well, with the best converters at about 20% efficiency. The solar panels are still very expensive to produce as well as maintain, which is the largest obstacle preventing more solar energy production. Because there is no fuel being used, solar energy is extremely clean. Depending on implementation, solar power can have a large or small land area usage. If made into PV farms, they would use a lot of land area. However, if they are installed in places such as rooftops, house sidings, etc. they would use very little land area. Another problem with solar is the unpredictability of sources, as the solar radiation depends on time of year, cloud cover, time of day, etc. 

CO2 Due To Biomass Reduction

The reduction in biomass( deforestation) has a definite effect on the overall CO2 levels in the atmosphere. Trees and other biomass act as a CO2 sink and absorb the atmospheric CO2. However, in terms of the overall CO2 levels in the atmosphere   the biggest cause is humans burning fossil fuels. “deforestation and forest degradation emissions contribute about 12% of total anthropogenic CO2 emissions”

http://www.biology.duke.edu/jackson/ng09.pdf

Energy in An Apple

The amount of energy that is inherent in an apple truly depends on where it is grown. The transportation and storage of an apple out of season is nearly 3 times as much energy than it is to grow it. We assumed the average weight of an apple is 0.5 pounds. We also assumed that in season you can get an apple grown and transported around 100km away. First, the amount of energy to grow an apple was found. This was found to be approximately 0.5 kWh. Then using data already calculated, we assumed it is 0.8kWh/ton-km to transport an apple. Using these numbers, an apple grown within 100km has 0.54 kWh of inherent energy, while an apple that is out of season, and has to be shipped in uses 1.7kWh. This may not seem like very much but if you increase the amount of apples from one to several million, the number can become rather frightening.



http://userwww.sfsu.edu/~cholette/sustain/SSCpublic/Local_vs._Imported_Apples-case3.pdf

Final Green Stack vs. Red Stack

Green Stack: Geothermal

Unfortunately for Hong Kong, geothermal energy is another unfeasible source of renewable energy. Due to geological constraints and such a dense population, geothermal energy is a renewable source that would not work in Hong Kong. Assuming hot dry rock resource was similar to the UK as presented in McKay's book, "Sustainable Energy Without The Hot Air", The UK has a population of only about 43 people per km^2, while Hong Kong has about 6250 people per km^2. The UK presented only 0.13 kWh/day per person with a much less dense population, revealing little hope for Hong Kong. In addition when conducting research, every site stated that geothermal energy is not plausible for Hong Kong.

Green Stack: Wind

Unknown to many, wind is actually a form of solar energy. Wind is caused by not only the varying contours of the Earth but also from the infared radiation given off by the Sun and Earth. Air in different locations across the Earth are heated differently due to these factors. This leads to areas of colder and thus more dense air pockets, as well as less dense and warmer areas. The air flows from areas of higher pressure to low pressure, and is directed differently due to the  varying pressures as well as other factors mentioned. This wind can be harvested into energy through the use of wind turbines. The kinetic energy in the wind is converted into electricity as the wind turns the blades of a turbine, powering an electric generator. This power is considered a renewable energy source because wind is an infinite power source (it will never run out). As with all energy sources however, it has its drawbacks. One such drawback is that they are often best placed in remote locations away from cities and other areas with high energy demand. Another disadvantage is the initial investments to create a wind turbine farm are considerably expensive compared to other energy sources.

To estimate the amount of kWh/day of energy could be created using wind turbines in Hong Kong, the power per Unit Area of Land first needs to be calculated using the equation (pi/400)*pv^3. With an average temperature of 23 degrees C in Hong Kong, the air density is about 1.2 kg*m^-3. The average wind velocity is 3.32 m/s. Inserting these values into the above equation reveals a Power per Unit of Land of 0.34 W/m^2. The average wind speeds in Hong Kong varies from 0.15 to 6.49 m/s.The Area per person in Hong Kong calculates out to be: 1104 km^2 / 6.9 million people = 160 m^2 per person. The power per person then is 0.34 W/m^2 * 160 m^2 = 54.4 W per person. Multiplying this by 24 hours per day gives 1.3056 kWh/person. Assuming 15% of the land could be used for wind turbines, a total of 0.2 kWh/day of available energy from wind turbines.

Green Stack: Hydroelectricity

 In order to be able to generate hydroelectic power, two main features are required for a country: elevation above sea level and rainfall.
With a population of approximately 6.9 million people, Hong Kong's potential Hydroelectric power capabilities come out to be too insignificant to even consider, being about 0 kWh/day. This number is derived by taking into consideration the average rainfall in Hong Kong of 2382.7 mm per year. This along with the density of water (1000kg/m^3),  and the strength of gravity being 9.81 m/s. The average altitude above sea level across Hong Kong is only 33 m. With such a large population, and such a small elevation, Hydroelectric power becomes an unfeasible solution.

Wave Energy

Using similar figures as McKay, we found meters of shoreline along with the average amount of energy a wave has per meter of height. We then estimated that only about 25% of the waves actual energy would be able to be harvested. This is due to loses in the turbines as well a an inability to catch an entire wave.

Energy Consumption: Stuff and transporting stuff

In order to find the energy consumption per person per day in kWh, in terms of "Stuff" all items had to be considered. Things that seem not to fit in other categories go into the "Stuff" category. We decided on a few of the items that would use more energy and that are in nearly every household. With that in mind we decided to account for miles of road, computers, cars, cluminum usage, and plastic bottles. For transporting stuff, we found the average amount of energy consumed per ton of cargo according to McKay. Then we simply found out the amount of stuff was is being transported into and out of Hong Kong.