Science Man and His Environment/Energy

Energy Usage
Energy usage varies widely among different countries

Units of energy resources usually given in tons of oil equivalent (toe):
 * one toe is amount of energy in one metric ton of oil

The table below gives the total energy consumption per capita per annum (2003) [kgoe/a] for selected countries (the whole list can be found here) Bangladesh		160.9 Eritrea		199.3 Senegal		233.2 Nepal			335.9 Morocco		357.3 Cote d'Ivoire		378.8 India			512.4 Kyrgyzstan		520.5 Honduras		521.9 Vietnam		539.4 Indonesia		757.4 Egypt			761.3 Nigeria		776.9 China			1138.3 Gabon			1248.7 Macedonia		1313.9 Thailand		1405.7 South Africa		2596.9 Lithuania		2629.2 Belarus		2630.9 United Kingdom		3918.1 Japan			4040.4 Austria		4053.2 Germany		4203.1 South Korea		4346.5 New Zealand		4378.6 Russian Federation 	4423.2 United States		7794.8 Canada			8300.7 Trinidad and Tobago 	8555.1 United Arab Emirates 	10538.7 Iceland		11718.1 Qatar			21395.8

Energy usage is usually divided into four sectors:
 * Industrial
 * Residential
 * Commercial
 * Transportation

Examples of energy usage by sector (in percent):



!Sector !USA !Thailand
 * Industrial
 * 33.3
 * 36.4
 * Residential
 * 16.0
 * 15.4
 * Commericial
 * 11.9
 * 7.8
 * Transportation
 * 38.8
 * 35.2
 * Agricultural
 * 5.2
 * }
 * 35.2
 * Agricultural
 * 5.2
 * }
 * 5.2
 * }


 * *The USA (and most other countries) include agriculture under commericial

Energy can be shown by using an energy flow chart 



The above figure shows the flow of energy in the United States. The left is the different energy sources, while the white shows the four sectors. Note that about 40 % of the energy is used to make electricity. Also note the Rejected Energy (in gray). It is 58% of all energy (more than half). This is partly due to the second law of thermodynamics and partly due to use of inefficient equipment.

Since a large part of energy is used for electricity generation, let us look at how the majority of electricity is made.



Water is heated in the boiler to create steam. The boiler can be heated by coal, oil, natural gas, nuclear, thermal solar, biomass, or geothermal. The steam is then used to drive a turbine. The turbine consists of blade attached to a shaft. The shaft is connected to a dynamo to generate electricity. The steam leaving the turbine is then condensed back to water (releasing heat) and then pumped back to the boiler.



A small percentage of electricity is produced by direct energy conversion - photovoltaic solar, wind, or hydropower.

Energy Sources
Types:
 * renewable
 * nonrenewable


 * Nonrenewable energy sources : Energy sources which are used much faster than they are produced

Energy sources which are produced rapidly or continuously
 * Renewable energy sources :



Nonrenewable energy sources

 * Energy reserves : known deposits which can be extracted economically



Fossil Fuels
Fossils fuels are created when dead organic matter is subject to high temperatures and pressure over millions of years. Fossil fuels include oil, coal, and natural gas.

Oil
Uses: electricity, transportation, heating, petrochemicals, plastics

Environmental Issues: oil spills, disruption of wildlife (due to oil drilling), greenhouse gases, air pollution, energy security, limited supply



Natural gas
Natural gas is often found with oil

Uses: electricity, heating, petrochemicals, plastics

It burns clearer than oil and has a much greater amount of reserves. It has been proposed as a transitional fuel (see Web Resources below).



Some commonly used acronyms
 * LNG - liquefied natural gas
 * LPG - liquefied petroleum gas
 * CNG - compressed natural gas
 * NGV - natural gas vehicle

Coal
Uses: electricity, heating

Issues: land disturbance, acid mine drainage, acid rain, greenhouse gases, air pollution



Nuclear Energy
Nuclear energy is using nuclear fission to produce heat (instead of coal, etc.).

The fuel used is uranium-235. A nuclear reaction occurs which produces high amounts of energy. This reaction is self-sustaining.

Note that mined uranium must be processed to be used as fuel since only 0.7% is U-235 (99.3% is U-238 which is non-fissionable). For use as a fuel uranium needs to at least 3 to 5 % U-235.





Advantages

Lower (but not zero) greenhouse gases

Adequate fuel supply

Disadvantages

Safety - with high radiation the potential for a severe accident is always present.

Nuclear waste - The waste fuel is extremely radioactive and long-lived.

Nuclear proliferation - There is concern that fissionable uranium or plutonium good get into the hands of terrorists and criminals.

High cost

Low efficiency - 25% vs. 30% for fossil fuels.

Solar Energy
Solar energy refers to using the energy directly from the sun

There are four types of solar energy


 * Passive solar : Uses solar energy directly to heat a space




 * Active solar : Solar energy to heat a fluid which is then used to heat water or a space




 * Thermal solar : Using solar energy as the heat source in a power plant




 * Photovoltaic cells : These convert solar energy directly into electricity using electronics



Wind Energy
Converting the wind into electricity using turbines



Pros: extremely efficient

Cons: requires land space, can be a hazard to birds.

Because of the land issue, recent interest has been in offshore wind farms.



Hydroelectric Power (Hydropower)
Using the power of flowing water to drive a turbine

Most hydropower is large scale - using a large dam to create a reservoir

Small-scale hydropower is using a small dam (or no dam) with no reservoir







Issues: large dams can be very destructive to the environment (see Web Resources below)

Small-scale hydropower usually has a small impact



Large dams also create social problems



Biomass
Biomass is the use of plant and animal material as an energy source

Types: 
 * Direct burning for heating and cooking (by far the largest usage, mostly wood used for cooking and heating)
 * Burning to produce heat for electrical generation
 * Biogas - Production of methane from waste products
 * Biofuels - Making liquid fuels as replacement for gasoline and diesel fuel

Biofuels
Biofuels are controversial. To understand that we need to know the difference between first and second generation biofuels.


 * First generation biofuels : Crops grown specifically for biofuel production


 * Second generation biofuels : Waste products are used to produce the biofuels

The controversy deals with first generation biofuels only.

Issues with biofuels

A major problem with first generation biofuels is that the planting of crops either reduces the amount of land available for food crops or is cleared from native forests

Geothermal energy
This is using the heat trapped underground either for direct heating or as a heat source for electrical generation

It is the same mechanism as found in hot springs





Tidal power
This uses the difference in tides to generate energy

A major restriction on its use is there are very few places with a large enough tides





Definition
Energy conservation is reducing the amount of energy used by improving energy efficiency

Energy conservation is the most important part of sustainable energy

Energy Efficiency
It is largely dependent on the specific energy usage or process. Some methods include replacement of inefficient equipment with more efficient ones, changing energy source, and changing processes.

Cogeneration
Cogeneration is the production of both energy and heat simultaneously. A cogeneration facility produces energy in the traditional way, but then uses the exhausted heat in order to heat buildings, make steam, provide energy to a process.

Transportation
Transportation takes up a large amount of the energy budget. Reducing reliance on gasoline and diesel fuel reduces not only energy consumption but also reduces greenhouse gases and air pollution.

Some conservation measures include:
 * Using electric and hybrid vehicles
 * Hybrid vehicles have both an internal combustion engine and an electric motor.
 * Making cities more bicycle friendly

Demand-side management
The size and number of power plants needed is determined by the peak electricity demand, not the average demand. Reducing this peak load is called demand-side management.

Examples:
 * Education - especially through using energy ratings on appliances, etc.
 * Adding devices which reduce air-conditioning usage during peak demand periods
 * Giving financial incentives to users in order to encourage shifting of electrical use to off-peak hours.

Energy audits
An energy audit is a survey of the energy usage within a building (or elsewhere). It looks at every point where either energy is used (for example, appliances) and where energy is lost (for example, leaking windows). Usually a checklist is used.

An example checklist can be found HERE

Conclusion
As it corresponds to energy and especially energy conservation this quote sums up the problem:

Technology is the Answer, but what was the Question?
 * Amory Lovins