As you can probably tell from my other posts on this site I advocate utilizing as many sources of energy as possible, but I also try to be realistic and consider environmental and economic factors.
So what does it mean to be green?
– Potential Cumulative Energy Production
Part 2 and 3?
– Land Usage
– Some Thoughts on EROEI (energy returned on energy invested)
In the best case around 260 kWh/ sq ft per year reaches the surface of the earth. (New Mexico)
A large portion of the United States is closer to 211 kWh/ sq ft per year.
The most efficient solar cell that can be purchased in today’s market is about 29% but an average solar cell would convert about 13% the total solar energy it receives to usable power.
Best case .29*260 = 75.4 kWh/ sq ft per year.
What I will call average .13*211 = 27.4 kWh/ sq ft per year. (average based on land not population distribution)
An average US home uses 8,900 kilowatt-hours of electricity each year. (Probably a little high)
Good: 8,900 kWh/y year / 75.4kWh/y = 118.1 sq ft
Average: 8,900 kWh/y year / 27.4kWh/y = 324.8 sq ft
Price per square foot for solar panels ranges between 100 and 300 sq ft installed so $150 seems possible.
Good: $150 * 118.1 sq ft = $17,715
Average: $150 * 324.8 sq ft= $48,720
Most commercial wind turbines range between 2 and 3 MW, and in 2007 it cost $1.2 million to $2.6 million, per MW of nameplate capacity installed.
We still need to factor in efficiency which on commercial systems can range between 20% and 45% (In ND).
Best Case 3000kWh*.45 = 1350kWh ~3.6 million
Average 3000kWh*.25 = 750kWh ~$4.5 million
Good: Annual power production 1350kWh*24*365 = 11826000 kWh/year
Average: Annual power production 750kWh*24*365 = 6570000 kWh/year
30 year lifespan * 11826000 kWh/year = 354,780,000 kWh/ 30 years
30 year lifespan * 6570000 kWh/year = 197,100,000 kWh/ 30 years
There really is no such thing as average when it comes to the cumulative production of an oil well, but most modern oil well in the US will yield somewhere between 200,000 and 2.5 million barrels of oil over their life time. (30-50 years in many cases.) It is also important to note that the payback is front loaded meaning production is very high when a well is brought online and declines over the life of the well. What that really means is that the pay back period is relatively fast.
Barrel of oil equivalent (boe) = approx. 6.1 GJ (5.8 million Btu), equivalent to 1,700 kWh. “Petroleum barrel” is a liquid measure equal to 42 U.S. gallons (35 Imperial gallons or 159 liters); about 7.2 barrels oil are equivalent to one tonne of oil (metric) = 42-45 GJ.
Good well 1700kWh * 2,000,000 barrels = 3,400,000,000 kWh
Bad well 1700kWh * 200,000 barrels = 340,000,000 kWh
The previous calculation got me accused of trying to skew the results, but realistically it is difficult to find efficiency values for how much energy is actually usable from a barrel of oil. The reason I originaly did not factor efficiency on oil is because the energy does exist and is stored in a barrel of oil even if it is not properly used. Efficiency was factored into solar and wind energy because energy is not tangible if it is not created and therefor it is necessary to factor it in.
With the last statement said we all know that energy from oil is used poorly in most cases so it is safe to assume efficiency factors that range between 20 and 60%.
.6 * 3,400,000,000 kWh = 2,040,000,000 kWh
.6 * 340,000,000 kWh = 20,400,000 kWh
.2 * 3,400,000,000 kWh = 680,000,000 kWh
.2 * 340,000,000 kWh = 68,000,000 kWh
Just to make sure solar cells don’t feel left out we will say that oil wells and wind towers have about a one acre footprint 43560 sq ft (more like .25 acre) . Which will cost you… $100(bulk rate) * 43560*= $4,356,000. So now our cost for each energy source is between 4 and 5 million US dollars. This is how it shakes out.
Average: 43560 sq ft* 27.4kWh/y *30 years = 35,806,320 kWh/ 30 years
Good: 43560 sq ft* 75.4kWh/y *30 years = 98,532,720 kWh/ 30 years
The most important detail that is not depicted in this chart is that the payback time for petroleum based power sources is rapid because petroleum production is typically high soon after a well is brought online. Over time petroleum production declines, but the company has already made all of the input cost back and moved on to drill more wells. Solar and wind return energy consistently but slowly which makes it difficult to rapidly grow. Growth in wind production has to be based on some forum of credit and long term planning which isn’t something that makes share holders happy (the same is somewhat true for tax subsidies too). The input cost and energy requirements that go into producing oil is very high and the efficiency is low, but none of that seems to matter as long as the payback period is short.
Energy Conversions: http://bioenergy.ornl.gov/papers/misc/energy_conv.html
Solar and Wind estimates: http://www.npr.org/templates/story/story.php?storyId=110997398
Solar Efficiency: http://sroeco.com/solar/most-efficient-solar-panels
Wind power pricing and rating: http://www.windustry.org/how-much-do-wind-turbines-cost