Wind and Other Renewable Energy Sources

Physics 1303

Renewable Energy comes in many forms:

Wind EnergyHydroelectricGeothermalBiomassOcean Thermal

Wind Energy

Uses the kinetic energy of wind. Needs high wind speed. Maximum efficiency is 59%. Practical efficiency is nearly 50%.

Wind Resource Map of the US

Desert Sky

Wind project Iraan, TexasOwner: American Electric PowerCustomer: CPSManufacturer: GE Wind Energy (formerly Enron)

Desert Sky

1.5 MW/Turbine 107 TurbinesMin. Wind: 8 mphMax. Wind: 56 mph

Desert Sky

Financing Depends on State Renewable Tax Incentive Program.AEI must guarantee to operate the system for 30 years

Desert Sky

ERCOT (Energy Reliability Council of Texas) maintains the electric grid for most of the state.AEI is not allowed to generate more than 100 MW

Desert Sky

Wind has some impact on the site as shown in the photo.Source of income for ranchers.

Wind Calculation

Stop and do the wind problem.

Wind ProblemThe Desert Sky Project near Fort Stockton, Texas has 107 wind turbines spread over 15 square miles on Indian Mesa. Each Turbine has a maximum capacity of 1.5 MW of power.

1.    Calculate the total power

capacity of this wind farm.

Capacity =

= 107 turbines • 1.5 MW / turbine = 161 MW

2. The capital cost of this project is about $175 million. Calculate the capital cost for each watt of installed

capacity..

Cost per Watt =

= $175 million / 161 MW= $1 / watt

3.  Assuming the project runs on average at 50% of capacity, calculate the total energy produced in a year. Express your answer in kWh. .

Annual Energy Production =

= 0.50 • 161 MW • 24 h/day • 365 day/year = 700 Million kWh / year

4. Assuming the commercial value of this electricity is $0.03/kWh, calculate the value of the energy produced in a year.

Value =

= 700 million kWh • $0.03 / kWh= $21 million / year

5. Neglecting the cost of running and maintaining this system, estimate the payback period for this investment.

Payback = Cost / Savings = $175 million / $21 million /year = 8 years

Hydroelectric power

Energy is stored as gravitational potential energy.Electrical generators convert mechanical energy to electrical energy.

Hydroelectric power

Largest source of renewable energy in USFill with siltLoss of wild riversCatastrophic floodingSalmon breeding blocked

Geothermal Energy

Localized surface level hot spots. Geothermal energy may be exploited for local uses.Not an important global resource.

Geothermal Energy

An important resource for Costa Rica and some other countries. Not really renewable.

Biomass EnergyPlant material is burned directly or converted into a fuel. An example: Conversion of grain to ethanol and the production of gasohol (10% ethanol and 90% gasoline)

Biomass EnergyRenewable Recycles CO2Could use agricultural wasteCompetes for agricultural landLow efficiency

Ocean Thermal Energy Conversion

OTEC uses the temperature differences between the ocean surface and ocean depths to run a heat engine. Highest potential in deep tropical waters like the Gulf of Mexico.

OTEC

Second Law of Thermodynamics: Max eff. = (Thigh - Tlow )/ Tlow

So, efficiency is pretty low.

Wind and Renewable Energy Technologies

Do these technologies represent the dawning of a new age of sustainable development?