1. Renewable Energy Systems
ME 252
Thermal-Fluid Systems
G. Kallio

2. Renewable Energy Systems
Introduction
Renewable energy is energy obtained from sources that are essentially inexhaustible, as opposed to energy obtained from fossil fuels (coal, petroleum, natural gas), of which there is a finite supply.
Renewable energy technologies generally include:
Solar electric, or photovoltaic (PV)
Solar thermal
Wind turbines
Geothermal
Biomass
Fuel cells that use renewable hydrogen
Small hydroelectric
Ocean energy
11/15/2018
Renewable Energy Systems

3. U.S. Energy Consumption by Resource
Electrical Power (%)
Total Energy (%)
Petroleum 2 40
Natural Gas 10 25
Coal 55 23
Nuclear 22
7.7
Hydro
3.9
Geothermal
0.2
0.1
Wind
Other
0.6
1997 data (Wiser, 2000)
11/15/2018
Renewable Energy Systems

4. U.S. Fossil Fuel Reserves vs. Energy Consumption
1997 data (Wiser, 2000)
Fossil Fuel Resource
Reserve (%)
Consump-tion (%)
Coal 82 23
Natural Gas
1.4 25
Petroleum
1.3 40
Oil Shale 14
Tar Sands
11/15/2018
Renewable Energy Systems

5. Fossil Fuel - Petroleum
Total world reserves (known & recoverable): 1035 billion barrels
Total world demand: 25.7 billion barrels/year
Years to depletion: /25.7 = 40 years
1997 data (Wiser, 2000)
11/15/2018
Renewable Energy Systems

6. Renewable Energy Systems
U.S. Petroleum Use
Transportation: 60%
Industrial processes: 19%
Heating oil: 6%
Synthetics/Plastics: 5%
Petrochemicals: 5%
Electric Power: 5%
1997 data (Wiser, 2000)
11/15/2018
Renewable Energy Systems

7. Fossil Fuel – Natural Gas
Total U.S. reserves (known & recoverable, including coal bed methane): 361 trillion ft3
Total U.S. demand: 22.3 trillion ft3/year
Years to depletion w/o imports: /22.3 = 16 years
1997 data (Wiser, 2000)
11/15/2018
Renewable Energy Systems

8. Renewable Energy Systems
Fossil Fuel - Coal
Total U.S. reserves (known & recoverable): 434 billion tons
Total U.S. demand: 978 million tons/year
Years to depletion w/o imports: /0.978 = 444 years
1997 data (Wiser, 2000)
11/15/2018
Renewable Energy Systems

9. Renewable Energy – Solar Systems
Solar Electric, or Photovoltaic (PV), Systems
Solar Thermal Systems
Concentrating solar for power generation
Passive solar for space heating/cooling and daylighting
Active solar water heating and space heating/cooling
11/15/2018
Renewable Energy Systems

10. Renewable Energy – Wind Turbine Systems
Horizontal Axis Wind Turbines
Vertical Axis Wind Turbines
11/15/2018
Renewable Energy Systems

11. Renewable Energy – Geothermal Systems
Space Heating - direct use of hot water
Electrical Power Generation – steam power plant
Ground-Source Heat Pumps – utilizes constant temperature of soil or surface water
11/15/2018
Renewable Energy Systems

12. Renewable Energy – Biomass Systems
“Biomass” refers to any plant-derived organic matter
Biomass solid fuels include wood waste, ag waste, animal waste, municipal waste, and aquatic plants
Biomass liquid and gaseous fuels include ethanol, methanol, biodiesel, methane, and hydrogen
Combustion of biomass fuels is used in electric power generation, process heating, and vehicle propulsion
11/15/2018
Renewable Energy Systems

13. Renewable Energy – Hydrogen Fuel Cell Systems
Renewable sources of hydrogen include water (by electrolysis) and reforming biomass fuels
Fuel cells efficiently convert chemical energy into electricity with little or no pollutant emissions and without the limitation of the 2nd Law of Thermodynamics
11/15/2018
Renewable Energy Systems

14. Renewable Energy – Hydroelectric Systems
Renewable hydroelectric typically refers to small plants (< 30MW) due to their minimal impact on fisheries and downstream water quality
Not all hydroelectric systems require dams; a diversion facility channels a portion of the river through a canal or penstock
11/15/2018
Renewable Energy Systems

15. Renewable Energy – Ocean Energy Systems
Tidal Energy – uses traditional hydroelectric technology to produce electricity from an elevated, dammed tidal basin
Wave Energy – difficult to harness
Ocean Thermal Energy Conversion (OTEC) – natural-occurring temperature difference used as a heat engine
11/15/2018
Renewable Energy Systems