Energy Production

1. Energy Production

2. Points on Energy to Discuss • Why is important in Agricultural Production? • Is all energy alike? • Can substitutions be made? • What about scalability?

3. Energy • Primary energy sources (data from 2005) • 40% Petroleum • 23% Coal • 23% Natural Gas • 8.4% Nuclear • 5.6% Renewable (mostly Hydroelectric) • Large scale production in the megawatts • Must then be distributed

4. Power Production • Power plants use generators to transfer mechanical motion to electrical power • Generators operate in the opposite capacity of an electric motor • The US grid is based on Alternating Current (AC) • 60 Hz (frequency or oscillations per second) • Must all be in phase • Multiple plants on the same grid • Syncing – up/tying to the grid

5. Power Production

6. Power Production

7. Power Production • Plants size • Measured in MW • Total peak output capacity • Large scale productions • Greater than 1 MW • Distribution • Power cables to substations • Power lines from substations to transformers • 120 Vac from transformer to houshold outlet • Power losses • Resistance in wire • Transformer junctions

8. Power Production • Due to large losses and large distribution areas plants must produce much more energy then eventually reaches the consumer • A fossil fuel plant is at best 40% efficient • So less than half even makes it to the generator • Power line efficiencies are also in the 40% range • So less than half of what makes it to the generator leaves the plant • Through other components more is lost resulting in what the consumer uses

9. Energy Sources • Grid Power Sources • Coal, Nuclear, Natural Gas, Wind, Hydroelectric, Hydrogen, and Biomass • Onsite Sources • Solar, Wind, Hydroelectric, Geothermal, and Biomass

10. Energy Sources • Grid Power Sources • Coal • Nuclear • Natural Gas • Wind • Hydroelectric • Hydrogen • Biomass • Onsite Sources • Solar, Wind, Hydroelectric, Geothermal, and Biomass

11. Grid Scale Energy Sources: Fossil Fuels Fossil Fuels - Coal, Natural Gas, Petroleum • Large amounts of stored energy • Nonrenewable, and must be mined • Fuel must be transported from mines to power plants • Large amounts of CO2 , Mercury, and Radon released • 100 x more radioactive material released to the environment than from nuclear power plants • Cost is low!

12. Grid Scale Energy Sources: Fossil Fuels • Fossil Fuels are burned and boil water • Advanced water reheat systems heat the water above the critical point creating superheated water • Combined with a multiple pass turbine large amounts of energy can be extracted from the steam • The hotter the water gets the more energy that can be distracted • Higher energy fuels can boil water to higher temperatures

13. Grid Scale Energy Sources: Coal Coal Power Example • Energy density: 6.67 kWh/kg (27000 BTU/kg) • Power plant efficiency: 30% 100 Watts x 24 h/day x 365 days/yr = 876 kWh/yr 876 kWh/yr / (6.67 kWh/kg x .30) = 437.78 kg/yr

14. Grid Scale Energy Sources:Nuclear Nuclear Fuels • Large amounts of energy in a small package • Fuel is Uranium-235 • 1 ton of U235 is equivalent to 500 tons of Coal • Fission Reactors • Boiling Water Reactors (BWR) • Pressurized Water Reactors (PWR) • Radioactive waste byproduct • Same principles of boiling water to spin turbines • Highly regulated

15. Grid Scale Energy Sources:Hydroelectric • Hydroelectric power has been used in agriculture for centuries • Water wheels to power mills, and factories • Modern dams stop river flows until it forms a lake of considerable depth • At the base of the dam are turbines that spin when the dam is opened • Energy is a function of: • Lake depth • Turbine area • Entrance and Exit pipe sizes

16. Grid Scale Energy Sources:Hydroelectric • Power available by hydroelectric dam P = ρ*h*r*g*k ρ - density of water h - height of water in the resevoir r - flow rate of the water (dependant on inlet pipe size) g - gravitational constant k - turbine efficiency

17. Grid Scale Energy Sources:Hydroelectric

18. Grid Scale Energy Sources:Hydroelectric

19. Energy Sources • From the Grid Scale the cost of the fuel is not as significant as the cost of the infrastructure • Cost effective energy strategies in agricultural production are somewhat different • Onsite power production • Viable with emerging technology • Viable in rural areas with little to no grid support • Often cost effective to run nonessential equipment

20. Energy Sources • Grid Power Sources • Coal, Nuclear, Natural Gas, Wind, Hydroelectric, Hydrogen, and Biomass • Onsite Sources • Solar • Wind • Hydroelectric • Geothermal • Biomass

21. Onsite Energy Sources • Power • Produced without a generator • Often delivers power as a Direct Current (DC) • Requires batteries for storage • Low efficiencies (but improving significantly) • Thermal • Using natural temperature gradients • Subsurface • Sunlight • Old and proven technology • Efficient and cost effective

22. Onsite Energy Sources: Solar • New technological innovations in production • Reduced cost • Greater availability • Renewable • Reliability • Sunshine is predictable • Distance from equator matters • Vegetation and weather patterns can play with efficiency • Two Sectors • Photovoltaic • Solar Thermal

23. How Solar Cells Work

24. Onsite Energy: Solar Availability

25. Onsite Energy Sources: Solar

26. Onsite Energy: Solar Availability • Florida is between 5000 and 5500 Watt hours per meter squared per day • Full terrestrial sunlight is about 1000 W/square meter (340 BTU/ft2h) per day • Full sun equivalent of between 5 and 5.5 hours per day • Panel Efficiency • PV ~ 6 - 10% • Thermal ~ 40 – 60%

27. Onsite Energy Sources: Solar • How much energy can a solar array produce on an annual basis? • Let’s look at a 3.0kW array of photovoltaic cells: kWh/yr = 3.0kW*5.5 hr/day*365 days/yr*0.9 kWh/yr = 5,420 kWh/yr Inverter efficiency is 0.9 Assumes no shading from adjacent buildings and/or trees

28. Onsite Energy Sources: Solar • Average Residential Usage • 8,000 – 11,000 kWhr/yr per home • Area Required • Roughly 10 W/ft2 • So the 3.0 kW array will take up 300 ft2 • The average home would need an array approximately: 398 to 548 ft2 • So space and storage become significant issues…

29. Onsite Energy Sources: Solar • Solar energy can be utilized as a passive agent • Houses designed to heat in the winter without attracting unwanted sun the summer • Overhangs and shading positioned to use or shield the strength and angle of the sun’s rays • Solar Declination  • Changing seasons, change the angle between us and the sun • In the northern hemisphere the sun is always angled just south of the sky’s middle • Solar energy applications, including passive solar, should be positioned on the southerly side

30. Onsite Energy Sources: Solar • The solar chimney • Uses a tall structure on the south end of a building with a glass window • The chimney is vented to the outside at the top and is vented to the building at the bottom • Forced convection cycle pulls moist air out of the building space providing ventilation •  Solar Grain Drying • Air is drawn into a flat solar collector on the downstream end • Then is forced by a fan or thermal buoyancy to convect through the grain bin • Heated solar air will extract moisture

31. Onsite Energy Sources: Solar

32. Onsite Energy Sources: Wind • Wind power extracts energy from moving air by use of turbine to rotate the spindle of a generator • Similar to the way a car alternator charges your car battery while the engine is running • Wind speed varies greatly by height • Larger blades create more area and carry more inertia spinning longer • Height of turbine should be roughly 2 to 3 times the blade length

33. Onsite Energy Sources: Wind

34. Onsite Energy Sources: Wind • Types of tubines • Horizontal Axis • Vertical Axis

35. Wind Speed Calculations • Wind profile power law: 1/7th power law • Wind speed rises with the 7th root of altitude u/ur = (z/zr)a • a is 1/7, u is the speed at hieght z, and the subscript r refers to the reference height and speed (something known) • These values change depending the atmospheric conditions and turbine style

36. Wind Power Calculations P = power, Watts E = Efficiency, the theoretical maximum is 0.59 C = 4.17 x 10-5 (5.02 x 10-3) A = area, square meters (square feet) v = average wind speed meters per second (miles per hour) Power= E *C *A* v3

37. Wind Power Calculations

38. Onsite Energy Sources: Wind • Notice that the average wind speed is cubed in the formula • wind speed at 3 miles per hour is 27 times the constants… • and wind speed at 10 miles per hour is 1,000 times the constants! • This is Florida’s problem: low average wind speeds, interspersed with hurricanes

39. Onsite Energy Sources: Geothermal • High temperatures occur in many locations around geologically active areas • Temperature gradients underground can be used to create small differential temperatures causing expansion and contraction of air and water • Can be used to generate hot water or steam • Directly heating • Generate electricity with steam turbines

40. Onsite Energy Sources: Geothermal • Used in passive homes to heat or cool through ground tubes • buried tubes can be used to cool air that is then drawn through a ventilated building • viable in drier climates, and not applicable to the hot, humid south  • Geothermal energy is a viable resource in passive design outside the hot, humid southeast

41. Onsite Energy Sources: Geothermal

42. Onsite Energy Sources: Biomass • Agricultural products can be burned to produce heat • The most familiar method of doing this is to burn wood in a stove or furnace • Biomass refers to plant material that can be burned for energy • Energy can also be generated by burning methane generated from agricultural products or wastes

43. Onsite Energy Sources: Biomass • Biomass can be directly burned or fermented in digesters • Anaerobic • Aerobic • Anaerobic microbes turn the hydrocarbons in organic matter into methane • Methane can be burned just like natural gas • Methane generation can produce useful energy, but requires a large amount of skilled attention to function properly • Aerobic microbes turn hydrocarbons into soil nutrients and produce some CO2

44. Onsite Energy Sources: Biomass • Alcohol can be produced by fermenting agricultural products or waste • Alcohol sees some use in the United States as an additive to gasoline • Use widely as a fuel in other countries, like Brazil • Can be used as a replacement for gasoline, but is not more energy efficient than gasoline • This is because alcohol must be distilled in order to produce a fuel that will burn in internal combustion engine • Substitutes for diesel fuel can also be extracted from soybean oil, sugarcane, and mixtures of burned vegetable oil

45. Onsite Energy Sources: Hydrogen • Hydrogen is another alternative to gasoline • Using hydrogen is not a way of saving energy, but rather of reducing objectionable emissions • Hydrogen is the cleanest burning fuel • When burned with pure oxygen, the only combustion product is water • Hydrogen fueled vehicles will probably become more important • The main problem with hydrogen is distribution and storage • Liquid hydrogen is difficult to store • Heavy and bulky fuel tanks are necessary for hydrogen fueled vehicles

46. Onsite Energy Sources • Individual power supplies (those designed for house scale operations) are never constant • The sun is not out all the time • Wind does pass fast enough all the time • There is not a constants stream of feedstock for a digester • Etc… • So energy must be stored

47. Onsite Energy Sources: Storage • Most onsite applications produce DC power • Solar panels • Turbines (wind, water, solar) • Easily stored in batteries, but must pass through an inverter to make the DC power 3 phase AC power • The inverter is not 100% efficient so you lose some power output • If a small scale generator is used for a turbine then to store the energy you must: • Use a converter to make the power DC for battery storage • Then use an inverter to make the battery energy 3 phase AC power again

48. Energy Strategy • With the current accessibility to the public grid a good cost benefit analysis would need to be performed in order to determine the benefits of locally produced power • The first place to start is with increased efficiency • Passive design techniques • Proper wiring and electrical layout • Energy efficient products, proper usage and timing

49. Energy Efficiency • Building orientation to the solar pattern • Overhangs where appropriate • Surrounding foliage • Trees for shading • Plants used to funnel air as a wind channel and barrier • Glazed glass • Properly ventilated structures

50. Energy Efficiency • For Air Conditioned buildings: HVAC duct sizing and placement • Sized for the application • Well insulated, and not crimped • Air handlers inside conditioned space • Insulating materials • High R-values • No moisture barriers in FL