Energy and power, solar astronomy. (Lecture 4) презентация

IE350 Alternate Energy Course Lecture # 4 Energy and Power, Solar Astronomy

Energy Units - Calorie Calorie (cal) = heat to increase by 1°C the 1 gram of water. 1 cal ≈ 4.184 Joules

Very Small Energy Unit, eV Electronvolt (eV) - the amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuum.

Energy unit conversion factors

Energy and Power If power is constant E = P · t, P = E/t If power is variable and depends on time E = ∫P(t)dt, P(t) = dE(t)/dt

Power Units Watt (W) = using one J in one second. kW = 1000 W Horsepower = 735 W = 0.735 kW MW = 1000 kW

Power vs. Energy Thus, power is the rate of the energy use. Energy is what you pay for repeatedly, as much as you use the energy, the kWh-s – variable, operational cost. Power is the capacity to use the energy You pay for the capacity usually upfront, fixed or installation cost. E.g. if you decide to buy an air conditioner, you need to solve a power sizing problem. You pay the fixed amount. Later you usually use only a fraction of the total capacity.

Solar Energy The SUN: Fusion in the sun – the process Temperature of the suncrust, black-body radiation – BBR Photon energy, light speed, duality Electromagnetic Spectrum The solar radiation spectrum Solar constant = 1366 W/m2.

The light: particle, wave Particle and wave Light speed, c = 299,792,458 m/s c ≈ 300,000 km/s Photon energy, E = h= frequency, h is Planck’s constant, h = 6.626 10-34 J s h = 4.135 10-15 eV s.  = c/ E = hc/

Electromagnetic Spectrum

Sun Spectrum

The Sun Sun has a capacity of 3.86×1026 W 3.86×108 EJ/s Earth gets only two-billionth part of it. 127,400,000 km² - Earth cross-section 1.740 1017 W = 0.174 EJ/s Armenian annual energy consumption: 0.1752 Quads Solar Constant =1366 W/sq.m. Average Insolation = ¼ of solar const. = 342 W/sq.m.

How this energy is generated?

How this energy is generated? About 74% of the Sun's mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements.

How this energy is generated? The Sun has a surface temperature of approximately 5,500 K, giving it a white color, which, because of atmospheric scattering, appears yellow.

How this energy is generated? The Sun diameter: 1.4 106 km = 109 that of the earth. Distance from Earth: 1.5 108 km, = 8.31 min at light speed

How this energy is generated? It was Albert Einstein who provided the essential clue to the source of the Sun's energy output with his mass-energy relation: E=mc²

The Sun

NASA caption: Giant magnetic loops dance on the sun’s horizon in concert with the eruption of a solar flare—seen as a bright flash of light—in this imagery from NASA’s Solar Dynamics Observatory, captured Jan. 12-13, 2015. Image Credit: NASA/SDO

Sun surface videos https://www.youtube.com/watch?v=ipvfwPqh3V4 https://www.youtube.com/watch?v=0WW1HN0iG0M https://www.youtube.com/watch?v=lpzCSZ7Eerc https://www.youtube.com/watch?v=nmDZhQAIeXM

Solar wind The total number of particles carried away from the Sun by the solar wind is about 1.3×1036 per second. Thus, the total mass loss is about 4–6 billion tons per hour. Composed of: - electrons, - protons - alpha particles

Elementary particles flow from Sun – Solar Wind http://www.independent.co.uk/travel/europe/watch-this-beautiful-timelapse-of-the-northern-lights-over-norway-9735690.html http://www.bbc.com/news/science-environment-28690559 https://www.youtube.com/watch?v=sBWPCvdv8Bk

Solar Wind

Aurora Borealis https://www.youtube.com/watch?v=hsMW7zbzsUs https://www.youtube.com/watch?v=Vdb9IndsSXk https://www.youtube.com/watch?v=pjgvGiEHlNs

How this energy is generated? In 1920 Sir Arthur Eddington proposed that the pressures and temperatures at the core of the Sun could produce a nuclear fusion reaction that merged hydrogen into helium, resulting in a production of energy from the net change in mass.

This actually corresponds to a surprisingly low rate of energy production in the Sun's core—about 0.3 µW/cm³ (microwatts per cubic cm), or about 6 µW/kg of matter. This actually corresponds to a surprisingly low rate of energy production in the Sun's core—about 0.3 µW/cm³ (microwatts per cubic cm), or about 6 µW/kg of matter. For comparison, the human body produces heat at approximately the rate 1.2 W/kg, roughly a million times greater per unit mass.

How this energy is generated?

1.5 The future of energy resources Solar Constant = 1366 W/sq.m. Sahara’s surface area = 9,000,000 sq.km. If we use 10% of Sahara with 12.5% efficiency, we will get 1000 Exajoules/year! This is twice as much as current world consumption. I can see the future «Ocean Solar Power Plants», that produce Hydrogen! However, population grows exponentially!

Earth's rotation Earth's rotation tilts about 23.5 degrees on its pole-to-pole axis, relative to the plane of Earth's solar system orbit around our sun. As the Earth orbits the sun, this creates the 47-degree peak solar altitude angle difference, and the hemisphere-specific difference between summer and winter.

Solar Constant

Now: go to the article http://www.wired.com/2015/07/pluto-new-horizons-2/

Solar radiation bouncing atmosphere the theoretical daily-average insolation at the top of the atmosphere, where θ is the polar angle of the Earth's orbit, and θ = 0 at the vernal equinox, and θ = 90° at the summer solstice; φ is the latitude of the Earth. The calculation assumed conditions appropriate for 2000 A.D.: a solar constant of S0 = 1367 W m−2, obliquity of ε = 23.4398°, longitude of perihelion of ϖ = 282.895°, eccentricity e = 0.016704. Contour labels (green) are in units of W m−2

Airmass In astronomy, airmass is the optical path length through Earth's atmosphere for light from a celestial source. As it passes through the atmosphere, light is attenuated by scattering and absorption; the more atmosphere through which it passes, the greater the attenuation. Consequently, celestial bodies at the horizon appear less bright than when at the zenith.

Earth Atmosphere

Rayleigh scattering

Airmass “Airmass” normally indicates relative airmass, the path length relative to that at the zenith at sea level, so by definition, the sea-level airmass when the sun is at the zenith is 1. Airmass increases as the angle between the source and the zenith increases, reaching a value of approximately 38 at the horizon. Airmass can be less than one at an elevation greater than sea level.

Airmass Atmosphere height = 8.5 ÷ 11 km. Earth's mean radius is 6371 km. Airmass abbreviation: AM##. E.g. at angle of approximately 60 degrees over horizon we have AM2, = 62% of solar constant. The solar panels are often rated at AM1.5 The maximum airmass at horizon is: AM35.5 ÷ AM39 At sea level, AM1 attenuates @ 27%. At AM10 we have 23X attenuation At AM20 we have >10000X attenuation

Earth Atmosphere

Numbers to remember Solar constant = 1366W/m2 Attenuation at AM1 = 27% Scattered light capacity = 1366W/m2 x 27% = 369W/m2 Intensity at AM1 = 1366W/m2 - 369W/m2 = 997W/m2 ≈ 1000W/m2 Reference Intensity = 1000W/m2

Air mass calculations

Notion of the Cost per peak watt installed “Peak Watt” = 1000W = 1kW Is the power produced at normal incidence of solar radiation @ 1000W/m2. $/Wp - Easy way to compare various solar conversion devices. Mostly useful for electric power generation devices, such as for: Hydro; PV; Wind, Solar Thermal Electric, etc.