For a complete curriculum primer that explains the content below on energy and solar energy in more detail, click:
Energy Sources and Forms
There are many ways to understand what form energy is in or various energy sources. Primary sources of energy in the universe include nuclear, gravity, radiation, chemical, and geothermal. Secondary forms of energy include mechanical, thermal, and electrical. Further energy can be classified into two categories: kinetic or potential.
Laws of Thermodynamics (Energy)
The first law of thermodynamics states that energy cannot be created or destroyed, although it can change from one form to the other. The second law of thermodynamics states that when energy is converted from one form to the other, some of it is degraded into heat, a less usable form that disperses into the environment
Entropy , a measure of disorder and randomness, is constantly increasing in the universe. That is to say the energy in the universe is always moving from a higher usable, low entropy form to a less usable, higher entropy form.
For one of the three examples explain how it illustrates entropy.
Efficiency
Because of the second law of thermodynamics, whenever energy changes form it is impossible for there to be a 100% conversion or 100% efficiency. Efficiency can be defined as the amount of work that comes out of a system divided by the amount of work out that comes out of the system.
Efficiency = Energy Out/Energy In
You just watched a system of energy change. List as many of the changing forms of energy in order over time of that system, including energy sources/forms allowed this system to occur. What might be the demonstrated efficiency? To answer this , what assumption would have to make about the work put into turning the handcrank and the amount of work done by the end hand crank?
System > Efficiency > Immediate Energy Forms
Automobile Engine > 20-30% > Chemical (fuel) to Mechanical (moving parts)
Automobile > 15% > Chemical (fuel) to Mechanical (movement of the car)
Human Cells for Metabolism > 40% > Chemical (food) to Mechanical
Commercial Solar PV cells > 15-18% > Radiation(sunlight) to Electrical (DC current)
Experimental Cells > 37% > Radiation(sunlight) to Electrical (DC current)
Fossil Fuel Steam PowerPlant > 33-40% > Chemical (fossil fuel) to Electrical
Lead Acid Battery > 70-92% (Discharge Efficiency) > Chemical to Electrical (DC)
Lithium Ion Polymer 99.8% > ( Discharge Efficiency) > Chemical to Electrical (DC)
The Sun
The largest primary and original source of energy for all life on earth and for all human activities is from the nuclear energy in the sun which reaches the earth as radiation energy. The sun is composed of hydrogen isotopes fusing together to form helium. In the process a small amount of matter is converted to energy, however, due to E=MC2 there is an enormous amount of energy given off by the sun (383 YottaWatts = 10exp24 watts) compared with humans average energy use (15.48 TeraWatts= 10 exp15 watts).
The Sun
Fusion
The sun gives off large amount of energy in the form of light radiation which travels to earth. Photovoltaic panels contain semi-conductor cells, typically made from silicon, that can absorb the photons from the sun converting light energy to electrical energy.
Solar Energy Technologies
There are numerous ways to capture energy from the sun. The major focus of this curriculum unit is on the photovoltaic cells. However, many systems use the suns heat to either provide heat for indoor spaces or for heating a coolant that in turn powers a generator that generates electricity. In addition to PV cells, these other solar energy systems include passive solar heating, active solar heating ,and solar thermal electric generation. The largest single solar energy system was a 500 MW Stirling engine system scheduled to become operational in the desert Southwest in 2009. This technology does not involved steam production, but rather sun light is concentrated by moving mirrors to heat a fluid which expands driving a piston that turns a shaft providing mechanical energy and electricity. Video:
Photovoltaic Panels
For a step by step interactive explanation for how a photovoltaic solar panel converts light energy (thus the “photo”) into electrical energy (thus the “voltaic”) for a house go to NOVA: Solar Panels and click on the “INTERACTIVES” icon on the right. The same principles apply to the Worcester Academy solar panels.
PV Cell Video:
WA PV Solar Panels
WA had a 92.19 kW DC PV system installed in April 2010. The systems is comprised of 439 invidual 210 watt PV panels made by Kyocera. 77 panels are on the each roof of Heydon and Stoddard with a combined DC capcity of 32.34 kW. Daniels Gym has 285 panels with a DC capacity of 59.85 kW. The Kyocera panels use silcon as the conducting material. The panels have a rated conversion efficiency of 16%.Click: Kyocera
The panels have an imbedded energy of 1.5 years of operation, meaning it will take 1.5 years of their producing energy to offset the amount of energy it took to construct the panels themselves. Think 2nd Law of Thermodynamics. Also, this duration may or may not include the energy used to install the panels.
Below is a short video of the ballasts used to hold down the panels on the dorm roofs being lifted up from ground level
The WA solar panels are expected to produce 100,948 kWh during the first year of operation. In 25 years that amount is expected to be 89,506 kWh.
Solar Across the Commonwealth and Nation
Solar energy makes up a small fraction of the total amount of renewable energy in the United States. However solar energy capacity is growing rapidly domestically and abroad.
The solar panels at WA and across the state have been made possible in part because of political capital. The state government has decided to set a goal of installing 250 MW of solar power within the state by 2017. Thus, there are state rebates for solar projects that when combined with federal government incentives make the projects financial feasible. In terms of concerns about “free market” forces it is important two remember two things. First, fossil fuels which provide over 80% of U.S. energy have been heavily subsidized over decades and that there is not yet an accurate market cost accounting for the externality of carbon pollution from fossil fuel sources. Statewide installed solar capacity, as measured through state rebated programs, was 3.05 MW as of March 2009. Total installations were higher in the residential area (282) than comerical (60), but total capacity for commercial was higher (1.9 MW) versus 1.1 MW for residential.
You are encouraged to explore your own solar installation potential at your home or business. The state funding program is in transition, click and save this link to the Renenwable Energy Trust (http://www.masstech.org/solar/) to access in the future as well as click: Commonwealth Solar which has details about the Commonwealth Solar II Rebate Program.
Other forms of Renewable Energy
Watch both videos below. On a piece of scratch paper list all the sources and forms of energy involved in creating electricity from hydropower dams and wind turbines.
