Solar Power and Glenforest
Efficiency, Environmental Impact, and Our School (George J)
Solar Energy: Introduction and how it works
When we think about renewable, natural energy sources, the sun is one of the first things that come to mind. Seen on anything from calculators to spacecrafts, we now have the technology to harness a fraction of that energy in the form of solar power; in fact, solar power now accounts for a tenth of the world's energy consumption. These solar panels, containing photovoltaic cells, are made up of semiconductors, usually silicon. When sunlight hits these cells, electrons are knocked loose from the atoms, and as they flow through the cells, they generate electricity.
As the example in the diagram shows, the semiconductor in the middle is treated to create an electric field, and to have one positive and one positive side. When they are both attached to circuit, electrons displaced from the sunlight will create a current, and thus electricity.
On a larger scale, sunlight is sometimes used directly for the heat energy it gives off, which is used to boil water to drive a steam turbine, instead of water, coal, etc in other energy sources.
Solar Energy: Effeciency and Downsides
When evaluating energy sources, one of the most important things to consider is efficiency. Efficiency is defined as the percentage of energy that can be extracted as a percentage of the amount of actual energy used up to extract that useful energy (which will vary in quantity and type for different energy sources). Therefore, you can see how important efficiency is in regards to energy production; if using the same amount of energy will yield more electricity for one type of electricity generation than another, then it wouldn't make sense to use the latter. Of course, efficiency isn't the only factor to consider, with renewablity, access to the resource, and effect on the environment on the list.
(Note: This graph is slightly outdated, and optimized photovoltaic technology today can go up to as high as 40% efficiency)
You can see from this graph that compared to other sources, in terms of efficiency alone, solar photovoltaic energy ranks pretty low compared to other energy sources. This can considered one of the biggest weaknesses of solar energy. And it's a shame too, because every hour, the sunlight hitting the earth carry enough pure energy to provide for our planet's energy needs for an entire year. Obviously, because not every square inch of the earth is covered with solar panels, and due to the low efficiency to photovoltaic cells to convert this energy to useful, electric energy, we will never come close to harnessing all that energy with the solar technology we possess right now.
There are also other downsides to solar power. Since it's largely dependent on nature, it can be unpredictable. For example, solar power is obviously scarce at night and during cloudy or rainy days. A storage device or battery would also be required for solar energy to be stored to be used at night. Solar energy is also one of the most costly energy sources, even though there are little to no costs after the panel is installed. A solar panel for an average sized house, 3.5-4kWp (kilowatt-peak, a standard unit to measure the current and voltage produced at varying resistances at light intensity 1000W/m^2 for photovoltaic appliances), have costs around 7000 - 13000 Canadian dollars. Also, due to solar panels' low efficiency, a large surface area would have to available for solar power to really be effective.
Solar Energy: Environmental Impact and Benefits
One of the main benefits of solar energy is that it is arguably one of the most environmentally friendly methods of energy production, even compared to other non-pollution renewable sources. While building a dam for hydroelectric power heavily displaces the surrounding environment, solar panels are passive, and built in places such as rooftops that have minimal effect on surroundings. It is also very versatile, and can be produced anywhere on earth where the sun shines. It is also estimated that the size of a typical home voltovoltaic system can save over a tonne of carbon dioxide being produced per year.
Efficient Energy for Our School
Implementing solar panels into the school may seem farfetched, but in this day and age, even institutions are finding the need to try renewable energy sources, not only for environmental reasons, but to cut costs as well. And it's not undone either; in September 2011, three high schools in West Sonoma County Union implemented a huge solar energy project that led to huge success, and I believe that Glenforest Secondary School has more than enough capacity to follow its example.
As the diagrams show, this huge system is not only built on rooftops, but also ground mounts and shade structures.
In total, the schools installed 2608 panels, covering 45800 square feet. The entire system is a huge 834kW system, which will satisfy three-fourth of the schools' energy needs, at the same time saving them $297,500 in the first year, power equivalent to powering 300 homes for a year. During the entire lifetime of the system (25 years), it will save $9 million dollars in energy production, as well as prevent 8000 tonnes of carbon dioxide emissions from non-renewable energy sources.
Of course, there are other specifics that should be considered to maximize efficiency. Luckily, factors such as shade needn't be considered, since the school, parking lot, and field are completely shadeless (with the exception of clouds, which is inevitable). There are also no construction sites nearby which may create dust clouds. The angle orientation of the panels are also extremely important to maximize efficiency, which will depend on the school's latitude. Optimal angles for solar panels are perpendicular to the sun's rays at solar noon (when the sun is highest during the day), and pointing at solar south. A solar panel with a non-optimal tilt can result in over 25% less power than optimal. The panels would also need to be adjusted every season, with winter being about 15 degrees more than the latitude angle constant, and summer 15 degrees less.
The chart below also shows multiple different photovoltaic cells that have been invented up until our current year, and how they rank in terms of efficiency for our school to potentially chose from.