cons

everyone knows that solar cells are great for the environment, but can we afford it?

At a current cost of 25 to 50 cents per kilowatt-hour, solar power costs as much as five times more than conventional fossil fuel-based electricity. And dwindling supplies of polysilicon, the element found in traditional photovoltaic cells, are not helping.

The Politics of Solar Power

According to Gary Gerber of the Berkeley, California-based Sun Light & Power, not long after Ronald Reagan moved into the White House in 1980 and removed the solar collectors from the roof that Jimmy Carter had installed, tax credits for solar development disappeared and the industry plunged “over a cliff.” Federal spending on solar energy picked up under the Clinton administration, but trailed off again once George W. Bush took office. But growing climate change worries and high oil prices have forced the Bush administration to reconsider its stance on alternatives like solar, and the White House has proposed $148 million for solar energy development in 2007, up almost 80 percent from what it invested in 2006.

Increasing the Efficiency and Lowering the Cost of Solar Power

In the realm of research and development, enterprising engineers are working hard to get solar power’s costs down, and expect it to be price-competitive with fossil fuels within 20 years. One technological innovator is California-based Nanosolar, which replaces the silicon used to absorb sunlight and convert it into electricity with a thin film of copper, indium, gallium and selenium (CIGS). Nanosolar’s Martin Roscheisen says CIGS-based cells are flexible and more durable, making them easier to install in a wide range of applications. Roscheisen expects he will be able to build a 400-megawatt electricity plant for about a tenth of the price of a comparable silicon-based plant. Other companies making waves with CIGS-based solar cells include New York’s DayStar Technologies and California’s Miasolé. Another recent innovation in solar power is the co-called “spray-on” cell, such as those made by Massachusetts’ Konarka. Like paint, the composite can be sprayed on to other materials, where it can harness the sun’s infrared rays to power cell phones and other portable or wireless devices. Some analysts think spray-on cells could become five times more efficient than the current photovoltaic standard.

Venture Capitalists Investing in Solar Power

Environmentalists and mechanical engineers aren’t the only ones bullish on solar these days. According to the Cleantech Venture Network, a forum of investors interested in clean renewable energy, venture capitalists poured some $100 million into solar start-ups of all sizes in 2006 alone, and expect to commit even more money in 2007. Given the venture capital community’s interest in relatively short-term returns, it’s a good bet that some of today’s promising solar start-ups will be tomorrow’s energy behemoths.

bibliography:

Solar Power: The Pros and Cons of Solar Power, 2008, Larry West, 10 July 2008, link: http://environment.about.com/od/renewableenergy/a/solar_power.htm

Life Span

A solar cell must be capable of producing electricity for at least twenty years, without a significant decrease in efficiency.

­­You've probably seen calculators that have solar cells -- calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels -- on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot if you know where to look. There are solar cell arrays on satellites, where they are used to power the electrical systems.

Yo­u have probably also been hearing about the "solar revolution" for the last 20 years -- the idea that one day we will all use free electricity from the sun. This is a seductive promise: On a bright, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that energy we could easily power our homes and offices for free.

Quek Ying

Application and implementation

Solar cells are often electrically connected as a module. PV modules often have a sheet of glass on the front side (sunny side up) , allowing light to pass while protecting the semiconductor wafer from the elements (rain, hail, etc.).

Solar cells are also usually connected in series in modules to create an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and current.

The power output of a solar array is measured in watts or kilowatts. A measurement in watt-hours, kilowatt-hours or kilowatt-hours per day is often used. Each peak kilowatt of solar array output power corresponds to energy production of 4.8 kWh per day.

The electricity of solar generated energy is most often fed into the electricity grid using inverters (grid-connected PV systems); in stand alone systems, batteries are used to store the energy that is not needed yet.

Li Qi

Minutes

Meeting#1

Name of Project: physics SIA Purpose of Meeting: to delegate tasks Date/Time: 20 May 2008 Members: Chew Li Qi Janice Yeo Quek Ying Chen Qin Yan
Topic	Discussion	Action	Person Responsible
1. doing the poster	the focus of the poster would be on the environmental benefits of using solar cells. it would include a short introduction on solar energy.	Qin Yan and Li Qi have already researched and done up the poster	Janice
2. doing the blog	the blog would be about our researched information. meeting minutes would be put up occasionally to show progress of project.	Janice has already started the blog and Quek Ying has researched on information.	Janice
3. who would be doing the powerpoint	the powerpoint would show the whole process of our project; from the blog to our reflections.	Janice would do the first draft of it and Li Qi will edit. after the powerpoint is done, Qin Yan and Quek Ying will work on the script also to be edited by Janice and Li Qi.	Quek Ying

Minute taker: Janice

P-N Junction

The most commonly known solar cell is configured as a large-area p-n junction made from silicon. In practice, p-n junctions of silicon solar cells are made by diffusing an n-type dopant into one side of a p-type wafer (or vice versa).Such an array is called a solar module. Solar cells are used to supply power to, Space
Applications, Rural Telephone Exchanges, Street Lighting, Mountain terrain mission control,
Remotely operated Robots, etc.,

bibliography:
http://www.wcubed.com/solar/What%20is%20a%20Solar%20Cell/light11.gif

(picture)

Qin Yan

How does a silicon solar cell work?

There is a direct conversion of light energy to electrical current in a solar cell.

When sunlight is present, light energy creates positive and negative charged particles which are then separated in the two layers of treated silicon in the solar cell, a structure to trap particles when it is in darkness. In other words, when the sunlight hits the cell, the particles move apart from one another.

This movement creates a voltage that generates an electrical current when the cell is part of a complete circuit. Current will then flow if the separate charged ends of the cells with a conductive material is connected.(as shown in the diagram)

Bibliography

1. Interactive Learning Centre. (1997). Some semiconductor physics. [On-Line]. Available: http://www.soton.ac.uk/~solar/intro/tech2.htm (June 1, 2008)

2. (1998). How is solar power generated. Illustrated Encyclopedia of Science and Nature, Energy and Physics. Time Life Asia.

Li Qi

what is a solar cell?

like every good presentation we start with an introduction. what is solar energy which is the main cause for solar cells which brings about this student-initiated assignment?

solar energy:

• energy produced directly by the sun
• indirect source of all energies except geothermal energy, nuclear fissions and fusion
  

the sun creates its energy through a thermonuclear process that converts about 650,000,000 tons of hydrogen to helium every second. The process creates heat and electromagnetic radiation. The heat remains in the sun and is vital in maintaining the thermonuclear reaction. The electromagnetic radiation (including visible light, infra-red light, and ultra-violet radiation) streams out into space in all directions.

bibliography:

An Introduction to Solar Energy, 1988, eric w. brown, 3 June 2008, http://www.ccs.neu.edu/home/feneric/solar.html

quek ying