“Solar” means ‘from the Sun’. Even before the advent of modern civilization man has been depending on the Sun for warmth and light. Sun was and is worshipped by many of the old world religions and was a main god in all of the ancient civilizations. Sun light makes life on earth possible. Solar energy starts the food chain in plants by helping in photosynthesis. Solar energy provides light and the warmth during day. Simply put life on earth revolves around when the Sun rises or sets. Before the advent of electrical bulbs The Sun was the primary source of light during the day. With the advent of electricity and more efficient interior lighting the dependency on Solar light reduced and as a result architecture evolved to not-being constrained by availability of day-light. This change also led to the present day scenario where the single most power consumed in a commercial building is for lighting.
Solar energy is clean and available in abundance. The amount of Solar energy that falls on the earth’s surface a day is enough to light every home and office forever. Around 2 billion people worldwide have little or no access to power.
From 2006 to 2007 there has been an 85% increase in Solar energy production using PV cells. More wide spread usage of Solar energy would come about sooner once the PV cells become more affordable. Researchers are working to make Solar energy more affordable. As of now the reality is that without Government subsidies Solar energy is still not economically viable.
U S department of Energy has a Solar America Initiative which is aiming to make Solar energy compatible price wise with conventional forms of energy by 2015.
The various methods of harnessing solar energy from the Sun in use today are listed below:
i.PHOTOVOLTAIC ENERGY – This method is the one most commonly seen method of Solar energy generation. Photovoltaic’s are broadly classified into 2 – (Crystalline) PV Cells and Thin Film Solar .
PV cells: Photovoltaic Cells literally means producing “Voltaic” – Energy from “Photo” – Light. PV cells are of 2 kinds mono-crystalline and polycrystalline – based on the kind of silicon used; Mono-crystalline – from single crystals, which is more efficient but expensive to produce and Poly-crystalline – which is cut from ingots there by reducing cost of production and also efficiency. Poly-crystalline PV cells are the most commonly used Solar energy generators.
Photovoltaic cells are considered the first wave in Solar Energy development. These cells have been used in Solar calculators and watches for decades. 9 out of 10 Solar energy generators are PV cell based. PV cell systems are used from simple Solar garden lamps and Solar sign lights (Provide hyper link to Solar Sign Light here) to running communication systems, traffic signals, water pumps etc which are off grid… PV cells are also used in powering satellites. The solar panels on satellites are turned away from the Sun so as to prevent excessive energy buildup. Japan is planning to set up satellite Solar energy stations in space and beam down energy!
Photovoltaic cells on Solar panels consist mainly of a silicon wafer based semiconductor which is treated to create a negative and a positive side. When Sunlight hits the PV cell photons cause electrons to be released. The negative and positive ends connected to conductors aid in the flow of electrons i.e. electricity thus converting Solar energy (light energy) into usable electrical energy.
PV cell arrays are simple to install and easy to connect together to create any size Solar panel. PV cell Solar energy panels are emission free and don’t require cooling as the conversion of light energy to electrical energy is direct without a need for generators. Use of PV cell Solar energy generators was more in places which were off the grid.
Future plans call for installations of Solar Energy generators using PV cells to be linked to the grid with an added inverter to enhance and aid the distribution system of the standard power grid.
Germany is the leading user of Solar energy using PV cells, closely followed by Japan and the United States.
THIN FILM TECHNOLOGY – Thin film Solar is considered the second stage in Solar Energy systems power Generation. Thin film basically means application of an extremely thin layer of photovoltaic substance to a substrate. RCA developed the first thin film solar in 1976 by applying a very thin layer of amorphous silicon to a glass substrate, the process used then was too expensive even compared to
the PV cells making it economically non-viable. The usage of a thinner layer of silicon (up to 100 times thinner) leads to the reduction in price by almost 50%. The development of scribing (similar to printing ink being applied) made thin film economically viable. Thin film Solar panels are used extensively in satellites.
Thin film technologies are basically divided based on the photovoltaic substance used: CdTe (Cadmium Telluride), CIGS (Copper Indium Gallium Selenide), CIS (Copper Indium Selenide), some dye-sensitized cells and organic solar cells are also being experimented with.
- CdTe Technology
CadmiumTeluride based solar film panels are thinner and cheaper than silicon based PV cells. They were the first to break the 15% efficiency barrier in Solar cells. First Solar is the lead manufacturer and researcher in the field of thin film solar. The cadmium used in production of these thin film semiconductors is the waste recycled from smelting of Zinc, and is considered the most environmentally safe way of using cadmium. The manufacturers say they use the most care to keep cadmium oxides from being released into air and water. They also set it up so that at the end of the expected life of these thin film solar panels they are collected, refined and recycled to create other modules or products. There by reducing Cadmium ending up in waste dumps. On the flip side these cells are only 10% effective, therefore what one save on the pricing of a cell, one might end up spending to get more cells to reach the same power generation as silicon based PV cells. CdTe Solar cells are made using a glass substrate as base. The chief manufacturers of CdTe Solar PV cells are First Solar
- CIGS technology
CIGS is part of the third wave of Solar Power technology development; this again is another thin film technology and uses CIGS which is a compound of Copper, Indium, Gallium and Selenium (Cu (InGa) Se2-CopperIndiumGalliumDiselenide). These elements when combined in the proper ratios form a semiconductor that can be applied as a thin film to create photovoltaic cells on many carrier substrates which also make them flexible. The CIGS layer absorbs photons, the first step in the transformation of Solar energy to electricity.
The advantages of Solar Power production using CIGS over CdTe is as follows:
- Per Watt less expensive than CdTe.
- Better efficiency in low light and low angle conditions.
- Extremely light weight as it can be mounted on any substrate.
- Flexible enough that it can be molded to fit small curves.
Various companies are coming up with ways to make thin film Solar energy more efficient, cheaper and also portable and flexible. Various substrates such as Steel, fabric, polymers and plastic are being used.
Solar Energy instead of the non-renewable yet cheaper standard grid for homes and Offices may still take time to make economic sense to a majority, but with the advancing technology it might be sooner rather than later when the world starts relying on renewable energy sources more.
Chief manufacturers of PV Cells or thin film Solar in the world are:
SunPower – Manufactures the highest efficiency Solar energy systems technology worldwide. www.sunpower.com (USA)
Conergy AG – One of the world’s largest solar companies and offers a broad product range from solar driven water pumps to photovoltaic and solar thermal systems, for off-grid and grid-connected Solar energy systems installations. www.conergy.com (Germany)
BP Solar – Mostly PV cells and has claimed the highest efficiency panels in the commercial market at 20%. BP solar manufactures stand alone and on the grid Solar energy systems for homes, offices and factories which can be added or put in during construction. www.bpsolar.com
Uni-Solar Ovonic – Manufactures thin film solar panels with a steel substrate, most efficient thin film modules in the world as per their website. These Solar energy systems can also be Building integrated, stand alone or linked to a grid. Manufacturing capacity of 28 megawatts, factory in Michigan. (USA) www.uni-solar.com
Suntech – Power- Mostly PV cell Solar energy systems. Also manufactures MSK design line a building integrated photovoltaic modules which can be combined or used as an add on as part of a buildings skin, the exception being that it would be generating electricity from Solar energy!! (China)www.suntech-power.com
Isofoton – Manufactures Photovoltaic and Thermal Solar energy systems. www.isofoton.com (Spain)
Kyocera – Manufacturer of crystalline PV cell Solar energy systems of up to 16% efficiency. http://kyocerasolar.com (Japan)
Siemens Solar – Manufacturer of Solar Power plants and modules. http://www.siemens.nl/sunit_en/Default.asp?p=1 (Germany)
Q-cells – They are the leading manufacturers of Solar power in 2006. Develop, Manufacture and sell high performance crystalline PV cell
Solar energy systems. www.q-cells.com (Germany)
First Solar- CdTe based thin film Solar energy systems manufacturers. First Solar PV Modules are designed for use in grid-connected, commercial power plants and are sold to leading system integrators, independent power project developers, and utility companies worldwide. www.firstsolar.com (USA)
Nano Solar – Is fast emerging as a leader in thin film Solar energy systems and is sold out until 2009, the company claims it will be able to sell Solar panels for 1 $ per watt! This ultimately was a goal which always seemed too far away. www.nanosolar.com (USA)
Powerfilm Inc – Flexible Thin film Solar energy systems manufacturer based in Iowa. www.powerfilmsolar.com (USA)
Yingli Green Energy – They are one the leading vertically integrated Solar PV manufacturers in China (meaning from silicon crystals to Solar panels). www.yinglisolar.com (China)
Sharp – Has been one of the leading manufacturers of Solar energy PV cell systems in the world for the last 3 years. http://sharp-world.com/solar/ (Japan)
Sanyo – Manufacturers of PV Solar modules and Amorphous Silicon thin film modules. http://us.sanyo.com/solar/ (Japan)
Siliken – One of the newer manufacturers of Solar PV modules. www.siliken.es (Spain)
Flisom AG – They manufacture thin film solar. http://www.flisom.ch/e/index.html (Switzerland)
Konarka technologies – They focus mainly on portable Solar energy systems based on thin film solar power generation. The thin-film solar panels Konarka manufactures are called Power Plastics. http://www.konarka.com/index.php (USA)
ii.Concentrating Solar Power systems / Solar Thermal Power – This is Solar energy harnessing using lenses and parabolic mirrors to concentrate Sun’s heat. The largest concentrating Solar energy plant is a demonstration power plant near Barstow California. Concentrating Solar systems are of 3 kinds mainly:
- Parabolic trough systems where parabolic mirrors are used to concentrate Solar energy onto the focal point, where a thermal receiver with fuel inside gets heated. Solar thermal systems in California produce enough energy to meet the needs of 350,000 people.
- Dish/Engine concentrating systems use dish shaped mirrors and are focused on to a receiver which is on a tower.
- Central receiving systems are made of thousands of individual Heliostats (Sun-tracking mirrors) which concentrate solar energy on to even taller towers. Heat is transferred using heat transfer liquids which help produce steam to run a generator and produce electricity.